ICMCTF2013 Session BP: Syposium B Poster Session

Thursday, May 2, 2013 5:00 PM in Room Grand Hall

Thursday Afternoon

Time Period ThP Sessions | Topic B Sessions | Time Periods | Topics | ICMCTF2013 Schedule

BP1 High Temperature Wettability of Ion Implanted Multicomponent CrAlSiN by Molten Glass
Yin-Yu Chang, Hsing-Ming Lai (National Formosa University, Taiwan, Republic of China); Ho-Yi Kao (MingDao University, Taiwan, Republic of China)
Metal plasma ion implantation has being successfully developed for improving wear, corrosion, and physical properties of engineering materials. In this study, the multicomponent CrAlSiN coating was deposited on tungsten carbide substrates by using a cathodic-arc deposition system with lateral rotating arc cathodes. Mo, V and C ions were co-implanted into the multicomponent CrAlSiN film using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions was set at 40 kV with implantation doses of 1~2 x 1017 ions/cm2. The microstructure of the implanted coatings was investigated by a field emission gun high resolution transmission electron microscope (FEG-HRTEM, FEI Tecnai G2 20 S-Twin), equipped with an energy-dispersive x-ray analysis spectrometer (EDS), operated at 200 keV for high-resolution imaging. X-ray diffractometry was performed for phase identification using a PANalytical X’pert Pro diffractometer with a high resolution ψ goniometer and Cu radiation in both glancing angle and high-angle configurations. Mechanical properties, such as the hardness and elastic modulus, were measured by means of nanoindention. The wettability of the implanted CrAlSiN by molten glass at temperatures at 500°C in controlled air was measured by using an improved sessile drop method. The Mo, V and carbon ion implanted CrAlSiN had a lower oxidation rate and a higher contact angle than the CrAlSiN coated samples. Therefore, the kinetic oxidation behavior and wettability varied with the surface alloy composition and phase segregation via high temperature oxidation. Results of this study demonstrate the potential of metal plasma ion implantation in improving the wettability behavior of the CrAlSiN film by molten glass.
BP2 Mechanical Properties and Impact Resistance of Multilayered CrAlSiN/TiN Coatings
Yin-Yu Chang (National Formosa University, Taiwan, Republic of China); Yau-Yi Liou (MingDao University, Taiwan, Republic of China)
Transition metal nitrides, such as TiN and CrN, have been used as protective hard coatings due to their excellent tribological properties. In this study, TiN, CrAlSiN and multilayered CrAlSiN/TiN coatings were synthesized by cathodic-arc evaporation with plasma enhanced duct equipment. Titanium and CrAlSialloy cathodes were used for the deposition of CrAlSiN/TiN coatings. During the coating process of multilayered CrAlSiN/TiN, TiN was deposited as an interlayer to enhance better adhesion. The total cathode current of both Ti (I[Ti]) and CrAlSi (I[CrAlSi]) targets was controlled at 140 A. With different bias voltages and cathode current ratios (I[CrAlSi]/I[Ti]) of 0.75, 1.0, and 1.33, the deposited multilayered CrAlSiN/TiN coatings possessed different chemical contents and periodic thicknesses. The nanolayer thickness and alloy content of the deposited coating were correlated with the evaporation rate of cathode materials. The microstructure of the deposited coatings was investigated by a field emission gun high resolution transmission electron microscope (FEG-HRTEM, FEI Tecnai G2 20 S-Twin), equipped with an energy-dispersive x-ray analysis spectrometer (EDS), operated at 200 keV for high-resolution imaging. Glancing angle X-ray diffraction was used to characterize the microstructure and phase identification of the coatings. The composition and depth profile were evaluated by wavelength-dispersive x-ray spectroscopy (WDS). Mechanical properties, such as the hardness and elastic modulus, were measured by means of nanoindention. To evaluate the correlation between impact fracture resistance and hardness/elastic modulus ratio of the deposited coatings, an impact test was performed using a cyclic loading device with a tungsten carbide indenter as an impact probe. The design of multilayered CrAlSiN/TiN coatings is anticipated to inhibit the grain growth, and leads to grain refinement effect, which expected to increase the hardness and impact resistance of coatings.
BP3 Mechanical Properties and Physicochemical Characteristics of CrN/Si3N4 Multilayers
César Aguzzoli, T.P. Soares (Universidade de Caxias do Sul, Brazil); G.V. Soares (Universidade Federal do Rio Grande do Sul, Brazil); Carlos Figueroa (Universidade de Caxias do Sul, Brazil); Israel Baumvol (Universidade de Caxias do Sul, Brazil and Universidade Federal do Rio Grande do Sul, Brazil)

We investigated the mechanical and physicochemical properties of CrN/Si3N4 multilayered coatings in the period interval 2 to 10 nm, produced by depositing the thin film multilayer structure at substantially higher substrate temperatures than in previously reported works. This resulted in an appreciable increase in hardness at a multilayer period around 4 nm, as well a corresponding increase in the resistance to plastic deformation of the coating for multilayer periods around 4 to 6 nm. The various physicochemical characterization techniques used here revealed that the individual CrN and Si3N4 layers were stoichiometric and the interfaces were abrupt, while the Si3N4 layers were amorphous and the CrN ones crystalline. Furthermore, Si is mainly bonded to N as Si3N4 and maybe some other non-stoichiometric Si-N compound, whereas Cr was bonded as CrN and chromium oxides.

Keywords: Multilayers; Hardness; Si3N4/CrN

BP4 Reliability Characteristics of Multi-Step Deposition-Annealed HfO2 Film under Static and Dynamic Stress
Yi-Lung Cheng, Cheng-Yang Hsieh (National Chi-Nan University, Taiwan, Republic of China); TC Bo (National Chi Nan University, Taiwan, Republic of China)

The physical, electrical and reliability characteristics of the HfO2 gate stack fabricated by a single-step and a multiple-step deposition-annealing method are compared in this study. After the same high temperature (750oC) annealing, the single-step HfO2 has transformed into a polycrystalline phase, while the multi-step HfO2 is found to remain in a nanocrystalline phase, indicating that a multi-step deposition-annealing method could significantly improve the thermal stability of the high-k HfO2 film with respect to the grain formation process. Additionally, the density and composition of the high-k HfO2 film are enhanced by multi-step deposition-annealing process. These changes lead to an improvement in the electrical characteristics, breakdown voltage, and reliability of the multi-step HfO2 film. The reliability characteristics of multi-step deposition-annealed HfO2 dielectric under unipolar and bipolar AC stresses were also evaluated. Dielectric breakdown failure time of bipolar AC stress becomes longest in comparison to the other two stresses. Moreover, as the number of deposition-annealing steps increases, a larger lifetime enhancement is detected due to the effective charge de-trapping for multi-step deposition-annealed HfO2 dielectrics under bipolar stress.

BP5 Wear Properties and Microstructure Characterization of Various Fe-W-C-B-Cr System Clad Layers
Yu-Chi Lin, Yong-Chwang Chen (National Taiwan University, Taiwan, Republic of China)
Hard boride and carbide were both synthesized in situ as clad layers generated using the GTAW method. In this investigation, Fe, C and Cr-containing SKD61 and SKD11 substrates with tungsten boride (WB) powder were synthesized in situ in various phases in the clad layer. According to the results concerning hardness and microstructure, the Fe-W-C-B-Cr system clad layers had a high hardness, caused by precipitation hardening by various precipitates. Additionally, high C and Cr contents (WB-SKD11 specimen) lead to a clad layer with a hard and complex structure. The Fe-W-C-B-Cr system clad layers are quite thick, with a mean thickness of 6 mm. In the scanning electron image, the soft region of the heat-affected zone (HAZ) of the WB-SKD11 specimen had a bainite and retained austenite structure, owing to the high C and Cr contents in the substrate. However, the WB-SKD61 specimen had no soft region; its HAZ displayed the martensite structure. The hardness of the WB-SKD61 specimen gradually decreased as the distance from the clad surface increased. Cryogenic treatment of the WB-SKD11 specimen reduced some of the retained austenite structures and significantly improved the hardness values of the HAZ. During sliding, the hard vein-shaped phase in the WB-SKD11 clad layer provided strong mechanical interlocking. Therefore, the wear performance of the WB-SKD11 clad layer was substantially better than that of the other specimens under all test conditions.
BP6 Effect of Cu Diffusion on Electrical and Reliability Characteristics for Low Dielectric Constant Dielectric
Yu-Min Chang (National Chiao Tung University, Taiwan, Republic of China); Yi-Lung Cheng, Kai-Chieh Kao (National Chi-Nan University, Taiwan, Republic of China); Jihperng Leu (National Chiao Tung University, Taiwan, Republic of China); TC Bo (National Chi-Nan University, Taiwan, Republic of China)
The interaction between copper interconnect and dense or porous low dielectric constant films under thermal annealing was investigated in this study. The electrical and reliability characteristics were investigated using Cu/Low-k film/Si metal insulator metal capacitors. The experimental results showed that copper diffusion depth increased with the annealing temperature and annealing time in both low-k films. Moreover, the copper diffusion rate in the porous low-k films is faster and is dominated by the annealing temperature, so that a large increase in the dielectric constant was observed. The lifetimes of porous low-k films are shorter than those of dense low-k films by about two orders when stressed under the same electric field (4.7 MV/cm). Furthermore, we found that the leakage current increase and the low-k dielectric breakdown lifeti me are proportional to the copper diffusion depth for dense or porous low dielectric films. Therefore, the copper diffusion depth ca n be an indication of the fast reliability evaluation for the future low-k dielectrics applications.
BP7 Zirconium Modified Aluminide Coatings Obtained by the CVD and the PVD Methods.
Jolanta Romanowska, Maryana Zagula-Yavorska, Jan Sieniawski (Rzeszów University of Technology, Poland); Janusz Markowski (Wrocław University of Technology, Poland)

The paper presents the comparison of the structures of the zirconium modified aluminide coatings deposited on pure nickel by the CVD and PVD processes.

In the CVD process, zirconium was deposited from the ZrCl3 gas phase at the 1000 ºC. In the PVD process, the zirconium layer 7 μm thick and the aluminum layer 0.5 μm thick or zirconium layer 7 μm thick and the aluminum layer 0.7 μm thick were deposited by the Electron Beam Evaporation method. Deposition velocity was about 1 μm/min. The layers obtained by the Electron Beam Evaporation method were subjected to diffusion heating at 1050 ºC for 2 h in the argon atmosphere. The obtained coatings were examined by the use of an optical microscope (microstructure and coating thickness ) a scanning electron microscope ( chemical composition on the cross-section of the modified aluminide coating) and XRD phase analysis. Microstructures and phase compositions coatings obtained by different methods are differ significantly. NiAl(Zr), Ni3Al and Ni(Al) phases were found in the CVD aluminide coatings, whereas Ni5Zr and γNi(AlZr) were observed in coatings obtained by the PVD method. The results indicate, that the microstructure of the coating is strongly influenced by the method of manufacturing.

BP8 Phase Stability, Thermal Stability and Oxidation Resistance of Arc evaporated Ti-Al-Ta-N Coatings
Robert Hollerweger (Christian Doppler Laboratory for Application Oriented Coating Development at Montanuniversitat Leoben and Vienna University of Technology, Austria); Mirjam Arndt, Richard Rachbauer (OC Oerlikon Balzers AG, Liechtenstein); Peter Polcik (PLANSEE Composite Materials GmbH, Germany); Jörg Paulitsch, Paul Mayrhofer (Vienna University of Technology, Austria)

Alloying Ti-Al-N with Ta has proven to enhance the hardness, thermal stability and oxidation resistance of sputter deposited coatings. To meet a balance between all these requirements for protecting tools during drilling and cutting applications, an optimized chemical composition of Ti, Ta and Al within the cubic stability range is necessary. However, only limited information is available on arc-evaporated Ti-Al-Ta-N coatings. Therefore, coating developments with an industrial scaled INNOVA Oerlikon Balzers plant, using powder metallurgical (Ti0.50Al0.50)0.95Ta0.05, (Ti0.50Al0.50)0.90Ta0.10, (Ti0.34Al0.66)0.95Ta0.05 and (Ti0.34Al0.66)0.90Ta0.10 targets, were carried out and investigated with respect on their phase stability, mechanical properties as well as thermal stability and oxidation resistance. Vacuum annealing treatments exhibit retarded film decomposition by the addition of Ta. Consequently, the formation of the stable wurzite AlN phase is shifted to higher annealing temperatures of ~1200°C, accompanied by the formation of hexagonal Ta2N. Furthermore, alloying Ta to Ti-Al-N promotes the formation of a dense oxide scale. Therefore, the Ti-Al-Ta-N coating is still intact under a protective oxide, even when treated at 950°C for 20h in ambient air.

BP9 Superhard and Corrosion Protective Coatings of Ta-Si-N and Nb-Si-N
Giovanni Ramirez (Argonne National Laboratory, US); Sandra Rodil, Stephen Muhl (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico); Enrique Camps, Luis Escobar-Alarcon (Instituto Nacional de Investigaciones Nucleares de Mexico)

In this work two different superhard coatings that improve the corrosion resistance were prepared, Nb-N-Si and Ta-N-Si.

The coatings were deposited using a reactive dual magnetron sputtering system, using two targets, one metallic target (Nb or Ta) and a silicon target, in a reactive mixture of gases (argon and nitrogen). Coatings with different concentrations of silicon were grown, which was controlled by varying the RF-power applied on the silicon target.

The microstructural properties, measured using X-ray diffraction, showed the growth of crystalline coatings presenting the FCC phase of the metallic nitrides (NbN or TaN). The composition of the films was measured using x-ray photoelectron spectroscopy (XPS). The hardness was obtained using the nanoindentation technique, finding the maximum values of hardness around to 5% at. of Si in both systems (Ta-N-Si and Nb-N-Si), with values higher of 35 GPa for the Nb-N-Si, and higher of 40 GPa for the Ta-N-Si.

The hardest films of Nb-N-Si and Ta-N-Si were grown on stainless steel substrates and evaluated using two different electrochemical techniques: DC polarization and electrochemical impedance spectroscopy. The films were compared with the substrate and with the NbN and TaN without silicon inclusion. The results showed a good improvement of the corrosion resistance in comparison to both the bare substrate and the metal nitride coating without silicon.

Scratch test was used to measure the adhesion of the coatings to the substrate, and the results showed that the Si inclusion in the TaN system improved the adherence of the coating compared with the TaN. However in the system of the Nb-N-Si there were not significant changes in the substrate-coating adhesion relative to the NbN coatings.

The most important conclusion of this research was that it was possible to design coatings presenting both properties; corrosion resistance and high hardness.

Acknowledgements: We wish to acknowledge the financial support from DGAPA-UNAM IN103910. G. Ramírez acknowledges CONACYT for his PhD scholarship.

BP10 Simple Relationships Between Characteristics of Complex Nitrides and Electronegativities and Radii of Constituent Elements
Vit Petrman (University of West Bohemia, Czech Republic); Jiri Houska (University of West Bohemia - NTIS, Czech Republic)

The paper deals with characteristics of ternary (M1M2N) and quaternary (M1M2M3N) metal nitrides (M = Ti, Zr, Hf, V, Nb or Ta) of various compositions obtained by ab-initio calculations. We focus on comparison of formation energies (E0), bulk moduli (B), shear moduli (G) and an improvement of B and G over weighted average of B and G of binary metal nitrides (ΔB and ΔG) with electronegativities and atomic radii of the constituent elements.

For elastic moduli of M1M2N we find that ΔB (up to 19 GPa), ΔG (up to 20 GPa) and G itself increase with increasing difference between atomic radii of M1 and M2. In parallel, higher E0 leads to higher ΔB (but lower B), and higher |E0| leads to higher ΔG.

For formation energies of M1M2N we find that (i) close atomic radii of M1 and M2 are sufficient for close to zero or highly negative E0, while (ii) close electronegativities of M1 and M2 are necessary for highly negative E0. The solubility of M1N and M2N surprisingly increases (formation energy of M1M2N decreases) with increasing difference between electronic structures of M1N and M2N. The lowest E0 values were observed for Ta-containing M1M2N compositions.

For formation energies of quaternary M1M2TaN we show that in agreement with the above statement, E0 is in all cases lower compared to M1M2N (at higher B). The drop in E0 (improved solubility) resulting from Ta incorporation is more significant for lower atomic radius and higher electronegativity of the other metals M1 and M2.

Overall [1], we present trends which allow one to understand and predict which materials form (stable) solid solutions, and which materials exhibit enhanced elastic moduli. There is a special role of tantalum in stabilizing the solid solutions. The phenomena shown can be tested experimentally, and examined for a wider range of materials.

[1] V. Petrman and J. Houska, J.Phys: Condens. Matter, submitted (2012)

BP11 Internal Oxidation of Nanolaminated Nb–Ru Coatings
Yung-I Chen, Hsiu-Nuan Chu (National Taiwan Ocean University, Taiwan, Republic of China)

Nb–Ru multilayer coatings with various chemical compositions were deposited on silicon wafers by using a direct current magnetron co-sputtering system. By varying the substrate-holder rotation speeds, the Nb–Ru coatings exhibited distinct nanolaminated structures with various periods. The annealing treatments were conducted at 400oC, 500oC, and 600oC under atmospheres of 50-ppm O2–N2 and 1% O2–Ar, respectively. The Nb oxidized preferentially when annealed in oxygen-containing atmospheres. The oxidized Nb–Ru coatings formed a nanolaminated oxide/metal structure, attributed to the internal oxidation behavior. The maintenance of nanolaminated structure for various Nb–Ru coatings after annealing was studied. The variations in crystalline structure, nanohardness, surface roughness and chemical composition of Nb–Ru coatings caused by annealing were widely investigated.

BP12 Phase Stability, Structural and Elastic Properties of Ternary Cr1-xTMxN alloys: An Ab-initio Study
Liangcai Zhou (Vienna University of Technology and Montanuniversität Leoben, Austria); David Holec (Montanuniversität Leoben, Austria); Paul Mayrhofer (Vienna University of Technology, Austria)

In order to improve the mechanical properties, wear resistance and high temperature oxidation resistance of CrN coatings, alloying with other group IIIB-VIB transition metal (TM) elements (e.g., Y, Ti, Zr, Hf, V, Nb, Ta, Mo, W) becomes an important concept in the industrial area, and hence attracts also attention of the scientific community. In this paper with present an extensive first principles study of the phase stability, structural and elastic properties of Cr-containing cubic TM nitrides, where Cr substitutes for TM (i.e. Cr1-xTMxN). The calculated equilibrium lattice parameters exhibit a deviation from Vegard’s linear interpolation to larger values. An addition of a small amount of TM elements into CrN results in softening of the material as measured by the bulk modulus, while significant increase in bulk modulus is predicted for Ta- and Nb-rich Cr1-xTMxN alloys (x>0.6). The phase stability is studied as a function of the TM valence electron concentration and thus linked with the electronic structure. Finally, the single crystal elastic constants of Cr0.5TM0.5N are calculated using the stress-strain method. Employing some representative sample textures allows us to discuss the influence of the TM on the polycrystalline elastic behavior of CrN. All these compositional trends are compared with the available experimental data.

BP13 Substrate Bias eEfects on the Wear and Hydrophobic Properties of CrAlN Coatings Prepared by Close Filed Unbalanced Magnetron Sputtering
Yu-Sen Yang, Ting-Pin Cho, Jia-Hau Lin (National Kaohsiung First University of Science and Technology, Taiwan, Republic of China)
CrAlN coatings were deposited in Ar/N2 plasma at 30-50% nitrogen flow rate ratios and DC pulsed substrate bias by using the reactive magnetron sputtering process. The hydrophobic and hydrophilic properties were evaluated by using water contact angle (WCA) measurement. Wear-resistant properties were evaluated by using ball-on-disc testers. Microstructure and morphology were observed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results show that the hardness and wear resistance increases obviously with increasing substrate bias from 0V to -100V. Due to the formation of (CrAl)2N solid solution phase at -60V substrate bias, the coatings exhibits the hydrophobic behavior with WCA at 104 degree. At high nitrogen flow rate ratios and low substrate bias the surface become hydrophilic with WCA lower than 90 degree.
BP14 Electrolyte-Insulator-Semiconductor (EIS) with Gd2O3-based Sensing Membrane for pH-Sensing Applications
Hsiang Chen (National Chi-Nan University, Taiwan, Republic of China); ChuanHaur Kao (Chang Gung University, Taiwan)
The electrolyte-insulator-semiconductor (EIS) devices with Gd2O3 5 sensing membranes were fabricated on 4-in p-type (1 0 0) Si wafers, which have a resistivity of 5–10 Ω -cm. After standard RCA clean process, samples were dipped into 1% hydrofluoric acid to remove native oxide from the surface. A ~ 25nm Gd2O3 film was deposited on Si substrate through reactive sputtering from a Gadolinium target in diluted O2 Samples were annealed at different temperatures (700℃.800℃.900℃) by rapid thermal annealing (RTA) in O2 ambient for 30 sec. The back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then sensing membrane size was defined through photolithographic processing under a photosensitive epoxy (SU8-2005, MicroChem Inc.) that behaves as an antacid polymer. EIS devices were then fabricated on the copper lines of a printed circuit board by using a silver gel to form conductive lines. A hand-made epoxy package was employed to encapsulate the EIS structure and the copper line. The physical properties of the high-k Gd2O3 and Gd2TiO5 sensing membrane are investigated by Atomic Force Microscopy (AFM). Besides, to evaluate the sensor performance, PH sensitivity, hysteresis, and drift rate were measured to find the most preferable treatment condition.
BP15 Reactive and Non-reactive Sputter Deposition of Metallic, Intermetallic and Ceramic Target Materials to Prepare Al-Cr-N Coatings
Corinna Sabitzer (Christian Doppler Laboratory for Application Oriented Coating Development at the Institute of Materials Science and Technology, Vienna University of Technology, Austria); Jörg Paulitsch (Vienna University of Technology, Austria); Peter Polcik (PLANSEE Composite Materials GmbH, Germany); Mirjam Arndt, Richard Rachbauer (OC Oerlikon Balzers AG, Liechtenstein); Paul Mayrhofer (Vienna University of Technology, Austria)

AlxCr1-xN coatings are highly valued for various industrial applications based on their outstanding mechanical properties and oxidation resistance. Even though deposition parameters like partial pressure, gas mixture or temperature are well investigated and optimized; only little information is available on the influence of the target material itself. Therefore, AlxCr1-xN coatings were deposited by reactive and non-reactive unbalanced magnetron sputtering using three different powder-metallurgically prepared targets: a metallic Al/Cr target, an intermetallic AlCrx target and a ceramic AlN/CrN target. XRD analyses indicate for all targets tested a single cubic microstructure. The coatings deposited from the metallic and intermetallic target demonstrate a columnar structure with a pronounced (111) orientation whereas the coating deposited from the ceramic target is fine crystalline with (200) orientation. Furthermore, the hardness is highest for those coatings prepared from the ceramic target material.

BP16 The Young’s Modulus of Composite Spacer Contributed on the Stress Effect of N-MOSFET with Contact-etch-stop Layer Stressor
Yung-Chuan Chiou (National Chiayi University, Taiwan, Republic of China); Chang-Chun Lee, Tzai-Liang Tzeng (Chung Yuan Christian University, Taiwan, Republic of China); Chien-Chao Huang (National Nano Device Laboratories, Taiwan, Republic of China)
Contact-etch-stop layer (CESL) stressor is able to generate higher tensile stress on channel direction (sxx) for enhancing N-MOSFET drive current. To analyze the analytic solution of residual stresses and bending in multi-layer/substrate systems, the Young’s modulus of thin film could control this stress level of substrate surface except for the stress and thickness of thin film. In general, two dielectrical layers, LPCVD oxide and SiN, were formed a composite spacer with liner oxide and spacer nitride in succession for most of the device structures. The Young’s moduli of LPCVD oxide and nitride were determined to 67-GPa and 375-GPa by using the nanoindenter, respectively . To address the concern topic, the Young’s modulus of composite spacer with CESL stressor by using the Sentaurus/TSUPREM4 simulation is to study. The analytic result shows that the channel stress is obviously reduced with decreasing the Young’s modulus of spacer materials. Furthermore, if liner oxide is kept at 15-nm, the reduction of spacer SiN width does not increase channel stress obviously, even the CESL stressor is closer to channel. Our experimental data strongly supports the aftermentioned simulation for identifying the role of liner oxide and spacer nitride. When the thickness of liner oxide is reduced from 15-nm to 5-nm, drive current of N-MOSFET is enhanced by 4% and without performance gain for thin remained SiN spacer but with 15-nm liner oxide.
BP17 Thermal Stability and Oxidation Resistance of TiAlN/TaAlN Multilayer Coatings
Christian M. Koller (Christian Doppler Laboratory for Application Oriented Coating Development at Montanuniversitat Leoben and Vienna University of Technology, Austria); Robert Hollerweger (Vienna University of Technology, Austria); Richard Rachbauer (OC Oerlikon Balzers AG, Liechtenstein); Peter Polcik (PLANSEE Composite Materials GmbH, Germany); Jörg Paulitsch (Vienna University of Technology and Montanuniversität Leoben, Austria); Paul Mayrhofer (Vienna University of Technology, Austria)

Mechanical properties, thermal stability and oxidation resistance of Ti1-xAlxN coatings are well investigated and recent studies indicated that these properties can considerably be improved by alloying elements such as Cr, Ta or Y to form quaternary nitrides. However within this study we want to focus on an architectural approach by depositing multilayer arrangements of TiAlN and TaAlN. Further on, combined processing of reactive arc-evaporated Ti1-xAlx targets with either arced (arc) or sputtered (rsd) Ta1-yAly targets are carried out opening the possibility to deposit coatings with variable chemical and structural modulations.

Our investigations show that the TiAlNarc/TaAlNarc multilayers exhibit enhanced thermal phase stability with peak hardness values of ~ 35 GPa up to Ta=1200 °C, whereas the TiAlNarc/TaAlNrsd multilayers exhibit hardness values of ~35 GPa up to Ta=800 °C which decrease to ~32 GPa when Ta=1100 °C. However, oxidation investigations clearly demonstrate the advantage of this hybrid arc/rsd process as the TiAlNarc/TaAlNrsd nitride coatings still remain intact after oxidising in air at 850 °C for 20 h, whereas the TiAlNarc/TaAlNarc multilayer coatings are completely oxidised.

BP18 Investigation of Corrosion Properties in TiAlN/TiCrN Multilayer Coatings Deposited by CFUBMS
Ebru Demirci (Atatürk University, Turkey); Ozlem Baran (Erzincan University, Turkey); Yasar Totik, Ihsan Efeoglu, Tahmasebian Morteza (Atatürk University, Turkey)

Advanced tribological properties, high temperature oxidation resistance, excellent corrosion performance of Ti alloy coatings (such as TiN, TiAlN and TiAlN/CrN) make them an important candidate to be utilized in many applications such as tool coatings. In actual working environments one of the main degradation causes of thin films is corrosion; therefore its evaluation processes have high importance. In the present study, TiAlN/TiCrN multilayer coatings were deposited by closed field unbalanced magnetron sputtering from two Cr, one Al and one Ti targets. The structural properties of coatings have been analyzed by electron microscopy (SEM), X-Ray diffraction (XRD) and energy dispersive spectrometry (EDS). Additionally, corrosion properties of these coating were investigated by using polarization test unit.

Keywords: TiAlN/TiCrN; Corrosion; Multilayer Coating; Sputtering
BP19 Simulation of Neutral Gas Dynamics for PVD DC-MSIP and HPPMS Processes
Kirsten Bobzin, Nazlim Bagcivan, Sebastian Theiss, RicardoHenrique Brugnara, Marcel Schäfer (Surface Engineering Institute - RWTH Aachen University, Germany); Ralf Brinkmann, Thomas Mussenbrock (Institute for Theoretical Electrical Engineering - Ruhr University Bochum, Germany); Jan Trieschmann (Surface Engineering Institute - RWTH Aachen University, Germany)
PVD processes such as DC Magnetron Sputtering Ion Plating (DC-MSIP) and High Power Pulse Magnetron Sputtering (HPPMS) are commonly used to produce hard protective coatings for corrosion and wear resistance applications. A uniform layer of coating material is an essential requirement for an effective protection of the coated parts. It is therefore important to understand the gas dynamic processes inside the reactor chamber to optimize the quality of the coatings. In particular, the dynamics of the process gas as well as of the film forming particles sputtered from the target material are of interest. In complex industrial scale coating units the spatial distribution of particles can only be predicted using numerical models. Depending on the geometry of the reactor chamber and the process pressure, different computational models can be used. The flow regime and in consequence the appropriate numerical model is determined by the Knudsen number (Kn) equal to the mean free path over the typical length scale. For Kn < 0.01, continuum models such as computational fluid dynamics (CFD) models allow for a precise description of the gas flow. In contrast, in pressure regimes with Kn > 2 only kinetic models provide an accurate description, e.g. the Direct Simulation Monte-Carlo (DSMC) method. Generalized limits for the validity of the different models in the transition regime 0.01 < Kn < 2 cannot be found.
In this work we investigate an industrial scale hybrid magnetron sputtering coating unit operated at pressures around 5 * 102 mPa. Due to the low pressure, the magnetron discharge operates in the already mentioned transition regime. In consequence, both CFD as well as DSMC simulations may provide an appropriate physical description. For our analysis we employ the commercially available FLUENT software V14 and the freely available OpenFOAM simulation package. Results obtained using the CFD and the DSMC approach are compared to investigate the applicability of the different models. The CFD simulations reveal all the principle flow characteristics at relatively low computational costs. The computationally costly DSMC method, however, provides a more detailed picture of the flow dynamics inside the reactor chamber, in particular in regions where Kn ≈ 1. The kinetic approach provides a more precise description especially at small features of the geometry. In addition, the DSMC routines provided with OpenFOAM can easily be extended with respect to a kinetic description of the coating forming particles sputtered from the target materials. Resulting, this allows for an analysis of the coating formation on the substrates.
BP20 Oxidation Resistance and Mechanical Properties of Ta – Si – N Coatings
Yung-I Chen, Kun-Yi Lin (National Taiwan Ocean University, Taiwan, Republic of China)
Ta–Si–N coatings were prepared by reactive direct current magnetron co-sputtering on silicon substrates. By varying the sputtering powers, Ta–Si–N coatings exhibited various chemical compositions and crystalline characteristics. The low Si-content Ta–Si–N coatings revealed a face centered cubic phase, whereas the high Si-content coatings revealed an amorphous phase in the as-deposited states. To explore the oxidation resistance and mechanical properties of the Ta–Si–N coatings, the annealing treatments were conducted in a 1%O2-99%Ar atmosphere at 600 oC for 4–100 h. The material characteristics of the annealed Ta–Si–N coatings were examined by Auger electron spectroscopy, transmission electron microscopy, atomic force microscopy, and a nanoindentation tester. The Si oxidized preferentially in the Ta–Si–N coatings. The in-diffusion of oxygen during annealing was restricted by the formation of a SiOx surface scale. Because of its resistance to oxidation and low surface roughness of 2–3 nm, Ta–Si–N coatings were proposed as a protective coating for die material utilized at high temperature in low oxygen containing atmospheres.
BP21 Structural and Optical Properties of Brominated Plasma Polymers
Marcelo Appolinario, Antonio Neto (UNESP, Brazil); Wido Schreiner (UFPR, Brazil); Nilson Cruz, Elidiane Rangel, Steven Durrant (UNESP, Brazil)

Brominated amorphous hydrogenated carbon films were produced by the plasma polymerization of bromoform-acetylene mixtures. There is little extant literature on this type of film. Varying the proportion of bromoform in the mixture allowed the production of non-brominated to highly brominated films (up to about 43 at% Br); thus the main parameter of interest was the degree of bromination, RB. The films were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photo-electron Spectroscopy (XPS). Ultraviolet-visible Near-Infrared Spectroscopy was employed to allow calculation of the optical properties, such as the refractive index, n, absorption coefficient, α(E), where E is the photon energy, and the optical gap, Eg, as a function of RB. Semi-empirical modeling of Eg as a function of RB was applied. In addition, nano-indentation studies revealed the hardness, modulus and stiffness of the films.

BP22 First Principles Study of Alloying Trends in Ti—Al—N and Cr—Al—N Systems
David Holec (Christian Doppler Laboratory for Application Oriented Coating Development at Montanuniversitat Leoben and Vienna University of Technology, Austria); Liangcai Zhou (Vienna University of Technology and Montanuniversität Leoben, Austria); Richard Rachbauer (Montanuniversität Leoben, Austria); Paul Mayrhofer (Vienna University of Technology, Austria)

We employ Density Functional Theory modelling to study the effect of early transition metal (TM) elements (Y, Zr, Nb, Hf, and Ta) on the structural and mechanical properties of Ti–Al–TM–N and Cr–Al–TM–N systems.

While Y decreases significantly the maximum solubility of AlN in the cubic phase of the alloy, the other elements have only a negligible effect when their amount is less than ~10at.% on the metallic sublattice. The lattice parameter bows out to larger values as compared with Vegard's linear interpolation, owing to a gradually changing character of the bonds in the alloy with composition. The chemical strengthening is most pronounced for Ta and Nb, although also causing smallest elastic distortions of the lattice due to their atomic radii being comparable with Ti and Al. This is further supported by the analysis of the electronic density of states.

Mixing enthalpy, used as a measure of the driving force for decomposition into the stable constituents, is enhanced by adding Y, Zr and Nb, suggesting that the onset of spinodal decomposition will appear in these cases for lower thermal loads than for Hf and Ta alloyed Ti1-xAlxN.

BP23 Pulsed Laser Deposition of Tetrahedral Amorphous Carbon Layers (ta-C) – Properties in Dependence of Laser Fluence on the Target- Surface
Katja Guenther, Steffen Weiβmantel (University of Applied Sciences Mittweida, Germany)

Recently, we developed a novel method for the preparation of several micrometer thick super-hard tetrahedral amorphous carbon (ta-C) films with low internal stress. The method is a combination of excimer laser ablation for film deposition and excimer laser irradiation of as-deposited sub-layers for the reduction of the high stresses.

We will show that the variation of the laser beam spot size on the target surface influences the creation of particulates in the ta-C layers. With this the mechanical properties are affected. For the investigations ta-C layers have been deposited on hard metal substrates using only the nearly perpendicularly from the target surface ablated species. With the SEM, the particulates will be characterized. Nanoindentation was used for the measurement of hardness and the scratch test shows the critical loads.

Furthermore the influence of the repetition rates of the laser beam during the ablation process was analyzed. It was found that mechanical properties are not affected by the change of the repetition rates.

We will show that this variation of the laser beam spot size with the particulates must be taken into account if the mechanical properties of the ta-C layers should be optimized and that the deposition rate can be increased by using higher laser beam repetition rates.

BP24 Tribological Properties of TiN/TaN and TiN/TaN Doped CrY Multilayer Coatings at High Temperature
Ihsan Efeoglu (Atatürk University, Turkey); Ozlem Baran (Erzincan University, Turkey); Ebru Demirci, Yasar Totik (Atatürk University, Turkey)

In this study, TiN/TaN and TiN/TaN doped CrY multilayer coatings were deposited on M2 substrates using Closed Field Unbalanced Magnetron Sputtering (CFUBMS). The structural properties of coatings were analyzed by using Xray Photoelectron Spectroscopy (XRD), (energy-dispersive spectroscopy) EDS, Scanning Electron Microscopy (SEM). The hardness values of coatings were determined with a microhardness tester. Friction and wear properties of the coatings were determined by using pin-on-disc tribometer at humid air and high temperature.

Key Words: TiN/TaN, CrY, multilayer coatings, CFUBMS

BP25 The Effect of Annealing Temperatures on the Hydrophobic Property of CrAlN Coatings
Yu-Sen Yang, Ting-Pin Cho, Jia-Hau Lin, Shih-Han Yang (National Kaohsiung First University of Science and Technology, Taiwan, Republic of China)
The CrAlN coatings were deposited in Ar/N2 plasma by using the reactive magnetron sputtering process. The coating parameters were controlled at bias voltage -100 V and N2 flow rate ratio 40 %. The film thickness was controlled to be around 2μm. The CrAlN coatings were annealed for one hour between 600 and 1100℃ at 100℃interval. The hydrophobic and hydrophilic properties were evaluated by using water contact angle (WCA) measurement. The experimental results show that the as-deposited CrAlN coatings and annealing temperatures below 800℃ the surface exhibit hydrophobic property with WCA around 102o. As the annealing temperature increases from 800 to 1100℃, the WCA decrease evidently from 102o to 45o and the surface become more hydrophilic. The XRD results show that when the annealing temperatures were greater than 900 ℃ the Cr-Al-N phases were fully oxidized to become Cr2O3 and WCA drops from 78o down to 45o.
BP26 Effect of CO Gas for CVD Ti(C,N,O) Coating Layers on MT-TiCN Ⅰ : CO Gas Effect
Sangwoong Na, Jiheon Kim, Eunsoo Lee, Doyeon Kim, Sihoon Song, Moshe Sharon (TaeguTec, Republic of Korea); Bongki Min (Yeungnam University, Republic of Korea)
CVD deposited TiCNO layer was well known in cutting tool applications as one of buffer layer between the mid-temperature TiCxNy and alpha-Al2O3. The role of TiCNO layer is strong bonding between mid-temperature TiCxNy and alpha-Al2O3 layer, and texture control of Al2O3. Especially, the shape, composition and texture of TiCNO determine the alpha-Al2O3 texture and size.
In this study, TiCl4-CH4-CO based gas mixture was used for coating of TiCNO on the (422) and (311) based mid-temperature TiCxNy, which stands on the cemented carbide substrate. The range of CO gas volume was 0 to 2 % and over 2 ㎛ coating layer was obtained to identify the shape and texture of TiCNO layer. Small amount of CO gas abruptly changed the shape and texture of TiCNO layer and the low Kv EDS mapping data showed incorporation of relatively large amount of oxygen at high temperature. Along with the EDS analysis, SIMS and EPMA analysis was also done for the composition variations of TiCNO with CO variations. Low angle backscattering SEM mode was used to achieve the exact shape of cross section of lenticular TiCNO, pore size and pore distributions. As increasing the CO gas volume, thickness of TiCNO layer goes to double at the same deposition time that compares to 0 % CO gas condition, and thinner and longer lenticular TiCNO was developed. The pore size of lenticular TiCNO reduced and the specific surface area increased at high amount of CO gas. Compare to mid-temperature TiCxNy, texture of CO gas involved TiCNO layers showed the strong (111) preferred orientation and portion of (200) and (220) also increased. XRD analysis indicated that low to high amount addition of CO gas brings the lattice contraction of TiCNO layer.
BP27 Effect of CO Gas for CVD Ti(C,N,O) Coating Layers on MT-TICN Ⅱ : Temperature Effect
Sangwoong Na, Eunsoo Lee, Jiheon Kim, Doyeon Kim, Sihoon Song, Hyunjun Han (Taegutec, Republic of Korea); Jaehyung Lee (Yeungnam University, Republic of Korea)
There are many kinds of buffer layers between the mid-temperature TiCxNy and alpha-Al2O3 CVD coating on the cemented carbide cutting tool substrate. The role of buffer layer is strong bonding between mid-temperature TiCxNy and alpha-Al2O3 layer, and texture control of Al2O3. Additionally, buffer layer also requires the adequate physical properties as one of active layer for cutting. So, the size, density, composition and texture formation of buffer layer are important for the total performance of CVD based cutting tool.
This study focused on the temperature effect for one of carbon rich TiCNO base buffer layer formation. (422) and (311) based mid-temperature TiCxNy coating on the cemented carbide substrate was selected for substrate of buffer layer. Coating temperature was 1000 ℃, 950 ℃ and 900 ℃, and TiCl4-CH4-CO based gas mixture was used. Although the coating time was the same for three coating conditions, total coating thickness of three temperature condition was similar. But low angle back scattering SEM image for cross section of the coated buffer layer indicated that total volume of the coating layer was decreased by pores as the temperature decreasing. Shape of buffer layer also decreased with temperature deceasing and more sharp lenticular type buffer layer was obtained at low temperature. Low Kv EDS mapping data showed incorporation of relatively large amount of oxygen at entire temperature range. Along with the EDS analysis, SIMS and EPMA analysis was also done for the composition variations of each TiCNO layers. As the temperature decreasing, (111) preferred orientation was declined but intensity of (200) and (311) peak was increased.
BP28 Wear and Oxidation Behaviors of Ti(C, N, O) Coatings
Jang-Hsing Hsieh, YuanLiang Lai, Y.R. Cho (Ming Chi University of Technology, Taiwan, Republic of China)
It has been known that the life time of Ti-based hard coatings is dependent on the oxidation rate of Ti. Here, Ti(C,N,O) coatings prepared by a unbalance magnetron sputtering were studied and compared using a static oxidation approach as well as a pin-on-disc tribometer. Ti(C,N,O) thin film prepared with different N2/O2 flow rates were deposited on M2 steel substrates. The films properties were analyzed by Raman spectroscopy, SEM and X-ray diffraction. These samples then went through static oxidation and tribological testing. The surface morphology and the thickness of oxidation layer were obtained by using scanning electron microscopy (SEM).

In static oxidation, the formed titanium oxide (TiO2) was found to have mainly anatase structure at temperatures between 500ºC to 600ºC and transform to rutile structure at temperature higher than 600ºC. Through this study, oxidation rate and activation energy of oxidation for each sample were evaluated. It is found the samples exhibited higher activation energy could have higher oxidation resistance. These results are consistent with those obtained from wear testing.

BP29 Improved Performance of Metal-based Dye-sensitized Solar Cells by Introducing a TiN Nanocrystalline Thin Film
Wei-Lun Tai, Fan-Yi Ouyang (National Tsing Hua University, Taiwan, Republic of China)

Metals foils have been increasingly used as alternative substrates for the flexible dye-sensitized solar cells (DSSCs) to overcome the limitations arising from the low sintering-temperature tolerance of the plastic substrates. However, the potential problem of metal corrosion in the iodide-based electrolytes threatens to degrade the performance and long-term stability of the metal-based DSSCs. To resolve this dilemma, we have employed unbalanced magnetron sputtering systems to prepare nanocrystalline TiN barriers on the metal substrates as a photo-electrode. The energy conversion efficiency of TiN deposited DSSC reaches about 4.5% under illumination with a light intensity of 100mW-2. The improved durability of DSSC has also been observed as compared to uncoated metal based DSSC. The mechanism of enhanced efficiency and durability of TiN coated DSSC will be discussed in this talk.

BP30 Super Smooth Nano-Structured Carbon Films with Cross-linked Graphitic Sheets Induced by ECR Ion Irradiation
Xue Fan (Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi’an Jiaotong University, China); Dongfeng Diao (School of Mechanical Engineering, Xi’an Jiaotong University; College of Mechatronics and Control Engineering, Shenzhen Univeristy, China); Lei Yang (Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi’an Jiaotong University, China)

Nano-structured carbon films with cross-linked graphitic sheets exhibited good mechanical and electrical properties. When applying the films in the ultra precision system, very smooth surface is needed. We studied that the nanostructure of carbon films was tailored by ion irradiation energy in electron cyclotron resonance (ECR) sputtering, and the surface morphology was smoothed simultaneously. The nanostructure and bonding configuration were characterized by transmission electron microscopy (TEM) observation, Raman and X-ray photoelectron spectroscopy (XPS) spectra analysis. Upon increasing of ion irradiation energy, the graphitic sheets in nanocrystalline graphite were cross-linked with sp3 bonds. XPS results and the peak density ratio of ID/IG from Raman spectra also showed the increase of sp3 bonds content. The surface morphology of the nano-structured carbon films were tested by atomic force microscopy (AFM). Results indicated thatthe mean surface roughness (Ra) was decreased from 0.2 nm to 0.03 nm when the nanostructure changed from graphite clusters to cross-linked graphitic sheets. Super smooth carbon films correlated with the cross-linked graphitic sheets nanostructure was obtained by ECR ion irradiation.

BP31 Influence of the Bilayer Period on the Structure of AlN and the Mechanical Properties of CrN/AlN Multilayer Coatings
Paul Mayrhofer (Vienna University of Technology, Austria); Manfred Schlögl (Vienna University of Technology and Montanuniversität Leoben, Austria); Bernhard Mayer, Vipin Chawla, David Holec (Montanuniversität Leoben, Austria)

CrN/AlN multilayer coatings exhibit improved mechanical properties and thermal stability, especially when a superlattice structure is formed. To obtain this superlattice structure both layer materials (CrN and AlN) have to exhibit the same crystal structure and a similar lattice parameter. However, a systematic study on the influence of the individual layer thicknesses of CrN and AlN on structural and mechanical properties of CrN/AlN superlattice coatings is still missing. Therefore, CrN/AlN multilayer coatings were prepared by DC reactive magnetron sputtering with AlN layer thicknesses of 1, 2, and 3.3 nm and varying the CrN layer thicknesses from 0.9 to 10 nm. The thereby obtained bilayer period (Λ) and structure of the CrN/AlN coatings was investigated by low-angle and high-angle X-ray diffraction (LAXRD and HAXRD) as well as high-resolution transmission electron microscopy (HRTEM). The hardness as a function of Λ was determined with an ultra-micro-indentation system and the residual stresses were obtained by the substrate-curvature method at room temperature.

The results suggest that the minimum CrN layer thickness, necessary to stabilize the AlN layers in their metastable cubic structure, is in the range of the AlN layer thickness themselves. Hence, for the CrN/AlN coatings composed of 1, 2, and 3.3 nm thin AlN layers the CrN layers need to be at least 1, 2, and ~3 nm, respectively. For thinner CrN layers an X-ray amorphous structure or a multiphase arrangement of cubic, wurtzite-like, and amorphous phases is obtained. Exemplarily, the CrN/AlN superlattice coating composed of 1 nm thin AlN and 1.9 nm thin CrN layers (Λ = 2.9 nm) was investigated by cross-sectional HRTEM. These studies confirmed the superlattice structure–suggested by LAXRD and HAXRD–by the almost perfect hetero-epitaxial relationship between c-CrN and c-AlN. This CrN/AlN superlattice coating, as well as the one composed of 2 nm thin AlN and 3.5 nm thin CrN (Λ = 5.5 nm) exhibit a hardness maximum of ~31 GPa. If the AlN layer thickness is ~3.3 nm the hardness peak is obtained only with ~28.5 GPa for a bilayer period of Λ = 6.3 nm. The resulting hardness-peak as a function of the bilayer period becomes broader with increasing AlN layer thickness. A corresponding dependence on the bilayer period is also obtained for the compressive stresses.

Based on the results it can be concluded that the arrangement of 1 nm thin AlN layers with 1.9 nm thin CrN layers or 2 nm thin AlN layers with 3.5 nm thin CrN layers will result in the formation of a superlattice CrN/AlN structure having a hardness of ~40 % above that of the layers they are formed.
BP34 Mechanical Properties and Interface Adhesion of Molybdenum Single Layer on Soda-lime Glasses
Huan-Hsin Sung (National Chung Hsing University, Taiwan, Republic of China); ZueChin Chang (National Chin-Yi University of Technology, Taiwan, Republic of China); Li-Yu Kuo, Fuh-Sheng Shieu (National Chung Hsing University, Taiwan, Republic of China)

In this study, the Mo thin films were deposited on soda lime glass substrates through varies sputtering current by DC magnetron sputtering system. The structure of Mo films showed (110) preferred orientation. The electrical properties of Mo films indicated well conductive in this study. The mechanical properties of Mo thin films which were measured by nano-indentation, and the adhesion properties of interface between glass substrate and Mo film were investigated by nano-scratch. We were found that interface adhesion energy between Mo film and glass substrate was enhanced from 0.06 to 9.48 J/m2, as sputtering current was increased. In this study, we were offered quantitative method to analysis adhesion properties, also including verify the feasibility in tribological application.

BP35 Effects of Silicon Content on the Structure and Mechanical Properties of (AlCrTaTiMo)N Coatings by Reactive Magnetron Sputtering
Du-Cheng Tsai, Fuh-Sheng Shieu (National Chung Hsing University, Taiwan, Republic of China)

Si-doping (AlCrTaTiMo)N coatings were deposited onto Si substrate by the radio-frequency (RF) magnetron sputtering of a AlCrTaTiMo alloy target under direct current bias in a N2/Ar atmosphere. The crystal, microstructural, mechanical, and electrical properties at different N2-to-total (N2+Ar) flow-rate ratios (RN) values were investigated. As the silicon content reached 7.43 at%, the nitride remained as a simple NaCl-type face-centered cubic (FCC) structure. The lattice decline occur, implying that the incorporated silicon atoms can dissolve into the (AlCrTaTiMo)N lattice by substitution. The silicon incorporation significantly improved the mechanical properties and oxidation resistance of (AlCrTaTiMo)N coatings, however, deteriorated the electrical properties.

BP36 Effect of In-Situ Crystallization on the Microstructural and Photo-induced Properties of TiO2 Coatings Prepared by Magnetron Sputtering
Imane Sayah, Mohammad Arab Pour Yazdi (LERMPS-IRTES, France); Frédéric Schuster (CEA-Saclay, France); Alain Billard (Lrc Cea/irtes-Lermps, France)

TiO2 coatings are still widely studied because of numerous potential industrial applications especially in the environmental fields such as water purification technology, due to its chemical stability, low toxicity, corrosion resistance and low cost [1].

In this study, TiO2 thin films are deposited by reactive magnetron sputtering at high pressure on heated glass slides substrates (from 250 to 550 °C). All of the substrates are covered by 250 nm SiNx barrier layer to avoid the alkali elements diffusion of glass and degradation of TiO2 photocatalytic activity [2-3]. X-ray diffraction, scanning electron microscopy, water angle contact measurement and Orange G decomposition upon UV irradiation are used as characterization technics.

Synthesized films were crystallized in anatase phase and their morphology exhibits a porous structure. The study of the photo-induced properties shows an activity maximum at 450 °C.

Finally, microstructural and photocatalytic properties of the TiO2 coatings in-situ crystallized are compared with those of the films prepared under the same conditions but crystallized ex-situ.

BP37 Thermal Stability of Quaternary TiZrAlN Sputtered Thin Films
Grégory Abadias (Institut P' - Universite de Poitiers, France); Ihar Saladukhin, Sergey Zlotski, Vladimir Uglov (Belarussian State University, Belarus)

The aim of the present work is to study the thermal stability, under vacuum and air annealing, of quaternary transition metal nitride films, namely TiZrAlN, with emphasis on the role of Al content on the structure and phase formation.

(Ti,Zr)1-xAlxN films with thickness of 300 nm have been deposited onto Si (001) wafers by reactive unbalanced magnetron co-sputtering from individual metallic targets under mixed Ar+N2 plasma discharges. Ti and Zr targets were operated in dc mode, at fixed power of 300 and 220 W, respectively, while an RF power was applied to the Al target. The working pressure during deposition was fixed at 0.19 Pa. Varying the RF power of the Al target from 20 to 200 W resulted in metallic atomic fraction of aluminum, x, in the films to increase from 0.026 to 0.364, while the Ti:Zr concentration ratio was kept constant to ~1.0. RBS analysis revealed that N content decreased from ~50 at.% for low Al content (x<0.10) to ~30 at.% for x>0.25.

XRD, AFM, SEM and TEM analyses revealed a structural and morphological evolution upon Al incorporation in the TiZrN lattice. Three growth regimes were identified: i) nanocrystalline TiZrAlN solid solutions with cubic structure for x< 0.11, ii) dual-phase nanocomposites consisting of cubic TiZr(Al)N nanograins surrounded by amorphous TiAlN matrix for 0.11 < x < 0.25, and iii) XRD amorphous films for x> 0.25.

Annealing in vacuum (~10-4 Pa) at the temperature of 600°С doesn't cause any structural changes of TiZrAlN films. After annealing in vacuum at 950°С, the structure of the films depends essentially on the aluminum content. Cubic TiZrAlN films with x=0 and 0.048 remained stable, while phase decomposition into c-TiN and c-ZrN was revealed for x>0.10.

Annealing under air atmosphere was carried out for temperature intervals ranging from 400 to 950°С using in situ temperature XRD. For low Al content (x<0.13), oxidation started at 500°C. Interestingly, an intermediate oxidized amorphous phase was found in the 600-700°C temperature range, followed by crystallization of the orthorhombic (ZrTi)O4 oxide phase at 780°C. For x>0.25, the reduction of oxide formation can be explained by the passivating role of the Al2O3 outer layer. Thus, amorphous TiZrAlN films with high Al content are desirable for a better oxidation resistance.

BP38 The Development and Application on the Process Technique of (ZrxHf1-x)N Thin Film
Yu-Wei Lin (Instrument Technology Research Center, National Applied Research Laboratories, Taiwan, Republic of China); Jia-Hong Huang (Department of Engineering and System Science National Tsing Hua University, Taiwan, Republic of China); Ge-Ping Yu (Institute of Nuclear Engineering and Science National Tsing Hua University, Taiwan, Republic of China)
ZrHfN thin film has attractive attention for its superior mechanical properties (hardness, adhesion, friction resistance), corrosion resistance, higher packing factor, chemical stability and warm golden color as similar to TiN, and it was widely applied in industry in the current decades. ZrHfN film will be deposited by reactive magnetron sputtering, based on modification of the previous results of optimum coating conditions (substrate bias, substrate temperature, system pressure, nitrogen flow etc.) for metal nitride thin films to develop a new deposition condition, to investigate the microstructure, corrosion and mechanical properties of different proportion of the Hf-Zr components. Based on the early studies, metal nitride coatings have attracted attention for good mechanical properties, hardness up to 30 GPa. Moreover, the addition of Zr may further improve the thermal stability of the metal nitride coating. In the study, we should have a generalized definition for substitutional solid solution. The addition of Hf into ZrN (or addition of Zr into HfN) forms the substitutional solid solution ZrHfN (or HfZrN). Different ratios of Hf/Zr will form various structure for (ZrxHf1-x)N with interesting properties, and many characteristics, such as nanostructure, hardness, and residual stress remain to be studied further. The thickness of films will be determined by scanning electron microscope (SEM). Hardness of the films can be measured by nano-indenter, and atomic force microscopy (AFM) is applied to measure the surface roughness of thin film. The preferred orientation and lattice parameter of ZrHfN films will be studied by using X-ray diffraction (XRD). The ratio of N/Hf/Zr and composition in ZrHfN thin film will be ascertained by X-ray Photoelectron Spectroscopy (XPS) and Rutherford Backscattering Spectrometer (RBS). Characterizing the structure and properties of single ZrHfN layer coating with the different ratio of Hf-Zr to find out the optimum processing parameters, and further to tailor a variety of surface coating applications is the objective of this project.
BP39 Deposition of TiN Films by High Power Impulse Magnetron Sputtering
Wan-Yu Wu, Siao-Gu Shih, Ping-Hung Chen, Chi-Lung Chang, Da-Yung Wang (MingDao University, Taiwan, Republic of China)
High power impulse magnetron sputtering (HiPIMS) is a novel technique in physical vapor deposition (PVD) technology. The advantages of HiPIMS include low process temperature, well-adherent coating, better quality of the films, and droplet-free coating process. It provides higher gas dissociation and highly ionized plasma by inputting a high power in short pulses to the target. The target materials are therefore not only sputtered but also ionized during the deposition process. As a result, high power density and plasma density in the order of 1017 to 1019 m-3 can be achieved in HiPIMS process. In this study, TiN thin films exhibiting high hardness and low friction coefficient were deposited using a unipolar mode in HiPIMS. The Ti target used has a purity of 99.99%. Nitrogen was used as the reactive gas to deposit TiN along with Ar gas. The effect of duty cycle on the deposition of TiN film was investigated in this study by varying the duty cycle from 5 to 50%. The cycle time of 100, 500, 1000, 5000, 10000 μs were also studied. Besides, TN thin film was also deposited by conventional dc magnetron sputtering (dcMS) for comparison. During the deposition, target voltage and current were recorded while the ions and neutrons in the plasma were diagnosed by optical emission spectroscopy, OES (EMICON). Thickness of the obtained TiN films was measured using scanning electron microscopy (SEM, JEOL-JSM 7000F ). The surface morphology and surface roughness were investigated by atomic force microscopy (AFM, Veeco-DI 3100). Compositions were analyzed using Auger Electron Spectroscopy (AES, MICROLAB 350). Crystallinity and microstructures were investigated using grazing incidence X-ray diffractometry (GIXRD, PANalytical-X'Pert PRO MRD). The hardness and elastic modulus were investigated using nanoindenter (Nano Hardness Tester, CSM) equipped with a Berkovich 142.3° diamond probe tip at a maximum applying load of 2400 μN. The wear behavior was investigated using a ball-on-disk tribometer (CSM Instruments Inc.).
BP40 Development of Uniform Coating Technique of Tetrahedral Amorphous-Carbon Film by T-shape Filtered-Arc-Deposition with Deflected Plasma beam and Multi-Motion Substrate Holder for Semispherical Object
Hideto Tanoue, Hiroshi Okuda, Yoshiyuki Suda, Hirofumi Takikawa (Toyohashi University of Technology, Japan); Masao Kamiya (Itoh Optical Industrial Co., Ltd., Japan); Makoto Taki, Yushi Hasegawwa, Nobuhiro Tsuji (Onward Ceramic Coating Co., Ltd., Japan)

Tetrahedral amorphous-carbon (ta-C) is hydrogen-free and high-density diamond-like carbon (DLC) film. In particular, chemical inertness, since it is able to prevent the adhesion of glass at high temperature and, focused as a protective film of glass lens mold. A Vacuum arc deposition, DLC is able to produce commercially, including ta-C. On the other hand, the vacuum arc plasma has a problem that the cathode emits a plenty of macrodroplets as well as ions and electrons. The macrodroplets deteriorates the film properties; uniformity, surface roughness, friction coefficient, hardness, etc. In order to overcome this droplet problem, the filtered arc method has been developed to remove the droplet from the plasma, as the most powerful method. However, the droplets emitted from the graphite cathode are in solid phase so that the conventional filtered arc system is hard to filter them. The one of authors has been developed the T-shape filtered arc deposition (T-FAD) system, in which the droplets are separated from the plasma at the 90 degree bent position. Though, the ta-C preparation to semi-spherical object was difficult by T-FAD until now. In this study, new preparation technique by T-shaped filtered-arc deposition (T-FAD) system has been developed for ta-C preparing to semi-spherical object.

First, number of droplets was reduced for capable large-aperture lens. A few droplets were attached film that prepared by T-FAD. Droplets were crash the duct wall, it was reflection and exploding, and it was flied to the substrate. Therefore, substrate position was set in the line of sight non-visible from the duct wall by controlling the plasma beam deflection. As a result, it was improved removing droplets performance. Plasma beam was deflected at about 15° upward from the horizontal line of duct exit, number of droplets was one-third.

Second, plasma beam was irradiated on normal axis of the substrate for uniform film thickness. So, we developed a multi-motion substrate holder which is able to move in direction of vertically and rotatory. Ta-C was coated to object simulated semi-spherical object, the film thickness distribution was confirmed. So, α is the angle between the normal axis of object and plasma beam center line. α is 0° (downward of object) and 40° (upward of object). A swing motion pattern in the vertical direction was programmed under the distribution of film thickness. As a result, uniform thickness ta-C film was coated on polished semi-sphere object in this condition, a uniform coating of the semi-sphere object was realized.

BP41 Optical Emission Spectroscopy of Cr-Al-C Arc Ion Plating Plasma
Tetsuya Takahashi, Rainer Cremer, Peter Jaschinski (KCS Europe GmbH, Germany)

A ternary transition metal carbide of Cr2AlC, also referred to as MAX-phase, is known to exhibit both the properties of metals and ceramics, providing high stiffness, high hardness, high oxidation resistance, thermal-shock resistance, and machinability. Due to the unique mechanical and chemical properties, Cr2AlC is a promising candidate for protective hard coatings on tools or components operated in severe mechanical and thermal load conditions.

We explore the depositions of phase pure Cr2AlC by an industrial arc ion plating. The phase and microstructural evolution of the growing films are known to be affected by the plasma properties, and hence the understanding thereof is of significance for the process optimization. This study analyzes the Cr-Al-C arc ion plating plasma using Optical Emission Spectroscopy (OES) towards contributing the Cr2AlC deposition. In the Cr-Al-C arc ion plating plasma ignited, OES peaks associated with Cr-neutral, Cr-ions, and Al-neutrals were identified whereas those of C were not detected in the present study. The relative intensity of Al to Cr neutral is found to be affected by the Ar gas pressure. Also, the relative intensity of Cr-ions to Cr-neutral decreases with increasing the working Ar gas pressure, which could be explained in terms of the charge-exchange collision processes.
BP42 Growth of Boron Nitride with a High Temperature Chemical Vapor Deposition (HTCVD) Reactor using BCl3 and NH3 as Precursors
Nicolas Coudurier, Raphaël Boichot (Grenoble INP, France); Elisabeth Blanquet, Michel Pons (CNRS, France)
Boron Nitride (BN) with its various properties like high thermal conductivity, high chemical and thermal stability, a wide optical bandgap and a high electrical resistivity is a potential material for optoelectronic, piezoelectric sensors and high power electronics applications. Many different polytypes of BN exist. Previous studies report the difficulty to obtain other phase than the poorly crystallized graphite-like turbostratic phase (t-BN). Cubic BN (c-BN) phase was however obtained with plasma aided CVD processes. Recent attempts to obtain epitaxial layers of hexagonal (h-BN or r-BN) have succeeded with triethyl boron [1] and diborane [2] as boron source and NH3 as nitrogen source. This phase is expected to be the most promising material after diamond for optoelectronic.

Growth of BN at high temperature (1500-1800°C) on various substrates (lab-made AlN templates on c-sapphire and c-sapphire alone) in a cold wall HTCVD reactor has been studied using NH3 and BCl3 as nitrogen and boron sources, and H2 as carrier gas. The experiment set-up consists of a vertical water-cooled quartz reactor with a graphite susceptor covered with AlN and heated by induction. Temperature of the substrate, N/B ratio in the gas phase and reactor pressure influence on the growth layer has been investigated. As-grown BN layers have been characterized by Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectroscopy.

The study shows that the t-BN phase is systematically obtained at high growth rates as expected, whatever the temperature in the range investigated. To stabilize the h-BN growth on hetero substrate, a very low partial pressure of BCl3 should be used, leading to very low growth rates.

[1] M. Chubarov, H. Pedersen, H. Högberg, V. Darakchieva, J. Jensen, P.O.Å. Persson, A. Henry, Phys. Status Solidi RRL 5 (2011) 397.

[2] G. Younes, G. Ferro, M. Soueidan, A. Brioude, V. Soulière, F. Cauwet, Thin Solid Films 520 (2012) 2424.

BP43 Novel TiAlN Nanostructured CVD Coatings with Superior Oxidation Resistance
Jozef Keckes, Rostislav Daniel, Velislava Terziyska, Christian Mitterer (Montanuniversität Leoben, Austria); Arno Köpf, Ronald Weißenbacher, Reinhold Pitonak (Böhlerit GmbH, Kapfenberg, Austria)

In this contribution, microstructure and properties of Ti1-xAlxN coatings with x > 0.9 prepared using moderate temperature chemical vapour deposition are described. The coatings characterization was performed by X-ray diffraction and transmission electron microscopy techniques. The coatings consisting of fcc-Ti1-xAlxN, fcc-TiN and hexagonal AlN phases exhibit a special nanolamellar microstructure and an extraordinary high oxidation resistance up to 1.100 °C (air / 1h), which is considerably higher than it is known for Ti1-xAlxN- and even Cr1‑xAlxN grown by physical vapour deposition techniques.

BP44 Silicon Carbide Interlayers for HFCVD Diamond on Cemented Carbide Cutting Tools
Ulrike Heckman (Fraunhofer Institute for Surface Engineering and Thin Films, Germany); Antje Hagemann (Fraunhofer Institute for Surface Engineering and Thin Films IST, Germany); JavierA. Oyanedel Fuentes (Institute for Machine Tools and Factory Management (IWF), TU Berlin, Germany); Jan Gäbler, Markus Höfer (Fraunhofer Institute for Surface Engineering and Thin Films IST, Germany); Fiona Sammler (Institute for Machine Tools and Factory Management (IWF), TU Berlin, Germany); Lothar Schäfer (Fraunhofer Institute for Surface Engineering and Thin Films IST, Germany); Eckart Uhlmann (Institute for Machine Tools and Factory Management (IWF), TU Berlin, Germany)

The performance and tool lifetime of cemented carbide tools (WC:Co) can be significantly improved by chemical vapor deposited thin film diamond (CVD diamond). As the cobalt binder of the cemented carbides leads to graphitization during diamond deposition, the tools are usually pretreated by chemical etching procedures which remove the cobalt binder from the boundary zone of the tool substrate. This pretreatment may have a detrimental effect on the mechanical integrity of the tool and is highly time-consuming and costly.

A promising method to achieve good adhesion of diamond films on cemented carbides is to deposit a carbide interlayer, such as silicon carbide. This interlayer acts as a diffusion barrier and thereby protects the diamond film against the cobalt binder phase. The interlayer strategy is not only beneficial for the properties of the layer system but also reduces costs and time effort during tool coating. Furthermore, these interlayers enable to deposit diamond on cemented carbides with higher cobalt content than the conventional 6 to 10 wt-%.

Investigations on hot-filament activated chemical vapor deposited (HFCVD) SiC/diamond systems were performed without chemical etching of the cemented carbide tools with Co content of 6‑13 wt-%.

Tetramethylsilane (TMS) was used as a precursor gas which delivers both silicon and carbon species. Diamond and silicon carbide were deposited in separate coating processes (ex-situ). An in-situ deposition of both silicon carbide and diamond coating in the same batch will be developed by performing experiments on optimization of the SiC coating and on diamond in‑situ nucleation.

The performance of the tools coated with SiC interlayers and CVD diamond was tested in cutting tests as well as in model wear tests. The turning tests on the workpiece material AlSi17Cu4Mg, with regard to the tool life and wear form, were conducted without any coolant. The results of the experiments were compared with conventional CVD diamond tools. Additionally, the wear mechanisms adhesion, abrasion and surface fatigue of the innovative coating systems were investigated in model wear experiments.

BP45 Role of the Si-addition on the Mechanical and Tribological Properties of AlCrN-based Films Deposited by Cathodic Arc Deposition
Alain Billard (IRTES-LERMPS-UTBM, France); Fernando Lomello (DEN/DANS/DPC/SEARS/LISL CEA, France); Frédéric Sanchette (ICT, France); Frédéric Schuster, Michel Tabarant (CEA, France)

The study was focused on the development of AlCrN hard layers for high speed machining applications since during the last years, it was proved that commercially available coatings present high abrasion and oxidation resistance over 800°C, thus increasing the tool lifetimes. Recently, the addition of alloying elements such as silicon, tungsten and boron are believed to be suitable for enhancing the oxidation resistance at high temperatures, as reviewed by many authors [1, 2].

In this study nitride-based coatings have been deposited by vacuum cathodic arc deposition (CAD). This technique has been chosen due to its versatility, allowing easily the industrial up-scaling.

The results were discussed taking into account the role played by the stratification and the silicon and oxygen content in AlCrN coatings. It is believed that surface and bulk oxides are sufficiently plastic to sustain abrasive wear at high temperatures without spalling effects [3]. Moreover, they are supposed to increase the wear resistance as they reduce the friction coefficients [4].

Microstructures and morphology of the deposited coatings, before and after tests, have been investigated by means of X-ray diffraction, scanning electron (SEM) and transmission electron (TEM) microscopy observations. However, in order to determine the dispersion of oxides and silicon nitrides inside the microstructure, the glow discharge optical emission spectroscopy (GDOES) was employed.

Finally, samples were subjected to mechanical (nanoindentation) and tribological characterization (up to 800°C) with the aim of correlating the microstructures to the mechanical behaviour.

BP46 Influence of RF and Plasma Parameters on Film Properties for Layer Transfer by an Advanced PECVD Process Control Method
Tobias Grotjahn (Fraunhofer IWM, Germany); Ralf Rothe (Plasmetrex GmbH, Germany); Sven Meier (Fraunhofer IWM, Germany)
For layer property optimization and transfer of PECVD deposited diamond-like-carbon (DLC) coatings usually the very time consuming "trial-and-error"-method is used. To improve the layer transferability it is necessary to develop a better understanding of the RF-network, the plasma state and the interaction between the plasma and the substrate surface. For this reason several diagnostic methods were used to investigate the influence of RF and plasma parameters on film properties according to the load condition of the chamber at different generator powers and gas fluxes. The matching network was equipped with several additional calibrated RF-sensors. Additionally, the non-invasive diagnostic methods of Nonlinear-Extended-Electron-Dynamics and Optical Emission Spectroscopy were used to monitor the plasma state. Through these techniques the plasma resistivity, the collision rate, the gas temperature and, by means of the actinometrical approach, the electron temperature and particle densities of emitting species may be determined. To obtain a time-resolved overview of all of these parameters a monitoring system, which connects all of these parameters, was developed. In addition, mechanical layer properties such as hardness, young’s modulus and tribological behavior were measured. This work investigates the correlations between all of the outlined parameters and properties and illustrates how they are used to design a process control technique which transfers reliably established layer properties directly to different substrate sizes or to another devices.
BP47 Arc evaporated coatings for machining application
Daniel Schlegel (ESTA, France); Mohammad Arab Pour Yazdi (IRTES-LERMPS-UTBM, France); Fernando Lomello (DEN/DANS/DPC/SEARS/LISL CEA, France); Frédéric Sanchette (ICT, France); Alain Billard (IRTES-LERMPS-UTBM, France); Frédéric Schuster (CEA, France)

Arc evaporation is a powerful process for the deposition of very hard nitride coatings due to the high ionization rate of the discharge which allows a tuneable control of the impinging species energy. In particular, this technique is suitable to improve machining efficiency of carbide tools. Both mono- and nano-layer coatings based on Al, Ti and Cr nitrides have already been involved to coat machining tools.

In this paper, we first describe the industrial prototype used for the deposition of nitride single or nanolayer coatings. This device allows the deposition of nano-layer coatings with periods if about 5 to 50 nm by controlling the rotation speed of the triple-rotation substrate holder.

The structural, mechanical and tribological characteristics of different nitride coatings such as (Al,Cr)N, (Al,Ti)N monolayers and TiN-CrN, (Al,Ti)N-TiN, (Al,Cr)N-CrN nano-layers are then presented in relation with the coatings their deposition.

Finally, instrumented machining tests are performed using carbide tools coated with those different coatings to compare their ability to high speed machine several hard materials.

BP48 Structure and Properties of CrN/TiN Multilayer Coatings Deposited by Modulated Pulsed Power and Pulsed dc Magnetron Sputtering
Yixiang Ou, Jianliang Lin (Colorado School of Mines, US); Isaac Dahan (Ben Gurion University of the Negev, Israel); Bo Wang, John Moore (Colorado School of Mines, US); William Sproul (Reactive Sputtering, Inc., US); Mingkai Lei (Dalian University of Technology, China)

CrN/TiN multilayer coatings with different bilayer periods (l)were synthesized by using the combination of modulated pulsed power magnetron sputtering (MPPMS) and pulsed dc magnetron sputtering (PDCMS) in a close field unbalanced magnetron sputtering system. The structure and properties of the coatings were investigated by means of X-ray diffraction, transmission electron microscopy, nanoindentation and ball-on-disc wear test. The corrosion resistance of the coatings was evaluated by anodic polarization measurement in 3.5 wt% NaCl aqueous solution. The coatings showed face centered cubic nanolayered structure. Although no oriented TiN or CrN layer were prepared as an adhesion layer prior to the coating depositions, the coatings with relatively large l (e.g. 8.9 nm and 13.5 nm) exhibited a dominated (111) texture, while the coatings with relatively small l (e.g. 4.7 nm and 2.2 nm) exhibited a strong (200) peak. With a decrease in the l from 13.5 to 2.2 nm, the hardness and the elastic modulus of the coatings increased and achieved the highest values of 22.8 GPa and 276 GPa at a l of 2.2 nm, respectively. The anodic polarization curves of CrN/TiN multilayer coatings in a 3.5 wt% NaCl aqueous solution showed excellent pitting corrosion resistance with an increase in corrosion potential and a decrease in passive current as compared with untreated AISI 304L substrate.

Key words: CrN/TiN; Modulated pulsed power (MPP); High power pulsed magnetron sputtering (HPPMS); Pulsed dc magnetron sputtering (PMS); Multilayer coatings; Corrosion

BP49 Hardness and Structure Evolution of Annealed Zr-TiAlN Films
Robert Pilemalm (Linköping University, Sweden)

TiAlN has been used as an effective protective coating for cutting tools since the 1980’s. Recently and triggered by the demands for improved high temperature protection, research on different alloying concepts have been explored, e.g. Cr-TiAlN and Y-TiAlN. Some of these alloy compositions have shown improved high temperature properties and better cutting performance. Here we build on this concept and explore the Zr-TiAlN system and to systematically investigate how Zr-additions to TiAlN affects thermal stability and hardness. The background for choosing Zr as the alloying element is ab initio calculations of the Gibb’s free energy of mixing that points out the possibility to tailor the driving force for spinodal decomposition though Zr-additions.

For this study we have used Ti50Al50N as the reference material and then added Zr resulting in the following compositions: Ti0.44Al0.40Zr0.17N, Ti0.25Al0.24Zr0.51N, Ti0.09Al0.07Zr0.84N, and Ti0.04Al0.04Zr0.92N. The coatings were deposited on hard metal (WC-Co) substrates with cathodic arc evaporation. After deposition the coatings were isothermally annealed for two hours at 800°C, 900°C, 1000°C and 1100°C respectively.

X-ray diffractometry shows that Ti0.44Al0.40Zr0.17N decomposes isostructurally into cubic (c)-TiZrN and c-AlN, which is consistent with theoretical predictions. It also shows the unstable nature of this composition resulting in a driving force for spinodal decomposition. As a consequence of the decomposition age hardening occurs at 800°C. In contrast, for high additions of Zr, i.e. Ti0.09Al0.07Zr0.84N and Ti0.04Al0.04Zr0.92N, no decomposition occurs at the investigated temperatures. Instead the alloys remained in their original cubic state after annealing. This result is also in agreement with the theoretical predictions, which indicate a very weak driving force for decomposition for these compositions. Instead the heat treatments resulted in an annihilation of the lattice defects present from the deposition and a significant drop in hardness already after 900°C of annealing.

In summary we conclude that alloying TiAlN with Zr opens new avenues for control of the driving forces for spinodal decomposition such that the high temperature properties can be tuned.
BP50 Synthesis of the CrZrSiN Thin Films and its High Temperature Tribological Properties
DongJun Kim, JoungHyun La, SungMin Kim, SangYul Lee (Korea Aerospace University, Republic of Korea)
Recently, challenges to meet the ever increasing requirements to cover severe working conditions for thin films, multi-compositional films with more than 3 elements could be one of the excellent solutions. Using segment or mosaic targets to synthesize multi-compositional films could be a simple way to produce these thin films with multi compositions. In this work, three different segment targets were used to synthesize the CrZrSiN coatings with various Si contents on the Si wafer substrate and H13 tool steel using unbalanced magnetron sputtering process. Tribological properties of coatings as a function of the Si content were investigated by ball-on-disk type wear tester at room temperature and 500℃. After wear test, various tribological characteristics such as surface morphology, wear rate and wear debris were examined by atomic force microscopy (AFM), field emission scanning electron microscope (FE-SEM) and Raman Spectroscopy. Our results showed that tribological properties of CrZrSiN films at high temperature were increased significantly, compared with those of CrZrN coatings. Si content in the thin films has strong influence on the improvement of the high temperature tribological performance of the films. At the room temperature, however CrZrSiN films and CrZrN films showed similar tribological performance. Detailed experimental results will be presented.
BP51 Improvement of Wear Resistance of Nitrile Rubber Surfaces by Hydrocarbon Plasma Treatments
Raquel dos Santos, Emanuel Santos Jr., Sergio Camargo Jr. (Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.)
Nitrile rubbers (NRB) are widely employed in engineering as mechanical seals, for instance. However, they usually exhibit high coefficient of friction (COF) when sliding against hard counterparts. Besides to that, the presence of severe wear limits their service lifetime. So, plasma surface treatment may be considered to enhance the NBR tribological performance. In this work the wear behavior of NBR surfaces modified by radio frequency (rf) hydrocarbon plasma treatment is investigated. Surface treatment was carried out using methane (CH4) and acetylene (C2H2) as precursor gases at 0.05 torr working pressure and -50 and -100 V self-bias voltages (bias voltages in excess of -100V damaged the sample surface). The surface morphologies were observed by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), while the physicochemical characterizations were carried out by Raman scattering and Fourier transform infrared (FTIR) spectroscopy. The CH4 plasma did not seem to affect much the NBR surface morphology when compared to the untreated samples, as the elastomer matrix and the particulate phase present in the bare samples are still clearly observed. On the other hand, NBR samples treated in C2H2 plasma present completely different surface morphologies and seem to be covered by a film of rough appearance. In this case EDS analysis shows an almost pure carbon surface showing the presence of a thick film. FTIR and Raman spectra of CH4 plasma treated samples are also very similar to bare NBR, while C2H2 treated ones present only a broad Raman peak characteristic of DLC films centered around 1525 cm-1. Wear tests were performed by pin-on-plate technique using a CETR-UMT tribometer. A stainless steel ball (1/4” diameter) was employed as the counter-pin. All tests were carried out at room temperature using to the following parameters: 0.5 N load, 2.0 and 5.0 mm wear radii, 0.05 and 0.20 m/s linear velocities. Wear was basically evaluated in terms of mass (volume) loss. In general, all surface treatments were effective to enhance the wear resistance of NBR samples, regardless the deposition conditions. Further, a noticeable COF reduction of up to about 70% was found in relation to the bare samples, from 0.5 to 0.15. For samples treated with CH4 plasma, the wear rates were surprisingly decreased of about 70-85%, while in case of C2H2 treated samples wear was reduced by up to about 60%. In conclusion, hydrocarbon plasma treatment can be effectively employed on nitrile rubber. The effect of plasma treatment seems to deposit a film with structure similar to DLC carbon, resulting in great improvement of NBR tribological performance.
BP53 Preparation and Characterization of Ti-Al-N Thin Films Deposited by Reactive Crossed Beam Pulsed Laser Deposition
Luis Escobar-Alarcon (Instituto Nacional de Investigaciones Nucleares de Mexico, Mexico); Dora Solis-Casados (Universidad Autonoma del Estado de Mexico, Mexico); Saul Romero, Jonatan Perez-Alvarez (Instituto Nacional de Investigaciones Nucleares de Mexico, Mexico); Giovanni Ramirez (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México); Sandra Rodil (Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de Mexico, México, Mexico)
Ti-Al-N thin films were deposited on stainless steel substrates using the reactive crossed beam pulsed laser deposition technique. The Al content in the films was varied in a controlled way by changing the ablation conditions on the Al target, particularly the Al+ mean kinetic energy. The aluminum ion mean kinetic energy was varied from 46 to 423 eV, resulting in Ti-Al-N films with Al contents from 5.4 up to 39.0 at. %, suggesting the aluminum content can be controlled by the Al+ kinetic energy. The characterization of the mechanical properties showed that the hardness increased from 18.0 to 26.0 GPa as the Al+ mean kinetic energy was increased. Raman Spectroscopy was used to characterize the microstructure of the deposits, and the obtained results revealed the development of different local microstructures as a function of the Al+ kinetic energy. The corrosion resistance of deposited films was evaluated using two different electrochemical techniques: DC polarization and electrochemical impedance spectroscopy. The results showed a good improvement of the corrosion resistance in comparison to both the bare substrate and the titanium nitride coating without aluminum. The obtained results reveal that it was possible to design coatings with good corrosion resistance and high hardness.
BP54 Characterization of Diamond-like Carbon Film Synthesized by HIPIMS System for Medical Application
Ming-Huei Shih, Wei-Chih Chen, Chi-Lung Chang, Da-Yung Wang (MingDao University, Taiwan, Republic of China)

The diamond-like carbon (DLC) film has been widely used for molds and components protection in automotive and aerospace industries with its high hardness, low friction coefficient, high wear resistance, and chemical inertness. For medical applications such as the protective coating for artificial implants, typical DLC films are suffered by concentrated corrosion at pin holes and associated corrosion cracking which leads to the premature implant failure. In this study, the improved DLC film was synthesized by using the high power impulse magnetron sputtering (HIPIMS) technology to assess the feasibility of producing a pin-hole-free, low internal stress, and chemically stable DLC coating by the characteristic HIPIMS high energy plasma impingement during the coating process. The HIPIMS deposited DLC coatings were characterized for structural integrity and tribological behaviors. Additional in-vitro test, which emulates the actual bio-chemical and mechanical conditions, will be conducted.

Keywords: High Power Impulse Magnetron Sputtering (HIPIMS), wear, DLC, medical
BP55 Design and Fabrication of Bilayer Wire Grid Polarizers (B-WGPs) with Sub-wavelength Metal Gratings
JinJoo Kim, TaeYoung Kim, WonYoung Kim, BongHye Ku, Peranantham Pazhanisami, ChangKwon Hwangbo (Inha University, Republic of Korea)
Wire grid polarizers (WGPs) are very essential optical components because of low cost, compactness, and high polarization efficiency than typical polarizers. Also they are compatible with an integrated circuit fabrication in nano photonics. The WGPs for visible and near infrared wavelength region require fabrications of sub-wavelength metal gratings. Recently, in order to achieve high performance polarizer, bilayer metal WGPs (B-WGPs) have considered as new type of polarizer composed of two sub-wavelength metal gratings separated by a certain distance. In the B-WGP, the s-polarized light is reflected, and the p-polarized light is transmitted. To fabricate WGPs with sub-wavelength gratings, the nanoimprinting lithography is attracting attention. In this study, we have designed and fabricated bilayer wire grid polarizers with sub-wavelength aluminum gratings using ultra-violet (UV) curing nanoimprinting method and physical vapor deposition. An Al metal B-WGPs was fabricated on two type transparent substrates with different size. The substrates with 120 nm period and 100 nm height are applied for visible wavelength region. The substrates with 450 nm period and 150 nm height structure are available for near infrared wavelength applications. We have employed the finite difference time domain (FDTD) method to analyze optical performance of B-WGPs as metal thickness and to calculate the field distribution in the B-WGPs. The experimental results reveal that TM transmittance is above 50 % and also the polarization extinction ratio (PER) between TM and TE wave are respectively up to 100 in visible and above 250 in near infrared region. For high quality B-WGPs, these values are not enough to reach to simulation results above 1000, however, we are improving our skills to increase them more. Thus, it is expected that the B-WGP with sub-wavelength metal gratings by using nanoimprinting is good candidate as a high performance polarizer for a variety of applications.
BP56 Alumina Coatings for use under High Radiation Conditions
Farzana Majid, Saira Riaz, Shahzad Naseem (University of the Punjab, Pakistan); Ishaq Ahmad, Ghulam Husnain (National Centre of Physics, Pakistan)

Alumina (Al2O3) is being studied as a radiation resistant coating for various applications. The surface modification and irradiation effects on aluminum alloy 7407 after coating with alumina (Al2O3) was carried out using electrochemical and sol–gel method. Alumina coatings, synthesized by a sol–gel route, were deposited on Al7407 substrates by spin coating. Other series of samples were prepared electrochemically by varying DC voltage in the range 1 – 5 volts. Coatings are optimized by controlling various deposition parameters. For comparison purposes RF Magnetron sputtering technique is also used. The various characterization results indicate that relatively smooth coatings can be achieved by simple and scalable techniques such as electrodeposition and sol-gel. Coated substrates were then irradiated with Ni+, H+ and Ar+ ion beams by using Pelletron accelerator at several KeV to a few MeV. The nature and fluency of ions was varied to correlate to different environments. The surface modifications and structure of the coated surfaces before and after ion beam irradiations were characterized by FTIR, XRD, SEM, AFM and XRD, whilst the mechanical properties of modified surfaces were determined using nano-indentation. The results showed that the alumina xerogel films coated on the Al7407 substrates are successfully converted into crystalline alumina ceramic coatings by ion beam irradiations. Electrodeposited alumina films also show recovery and improved crystalline structure after ion beam exposure. Structure of resulting coatings is observed to be strongly depending on the ion beam types and dose conditions. By increasing dose intensity of Ar+ and Ni+ ion beams, γ-Al2O3 was observed which transformed to α-Al2O3 at higher energy. Nano-indentation results reveal that significant improvement in hardness and Young's modulus of the alumina -coated surface at optimized conditions can be achieved even after recovery from irradiations.

BP57 A Detailed Investigation into the Preparation and Properties of ZrO2- Fe2O3 Coatings for Bio-Medical Applications
Saira Riaz, Shahzad Naseem (University of the Punjab, Pakistan)

Tetragonal zirconia (ZrO2) ceramics find a useful application in human dentures for reconstruction and filling purposes because of their unusual combination of strength, fracture toughness, hardness, and low thermal conductivity. These attractive characteristics are largely associated with the stabilization of tetragonal phase through alloying with aliovalent ions. The high fracture toughness exhibited by many of zirconia ceramics is attributed to the tetragonal to monoclinic phase transformation and its release during crack propagation. However, tetragonal phase of zirconia is not stable at room temperature. A number of ways are being sought, and we are investigating Fe2O3 addition in ZrO2 for stabilization purposes. RF magnetron sputtering and Sol-Gel techniques have been used for preparation of the coatings, whereas XRD, SEM/EDX, AFM and IS techniques are used for characterization purposes. The optimized conditions are shown to lead to a stable tetragonal phase of ZrO2 at room temperature. In sol-gel synthesis temperature, pH, nature of solvent and synthesis conditions played critical role in the size reduction and stabilization of zirconia at room temperature . ZrO2 and Fe2O3 targets were used to prepare coatings by RF sputtering. Layer by layer growth of ZrO2 and Fe2O3 was optimized for the preparation of stable zirconia coatings. Post annealing was done to investigate the alloys conditions and properties. X-ray diffraction (XRD) results show formation of tetragonal phase at 300oC when sample was heated for 60 minutes. Coatings, prepared by sol gel, at 500oC exhibit crystallite size as low as 11 nm as revealed by XRD results, whereas grain size ~30 nm was observed by scanning electron microscopy (SEM). Vickers Hardness measurements showed ~564 HV hardness of ZrO2 samples prepared by sol-gel. Thus, sol-gel has proven to be a low cost, reliable and application oriented technique for the preparation of ZrO2 coatings.

BP58 Preparation and Characterization of CIGAS Thin Films and Their Solar Cells
Shahzad Naseem, Saira Riaz (University of the Punjab, Pakistan)

Thin films of copper indium gallium aluminum selenide Cu(In,Ga,Al)Se2 (CIGAS) are prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation. These films were concurrently studied for their structural properties by X-ray diffraction (XRD) technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time. It is also seen that the compound formation starts at 250oC, with ternary phases appearing at 350oC or above. Whereas, there is another phase shift, at 450oC, with preference to the quaternary and / or pentenary compound. CdS is used as a window layer for the solar cell fabrication, whilst zinc-aluminate has been used as transparent conducting layer. The current-voltage results, at various illumination levels, are used to calculate the internal and external parameters of these solar cells; the internal parameters being obtained by a simple one-diode fitting of the experimental data. A maximum efficiency of around 9% is reported with a poor fill factor of 60%. Analytical calculations have also been performed and the analytical results point out towards loss of fill factor due to high series resistance.

BP59 Effect of Droplet Inclusion in Arc-evaporated Multilayer Coatings on the Anisotropy of Thermal Conductivity
Michael Böttger (ETH Zurich, Department of Materials, Switzerland); Andrey Gussarov (ENISE, France); Valery Shklover (ETH Zurich, Department of Materials, Switzerland); Jörg Patscheider (Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland); Matthias Sobiech (OC Oerlikon Balzers AG, Liechtenstein)
Thermal conductivity (TC) and its anisotropy is one of the coating properties that can be adjusted by appropriate multilayer structuring and thus has received recently great attention in the context of application of TC-designed hard coatings for machining of difficult-to-cut materials like Ni- and Ti-based superalloys. Cathodic arc evaporation is a standard technology to synthesize multilayer coatings for wear resistant applications. However, arc-evaporated hard coatings typically contain droplets of different sizes which are generated during evaporation of the target material. These droplets may have a big influence on the thermal conductivity in multilayers, especially if they are larger in size than the bilayer thickness In this study it is presented how the inclusion of metallic droplets of different material, size, volume fraction and shape can affect the anisotropy of thermal conductivity in a multilayer coating system.
We use the Maxwell Garnett Approximation (MGA) for the description of isotropic inclusions in an anisotropic matrix. Its applicability is evaluated by comparison with a 2D finite element method (FEM) simulation of a prototypical multilayer coating. The MGA model agrees well with FEM simulation in predicting independence of thermal conductivity anisotropy of droplet material and size, only depending on the volume fraction for spherical droplets. In the case of elliptical droplet shapes the inclusion of such droplets can be beneficial or detrimental regarding TC anisotropy depending on droplet material, excentricity of the droplets and their orientation with respect to the multilayer coating structure.

BP60 Structural, Electrical Conductivity and Mechanical Properties of TiNx Thin Films
Johannes Goupy (CEA Grenoble, France); Philippe Djemia (LSPM-CNRS, Université Paris 13, Sorbonne Paris-Cité, France); Stephanie Pouget (CEA Grenoble, France); Laurent Belliard (UPMC-Institut des NanoSciences de Paris, France); Grégory Abadias (Institut P' - Universite de Poitiers, France); JeanClaude Villégier (CEA Grenoble, France); JeanLouis Sauvageot, Claude Pigot (CEA Saclay, France)
For thermal applications, we need to manufacture Titanium Nitride film with as high as possible Critical temperature while minimizing the mechanical constraint. We thus tried different physical conditions during realization and characterized the films obtained. We also studied the influence of the substrate onto these films. We investigated the structural and mechanical properties of titanium nitride thin films TiNx with 0.385 ≤ x ≤ 1.13 deposited in a temperature range [320 K, 400 K], at 800 W, by reactive DC magnetron sputtering deposition from a Ti target in Ar + N2 plasma discharge. The Ar working pressure was fixed at 0.2 Pa and the nitrogen concentration, x, modified by increasing the N2 flow from 4.2 to 15 sccm. The Ar flow was set at 60 sccm. The chemical analysis was performed with the Rutherford backscattering (RBS) and nuclear reaction analysis (NRA) techniques. The structural properties of the films were characterized by X-ray Diffraction (XRD) and X-ray reflectivity (XRR), the electrical conductivity by the four-point probe method, whereas the picosecond ultrasonics and Brillouin light scattering techniques were employed to measure their acoustic and elastic properties as function of the nitrogen concentration.
BP61 Tribological and Electrochemical Properties of HVOF Sprayed CrC-40NiCr and WC-40NiCr Coatings
Peter Olubambi, Zanele Masuku, Babatunde Obadele, Tumisang Rapoo (Tshwane University of Technology, South Africa)

CrC–NiCr coatings have been extensively employed in high temperature applications and automotive industries to improve high temperature corrosion resistance of component surfaces, improve their wear resistances and decrease the friction coefficient between varying sliding parts. With the recent technological advancement in the mining industries and the need to develop improved materials for the varying harsh mine environments, the need to investigate the tribological and corrosion behaviour of these coatings in both dry and wet environments, typical of mine conditions is very imperative. The present study described and compared the corrosion and tribological properties of HVOF sprayed coatings from two types of CrC-40NiCr feedstock powders and WC-40NiCr powders. Reciprocating sliding wear test was performed using the CETR UMT-2 test system under a load of 25 N and sliding velocity of 0.4 mm/s for 1000 seconds while wet abrasion test using the same wear parameters as well as electrochemical behaviour of the coatings were carried out in synthetic mine water environments. The morphology and microstructures present from the as sprayed, polished cross-section, wear and corroded coatings were examined using FE-SEM while the different phases present where analysed by XRD. The microhardness value was obtained using Vickers microhardness tester at a load of 100g. Hardness value obtained from the WC-NiCr coating is significantly higher than that of CrC-40NiCr. Results obtained from wear analysis showed that WC-NiCr coated steel substrate gave a higher wear depth of 0.93 mm when compared to CrC-NiCr 0.7 mm and this could be attributed to the presence of WC in the coating and also the use of WC ball which is a harder phase carbide than CrC. From the corrosion results, there is no much significant difference in the Ecorr and Icorr observed. However, CrC-NiCr coatings showed more corrosion resistant with a negative shift in Icorr.

BP62 TiCrN/NiMnSb Thin Film Heterostructures for Vibration Damping in MEMS
Nitin Choudhary, Davinder Kaur (Indian Institute of Technology Roorkee, India)

The present study explored the in-situ deposition of TiCrN/NiMnSb thin film heterostructures using magnetron sputtering. Room temperature nanoindentation was performed to obtain the mechanical and damping properties of these heterostructures and results were compared with pure NiMnSb films. A significant improvement in the hardness and elastic modulus was observed in TiCrN/NiMnSb films, which is due to the presence of superhard TiCrN thin layer. Creep and Impact test performed using berkovich and spherical indenter revealed better damping in surface modified NiMnSb ferromagnetic shape memory alloy (FSMA) thin films. The improved damping in surface modified FSMA was attributed to the good adhesion and strong combination of TiCrN and NiMnSb damping layers. The novel TiCrN/NiMnSb heterostructure with enhanced mechanical and damping properties would be a potential material for vibraton damping applications in MEMS.

BP63 Characterization of a Cylindrical Planar Hollow Cathode and it's use for the Preparation of Bi Nanoparticles
Stephen Muhl (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico); Argelia Perez (Universidad Nacional Autonoma de Mexico, Mexico); Andres Tenorio (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico)

Hollow cathodes are widely used for a variety of applications from intense light sources to for thin film deposition. The particular characteristics of the hollow cathode are that the geometry reduces the loss of electrons by the oscillative motion them between the sheaths on each side of the cathode, with this resulting in the production of high density plasmas. Sputtered atoms from the cathode normally travel from one wall to the other but can be carried toward the substrate through the use of a high gas Ar flow and this can be used to control the deposition rate. It has also been reported that under high pressure operation, the high density plasma can be used to generate nanoparticles in the gas phase; diameters in the range of 10-50 nm. We have developed a new version of the traditional hollow cathode based on the cylindrical planar design. The geometry is similar to a toroidal electrode which is open at the interior surface. In this way the “hollow” discharge occurs between the upper and lower electrode surfaces and the only way that electrons can leave the discharge is via the upper or lower apertures. We have studied the electrical characteristics of the discharge as a function of the applied electrical power and gas pressure, and we have used the system to deposit thin films as a function of the plasma power and gas flow. This hollow cathode was also successfully used to deposit thin films of nanoparticules of bismuth. By varying the different operating parameters, such as pressure (6.7 – 267 Pa), power (40 -120 W) and gas flow (20 – 120 sccm), it is possible to control the size of the nanoparticles (10 – 150 nm), as well as it is possible to control the deposition rate (0.4 – 4.0 nm/min) and the size particles with the applying of a bias (60 – 240 V) to the substrate.

The size and morphology of the nanoparticles were measured by SEM images. X-ray diffraction and XPS were used to determine the structure and composition of the deposits.

BP64 TheIinfluence of the Inert and Reactive Gas Inlet Temperature and Pressure on the Reactive Sputtering Process Outcomes
Sofia Faddeeva, Joaquin Oseguera (ITESM-CEM, Mexico)
The influence of the inert and reactive gas inlet temperature and pressure on the reactive sputtering process outcomes is modeled using the thermodynamic model. The numerical simulation results are compared to the available in literature experimental results and are found to be in reasonable concordance with them.
BP65 Hardness and Elastic Modulus of Hard Coatings at High Temperatures
Marisa Rebelo de Figueiredo (University of California Berkeley); Michael Tkadletz (Materials Center Leoben Forschung GmbH); Robert Hollerweger (Christian Doppler Laboratory for Application Oriented Coating Development at the Institute of Materials Science and Technology, Vienna University of Technology, Austria); Adrian Harris (Micro Materials Ltd, UK); Manuel Abad (University of California Berkeley); Paul Mayrhofer (Vienna University of Technology, Austria); Christian Mitterer (Montanuniversität Leoben, Austria); Peter Hosemann (University of California Berkeley)
Nanoindentation has been established as a standard method to evaluate the mechanical properties of coating materials utilizing the Oliver and Pharr approach for data analysis. The measurements to obtain the hardness and elastic modulus are commonly performed at room temperature. Industrial applications like metal cutting cause friction between the tool and the workpiece leading to temperatures up to 1000°C. Therefore, knowledge on understanding and characterizing mechanical properties of hard coatings at elevated temperatures is of vital importance. Within the present work, nanoindentation measurements up to 700°C were conducted in order to study the evolution of mechanical properties of hard coatings close to operational conditions. The coating systems evaluated represent state‐of‐the‐art materials for cutting applications, i.e. Al2O3, TiAlN, TiCN, TiN as well as newly developed coating materials like TiAlTaN. The substrate materials used were cemented carbides and sapphire. As a general trend it was found that the hardness and the elastic modulus decrease with increasing temperature for all tested coatings. The degradation of the properties was found to be between 30 and 80 % of the room temperature value depending on the coating material. The obtained results are intended to aid future studies on the temperature dependence of structure and properties of hard coatings with the final goal of further improvement of hard coating materials to fulfill the ever increasing demands in metal cutting.
BP66 Electrochemical and Impact Wear Behavior of TiCN, TiSiCN, TiCrSiCN, and TiAlSiCN Coatings
Dmitry Shtansky, Konstantin Kuptsov, Philipp Kiryukhantsev-Korneev, Alexander Sheveko (National University of Science and Technology “MISIS”, Russian Federation)

This study evaluates the performance of magnetron-deposited Cr- and Al-doped TiSiCN coatings, which were previously reported to have an excellent tribological properties, enhanced thermal stability and high-temperature oxidation resistance. Here, the behavior of these coatings during scratch tests, dynamic impact and electrochemical tests was studied and compared with that of the TiCN and TiSiCN reference coatings. The structure, elemental and phase compositions of coatings were studied by means of X-ray diffraction, scanning electron microscopy, and glow discharge optical emission spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, elastic recovery, and adhesion strength. To evaluate their electrochemical characteristics, the coatings were tested in 1N H2SO4 and 0.9% NaCl solutions. The coatings were also subjected to a range of impact tests, first in air, and then in normal saline (to assess a tribocorrosion effect) and distilled water (to assess a hydrodynamic effect in liquid). Under dynamic impact load, the coatings showed different impact resistance improving along the row TiCN→TiSiCN→TiCrSiCN→TiAlSiCN. In air, the TiSiCN, TiCrSiCN, and TiAlSiCN coatings endured a dynamic impact force as high as 1000 N with a minimum impact wear observed for the TiCrSiCN and TiAlSiCN coatings. The accelerated degradation of the TiCN, TiSiCN, and TiCrSiCN coatings in distilled water and normal saline was attributed to both the NaCl-induced corrosive processes and hydrodynamic effect resulting in accelerated abrasive wear. The TiAlSiCN coating was the only sample to sustain a repetitive impact load of 500 N for 105 cycles both in distilled water and normal saline.

BP67 A Study of Thermal Stability, Structural and Mechanical Properties of ZrxW1-xNy Coatings Deposited by DC/RF Reactive Magnetron Sputtering
Paritosh Dubey, Ramesh Chandra, Arya Vivek, Devendra Singh, Vikramaditya Dave (Indian Institute of Technology Roorkee, India)

In recent years, great attention has been devoted to the development of a new class of thin films with a special structure and unique properties against thermal stability and wears damage. The high metastability of the amorphous structure is the most striking aspect of ternary nitride alloys and is one of the reasons for their successes as thin-film diffusion barriers in semiconductor metallization technology.

Zirconium tungsten nitride (ZrxW1-xNy) nanocrystalline films represent a new class of ternary metal nitride coating material. In the present work, films were deposited onto Si substrates using DC/RF reactive magnetron sputtering. The temperature dependence of the structure, morphology, stability and mechanical properties have been studied of the films under two different conditions; (i) Films have been deposited in-situ at various substrate temperatures (room temperature ~ 300C to 6000C). (ii) Ex-situ annealing have been done up to 6000C in the ambient atmosphere of films deposited at 300C. It was found from the first kind of treatment that (i) there is a strong correlation between crystallization and deposition temperature and (ii) the thickness and hardness of the films have dual trend depending on the phases present in the films. (iii) the maximum hardness achieved is ~ 25 GPa of the films deposited at 3000C, while,the outcome of lateral treatment were (i) No significance of oxide phase formation except the broadening of hump.(ii) The O2 start to incorporate above 2000C with increasing tendency up to 6000C. (iii) The RMS roughness (δrms) and thickness of the films increases with annealing temperature (iv) The hardness decreases (~11GPa) as the percentage of O2 increases in the films.

The characterizations of the deposited films have been done using XRD, FE-SEM, EDS, AFM and Nanoindentation techniques.
BP68 The Investigation of the Adhesion, Wear and Friction Properties of TiN/TaN Multilayer Coatings
Ozlem Baran (Erzincan University, Turkey); Ebru Demirci, Ihsan Efeoglu, Yasar Totik (Atatürk University, Turkey)

TiN and TaN coatings widely used due to excellent mechanical and tribological properties. Specifically, TiN/TaN multilayer coatings have been exhibit superior mechanical and chemical properties, such as hardness, adhesion and wear resistance, when compared to single layer nitride coatings. Therefore, in recent years, multilayer coatings composed of two kinds have been investigated. For this reason, in this study, TiN/TaN multilayer films were deposited on Mo-alloy substrate and Cu-alloy substrate by Closed-Field Unbalanced Magnetron Sputtering (CFUBMS). The structural and mechanical properties of these films were analyzed by using XRD, SEM and microhardness tester, respectively. The adhesion and fatigue properties of the coatings were evaluated via a scratch test in two modes. A sliding-fatigue multimode operation was used that involved multi-pass scratching in the same track at different fractions of the critical load (unidirectional sliding), and a standard mode with progressive loading was also utilized. Adhesion and fatigue properties of TiN/TaN multilayer coatings deposited on different substrates were discussed according to microscopic image examinations of the scratch tracks.

Key Words: TiN, TaN, multilayer films, CFUBMS, adhesion, fatigue

BP69 Rapid Annealing of TaN-(Ag,Cu) Thin Films Deposited on PEEK Polymer Substrate by Pulse Current Heating
Jang-Hsing Hsieh, Yu-Tai Su (Ming Chi University of Technology, Taiwan, Republic of China)
Pulse current annealing (PCA) technique has the advantage of heating up conductive film while maintaining low substrate temperature. In this study, a PCA system was used to anneal TaN–(Cu,Ag) nanocomposite films deposited on polyether ether ketone (PEEK). The emergence of Ag and Cu particle and substrate/film temperature difference was studied as functions of frequency and ON/OFF time ratio.

TaN–(Cu,Ag) nanocomposite films were deposited by reactive co-sputtering with Ag/Cu=6.5/3.5 in atomic %. The total amount of soft metal contents is 7 and 11 at.%. After PCA, the films were characterized using XRD, FESEM, nano-indentation. The tribological properties and antibacterial behaviors were also examined. The results show that the increase of pulse frequency and the reduction of ON/OFF ratio would enlarge substrate-film temperature difference. Therefore the substrate could be protected better. Through the anti-wear and anti-bacteria studies, it was found that the film/substrate system, after PCA, could maintain low frication and low wear rate, and high antibacterial efficiency against E. Coli. All these properties were related to pulse frequency and ON/OFF time ratio.

BP70 Synthesis and Characterization as Hydrocarbon Sensors of Nanostructured ZnO Sputter-deposited Coatings
Mohammad Arab Pour Yazdi (IRTES-LERMPS-UTBM, France); JeanBaptiste Sanchez (Umr Cnrs 6249, France); Eric Monsifrot (Sarl Dephis, France); Pascal Briois (IRTES-LERMPS-UTBM, France); Franck Berger (UMR CNRS 6249 University of franche comte, France); Alain Billard (IRTES-LERMPS-UTBM, France)

Recently, zinc oxide (ZnO) thin films have attracted increasing attention due to their excellent properties and their potential applications in various fields; gas sensors, piezoelectric devices, transparent conductive electrodes …. The performance of ZnO coatings in a number of modern devices and especially as gas sensors is strongly linked to their specific surface that can be tuned by controlling their morphology. ZnO nanostructures such as nanowires/nanorods, nanobelts, and nanodots are the object of intensive studies. Most of nanostructured ZnO materials are synthesized by vapour transport based on vapour–liquid–solid (VLS) growth mechanism using a noble metal as catalyst such as Au and Cu. However, some studies show that Au is not necessary for nanowire growth. Among the different deposition methods, the technique used in this study is the reactive magnetron sputtering.

In this paper, we investigate the feasibility of ZnO coatings with different morphologies (dense, porous, nano-wire and nano-tree) by reactive magnetron sputtering. After a short description of the experimental devices used for the deposition stage and the hydrocarbon sensing bench, a first part will be dedicated to the chemical, microstructural and structural characterization (SEM, XRD,…) of coatings in relation with their deposition parameters. We will the report the performance as dodecane-sensors of ZnO coatings with different morphologies as a function of dodecane concentrations and sensor surface temperature.

BP71 A New Dedicated DLC Coating System for Threading in Titanium
Marcus Morstein, Pascal Dessarzin (PLATIT AG, Switzerland); Klaus Gerschwiler (RWTH Aachen University); Heiko Frank, Mario Schiffler (GFE Schmalkalden e.V., Germany)

TiAl6V4 and other titanium alloys are high-performance alloys used for lightweight and high strength applications due to their low density (ρTi = 4,51 kg/dm3) in combination with a high yield strength of about 1’000 MPa. However, titanium alloys are considered as difficult to machine materials due to their high strength, the low Young’s modulus, the low thermal conductivity and the high tendency to sticking during the cutting process.

The present work shows how the lifetime and productivity of a coated state-of-the-art thread cutter can be improved. Crucial for the tapping is to ensure a reliable process, since the thread cutting in a component is usually one of the last machining steps conducted, and thus tool failure at this point would lead to the loss of an already highly valuable work piece.

The parameters used to optimize the performance of the reference tool were the cutting edge pre- and post-treatment as well as the coating type. Since first experiments showed that the sticking of titanium on the flank of the thread cutter is the lifetime limiting factor, a tribological experiment was used to evaluate the affinity of various nitrides, oxynitrides and DLC coatings to titanium. Measurements were done at 400°C on coated test plates against a TiAl6V4 pin and the build-up was then quantified using a profilometer. The results identified different behavior for the investigated coating types, which will be discussed and correlated to the cutting performance of the coated tools.

By selecting an appropriate coating as well as using optimized pre- and post-treatment the lifetime of the newly developed thread cutter could be more than doubled compared to the reference tool and further on this new generation tool was capable to work at faster cutting speeds in production.

BP72 Study on the Characteristics of MoN Doping Cu Amorphous Thin Film Fabricated by Pulse Magnetron Sputtering Process
Chia-Hung Huang, Weng-Sing Hwang (National Cheng Kung University, Taiwan, Republic of China); Chi-Wen Chu (Metal Industries Research & Development Centre, Taiwan, Republic of China); Shyh-Jiun Liu, Hao-Yu Chu (National Unversity of Tainan, Taiwan, Republic of China)
The corrosion resistance of NdFeB magnets is improved by direct MoCu and MoCuN thin film treatment of a sintered NdFeB magnet surface. X-ray diffraction and transmission electron microscopy are used to examine the microstructure of the thin films. The hardness, wettability, and surface roughness of the thin films are investigated using nanoindentation, contact angle measurements, and atomic force microscopy, respectively. The MoCu and MoCuN thin films exhibit a typical amorphous microstructure and a smooth surface with an average roughness of about 2 nm. The results of alternating-current (AC) impedance spectroscopy in 5% NaCl solution show that the AC impedance of the thin films increased with time. The lZl10mHz values for NiCrAlVN (15000 ohms/cm2), NiCrAlV (4000 ohms/cm2), and uncoated NdFeB magnets (550 ohms/cm2) show an 8-fold increase in the low-frequency impedance due to the amorphous state.
BP73 Thermal Stability and Oxidation Behavior of Reactively Sputtered TaN Coatings
Fan-Bean Wu, Kun-Yuan Liu (National United University, Taiwan, Republic of China)
Tantalums nitride, TaN, coatings with various microstructure are fabricated by magnetron sputtering. Through N2/Ar gas flow ratio control, the TaN coatings are manufactured with amorphous, nanocrystalline, and columnar crystalline features. TaN multilayered coating with alternating stacking of the amorphous and crystallized TaN nanolayers is also deposited for comparison. Thermal stability of various TaN films is examined through vacuum and air annealing at 350 to 550 ° C. All the TaN coatings remain their structural features under vacuum annealing, while significant oxidation occurs in the crystalline TaN coatings. The oxidation penetration is reduced due to the introduction of alternatively stacking amorphous/crystalline TaN nanolayers. The microstructure evolution and oxidation of various TaN coatings are also investigated under a high temperature glass contact experiment. The oxidation mechanisms for the TaN coatings under various annealing environments are discussed.
BP74 Electrochemical Impedance Spectroscopy Evaluation of Aluminium-Based PVD Coatings Exposed to Salt-Spray Corrosion
Fahima Indeir, Omoniyi Fasuba, Allan Matthews, Adrian Leyland (University of Sheffield, UK)

Evaluation of the corrosion behaviour and the protective properties of Al-based PVD coatings in aqueous solution have been carried out by Salt Spray Testing (SST) and Electrochemical Impedance Spectroscopy (EIS). SST offers many advantages, including the fact that it is a standardised method for conducting exposure to a corrosive environment and evaluating the results. However, SST has been criticised for its lack of reproducibility from one test to another, and for failure to provide a quantitative measure of corrosion degradation. The EIS method is a well-established technique and a powerful tool to determine a quantitative, numerical value for corrosion damage of coatings, and to investigate the electrochemical reactions mechanisms of the corrosion process in a short period of time. Coatings produced by physical vapour deposition (PVD) techniques can increase the lifetime and service quality of the system. Two main objectives are taken into account in this study; firstly, to evaluate the corrosion behaviour of Al-based PVD coatings after SST exposure and in 3.5% NaCl solution at different exposure times, by EIS. Secondly, to obtain a correlation between SST and EIS test results for Al-based PVD coatings. SST experiments were carried out after exposure times of 24, 48,123, 216 and 384hrs for ten test panels of PVD AlCr coatings deposited at 300oC & 400oC. EIS experiments of PVD AlCr coatings deposited at 300oC & 400oC have been carried out after open circuit potential (OCP) stabilisation, as a function of the immersion time for 24, 48,123, 216 and 384hrs in 3.5wt% NaCl solution. EIS data was obtained using an electrochemical cell instrument and then the experiments is complemented by scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX) composition analysis and phase analysis by X-Ray Diffraction (XRD).

BP75 Comparison Between Single Phase Ti and Cr-nitrides Thin Films Deposited by Different Processing Routes
Fernando Lomello (DEN/DANS/DPC/SEARS/LISL CEA Saclay, France); Mohammad Arab Pour Yazdi (IRTES-LERMPS, France); Daniel Schlegel (ESTA, France); Alain Billard (IRTES-LERMPS-UTBM, France); Frédéric Sanchette (LRC CEA-ICD LASMIS, Nogent International Center for CVD Innovation (Nicci), France); Frédéric Schuster (CEA Cross-Cutting Programme on Advanced Materials, France); Michel Tabarant (DEN/DANS/DPC/SEARS/LISL CEA Saclay, France)

Titanium and chromium nitrides were deposited by means of two high energetic deposition techniques such as cathodic arc deposition and high-power impulse magnetron sputtering (HIPIMS) [1,2].

The aim was to establish a correlation between these techniques and the resulting morphological-mechanical properties. Firstly, a physicochemical characterization was conducted employing X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) techniques.

Subsequently, the mechanical-tribological characterization allows the comparison of the different chemical-morphological properties. The resulting properties were strongly depending on the processing routes and their specific parameters. For instance, the differences in terms of surface roughness affected the final tribological properties.

The built-up of material at the edge of the wear tracks found after ball-on-disc tests is in good agreement with higher droplets’ density. Indeed, the better surface state (no droplets) in the case of HIPIMS leads to the reduction of the coefficient of friction (COF). It is well known that macroparticles emission creates defects (droplets) in non-filtered cathodic-arc evaporation processes. These droplets act as cutting edges, thus increasing the COF as reported by several studies [3].

Taking into account that until now, HIPIMS has few industrial applications, a final aspect concerning the industrial up-scaling feasibility was investigated. To accomplish this aim, several aspects such as the deposition rates and the measured final properties were considered. Finally, the machining performances on the developed coatings were measured, in order to justify the advantages of HIPIMS if compared with the cathodic-arc process.


[1] F. Sanchette et al. Surf. Coat. Technol. 205 (2011) 5444.

[2] A.P. Ehiasarian et al. Surf.Coat. Technol. 163-164 (2003) 267.

[3] O. Banakh et al. Surf.Coat. Technol. 163-164 (2003) 57.

BP76 Improving the Corrosion Resistance of Electroplated Chromium Coatings on AISI H13 Steel by Gaseous Nitriding in Vacuum
Hector Cifuentes, JhonJairo Olaya (Universidad Nacional de Colombia Bogotá, Colombia)
The development of chromium nitrides of type CrxN from the surface and subsurface modification of electrolytic chromium coatings applied to ferrous substrates (AISI H13) can improve the corrosion resistance of the metallurgical system. This document shows the results of this process through the realization of a duplex treatment that combines the application of a chromium hard coating Cr(VI) on a steel AISI H13 with a thermochemical treatment of gaseous vacuum nitriding . The electrolytic coating thickness was 15 μm, and N2 was used as precursor gas with a flow of 100 ml/min at a pressure of 1.2 kPa. The existing phases were determined by means of X-ray diffraction, and the corrosion resistance was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy techniques in a three electrode electrochemical cell. The characterization by XRD could determine the presence of chromium nitrides of type Cr2N, with an important texturing in the plane (300) associated with the partial pressure of N2 and the thermodynamic behavior, which favors the preferential orientation of this phase in the orientation exhibited. The corrosion resistance results of potentiodynamic polarization showed a significant decrease in the corrosion current density compared to those exhibited by samples electrolytically chromed with steel AISI H13 without nitriding . The EIS results showed a significant increase of the load transfer resistance and an increase in the impedance values ​​for low frequencies up to 3 orders, from 104 Ohm/cm2 to 107 Ohm/cm2. These results, coupled with the sealing of characteristic microcracks of the electrolytic chrome coating, could improve the corrosion resistance because of the existence of the Cr2N phas.

BP77 Enhancement of Mechanical and Tribological Properties in NiTi Shape Memory Alloy Thin Films by Using Graded AlN/Al Multilayer Coating
Navjot Kaur, Davinder Kaur (Indian Institute of Technology Roorkee, India)

Shape memory alloy (NiTi) thin films coupled with graded AlN/Al multilayers produce an intelligent material having improved mechanical and tribological properties. In the present study [AlN/Al]n/NiTi/Si heterostructures have been deposited on Si substrate using magnetron sputtering technique. AlN/Al multilayers were grown on NiTi/Si in a graded pattern with bilayer period n=1, 4, 8 & 12 and the effect of bilayer period on different properties of heterostructure was evaluated. The heterostructures were characterized in terms of structural, electrical, morphological, mechanical and tribological properties by X-ray diffraction (XRD), four probe resistivity method, atomic force microscopy, field emission scanning electron microscopy, nanoindentation, and scratch tests. The bilayer period of AlN and Al had great influence on the hardness and the toughness properties of the heterostructure. This enhancement in hardness and toughness of the heterostructure could be attributed to the different mechanisms for layer formation with nanometric thickness such as the Hall–Petch effect and the number of interfaces that act as obstacles for the crack deflection and dissipation of crack energy.

Keywords : NiTi, Magnetron Sputtering, Shape memory, Nanoindentation

BP78 Property Evaluation in Humid Environments of Silicon-doped DLC Films Deposited by Plasma Immersion Assisted Deposition
Chang Liu, Jack Cooper, Heqing Li, Martynas Audronis, Allan Matthews, Adrian Leyland (University of Sheffield, UK)

Plasma immersion assisted deposition (PIAD) is an effective deposition technology for synthesising high quality carbon thin films. A graded layer structure which can mitigate delamination and improve adhesion can be achieved by this combined implantation and deposition technique. Hydrogen containing diamond like carbon (a-C:H) films exhibit an ultra-low sliding coefficient of friction (CoF) in dry or inert (e.g. vacuum) environments; however, the CoF of a-C:H changes dramatically with increasing humidity. Silicon-doped a-C:H (Si-DLC) films can show better humidity adaptability compared with a-C:H films. In this study, diamond-like carbon films with different silicon doping contents were deposited by PIAD with different experimental parameters. Nano-indentation and impact testing were used to investigated the mechanical properties e.g. hardness, elastic modulus and adhesion of Si-DLC coatings. Pin-on-disc wear tests were applied in an environmental chamber with humidity control, to examine the friction and wear properties at different RH% values. The chemical compositions are also examined by Energy Dispersive X-ray (EDX) analysis and Raman Spectroscopy.

BP79 First-principles Calculations on the Thermodynamic and Mechanical Properties of Ti-Al-(Zr, Hf)-N Wear-resistant Coating Systems
Aijun Wang (National Center for Quality Supervision and Inspection of Building Decoration Materials, China); Weiwei Wang, Yong Du, Li Chen (State Key Laboratory of Powder Metallurgy, Central South University, P.R. China)

Based on the first-principles calculations, the properties of TiAl(Zr, Hf)N system have been systematically investigated and the calculated results are compared with the available experimental data. The predicted structural, phonon, electronic, and thermodynamic properties of cubic binary nitrides MN (M= Ti, Al, Zr and Hf) can give an accurate prediction for the high temperature thermodynamic properties, especially for the thermodynamic data which are difficult to determine by experiments. The temperature dependence of elastic constants are computed for the first time by first-principles quasiharmonic approach and efficient stress-strain method and is beneficial to the determination of residual stress of coatings. The effects of both lattice vibration and pressure on the thermal decomposition of TiAlN, ZrAlN and TiZrN have been first considered in the present work. It is found that the pressure increasing make the temperature of predicted binodal and spinodal curves increase, while the vibration contribution significantly decreases the temperatures. In addition, the study indicates that the improved age hardening of cubic Ti-Al-N coatings by adding Zr is because of the enlarged composition range of binodal and spinodal curves. Finally, the quaternary SQS models have been developed in the present work to describe the disordered solid solution, based on which the mechanical properties of Ti-Al-Zr-N and Ti-Al-Hf-N coatings are calculated. Additionally, the effect of addition of Zr and Hf on the spinodal decomposition is studied. It is concluded that Zr and Hf are effective in influencing the age-hardening as they promotes the coating spinodal decomposition. Present work allows the combination of theoretical predication and experiment research, which provide the theoretical guidance and useful information for the further research of coatings system.

BP80 Interfacial Structure of Ti2AlN Thin Film Deposited on MgO(111): Experimental and Computational Study
Hongmei Jin (Institute of High Performance Computing, Singapore)
Single-crystalline Ti2AlN thin films have been grown on MgO(111) substrates at 750oC using DC magnetron sputtering from a Ti2Al alloy target in a mixed N2/Ar plasma. X-ray diffraction and atomic force microscopy confirm epitaxial layered growth of Ti2AlN {0002} on MgO(111). ab initio calculations were carried out to study the interfacial structure between Ti2AlN and oxygen/magnesium terminated MgO polar surfaces. It was found that the adhesion energies of Ti2AlN (0001) with O terminated MgO(111) are stronger than that with Mg terminated MgO(111) surfaces. In particular, strong charge transfers and ortital hybridizations between Ti2AlN and O terminated MgO(111) were observed. In addition, the stacking sequence of N-Ti-Al-Ti/O–Mg exhibited the largest adhesion energy among all, suggesting this interfacial structure might be the most stable structure of Ti2AlN thin film growth.
BP81 Study of the Mechanical Properties of PVD Metallic Nanocomposite Cr(N)-based Coatings with Combined Additions of Silver and Copper
Xingguang Liu, Martynas Audronis, Aleksey Yerokhin, Allan Matthews, Adrian Leyland (University of Sheffield, UK)
Hard and superhard nanocomposite coatings have been intensively investigated in recent years. However, consideration of the hardness to elastic modulus ratio (H/E) has been shown to have greater merit than high hardness alone, in optimising coating mechanical properties and durability. In this study, we aim to obtain high H/E ratio coatings by controlling the nanocomposite structure of metallic nitrogen-containing PVD chromium coatings, rather than trying to obtain hard (ceramic) nitrid-containing structures. Solid lubricant (and antibacterial) ingredients – in this case both silver and copper (each of which generate different coating morphological effects) – were added to the coatings, to attempt to improve friction and wear properties, as well as to provide improved multifunctional behaviour. Coatings were deposited using a dual-target unbalanced magnetron sputtering system. Nano-indentation, sliding wear and impact wear tests were used to evaluate mechanical properties such as hardness, elastic modulus, coefficient of friction and wear resistance. X-ray diffraction, scanning electron microscopy and Energy Dispersive X-ray analyses were used to analyse the effects of the chemical composition (Cr-Ag-Cu-N), distribution of these elements (and resulting coating nanostructure) on the functional properties.
BP82 Improving the Corrosion and Tribological Performance of Magnesium Alloys by Using Duplex Surface Treatments
Lian Liu, Martynas Audronis, Aleksey Yerokhin, Allan Matthews, Adrian Leyland (University of Sheffield, UK)

Magnesium is a promising engineering material with a high strength-to-weight ratio which enables lighter products to be achieved. Moreover, the excellent castability and weldability of magnesium alloys contribute to this material’s suitability for prospective markets in the construction, automotive, aerospace and communications industries. However, several undesirable properties of magnesium alloys have prevented their widespread adoption; these include insufficient resistance to creep and poor corrosion and wear resistance.Depositing protective coatings onto magnesium alloy parts is an effective strategy to improve the corrosion and wear performance. In this work, duplex surface treatments incorporating novel PVD techniques are used to explore the wider application of magnesium alloys. To improve the durability of low-strength Mg-alloy products in tribological applications, a relatively soft and compliant, amorphous interface layer (rather than the hard – and brittle – AlMg intermetallic compound-containing layers so far explored in the literature), containing B, N, Zr, Ti or Cr elements (as well as Al), is deposited by plasma-assisted PVD. The introduction of an amorphous and/or nanocrystalline interface, with an elastic modulus closer to that of the underlying Mg-alloy substrate, accommodates substrate strain more effectively. In addition, on top of the interface layer, ceramic coatings such as TiN, CrN (or plasma electrolytic oxidation post-treatments) can be deposited to increase the hardness and corrosion resistance of the surface. Compared to hard coatings deposited directly onto Mg-alloy substrates, this design philosophy improves the matching of coating/substrate interfacial mechanical properties, such that coating toughness is enhanced by accommodation of the deformation energy without fracture. Overall, we show that such duplex layered treatments have potential to provide improved wear and corrosion protection to Mg-alloys.

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