ICMCTF2003 Session B1: Sputtering Coatings and Technologies

Thursday, May 1, 2003 8:30 AM in Room Golden West
Thursday Morning

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8:30 AM B1-1 Oxidation Behaviour of Nanoscale TiAlN/VN Multilayers
Z. Zhou, W.M. Rainforth (The University of Sheffield, United Kingdom); D.B. Lewis, S.J. Creasey, P.Eh. Hovsepian, W.-D. Münz (Sheffield Hallam University, United Kingdom)
The lower friction coefficient (µ=0.4) and excellent sliding wear resistance (Kc=1.2´10-17 m-3/N m) of TiAlN/VN multilayers in comparison to other state-of-the-art PVD coatings was attributed to the possible formation of a lubricious surface oxide of V2O5, indicating that oxidation was a key factor during the performance. Nanoscale multilayer TiAlN/VN coatings were grown using combined cathodic arc/unbalanced magnetron deposition (arc bond sputtering, ABS) in an industrially sized physical vapour deposition machine. The coating structure comprised a ~ 2.5µm thick TiAlN/VN multilayers coated on top of a ~ 0.25µm thick VN base layer on a stainless steel substrate. Dynamic thermo-gravimetric analysis (TGA) showed that the coating experienced pronounced weight gains around 638°C, indicating the onset of significant oxidation. Samples heated in ambient atmosphere at 550oC, 600oC, 638oC and 670oC isothermally for 30 minutes were studied. Field emission gun scanning electron microscopy (FEGSEM) revealed ultra-fine oxides at the early stage of oxidation on the surface of sample heat-treated at 550oC /30min. Glancing-angle X-ray diffraction (XRD) showed evidence of oxidation at 600oC by the presence of V2O5 and TiO2 on the top of the coatings. At 600oC enhanced growth of needle and plate shaped undense oxides were found on the top of the coating. At 638oC, XRD pattern showed a sharp peak for V2O5. In parallel TGA indicated the complete oxidation of VN component of the nanoscale multilayers coating. At 670oC, V-rich round shaped islands are distributed over the oxidised surface of the coating. The shape of the island suggested that the V2O5was molten. The fact that V2O5existed in a molten state let one to assume that the tribological application of TiAlN/VN at temperature above 650oC seems to be limited.
8:50 AM B1-2 Multilayereded Coatings with Alternate Pure Ti and TiN/CrN Superlattice
Q. Yang, L.R. Zhao (Institute for Aerospace Research, National Research Council Canada)
Multilayered coatings containing alternate layers of pure Ti and TiN/CrN superlattice were deposited with controlled layer thickness and superlattice bilayer period using magnetron sputtering technique. The preferred orientation of the TiN/CrN superlattice layers is either (111), (200) or random depending on the sub-structure of the Ti layers. Nanoindentation testing shows that mechanical properties of the coatings vary with the bilayer period, crystallographic orientation and volume fraction of superlattice in the coating. For the same bilayer period and volume fraction, coatings with (200)- oriented superlattice layers are harder than those with randomly and (111)- oriented superlattices. Scratch testing indicates the interface adhesion between coating/substrate and superlattice/Ti is weak. Coatings with a large hardness difference between the superlattice and Ti layers have a strong tendency towards interfacial detachments. Due to the brittle nature of the superlattice layers and weak interface adhesion, these multilayered coatings exhibited poor performance in erosion testing involving impingement of the coatings by high-speed sand particles, which caused intensive cracking and localized interfacial detachments between the coating and substrate and between the superlattice and pure Ti layers.
9:10 AM B1-3 Investigation of Nanocrystal-(Ti,Al)Nx / Amorphous-SiNy Composite Films by Co-Deposition Processes
J.-L. Huang, B.-S. Yau (National Cheng-Kung University, Taiwan, ROC); D.F. Lii (Chinese Naval Academy, Taiwan, ROC)

Nanocrystal-(Ti,Al)Nx / amorphous-SiNycomposite films were prepared by co-deposition processes. The effects of deposition parameters on composition, texture, lattice parameter, preferred orientation, grain size, grain morphology, fractured cross-sections, surface morphology, and roughness of (Ti,Al)Nx films were analyzed by x-ray photoelectron spectroscope, x-ray diffraction, transmission electron microscopy, scanning electron microscope, and atomic force microscope. The mechanical properties were also investigated.

The results indicated that the composition of nanocomposite films was uniform and could be controlled through the co-deposition process. Nanocrystal (Ti,Al)Nx embedded in amorphous SiNy matrix with (200) preferred orientation was observed. The content of amorphous SiNy has substantial influence on the stresses release, columnar structure, surface morphology, hardness, nanograin size and dome-shaped.

9:30 AM B1-4 Deposition of α-Alumina Hard Coatings by Reactive Magnetron Sputtering
T. Kohara, H. Tamagaki, Y. Ikari, H. Fujii (Kobe Steel, Ltd., Japan)

Alumina as top-coat of hard coatings is considered as the suitable material for oxidation-resistance and heat-resistance layer of cutting tools. Particularly, α-alumina with corundum structure is considered as the best because of its higher thermal stability than any other crystal structure of alumina. However, such film can be commercially deposited only by CVD at temperature above 1000°C.

In this work, the deposition of crystalline PVD-Alumina at lower temperature on cemented carbide substrates by reactive magnetron sputtering was reported. The films were deposited from the metallic aluminum targets in Ar and O2 mixture at the substrate temperature from 600°C to 780°C in the production scale PVD system. By combining discharge voltage control and optical emission feedback, the deposition rate as high as 0.8µm/hr was achieved. Under the optimized conditions, the formations of single phase α-Al2O3 with good crystallinity was confirmed by low angle XRD analysis. The deposited films were characterized by hardness and adhesion, and the film compositions were measured by XPS. The structure and morphology of the films were observed by SEM.

9:50 AM B1-5 On the Deposition Process of Silicon Suboxides by a RF Magnetron Reactive Sputtering in Ar-O2 Mixtures: Theoretical and Experimental Approach
A. Palmero-Acebedo, N. Tomozeiu, A.M. Vredenberg, F.H.P.M Habraken (Utrecht University/Debye Institute, The Netherlands)
Magnetron reactive sputtering of silicon oxides produced by Ar-O2 RF capacitive plasma has been studied from a theoretical and experimental point of view. In this way a cross-section averaged plasma model has been developed, that allows to know the densities and temperatures of all the species of the plasma, as well as all the flows of charged particles. This model is coupled with a sputtering model, which relates the plasma properties to the deposition process. Therefore, the substrate stoichiometry, as well as the deposition rate, is obtained as a function of the model input parameters, i.e. the argon and oxygen flows, RF power and pumping speed. These results are compared with experimental measures on both plasma and deposited layers. Optical emission spectroscopy was used in order to characterize plasma volume, whereas the stoichiometry of the SiOx layers is determined by RBS and XPS measurements. A good agreement between theoretical predictions and experimental data is found in several deposition conditions. A discussion about these results is carried out.
10:10 AM B1-6 Influence of Negative Bias on Structure of Polycrystalline Tin-nitride Films Deposited by Reactive Sputtering
Y. Inoue, J. Matsui, O. Takai (Nagoya University, Japan)

Metallic tin and its alloys have been utilized since the Bronze Age, and their properties have been well-known as well as tin oxides, which have also been extensively studied and already put to practical use to gas-sensing and transparent-conductive devices. On the other hand, the characteristics of any binary tin-nitrogen compound have not been clarified. In this study, we report on the influences of negative bias on structural properties of tin-nitride thin films prepared by reactive sputtering.

Tin-nitride films were prepared by using an rf magnetron sputtering system. The nitrogen pressure was kept at 1 Pa. We varied a substrate bias in the ranges of 0 ~ -200 V. The crystal structure of the deposited films was characterized by X-ray diffraction (XRD). The chemical bonding states and the chemical compositions were investigated by X-ray photoelectron spectroscopy (XPS). Cross-sectional structure of the films was observed by using both a scanning electron microscope (SEM) and a transmission electron microscope (TEM).

Some sharp diffraction peaks were observed in the XRD patterns. From the peak positions, we confirmed the crystal structure of the tin-nitride film is spinel. The crystallinity of the films was strongly influenced by the substrate bias. Preffered orientation of the deposited films varied from 111 to 311 with increase in the negative bias. XPS analyses revealed that the Sn-N bonds in the films are more covalent than Sn-O in tin oxide. In the cross-sectional SEM images, we observed that the films consist of two layers: the surface-side layer shows clear columnar structure while the substrate-side one has no texture, which means the polycrystalline tin-nitride grow on amorphous tin-nitride buffer layers.

10:30 AM B1-7 Deposition of Customized-index Optical Films by Mid-frequency Dual Magnetron Reactive Co-Sputtering.
D.J. Christie, W.D. Sproul, D.C. Carter (Advanced Energy Industries, Inc.)
Reactive co-sputtering gives the optical coating designer new options, and enables practical realization of new classes of coatings. It is a way to create films of customized or graded index of refraction. Two adjacent targets may be sputtered so material from both targets and a reactive gas flux are incident on the work piece. The resulting film deposited on the work-piece is a compound consisting of the two target materials and the reactive gas. For example, if the two targets are Si and Ti, and the reactive gas is oxygen, then the index of the film may be adjusted from about 1.5 to 2.4 by appropriately setting the power to each magnetron. The application of reactive co-sputtering has been limited by the disappearing anode effect when DC supplies are used, and the relative inability to adjust the power to each magnetron when mid-frequency AC supplies are used in dual magnetron sputtering. However, recently developed current-source pulsed supplies can independently regulate power delivered to each magnetron in dual magnetron sputtering, which eliminates disappearing anode effects. This enables reactive co-sputtering of optical films, without the prior disappearing anode and individual magnetron power adjustment issues. We present optical films having a customized index of refraction deposited by mid-frequency dual magnetron reactive co-sputtering, with independent target power regulation. We also show the ability to create films with a range of indexes, and discuss process limitations and boundaries.
10:50 AM B1-8 Wear Resistance of Chromium Nitride Coatings Deposited by High Power Impulse Magnetron Sputtering
A.P. Ehiasarian, W.-D. Münz (Sheffield Hallam University, United Kingdom); L. Hultman, U. Helmersson (Linköping University, Sweden)

Sliding and abrasive wear tests were performed on chromium nitride (CrN) coatings deposited on mirror-polished M2 high speed steel substrates by the novel high power impulse magnetron sputter (HIPIMS) deposition technique utilising peak cathode powers of 3000 Wcm-2, applied at a repetition frequency of 50 Hz and a duty cycle of <1%. The samples were metal ion etched using non-reactive HIPIMS at a substrate bias voltage of -1200 V. Subsequently a 2 µm thick CrN was deposited by reactive HIPIMS at a deposition rate of 0.5 µmh-1 on the samples positioned at a distance of 10 cm from the target. No bias was used during the deposition. The ion saturation current measured by a flat electrostatic probe reached peak values of 50 mAcm-2 corresponding to a peak ion-to-neutral ratio of Ji/Jn = 700 during the maximum of the target power pulse. Secondary electron microscope observations of the surface showed a roughening of the samples, which exposed the grain structure and was caused by intensive ion etching during the pretreatment stage. The microstructure of the CrN coatings was highly dense and columnar as observed by transmission electron microscopy.

The CrN films were evaluated in pin-on-disk tests under a normal load of 5 N and using an Al2O3 ball as a counterpart. Abrasive wear tests were carried out using SiC slurry and normal loads of 300 mN. Sliding wear coefficients of 2.3x10-16 m3N-1m-1 measured for these films were lower by factor of 4 and the roughness of the wear track was significantly reduced compared to conventional unbalanced magnetron (UBM) sputtered CrN films. The abrasive wear coefficient, KC, was 2.2x10-13 m3N-1m-1 representing an improvement by a factor of 3 over CrN deposited by conventional UBM sputtering and a wear resistance comparable to that of CrN based superlattice structured coatings such as CrN/NbN and CrN/TiAlN.

11:10 AM B1-9 The Thermal Stability of Sputtered Ni-P-Cr and Ni-P-W Coatings by Cycling Test and Annealing Treatment
W.Y. Chen, F.B. Wu (National Tsing Hua University, Taiwan.); J.G. Duh (National Tsing Hua University, Taiwan)
Ternary Ni-P-Cr and Ni-P-W alloy coating was fabricated by the RF magnetron sputtering technique with dual targets of electroless nickel alloy and a third element metal. The compositions of the as-deposited alloy were measured by electron probe microanalysis. The phase identification was carried out by X-ray diffraction technique. The as-deposited Ni-P-Cr and Ni-P-W coating exhibited amorphous structure. The thermal properties of coating was evaluated by the annealing test at 400°C~600°C for 4hours and cycling test at 400°C~500°C for 30 minutes in N2 atmosphere. The related mechanical properties were measured by Knoop microhardness test and scratch test. Microhardness and adhesion strength were employed to evaluate the thermal stability of the ternary alloy. The maximum microhardness was 1800HK for both the ternary Ni-P-Cr at 500°C and Ni-P-W alloys 550°C, respectively, after 4 hours annealing. For cycling test over 40 times cycles at 400°C, the microhardness was 1600HK, in which fully phase of Ni3P precipitation was not completed. The influence of adding element (Cr or W) and different content of phosphorous on the thermal properties of Ni-P based alloy coating were also discussed.
11:30 AM B1-10 Structure and Tribological Behaviour of Nanoscale Multilayer C/Cr Coatings Deposited by the Combined Steered Cathodic Arc/Unbalanced Magnetron Sputtering Technique
P.Eh. Hovsepian, Y.N. Kok, A.P. Ehiasarian (Sheffield Hallam University, United Kingdom); A. Erdemir (Argonne National Laboratory); I. Petrov (Frederick Seitz Materials Research Laboratory\University of Illinois); W.-D. Münz (Sheffield Hallam University, United Kingdom)

Nanoscale multilayer C/Cr coatings (bilayer thickness, Δ =1.6 nm) were produced by the combined steered cathodic arc/ unbalanced magnetron deposition technique. The mirror-polished M2 substrates were treated by Cr+ ion etching/ implantation followed by the deposition of a 0.2 µm thick CrN base layer. A 1.6 µm thick C/Cr multilayer coating was then deposited by non-reactive unbalanced magnetron sputtering while rotating the substrates in front of three graphite and one Cr target. During the multilayer deposition, a bias potential of -75 V was applied to the substrates. The ion flux measured by a flat electrostatic probe was 1.2 mAcm -2 and the deposition rate was 0.4 µmh-1, which resulted in ion-to-neutral ratio of Ji/Jn = 11.

XTEM diffraction- and Z-contrast imaging investigations revealed a novel nanostructure in which the basic nano-lamellae obtained as a result of substrate rotation in front of the C and Cr targets were modified by ion-irradiation induced nanoclumnar structure. The intense ion-irradiation of the immiscible film components caused local enrichment of Cr and C that propagated in the growth direction resulting in Cr-rich nanocolunms separated by C-rich boundaries.

Tribological studies of the composite Cr/C coatings were conducted using a pin on disk apparatus under a load of 5 N, at velocities of 0.13 to 0.15 and for distances of ~ 500 m in dry nitrogen (~ 0% humidity) and open air (30% relative humidity). Results indicated that the Cr-C composite coatings provided friction coefficients of 0.7-0.8 in dry nitrogen while the values were significantly lower in open air, 0.21 to 0.24, during sliding against both the coated and uncoated balls. In air a transfer film was present on the sliding ball surfaces and the wear of coated and uncoated surfaces was low. Critical load values exceeding Lc = 75 N were measured in scratch test, showing excellent adhesion of the coating.

11:50 AM B1-11 MAX-phase Ti3SiC2 Coatings for Engineering Components
P. Eklund, J. Emmerlich, H. Högberg, J. Birch (Linköping University, Sweden); H. Ljungcrantz (Impact Coatings AB, Sweden); P. Isberg (ABB Group Services Center AB, Sweden); U. Jansson, J.-P. Palmquist, O. Wilhelmsson (Uppsala University, Sweden); L. Hultman (Linköping University, Sweden)

The Mn+1AXn-materials are newly discovered ceramics with unique properties, as reported for the bulk materials1. An example is Ti3SiC2, which exhibits typical metallic properties (e.g., low resistivity) in combination with ceramic attributes such as high hardness, oxidation resistance and self-lubrication. Calculations for the electronic and mechanical properties of this phase2,3 have further promoted the interest for surface engineering applications. Recently, we showed that single crystal Ti3SiC2 films can be deposited on MgO(111) substrates at growth temperatures below 1000°C, using three different d.c. magnetron sputtering processes4,5.

We present a study on the growth of Ti-Si-C as a function of substrate temperature and substrate bias on different substrate materials including single crystals and engineering components. We evaluate the phase composition, phase stability and microstructure evolution in films grown by magnetron sputtering from individual Ti, Si and C targets as well as from a Ti3SiC2 compound target. Analysis with SEM, TEM, XRD, XPS and nanoindentation show that well-defined films of different microstructure ranging from epitaxial (at T>700°C) to nanocrystalline/amorphous (below 600°C) can be deposited with a smooth, nodular surface morphology. Electrical measurements yield contact resistances below 100µΩ.

1M.W. Barsoum, Prog. Solid St. Chem. 28 (2000) 201-281.

2R. Ahuja et al., Appl. Phys. Lett. 76 (2000) 2226

3B. Holm et al., Appl. Phys. Lett. 79 (2001) 1450

4J.-P. Palmquist et al., Appl. Phys. Lett. 81 (2002) 835

5T. Seppänen et al., Proc. 53rd Ann. Meet. Scand. Soc. Electron Microscopy (Ed. J. Keränen and K. Sillanpää, Tampere University, Finland, ISSN 1455-4518, 2002), p.142.

Time Period ThM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2003 Schedule