ICMCTF2005 Session B1-2: Sputtering Coatings and Technologies

Thursday, May 5, 2005 1:30 PM in Room Golden West
Thursday Afternoon

Time Period ThA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2005 Schedule

Start Invited? Item
1:30 PM B1-2-1 The Structure and Properties of Chromium Diboride Coatings Deposited by Pulsed Magnetron Sputtering of Powder Targets
M. Audronis (The University of Sheffield, United Kingdom); P.J. Kelly, R.D. Arnell (University of Salford, United Kingdom); A. Leyland, A. Matthews (The University of Sheffield, United Kingdom)
Boride coatings are attracting increasing interest, due to the fact that they combine high hardness with good wear and corrosion resistance. These coatings are often deposited by sputtering hot-pressed, or sintered ceramic targets. However, targets of this nature can be prone to cracking and, since the user is limited to a single composition per target, do not offer the opportunity to readily vary film stoichiometry. TiB2 and ZrB2 have been widely studied. Far less attention has been paid to chromium diboride, although it is recognised to offer superior performance in corrosiveâ?"wear environments. In this study, therefore, CrB2 coatings were deposited by the pulsed magnetron sputtering of loosely packed blended powder targets. This work was carried out in a deposition system specifically designed for the use of powder targets, and the effectiveness of this approach has been previously demonstrated through the production of a number of different multi-component coating materials. The ability to conveniently vary the target composition allowed the production of stoichiometric, crystalline CrB2 coatings. The coatings have extremely dense, defect-free structures, high hardness (>30GPa) and good tribological and corrosion resistant properties, which are summarised in this paper. Comparisons of coatings produced by continuous DC and pulsed DC, under otherwise identical conditions, clearly demonstrate the very significant impact that pulsed processing had on the structure and properties of these coatings.
1:50 PM B1-2-2 Structural, Mechanical and Tribological Properties of CrAlN Coatings Deposited by Reactive Unbalanced Magnetron Sputtering
X.Z. Ding, X.T. Zeng (Singapore Institute of Manufacturing Technology, Singapore)

TiAlN coatings exhibit high hardness and oxidation resistance over TiN, and have attracted substantial research and industrial interests. However, their tribological properties show insignificant improvement due to their unimproved high friction coefficient. Recently, CrAlN coatings had been reported exhibiting even higher oxidation resistance than TiAlN. CrN coatings are known to be superior to TiN in corrosion and wear resistances, friction behavior, and toughness. Therefore, in comparison with TiAlN, better tribological properties of CrAlN coatings and their promising applicability in high speed machining could be expected.

In this work, a series of Cr1-xAlxN coatings with 0≤x≤0.4 were deposited on high speed steel (HSS) substrates by a reactive unbalanced magnetron sputtering technique from Cr and Al elemental targets in an Ar+N2 mixture atmosphere. During coating deposition, a negative bias was applied onto the substrates, but no deliberate heating was applied. The structural, mechanical and tribological properties of the as-deposited CrAlN coatings were characterized by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), nanoindentation, and pin-on-disc tribometer experiments. For the pure CrN coating sample, all of the major XRD peaks arise from the HSS substrate. With the addition of aluminum, the CrAlN coatings gradually crystallize in the pseudo binary, rocksalt-type cubic structure, showing a (111) preferential orientation. With the increase of aluminum content, the hardness of the CrAlN coatings increases gradually from about 18 GPa up to a maximum value of 30 GPa, and then drops down slightly with increasing aluminum content further. The wear resistance of all the CrAlN coatings are much better than that of the pure chromium nitride coating deposited under similar conditions.

2:10 PM B1-2-4 Properties of Sputtered a-Si3N4/MoNx Nanocomposite Coatings with High (>20 at.%) Si Content
J. Musil, P. Dohnal, P. Zeman (University of West Bohemia, Czech Republic)
Thermal stability of properties and high-temperature oxidation resistance is one of the fundamental questions of hard nanocomposite coatings.Recent experiments have shown that very perspective from this point of view is a new family of a-Si3N4/MeNx composites with a high(≥40 vol.%)content of a-Si3N4 phase.This paper reports on structure,phase composition and high-T oxidation resistance of sputtered MoSiN films.These films were dc reactively sputtered using an unbalanced magnetron equipped with a MoSi2 alloyed target in a mixture Ar and N2.A continous increase of pN2 from 0 to 0.6 Pa makes it possible to produce two groups of composites:(1)(Mo,Si)+a-Si3N4 and (2)a-Si3N4+MoNx.The composites of the first group are crystalline and contain a low amount of a-Si3N4 phase.On the contrary,the composites of the second group are composed of nc-MoNx grains embedded in a-Si3N4 matrix,which dominates in the film.It is shown that the oxidation resistance of a-Si3N4/MoNx composites depends on the phase composition of composite and the thermal stability of individual phases.The highest high-T oxidation resistance exhibit a-Si3N4/MoNx>1 composites with high(≥50 vol.%)amount of a-Si3N4 phase.The oxidation of these films at annealing temperatures Ta≥900C results in a very small loss of weight Δm=0.01 mg/cm3.This loss of weight is due to a decomposition of MoNx>1-Mo+N(g) and the formation of volatile MoOx oxide.The loss of weight does not increase with increasing Ta up to 1300C.This fact clearly demonstrates the high-T oxidation resistance of the a-Si3N4/MoNx>1 composite.The temperature Ta=1300C is not a physical limit of high-T oxidation resistance of the a-Si3N4/MoNx>1 composite but only the limit of Si substrate used in annealing experiments.
2:30 PM B1-2-5 A New Route Towards the Scaling-Up of Solid Lubricant TiC-C Coatings
M. Stüber, S. Ulrich, U. Albers (Forschungszentrum Karlsruhe, Germany); A. Schintlmeister, P. Wilhartitz (Plansee AG, Austria)
Carbon-based solid lubricant coatings such as TiC-C are attracting more and more interest for industrial applications since the knowledge on the relation between growth parameters, microstructure, properties and performance is increasing. TiC-C thin films composed of nanocrystalline TiC and amorphous carbon phases provide multifunctional property profiles including high wear resistance and low friction. The scaling-up of TiC-C coatings by means of magnetron sputtering will be reported. Various deposition methods, such as reactive and non-reactive magnetron sputtering processes will be compared in terms of the coatings microstructure, properties and performance. A new process of non-reactive magnetron sputtering on production level using innovative ceramic composite targets of individual compositions will be presented. Applying these new targets very stable, reproducible and easily to control and monitor deposition processes are available. Advanced coating concepts based on this new route of carbon-based solid lubricant nanocomposite coatings will be discussed.
2:50 PM B1-2-6 Thermal Stability of MAX Phase Ti3SiC2 Thin Films Prepared by DC Magnetron Sputtering
J. Emmerlich, H. Högberg, P. Eklund (Linköping University, Sweden); O. Wilhelmsson (Uppsala University, Sweden); H. Willman (University of Leoben, Austria); U. Jansson (Uppsala University, Sweden); L. Hultman (Linköping University, Sweden)
Metallic ceramics of the so-called Mn+1AXn phases (M: early transition metal; A: A-group element; X: Carbon or Nitrogen; n=1-3) are of growing interest for functional thin film materials. They can be described as nanolaminates with MX slabs interleaved with atomic layers of A-elements. Typically, these phases are electrically and thermally well conducting and exhibit low friction with high resistance against oxidation and thermal shock. In this study the thermal stability of as-deposited Ti-Si-C films was investigated using x-ray diffraction with in-situ annealing facilities under ultra-high-vacuum conditions and differential scanning calorimetry. Single phase and epitaxial thin films of Ti3SiC2 and Ti4SiC3 were grown on MgO(111) and Al2O3(0001) substrates by DC magnetron sputtering from three single element targets at substrate temperatures (TS) between 700°C and 1000°C. Initial results show phase stability of Ti3SiC2 up to approximately 1200°C. For higher annealing temperatures, diffusion of Si and C resulted in the decomposition of the ternary MAX phase into binary TiC and SiC and/or possible solid solutions between Ti, Si and C. This is notably less than the ≥2000°C stability stated for Ti3SiC2 bulk material. The difference in thermal stability between thin film and bulk material is ascribed to the presence of an interface to vacuum in the former case. Additionally, much smaller film dimensions causing decreased diffusion lengths of the elements compared to bulk material influence the phase stability. Furthermore, results from XRD and TEM investigations in films grown at TS≤700°C will be presented.
3:10 PM B1-2-8 The Influence of Nitrogen Contents on Magnetic Properties of Fe-Co-Ni-based Multi-component Thin Film
H.-K. Chen, S.-H. Lee, J.G. Duh (National Tsing Hua University, Taiwan)
An extensive magnetic characteristic of the Fe-Co-Ni-based magnetic thin films prepared by the RF-sputtering is presented. The relationships between the magnetic properties and the magnetic domain structures of the coatings under various annealing temperatures measured by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM) respectively are discussed. Various annealing temperatures and alloy composition in the thin films result in the different domain structure, which in turn influence magnetic properties of the magnetic films. The domain structure with a width around 0.25 µm in the as-deposited magnetic thin film without nitrogen doping exhibits an irregular figure. With varying the nitrogen content, the distribution of the domain structure changes from maze-like to strip-like shape. Similar transformation in the domain structure with respect to the variation in annealing temperatures is also revealed.
3:30 PM B1-2-9 Tarnishing Resistance of Silver Thin Films
M. Doriot-Werlé, P-A Gay, P.-A. Steinmann, O. Banakh (University of Applied Sciences, Switzerland)

Ag-Pd decorative coatings are supposed to provide better tarnishing resistance as compared to pure Ag, while keeping the same optical and mechanical properties. Palladium has similar optical appearance as silver, and forms a thin protective oxide surface layer. For this reason, small incorporation of Pd in Ag could improve its tarnishing resistance.

Thin Ag-Pd films were deposited by magnetron co-sputtering from Pd and Ag targets on stainless steel substrates. The Ar working gas pressure, Ag and Pd target power, substrate temperature were varied in order to modify the chemical composition of the films and optimise their properties.

The optical properties of the films were evaluated by spectroscopic ellipsometry. The reflectivity in VIS of the Ag-Pd films decreases with increasing Pd content and the reflectivity edge becomes less pronounced. For the film with 30 wt.% Pd the reflectivity is 70% which is lower than that of pure Pd. High values of reflectivity (80-95% in VIS) are observed for films with Pd content between 2 and 6 wt.%. The reflectivity (at 633 nm) of Ag-Pd film with 5 wt.% Pd decreases with increasing substrate temperature from 90% (without substrate heating) to 74% (Ts=300°C). High working gas pressure results in a drastic decrease of the specular reflectivity of the films : the reflectivity (at 633 nm) of two films with 15 wt.% Pd deposited at high (4 Pa) and low (0,5 Pa) pressure are 65 and 90% respectively.

The tarnishing resistance was evaluated by sulfidation test. Different Ag-Pd films together with an Ag 925 reference were exposed to ammonium sulfide during 40 min. The color of the samples was measured before and after the sulfidation test by colorimetry (CIELAB). The first results indicate an improvement of tarnishing resistance for Ag-Pd films.

The paper is focused on the relationship between deposition conditions, chemical composition, film morphology and color, mechanical properties and tarnishing resistance of the coatings.

3:50 PM B1-2-10 On the Characteristics of Nano-Scaled Metal and Carbon Thin Films for the Explanation of A Self-assembling Process
W.-Y. Wu, C.-W. Hsu, J.-M. Ting (National Cheng Kung University, Taiwan)
We have reported in a previous paper sputter deposited metal-containing diamond-like carbons (Me-DLC) with self-assembled, nano-scaled alternating layers of metal and carbon (Wan-Yu Wu and Jyh-Ming Ting, "Self-assembled Alternating Nano-scaled Layers of Carbon and Metal", CPL, 388/4-6, 312-315, 2004). We have suggested that the self-assembling process is a result of a catalytic reaction of the metal and the difference between the metal deposition rate and the carbon deposition rate. To further explore the self-assembling process, we have addressed the issue of deposition rate in this study by investigating the characteristics of nano-scaled metal thin films and carbon thin films. The nano-scaled thin films were prepared using the magnetron sputter deposition technique as was used in the aforementioned study. The targets used include Pt, Cu, Ni, Fe, Al, Si, and C. The nano-scaled thin films were deposited under Ar pressures of 5 x 10-2 torr and 5 x 10-2torr, DC powers of 20 W, 100 W, and 200 W, electrode distances of 5 cm, 7 cm, and 10 cm, and various deposition times. The resulting thin films were analyzed for the thickness and n/k values using a ellipsometry The thicknesses determined were used to calculated the deposition rate. The microstructure and crystallinity were analyzed using transmission electron microscopy(TEM); and the surface topography was examined using atomic force microscopy (AFM). The data obtained were compared with the previous results for further understanding of the self-assembling process.
4:10 PM B1-2-11 Effect of Deposition Conditions on Mechanical and Tribological Properties of Nanostructured TiN/CNx Multilayer Films
A. Vyas, K.Y. Li, Z.F. Zhou, Y.G. Shen (City University of Hong Kong, China)
Nanostructured TiN/CNx multilayer films were deposited onto unheated Si(100) wafers and M42 high-speed-steel substrates using unbalanced closed-filed magnetron sputtering in an Ar/N2 gas mixture. The effects of nitrogen concentrations and bilayer thickness periods on the mechanical and tribological properties of these multilayer films were investigated. These multilayer films were characterized and analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Rockwell-C adhesion test, scratch test, pin-on-disc tribometer, and nanoindentation measurements. It was found that the stress of the films was strongly related to their microstructure, which depended mainly on the incorporation of nitrogen in the films. TEM and SEM studies revealed the complete suppression of columnar grain growth in TiN owing to the incorporation of amorphous CNx layers. The crystallinity of TiN and amorphous nature of CNx were also confirmed by HRTEM. By XPS total nitrogen concentrations of up to 20 at.% with the presence of both N-C sp2 and N-C sp3 bonds in CNx were shown. Nanoindentation results showed that at a bilayer thickness period of ~2 nm the hardness of the film was about 37 GPa. The friction coefficient values of the CNx containing 20 at. % nitrogen in multilayers were measured to be in the range of 0.1-0.14. By scratch and Rockwell-C tests, it was also found that the multilayer films (bilayer thickness of ~2 nm and hardness of ~35 GPa) exhibited the best adhesion and cohesive strength. These adhesive properties and wear performance are also explained on the basis of microstructure, mechanical properties and tribochemical wear mechanisms.
Time Period ThA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2005 Schedule