ICMCTF2001 Session E5/D4-1: Properties and Applications of Diamond, Diamondlike and Related Coatings

Tuesday, May 1, 2001 8:30 AM in Room California

Tuesday Morning

Start	Invited?	Item
8:30 AM	Invited	E5/D4-1-1 Development and Tribological Applications of Carbon Based Coatings A. Hieke, L. Schäfer, K. Bewilogua (Fraunhofer Institute for Surface Engineering and Thin Films (IST), Germany) Research and development in the field of carbon based coatings have resulted in a class of hard and wear resistant thin films with very different properties. The most well-known carbon based coatings are crystalline diamond films and amorphous "hydrogen-free" ta-C coatings (H < 1at%), hydrogenated amorphous carbon a-C:H (H < 50 at%), metal-containing Me-C:H coatings and DLC coatings modified by adding different non-metallic elements (a-C:H:X). We will present different deposition techniques to prepare pure diamond, DLC and modified DLC films. Diamond films are deposited by hot filament (T = 600 - 1000°C) chemical vapour deposition (HFCVD), whereas amorphous carbon films are prepared by plasma assisted chemical vapour deposition (PECVD) or physical vapour deposition (commonly magnetron sputtering) at low substrate temperatures (T < 200 °C). The properties of such coatings are high hardness, high wear resistance, a very low friction coefficient (e.g. vs. steel), electrical conductivity or insulation, an adjustable surface energy and a high chemical inertness. The possibility to tailor the properties of the deposited carbon films by using different techniques opens a wide field of different technical applications.
9:10 AM		E5/D4-1-3 Nano-Wear-Resistance of Amorphous Carbon Nitride Thin Films Prepared by Shielded Arc Ion Plating O. Takai, H Saze, T Kawaguchi, H. Sugimura (Nagoya University, Japan) Amorphous carbon nitride (a-C:N) thin films show excellent mechanical properties such as low friction and high wear resistance like diamond-like carbon (DLC) films. The a-C:N films, therefore, are very useful for the tribological coatings on various industrial substrates. This paper reports on the nano-wear-resistance of the a-C:N films prepared by shielded arc ion plating (SAIP) in comparison with that of the DLC films prepared by the same method. The nano-wear-resistance of films was studied with a Hysitron nanoindentation system interfaced with an AFM. First each film surface was scanned with the Berkovich-type diamond tip. The tip scanning was repeated 30 times in a 1 µm-square region with 512 lines at a scanning rate of 2 µm/s. Next the wear profile of the film was obtained in the AFM mode using the identical Berkovich tip. The wear depth was determined from this wear profile. We could distinctly detect a wear depth in sub-nm scale. Wear depths of control substrates such as Si and quartz were both about 15 nm. The a-C:N films were prepared at various dc substrate bias voltages ranging from 0 to -500 V. The a-C:N film prepared at 0 V was least wear resistant among the deposited a-C:N films reflecting its lowest hardness of 10 GPa. The wear depth of this film was about 3 nm. The biased a-C:N films became more wear resistant. Particularly the a-C:N film prepared at -300 V showed high wear resistant because its wear depth was almost zero in spite that the much harder DLC films were obviously worn under the same wear test condition. We discuss the origin of this high wear resistance in connection with the XPS measurement of the a-C:N films.
9:30 AM		E5/D4-1-4 Influence of Different Plasma Confinement Conditions on Mechanical and Tribological Properties for Deposition of Me-DLC Coatings C. Strondl, G.J. van der Kolk, T. Hurkmans, W.S. Fleischer (Hauzer Techno Coating Europe BV, The Netherlands); N.M. Carvalho, J.Th.M. de Hosson (University of Groningen, The Netherlands) A series of different metal containing diamond like carbon coatings (Me-DLC) have been produced by unbalanced magnetron sputtering using a Hauzer HTC-1000 production system. For this series of Me-DLC coatings, sputtering from WC targets have been used to form W-C:H coatings. Previous work in this field have shown a great influence on mechanical and tribological properties when the microstructure of W-C:H coatings have been changed. The W-C:H coatings in this investigation have been deposited under different plasma confinement conditions by changing the degree of unbalancing of the magnetic field in the magnetrons. The plasma confinement by the magnetic field lines surrounding the substrate table controlled the plasma assisted deposition process directly from the hydrocarbon gas phase (in this case actylene). This influenced the W-C:H coatings microstructure and in turn the mechanical and tribological properties, which were investigated in this paper. Properties like adhesion (scratch testing), hardness and E-modulus (nano indentation), fatigue resistance (impact testing), coefficient of friction (pin-on-disc) and wear resistance (ball grinding test) were studied. Detailed high-resolution TEM has been carried out to analyse the microstructure of the different W-C:H coatings. The microstructure was correlated to the mechanical and tribological properties.
9:50 AM		E5/D4-1-5 Tribological Characterisation of Diamond-Like Carbon Coatings on Co-Cr-Mo Alloy for Orthopaedic Applications D. Sheeja, B.K. Tay, S.P. Lau (Nanyang Technological University, Singapore); L.N. Nung (Department of Orthopaedic Surgery, Singapore) Medical grade ultra-high-molecular-weight- polyethylene (UHMWPE), which articulate well against metal, typically Co-Cr-Mo alloy, is commonly used in total joint replacements. The clinical performance of the components made of UHMWPE, is considered very good except for the concern about their wear. The adverse tissue reaction due to these wear particles is found to be the major factor responsible for the loosening or failure of the implant. Development of new and/or improved material pair, which produces least wear, is one of the solutions for a long lasting orthopedic implant. Diamond-like carbon (DLC) coatings have received enormous attention as a wear resistance coating, due to its high hardness. In addition to that, DLC coating has many other superior properties as an implant material such as biocompatibility and chemical inertness. The properties of DLC coatings can vary widely depending on the deposition technique as well as the deposition parameters. The filtered cathodic vacuum arc (FCVA) technique has been proven to be an efficient method of producing high quality DLC coatings. Some studies claim that the DLC coated stainless steel sliding against the same reduces the wear rate to a very low value. However, any incidental failure of the coating can cause drastic friction and wear. Hence the present study focuses on the surface modification of the existing implant materials. The tribological characterization of Co-Cr-Mo alloy with and without DLC coating sliding against UHMWPE counter-surface in different tribological environments such as ambient air, DI (de-ionized) water and SBF (simulated body fluid), is discussed in the paper. It is observed that the DLC coating improves the wear resistance of CCM alloy to about 10 times and hence such coating can be used to improve the life of artificial joints. The influence of surface roughness on the characteristics of the DLC coatings has also been investigated.
10:10 AM		E5/D4-1-6 Role of Third Bodies in Friction and Failure of Diamond-Like Nanocomposite Coatings Studied by In Situ Raman Tribometry T.W. Scharf, I.L. Singer (U.S. Naval Research Laboratory) The friction and wear life of amorphous diamond-like nanocomposite (DLN) coatings (C:H:Si:O) have been investigated using a homebuilt in situ Raman tribometer. Tests were performed under reciprocating sliding against stationary sapphire hemispheres in dry (4% RH) and moist (40-50% RH) air at contact stresses from 0.7 to 1.1 GPa. The friction coefficients fell from starting values of ~0.2 to steady state values of 0.04-0.06 in 50 to 200 cycles for all humidity testing conditions. However, in moist air, friction coefficients either remained steady with occasional spikes, or rose and fell gradually (over 1000 cycles) by ~50%. By contrast, in dry air, friction coefficients remained steady but the coatings failed early as the friction coefficients increased rapidly to > 0.2. In situ video observations of the sliding contact showed that in dry and moist air, the low steady state friction values corresponded to interfacial sliding (velocity accommodation mode) between the coating and a film that transferred to the Hertzian contact spot on the sapphire counterface. The friction spikes were associated with the dynamic rheology of the transfer film and other third bodies in the contact: friction increased when the film was worn away but decreased when the film recovered. The shorter wear life in dry air corresponded to the loss of the transfer film without recovery. In situ Raman spectroscopy identified the transfer films as carbon-based, but with higher frequency shifts and narrower bandwidths of the graphitic "G" and disordered "D" peaks than the DLN coating itself. Complementary ex situ analysis and profilometry of the wear scars are also reported, and third body processes that influence the tribological behavior are discussed.
10:30 AM	Invited	E5/D4-1-7 Deposition, Structure, Mechanical Properties and Tribological Behavior of Polycrystalline to Smooth Fine-Grained Diamond Coatings L. Vandenbulke, M.I. De Barros (CNRS - LCSR, France) Polycrystalline and smooth fine-grained diamond (SFGD) coatings are deposited at 600°C on Ti alloys or Ti-coated surfaces by a two-step microwave PACVD procedure using CO-H₂ or CO₂-CH₄ during the second step. Optical emission spectroscopy and mass spectrometry reveal important differences between the plasma species produced in the different conditions including the deposition from CH₄-(Ar-H₂). SEM, AFM, XRD, TEM, visible and UV Raman spectroscopy allow to characterize the surface roughness, the diamond quality (sp³/sp² ratio) and the microstructure of the coatings. The roughness can be decreased from about 120 nm (r.m.s.) for polycrystalline coatings to 35 nm for SFGD coatings while the incorporation of sp²-hybridized carbon is only slightly increased. It can be further lowered to the 30-15 nm range while the sp²-carbon incorporation increases. Note that this low roughness is independent of the coating thickness due to the microstructure. The difference of microstructures and diamond purity influence the hardness and Young's modulus of the coatings, measured with an ultra-low load micro-indenter and by Brillouin scattering. The residual stresses are deduced from the Raman spectra. Finally the tribological behavior in ambient air of 100Cr6 steel, uncoated and diamond-coated Ti-6Al-4V alloy sliding against all coating types including some polished polycrystalline coatings has been studied with a rotating pin-on-disk tribometer. The strong influence of the surface roughness has always been evidenced. The counterface materials present however different tribological behaviors which also depend on the diamond quality. Different friction and wear mechanisms are discussed as a function of these parameters. The advantages of SFGD with respect to polycrystalline coatings are emphasized. Very low wear rates of the alloys and low friction coefficients, in the 0.05 - 0.1 range, were obtained for the smoothest coatings, even under fairly heavy load.
11:10 AM		E5/D4-1-9 A Study of Diamond-Like Carbon Films Deposition on a High Nitrogen Stainless Steel A. Di Schino, L. Valentini, J.M. Kenny (University of Perugia, Italy) Nickel containing austenitic stainless steels have been indispensable for the progress of technology during the last 80 years. Due to the cost of nickel and to the prospected possibility of allergic reactions caused by this element, more and more laboratories and industries are trying to develop a new class of austenitic stainless steels without nickel. Nitrogen alloyed austenitic stainless steels have shown to exhibit attractive properties as high strength and ductility, good corrosion resistance and reduced tendency to grain boundary sensitation. Generally as it has been shown, the mechanical and tribological characteristics of the steels can be greatly improved by surface treatment, for example by plasma enhanced chemical vapour deposition (PECVD). In this sense a deep understanding of the coating process is then needed. The study is here focused on the coating of a high nitrogen stainless steel by mean of both diamond like carbon (DLC) and DLC nitrogen doped thin films. In this study the mechanical and tribological properties of various coatings are investigated to generated a basis of data for comparison that should facilitate the selection of the DLC coating for particular application. Scratch test is used to determine the adhesive strength of the coatings. Wear tests are conducted to determine the wear rate of the coated samples in comparison to the untreated ones. The treated samples were investigated by Auger electron microscopy and x-ray photoelectron spectroscopy to determine the chemical interactions near the surface.
11:30 AM		E5/D4-1-10 Influence of Atomic Hydrogen Bombardment on the Diamond/DLC Couple Tribological Behaviour M. Schmitt, D Paulmier, T. Le Huu (LPMM-ERMES, CNRS UMR 7554, France) The technological evolvements over the last decade highlighted the importance of the machining ; its use, always increasing, leeds to the necessity of its cost lowering, that means a pieces tooling at very high speed and directely in final surface state. A low wear rate combined with an extreme hardness are two of the excellent mechanical properties of the diamond and DLC coatings which make them suitable for machining, and more particularly for coated the cutting tools. It was then interesting to study whether diamond and DLC coatings can present lubricating characteristics in these kind of applications. The tribological behaviour of the diamond/DLC couple was consequently studied : diamond was obtained by flame process whereas DLC coatings were deposited on steel discs by dc-CVD process ; these coated discs were then submitted to an atomic hydrogen bombardment. The friction tests were realised under vacuum and hydrogen ; the role of the atomic hydrogen on the surface modifications and on the transferred layers formation as well as its influence on the friction coefficient were clearly shown. Scanning Electron Microscopy observations and Energy Dispersive Spectroscopy analyses were used to reveal the surfaces changes ; Raman Spectroscopy was carried out to highlight the coatings evolution.
11:50 AM		E5/D4-1-11 Thickness Uniformity of Free-Standing Diamond Synthesized by "Trumpet Bell" Flame Method T. Le Huu, M. Schmitt, D Paulmier (LPMM-ERMES, CNRS UMR 7554, France) Free-standing diamond layers can be produced in large sizes by various deposition methods: microwave, radio-frequency and combustion flame etc.,. The advantage of the combustion flame method is to obtain high growth rates of diamond deposition, however the poor uniformity of thickness that has not yet solved. In this paper, free-standing diamond films are deposited using combustion flame method on polycrystalline copper substrates. Studies on the nucleation and growth of diamond show that copper is a promising substrate material for the free-standing diamond films preparation. By use the "trumpet bell" welding torch developed by ERMES group has made possible to deposit diamond on large area with very good uniformity. In our experiments, high quality free-standing diamond films of 30-40 µm thickness and of 10 mm diameter were obtained after 20 minutes deposition. The quality and the uniformity of the free-standing diamond films are observed by Scanning Electron Microscopy (SEM) and analysis by Raman Spectroscopy (RS); profilometry. The four points probe method is also used to measure the resistivity of the film as a function of the temperature (?-T) during the heating and cooling phases to the room temperature (RT).