Papers

ICMCTF2009 Session D2-2: Diamond and Diamond-Like Carbon Materials

Monday, April 27, 2009 1:30 PM in Room Royal Palm 4-6

Monday Afternoon

Start	Invited?	Item
1:30 PM		D2-2-1 Raman Analysis of DLC Coated Engine Components with Complex Shape: Understanding of Wear Mechanisms O. Jarry (Sorevi); C. Jaoul, P. Tristant, M. Colas, T. Merle-Mejean, C. Dublanche-Tixier (University of Limoges, CNRS, SPCTS, France) DLC films such as amorphous hydrogenated carbon films (a-C:H) are presented as one of the best solutions to reduce friction in internal combustion engines and increase the lifetime of the mechanical parts, e.g. the valve train components. Many authors have already carried out tribological tests on flat samples including Raman analysis of the wear tracks. However very few studies dealt with tests realized in the real engine conditions, although DLC coatings are very sensitive to the working conditions. The originality of this work was to perform Raman analysis directly on complex-shaped mechanical parts after being used in real engines. DLC films were deposited by r.f. PACVD in an industrial scale reactor. Adhesion of the films was improved by the interlayer system between the steel sample and the DLC film. First, an overall characterization of the DLC films was carried out. Structure of the films was compared using Raman spectroscopy. Then tribological tests were conducted in unlubricated and lubricated conditions. Raman analysis of the wear tracks was also realized to check the stability of the DLC structure. Finally, Raman spectroscopy was performed directly on real parts with complex shapes. Mechanical parts showing different wear morphology were analyzed. A particular attention was paid to interactions with the Raman signal of the interlayer system. Different kinds of wear mechanisms were identified using this Raman analysis. Unusual high wear rate of the DLC layer were explained by the graphitization of the DLC structure. The knowledge of the various wear mechanisms allowed us to improve the wear resistance of the parts.
1:50 PM		D2-2-2 Hydrogen-Free Hard Amorphous Carbon Coatings: Properties by Cathodic Vacuum Arc Evaporation and Magnetron Sputter Deposition M. Stueber (Forschungszentrum Karlsruhe, Germany); J. Vetter (Sulzer Metaplas GmbH, Germany); H. Leiste, S. Ulrich, C. Ziebert (Forschungszentrum Karlsruhe, Germany); J. Mueller, G. Erkens (Sulzer Metaplas GmbH, Germany) Basic research and industrial development of diamond like carbon coatings (DLC) have been carried out since decades with regard to their exceptional properties. Different types of DLC coatings (usually hydrogenated amorphous carbon coatings, a-C:H:Me, a-C:H:X) deposited by reactive processes in carbon gas atmospheres have, therefore, been adapted in a large number of industrial applications. Significant progress in the PVD deposition of hard, hydrogen-free amorphous carbon coatings is achieved by applying both tailored magnetron sputtering and improved cathodic vacuum arc processes. Coatings of high surface quality, reduced droplet contamination, low intrinsic stress values, excellent adhesion and hardness values up to 60 GPa with a thickness up to several microns are deposited on silicon and cemented carbide substrates with a new Metaplas MZR304RF hybrid PVD deposition equipment. Results on the laboratory scale deposition experiments, on the thin film microstructure an d properties will be presented. Constitution analyses of the coatings, in example by Raman spectroscopy, and various mechanical characterization methods including nanoindentation, will be described. Scale-up measures and the technical potential of the films, for example in tooling applications and components, will be discussed.
2:10 PM		D2-2-3 Non-Destructive Characterization of Carbon Films A. Ferrari (University of Cambridge, United Kingdom) The availability of reliable characterization tools for carbon films down to a few atomic layers’ thickness is one of the most decisive factors for technology development and production. In particular, non-destructive techniques are preferred. I will review the use of x-ray reflectivity, surface acoustic waves, and Raman spectroscopy to characterize carbon films in terms of density, thickness, layering, elastic constants, roughness, structure, and chemical composition. Raman spectroscopy, in particular, allows the assessment of most of the materials properties, even if indirectly. The measurement of thermal conductivity of carbon films will also be discussed.
2:50 PM		D2-2-5 Characterisation of a Plasma Beam Source During Duplex Treatment of High Speed Steel for Depositing DLC Coatings M. Fenker, M. Balzer, N. Bermayer (Forschungsinstitut Edelmetalle & Metallchemie, Germany); M. Rinke, M. Stüber, S. Ulrich, J. Ye (Forschungszentrum Karlsruhe GmbH, Germany) Plasma characterisation methods have been utilised to study a duplex process, consisting of plasma nitriding of high speed steel (HSS) and subsequently depositing a DLC (a-C:H) coating. Both treatments are performed by using a plasma beam source. For the plasma nitriding a gas mixture of N₂/H₂ was used. The nitriding duration was varied and the substrate temperatures ranged from 400 to 500°C. The subsequent DLC deposition was performed at 100°C with acetylene as precursor gas. The formation of a white layer could be avoided by suitable adjustment of the process parameters, resulting in well-adherent DLC coatings for nitriding depths ≥ 20 µm. Plasma characterisation methods – like optical emission spectroscopy, mass spectroscopy, Langmuir probe, electrical double probe, retarding field analyser and Faraday cup measurements – have been conducted to understand the influence of the plasma parameters on the nitriding behaviour and t he DLC film growth. The hardness of the a-C:H coatings was in the range of 1200 – 3000 HV, decreasing with increasing acetylene flow due to a decrease of the kinetic energy of the C_xH_y molecules impinging on the growing film surface. Raman spectroscopy showed a shifted G-peak at 1530 cm^-1 and a shifted D-peak. The friction coefficients in dry pin-on-disk tests with an Al₂O₃ counterpart and a load of 10 N were in the range of 0.05 and 0.10. In conclusion, it could be shown that the duplex treatment with a plasma beam source has been optimised by correlating the plasma parameters with the properties of the coated parts.
3:10 PM		D2-2-6 Correlation of Plasma Properties and Microstructures of DLC Films Deposited by Laser Induced High Current Pulsed Arc J.-B. Wu, C.-Y. Chen (Industrial Technology Research Institute, Taiwan); M.-Y. Li (National Nano Device Laboratories, Taiwan); M.-S. Leu, A.-K. Li (Industrial Technology Research Institute, Taiwan) Hydrogen free diamond-like carbon (DLC) coatings were deposited on Si(100) and stainless steel substrates by laser induced high current pulsed arc (LIHCPA) system with different deposition partial pressure. The microstructures and hardness behavior of DLC films were identified by the instrumental analyses such as scanning electron microscopy, X-ray photoelectron spectroscopy and nano-indentation. In order to investigate the correlations between the microstructures of films and plasma characteristics, a quadrupole plasma analyzer was used to identify the positive ion energy distribution (IED). Meanwhile, the pulse arc current of 4 kA was applied to the carbon target to deposit the DLC films with high density and hardness. It was found that the deposition partial pressures affected not only the hardness and sp³ content of the films but also the carbon ion energy. The results clearly showed that when the deposition partial pressure increased from 3×10^-3 Pa to 1 Pa, the hardness decreased from 52 GPa to 27 GPa, and also the sp³ fraction of the DLC films measured by XPS would increase from 47 % to 61 % accordingly. Moreover, by taking deposition partial pressure of 3×10^-3 Pa into consideration, the results revealed that the plasma species generated by the carbon target were verified as C⁺, C²⁺, C₂⁺ and C₃⁺ among which that the C⁺ ion energy can achieve the energy of 50 eV.
3:30 PM		D2-2-7 Amorphous Carbon Deposited By Sputtering And Plasma Enhanced Chemical Vapor Deposition Without Vacuum Pumping During Deposition G.A. Viana, F.C. Marques (University of Campinas, Brazil) Amorphous carbon film films have been deposited by a large variety of deposition method. All of them use a flow of certain gas for the deposition of the films. Plasma enhanced chemical vapor deposition (PECVD), for instance, usually uses a flow of methane into the chamber and pumped with a vacuum pump during deposition. This gas is then disposable to the atmosphere. For films deposited by sputtering, usually an argon gas flow is adopted for sputtering a graphite target. In this case a large amount of argon is also released to the atmosphere. In this work we propose the deposition of amorphous carbon by sputtering and PECVD without vacuum pumping during deposition. For that purpose the deposition chamber is prior pumped down to about 10-8 Torr in order to clean the chamber walls, avoiding the releasing of adsorved contaminating gases during deposition. The chamber is then closed and argon (for sputtering) or methane (for PECVD) is introduced into the chamber until a cert ain pressure. The films are then deposited without further supply of argon or methane. Graphitic-like amorphous carbon was obtained by sputtering and diamond- and polymeric-like carbon films were obtained by PECVD. Visible and infrared transmission spectroscopy, nanohardness, stress and Raman measurements reveal that the properties of the films are similar to those reported for films deposited by the conventional procedure. Ones conclude that this technique can be used to reduced gas waste and thus contributing to a sound environment.
3:50 PM		D2-2-8 Thermal Annealing Effect on Tribological, Electrical, and Corrosion Properties of DLC Coatings L. Wang, Z.J. Peng (University of Windsor, Canada); J. Housden, E. Spain (Tecvac Ltd.); X. Nie (University of Windsor, Canada) Diamond-like Carbon (DLC) coatings usually have high hardness, chemical inertness and high electrical resistivity. These properties make them attractive in a wide range of applications such as engineering tools, dies, electronic devices and even medical and food packaging field. Especially, due to their remarkable tribological properties (low friction coefficient and wear rate), DLC coatings have become one of the important coatings applied as protective layer on engineering tools. However, DLC coatings are likely graphitized at high working temperatures. Many research efforts have been made to investigate the effect of annealing temperature on coating structure, mechanical and tribological properties. In this study, besides the mechanical and tribological properties, electrical conductivity and corrosion protective properties of annealed DLC coatings were investigated. The annealing treatments were performed in air for 1 hour at the temperatures ranged from 200 to 600^oC. Nanomechanical test instrument, pin-on-disc tribometer, potentiodynamic electrochemical tests and interfacial contact resistance tests were used to study the mechanical, tribological, corrosion protective and electrical conductivity properties of DLC coatings before and after annealing. The investigation results were discussed in terms of feasibility of DLC coatings for various applications.