Papers

ICMCTF2008 Session D2-2: Diamond and Diamond-Like Carbon Materials

Wednesday, April 30, 2008 8:00 AM in Room Royal Palm 4-6

Wednesday Morning

Start	Invited?	Item
8:00 AM		D2-2-1 Friction Reduction in the Valve Train With Triondur® Carbon Coating T. Hosenfeldt, Y. Musayev, W. Christgen (Schaeffler Group, Germany) For reducing friction in the sliding contact between the cams of the camshaft and the bucket tappets, the Schaeffler Group is presenting Triondur® Coating Systems, which perform precisely the various requirements of the application. The latest Triondur® coating system is a nanostructured carbon based coating, which is deposited using an environmentally-friendly PVD-/ PACVD- coating process. Especially in the lower speed ranges up to 2000 rpm, the valve train contributes up to 25% of the friction losses in the engine. The presented Triondur® CX⁺ amorphous carbon coating allows for the reduction of friction in the valve train by up to 50% in contrast to uncoated bucket tappet type valve trains. Because of the described excellent tribological and mechanical properties in conjunction with relatively low costs Triondur® coating systems can be applied not only to the valve train, but also to all applications with very high mechanical loads.
8:40 AM		D2-2-3 Friction and Wear Behaviour of Modified ta-C Films V. Weihnacht, H.-J. Scheibe, A. Leson (Fraunhofer IWS - Institute for Materials and Beam Technology, Germany) Hydrogen-free tetrahedral amorphous carbon (ta-C) films with up to 70% sp3-bonds can be deposited by pulsed vacuum-arc discharge from a graphite source. In this contribution standard ta-C-films are compared to modified (t)a-C:X-films, deposited by using different process atmosheres and doped graphite targets. The first kind of modified ta-C was produced by using different partial pressures of argon gas in order to moderate the carbon ion energy. The second modification was done by using nitrogen atmosphere to deposit (t)a-C:N films. Finally, metal-containing (t)a-C:Cu and (t)a-C:W films were deposited from metal containing graphite targets. The different film types were analyzed with respect to hardness, elasticity, intrinsic stress, adhesion strength, chemical and structural constitution, and tribological behaviour both under dry and under lubricated conditions. The friction and wear behaviour was measured in ball-on-disk arrangement. The results are evaluated against the background of different sp3-contents and the chemical influence of doping elements. From these investigations important conclusions can be drawn for the design of ta-C based coating systems. It is shown, that coatings can be optimized and adjusted to the tribological conditions in the application by stack- and multilayer structure.
9:00 AM		D2-2-4 CVD-Diamond Coatings for Highly Demanding Cutting Operations W. Reichert, S. Krysta, O. Oliver, R. Cremer (CemeCon AG, Germany); S.M. Rosiwal (University of Erlangen, Germany) High performance cutting and an increasing amount of composite materials to be machined require on the one hand a general view of the cutting process, workpiece and tool as a uniform process and the need to tailor the coated tool's properties exactly to the specific application. Especially fibre reinforced materials can not be machined with conventional tools, but also other high-tech materials e.g. green compacts, non ferrous alloys, intermetallics, printed circuit boards (PCB) and extremely abrasive Al-Si and Ti-Al alloys require tailored diamond coated tools for reasonable machining operations. All these demands can be met by well to the Co-content adjusted pre-treatment of the cemented carbide tools to guarantee a perfect adhesion and improved interface. Furthermore the morphology of the diamond coatings can be exactly controlled leading to micro- and nano-crystalline as well as multilayered coatings to increase fracture toughness. It is even possible to sharpen diamond cutting edges for machining of wood or chipboards. All possible treatments and processes may be used solely or combined to produce the ideal fitted diamond coated tool for specific application to achieve an optimum performance in cutting operations at reasonable costs. This will be illustrated by selected cutting test results in most demanding applications.
9:20 AM		D2-2-6 DLC Film Deposition on the Inner Wall of the Cylinder Using Hollow Cathode Effect Wth Low Frequency Pulse Power Y.H. Jun, J.E. Lee, K.H. Han, M.S. Park (Plasma Lab, J&L Tech.Co.,Ltd., Korea) Recently it has been hot issue to coat thin film on the inner wall surface of cylinder or tube. Some group reported successful coating on it. Most of them used the techniques delivering the high frequency power such as radio and microwave through an antenna in the inside of cylinder. In this study, we developed a new CVD technique using a hollow cathode effect with the pulse power of relatively low frequency, ~300 kHz, without any antenna to deposit diamond-like carbon(DLC) films on the inner wall of a cylinder (stainless steel of Φ60~110mm and length 200mm). To deposit DLC film on the inner wall, the cylindrical electrodes and insulation plates were placed both sides of the cylinder. Plasma is generated in the inside of cylinder by the pulsed power applied to the electrodes, Hollow cathode Effect, and DLC film resulted in uniform deposition on the inner wall. The discharge characteristics were investigated as changing the frequency of pulsed power. The mechanical properties of DLC film such as hardness, residual stress and friction coefficient were also measured using nano-indentation, stress tester, and tribometer, respectively. This research was supported by a grant(code #: 07K1501-00900) from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Science and Technology, Korea.
9:40 AM		D2-2-7 Classification of Diamond-Like Carbon Films for Industrial Application H. Saitoh (Nagaoka University of Technology, Japan) The objective of this presentation is to provide general understanding of the fundamentals of the fabrication process, structure, properties and performance of the thin films of amorphous carbon and related films. Amorphous carbon including DLC is one of the precious materials related to diamond in film form. Especially, material science is still in the process of defining amorphous carbon and related films. Our understanding of amorphous carbon and related films is barely on its developmental stage due to increasing current opportunity for discussion among researchers who own various backgrounds. The opportunity for discussion has been made available by the steady efforts made by scientists belonging to several universities and research institution in Japan. Organization work started in 2004, when the researchers held a workshop entitled "Science of Amorphous Carbon and Related Films (SACRF)". In 2006, the SACRF workshop welcomed several company members in addition to the university and national institution researchers to promote discussion among researchers with various backgrounds. This group accomplishes research project ACTION 2006 supported by the New Energy and Industrial Technology Development Organization (NEDO). ACTION 2006 draws up a plan for the material identification on the amorphous carbon and related films. The SACRF workshop collected more than 58 samples from the research workers on the amorphous carbon and related films in Japan. The structure, properties and performance of the samples of 58 samples will be classified and presented in the session.
10:20 AM		D2-2-9 Modified DLC Coatings Prepared in a Large-Scale Reactor by Dual Microwave/Pulsed-DC Plasma-Activated Chemical Vapour Deposition C. Corbella, I. Bialuch, M. Kleinschmidt, K. Bewilogua (Fraunhofer IST, Germany) Diamond-Like Carbon (DLC) films find abundant applications as hard and protective coatings due to their excellent mechanical and tribological performances. The addition of new elements to the amorphous DLC matrix tunes the properties of this material, leading to an extension of its scope of applications. In order to scale up their production to a large plasma reactor, DLC films with silicon and oxygen additions have been grown in an industrial plant of 1 m³ by means of pulsed-DC Plasma-Activated Chemical Vapour Deposition (PACVD). The use of an additional microwave source has enhanced the glow discharge, partly by Electron Cyclotron Resonance (ECR), accelerating therefore the deposition process. Hence, acetylene, TMS and HMDSO constituted the respective gas precursors for the deposition of a-C:H, a-C:H:Si and a-C:H:Si:O films by dual microwave/pulsed-DC PACVD. This work presents the systematic studies of the deposition rate, hardness, adhesion, abrasive wear and water contact angle aimed to optimize the technological parameters of deposition: gas pressure, relative flow of the precursors, input power. The deposition rates around 1 µm/h, typical for modified DLC standard processes held in the large reactor, are increased by a factor 10 when the ionization source has been operated in ECR mode.
10:40 AM		D2-2-12 Mechanical Comparison of Deuterated and Hydrogenated Amorphous Diamond-Like-Carbon Coating Prepared by rf-PECVD and FCVA N. Mathis, C. Meunier, A. Roman (Université de Franche Comté, France); G. Berthout, G. Favaro (CSM Instruments SA, Switzerland); G. Guibert, S. Mikhailov (IMA, HE-Arc, Switzerland) In this study we compared the mechanical performances of diamond-like-carbon (DLC) films prepared both by plasma-enhanced chemical vapor deposition (PECVD) and by filtered single bend cathodic vacuum arc (FCVA). We introduced gas precursors like CH₄, CD4 and their mixture 1:1 in the plasma, to obtain hydrogenated and/or deuterated amorphous carbon thin film (a-C:H,a-C:D, ta-C:H, ta-C:D). In PECVD, wide self bias voltages variations are applied (-50V to -600V) to obtain a large range of chemical and mechanical properties. In FCVA, the trigger voltage and the sample holder bias voltage are varied in the same way (12kV to 20 kV). We studied the consequences of these electrical variations on the chemical and mechanical properties of the carbon films. In the both experiments we deposited the DLC coating single layer on silicon wafer (100) with a constant thickness of 200 nm, controlled by X-Ray Reflectivity. Chemical compositions are determined by ions and electrons spectroscopies (RBS, ERDA, XPS). Mechanical properties such hardness, apparent elastic modulus, critical load, friction coefficient and wear rate are analyzed. We found that the hydrogen replacement by deuterium gave place for PECVD, to an enhancement of hardness and a decrease of wear rates for low self bias voltage. Concerning FCVA results we found that including deuterium in ta-C structure allows a decrease of friction coefficients and wear rates.