Papers

ICMCTF1999 Session E5/D4: Properties and Applications of Diamond, Diamondlike and c-BN Coatings

Tuesday, April 13, 1999 8:30 AM in Room California

Tuesday Morning

Start	Invited?	Item
8:30 AM		E5/D4-1 Tribological Properties of Nanocrystalline Diamond Films A. Erdemir, G.R. Fenske, A.R. Krauss, D.M. Gruen, T. McCauley, R.T. Csencsits (Argonne National Laboratory) In this paper, we will present the friction and wear properties of nanocrystalline diamond films grown in Ar-fullerene (C60) and Ar-CH4 microwave plasmas. Specifically, we will address the fundamental tribological issues posed by these films during sliding against SiC counterfaces in ambient air and inert gases. The films grown by the new method have very small grain sizes (10-30 nm) and are much smoother (20-40 nm, root mean square than films grown by the conventional H 2-CH4 microwave-assisted CVD process. Transmission electron microscopy reveals that the grain boundaries of these films are very sharp and free of nondiamond phases. As is known, the diamond films grown by most conventional methods consist of large grains and rough surface finish which can cause severe abrasion during sliding against other materials. Films grown by the new method (i.e., in Ar-C60 and Ar- CH4 plasmas) provide friction coefficients comparable to those of natural diamond and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can dominate the friction and wear performance. Employing a combination of transmission electron microscopy, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy, we describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of nanocrystalline diamond films during tests in dry N2. Finally, we mention a few potential applications for which nanocrystalline diamond films can improve performance and service lives.
9:10 AM		E5/D4-3 Preparation of Diamond Film by HFCVD of Camphor in Methyl Alchohol S. Chaudhuri, K. Chakrabarti, A.K. Pal (Indian Association for the Cultivation of Science, India) Use of methane as a precursor is of current interest in diamond research since it is known that methane with atomic hydrogen plays the key role in diamond deposition. Any other precursor containing methyl group may also be a suitable source of carbon for diamond deposition. In the present work, we have demonstrated that camphor (C₁₀H₁₆O, a natural source) + methyl alcohol with hydrogen may be a suitable precursor for diamond deposition at lower substrate temperature (873 K). During deposition hydrogen was bubbled through a solution of camphor in methyl alcohol before being introduced in the HFCVD chamber in which diamond films were deposited on Si, quartz and Mo substrates. The films were characterized by the XRD, FTIR, photoluminescence (PL) and Raman studies. The SEM studies of the films indicated average grain size of 0.7 µm on quartz and 3.5 µm on Si substrate when deposited without any pretreatment of the substrate surface with diamond paste. The variation of band gap (3 to 4 eV) with the deposition condition could be explained by the variation of sp³/sp² ratio (within 6 to 10). Although FTIR studies indicated the films to be sp³ rich, the PL spectra indicated that there may be considerable amount of non-diamond phases at the grain boundaries of the microcrystalline films. The average value of stress in the film, estimated from the Raman peak shift and optical absorption band tail measurement (to avoid the substrate effect), was nearly 13 GPa while hardness was > 40 GPa. Films were also deposited by HFCVD of methyl alcohol only (without using camphor) which showed much lower grain size and growth rate than those obtained with the addition of camphor in the alcohol. The films were boron doped by using a parallel path of hydrogen bubbling through a solution of trimethyl borate and good quality films were characterized by electro-optical measurements.
9:30 AM		E5/D4-4 Friction and Wear Performance of Diamond-like Carbon Films Grown in Different Source Gas Plasmas A. Erdemir (Argonne National Laboratory); I.B. NILUFER, O.L. ERYILMAZ (Istanbul Technical University, Turkey); M. Beschliesser (The University of Leoben, Austria); G.R. Fenske (Argonne National Laboratory) In this study, we investigated the effects of various source gases (i.e., methane, ethane, ethylene, acetylene, etc.) on friction and wear performance of diamond-like carbon (DLC) films. Films were deposited on AISI H13 steel substrates and tested in a pin-on-disk machine against the DLC-coated M50 balls in dry nitrogen. We found a close correlation between friction coefficient and source gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios had lower friction coefficients and lasted longer than films grown from source gases with lower hydrogen-to-carbon ratios. The lowest friction coefficient (0.015) was achieved with a film derived from methane (having an H/C ratio of 4) while the films derived from acetylene (H/C=1) had a coefficient of 0.15. Similar correlation was observed on wear rates of films on both ball and disk sides. Specifically, the films derived from gases with lower C/H values wore out quickly, while the films from methane and ethane lasted a very long time. Raman spectroscopy and electron microscopy were used to elucidate the structural chemistry of each film and of wear debris particles, and these findings were correlated.
9:50 AM		E5/D4-5 The Role of CN Chemical Bonding on the Tribological Behavior of CN_x Coatings C. Donnet, J. Fontaine, J.M. Martin, T. Le Mogne (Ecole Centrale de Lyon, France); C. Quirós, R. Núñez, P. Prieto, E. Elizalde, J.M. Sanz (Universidad Autonoma de Madrid, Spain); T.C. Rojas, A. Fernández (Instituto de Ciencia de Materiales de Sevilla, Spain) The tribological performances of CN_x coatings strongly depends on both the environmental conditions and the nature of the coating, in relation to the deposition process. The paper will present and discuss friction results linking the nature, structure and composition of CN_x coatings, prepared by dual ion beam sputtering in various conditions. The films have been characterized by infrared spectroscopy, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. Friction tests have been carried out in ambient conditions in the reciprocating mode. The highest tribological performances have been achieved with CN_x films with a N/C content between 0.3 and 0.5. A low concentration of CN triple bond has been stated. The films containing a majority of CN double bond exhibit a poor wear resistance. The discussion proposes a correlation between the deposition conditions, the nature of the films and the tribological behavior, showing that a combination of selected bonds is necessary to achieve the desired film properties.
10:30 AM		E5/D4-7 Tribology and Surface Chemistry of Low Stress Hydrogen-Free Amorphous Diamond-Like Carbon^* M.T. Dugger, T.A. Friedmann, D.M. Follstaedt, J.A. Knapp, E.H. Sorroche (Sandia National Laboratories); J.W. Ager, III, I.G. Brown, O.R. Monteiro (Lawrence Berkeley National Laboratory) Tribological measurements have been made on ultrahard amorphous-tetrahedrally bonded carbon (a-tC) films prepared by pulsed laser deposition and by a pulsed vacuum-arc plasma process. Processes have been developed to make films over 1 µm thick by pulsed laser deposition having residual compressive stress less than 0.2 GPa, by repeated steps of deposition and annealing at 600°C. These relatively low stress films retain the high degree of tetrahedral bonding found in the as-deposited films. During contact with 440C steel in air at 54 MPa contact stress, a friction coefficient of 0.26±0.01 was observed and increased by 50% over the duration of the experiments. At a contact stress of 131 MPa in air, the starting friction coefficient was reduced to 0.21±0.02, and the friction coefficient decreased 50% over the duration of the tests. No delamination or wear-through of the films occurred for over 1200 cycles of contact. We will discuss the behavior of friction coefficient with sliding in environments from vacuum to pure nitrogen to nitrogen containing varying amounts of oxygen and water vapor. Friction behavior will be correlated with changes in surface composition, including the degree of σ and π bonding, as an indicator of transformations in the carbon surface upon sliding for the two types of diamond films. ^*Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000
11:10 AM		E5/D4-9 The Friction Characteristics of Hydrogen-free and Hydrogenated Hard Carbon Films in Dry and Humid Atmospheres J. Koskinen, H. Ronkainen, S. Varjus, K. Holmberg (VTT Manufacturing Technology, Finland) The tribological performance of hydrogen-free and hydrogenated diamond-like carbon (DLC) coatings differ from each other, particularly when considering the friction characteristics. The hydrogen-free hard carbon (ta-C) films, deposited by a pulsed vacuum arc discharge method, and hydrogenated amorphous carbon (a-C:H) films, deposited by r.f. plasma method, were tested in ambient atmosphere (50 % RH) and in dry nitrogen and dry synthetic air. The counter part material was steel (AISI 52100), the normal load applied 5 N and the sliding velocity 0.008 m/s. The wear surfaces were analysed by ESCA after the tests. The ta-C films showed low friction in ambient air, but in dry nitrogen the friction coefficient was high (0.8). The a-C:H films, on the contrary, have a lower friction coefficient in dry nitrogen and dry synthetic air than in ambient air. The friction characteristics and surface analysis data will be discussed in detail. Also the ta-C films with improved friction performance in dry conditions, will be reviewed.
11:30 AM		E5/D4-10 Effects of Direct Current and Pulse-Plating on the Co-Deposition of Nickel and Nanometer-Diamond Powder Coatings W.-H. Lee, S.-C. Tang, K.C. Chung (National Taipei University of Technology, Republic of China) Nickel and nanometer-diamond powder has been successfully co-deposited on the Cu alloy by the direct current and pulse plating methods. The investigated variables of this research work include the concentration of diamond powder in the plating solution, current density (D.C.), current frequency (pulse plating), plating temperature, plating time, and stirring speed during plating processes. The optical microscope and scanning electron microscope (SEM) were used to characterize the properties of the coating layer. The microhardness and the wear resistance of the coating layer are also tested. The microhardness of the co-deposited layer will be increased with the increasing of concentration of diamond powder in the plating solution. However, the surface roughness will be increased as well. The value of the specimen treated with 40 g/l diamond powder concentration is HV 540, which is almost three times of that without powder addition (pure Ni plating). Although the nanometer diamond powder has a longer floating time than that of larger ones, the stirring step seems necessary for the co-deposition processes. The stirring speed below 300 rpm and plating temperature ranging from 30°C to 50°C are found suitable for Ni-diamond composite plating. The friction coefficient (μ) of Ni-20g/l diamond co-deposition specimen is about 0.16, which is much lower than that of pure Ni-plated layer (μ = 0.44).
11:50 AM		E5/D4-11 Fine Polishing of Diamond Film Via a Thinning Process Using Fe, Ni, Cr Alloys and a Dry Grinding Process Using a Synthetic Diamond Powder S.-H. Kim, J.-C. Park (Silla University, South Korea); T.-G. Kim (Miryang National University, South Korea) Shiny surface morphology of diamond film as a mirror surface could be obtained using two-step polishing process, namely, thinning and then dry grinding processes. For the thinning process, we placed Fe, Ni, Cr alloys onto the surface of the free-standing diamond film and heated it using either hydrogen plasma or the thermal methods. The morphologies and the characteristics of the films were investigated as functions of the methods and the alloy compositions used in the thinning process. For the dry grinding process, we used metal (a mixture of Cu and Sn) resin synthetic diamond plate and synthetic diamond powders. we designed a leveling device mounted onto the sample holder for maintaining the balance of the polishing area. The surface morphologies of the polished area and the residual impurities after dry-grinding process were investigated. Finally, we could suggest the best materials and methods to obtain the polished area of diamond film applicable to electronic device.