ICMCTF2002 Session E5/D4-1: Properties and Applications of Diamond, Diamondlike and Related Coatings

Thursday, April 25, 2002 8:30 AM in Room California

Thursday Morning

Start	Invited?	Item
8:30 AM	Invited	E5/D4-1-1 Nanotribology of Carbonaceous Film and its Potential Application to High-density Memory S. Miyake, J.D. KIM, S. Watanabe (Nippon Institute of Technology, Japan) To improve the triborlogical properties, carbonaceous nanoperiod multilayered films were deposited by controlling the time the substrate was positioned opposite each of the graphite and boron nitride semicircular targets. The wear depth of the 4-nm-period multilayer film is the lowest of all the sliding cycles; therefore, the wear resistance is clearly improved for a 4-nm-period layered film. To clarify the reason why the wear resistance of these multilayer films increases, the wear properties of the load conditions under which the wear increases atomically were evaluated by varying the number of sliding cycles. These results indicate that the wear resistance increased because of the prevention of fracture growth at the interface between B-N and C-N layers in the case of multilayer films. To realize high-density memory, the possibility of using tribo-memory, which is consistent with nanometer scale mechanical processing of multilayer film, was suggested, and the processing properties of multilayer film were studied using the diamond coated tip of the AFM.
9:10 AM		E5/D4-1-3 Deposition and Characterization of Ultra Thin Boron Carbide Films for Magnetic Media Overcoats M.L. Wu, J.D. Kiely, Y.T. Hsia, J.K. Howard (Seagate Technology) Boron carbide (B₄C) is used in a wide range of applications on coatings and cutting tools development. However, there are very limited studies of this material at ultra-thin regime (less than 10nm thick). In this paper, we focus on the properties of B₄C films with thicknesses less than 10 nm. Magnetron sputtering was used to produce these thin films on magnetic recording media. We have studied the nanotribological and mechanical properties of these thin B₄C films as a function of deposition parameters. We have evaluated the mechanical properties using atomic force microscopy (AFM ) nanoscratch techniques and find that these films have nanoscratch resistances superior to that of DLC films. We have surveyed variations in mechanical properties as a function of deposition parameters and correlate nanoscratch resistance with other film properties such as composition and stress. The AFM topography results showed that the surface root-mean-square roughness as low as 0.13 nm can be attained by applying appropriate substrate bias to enhance the ion bombardment during film growth. Finally, we comment on the use of these films as protective overcoats for hard-disk recording media.
9:30 AM		E5/D4-1-4 Comparison of Properties of Amorphous Carbon Nitride Films and Diamond-like Carbon Films Prepared by Shielded Arc Ion Plating O. Takai, K.H. Lee, T. Kawaguchi, H. Sugimura (Nagoya University, Japan) Amorphous carbon nitride (a-C:N) thin films show excellent tribological 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 comparison of the structural and mechanical properties of a-C:N films and DLC films prepared by shielded arc ion plating (SAIP). Structural properties were investigated by using UV and visible Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The a-C:N films prepared with negative bias showed excellent wear resistance. Particularly the a-C:N film prepared at around -300 V showed high wear resistant because its wear depth was almost zero in spite that the much harder DLC films were slightly worn under the same wear test condition. We investigated the origin of this high wear resistance in connection with the Raman and XPS measurements of the a-C:N and DLC films.
9:50 AM		E5/D4-1-5 Gas Permeation of Diamond-like Carbon Films on Polyethylene Terephthalate H Kodama, A. Kimura, T. Suzuki (Keio University, Japan) Diamond-like Carbon (DLC) coatings highly barriers oxygen gas and are expected applying to polymer substrates for food packaging. DLC films were deposited on polyethylene terephthalate (PET) substrates using rf-plasma CVD method and considered on relationship between their gas barrier property, optical transmission and chemical bonding. Optical transmission of the films was measured by Ultraviolet-Visible Spectrometer (UV/VIS) and the oxygen gas permeation was measured using OX TRAN (MOCON). Further, these films were analyzed by X-ray photoelectron spectroscope (XPS) and transmission electron microscope (TEM). The oxygen transmission rate of DLC coated PET films was 4.5-5.9 cm³/m²/24h/atm, which was 4-5% against that of uncoated PET films. The optical transmission decreased approximately 5 % as film thickness increased from 25 to 40 nm. Further, it decreased approximately 7 % when rf input power increased from 200 to 400 W in spite of same film thickness. XPS spectra from C1s region of the DLC films shifted to high binding energy with increasing the rf input power.
10:10 AM		E5/D4-1-6 Effect of Load on the Friction and Wear of DLC and TiN Coatings at Constant Hertzian Contact Pressure S.E. Franklin (Philips Centre for Industrial Technology, Netherlands) Precision sliding bearing systems in professional and consumer equipment applications should be capable of providing a low and stable friction behaviour and low wear rate for a long lifetime. They should also be inexpensive to manufacture and assemble and ideally require no maintenance during the lifetime of the equipment. Advancements in the commercial availability and costs of DLC (Diamond-Like-Carbon) coatings with a reliable quality mean that these coatings are increasingly becoming viable options for such applications. The thickness of DLC coatings can be controlled with great precision and many DLC coating types are capable of providing low wear and low friction in the unlubricated condition in bearing systems where only one of the surfaces is coated. In order to compare the performances of commercially available coatings, a number of friction and wear tests have been carried out under dry sliding conditions. A reciprocating steel ball-on-plate test configuration was used and tests were carried out with two DLC coatings and a PVD-TiN coating deposited onto hardened tool steel. Uncoated hardened tool steel was also tested as a reference. The nominal Hertzian contact pressure and sliding speed were kept constant for all tests whilst the diameter of the steel ball and the load were varied. In this way, the depth of the maximum Von Mises stress beneath the surface was varied whilst other parameters were kept constant. The friction and wear performances of the bearing systems are discussed in terms of the friction coefficient, coating lifetime and wear of the steel ball.
10:30 AM	Invited	E5/D4-1-7 Hard Coatings for Protective, Mechanical Barrier Applications K. Miyoshi, J.K. Sutter (NASA Glenn Research Center); J.S. Zabinski (Air Force Research Laboratory); M. Murakawa (Nippon Institute of Technology, Japan) Interest in applying hard coating technologies for protective, mechanical barriers continues to grow. Recent work on hard coatings, including thermally sprayed WC-Co, diamondlike carbon (DLC)-base, functionally graded, nanocomposites, and plasma-assisted chemical-vapor-deposited (PACVD) DLC are reviewed. These films and coatings can improve many of the surface properties, including erosion-, oxidation-, corrosion-, abrasion-, and wear-resistance, and chemical stability and low friction, of engineering substrate materials. The WC-Co coatings for high temperature polymer matrix composites used in gas turbine engine applications were prepared using a system comprised of a soft bond coat and a hard topcoat, and evaluated for their ability to withstand harsh solid particle erosion. The nanocomposite coatings consisting of amorphous carbon/titanium (a-DLC/Ti) top layers and functionally graded titanium-titanium carbide-diamondlike carbon underlayers were produced on 440C stainless steel disks by the hybrid technique of magnetron sputtering and pulsed-laser deposition. Also, an amorphous hydrogenated carbon (H-DLC) was produced on the a-DLC/Ti-based, functionally graded nanocomposite coating by using an ion beam (composed of a 3:17 mixture of argon and methane). The PACVD DLC films were prepared by using radiofrequency plasma and consisted of two layers, a DLC top layer on silicon-DLC underlayer. The surface properties, such as fretting wear-resistance, sliding wear-resistance, and self-lubricating properties, of the DLC coatings were evaluated.
11:10 AM		E5/D4-1-9 Tribological Properties of Carbide-derived Carbon (CDC) Films on SiC Substrates A. Erdemir (Argonne National Laboratory); Y. Gogotsi (Drexel University); M.J. McNallan (University of Illinois at Chicago); A. Kovalchenko (Argonne National Laboratory); A. Lee (University of Illinois at Chicago) In this study, we investigated the tribological behavior of carbide-derived carbon (CDC) films produced on SiC substrates by a chlorination process at 900 to 1000 ° C [1]. Tribological tests were performed in dry N₂ and high vacuum (10^-8 torr) using two pin-on-disk machines at room temperature. The test pairs consisted of a sintered Si₃N₄ ball (9.55 mm in diameter) and the SiC flats with and without the CDC coatings on their sliding surfaces. The sliding velocity was 0.16 m/s and the normal force was 5 N. Friction coefficients of test pairs in dry nitrogen were about 0.1 (similar to that in air [2]), but as high as 0.3 in high vacuum. When SiC samples with CDC coatings were first exposed to high vacuum, and then tested in dry nitrogen, the friction coefficients became very low, i.e., 0.04 at steady states. Sliding contact tests as a function of humidity revealed the existence of a close correlation between the friction coefficient of the CDC films and relative humidity. In general, the friction coefficients decrease with decreasing humidity. Such behavior is in contrast to that of the crystalline graphite or glassy carbon which exhibit a low friction at high humidity, but a higher friction and fracture at low humidity or in vacuum. Using Raman spectroscopy and electron microscopy, we explore microstructure and chemistry of these films and correlate these findings with friction and wear mechanisms in humid, dry, and vacuum environments. 1. Y. Gogotsi, S. Welz, D.A. Ersoy, M.J. McNallan, Conversion of Silicon Carbide to Crystalline Diamond-Structured Carbon at Ambient Pressure, Nature, v. 411, pp. 283-287 (2001) 2. D. A. Ersoy, M. J. McNallan, Y. Gogotsi, A. Erdemir, Tribological Properties of Carbon Coatings Produced by High Temperature Chlorination of Silicon Carbide, STLE Tribology Transactions, v. 43, pp. 809-815 (2000).
11:30 AM		E5/D4-1-10 Safe Machining of Magnesium with CVD-DP and Smooth CVD-DP Coated Tools H.K. Tönshoff, C. Podolsky, J. Winkler (University of Hannover, Germany) In the last years, an upcoming interest of the automotive industry has been noticed in the use of light metals as construction materials. Magnesium as the light metal with the lowest density offers a great potential for weight reduction. Still, for a safe and economic machining of magnesium parts, there are some problems to solve. Especially in dry machining and at high cutting speeds, adhesion between tool and workpiece material leads to build-up edges. Experiments show, that CVD-DP coated tools have a superior cutting performance but still lead to unsatisfactory surface topographies. Good results can be achieved when using new smooth CVD-DP coated tools. .
11:50 AM	Invited	E5/D4-1-11 Tribological Coatings for Rolling Element Bearings E.P. Cooke, G.L. Doll (The Timken Company) Rolling element bearings are among the most common machine elements. A rolling element refers to the ball or roller components that are used to separate the inner and outer rings. As in other machine elements, tribological coatings can increase the fatigue life, load rating, and provide wear resistance to rolling element bearings. For example, roller bearing life tests show that certain coatings can increase the fatigue life of premium product by more than 30%. Other tests show that the increase in wear resistance provided by other coatings to roller bearings is even more dramatic. The mechanisms by which tribological coatings increase fatigue life and wear resistance are complex, and typically application specific. Although complex, a working understanding of the inter-relationships between the mechanisms, the tribological conditions, and the coating properties has resulted in the incorporation of tribological coatings into rolling element bearing design.