ICMCTF2000 Session E5/D4-2: Properties and Applications of Diamond, Diamondlike and Related Coatings
Thursday, April 13, 2000 1:30 PM in California
E5/D4-2-1 Issues Related to Tribological Characterization of DLC films
P. Maurin-Perrier, C. Heau (HEF, France)
Diamond-like carbon coatings (DLC) are widely recognized for providing low friction coefficients and wear rates under various environmental and mechanical sollicitations.Depending on the type of deposition method, different behaviors could be observed for given testing environment.@paragraph@A different approach is proposed in this paper where a review is made on how for a given deposition method the tribological behavior strongly depends on the type of test. Tribological assessment is performed with sliding speed and contact pressure ranging respectively from 0.01 to 0.5 m/s and 0.1 to 1GPa, under various environment (air, nitrogen, vacuum).It evidences that among the films properties (coating thickness, surface roughness,...) the ones that have an influence on the tests results vary from one set of sollicitations to the other. An interpretation is then proposed to explain why certain properties have an effect on the coating tribological behavior.
E5/D4-2-3 Tribochemical Effects on CN@subx@ Films
J.C. Sánchez-López, C. Donnet, M. Belin, J. Fontaine (Ecole Centrale de Lyon, France); C. Fernández-Ramos, M.J. Sayagués, A. Fernández (Instituto de Ciencia de Materiales de Sevilla, Spain)
CNx thin coatings have been deposited by DC-magnetron sputtering using a graphite target in nitrogen atmosphere under different experimental conditions. X-ray photoelectron spectroscopy, electron-energy loss spectroscopy, nuclear magnetic resonance and Fourier-transformed infrared spectroscopy were used to elucidate the structural chemistry of each film. The tribological behavior has been investigated by reciprocating pin-on-flat tribometer in a wide range of environmental conditions: ambient air, nitrogen, argon and vacuum. Tribochemical effects in relation to the nature of the surrounding atmosphere during friction tests are presented. Strong relationships between the N/C ratio, the nature of C-N bonds and the friction behavior are highlighted and discussed.
E5/D4-2-4 Non Wetting Properties of Modified DLC and Chromium Nitride Films
A. Hieke, K. Bewilogua, I. Bialuch, N. Bonhoff (Fraunhofer Institute for Surface Engineering and Thin Films, Germany)
For many applications in the areas of food industry, heat exchanger technology, polymer fabrication and pharmaceutical industry wear-resistant and non-sticking PTFE-like coatings have a very high potential. Two promising layer systems are DLC films modified with silicon and oxygen and chromium nitride coatings. Surface energies were derived from contact angle measurements. Characteristic values of modified amorphous carbon based coatings and carbon free chromium nitride films will be compared. The modified DLC films were deposited in a radio frequency (13.56 MHz) glow discharge by using hydrogenated gases and silicon containing precursors. Our work showed that it is possible to generate a silicon and oxygen doped DLC film with a similar non-sticking behaviour like PTFE. On the other hand chromium nitride coatings were prepared by reactive DC magnetron sputtering in a argon/nitrogen atmosphere. Correlation’s between the ion current density during film growth, the nitrogen content in the coatings and the surface energy were revealed. Furthermore we present results about the time stability of the surface energy values, the hardness and the abrasive wear resistance of the deposited films.
E5/D4-2-5 Comparative Study of the Tribological Moisture Sensitivity of Different Diamondlike Carbon Films
R. Gilmore, R. Hauert (Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland)
A well-known drawback of DLC tribological coatings is their loss of lubricating properties at high relative humidity, limiting their use in certain tribological applications for which ambient humidity levels may vary significantly. In this paper, we directly compare some of the methods currently proposed for reducing this moisture sensitivity. Different types of DLC coatings have been prepared using a PACVD technique, both in a pure form and with the addition of small amounts of other elements such as Ti or Si. Coatings were then tribologically tested to highlight their sensitivity to ambient humidities in the range 5 to 90% RH, against steel and alumina counterfaces, and XPS analysis was used to examine coating and transfer-layer chemistry. Commercially-available DLCs were also similarly tested for comparison. It was shown that Ti- and Si-containing coatings displayed reduced friction coefficients for high ambient humidities and that frictional behaviour is strongly dependent on counterface material.
E5/D4-2-7 Invited - Missing - Ohmae
Unknown Ohmae (Consultant)
E5/D4-2-9 Synthesis, Characterization and Properties of: Nanocomposite DLC Films
V. Singh (Louisiana State University); E.I. Meletis (Louisiana State University.)
Diamondlike carbon (DLC) films, known for exhibiting attractive combination of properties, have been extensively studied in the past. However, a significant drawback with these films is their relatively low thermal stability above 400@super o@C. The present work focuses on the synthesis and study of nanocomposite DLC films with the addition of carbide formers, Si, Ti and Cr. They offer the potential to stabilize the tetrahedral (sp@super 3@) structure and enhance the thermal stability of these films while maintaining their mechanical properties. Nanocomposite DLC films with Si, Ti and Cr additions upto 20 at.% were developed using a combination of intensified plasma assisted processing and sputter deposition techniques. These nanocomposite films were characterized by SEM-EDAX, and analytical TEM. Annealing experiments were conducted at various temperatures to assess the thermal stability as a function of additive type and concentration. Pin-on-disc experiments were conducted to study the wear behavior of the films.
E5/D4-2-10 Use of Diamond like Carbon and Diamond Coatings in Forming and Cutting of Aluminium
K.H. Taube, J. Gäbler (Fraunhofer Institut für Schicht- und Oberflächentechnik, Germany)
In a companion paper ("Tribology of carbon-based coatings with Aluminium ") the tribology of aluminium with DLC and crystalline diamond coatings was investigated. Rather high friction values and aluminium transfer on DLC was found in dry testing. This could be minimized by using stronger lubrication or just pure water. Aluminium transfer and high friction values were also found with crystalline textured diamond coatings (DiaTex®by Fraunhofer IST), but not on the surfaces of the crystallites, just in the gaps between them.@paragraph@ In this talk these results are correlated with application oriented deep drawing and cutting tests and results from production. Also here it is found that forming and punching of aluminium alloys with DLC coated tools is possible with very limited amounts of lubricating agents or/and pure water, but not dry. The beneficial effects of coated tools for lower drawing and cutting forces were investigated. Cutting of aluminium alloys without any cooling and lubrication seems feasible with a smooth DiaTex®coating.
E5/D4-2-11 Trial Fabrication and Cutting Performance of c-BN-Coated Taps
M. Jin, S. Watanabe, S. Miyake, M. Murakawa (Nippon Institute of Technology, Japan)
In this study, the possibility of using a c-BN-coated tap for cutting a beta-type titanium alloy which has been known as one of the most difficult to cut materials was investigated. The beta-type titanium alloy is known to strongly adhere to the tools during the operation. The authors considered that the c-BN coating film, which is known to have good tribological characteristics, could be effective in preventing this adhesion for cutting operations of the beta-type titanium alloy. We fabricated c-BN-coated taps by means of a magnetically enhanced ion plating method and carried out tapping experiments to evaluate the performance of the tap. As seen from the results, the c-BN-coated taps proved to be effective in the cutting of beta-titanium alloys with improvement in the accuracy, tapping torque and tool life over those in the case of commercially available conventional-coated taps.
E5/D4-2-12 Effect of Composition Modulation on the Tribological Performance of Metal Containing Diamond Like Carbon Coatings
C. Strondl, G.J. van der Kolk, A.P.A. Hurkmans (Hauzer Techno Coating Europe BV, The Netherlands); T. Trinh (Hauzer Coating Centrum BV, The Netherlands); W.S. Fleischer (Hauzer Techno Coating Europe BV, The Netherlands)
Metal containing diamond like carbon is at present the most widely applied tribological coating system. Present coatings are mainly based on a bi-layer approach, whereby an interface layer is deposited like Cr or Ti, followed by a Me-C:H layer, whereby normally W is taken as metal. Composition modulation of the coating is normally present but not well controlled as it depends on target geometries, plasma conditions and substrate rotation speed. In the present paper we have controlled the composition modulation for a number of transition metals. The modulation period has been varied from 1 to 300 nm. The effects on tribological and mechanical properties of the coating have been studied.