Surface Temperatures Generated by Friction with Ceramic Materials

Abstract

For tribological applications of ceramics, surface temperatures and thermal effects produced in frictional processes are important not only in influencing possible mechanisms of friction, wear, and lubricant film failure but also in initiating protective film formation, e.g., as in tribopolymerization. As part of a continuing combined experimental and theoretical study of surface temperatures generated by friction, the fundamental Greens function approach has been applied to a number of ceramics including those used in tribological applications such as bearings and advanced low heat-rejection ceramic engines. The ceramics examined consisted of (a) alumina, Al2O3, (b) single crystal sapphire, Al2O3, (c) partially stabilized zirconia, ZrO2, (d) tungsten carbide, WC, (e) silicon carbide, SiC, and (f) silicon nitride, Si3N4. In addition, three forms each of silicon carbide and silicon nitride were included in this study, i.e., sintered, hot-pressed, and reaction-bonded. Assuming a single area of real contact, calculated ratios of average surface temperature rise to coefficient of friction plotted against area of contact, velocity, and load on a logarithmic scale are presented for all the above ceramics for A-on-A (self-mating) contact as well as an example of a ceramic in sliding contact against steel. The results show that as expected, very high surface temperatures can be generated by some ceramics, particularly those having very low thermal conductivity (e.g., zirconia), high hardness, or a combination of both. However, not all ceramic combinations produce high temperatures. It is suggested that the information developed may be useful in understanding the wear behavior of ceramics as well as in designing novel anti-wear approaches for ceramic lubrication. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999