The effect of counterface on the tribological performance of a high temperature solid lubricant composite from 25 to 650 degrees C

The effect of counterface selection on the tribological performance of a Ag/BaF2-CaF2 containing composite coating are studied. Ceramic (Al2O3) and metal (Inconel X-750) pins are slid against PS300 (a metal bonded chrome oxide coating with Ag and BaF2/CaF2 lubricant additives) in a pin-on-disk tribometer at 25, 500 and 650 degrees C. Compared to the ceramic counterface, the metal counterface generally exhibited lower friction and wear at 25 degrees C but higher friction and wear at 650 degrees C. Friction coefficients, for example, for the Al2O3/PS300 combination at 25 degrees C were 0.64 compared to 0.23 for the Inconel/PS300 sliding couple. At 650 degrees C the ranking was reversed: the Al2O3/PS300 combination gave a friction coefficient of 0.19 while the friction for the metal counterface increased slightly to about 0.3. Based upon these tribological results and other information found in the literature, it appears that the performance of each counterface/PS300 combination is affected by the ability of the solid lubricant additives to form an adequate transfer film. The effects of surface wettability and tribological compatability are discussed in relation to the observed tribological results.