ON TEMPERATURE-DEPENDENT TRIBOLOGICAL REGIMES AND OXIDATION OF CARBON-CARBON COMPOSITES UP TO 1800-DEGREES-C

This paper describes an experimental study on the temperature-dependen t tribological behavior and oxidation of a carbon-carbon (C/C) composi te material sliding against itself in ambient air up to 1800 degrees C . Tribological experiments were conducted with a ring-on-ring type of apparatus using a wide range of load and speed conditions. As the spec imen temperature gradually increased with frictional heating, the fric tion of C/C composites experienced two abrupt increases at 150-200 deg rees C and 650-700 degrees C. The two transition temperatures divided the friction and wear of C/C composites in ambient air into three temp erature-dependent regimes: the normal wear, the water-desorption dusti ng wear, and the oxygen-desorption dusting wear regimes. The friction and wear also depended on the load and speed conditions. In addition t o the wear loss at the rubbing surface, the oxidation loss at the exte rior of the specimen also contributed to the weight loss of the specim en, especially at elevated temperatures. The linear wear of C/C specim ens amounted to less than 2% of the total weight loss when the maximum specimen temperature exceeded the failure temperature of the oxidatio n-inhibitor. The effect of specimen geometry on the wear and oxidation at the rubbing surface is also discussed.