Tribological Characteristics of Novel Superhard Carbon Compacts for Self-Lubricating Applications

Tribological performance of a recently developed hard carbon material (Diamonite(TM)) was evaluated. The samples of new carbon ceramic were sintered from fullerene C-60 under high pressure. Pin-on-disc experiments were performed without lubrication between 440C stainless steel balls and the superhard carbon disc samples at 200-400 rpm, with loads of 0.25 N, 0.5 N and 1.00 N. The testing environments include humid air (40 % RH) and dry nitrogen atmospheres. Microstructural analysis of the as-sintered carbon ceramic, wear scar analysis on the carbon discs, and material transfer to the steel balls were examined using a scanning electron microscope. The coefficients of friction obtained were 0.15-0.17 in lab air. In dry testing condition, the material showed surprisingly low coefficients of friction (0.05-0.12). Raman analysis was used to determine the chemical bonding of the as-polished materials and the changes in sp3 to sp2 ratio of carbon bonding before and after wear tests. Comparisons of the tribological performance of new carbon ceramic with diamond ceramic will be presented. The results demonstrated the feasibility of using this fullerene-derived carbon material with a low coefficient of friction for self-lubricating antifriction applications.