Effect of structure of carbon films on their tribological properties

The friction and wear performance of the carbon films were found to depend on both the structure and the ambient conditions. Hydrogen free films have friction coefficients < 0.1 for 80% sp3 bonded films and > 0.1 for 100% sp2 bonded films. The wear resistance of the hydrogen free films (much larger for sp3 bonded films) significantly decreases under dry conditions. In contrast, hydrogenated films show reduction in friction with decreasing humidity (from 0.2 under 50% RH to < 0.1 under 5% RH). The wear resistance of hydrogenated films is larger for dry and smaller for humid conditions.