Friction and Wear Behaviors of MoS_x-doped DLC films Ⅱ: Effect of Sliding Speed

(MoS_x)-doped diamond-like carbon (a-C:H:Mo:S) films were prepared using a hybrid radio frequency plasma-enhanced chemical vapor deposition and unbalanced magnetron sputtering deposition technique. Their composition, surface topography, nanohardness and thermal stability were investigated. Friction and wear tests at different sliding speed were conducted on a QG-700 tribometer. The friction and wear mechanism was briefly discussed based on the characterizations of frictional surfaces by optical microscope, scanning electron microscopy and energy dispersive spectrometer. The results reveal that the friction coefficient first increases and then decreases with increasing sliding speed, while the wear rate just varies oppositely. The increase in friction coefficient is due to the aggravated surface oxidization in high-humidity environment, but the decrease is most likely due to the friction-induced graphitization.