Evidence for tribochemical wear on amorphous carbon thin films

The friction and wear properties between a smooth oxide-based ceramic sliding and an amorphous carbon surface are greatly influenced by the surface chemistry of the carbon layer. Like most carbon compounds, surface oxides can form if the surface is exposed to oxygen. These surface species can desorb as carbon monoxide and/or carbon dioxide under the rubbing action of the slider. Such a gradual tribochemical wear mechanism induces a greater area of true contact, and the friction coefficient increases dramatically from 0.2 to 1.2 or higher when repeated sliding contacts are made. In contrast, similar tribological experiments carried out in an inert environment show no friction increase. >