The influence of the environment on the friction and wear of graphitic carbons

Review of the tribology of diamond-like carbon

“…Hydrogen passivates the dangling bonds in the hydrogenated DLC films and permits only weak interactions between DLC and the sliding partner. When hydrogen is lost from hydrogenated DLC by annealing, the dangling bonds created cause strong interactions between the contacting surfaces, resulting in increased friction in UHV or dry nitrogen, similar to the cases reported for diamond or graphite [16,22]. Humidity reduces the friction coefficient to an intermediate value, as it would do for graphite, but also for diamond, although the values are closer to that of graphite.…”

“…It appears from the results presented above that, in hydrogenated DLC films, hydrogen has a similar effect to that in diamond [16] or in graphite [22]. Hydrogen passivates the dangling bonds in the hydrogenated DLC films and permits only weak interactions between DLC and the sliding partner.…”

“…Hydrogen has been found to have a similar lubricating effect on graphite. Zaidi et al [22] investigated the sliding wear of graphite against graphite in an atomic hydrogen atmosphere produced by passing hydrogen over a tungsten ribbon at 2000 K. The authors found that atomic hydrogen is an effective lubricant for graphite and that there is a close analogy between the lubrication of the graphite by water vapor and by atomic hydrogen. It appears that hydrogen passivates dangling bonds at the edges of the graphite crystallites, leaving only the possibility of weak interactions with the r bonds, thus resulting in reduced friction.…”

Study of a-C:H thin films grown by PIII in different times for Mechanical and Tribological applications

“…It is a consistent explanation with Raman analysis, which the layer has a disordered graphite structure, revealing evidence of amorphization of a-C:H films in the wear track. If the hydrogen is removed from hydrogenated DLC, the dangling bonds formed cause strong interactions between the surfaces in contact, resulting in a slope of friction coefficient as function of loss of hydrogen dry hydrogen (35) , similar to that reported for both graphite and diamond (36,37) .…”

Friction and wear performance of diamond-like carbon films grown in various source gas plasmas

“…In fact, the low-friction mechanism of diamond is largely attributed to the highly passive nature of its sliding surface [33][34][35]. When hydrogen and other species are desorbed or removed from the sliding surfaces of diamond and/or graphite (e.g., by ion-beam sputtering and/or high-temperature annealing in vacuum), the friction coefficient increases significantly, presumably because the reactivated dangling bonds cause strong adhesive interactions between the diamond and the countetiace ball or pin materials [33][34][35][36][37][38][39][40].…”