Frictional behaviors of diamond-like carbon films under water lubrication: A molecular dynamics study

This study investigates the influence of water lubrication on the friction of DLC films. It is found that water molecules at contact interfaces prevent the formation of interfacial C-C covalent bonds and show hydrodynamic lubrication effects, and thus effectively postpone the friction increase in initial friction stages. Moreover, for the small/medium amount of water molecules, they would diffuse into the DLC films during further sliding, hence highly decrease the interfacial density of carbon networks but inhibit their graphitization. This suggests that the degraded mechanical strengths of DLC films induced by the water diffusions at the interfaces contribute much to the friction reduction of these films, which improves the current understanding that such reduction is mainly caused by tribochemical reactions.