LUBRICATING PROPERTIES OF DIAMOND-LIKE COATING

The friction of hydrogenated hard carbon coatings against themselves o r against a metal depends on the tribocontact environment. A low frict ion state is associated with an inert environment whereas the physisor ption of water vapour induces a transition to a high friction state. A theoretical calculation of the hydrogen bond given in this paper lead s to the conclusion that the interaction forces vary with the relative dielectric permittivity of the environment. Small quantities of water vapour inhibit the lubricating properties of the hydrogen contained i n the coating. The hydrogen is weakly bonded under vacuum and strongly bonded in a moist environment. The purpose of this paper is to presen t the tribological behaviour of diamond-like carbon coatings obtained by a chemical vapour deposition process. We present a calculation mode l of hydrogen-carbon binding under different environments and we discu ss the influence on the tribological behaviour.