Lubricating properties of diamond-like coating

Abstract

The friction of hydrogenated hard carbon coatings against themselves or against a metal depends on the tribocontact environment. A low friction state is associated with an inert environment whereas the physisorption of water vapour induces a transition to a high friction state. A theoretical calculation of the hydrogen bond given in this paper leads 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 in the coating. The hydrogen is weakly bonded under vacuum and strongly bonded in a moist environment. The purpose of this paper is to present the tribological behaviour of diamond-like carbon coatings obtained by a chemical vapour deposition process. We present a calculation model of hydrogen-carbon binding under different environments and we discuss the influence on the tribological behaviour.