TRIBOLOGICAL BEHAVIOR OF DIAMOND-LIKE COATINGS - EFFECT OF ACTIVE GASES IN ATOMIC AND MOLECULAR-STATES

Diamond-like coatings have very good mechanical properties and present a real area of interest in studying their tribological behaviour. How ever, their friction coefficient is strongly affected by gaseous envir onments. Under a vacuum, when the coating contains hydrogen, the frict ion coefficient is lower than that in ambient air. To explain the lubr icating mechanism of the gases on the surface, we have experimentally studied the effect of active gaseous species, such as atomic and molec ular oxygen, hydrogen, nitrogen and water vapour, on the frictional be haviour in relation to the presence of hydrogen in the substrate. A tr ibochemical interpretation is proposed in connection with the temperat ure of the contact asperities.