Fretting wear rate of sulphur deficient MoSx coatings based on dissipated energy

The fretting wear of sulphur-deficient MOSx coatings with different crystal lographic orientations has been investigated in ambient air of controlled r elative humidity. The coefficient of friction and the wear rate of MoSx coa tings sliding against corundum depend not only on fretting parameters like contact stress, fretting frequency, and relative humidity, but also strongl y on the crystallographic orientation of the coatings. For randomly oriente d MoSx coatings, the coefficient of friction and the wear rate increased si gnificantly with increasing relative humidity. In contrast, basal-oriented MOSx coatings were less sensitive to relative humidity. The coefficient of friction of both types of MoSx coatings decreased on sliding against corund um with increasing contact stress and decreasing fretting frequency. A corr elation between dissipated energy and wear volume is proposed. This approac h allows detection in a simple way of differences in fretting wear resistan ce between random- and basal-oriented MoSx coatings tested in ambient air o f different relative humidity.