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

The fretting wear of sulphur-deficient MoS x coatings with different crystallographic orientations has been investigated in ambient air of controlled relative humidity. The coefficient of friction and the wear rate of MoS x coatings sliding against corundum depend not only on fretting parameters like contact stress, fretting frequency, and relative humidity, but also strongly on the crystallographic orientation of the coatings. For randomly oriented MoS x coatings, the coefficient of friction and the wear rate increased significantly 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 corundum with increasing contact stress and decreasing fretting frequency. A correlation between dissipated energy and wear volume is proposed. This approach allows detection in a simple way of differences in fretting wear resistance between randomand basal-oriented MoS x coatings tested in ambient air of different relative humidity.