Effect of crystallographic orientation on fretting wear behaviour of MoSx coatings in dry and humid air

Abstract

The tribological behaviour of MoS2 coatings in air of high humidity is critical for their application in air. An improved friction and wear resistance of sulfur-deficient MoSx coatings in humid air is reported based on fretting wear tests. For random-oriented MoSx coatings, the coefficient of friction and the wear volume are still significantly dependent on the relative humidity. On the contrary, basal-oriented MoSx coatings show an interesting low sensitivity to humidity. MoO3 and SO42- have been detected in the wear track and the debris. The amount of MoO3 and SO42- is related to the crystallographic orientation of the coatings and the relative humidity in the fretting wear tests. However, them structure and grain size of the MoO3 debris are not dependent on the relative humidity and the crystal orientation of the coatings. The effect of humidity on the friction and wear of these sulfur-deficient MoSx coatings with different crystallographic orientations is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.