Relationship of Endurance to Microstructure of IBAD MoS2Coatings

The endurance of ion-beam-assist-deposited (IBAD) MoS2 is correlated with coating structure and orientation. Structure and orientation are determined by X-ray diffraction, while endurance is measured with a ball-on-disk tribometer operating in dry air. The IBAD MoS2 coatings contain both crystalline and non-crystalline components. Only two orientations of the crystalline component are observed: the (001) planes parallel (basal orientation) and perpendicular (edge orientation) to the surface. Endurance of the coating is not related to coating thickness or substrate chemistry, but is related to the relative amount of the two MoS2 crystal orientations. Coating endurance decreases with increasing edge (100) intensity. Furthermore, MoS2 coatings with poor crystallinity exhibit good endurance. These results are discussed in terms of a possible oxidative wear mechanism and stress-induced basal re-orientation of the non-crystalline IBAD MoS2.