Tribological behaviors at high load of MoS_x/Au films in vacuum

MoS_x/Au films about 1μm in thickness were deposited on 9Cr18 steel substrate discs by magnetron sputtering method. The chemical composition and chemical states of the as-deposited films were determined by X-ray photoelectron spectroscopy (XPS). The effect of high loads (15∼50N) on tribological behaviors of the MoS_x/Au films in vacuum was studied by pin-disc wear tests. The pins were made of 2Cr13 steel. The morphologies of as-deposited films and wear track were observed by scanning electron microscopy (SEM). The results show the friction coefficient and the wear life of the films decrease with the increase of load at a sliding velocity of 1.6 m·s ^-1. The wear life of the films at 15N can reach 2000m. The friction process of the films can be divided into four stages based on typical variation of friction coefficient with sliding time in vacuum, e.g. running-in stage, steady stage, severe damage stage and thorough wear stage. In steady stage, the films peel in small pieces and the abrasion mechanism appears delamination wear. When the film was damaged thoroughly, the wear test carried out between 2Cr13 pin/9Cr18 disc. The adhesive wear becomes the dominant abrasion mechanism.