Abstract:WS_x/a-C nanometer multilayer films with modulation period of 4-23 nm were deposited by magnetron sputtering graphite target and WS₂ target alternately. The microstructures of the films and the chemical valence state of the elements were analyzed by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The hardness, adhesion to the substrate and tribological behavior of the films under humid air (RH 70%) were investigated by nano-indenter test, scratch test and ball-on-disk tribometer. The results show that the multilayer films have compact microstructure and smooth surface. The addition of a-C (amorphous carbon) layer to the films leads to the crystallinity change of WS₂ phase, the multilayer films are amorphous structure. With the increase of the modulation period, the mole ratio of S to W of the films decreases to a constant value of about 1.32, the hardness increases slowly while the adhesion decreases apparently. The friction coefficient of the films decreases from 0.32 to 0.26, and the wear rate increases, but it is remarkably lower than that of WS_x film. The film with modulation period of 4 nm shows the best wear resistance, and the wear rate is 1.03×10^{-13 m3}？N^-1？m^-1.

Key words: WS₂; multilayer films; modulation period; microstructure; friction; wear