Pulsed laser deposition of antifriction thin-film coatings in vacuum and inert gas

Abstract

MoSe x coatings were obtained by pulsed laser deposition in vacuum and inert Ar gas atmosphere at the pressure from 1 to 10 Pa. The deposition temperature was 200 0 С. The films were studied by means of X-ray diffraction, scanning and transmission electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy of helium ions. The tribological properties of thin film coatings were investigated by pin-on-disk testing in air with 50% relative humidity. Chemical composition, structure, and tribological properties of the coatings were found to be sensitive to the presence of the inert gas. Thus, increasing the gas pressure from 1 to 10 Pa changes the chemical composition, so that the value of x increases from 1.5 to 2.4 in the principal deposition zone. At the optimal gas pressure (~ 2 Pa), the composition of the coating was close to the stoichiometric one, and the layer adjacent to the substrate consisted of MoSe x nano-crystals with the basal planes parallel to the substrate surface or oriented at small angles to the surface. The tribological properties of MoSe x coatings deposited on steel substrates depend on the gas pressure. The friction coefficient in air decreases from 0.08 for deposition in vacuum to 0.04 for deposition at the optimal pressure.