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

MoSex 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°C. 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 MoSex nano-crystals with the basal planes parallel to the substrate surface or oriented at small angles to the surface. The tribological properties of MoSex 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.

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