Tribological properties and oxidation resistance of tungsten and tungsten nitride films at temperatures up to 500 °C

Abstract

Abstract The paper reports on the structure, microstructure, mechanical and tribological properties and oxidation resistance of WNx films with a stoichiometry x = [N]/[W] ranging from 0 to 1.5 prepared by magnetron sputtering. It was found that (i) films with x ≤ 0.20 exhibit α-W structure and columnar microstructure, while films with x ≥ 0.27 exhibit β-W2N or δ-WN structure and fine-grained microstructure, (ii) the hardness H and hardness to effective Young's modulus H/E∗ strongly affect the tribological properties of the films. Furthermore, we investigate and discuss how the tribological properties are affected by the humidity and by the film oxidation. The oxidation is expressed in terms of the thickness of the WO3 scale, and is shown to be significantly different for x ≤ 0.20 and x ≥ 0.27 WNx films.