Structure and oxidation resistance of W1-xAlxN composite films
(1. School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China;
2. Analysis Center, Tianjin University, Tianjin 300072, China)
2. Analysis Center, Tianjin University, Tianjin 300072, China)
Abstract: A series of W1-xAlxN films (0<x<38.6%, mole fraction) were deposited by reactive magnetron sputtering. The composition, microstructure, mechanical properties and oxidation resistance of the films were characterized by EPMA, XRD, XPS, nano-indentation, SEM and HRTEM. The effect of Al content on the microstructure and oxidation resistance of W1-xAlxN films was investigated. The results show that WN film has a face-centered cubic structure. The preferred orientation changes from (111) to (200). The W1-xAlxN films consist of a mixture of face-centered cubic W(Al)N and hexagonal wurtzite structure AlN phases. The hardness of the W1-xAlxN films first increases and then decreases with the Al content increasing. The maximum hardness is 36 GPa, which is obtained at 32.4% Al (mole fraction). Compared with WN film, the W1-xAlxN composite films show much better oxidation resistance because of the formation of dense Al2O3 oxide layer on the surface.
Key words: W1-xAlxN film; microstructure; hardness; oxidation resistance; Al2O3 layer