Influence of Nb Doping on Structural, Mechanical and Tribological Properties of VN Film

Abstract

For understanding the influence of Nb element nanocomposite doping on the structure, mechanical and tribological properties of VN films, vanadium nitride(VN) and vanadium niobium nitride(VNbN) films were prepared using reactive magnetron sputtering method, and the microstructure, mechanical behavior and tribological behavior of the two films were compared and analyzed by field emission scanning electron microscopy(FESEM), atomic force microscope(AFM), EDS, XRD, microhardness tester, nanoindenter, friction testing machine, optical microscope and step profiler. Result showed that the doping of Nb element with an atomic fraction of 10.3% led to a higher density of the columnar crystal structure of VNbN thin films, and the surface roughness declined by 45.26%. The nanoindentation results indicated that the hardness of VNbN film was 20.47 GPa, which was 7.51% higher than that of VN film, and the H/E and H3/E2 values were also 18.64% and 49.25% higher than those of VN film, respectively. Tribological analysis revealed that the addition of Nb significantly improved the tribological properties of VNbN thin films at normal atmospheric temperature, with a friction coefficient as low as 0.35 and a wear rate as low as 3.30 × 10-6 mm3/(N·m). Moreover, the friction coefficient of VNbN film at high temperatures of 400 ℃ and 600 ℃ was as low as 0.58, which was also lower than that of VN films. However, its wear resistance significantly decreased at high temperatures, which was due to that the addition of Nb did not improve the oxidation resistance of VN film at high temperatures, the hardness of VNbN thin films deteriorated faster compared to VN film at high temperatures, the load bearing capacity during the rubbing was lower, and the film was easier to fall off.

Keywords

• vnbn film；microstructure；mechanical properties；tribological properties