Influence of Ag Content on Microstructure, Mechanical and Tribological Properties of WNbN-Ag Composite Films

Abstract

WNbN composite films with different Ag content were deposited by reactive multi-target magnetron sputtering. The microstructure, mechanical and tribological properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), high resolution transmission electron microscopy (HRTEM), nano-indentation and ball-on-disc tribo-mter analysis. The results indicated that WNbN-Ag film consists of face-centered cubic (fcc) WNbN, face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and face-centered cubic (fcc) Ag. The hardness and elastic modulus of WNbN-Ag composite film decreases gradually as Ag content increases from 0 to 25.23 at %. At room temperature, the friction coefficient of the film firstly increases and then decreases, while the wear rate gradually increases with the increasing Ag content. As the temperature increases from room temperature to 700°C, the friction coefficient firstly increases and then decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures influenced the hardness, the tribo-films and wear mechanism of the film.