Influence of silver content on structure, mechanical and tribological properties of WCN–Ag films

Abstract

In recent years, the preparation of thin films with excellent tribological properties over a wide temperature range has attracted the attention of the researchers. It is reported that an effective way is the fabrication of films consisting of different lubricant phases, which exhibit self-lubricating characteristics at different temperatures. On this basis, WCN–Ag films with various silver contents ranging from 0 to 8.3at.% were deposited by a multi-target magnetron sputtering system. The composition, structure, mechanical and tribological properties were characterized using XPS, XRD, HRTEM, nano-indentation, ball-on-disk dry sliding wear tester, Bruker 3D Profiler, SEM and compared to WCN. It is found that the incorporation of silver does not change the cubic structure, WCN–Ag films consist of a mixture of WCN, W2N, Ag, amorphous C and CNx phases. Although the addition of Ag into WCN films reduces the hardness, Young's modulus and compressive stress, it improves the tribological properties obviously. A low friction coefficient (<0.4) is observed in the temperature range of 25–600°C for WCN–Ag film containing 6.6at.% Ag. Overall, the results reveal that WCN–Ag films by adding some Ag content can exhibit self-lubricating characteristics in the temperature range of 25–600°C.