Influence of Cu content on the structure, mechanical and tribological properties of W2N-Cu films

W2N-Cu films with different Cu content ranging from 0 to 6.22 at.% were deposited by reactive magnetron sputtering technique. The structure, mechanical and tribological properties were investigated by XPS, XRD, HRTEM, nano-indentation CSM, high-temperature ball-on-disc tribo-meter, Bruker 3D Profiler. The results indicated that the incorporation of copper did not affect the cubic structure. W2N-Cu films consist of W2N and Cu crystal phases. An addition of copper induced W2N crystallite size refinement accompanied by increase in hardness with a maximum at 0.9 at.% Cu. At room temperature, the friction coefficient of W2N-Cu films decreased gradually and the wear rate increased with increasing Cu content. At high temperatures, the friction coefficient of W2N-Cu films decreased with increasing Cu content but the wear rate increased. Overall, the results reveal that the friction properties of W2N-Cu films, in the temperature range of 25- 600 °C, can be improved by addition of a copper element, but the wear resistance failed to improve under same conditions.