Microstructure and mechanical properties of W–Ni–N coatings prepared by magnetron sputtering

• W–Ni–N coatings were fabricated by magnetron sputtering technique.
• W–10 at.% Ni–N coating consisted of nc-W2N + nc-Ni3N + nc-Ni.
• The maximum hardness of W–Ni–N coating is 38 GPa.

W–Ni–N coatings were fabricated by direct current magnetron sputtering technique. The influence of Ni content on the microstructure, surface morphology and mechanical properties of coatings was investigated by using X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, nanoindentation and scratch tests. The results showed that the addition of Ni into W–N coatings induced a change of grain morphology from polygon to granular shape leading to the reduction in contact area between the coating and the substrate. The roughness of coatings also decreased upon the addition of Ni. Therefore, the adhesion strength of W–Ni–N decreased from 60 to 38 N as Ni content is increased from 0 to 21 at.%. In contrast, the hardness increased slightly at first and then decreased with Ni concentrations. The maximum hardness of 38 GPa was obtained at 10.2 at.% Ni, corresponding to a composite structure consisting of nc-W2N + nc-Ni3N + nc-Ni.