Effect of sputtering power on the chemical composition, microstructure and mechanical properties of CrNx hard coatings deposited by reactive magnetron sputtering

In this study, the CrNx coatings were deposited by reactive magnetron sputtering at varying sputtering power from 200 to 300 W. The chemical composition, phase structure, surface and cross-sectional morphologies, and mechanical properties of the coatings were respectively investigated by electron probe microanalysis, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and nano-indentation measurements. The results show that the coating deposited at a sputtering power of 200 W is a single-phase fcc CrN with columnar structure, while the coatings deposited at sputtering powers of 250 and 300 W are consisted of hexagonal Cr2N and fcc CrN with nano-composite structure. As compared with the single-phase Cr2N or CrN coatings, the composite coatings exhibit both higher hardness and superior resistance to plastic deformation and cracking, which is attributed to their unique nano-composite structure.