Composition, microstructure, and properties of CrNx films deposited using medium frequency magnetron sputtering

CrNx films were deposited on stainless steel and Si (1 1 1) substrates via medium frequency magnetron sputtering in a N2 + Ar mixed atmosphere. The influence of N2 content on the deposition rate, composition, microstructure, mechanical and tribological properties of the as-deposited films was investigated by means of the X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation and tribometer testing. It was found that the N atomic concentration increased and the phase transformed from a mixture of Cr2N + Cr(N) to single-phase Cr2N, and then Cr2N + CrN to pure CrN phase with the increase of N2 content. The Cr 2p3/2 and N 1s of XPS spectra also confirmed the evolution of phase. Accordingly, all films exhibited a typical columnar structure which lies in the zone T of Thornton Model. The mixed Cr2N and Cr(N) phases showed low hardness and high friction coefficient. Cr2N possessed higher hardness than CrN while CrN exhibited lower friction coefficient.