Effect of N2 Flow on Microstructure, Mechanical Properties and Oxidation Resistance of CrNx Coatings

Abstract

A series of CrNx coatings were deposited by direct-current reactive magnetron sputtering. The microstructure, the hardness and oxidation resistance of the thin films were characterized respectively with X-ray diffraction (XRD) and nanoindentor. The effect of N2 flow on the microstructure, the hardness and oxidation resistance was studied. It was found that the CrNx film has two phases, the conformation of hcp-Cr2N (hexagonal structure) and fcc-CrN (face-centered cubic). In CrNx film phase structure, with N2 flow increasing, there is the conformation of CrNx films transition from Cr2N to Cr2N and CrN mixed phase, the final CrN single-phase. A single phase of CrNx films has very high hardness while thin film as mixed phase showed a low hardness. CrN has better oxidation resistance with the oxidation resistance temperature of 500°C to 600°C compared to Cr2N. Comparison of Cr2N and CrN on the mechanical properties and oxidation resistance, CrN has better comprehensive performance for protective hard coatings.