A comparative study of the oxidation behavior of Cr2N and CrN coatings

Abstract

A comparative study of the oxidation behavior of Cr2N and CrN coatings was investigated in air at temperatures ranging from 700 degrees C to 1000 degrees C including phase structure, surface and cross-sectional morphologies, oxidation kinetics and mechanism. During oxidation, the dense Cr2O3 scales form both on the Cr2N and CrN coatings. The Cr2N phase transforms to CrN phase, which is accompanied with 20% volume expansion in transverse. This volume expansion induces the porous and non-columnar cross-sectional morphology of the Cr2N coating. The worse oxidation resistance of the Cr2N coating compared with the CrN coating is attributed to its higher chromium content and phase transformation induced porous structure. The oxidation activation energy values are 139 and 190 kJ/mol for the Cr2N and CrN coatings respectively, which is comparable to the literature results. Marker experiments prove that the growth of Cr2O3 scales is controlled by both the outward diffusion of chromium and inward diffusion of oxygen and the outward diffusion of chromium is dominated. (C) 2013 Elsevier B. V. All rights reserved.