The CrNxOyCz coatings were deposited by planar DC reactive magnetron sputtering onto AZ31 Mg alloy and high speed tool steel (HSTS) substrates at a substrate temperature of 200 degrees C. The effect of N-2 content on composition and structure of the CrNxOyCz coatings was investigated. The structure of the CrNxOyCz coatings was analyzed by a glancing angle X-ray diffraction (GXRD). The cross-section morphology and thickness of the CrNxOyCz coatings were checked by a field emission scanning electron microscope (FESEM), and the composition pro. le and chemical state were carried out by an X-ray photoelectron spectroscopy (XPS). The experimental results showed that the structure and phase composition of the CrNxOyCz coatings depended on N-2 content. The evolution of the structure of CrNxOyCz coatings was consistent with CrNx-based coatings, and the CrNxOyCz coatings contained Cr2O3, CrO2, CrO, Cr3C2, CrNx (Cr, CrN, Cr2N), as well as different chromium oxynitride. However, the carbide and oxynitride were oxidized after annealing. (C) 2008 Elsevier B.V. All rights reserved.