Quaternary TiZrAlN nanocomposite thin films with a composition of 20.7Ti-22.2Zr-2.7Al-54.4N (at.%) were deposited by the closed-field unbalanced magnetron sputtering (CFUBMS) method and oxidized in air at temperatures between 500 and 700 degrees C. The oxides formed were TiO2, ZrO2, and Al2O3. The films had inferior oxidation resistance because the amounts of ZrO2 and TiO2 were large while the amount of Al2O3 was small. The oxidation progressed primarily by the inward diffusion of oxygen and the outward diffusion of nitrogen. (C) 2009 Elsevier B.V. All rights reserved.