The degradation of CrN films was investigated over temperatures of 400-1200 degreesC in air, nitrogen, and forming gas (N-2/H-2 = 9) by analyzing changes in color and appearance, as well as microstructures. The degradation mainly included color changes and cracks occurring on the film surface. The color change resulting from low-temperature/short-time annealing was due to the formation of an additional Cr2N phase, as well as a thin oxide overlayer. The color change appearing at higher temperatures/longer times stemmed from the formation of a thicker Cr2O3 layer, whose content depended on the pN(2)/pO(2) ratio in the atmosphere. The driving force of the oxidation was the Gibbs free-energy change for CrN and Cr2O3 . Cracks that showed up at relatively high temperatures were attributed to the large thermal mismatch between the CrN film and Cr2O3 overlayer. The thermal stresses were calculated and discussed. The degradation diagrams were generated based on the above analyzed results. (C) 2003 American Vacuum Society.