Abstract
The thermal oxidation of TiN, CrN and TiAlN films were studied in air at temperature from 650 C to 900 C. These nitride films were deposited onto stainless steel substrates using an arc ion-plating method. Oxidation rates were calculated by the weight changes with times. Formed oxide layers were analyzed by XRD, SEM and AES. The oxidation rates were found to fit well to a parabolic time dependence. The high dependence of oxidation rates on film materials was evident from the Arrhenius plots of the calculated rate constant. The calculated activation energy of 32.5 kcal/mol for oxidation of TiN was less than that of 43 kcal/mol for oxygen diffusion, in TiO 2 . This difference suggested that the oxidation of TiN is enhanced by grain boundary diffusion of oxygen in formed oxide film. The activation energy for CrN was 60.1 kcal/mol, which was almost same value as that of diffusion of Cr ion in Cr 2 O 3 . The oxidation reaction of Ti 0.9 Al 0.1 N is much faster than that of Ti 0.6 Al 0.4 N and the activation energies were 51.5 kcal/mol and 112.6 kcal/mol respectively. The activation energy for Ti 0.6 Al 0.4 N was almost same as that of diffusion of Al ion in Al 2 O 3 .
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