Effects of Water Vapor on the Oxidation Behaviors of Cr-Al-N Coatings

Cr1-xAlxN coatings with different aluminum content were deposited on K38G alloy by reactive magnetron sputtering method. Oxidation behaviors of these coatings were investigated at 1000 degrees C in air+10 vol.% water vapor. The surface morphologies and the microstructure of the oxide scales were analyzed by SEM and XRD, respectively. The results showed that the oxidation of the Cr1-xAlxN coatings in the wet air also obeyed the parabolic law; however, compared to that in the dry air, existing of 10 vol. % water vapor increased the parabolic rate constants of the coatings. It was believed that the accelerating of the oxidation rates was owing to easily outwards diffusion of Cr through the looser and coarser oxide scales formed on the surface of the coatings when oxidized in wet air.