Comparative study on mechanical and tribological properties of Cr–Al–N and Cr–Al–O coatings deposited by cathodic arc evaporation

A comparative study was performed for (Cr1−xAlx)2O3 and (Cr1−xAlx)N coatings with different Al contents (x = 0, 0.5, and 0.7) concerning structural, mechanical, and tribological properties. The composition-dependent phase structure was found for Cr–Al–O coatings, where higher Al content promotes a mixed structure of cubic and minor amorphous phases. Moreover, the mixed-phase structure results in lower indentation hardness, ∼27 GPa, and residual compressive stress, ∼ −4 GPa, as compared to Cr2O3 and Cr–Al–N coatings. Besides, (Cr0.5Al0.5)2O3 and (Cr0.3Al0.7)2O3 show worse wear resistance with a wear rate higher than 1.0 × 10−5 mm3/N·m at 200 − 600 °C due to reduced hardness and lower residual stress. A higher bias potential of −150 V induces higher compressive residual stress and hardness, which is beneficial to the high-temperature wear resistance of Cr–Al–O coatings.