Effect of controlled oxygen incorporation on the structure, mechanical, and High-temperature tribological behavior of AlCrON coatings

Abstract

This study examines the effect of oxygen incorporation on the structural, mechanical, and high-temperature tribological behavior of aluminum-chromium-oxynitride (AlCrON) coatings deposited by cathodic arc physical vapor deposition (PVD). Coatings with low, medium, and high oxygen levels were compared with oxygen-free aluminum-chromium nitride and aluminum-titanium-chromium nitride reference coatings. Grazing-incidence XRD showed that all coatings retained the face-centered cubic nitride structure, with oxygen substituting nitrogen sites and no separate oxide phases detected within the detection limit of the technique. Increasing oxygen content introduced lattice distortion and higher compressive stress, improving hardness in the as-deposited state, whereas post-deposition annealing at 650 °C caused stress relaxation and reductions in hardness and H/E*-H3/E*2 values. High-temperature unidirectional ball-on-disk sliding wear tests were conducted at 650 °C against a 6 mm Al2O3 ball counterbody under both dry and molten Zn-alloy conditions, with each test repeated three times. Under dry conditions, the coating with medium oxygen content exhibited the lowest wear. In the molten zinc alloy tests, oxygen-containing coatings showed superior wear resistance, attributed to the formation of a ZnO rich tribochemical layer at the sliding interface, identified by Raman and XPS analyses of the wear tracks, which acted as a self-limiting barrier against direct metallic contact and suppressed severe liquid-metal adhesion. These results demonstrate that optimized oxygen addition enhances the tribochemical stability of aluminum-chromium-based coatings for demanding die-casting environments.