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Y. Xu, H. Riedl, D. Holec, L. Chen, Y. Du, P.H. Mayrhofer:
"Thermal stability and oxidation resistance of sputtered TiAlCrN hard coatings";
Surface & Coatings Technology, Supplement C (2017), 324; 48 - 56.

Abstract In recent years, TiAlCrN coatings attract broad research interests owing to their excellent mechanical and tribological properties. Here, we study the thermal stability and oxidation resistance of two Ti1−x−yAlxCryN coating series, having up to 47 at.% Cr (of the metal fraction, hence, y≤0.47) for Al/(Ti+Al) ratios of ~0.55 and ~0.65. All as-deposited Cr-containing coatings are single-phase face-centered cubic (c) structured with hardness values between 32.0 and 33.9GPa. For Cr contents below y<0.38, age hardening due to spinodal decomposition of the Ti1−x−yAlxCryN solid solution is dominant upon annealing in inert atmosphere. But, for Cr contents y≥0.41, the thermodynamically stable wurtzite AlN phase rapidly nucleates upon annealing (accompanied by the dissociation of CrN bonds) leading to a significant hardness reduction above 700°C. Nevertheless, the oxidation resistance constantly increases with increasing Cr and Al content of our single-phased c-Ti1−x−yAlxCryN coatings, because both favor the formation of a dense well-adherent oxide scale and retard the growth of Ti-rich scales. Therefore, our Ti0.18Al0.35Cr0.47N coating - exhibiting the best oxidation resistance among all coatings studied − only exhibits a 1.3-μm-thin oxide scale after 20h exposure to ambient air at 900°C.

http://dx.doi.org/10.1016/j.surfcoat.2017.05.053