Oxide scales formation in nano-crystalline TiAlCrSiYN PVD coatings at elevated temperature

Nano-crystalline TiAlCrSiYN plasma vapor deposited (PVD) coatings were developed for oxidation and wear protection at elevated temperatures. Compositional tuning of the coatings was performed to enhance oxidation protection at elevated temperatures. The oxidation kinetics of the coatings has been studied over 180 h at 900 degrees C in air. Post-oxidation microstructural examinations of specimens were performed using transmission electron microscopy (TEM), secondary electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and glow discharge optical emission spectroscopy (GDOES). Micro mechanical characteristics of the coating were studied using a micro materials nanotest system. Wear resistance of the coatings were studied during turning of Inconel 718. Experimental results clearly indicate that the aluminum-rich PVD TiAlCrSiYN coatings with 60 at.% of Al can improve oxidation resistance of titanium aluminide alloy at the temperature 900 degrees C as well as wear resistance during machining of Inconel 718. It was shown that during oxidation, continuous protective alumina-based oxide films form on the surface. These oxides are predominantly (Al,Cr)(2)O-3-based films. Self-healing behavior of the TiAlCrSiYN coatings was observed in its ultra-fine nano-crystalline structure. (C) 2009 Elsevier Ltd. All rights reserved.