Oxidation behaviour of CrAlYN coatings at elevated temperatures

CrN/AlN nanolayered coatings with different Y doping levels were deposited to understand the effects of Y on the oxidation behaviour of the coatings at elevated temperatures. The coatings were deposited in a hybrid HIPIMS and magnetron sputtering deposition system, and their chemical composition and mechanical properties were characterized using EDS and nanoindentation tests respectively. The as-deposited coatings were annealed in air at 800 °C and 1100 °C for 1 h, and the evolution of coating microstructure were characterized by GI-XRD and FIB assisted cross-sectional SEM imaging. Different oxidation behaviours were observed at 800 °C and 1100 °C. At 800 °C, coating oxidation is dominated by the formation of Cr2O3, while at 1100 °C, the oxidation is characterized by the competing growth of Cr2O3 and Al2O3 scales. The Y content significantly influenced the oxide scale formation and voids distribution in the coatings, and this was attributed to the role of Y in changing the diffusion processes both within the coating and at the coating-air interface.