Influence of Ta and Y co-alloying on the structure, mechanical, and thermal properties of TiAlN coatings

Alloying is commonly recognized as an efficient method to enhance the high-temperature properties of TiAlN coatings. In this study, a series of Ti1-x-y-zAlxTayYzN (0.01 <= y <= 0.06, 0.01 <= z <= 0.06) coatings with similar Al content was investigated, concerning phase structure, thermal stability, and oxidation resistance. The presence of an excessive Y-content in Ti0.41Al0.52Ta0.01Y0.06N and Ti0.41Al0.52Ta0.02Y0.05N coatings causes a mixed cubic and wurtzite structure, leading to reduced hardness. A single-phase cubic structure was obtained by low Y-containing Ti1-x-y-zAlxTayYzN coatings with z <= 0.03. Among them, the Ti0.41Al0.52Ta0.05Y0.02N coating obtains the highest hardness value of 34.3 +/- 0.9 GPa in the as-deposited state. Moreover, the thermal stability and oxidation resistance of the Ti0.46Al0.54N coating were significantly improved by co-alloying with Ta and Y. Upon annealing at 900 degrees C, the Ti0.41Al0.52Ta0.05Y0.02N coating shows a peak hardness of 35.8 +/- 1.4 GPa. Increasing Ta-content and decreasing Y-content give rise to a decline in oxide scale thickness when exposed to air at 900 degrees C for 10 h. However, the Ti0.41Al0.52Ta0.05Y0.02N coatings exhibit the best oxidation resistance after oxidation at 1000 degrees C for 15 h with an oxide scale of similar to 3.24 mu m. In general, the Ti0.41Al0.52Ta0.05Y0.02N coatings showed the best comprehensive performance in this work.