Influence of Si content on the microstructure, thermal stability and oxidation resistance of TiAlSiN/CrAlN multilayers

Abstract In order to optimize the overall properties of CrAlN coating, TiAlSiN insertion layer with exceptional thermal stability are introduced into CrAlN coating. Based on the template effect of CrAlN layer, the Ti0.53Al0.38Si0.09N layer can be stabilized in a metastable cubic structure, and thus exhibits a high hardness of 33.8 ± 0.7 GPa, whereas the Ti0.48Al0.38Si0.14N layer still crystalize in the mixed cubic and wurtzite structure, and shows a low hardness of 28.9 ± 0.9 GPa. TiAlSiN insertion layer improves the thermal stability of CrAlN coating by suppressing the breakage of Cr–N bonds. Additionally, TiAlSiN/CrAlN multilayers reveal an age-hardening ability and also higher hardness than Cr0.32Al0.68N coating during annealing up to 1200 °C. Compared with Cr0.32Al0.68N coating, TiAlSiN/CrAlN multilayers show inferior oxidation resistance below 1000 °C, but better antioxidative performance at higher temperatures. Furthermore, Ti0.48Al0.38Si0.14N/CrAlN CrAlN exhibit better oxidation resistance than Ti0.53Al0.38Si0.09N/CrAlN due to the elevated Si content. On the whole, Ti0.53Al0.38Si0.09N/CrAlN multilayer reveals the best comprehensive properties.