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

In order to optimize the overall properties of CrAlN coating, TiAlSiN insertion layers with exceptional thermal stability are introduced into CrAlN coating. Based on the template effect of CrAlN layer, the Ti 0.53 Al 0.38 Si 0.09 N layer can be stabilized in a metastable cubic structure, and thus exhibits a high hardness of 33.8 ± 0.7 GPa, whereas the Ti 0.48 Al 0.38 Si 0.14 N layer still crystallizes in the mixed cubic and wurtzite structure, and shows a low hardness of 28.9 ± 0.9 GPa. TiAlSiN insertion layers improve 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 Cr 0.32 Al 0.68 N coating during annealing up to 1200 °C. Compared with Cr 0.32 Al 0.68 N coating, TiAlSiN/CrAlN multilayers show inferior oxidation resistance below 1000 °C, but better antioxidative performance at higher temperatures. Furthermore, Ti 0.48 Al 0.38 Si 0.14 N/CrAlN exhibit better oxidation resistance than Ti 0.53 Al 0.38 Si 0.09 N/CrAlN due to the elevated Si content. On the whole, Ti 0.53 Al 0.38 Si 0.09 N/CrAlN multilayer reveals the best comprehensive properties. • Ti 0.53 Al 0.38 Si 0.09 N/CrAlN multilayer exhibits the highest hardness of ∼33.8 GPa. • The introduction of TiAlSiN optimizes the thermal stability of CrAlN. • TiAlSiN improves the high-temperature oxidation resistance of CrAlN above 1000 °C. • Increasing Si content improves the oxidation resistance of TiAlSiN/CrAlN. [ABSTRACT FROM AUTHOR]