A superhard CrAlSiN superlattice coating deposited by a multi-arc ion plating: II. Thermal stability and oxidation resistance

According to Part I, the as-deposited CrAlSiN coatings have the superlattice structure containing alternating fcc-(Cr, Al)N and h-(Al, Si)N nanolayers. In this part, for the applications of the CrAlSiN coatings on high-speed cutting tools and/or anti-wear parts at high temperatures, the thermal stability of CrAlSiN superlattice coatings was investigated by vacuum annealing at elevated temperatures of 700 °C, 900 °C and 1100 °C for 2 h, respectively. The phase structures and mechanical properties of CrAlSiN coatings before and after vacuum annealing were investigated. The results indicated that the coating structures and mechanical properties remained nearly unchanged up to 900 °C. Since the fcc-CrN phase decomposed into h-Cr2N, cubic Cr and Al80Cr20 phases, the hardness of the coating after annealing at 1100 °C reduced from 48 ± 2 GPa to 39 GPa and the adhesion strength increased from 50 GPa to 60 GPa simultaneously. Moreover, the coatings exhibited higher oxidation resistance with the formation of crystalline Al2O3 phases on the surface.