A Si-Nb co-alloyed AlCrN coating with good mechanical properties, excellent thermal stability and resistance to high temperature oxidation.

The thermal properties of AlCrN coatings influence their application in harsh mechanical environments. This paper introduces a Si-Nb co-alloying strategy to prepare AlCrN-based coatings with good mechanical properties, excellent thermal stability and resistance to high temperature oxidation for developing high-performance tool coatings. The results indicate that, benefiting from the synergistic effect of replacing a portion of Si with an appropriate amount of Nb, Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating exhibits a fine columnar crystal structure different from the featureless dense structure of Al 0.60 Cr 0.32 Si 0.08 N coating. The different microstructure results in the difference of mechanical properties. Therefore, Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N has a higher hardness (32.3 ± 0.8 GPa) than Al 0.60 Cr 0.32 Si 0.08 N (28.8 ± 0.8 GPa). Meanwhile, the Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating get a better thermal stability and a comparable resistance to high temperature oxidation as Al 0.6 Cr 0.32 Si 0.08 N coating. The temperatures of thermal decomposition and oxidation resistance for Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating are increased by about 125 °C and 175 °C, respectively, compared with Al 0.66 Cr 0.34 N coating. In addition, the Si-Nb co-alloyed coatings maintain a better hardness after annealing. • Si-Nb co-alloying can improve the mechanical and thermal properties of AlCrN-based coatings. • Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating shows better hardness than Al 0.6 Cr 0.32 Si 0.08 N coating. • Nb addition retains the excellent thermal properties of Al 0.6 Cr 0.32 Si 0.08 N coating. • The thermal decomposition onset temperature of Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating is ~1075 °C. • The oxidation resistance onset temperature of Al 0.59 Cr 0.31 Si 0.06 Nb 0.04 N coating is ~1275 °C. [ABSTRACT FROM AUTHOR]