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

Abstract

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, Al0.59Cr0.31Si0.06Nb0.04N coating exhibits a fine columnar crystal structure different from the featureless dense structure of Al0.60Cr0.32Si0.08N coating. The different microstructure results in the difference of mechanical properties. Therefore, Al0.59Cr0.31Si0.06Nb0.04N has a higher hardness (32.3 ± 0.8 GPa) than Al0.60Cr0.32Si0.08N (28.8 ± 0.8 GPa). Meanwhile, the Al0.59Cr0.31Si0.06Nb0.04N coating get a better thermal stability and a comparable resistance to high temperature oxidation as Al0.6Cr0.32Si0.08N coating. The temperatures of thermal decomposition and oxidation resistance for Al0.59Cr0.31Si0.06Nb0.04N coating are increased by about 125 °C and 175 °C, respectively, compared with Al0.66Cr0.34N coating. In addition, the Si-Nb co-alloyed coatings maintain a better hardness after annealing.