Influence of oxygen addition on the structure, mechanical and thermal properties of CrN coating.

In this study, the effect of oxygen addition on the structure, mechanical and thermal properties of CrN coatings was investigated. CrN, Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings reveal a single-phase cubic structure, and further increasing oxygen content results in the formation of a corundum structured Cr 2 O 3 coating. An increased hardness from ~16.9 GPa for CrN to ~21.9 GPa for Cr 0.50 O 0.07 N 0.43 , ~27.0 GPa for Cr 0.47 O 0.22 N 0.31 , and finally ~28.6 GPa for α-Cr 2 O 3 is obtained. Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings show a deferred onset temperature of nitrogen loss than CrN by ~100 °C. During annealing, the hardness value of the CrN coating decreases to ~11.3 GPa at 900 °C and then inversely increases to ~17.9 GPa at 1200 °C, while those of Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings exhibit a continuous drop to ~14.5 and ~20.6 GPa at 1200 °C, respectively. The oxidation resistance of Cr-O-N coating is closely related to oxygen content. After oxidation at 800 °C for 20 h, the oxide scales of CrN, Cr 0.50 O 0.07 N 0.43 and Cr 0.47 O 0.22 N 0.31 coatings are ~0.22, ~0.16 and ~0.55 μm in thickness, respectively. In addition, the Cr 2 O 3 coating always retains excellent mechanical and thermal properties regardless of in Ar or synthetic air. • O-addition into CrN causes a structural transformation from cubic to hexagonal. • The O-containing coatings reveal higher hardness than CrN coating. • Doping with O into CrN postpones the onset temperature of N-loss by ~100 °C. • The oxidation resistance of Cr-O-N coating is closely related to the O content. [ABSTRACT FROM AUTHOR]