Microstructure and wear resistance of nanostructured Al2O3–8wt.%TiO2 coatings plasma-sprayed with nanopowders

Microstructure and wear resistance of nanostructured Al2O3–8wt.%TiO2 coatings plasma-sprayed with nanopowders were investigated in this study. Four types of nanostructured Al2O3–8wt.%TiO2 coatings were plasma-sprayed on a low-carbon steel substrate by using different critical plasma spray parameters (CPSP). The nanostructured coatings consisted of completely melted region of γ-Al2O3 phase and partly melted region, and the fraction of the partially melted regions and pores decreased with increasing CPSP. The hardness and wear test results revealed that the hardness of the coatings increased with increasing CPSP, and that the coating sprayed with the lowest CPSP had the best wear resistance, while its hardness was lowest. The main wear mechanism was a delamination one in the coating sprayed with the high CPSP, but was changed to an abrasive one in the coating sprayed with the low CPSP. According to this change in the wear mechanism, the wear resistance was not proportionally increased with the hardness, and was the best in the coating sprayed with the lowest CPSP.