Correlation of microstructure and wear resistance of Al2O3-TiO2 coatings plasma sprayed with nanopowders

Abstract

Correlation of microstructure and wear resistance of Al2O3-TiO2 coatings plasma sprayed with nanopowders was investigated in this study. Four kinds of nanostructured Al2O3-13 wt pct TiO2 coatings were fabricated by varying plasma-spraying parameters and were compared with an Al2O3-13 wt pct TiO2 coating fabricated with conventional powders. The nanostructured coatings showed a bimodal microstructure composed of fully melted regions of gamma-Al2O3 and partially melted regions, while the conventional coating mostly consisted of fully melted gamma-Al2O3, together with some TiO2-rich regions and unmelted Al2O3 powders. The wear test results revealed that the wear resistance of the nanostructured coatings was 3 or 4 times better than that of the conventional coating, because the preferential delamination seriously occurred along TiO2-rich regions in the conventional coating. In the nanostructured coatings, TiO2 was homogeneously dispersed inside splats and around, thereby leading to higher splat bonding strength and to better wear resistance over the conventional coating.