Mechanical and tribological properties of plasma sprayed NiAl composite coatings with addition of nanostructured TiO2/Bi2O3

Spray-dried nanostructured TiO2/Bi2O3 feedstock powders were successfully incorporated into plasma sprayed NiAl composite coatings. The tribological properties of the composite coatings from RT to 800 °C were investigated. The results show that the nanostructured TiO2/Bi2O3 phases performed the typical bimodal microstructure resulting in a significant enhancement of mechanical and tribological properties of the composite coatings. The lowered friction and wear at 800 °C is attributed to the synergistic lubricating effect of Bi4Ti3O12 and NiTiO3 formed on worn surfaces by tribo-chemical reactions together with TiO2 and NiO. A continuous lubricating layer including NiTiO3 and Al2TiO5 was formed on counterfaces, which further improved the tribological behavior of composite coating at high temperatures.