"Effect of nano graphite on the wear resistance of the Al2O3-TiO2 plasma sprayed coatings"

In this paper, the effect of nano graphite on tribological properties of Al₂O₃-TiO₂ coatings was studied. Different content of nano graphite was added into the nano-structured Al₂O₃-TiO₂ sprayable feedstocks by ball milling process. The wear resistance of the coatings was studied by performing dry sliding wear tests under normal loads of 5N, 10N and 15N. The results of wear tests showed that graphite could improve the wear resistance of the coatings. The friction coefficient decreased with the increase of nano graphite under different normal loads. Nano graphite decreased the wear rate of the coatings remarkably. The coating with 12wt.% nano graphite decreased by 23% compared to the coating without nano graphite under the normal load of 5N. But when the normal load was 15N, the coating with 12wt.% nano graphite decreased by 63% compared to the coating without nano graphite. The content of carbon (C) on the worn surfaces of the coatings with nano graphite was larger than that on the worn surface of the coating without nano graphite, indicating that graphite was adhered on the worn surfaces during the wear process. The adhered graphite acting as lubricant could separate the coatings and the counter balls efficiently.