Improved Tribological Performance of Amorphous Carbon (a-C) Coating by ZrO(2) Nanoparticles

Nanomaterials, such as Graphene, h-BN nanoparticles and MoS(2) nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C) coatings. In the current study, the effectiveness of ZrO(2) nanoparticles (ZrO(2)-NPs) in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO(2)-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO(2)-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO(2)-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO(2)-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO(2)-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO(2)-NPs is an effective, long lasting and environment-friendly lubrication solution.