Microstructure and wear behavior of graphene nanosheets-reinforced zirconia coating

Zirconia/graphene nanosheets (ZrO2/GNs) composite coatings were prepared using a plasma spraying technique. Microscopic observations showed that the GNs additives (1 wt%) were homogeneously distributed in the ZrO2 matrix and most of them were anchored at the splat interface. The results of wear test indicated that the ZrO2/GNs composite coating exhibited excellent wear resistance and low friction coefficient with the addition of GNs. The wear rate of ZrO2/GNs coating reduced to 1.17×10−6 mm3/N m at 100 N, which corresponded to a 50% decrease compared with the pure ZrO2 coating. Interestingly, a GNs-rich transfer layer was observed on the wear track of ZrO2/GNs coating by field-emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and micro-Raman spectroscopy. This layer protected the ZrO2/GNs composite coatings from severe wear by brittle microfracture, which significantly improved their tribological performance.