Improving tribological performance of chemically bonded phosphate ceramic coatings reinforced by graphene nano-platelets.

To improve tribological performance of chemically bonded phosphate ceramic coatings, the graphene nano-platelets (GNPs) were selected as the reinforcement. Tribological experiment and the analysis of SEM, EDS and Raman were conducted to clarify the mechanism of graphene on the improvement of tribological performance. It was found that, the worn surface of the coating with GNPs is smoother than the one without GNPs, and these GNPs were extruded out and adhered to the worn surface forming the lubricating tribofilm. Besides, the wear volume decreases with the introduction of GNPs. The reason behind this is that these GNPs can lead to the absorption of the fracture energy, which further can improve the mechanical property of the ceramic. This improvement makes the ceramic more tolerant to damage during the wear. Additionally, the decrease of the internal stress of contact surface because of the large contact surface induced by the smooth worn surface results in the lower wear. The friction coefficient shows the similar trends with the wear volume. The lubricant effect of the adhered lubricating tribofilm stemming from the weak interfacial shear strength between graphene platelets dominantly leads to the decrease in friction coefficient. Besides, the smaller internal stress induced by the smooth surface also contributes to the low friction coefficient because of the direct proportionality between the interfacial shear strength and the contact pressure. [ABSTRACT FROM AUTHOR]