Selective release of less defective graphene during sliding of an incompletely reduced graphene oxide coating on steel

Recently, graphene has been gaining a lot of attention as a coating material that can be effectively utilized in reducing friction and wear of sliding components. In order to fully exploit the lubricious properties of graphene, the variation in the structure of the coating as sliding proceeds against a counter surface needs to be understood clearly. In this study, the structural evolution during sliding of an incompletely reduced graphene oxide (rGO) coating deposited on the 304 stainless steel by an electrodynamic spraying process was investigated. Experimental results showed that this coating possessed a low friction coefficient, below 0.05, under either low humidity air or dry N-2 gas condition. The micro-Raman and XPS analyses systematically revealed that less defective graphene structure was selectively released at the center region of the wear track. It was determined that the redistribution of graphene with different structures within the wear track was induced by frictional interaction at the sliding interface. Furthermore, it was determined that the degree of release of less defective graphene structure was proportional to both the applied normal force and sliding cycles. (C) 2018 Elsevier Ltd. All rights reserved.