Tribological properties and self-lubrication mechanism of in-situ grown graphene reinforced nickel matrix composites in ambient air

In situ synthesis of graphene reinforcements in Ni matrix is a promising strategy to manufacture graphene/Ni composites for advanced lubrication . However, the influence of in situ grown graphene content on the tribological properties and the lubricating mechanisms of the graphene/Ni composites under ambient air are far from clear. According to the dissolution and precipitation of carbon on Ni grain surface, this paper reports a high-quality graphene/Ni self-lubricating composite synthesized by in situ powder metallurgy process. The microstructure and tribological behaviours of the composites with different graphene content are elaborated. It is found that the in situ grown few-layer graphene can induce a significant grain refinement effect and simultaneously achieve excellent anti-friction and wear performances. The lowest friction coefficient and wear rate of 0.254 and 4.385 × 10 −5 mm 3 /(N·m) are obtained by the graphene/Ni composite with 0.6 wt% carbon. In comparison with pure Ni, the friction coefficient and wear rate are reduced by 3.02-fold and 3.44-fold, respectively. The tribological improvements of the presented graphene/Ni composite is related to the high H/E ratio and homogenous dispersion of graphene nanosheets .