Effect of Counterparts and Applied Load on the Tribological Behavior of the Graphene-Nickel Matrix Self-Lubricating Composite

Recently, an in-situ method was proposed to fabricate the graphene-nickel matrix (G-Ni) composite by direct growth of few-layer graphene in bulk nickel, achieving the uniform dispersion of graphene into metal matrix. In this paper, G-Ni composite was prepared by in-situ powder metallurgy method followed by a repressing-annealing process to improve densification of specimen. The tribological behavior of the composite sliding against GCr 15, Si3N4, and ZrO2 balls was comparatively investigated under dry friction condition. The results show that the friction coefficient and wear rate are dependent on the counterparts and the applied load. The G-Ni/ZrO2 tribo-pair exhibits the lowest friction coefficient (0.52) and wear rate (9.58x10(-5) mm(3)/Nm) than other tribo-pairs, which can be attributed to good lubrication and protection of the tribofilms formed by tribo-chemical reaction at interface. The friction coefficient for G-Ni/ZrO2 tribo-pair first decreases to a minimum (0.41) at 6N load and then increases associating quite large fluctuations with increasing load. The formation and breakdown of tribofilms are mainly responsible for the tribological behavior at different loads.