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 (9.58 × 10⁻⁵ mm³/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 6 N 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.