Tribological Performance of Steel With Multi-Layer Graphene Grown by Low-Pressure Chemical Vapor Deposition

To explore the potential of directly grown multi-layer graphene as an agent in reducing friction and wear of steel on steel tribo-pair, multi-layer graphene films were synthesized on GCr15 steel in a low-pressure chemical vapor deposition (LPCVD) setup using a gaseous mixture of acetylene and hydrogen onto a bearing steel substrate. An interlayer of electroplated nickel was deposited on steel to assist and accelerate the graphene deposition. The tribological performance was evaluated using a ball-on-disc tribometer with an average Hertzian pressure of 0.2, 0.28, 0.34, and 0.42 GPa over a stroke length of 5 mm against GCr15 steel ball and compared with bare steel and nickel-plated steel. The results indicate that the friction coefficient is dependent on the applied load and decrease with increasing load, and the minimum friction coefficient of ∼0.13 was obtained for an applied normal load of 1 N; however, the coating failed after 250 cycles. The decrease in friction coefficient has been attributed to the homogenization of the deposited multi-layer graphene along the sliding direction and transfer of graphene to counter-face ball leading to inhibition of metal-metal contact. The investigation suggests that this kind of coating has the potential of improving the tribological performance of metal-metal tribo-pairs.