Tribological evaluation of steel–steel contact surface lubricated by graphene nanoparticle-enhanced lubricant

The aim of the present study is to assess and compare the characteristics such as thermal stability, viscosity and frictional and wear properties of graphene nanoparticle (GNP)-enhanced lubricant against the polyalphaolefins-4 (PAO4) base oil. Four samples with different wt.% concentrations (0.075%, 0.1%, 0.15%, and 0.5%) of GNP-enhanced lubricant samples were synthesized. The thermal stability analysis demonstrated that GNP-enhanced lubricant assists to delay the oxidation onset temperature. The sample with 0.5 wt.% GNP addition showed 21.79 °C higher temperature for oxidation compared to pure base oil. The GNP-enhanced lubricant demonstrated an increment of 33% to 56% in viscosity for varying concentration (from 0.075 to 0.5 wt.%) as compared to pure base oil at 100 °C. The findings indicate that when utilized at an ideal concentration of 0.15 wt.% GNP additive lubricants demonstrate notable improvements in reducing friction coefficient and wear depth by 85% and 80%, respectively, compared to pure base oil.