Effect of Graphene-Based Nanoadditives on the Tribological and Rheological Performance of Paraffin Grease

The present study deals with tribological and rheological evaluations of paraffin grease having variable dosages (0.01-0.05 wt.%) of graphene oxide (GO), reduced graphene oxide (rGO), and octadecylamine-functionalized GO (GO-ODA). The microstructural and chemical characteristics of GO, rGO, and GO-ODA were analyzed by HRTEM, XRD, and FTIR. The graphene-based nanoadditives significantly improved the tribological properties between the steel tribo-pair by decreasing the wear and friction. The optimized dose of GO, rGO, and GO-ODA decreased the coefficient of friction (COF) by ~ 34.3, ~ 50.3, and ~ 34.3%, and wear volume by ~ 86.6, ~ 85.4, and ~ 80.9%, respectively. The friction reduction by GO, rGO, and GO-ODA nanoadditives conserved the energy by ~ 34.3, ~ 50.3, and ~ 34.4%, respectively. The spectroscopic and microscopic analyses of worn surfaces suggested the formation of graphene-based tribo-film, which facilitated the shearing under tribo-stress and protected the tribo-interfaces against the wear. The rheological results corroborate the roles of graphene-based nanoadditives and lube oil of grease under the tribo-stress, which is vital for the sustainability of tribo-film on the interacting surfaces. The graphene-based tribo-film reduced the friction, subsidized the wear, and conserved energy consumption.