Exploring the potential of graphene nanoplatelets as a lubricant additive: Topography evolution and performance under boundary lubrication conditions

This work investigates the friction and wear reduction effects of adding functionalized graphene nanoplatelets (GNPs) to a fully formulated engine oil. Friction tests using a continuous sliding/rolling ball-on-disk tribometer showed that 0.2 wt% GNP oil reduced friction by up to 28% and 11% in the boundary and elastohydrodynamic lubrication regimes, respectively. The disk tested with GNP oil also exhibited lower wear and evidence of carbon tribofilm formation. Raman spectroscopy indicated that the mechanical stresses in the tribological tests altered the graphene morphology. Furthermore, the study evaluated the literature mechanisms for graphene-induced friction and wear reduction, and concluded that the interplay between interlaminar shearing and protective film formation mechanisms was the most plausible explanation for the obtained results.