Mechanisms of friction and wear reduction by h-BN nanosheet and spherical W nanoparticle additives to base oil: Experimental study and molecular dynamics simulation

Abstract

Hexagonal boron nitride (h-BN) nanosheets, spherical W nanoparticles, and their combinations were utilized as lubricant additives to synthetic PAO6 oil. The addition of W NPs led to a decrease in the coefficient of friction and wear rate. Molecular dynamics (MD) simulations and in situ TEM mechanical tests showed that the positive effect of adding spherical W NPs can be attributed to their rolling and sliding in the tribological contact zone. Adding BN nanosheets to PAO6 also improved the tribological performance of friction pairs: MD simulations suggest that the exfoliation and sliding of BN layers under tribological contact can contribute to the reduction of friction and wear. Moreover, a synergistic effect from the simultaneous addition of W and BN nanoparticles was observed: the CoF and wear reached minimum values among all tested suspensions. The formation of W/BN core/shell structures by wrapping of W nanoparticles by h-BN sheets provided superior macroscale lubricity.