Tribological properties of hexagonal boron nitride nanoparticles as a lubricating grease additive

The friction and anti-wear behaviours of hexagonal boron nitride (h-BN) nanoparticles as a lithium lubricating grease additive are being investigated under sliding conditions. The grease with 3 wt% 60 nm h-BN particles and the grease with 1 wt% 500 nm h-BN particles lead to 22.34% and 20.18% reductions in the wear scar diameter, respectively, although the friction coefficients slightly decrease. The boric acid H₃BO₃ with layer-crystal structure produces during the friction process, and the synergistic effect of h-BN nanoparticles and H₃BO₃ makes friction reduction and wear-resistant enhancement. Furthermore, the 60 nm h-BN particles filled in the asperity valleys of the friction surface make a rolling effect and establish a protective film, while the 500 nm h-BN particles shield the asperity contact between friction pairs and make a polishing effect as well.