Tribological behavior of ZnO-Si₃N₄ nanoparticles-based lubricating grease

Currently, nanoparticles have been widely used as lubricant additives, few researches have investigated their applications as additives for lubricating grease. In this paper, mixtures of ZnO and Si3N4 nanoparticles were added into grease as additives. XRD and TEM were utilized to the investigate phase composition, microstructure and morphology of the nanomaterials. The composite grease was prepared by introducing ZnO and Si3N4 nanoparticles into the grease matrix through ultrasonic dispersion. Then, tribological properties of the composite grease were measured through a MMW-1A universal friction tester. Results showed that the best lubrication performance was achieved when the composite grease contains 1 wt% ZnO and 0.5 wt%Si3N4. Under this condition, the friction coefficient and wear scar diameter decreased to 0.0701 and 0.727, which is 34.3% and 8.3% lower than that of the base greases, respectively. The morphology of composite nanoparticles is beneficial to the enhancement of antifriction property, which can be seen from SEM images. In addition, EDS analysis illuminated the accumulation of Zn and Si on the friction surface. Further researches proved its great potentials in alleviation of vibration, noise and temperature rise for high speed bearings, since the ZnO-Si3N4 nanoparticles-based composite grease showed excellent lubrication and antifriction properties.