Tribological properties of nanometer cerium oxide as additives in lithium grease

Abstract This paper presents a comparative study of the influence of nanometer-CeO 2 (nano-CeO 2 ) and temperature on tribological and lubricating properties of lithium grease. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Friction and wear tests were conducted on the friction and wear tester. Results show that the lithium grease with addition of nanometer-CeO 2 has much better friction-reducing and anti-wear performance than that of base grease. When the additive in grease is 0.6 wt%, the friction coefficient (COF) and wear scar diameter (WSD) decrease by 28% and 13% comparing with base grease, respectively. The base grease and grease with 0.6 wt% nanometer-CeO 2 both possess the lowest average COF and wear width at 50 °C. The worn surface morphology after friction test was analyzed by scanning electron microscopy (SEM) and NANOVEA three-dimensional profilometer. Under the lubrication of the lithium grease containing 0.6 wt% nano-CeO 2 , few shallow furrows can be observed on the quite smoothed surface and the WSD decreased. Moreover, It was found that the nano-CeO 2 has been incorporated into the surface protective and lubricious layer by energy dispersive spectrometer (EDS) analysis.