Comparative investigation of the influence of CaCO3 and SiO2 nanoparticles on lithium-based grease: Physical, tribological, and rheological properties

Due to their special features, nanoparticle additives have been suggested to enhance lubricant performance in various situations. Working in harsh environments also requires lubricating greases with excellent tribological properties and high corrosion resistance. The impact of calcium carbonate (CaCO3) and silica (SiO2) nanoparticles (NPs) on the physical, tribological, and rheological properties of lithium-based grease are investigated in this research. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction (XRD) analyses were used to examine the morphology of NPs and crystalline structures as well as their particle size distributions. For the preparation of nano-grease, different weight percentages of CaCO3 and SiO2 nano-additives (0.5, 1, and 2 wt%) were dispersed separately in the lithium-based grease with the aid of a two-stage approach. The results revealed that the physical, tribological, and rheological properties of all of the nano-greases prepared with CaCO3 and SiO2 nano-additives were improved in comparison with lithium-based grease. Furthermore, 1 wt% of CaCO3 (as the optimal concentration) in comparison with lithium-based grease, significantly reduced friction and wear, reduced water washing by 40%, increased thermal stability (69%), and reduced cone penetration rate (33%). It is attributed to a protective layer of nanoparticles that protects friction couples from direct asperity contact and improves tribological behavior. Generally, a lubricating nano-grease containing 1 wt% CaCO3 can be utilized in industrial valves as the best lubricating nano-grease.