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The influences of Hexagonal boron nitride (hBN) and Calcium carbonate (CaCO3) nanoparticles on tribological and bearing vibration properties of polyurea grease (PG) were investigated. The microstructure, friction coefficient, wear morphology, and bearing vibration test of five components of greases were conducted. The results showed that the addition of 1 wt% hBN, playing the role of isolation protection and nano-abrasive, could improve the wear and vibration reduction performance of PG. However, the addition of CaCO3 nanoparticles at the same time, playing the role of deposition and recovery, could further improve the tribological and vibration reduction performance of PG, which was attributed to the synergistic effect of CaCO3 and hBN particles. The findings revealed that PG with the addition of 1 wt% hBN + 5 wt% CaCO3 nanoparticles had the greatest tribological and vibration suppression performance, which is due to the synergistic effect of hBN and CaCO3 nanoparticles. Additionally, the wettability tests showed that the addition of hBN and CaCO3 nanoparticles could significantly increase the flow of base oil on the PG soap fibers, resulting in the most effective bearing vibration suppression. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnO@SiO 2 have better dispersion in lubricants than ZnO/SiO2 mixed nanoparticles. • ZnO@SiO 2 composite nanoparticles can form a stable tribo-film on the worn surface. • SiO 2 shell absorb long chain molecule of base oil, forming a high viscosity layer. Nano additives have been widely proven to significantly improve the tribological properties of traditional greases, and the synergistic effect of multiple nanomaterials to improve the performance of greases is a promising research direction. In this paper, based on the hardness of the bearing material GCr15 steel, harder SiO 2 nanoparticles and softer ZnO nanoparticles were selected to synthesize hard-shelled soft-core composite nanoparticles (ZnO@SiO 2) by chemical deposition, and it was used as grease additive for the first time. The composite ZnO@SiO 2 nanoparticles have better dispersion and tribological properties than the physically mixed nanoparticles (ZnO/SiO 2). When 1 wt% ZnO@SiO 2 was added to the grease, the coefficient of friction and wear scar diameter were reduced by 11.5% and 25%, respectively. The special hard-shell-soft-core structure of the composite not only has good dispersion, but also forms a special solid friction film on the surface of the friction pairs. The SiO 2 shell can absorb a large number of long-chain lubricant molecules and increase the viscosity of the lubricant in the friction zone, thus forming a solid-liquid phase composite lubricating film, which plays a significant role in friction reduction and anti-wear. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of the tribological and vibration performance of the synthesized lithium complex grease (LCG) containing Carbon black, Fe 3 O 4 and Al 2 O 3 nanoparticles on rolling bearing. The micromorphology, friction coefficient, worn surface and bearing vibration experiment of four greases were studied. The results show that in presence of nanoparticles friction and wear behaviors are improved compared to LCG without nanoparticles. The best tribological performance is obtained in presence of Al 2 O 3 nanoparticle, which is mainly attributed to its high hardness, cylindrical shape and deposition on the worn surface. Further, the wettability test shows that Al 2 O 3 nanoparticles can effectively promote the flow of base oil on the LCG soap fibers, which results in the most effective bearing vibration suppression. • The Al 2 O 3 nano-particles have the largest hardness and show cylindrical microscopic morphology. • The Al 2 O 3 nano-particles were intensively deposited on the surface of worn steel ball. • The Al 2 O 3 nanoparticles effectively promote the flow of base oil on the LCG soap fibers. [ABSTRACT FROM AUTHOR]

To evaluate the effects of CuO nanoparticles on friction and vibration behaviors of grease on rolling bearing, lithium complex grease (LCG), polyurea grease (PG), calcium sulfonate complex grease (CSCG) and these three greases containing 1 wt% CuO nanoparticles were prepared respectively. The microstructure, friction coefficient, wear surface and bearing vibration test of six greases were investigated in detail. The results show tribological properties of PG are improved most significantly, with the friction coefficient and wear scar diameter decrease, and the wear surface is fine and smooth. This is mainly attributed to the synergistic effect of lamellar thickener structure and CuO nanoparticles. Further, the addition of CuO nanoparticles to PG also has an obvious inhibitory effect on bearing vibration. • The three thickeners show coiled fibrous, lamellar and reticular microstructure. • The CuO nanoparticles have different effects on friction of the three greases. • The CuO nanoparticles affect the vibration of bearing with three greases. [ABSTRACT FROM AUTHOR]