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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]

Grease plays an important role in reducing friction and wear of rolling bearings and improving their service life and reliability. However, increasing attention is being paid to the environmental pollution caused by discarded grease. In this paper, calcium sulfonate complex grease (CSCG) was prepared by using green raw materials, namely poly-alpha-olefin oil as the base oil and complex calcium sulfonate soap as thickener. In order to improve the lubrication and damping performance of the grease, hexagonal boron nitride (hBN) and nano-Al 2 O 3 , which have the potential to replace toxic additives, are mixed into the grease in different mass proportions. The thickener structure of each grease was characterized and analyzed. According to the bearing vibration and life of the two key performance indicators, four-ball tests and bearing vibration tests under limited lubricant supply (LLS) were performed. The results show that CSCG with 0.75 wt% hBN and 0.25 wt% Al 2 O 3 (BN75AL25) has the best tribological and vibration suppression performance. The mean friction coefficient decreased by 11.3%, the wear scar diameter decreased by 6.1%, and the worn surface morphology improved significantly compared with CSCG. The frequency domain analysis showed that high, medium and low frequency vibrations were suppressed by 19%, 11.7% and 16.4%, respectively. In conclusion, BN75AL25 has the potential to become a green high-performance grease under LLS, which is worth further research and exploration. [Display omitted] • The nano-hBN can promote the formation of calcium carbonate protective layer. • The nano-Al 2 O 3 can improve the tribological performance of the grease with hBN. • The nano-hBN and nano-Al 2 O 3 can reduce the vibration by momentum exchange. [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]