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Molybdenum disulfide nanoparticles is an effective additive used to enhance the tribological properties of greases. However, there are four main mechanisms for improving the tribological properties of nanoparticles. Nano-MoS2 mainly plays the role of film formation, but it is difficult to achieve rolling, mending, and polishing effect. In this paper, based on addition of MoS2 nanoparticles, CuO, SiO2, and Al2O3 nanoparticles are further added to calcium sulfonate complex grease to achieve the other three effects, hoping to further improve the tribological performance of the grease. The tribological properties and the suppression effect on bearing vibration of the five greases were studied by four-ball friction experiment and bearing vibration experiment. The results show that a protective film consisting of MoS2 and MoO3 is formed on the worn surface. The addition of three oxide nanoparticles can further improve the properties of the calcium sulfonate complex grease containing MoS2 nanoparticles. Among them, calcium sulfonate complex grease with MoS2 and SiO2 nanoparticles performs the best, with 11.9% decrease in friction coefficient, 5.9% reduce in wear scar diameter, 27% decrease in the high frequency vibration of the bearing. The wettability test shows that the contact Angle of polyα-olefin 40 base oil on the thickening agent surface of calcium sulfonate complex grease containing MoS2 and SiO2 nanoparticles is the smallest, and it can be quickly added to the raceway. [ABSTRACT FROM AUTHOR]

Si 3 N 4 hybrid bearings are considered the most promising motor bearings due to their characteristics of electrical insulation, high speed, low friction coefficient, and wear resistance, which can better meet the requirements of driving motors of electric vehicles. However, the tribological mechanism between the ceramic-grease-steel complex interface is unclear. Three kinds of greases, namely lithium, polyurea, and calcium sulfonate complex grease, were synthesized from poly alpha olefin 40 as base oil. The effects of grease thickener morphology on the tribological properties of Si 3 N 4 /GCr15 contact surfaces at different slip speeds were investigated, and the vibration and friction torque performances in 6204 hybrid ceramic balls were evaluated. The results showed that the thickener could form physical deposition film and friction film to protect the worn surface at low speed. The friction and wear conditions were significantly improved at high speed under lithium grease and polyurea grease lubrication, being a mixed lubrication state. In presence of lithium grease, the tribological performance of the Si 3 N 4 /GCr15 interface and the vibration performance, impacted condition, starting torque, and friction torque of the hybrid ceramic ball bearings were all the best. Because lithium grease is subjected to continuous shear of the ceramic ball, which releases the base oil stably, and forms a thick oil film with the broken thickener in the center of the raceway, the bearing is in a mild lubrication state. Therefore, for Si 3 N 4 hybrid ceramic ball bearings, lithium grease is a lubricant with good application prospects. [ABSTRACT FROM AUTHOR]

Six kinds of choline chloride (ChCl)/diols deep eutectic solvents (DESs) with different alkyl chain lengths and hydroxyl positions were prepared, which are easily synthesized and biodegradable. Tribological and bearing tests show that ChCl/ethylene glycol (EG) has the best performance on the surface of Si 3 N 4 /GCr15 tribo-pairs. Compared with PAO10, friction coefficient, wear scar diameter, bearing vibration, and friction torque decreased by 71 %, 28 %, 34.8 %, and 24.6 %, respectively. ChCl/EG, which has the shortest alkyl chain length and hydroxyl distance, has the highest molecular polarity. Such a dense and stable chemisorption film is formed and the lubrication performance is improved, which is confirmed by the inconspicuous tribochemical films. Consequently, ChCl/EG serves as a potentially superior lubricant for Si 3 N 4 hybrid ceramic ball bearings. • The shorter the alkyl chain of the diol DES, the better the tribological effect. • The longer the hydroxyl group distance of the diol DES, the better the tribological effect. • ChCl/EG exhibits excellent tribological properties. [ABSTRACT FROM AUTHOR]

The surface microstructure of biomimetic Procambarus clarkia claw was prepared on the surface of GCr15 steel, then PTFE solid lubricants dispersed with three different hardness nanoparticles (C, ZnO, Al 2 O 3) were filled in. The results of the tribological experiment show the textured surface lubricated by PTFE with Al 2 O 3 nanoparticles reflected the best performances. Because PTFE stored by the bionic texture could be supplied to the friction surface to form a solid lubrication film. Due to the addition of Al 2 O 3 nanoparticles, the hardness and wear resistance of the film are improved, thus avoiding a large loss of PTFE. And the process of "rolling-embedding PTFE surface-exposing-rolling" occurs. As a final, the surface tribological properties of GCr15 steel can be significantly improved. • The PTFE could be supplied to the friction surface to form a solid lubrication film. • The Al 2 O 3 nano-particles enhance hardness and wear resistance of lubricant film. • The textured surface lubricated by PTFE with Al 2 O 3 reflected the best performance. [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]

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]

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]