Experimental Study On Tribological Performance Of Lithium Grease Containing Various Nano-particles As Additives

It has been widely applied in lubrication engineering for quite a long time that addingadditives into lithium grease to reduce friction and wear and even to mend the wear surface.friction reduction,surface improvement and extreme-pressure effect of five kinds of singlematerial nano-partictes and groups of mixed material nano-particles as lithium greaseadditives are tested, and a preliminary exploration of the mechanisms are presented.Tribological performances of the nano-alumina (Al₂O₃), aluminium(Al), cuprum(Cu),magnesia (MgO), zinc oxide(ZnO) particles as additive in lithium grease were studied byfriction and wear tester. It was found that every kinds of single material nano-particles couldimprove friction reduction,reconditioned the surface and exhibit extreme-pressure effect ofsurfaces by observing and analyzing the wear surfaces by using SEM and EDS. Themechanism was put forward that soft metal nano-particles Al and Cu can form the film thatshear easily between the interface which can protect the surface of friction and do well infriction reduction in the contact zone. Furthermore, nano-particles might melt and weld in thefriction surface due to friction heat accordingly, both of them reveal a better improvement ofthe surface. Nano-particles Al₂O₃ take on a high rigidity and melting point, so thenano-particles were supposed to roll like a ball between the contacting area, and changessliding friction to rolling friction, which lead to the reduction of friction and enhancement ofload carrying capacity simultaneously. The nano-particles can fill or embed in the grooves onthe surface which can do well in the surface improvement. Nano-particles MgO and ZnO canform a kind of film that unsteadily and destroy easily between the interface, so both ofnano-particles also improve friction reduction, surface quality and extreme-pressure effect ofsurfaces, but the effect is not much obvious.On the basis of some characteristic parameter obtaining from the tribological tests of fivekinds of single material nano-particles, and considering economy of this test, the author usedfriction and wear tester to study of the mixed nano-Al₂O₃, Al, Cu and nano-Al₂O₃, Al, MgOparticles as additive in lithium grease and find that the mixed nano-particles possess bettereffects of friction reduction,s urface improvement and extreme-pressure. Through this test wefound the best confecting method of the mixed nano-Al₂O₃, Al,Cu and nano-Al₂O₃, Al, MgOparticles. The result indicated that several kinds of particles can put up respectivecharacteristics because of synergetic effect of mixed nano-particles, so the mixed particles asadditive could improve the tribological property of lithium grease more obviously. Meanwhilewe can not neglect nano-Cu and nano-MgO particles' effect, although there are a smallproportions in the mixed particles. Abundant tribological properties were studied in this paper, and developed a new typenanometer lithium grease additive that have outstanding properties of friction reduction,extreme,pressure mechanism and a certain surface improvement mechanism. It possessbroadly market's requirements.