KH550修饰纳米莫来石对聚脲润滑脂摩擦学性能的影响

Effect of KH550 Modified Nano-mullite on Tribological Properties of Polyurea Grease

目的研究硅烷偶联剂表面修饰纳米莫来石(Mullite)(Al_(2)O_(3)-SiO_(2)体系)作为添加剂,对聚脲润滑脂摩擦学性能的影响。方法用硅烷偶联剂(KH550)对纳米Mullite表面进行修饰,分别制备质量分数为0.03%的纳米Mullite和KH-mullite的聚脲润滑脂。采用四球摩擦试验机测试纳米Mullite和KH-mullite作为添加剂对聚脲润滑脂摩擦学性能的影响,利用扫描电子显微镜(SEM)和三维表面形貌仪观察磨损表面形貌,通过X射线能量色散能谱仪(EDS)分析磨损表面的元素分布,使用X射线光电子能谱(XPS)分析磨损表面润滑膜的元素价态,探究添加剂在聚脲润滑脂中的作用机理。结果经过修饰后,纳米KH-mullite在聚脲润滑脂中的减摩抗磨性能较优,摩擦因数和磨斑直径分别降低了22.4%、15.6%。通过SEM和三维表面轮廓仪观察磨损表面发现,KH-mullite添加剂能够有效降低磨损表面的粗糙度,修复磨损表面。KH-mullite聚脲润滑脂优良的摩擦学性能归功于两点,首先KH-mullite能够沉积并吸附在磨损表面,在起到修复作用的同时促进了润滑膜的形成;其次,KH-mullite能够进入润滑膜中,将摩擦副之间的摩擦方式变为滚动摩擦。结论Mullite和KH-mullite都具有提升聚脲润滑脂润滑性能的作用,经硅烷偶联剂修饰后的KH-mullite在减摩抗磨性能方面表现更优越。

As a traditional lubricant medium,lubricating grease effectively reduces the friction and wear of mechanical equipment during operation.Polyurea lubricating grease is highly favored due to its good thermal stability,oxidative stability,and corrosion resistance.With the rapid development of modern industries,people's requirements for the performance of lubricating grease are becoming increasingly demanding.Adding nanoparticles to lubricating grease is a feasible solution to improve its lubricating performance.However,nano oxides tend to agglomerate due to their small volume and large specific surface area.The currently used method is to modify the surface of nanoparticles to improve their dispersibility.Therefore,this study chose to investigate the effect of KH550-modified mullite(Al2O_(3)-SiO_(2) system)on the frictional properties of polyurea lubricating grease.In this study,the silica coupling agent(KH550)was used to modify the surface of nano-mullite,and polyurea lubricating grease containing 0.03%nano-mullite and KH-mullite were prepared,respectively.The frictional properties of polyurea lubricating grease with nano-mullite and KH-mullite as additives were evaluated with a four-ball friction tester(MRS-10D).GCr15 steel balls were used as the friction pairs in the test,and a composite grease with a mass of 10 g was used each time.The test duration was 60 minutes.The surface morphology of the worn surface was observed with a scanning electron microscope(SEM)and a three-dimensional surface profiler.Energy-dispersive X-ray spectroscopy(EDS)was used to analyze the element content of the worn surface and X-ray photoelectron spectroscopy(XPS)was used to analyze the valence states of the elements in the lubricating film on the worn surface to explore the mechanism of mullite and KH-mullite in polyurea lubricating grease.The results showed that mullite,as an additive,could effectively improve the frictional properties of polyurea lubricating grease.Compared with that before modification,the nano-KH-mullite after modification showed better anti-wear and friction-reducing properties in polyurea lubricating grease,with a decrease in friction coefficient and wear scar diameter of 22.4%and 15.6%,respectively.Observations were made on the worn surface using SEM and a 3D surface profilometer,and it was found that after the addition of molybdenum disulfide lubricant,there were few wide and deep furrows on the worn surface,indicating the presence of abrasive wear.In contrast,the wear surface lubricated with KH-mullite was smoother,and the surface roughness was improved,indicating the presence of polished wear.EDS analysis revealed that,compared with the worn surface lubricated with mullite,the worn surface lubricated with KH-mullite had an increased oxygen element content,indicating that KH-mullite could deposit a large amount on the frictional surface to provide a friction repair effect.XPS element analysis showed that KH-mullite had good compatibility with polyurea lubricating grease,and could carry the stress between the friction pairs in the lubricating film while moving along the surface,transforming the sliding friction into rolling friction and thereby improving the frictional performance of the polyurea lubricating grease.Therefore,it can be concluded that both mullite and KH-mullite can improve the lubricating performance of polyurea grease,but KH-mullite modified with silane coupling agent exhibits superior anti-friction and anti-wear properties.