几种纳米微粒作为锂基脂添加剂对钢-钢摩擦副摩擦磨损性能的影响研究

采用四球摩擦磨损试验机考察了纳米SiO2、纳米LaF3及纳米Ni等3类纳米微粒作为锂基脂添加剂对钢-钢摩擦副摩擦磨损性能的影响;采用扫描电子显微镜、X射线能量色散谱仪及X射线光电子能谱仪分析了含纳米微粒添加剂的锂基脂润滑下的钢球磨损表面形貌、元素面分布及典型元素的化学状态.结果表明:3种纳米微粒作为添加剂均能够显著提高锂基脂的减摩抗磨能力;锂基脂及含不同纳米添加剂的锂基脂润滑下的钢球磨损表面形貌及其表面保护膜的性质存在明显差异,这种差异决定了钢-钢摩擦副在相应脂润滑条件下的摩擦磨损性能差异;含纳米SiO2的锂基脂润滑下的钢球磨损表面形成的含纳米SiO2的表面保护膜均匀且厚度适中,故其相应的减摩抗磨效果最佳.

Tribological Properties of a Steel-Steel Pair under the Lubrication of Lithium Grease Containing Various Nano-Particulates as Additives

A four-ball machine was performed to investigate the effect of three kinds of nanoparticles as additives of a commercial lithium grease on the friction and wear behavior of SAE-52100 steel. Thus the friction and wear behavior of the steel-on-steel system under the lubrication of the lithium grease containing nano-particulates of Ni, or LaF_3, or SiO_2 was evaluated. The chemical states of some typical elements on the worn surfaces of the upper steel ball were analyzed by means of X-ray photoelectron spectroscopy, while the morphologies and elemental plane distributions of the worn surfaces of the lower steel balls were observed and determined by means of scanning electron microscopy and energy dispersion spectrometry. It was found that the three kinds of nano-particulates were all effective to improving the friction-reducing and antiwear abilities of the lithium grease, which was attributed to the formation of the boundary lubricating and protective layers on the worn steel surfaces lubricated with the base grease containing different kinds of nano-particales, by way of physico-chemical adsorption and/or tribochemical reactions. The best friction-reducing and antiwear behavior was observed for the lithium grease containing SiO_2 nano-particulates, because in this case the surface protective layer had a reasonable thickness and good uniformity. The worn steel surface was characterized by mild adhesion and scuffing under the lubrication of lithium grease and lithium grease containing various nano-particulates additives, and the adhesion and scuffing were effectively abated in the later cases, which conformed well with the corresponding friction and wear behaviors of the steel-on-steel system under different lubricating conditions.