纳米二氧化铈添加剂对复合锂基润滑脂摩擦学性能影响研究

The Effect of Nano-CeO_(2) Additive on the Properties of Lithium Complex Grease

为进一步提高复合锂基润滑脂摩擦学性能,将不同质量分数的纳米氧化铈(nano-CeO_(2))粒子添加到复合锂基润滑脂中,并利用四球摩擦磨损试验机对所制备的复合锂基润滑脂摩擦学性能进行测试,分析摩擦系数变化趋势.利用扫描电镜(SEM)、倒置金相显微镜和三维表面形貌仪观察摩擦试验后钢球表面磨痕形貌变化,并测量磨斑直径大小,同时使用X射线光电子能谱(XPS)和能谱仪(EDS)对润滑脂以及钢球表面典型元素变化情况进行测试,分析纳米氧化铈对润滑脂摩擦学性能影响机理.结果表明:当润滑脂中添加的纳米氧化铈质量分数为0.8%时,表现出最佳的抗磨减摩性能,摩擦系数和磨斑直径相比原始润滑脂分别降低了22.5%和12.1%.三维形貌扫描发现钢球磨斑表面粗糙度相比原始润滑脂降低38.1%,平均磨斑高度与最大磨斑深度分别下降56.9%和51.3%,纳米氧化铈对磨损表面具有抛光和自修复作用.EDS和XPS的结果表明纳米氧化铈在钢球表面形成了1层润滑膜,减少了摩擦副之间的直接接触.

Nanoparticle additives have been extensively studied and shown to significantly enhance the tribological performance of lubricating greases.Rare earth nanoparticles exhibit superior performance compared to other types of nanoparticles.Compared with traditional additives,rare earth nanoparticles possess excellent extrusion,anti-wear,and environmentally friendly properties.In this research,to further improve the tribological performance of lithium complex grease,nano-CeO_(2) with different mass fractions were added to the lithium complex grease.The nano-crystalline morphology and structure of nano-CeO_(2) were characterized using X-ray diffractometer(XRD),Fourier transform infrared spectrometer(FT-IR),and scanning electron microscope(SEM).A four-ball friction and wear tester were used to test the tribological properties of the prepared nano-crystalline,and the friction coefficient was automatically evaluated by a computer connected to the test machine.The changes in the surface morphology and diameter of the worn spot on the steel ball after the friction experiment were observed using SEM,inverted metallographic microscope,and three-dimensional surface profilometer.Meanwhile,X-ray photoelectron spectroscopy(XPS)and energy dispersive spectroscopy(EDS)were used to test the typical element changes on the lubricating grease and steel ball surfaces,and to analyze the mechanism of nano-CeO_(2) on the tribological performance of the lubricating grease.The results showed that when the mass fraction of nano-CeO_(2) added to the lubricating grease was 0.8%,the best anti-wear and anti-friction performance was exhibited.The friction coefficient and worn spot diameter decreased by 22.5%and 12.1%,respectively,compared with the original lubricating grease.Analysis of the friction coefficient curve showed that nanoceria can significantly improve the friction stability of the lithium complex grease.SEM observations revealed that the addition of nano-CeO_(2) significantly improved the morphology of worn spots on the steel ball surface and reduced the formation of pits and scratches.Three-dimensional surface scans found that the roughness of the worn spot on the steel ball surface was reduced by 38.1%compared with the original lubricating grease,and the average and maximum depths of the worn spot decreased by 56.9%and 51.3%,respectively.Nano-CeO_(2) had a polishing and self-healing effect on the worn surface.At the same time,during the friction process,some nano-CeO_(2) particles were transferred to the steel ball surface,dispersing certain pressure stress.Testing the thermal conductivity of the lubricating grease revealed that the thermal conductivity of the lithium complex grease increased with the addition of nano-CeO_(2).The results of EDS and XPS showed that nano-CeO_(2) promoted the formation of other metal oxides on the steel ball surface,which formed a stable chemical film on the worn surface,reducing the direct contact between the friction pairs and further reducing the severe wear of the steel ball.