Tribology Study Of Surface Modified Nano-rare Earth Oxides

With the constant updating of the machinery, equipment and performance, and theincreasingly demanding environmental requirements, the low-sulfur and phosphate-free andefficient multi-purpose lubricant additives were needed by multiple lubrication systems. In thesame time, the fuel oils were developing to low-sulfur and low-olefin direction, the catalyticconverters were required to install by gasoline vehicles, and the diesel cars should increasethe exhaust gas recirculation system, so it requires the lubricants with low sulfur and lowphosphorus. So, it has very important significance to study of the low-sulfur, low-phosphorus,even phosphorus-free, lubricant oil additives. The rare earth compound has excellent chemicalstability and excellent lubricating properties, and the special structure of the4f electron shellof the rare earth relate to its lubrication.For the high diffusivity, large surface area, low melting, easy sintering propertieshardness and other characteristics of the nano-materials, so it is easy to form a layer of easyshearing lubricating film on the friction surface to reduce the coefficient of fiction, while itcan fill and repair the worn surfaces. Between the fiction surfaces, the approximatelyspherical nanoparticles play the role of micro-bearings, so it can make the fiction surfacespolished and strengthening and supporting the load, increasing carrying capacity, andreducing the fiction coefficient at the same time. The analysis shows that the excellentabrasion resistance and outstanding resistance to extreme pressure properties of the nanoadditives make it suitable for low-speed, heavy-duty, high-temperature environment. Differentfrom the general solid lubricating materials, the nanoparticles have the advantages both of thesolid and the fluid lubrication. The rare earth element additives can improve the wearresistance of metals and alloys, and for the high temperature lubrication characteristics ofsome rare-earth compounds, it can improve the friction properties of the solid lubricant film,alloy and ceramic coatings in the friction process.The nitrogenous compounds were used as the surface modifier to modify the nano-rareearth oxides particles synthesized by sol-gel method. Some analytical tools were used tocharacterize the structure and properties of surface-modified nano-rare earth oxides particles.The abrasion resistance was tested by MRS-10A four-ball taster. After the tests, observing theunder ball of the four-ball taster by the JSM-500LV scanning electron microscope （SEM） toanalysis the test balls’wear scar morphology and the elements on the worn surface.The main conclusions derived from experiments as follows:（1） The nano-CeO₂particles that modified by the benzotriazole acetic acid had a gooddecentralize in rapeseed oil and they could enhance abrasion resistance of lubricating oil; wear scar diameter reaches a minimum （0.463mm） when the additive content of0.3wt%, thesmallest wear scar diameter is reduced by16.9%;（2） The tribological properties of CC grade wood oil with nano-La₂O₃, surface modifiednano-La₂O₃, nano-CeO₂, surface modified nano-CeO₂was better than the CD grade wood oil,wear scar diameter reaches a minimum （0.463mm） when the additive content of0.3wt%, thesmallest wear scar diameter is reduced by16.9%; In order to improve the performance of thefriction surface antifriction, the nanoparticles reacted with the friction pair generating alloy inthe test process.（3） In the effective load range, the carrying capacity of3#general lithium grease can beincreased by the additives of nano-La₂O₃, surface modified nano-La₂O₃, nano-CeO₂, surfacemodified nano-CeO₂. The PBvalue reaches a maxmum （863N） when the additive content of0.7wt%, increased by57.2%; When the level of additives was moderate, they could play itsresistance to wear better. Under certain conditions, the additives nano-La₂O₃and surfacemodified nano-CeO₂could increase the friction coefficient of the3#general lithium grease.