Research On Application And Mechanism Of New-type Cermet Additive In Lubricating Oil

As a kind of new lubricating oil additive, the cermet additive owns obvious anti-friction and self-repairing function. For the additive, whose main composition is Al4[Si4O10](OH)8, a systematical study on the tribological behaviors of steel/steel and steel/cast iron rubbing pairs were carried out on the sliding friction and wear tester made by ourselves, such as the influence of load, speed and material of the friction pair on self-repairing and tribological properties; analyses and verification of the oil samples from the tester and practical engine by ferrographic and spectroscopic method; analyses of composition and structure by the modern micro analysis instruments, like Micro-hardness tester, nano-hardness tester, AFM, SEM, XPS,XRD, Raman and SAM. The function mechanism of the new cermet additive was also discussed. According to the special requirements of research, such as wide range of load and speed, long-time running, and flat-surface wear track required, the multi-functional GWL-1000 friction and wear tester was researched and developed at first. On the tester the ball-on-disc and pin-on-disc tests were both carried out, to evaluate the tribology performance and self-repairing function of the additive. It was found that the running-in period of the friction pair could be reduced , the steady-wear period could be started earlier and the effects of the additive were more obvious with the increase of load and speed; the additive showed better function on the steel/cast iron friction pair than on steel/steel pair, which may be caused by the high carbon content and its unique structures; and that the additive could show excellent long-time dynamic self-repairing function to extend the wear life of the material. It was also found in the ferrographic analysis that the severity of wear index and wear particle concentration decreased when the additive was added. Moreover, the ferrographic analysis result for the practical engine was in good agreement with that for the tester, which displayed that the practical condition is better for the additive to play its roles in lubricating oil. It was found that the structures and properties of the formed cermet layer on the wear surface had changed greatly, the nano-hardness reached more than 16Gpa, surface roughness Ra decreased to 20-30nm, carbon content increased greatly, amorphous-state DLC structure was proved by the Raman analysis. Based on the tests and analysis results, the mechanism of the additive was put forward and a physical model was proposed: in the friction process, the additive may greatly enhance the activity of the friction surface, adsorb the carbon atoms dissolved from the lubricating oil, capture and cover the iron wear debris, and then a new structure can be reformed on the friction surface, which is likely to be the DLC structure.