The Effect And Mechanism Of The Cermet Additive In Lubricating Oil On Contact Fatigue And Sliding Wear Performance Of Steel/Steel Friction Pair

Lubricating technology is an effective solution to avoid the wear of materials. And the lubricating oil additives play an important role in the lubricating system. Study on the self-repairing lubricating additives will make a completely new complement and extending of the traditional triboiogical theory and greatly contribute economic and social benefits to the industrial fields, like cars, machinery and national defence. Therefore, it is very valuable and necessary to carry out the researches about the influences of self-repairing additives in lubricating oil on the triboiogical performance of metal friction-pairs.A self-repairing cermet additive in lubricating oil, whose main content is Al₄ [Si₄O₁₀] (OH) 8, was selected as the main composition. The ball-on-rod contact fatigue tester, friction and wear testing machine and whole experiments were carefully designed according to the research requirements. The effect of cermet additive on contact fatigue life and fatigue wear performance of steel/steel friction pair was investigated. In the friction and wear tests, the steel / steel friction pairs, and two kinds of contact modes of them, namely, ball-on-disc and pin-on-disc, were adopted to be the research targets. The influences of different working parameters, like load, rotating speed, sliding distance and additive concentration were studied. Also the analyses of machine parts, like gear, nitriding cylinder and chromeplating cylinder liners treated by the cermet additives were combined with the lab tests to systematically study its function and mechanism.It was found that the effect of cermet additive on the steel / steel friction pair is very obvious, it can effectively improve the contact fatigue life and show a good self-repairing function. And the load, sliding distance and additive concentration all influence the additive effect obviously, while the effect of rotating speed is less. It was found also that the additive can improve the surface topography in different degrees,lower the surface roughness significantly, repair and cover some cracks, enhance the nano-hardness of most frictional surfaces, and change the surface structure into a carbon-rich layer and DLC structure.Based on the systematic research, it was considered that the cermet additive can greatly improve the tribological performances of the metal friction pairs and show obvious self-repairing effect in certain working conditions, and the main function can be composed of several stages as follows: 1. surface polishing and speeding up running-in period, 2. energy accumulation and displaying anti-wear effect, 3. activating wear debris and broken carbon chains, and wear debris returning to the frictional surface, 4. formation of the surface modified layer with DLC structure. These stages repeat all the time until the complete cermet repaired layer is formed. And the cermet additive plays only an important catalysis role, instead of being a content of the repaired layer composition like most other additives.