| Micro/nanoparticles have a broad application prospect since they can significantly improve the lubrication state of friction pair,reduce the friction and wear as lubricating additives.But it is difficult to meet the needs of large-scale application due to the preparation method and the limited of technology and cost.Currently,more and more researchers have been devoted to researching about self-healing materials which can be applied to large scale with the advantages of comprehensive functions,low cost and no pollution.Recently,considerable attention was focused on the "friction improver" represented by natural serpentine minerals for the friction self-healing of the metal surface.Attapulgite as a kind of hydrated magnesium aluminum silicate usually presents in nature as one-dimensional nanostructured fibrillate mineral,which has similar chemical composition and crystal structure with serpentine minerals.So in this work we choose attapulgite as the research object and investigated its tribological properties and self-healing mechanism which is used as lubricating oil additive.In this work,the purified attapulgite were used as research object,the crystal structure,physical and chemical properties as well as the influence of the crystal structure and properties with different pretreatment processes were systematic analyzed by a multitude of test methods.In addition,the attapulgite was surface modified with silane coupling agent KH-550 then the modification effect and the mechanism were also discussed.The tribological properties of attapulgite as additives added to three typical lubricating oil were analyzed respectively,the microstructure,elemental distribution and the phase composition of worn surface morphology were characterized,and the mechanism of anti-friction and anti-wear performance had been carried on the preliminary discussion.Results indicated that the addition of attapulgite under three typical lubricating oil can reduce the friction coefficient and wear rate of the specimens effectively,which showed excellent anti-friction and anti-wear properties and the discontinuous self-healing film was formed on the worn surface.The influences of different environmental factors of friction(load,frequency and test temperature),pretreatment process parameters(heat treatment temperature,concentration of the acid treatment)on the tribological properties of attapulgite in the mode of line contact as additive in 150 SN mineral base oil were analyzed.Furthermore,the microstructure and elemental composition of wear surface morphology were analyzed.The addition of attapulgite under different environmental factors of friction showed excellent anti-friction and anti-wear property and the self-healing film was found on the worn surface.In addition,the addition of attapulgite under line contact mode showed good anti-friction and anti-wear properties as well,and self-healing film with the thickness about 3?m which is composed of nano-crystalline and amorphous was found on the surface of the wear.The tribological properties of organic molybdenum doped with attapulgite added to lubricating oil in were investigated,further the synergy between organic molybdenum and attapulgite under the conditions of different loads,different frequencies,different ways of contact friction pair were tested.The results demonstrated positive synergy between organic molybdenum and attapulgite under the condition of test parameters used,which showed better anti-friction and anti-wear performance than that of the attapulgite itself.The tribological properties of nanometer copper doped with attapulgite added to lubricating oil in were investigated,also the synergy between nanometer copper and attapulgite under the conditions of different ways of contact friction pair,different loads,different frequencies were tested.The results indicated that the composite of nanometer copper and attapulgite further improved the performance of anti-friction and anti-wear compared to attapulgite.The results give evidence that the addition of attapulgite to lubricating oil can reduce the friction coefficient and wear rate of the specimens effectively,which showed excellent anti-friction and anti-wear properties and the discontinuous self-healing film was formed on the worn surface.The composite of nanometer copper and attapulgite,organic molybdenum and attapulgite further improved the performance of anti-friction and anti-wear compared to attapulgite.Thus,attapulgite has great potential for application in the friction self-healing of the metal surface field as "friction improver".In this paper,the research showed that attapulgite is a high quality self-healing material and indicated the application in engineering scale in the future,which provides theoretical basis and engineering support. |
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