Mechanism Of Tribofilm Formation Of Graphene-serpentine Additive And Its Friction And Wear Properties

The addition of anti-wear and friction-reducing additives to lubricants is a common means to improve the wear-resisting property of parts.In recent years,metal self-repairing additives have been paid more and more attention because they can repair the damage of surface to make the artifact reach zero or even negative wear situation.Generally speaking,metal self-repairing additives mainly refer to silicate,among which,natural minerals such as serpentine powder are widely used.At present,there are lots of experimental data and a variety of self-repairing theories got from many researches on serpentine and composite additives of serpentine.These researches show that the tribo-healing film of serpentine contains a lot of amorphous graphite,SiO2,FeS and other complex chemical compositions.The most important discovery from these researches is that graphite comes from the cracking of lubricants and that the graphite plays an important role in the formation of tribo-healing film.However,there are still many deficiencies in the current researches,and the mechanism of film formation is also diversified.In this paper,there establishes the model of lubrication and repair of composite additives and the paper demonstrates that serpentine is attached to the surface and interlayer of the graphene layer and that the serpentine plays a role in lubrication and repair with the graphene.Since the addition of sulfonated graphene eliminates the cracking of lubricants,sulfonated graphene directly participates in the formation of the repairing film.Sulfonated graphene instead of graphite deposits in wear areas and absorbs cerment particles such as SiO2 from serpentine,Fe S and Fe2O3 which are both got from the reaction of serpentine and matrix,and then forms the repairing film with the cerment particles.The experiment discovers that the formation speed of repairing film of the composite additive of graphene-serpentine is faster than other composite additives and that sulphur which is a particular element in sulfonated grapheme exists in the repairing film,demonstrating that sulfonated graphene can boost the formation of repairing film.The friction and wear experiment is done through the preparation of oleophilic sulfonated graphene(SGO)and the addition of synthetic lubricants to the oleophilic SGO,using X-ray diffractometer(XRD)and scanning electron microscope(SEM)in order to characterize the sulfonated graphene.And the experiment also studies the anti-wear and anti-friction properties of the sulfonated graphene and the film formation property of the sulfonated graphene on metal surface.The film of graphene on metal surface can isolate air and water molecules,thus it can prevent the corrosion of metals.The salt spray corrosion test machine verifies that the film of graphene can prevent the mental surface from corrosion,in addition,the experiment on the machine finds the method of the preparation of sulfonated graphene lubricant preparation method and analyzes the self-repairing property of sulfonated grapheme,believing that the sulfonated grapheme can be used as a kind of new self-repairing additives.The paper studies the composite film of sulfonated graphene(SGO)and serpentine,rather than the composite film of nano-graphite particles and serpentine and employs various means to analyze the composition and structure of the tribo-healing film on the metal surface and the way of lubrication and the mechanism of film formation of compound additives,then the paper shows a fact that the composite film of sulfonated graphene(SGO)and serpentine can deepen the mechanism of film formation of mental self-repairing addictives.Based on the fact,the paper makes distinction between the mechanism of film formation of composite additives and the mechanism of film formation of the serpentine additives.Firstly,through the four-ball friction and wear test machine,the paper studies the anti-wear and anti-friction property of sulfonated graphene(SGO),serpentine,and composite powder on different concentrations.Then,the paper analyzes and studies the formation of the self-repairing film on the mental surface through the macroscopic and microscopic detection of surfaces of friction pairs.Later,through using scanning electron microscope(SEM)to observe the microstructure of self-repairing film on metal surface,using the ultra depth of field microscope to observe the size and three-dimensional shape of grinding marks and employing the energy dispersive system(EDS)to examine the compositions of self-repairing film,the paper reveals that the way of film formation of composite lubricant additives is different from that of the traditional additives and explores the effect of load,rotational speed and temperature etc.,providing a new idea for the development of composite additives.