The Research On Tribological Properties Of Solid-Liquid Composite System Based On Ti-DLC Film

Solid-liquid composite lubrication is an important technology to improve the lubrication effect and the friction and wear under extreme conditions by using the synergistic effect between solid and liquid lubricants material.Diamond-like carbon?DLC?films have been considered to be a promising competitor of solid lubricating films because of high hardness,low friction coefficient,outstanding wear resistance and chemical stability etc.However,it has been found that DLC films are difficult to react with ordinary additives due to low surface energy and chemical inertness.Metal doping can improve surface energy of DLC films,making additives more easily adsorbed on the surface of friction pairs.The design of traditional additives was applied to the interaction of metal friction pairs,which is not compatible with the DLC film,and most of them are polluted by sulfur and phosphorus compounds.Therefore,there is an urgent desire to develop environment-friendly lubricant additives for DLC film solid-liquid composite lubrication systems.In this paper,Ti-DLC films were deposited on the surface of high-speed steel by magnetron sputtering technology,alkylated graphene oxide,carbon nitride,and graphene oxide/carbon nitride nanocomposites were used as lubricant additives.The tribological behavior and synergistic lubrication mechanism of Ti-DLC films and lubricant additives were discussed.The main research contents and conclusions are as follows:?1?The alkylated graphene oxide?GO-ODA?was successfully prepared by chemical grafting.The oxygen functional group of the graphene oxide base surface and the amino group of octadecylamine?ODA?formed a long alkyl group by covalent interaction Chain,which promotes its stable dispersion in PAO-6 base oil.As a base oil additive,GO-ODA nanosheets not only have a very low coefficient of friction under high contact pressure,but also greatly improve the anti-wear performance,while also protecting the Ti-DLC film from damage.Shows the good synergistic lubrication effect of GO-ODA and Ti-DLC.2)The urea calcined in a muffle furnace to obtain a light yellow carbon nitride?g-C₃N₄?nanosheet sample.The g-C₃N₄ nanosheets with different concentrations were used as base oil additives under three loads?50 N,100 N,and 200 N?,to study the effect of different concentrations of g-C3N4 nanosheets as base oil additives under three loads on the tribological properties of Ti-DLC/GCr15 system.The friction coefficient and wear rate of the system are significantly reduced,and as the load increases,the friction and wear does not increase significantly,indicating that g-C₃N₄ nanosheet load adaptation range wider.As a new environmentally friendly lubricating oil additive,g-C₃N₄ shows great potential for its future applications in lubricating friction.?3?A graphene oxide/carbon nitride?GO/g-C₃N₄?nanocomposite was synthesized by self-assembly method,and octadecylamine was successfully grafted onto the surface of the nanocomposite by chemical grafting.When the two-dimensional nanocomposite was used as an additive,it exhibits superior lubricating properties compared to single graphene oxide and carbon nitride.The lipophilic nanocomposite adsorbed oil molecules on the surface form a microscopic two-dimensional layered heterogeneous structure by self-assembles that further reduces the shear strength,which results in low friction behavior of the Ti-DLC film solid-liquid composite lubrication system.The synergy between GO and g-C₃N₄ promote to form a thicker lubricating protective film,which effectively reduces the friction coefficient and wear rate of the system.