Study On Graphene Lubricant Additive And Its Tribological Properties On Internal Combustion Engine

In recent years,with the rapid development of anti-friction and anti-wear technology on internal combustion engine,nano-lubricating oil has come into being and developed a lot.The graphene is very suitable as a high-performance lubricating oil additive because of its thin nanostructure,high mechanical strength,thermal conductivity and self-lubricating properties,which has attracted more and more scholars' attention.But its poor stability in the lubricating oil dispersion and the lack of basic engine test,certainly restrict its promotion.The surface modification of nano-graphene was carried out by oleic acid,stearic acid,ricinoleic acid,silane coupling agent,titanate coupling agent.And the best modification scheme was screened by activation index method,natural sedimentation method and absorbance method.Meanwhile,we investigated the influence on physical and chemical properties of oil.We choosed the optimum additive amount by four-ball test and analyzed comprehensively the influence of graphene on the friction and wear resistance,high temperature detergency,the friction surface morphology,physical and chemical indicators by bench test.Results showed as follows:1?Optimum conditions of the modification of graphene is oleic acid and stearic acid with a mass ratio of 5:3 at 80 ?.The dispersion stability of modified graphene improved.The kinematic viscosity,the total acid / base value and the corrosiveness of lubricating oil containing modified graphene are equal to that of base oil,with less influence on the fluidity and corrosivity of lubricating oil.2?When 0.06 wt% modified graphene is added into the lubricating oil,its anti-friction and anti-friction properties increased.The friction coefficient is reduced to the lowest value of 0.077,30% lower than the base oil.Grinding diameter got to a minimum(0.42mm),with a decrease of 20.8%.Maximum no-clamping load was1.335 times then base oil.The amount of grooves on the surface significantly reduced and the depth decreased filled with black and gray fillers in some places.3?The oil consumption of the engine did not improve after test.The contents of Cu,Cr,Al and Pb in oil was less then base oil.The wear of the piston ring-cylinder pair was generally low.High temperature detergency got worse slightly.The surface roughness of main friction pairs is significantly smaller,and the surface hardness lower.Kinematic viscosity,TAN and TBN are basically the same.The content of n-pentane insoluble in the lubricating oil containing graphene was slightly lower.