Research On Tribological Properties Of Novel Copper/Graphene Slip Ring With Electric Current

Conductive slip ring,which is the critical component of various precise rotary tables,centrifuges and inertial navigation equipments,tends to be worn severely during sliding.So,it is urgent to develop materials with high conductivity and high wear-resistance.Copper has excellent conductivity and ductility,and graphene has properties of remarkable strength,high conductivity and superlubricity.This paper plans to combine the merits of copper and graphene and prepare bulk composite synthesized by copper and graphene with properties of high conductivity and wear-resistance.In this paper,modified Hummer's method was employed to prepare graphene oxide.Copper nanoparticles were coated uniformly on graphene.Then copper/graphene bulk composites were prepared by powder metallurgy molding.The density,hardness and resistivity of the bulk composite were tested.Friction pair formed by copper/graphene bulk composite and H65 hard brass was adopted to study the friction and wear properties of the bulk composite on a specially designed simulating test rig.The effect of graphene content,current and load on the friction and wear properties was explored.The wear topography was observed by scanning electron microscope(SEM).The wear mechanism was discussed.The results are shown as follows:1.The size of copper/graphene composite particle prepared through electroless plating is between 100-300 nm.After sensitization and activation of graphene oxide,copper particles are able to distribute evenly on the surface of graphene and thus enhance the interfacial bonding strength between copper and graphene.2.The copper/graphene bulk composites with different graphene oxide contents are prepared by powder metallurgy process.With the increase of graphene oxide content,the density and electrical resistivity of the copper/graphene bulk composites increases accordingly,but the hardness increases at first and then decreases.The hardness of the bulk composites reaches a maximum(201.9 HV)when graphene oxide content is 1.5wt%,which is 3.5 times harder than pure copper.3.The friction coefficient of the copper/graphene bulk composites decrease with the increase of the graphene oxide contents,and the wear rate increases at first and then decreases.Meanwhile,the friction coefficient and wear rate are obviously lower than pure copper.It can be concluded that the addition of graphene into composites can decrease the friction coefficient and improve the abrasive resistance.4.The friction coefficient of copper/graphene bulk composites decreases with the load until a plateau value reaches,and the friction coefficient decreases gradually with the increase of the electric current.However,the wear rate experiences first increase and then decrease,eventually increases with the load.Meanwhile,the wear rate increases gradually with the electric current.5.The worn mechanism of copper/graphene bulk composites under the condition of current-carrying is mainly attributed to the coupled composite worn mechanism of physical deterioration and electrical wear.The graphene solid lubrication films formed on friction surface have excellent effects of decreasing friction and reducing adhesive wear and electrical wear.