Study On The Conductive Capacity And Electrotribological Performance Of The Ag Coating Under Boundary Lubrication

Sliding electrical contact is widely used in automation control,power electronics,aerospace and other fields.As the hub of power transmission,its performance determines the reliability,stability,accuracy and service life of the whole system.The design of the sliding electrical contact is challenging due to the collaborative damage of current erosion,mechanical wear and electrochemical corrosion.In order to realize the design of simple electrical contact possessing strong conductive ability,strong oxidizing ability and long service life,the Ag coating prepared by different techniques was used as the contact pair and the conductive grease as the lubricant in this paper.The conductivity and the electrotribological properties of the contact pairs under boundary regime was studied.Fine Ag,Ag-graphite(Ag/C)composite coatings and heat-treated Ag coatings were prepared by electrodeposition.The microstructure and composition of different coatings were characterized by XRD,SEM and EDS.The conductive polyaniline(PANI)was used as the versatile additives and lithium complex grease as base grease to prepare new conductive grease.The three kinds of coatings were tested in dry friction and boundary lubrication by using current-carrying friction and wear tester.As a result,the Ag coating has excellent electrical conductivity and tribological properties under boundary lubrication;The lowest mean COF(0.056)of Ag coating under boundary lubrication,which is about 50%that of Ag/C and 75.0%that of Cu,and the wear width of Ag significantly reduces(wear width:0.34mm,about 61%that of Cu and Ag/C).Its excellent electrotribological properties are mainly ascribed to the mechanical effect of micro PANI and the protective film generated by PANI grease.An Ag coating(MS-Ag)was prepared by DC magnetron sputtering.Compared with the electrodeposited Ag and Ag/C coatings,the MS-Ag coating was free of "Tip effect",and the structure is more fine and dense.A new type of high-temperature conductive grease was prepared by using PANI as additive and high temperature polyurea grease as base grease.The wear width of magnetron sputtered Ag is also smallest(wear width:0.368 mm,about 61.8%that of Ag and 71.6%that of Ag/C).For the boundary lubrication,the current not only can play the anti-friction effect,but also play a certain anti-wear effect,which is mainly due to the synergy of the protective tribofilm generated by PANI grease,current-induced softening effect and micro-bearing effect of the PANI particles.ANSYS was used to simulate the wear process and analyze the stress distribution of the contact area,speculate the wear behavior of Ag coating.