Study On Current Carrying Friction And Wear Behavior Of Silver-Copper Matrix Composites

In this paper,four kinds of samples of electrical contact silver(copper)matrix composites were prepared by powder metallurgy method.Firstly,physical and mechanical properties of the electrical contact test composites were tested and the micro-structure of the material were investigated.Then,the friction and wear tests were carried out on the self-made ring-block friction and wear testing machine under atmospheric conditions.The silver-based composite materials and the brass slip ring form a pair of friction pairs,to change the input parameters(current,sliding speed,Pressure)and collect the output parameters(contact resistance,friction coefficient,wear amount),we can use the above parameters to analyze the composite's electrical contact friction and wear properties.Finally,based on the input and output data,combined with the contact surface morphology of the composite,the frictional wear state and friction mechanism of the composite were analyzed.Research indicates:(1)In silver-copper-based composite materials,the greater the content of graphite or graphene added as a solid lubricant,the lower the strength of the composite material and the lower the density thereof.In the composite structure,the better the metal matrix connection,that's to say,the better the integrity of the metal mesh skeleton,the better the conductivity of the composite material and the higher the strength.The addition of lead to the metal matrix has no significant effect on the strength and density of the composite.Combining the bending strength,resistivity,hardness and micro-structure of composites,Samples of component 2(80 wt.% silver-14 wt.% copper-6 wt.% graphite)and component 3(72 wt.% silver-20 wt.% copper-8 wt.% graphite)have relatively better static performance.(2)In the current-carrying friction and wear test,when the pressure and velocity were constant(1.7N,600r/min),the effects of carrier flow size on the friction and wear properties of the composites were analyzed.The friction coefficient of the composite material increases with the increase of the current load.The friction coefficient of the graphene-silver-copper based composite is lower than that of the graphite-silver-copper based composite.Under the condition of low applied current(?20A),addition of 2wt.%lead in the matrix metal can reduce the amount of wear of the material,but it has no obvious effect on the friction coefficient.The resistance of the contact surface duringthe rubbing process also increases with the increase of the current load.When the current load is constant,the contact resistance of the sample 1(76 wt.% silver-20 wt.%copper-4 wt.% graphene)is the smallest,the sample 4(70 wt.% silver-20 wt.% copper-8 wt.% graphite-2 wt.% lead)has the highest contact resistance.During the gradual increase of the load current(0-30A),the greater the current,the greater the amount of wear of the composite.(3)In the current-carrying friction and wear test,when the pressure and the applied current(1.7N,20A)are fixed,the effect of the change of the friction speed on the friction and wear properties of the composite material is analyzed.The friction coefficient of composites shows a decreasing trend with increasing sliding speed.When the speed increases to 800r/min,the change of friction coefficient tends to be stable.The contact resistance of the friction surface decreases as the sliding speed increases,and at a certain speed,with the increase of the friction time,the contact resistance has experienced a process from small to large and tends to be stable.Among them,the stability of the contact resistance of Sample 1 is the best.The wear loss of composites increases with the increase of sliding speed.In the four composite samples,the abrasion resistance of Sample 3 is relatively good,and the increase in wear is minimal and stable.(4)During the friction and wear process,the contact pressure has a certain influence on the friction coefficient,contact resistance and wear amount.When the contact pressure is large,the friction coefficient is large and the contact resistance is small;when the contact pressure is large,the amount of wear is also increased.(5)Under the condition of current-carrying friction and wear,the main wear mechanisms of silver-based composites are adhesive wear,abrasive wear and arc ablation.