| Current-carrying friction pairs are functional friction pair with the function of current transmission.With the continuous development of modern industry and information industry,current-carrying friction pairs are widely applied in railway traffic,power generation,automation,aerospace,military electronics and other fields.At the same time,due to increasingly harsh service environments,such as accelerating relative sliding velocity,increasing voltage and transmission current,the service life and stability of current-carrying friction pairs are severely challenged,which has become the main obstacle restricting the reliable service of key components in related fields.The process of current-carrying friction involves the coupling effects of force,heat,electricity and other factors.The service environment factors and intrinsic characteristics of materials have significant effects on the tribological behavior.In this paper,Cu-8.33Ni-1.67Si alloy and GCr15 bearing steel are used as experimental materials.The effects of friction conditions(load,sliding velocity and current),microstructure and material properties on the friction behavior of Cu-8.33Ni-1.67Si alloy were investigated.Firstly,the mathematical models of the relationship between friction conditions,friction coefficient and wear rate were established by using as-cast Cu-8.33Ni-1.67Si alloy as experimental material through comprehensive experiment and regression analysis.On this basis,by changing the friction conditions,the friction behavior of Cu-8.33Ni-1.67Si cast alloy under three different working conditions,namely,mechanical friction,Joule thermal coupling mechanical friction and current carrying friction,mainly arc erosion,was investigated.The effects of mechanical friction,Joule thermal effect and arc erosion on the wear mechanism were discussed by comparison.Finally,the microstructure of Cu-8.33Ni-1.67Si alloy was changed by heat treatment and multidirectional compression,and its mechanical properties,electrical properties and friction and wear properties were tested.The relationship between the microstructure and friction and wear behavior of Cu-8.33Ni-1.67Si alloy was investigated.The main conclusions of this paper are as follows:(1)The effect of current on the friction coefficient and wear rate of Cu-8.33Ni-1.67Si as-cast alloy is closely related to the load and velocity.When the load is small and the current increases to a certain critical value,GCr15 bearing steel material is easier to liquefy and melt under the action of arc erosion and cold weld to the surface of the cast alloy to form a dark oxide film.Before the oxide film is not damaged,its friction coefficient and wear rate will decrease greatly.And when the speed and load values are large,the wear of the as-cast alloy will be aggravated by the intervention of current.(2)Under the absence of current,as the load increases,the plastic flow in the subsurface of the as-cast Cu-8.33Ni-1.67Si alloy will cause the crack nucleation at the interface of the mesh grain boundary phase Ni31Si12 and the matrix,and the cambium flake chips will be shed in parallel expansion during the subsequent friction process.ST+MC+AT treatment can refine the coarse mesh grain boundary phase Ni31Si12,greatly reduce its quantity,effectively inhibit crack initiation,and improve the wear resistance of the alloy.(3)After solution aging treatment,the precipitation of Ni2Si phase improves the hardness,conductivity and tensile strength of Cu-8.33Ni-1.67Si alloy.Under 1N load conditions,Compared to solid solution alloys,their furrow scratches are significantly reduced and their wear resistance is improved.(4)Under 10N load conditions,the joule heat ratio increases gradually with the increase of current,the main wear mechanism of Cu-8.33Ni-1.67Si as-cast alloy changes from fatigue wear to adhesive wear.The appearance of adhesive wear makes the value of friction coefficient and its fluctuation range increase obviously,at this time,the higher the hardness and conductivity of Cu-8.33Ni-1.67Si alloy,the better its wear resistance. |
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