Investigation On Preparation And Electrical Characteristics Of Ag-ZrB₂-Gr Contact Materials

Ag-ZrB2 contact materials with different additions of ZrB2 and graphene(Gr)were prepared by ball milling,three-dimensional vibration blending and spark plasma sintering.The effects of ZrB2 and Gr additions on the microstructure and properties of Ag-ZrB2 contact materials were systematically studied,especially,the arc erosion and material transfer behavior of Ag-4wt.%ZrB2 contact materials with different additions of Gr at different load voltages were investigated.Scanning electron microscopy(SEM),laser condensing microscopy(CLSM),and energy dispersive spectrometer(EDS)were used to characterize the surface morphology and chemical composition of Ag-based contact materials after arc erosion.Based on the above studies,the following conclusions can be obtained.(1)The ZrB2 content significantly affects the conductivity and hardness of Ag-ZrB2 contact materials.With increase of ZrB2 addition,both the relative density and electrical conductivity of Ag-ZrB2 contact material decrease,whereas the hardness increases and then decreases.At the range of experiments,Ag-4wt.%ZrB2 contact material has the optimum properties,and the relative density,electrical conductivity and hardness are 97.5%,47.8HV and 55.2%IACS,respectively.(2)The addition of Gr significantly affects the conductivity and hardness of the Ag-4wt.%ZrB2 contact material.With increase of Gr addition,the electrical conductivity of Ag-4wt.%ZrB2 contact material increases and then decreases,while the hardness decreases and then increases.At 0.2wt.%Gr,the Ag-4wt.%ZrB2 contact materia has the largest hardness(58.8HV).The electrical conductivity of Ag-4wt.%ZrB2 contact material with 0.4w.%Gr added is 65.6%IACS.(3)At DC16A,for both make arc and break arc,the arc-duration and arc-energy increase with increasing load voltage.Additionally,under different load voltages,the direction of Ag-4wt.%ZrB2 contact material transfer is also different.At 12V and 36V,the material is transferred from the cathode to the anode.However,at 24V,the material is transferred from the anode to the cathode.(4)At DC16A/24V,the addition of Gr changes the micro-particles that support arc combustion,thereby changing the transfer direction of the Ag-4wt.%ZrB2 contact material.The transfer direction of Ag-4wt.%ZrB2 contact material with Gr added is from the cathode to the anode,which is opposite to the transfer direction of Ag-4wt.%ZrB2 contact material without Gr added.And the addition of 0.2wt.%Gr helps to reduce the erosion area,and the mass loss,relative transfer mass and welding force are all the lowest.Significantly improved the material transfer resistance and welding resistance of Ag-4wt.%ZrB2 contact material.