Investigation On Microstructure And Properties Of AgSnO₂ And AgTiB₂ Contact Materials

AgSnO₂ contact materials were fabricated by powder metallurgy and the effect of SnO₂ particle size and Ag particle size on the microstructure,relative density,hardness,electrical conductivity and arc erosion behaviors of AgSn02 contact materials were studied.Similarly,AgTiB₂ contact material was fabricated,and the effect of TiB₂ powder and SnO₂ powder on the arc erosion behaviors for Ag base contact materials were discussed.The microstructures and compositions of AgSnO₂ contact material and AgTiB₂ contact material after arc erosion were characterized by a scanning electron microscope?SEM?equipped with energy disperse spectroscopy?EDS?,and a confocal lasers canning microscope?CLSM?.From above investigations,the following conclusions can be drawn.?1?Fine SnO₂ particle size is beneficial for improvement on the uniformity,relative density and hardness of Ag-4wt.%SnO₂ contact material,while decreases the electrical conductivity.Compared with Ag-4wt.%SnO₂ contact material prepared with 800nm SnO₂ powders,the relative density and hardness of Ag-4wt.%SnO₂ contact material prepared with 300nm SnO₂ powders are increased by 14.93%and 12.01%,respectively,but the electrical conductivity is decreased by 38.50%.?2?With decrease of SnO₂ particle size,the arc erosion resistance of Ag-4wt.%SnO₂ contact material is enhanced.In comparison with the Ag-4wt.%SnO₂ contact materials prepared with 800nm and 600nm SnO₂ powders,Ag-4.Awt.%SnO₂ contact material prepared with 300nm SnO₂ powders has shorter arc duration and less mass loss,and presents larger erosion area,shallower and more dispersed arc erosion pits and more homogeneous surface composition after arc erosion 50 times.?3?With decrease of Ag particle size,the hardness of Ag-8wt.%SnO₂ contact material increases gradually,but the electrical conduct.ivity first increases and then decreases.Compared with Ag-8wt.%SnO₂ contact materials prepared with 2?m and 0.2?m Ag powders,Ag-8wt.%SnO₂ contact material prepared with 0.8?m Ag powders presents the best arc erosion resistance after arc erosion 50 times,which has the minimum arc duration,the lowest mass loss,the largest erosion area and the most dispersed and shallowest erosion pits.?4?TiB₂ powders have better strengthening effect than SnO₂ powders for Ag base contact materials.Compared with the Ag-8wt.%SnO₂ contact material,Ag-8wt.%TiB₂ contact material exhibits higher hardness,electrical conductivity and arc erosion resistance.After arc erosion 50 times,Ag-8wt.%TiB₂ contact material exhibits shorter average arc duration,less mass loss,larger erosion area and shallower pits,and more homogeneous surface composition.?5?The temperature distributions of Ag-8wt.%TiB₂ contact material and Ag-8wt.%SnO₂ contact material during arc erosion were simulated utilizing ANSYS 12.0 software.The results show that the volume of the molten pool and mass loss of Ag-8wt.%TiB₂ contact material is less than that of the Ag-8wt.%SnO₂ contact material,suggesting that the Ag-8wt.%TiB₂ has better arc erosion resistance.