Effect of Ni addition on the arc-erosion behavior of Ag-4 wt.%SnO2 electrical contact material

Abstract

To disclose the effect of Ni addition on the arc-erosion behavior of Ag-4 wt.%SnO2 contact material, the Ag-4 wt.%SnO2 contact materials with and without 4 wt%Ni were comparatively studied. The sintered materials were examined by scanning electron microscopy and transmission electron microscopy. The electrical contact tests were performed for different operations on an electrical contact testing system. The eroded morphology evolution and ingredients of the electrical contact surface under the action of arc were characterized, and the mass loss and welding behavior were studied as well. The results show that the Ag-4 wt.%SnO2 contact material has large break-arc-energy, which aggravates the SnO2 evaporation or decomposition. The reduced SnO2 content further decreases the arc erosion resistance and, in turn, causes much serious arc erosion, thereby resulting in larger mass loss and serious welding. However, for the Ag-4 wt.%SnO2-4 wt.%Ni contact material, Ni addition reduces the evaporation and decomposition of SnO2 due to its high melting point and poor thermal conductivity. Additionally, the reiterative dissolution and precipitation of Ag and Ni under the action of arc lead to the formation of fine precipitation phase, which is beneficial for the arc dispersion and generation of stable arc. As a consequence, the evaporation, splash, mass loss and welding are decreased, and the arc erosion resistance is significantly improved.