Microstructure and arc erosion behavior of WC/CuCr30 composites based on nano-Cr precipitation

Abstract

CuCr alloys with high contact performance for medium and high voltage vacuum circuit breakers are becoming increasingly urgent. In this work, WC/CuCr30 composites were prepared by SPS process, and nanometer-sized precipitated Cr phases were obtained by subsequent heat treatment. The microstructure and arc erosion behavior were investigated. The results show that nano-Cr phase precipitated in copper matrix can effectively improve the interfacial bonding strength between the Cu matrix and WC particles, and part of the precipitated nano-Cr phase is combined with the C element in WC to form nano-Cr23C6. Both nanophases can improve the resistance to dislocation and sub-grain boundary movement in the deformation process of WC/CuCr30 composite, thus improving the hardness of the copper matrix with a slight decrease in electrical conductivity. The results of electrical contact show that the addition of WC particles and nano-Cr precipitates can not only extend contact life of CuCr material, but also help to disperse the arc to avoid concentrated erosion. The presence of Cr23C6 phase around WC particles effectively improves the interfacial bonding between Cu phase and WC phase and reduces the probability of pore existence at the interface, which is beneficial to vacuum breaking performance.