Effect of short-time hot repressing on a Ag-SnO2 contact material containing CuO additive

Abstract

It remains difficult to achieve high-density metal matrix composites by traditional powder metallurgy. In this study, short-time hot repressing was proposed to densify a Ag-SnO2 contact material prepared by powder metallurgy. The effect of the vacuum repressing temperature on the Ag-SnO2 material containing CuO additive was systematically investigated under a constant pressure of 200 MPa. The results showed that the relative density of the material repressed at 800 °C for 10 min can be increased to as high as 99.75%. The microstructure of the Ag-SnO2(CuO) material was obviously refined and homogenized by short-time hot repressing. The dispersive distribution of the SnO2 particles in the Ag matrix was induced, resulting in the elimination of particle aggregation. It is worth noting that almost all the CuO additive was decomposed into Cu2O after hot repressing, which was beneficial for improving the electrical contact properties. Furthermore, the arc energy of the repressed material significantly decreased with increasing repressing temperature, which can be attributed to the high density and uniform microstructure. During arc erosion, the mass loss of the Ag-SnO2(CuO) materials repressed at 800 °C was smallest, and the formation of pores and cracks was inhibited. However, the relative density of the material showed a tendency to decrease when the repressing temperature reached 850 °C.