Simultaneously enhanced mechanical and electrical performance of Cu-10wt.%Mo contact material by the addition of graphite

Abstract

To disclose the effect of graphite (G) addition on the mechanical and electrical performance of CuMo contact material, the Cu-10wt.%Mo contact materials without and with 1wt.%G addition were prepared by mechanical wet-mixing and spark plasma sintering. The electrical performances of the resultant materials were comparatively studied by electrical contact test under different currents, and the surface morphology and composition of the eroded electrodes were characterized by scanning electron microscope and energy dispersive spectrometer. As compared to the Cu-10wt.%Mo contact material, the hardness, tensile strength, flexural strength of Cu-10wt.%Mo-1wt.%G contact material are respectively increased by 33.7 %, 21.7 % and 9.7 %, while the electrical and thermal conductivity are only reduced by 2.3 % and 1.0 %, respectively. With increase of current, the Cu-10wt.%Mo-1wt.%G contact material presents lower make-arc-energy and shorter make-arc-duration with less fluctuations than the Cu-10wt.%Mo contact material without G addition. The average make-arc-energy and make-arc-duration of Cu-10wt.%Mo-1wt.%G contact material are decreased by 45.1 % and 62.6 %, respectively. Moreover, the addition of graphite remarkably alleviates the arc erosion. The total mass loss and relative transfer mass of the Cu-10wt.%Mo-1wt.%G contact material after 5000 operations are respectively reduced by 33.3 % and 14.3 % when compared with Cu-10wt.%Mo contact material. This can be ascribed to arc erosion preferentially occurred on the graphite with low work functions, and the released CO2 which promotes arc extinguishment. Furthermore, the addition of graphite increases the viscosity of the molten pool, restraining the splashing and evaporation of the molten Cu.