Comparative Study on the Erosion Mechanism of W70Cu30 Anode in DC Gaseous Arcs

An in-situ diagnostic system with respect to the determination of the surface temperature and the splashing erosion quantities was established. Comparative study on the transition phenomenon of the erosion mode of W₇₀Cu₃₀ anode was carried out in Ar and H₂. Two erosion modes were identified, namely an evaporation-dominated mode and a splash-dominated mode. The results indicate that the detachment of the splashing droplet is driven by the explosion of surface bubbles. Moreover, it is found that the discrepancy in the melting and boiling points of the copper phase and the tungsten skeleton limits the anode surface temperature at first, but promotes the molten ejections through the bubble burst which originates from the copper vapor, when the copper layer above the tungsten skeleton is depleted. These characteristics control the formation of molten pool on the W₇₀Cu₃₀ anode, and lead to the transition of two erosion modes.