Erosion mechanism of silver in a single arc discharge across a static gap

The effects of pulse potential and gap distance on the arc erosion mechanism of silver material are investigated by using a static-gap electrical erosion tester with a single arc discharge. The boundary between the arcing and nonarcing regions has been obtained for different anode materials at pulse potential up to 500 V and gap distance up to 40 μm. The erosion pattern diagram is also established for a wide range of pulse potential and gap distance. With increasing pulse potential, the erosion pattern of anode silver is varied from B through B + M and M, to M + G, where B, M and G indicate that the molten metal bridge, metallic and gaseous phase arcs cause the erosion, respectively. At the pulse potential of 500 V, with increasing gap distance, the erosion volume increases, reaches a maximum, and finally diminishes. Meanwhile, the splashing of metallic particles around the crater becomes more dispersed, shorter with more silver powders, and finally disappears with a little silver powder because the gaseous phase arc becomes significant. The thermionic emission causes the erosion patterns of B, B + M, and M, and the mixed thermionic and field emission results in the erosion pattern of M + G