Distribution of molten layer and anode erosion pattern caused by constricted vacuum arcs

The objective of this paper is to investigate the influence of constricted vacuum arcs on the distribution and microstructure of the molten layer of anode surface. A pair of axial magnetic field contacts was set in a vacuum chamber with contact material CuCr25 (25% Cr) and the contacts diameters were 42 mm. The arc modes observation was recorded by a high-speed CCD, and the microstructure of the cross section of anode surface molten layer in sampling erosion region was observed by a scanning electron microscopy. The Cr contents of different erosion regions were measured by an energy dispersion spectrometer. The experimental results show that the constricted vacuum arcs melted the anode surface material and caused a motion which pushed the melting material from the center to the peripheral region on the surface. The motion leaded to a distribution of anode molten layer, and the Cr spheres in the molten layer of different erosion regions had quite differences both in size and shape. Moreover, with the influence of constricted vacuum arcs, the Cr content in central and periphery areas changed into 31% and 18%, respectively, which deviated from 25% before the experiments.