Investigation of erosion mechanism of tungsten-based cathode in Ar-N₂ DC arc

Direct current arc has been used in a wide industrial field. Reducing in cathode erosion is an important issue for process cost reduction, however the erosion mechanism under molecular gas as plasma supporting gas has not been clarified yet. The purpose of this research is to elucidate the erosion mechanism of tungsten based cathodes in atmospheric pressure Ar-N₂ DC arc. The metal vapor generated from the cathode surface was successfully visualized by a high speed camera system with a pair of band pass filters. Combing the visualization with the cahtode temperature measurements provides the tungsten vapor evaporation mechanism; tungsten vapor was generated not from the high temperature part of the cathode tip but from the peripheral part. The arc temperature measurement confirmed that ionization of tungsten atoms in the high-temperature region of the arc caused to this characteristic distribution of tungsten vapor. These findings advance the understanding of such electrode phenomena leading to increased use time of the electrode, and as a result the industrial use of N₂ arcs is expected to expand.