Numerical investigation of the swirl gas angle and arc current dependence on evaporation of hafnium cathode in a plasma cutting arc

The effects of arc current and swirl gas angle on a plasma cutting arc are investigated using a 2-D thermofluid model developed for arc plasma with consideration of hafnium (Hf) cathode evaporation. Numerical modeling is extremely important to predict the erosion amount of Hf cathode for different process parameters in plasma cutting arcs. Results show that a larger swirl gas angle causes a high-temperature plasma area in front of the cathode surface shrunken in the radial direction and that the flow patterns changed to the opposite direction in front of the cathode at swirl gas angles from 12^° to 30^°. This change in the gas flow pattern induces Hf vapor transport along the center-axis direction to the nozzle outlet. With the increase of arc current, the whole temperature field markedly increases, and the radius of arc plasma is expanded in the radial direction. The total amount of mass loss of Hf cathode evaporation was predicted to be enhanced with increasing arc current and swirl gas angle from 12^°.