Cathode diameter and operating parameter effects on hafnium cathode evaporation for oxygen plasma cutting arc

Evaporation of hafnium cathode in a plasma cutting arc torch was investigated numerically and experimentally to assess the effects of cathode diameter and operating parameters such as gas pressure, gas flow rate and arc current. A numerical model was developed for arc plasma with consideration of hafnium cathode evaporation. Using this model, the surface cathode temperature and the amount of cathode mass loss caused by evaporation were predicted for different operating parameters. Simulated results show that the cathode surface temperature decreases at the hafnium cathode centre with increasing gas flow rate and cathode diameter. However, an increase in gas pressure elevates the surface cathode temperature in the radial range of 0.35 mm. The total amount of mass loss of hafnium cathode evaporation was predicted to be enhanced with increasing gas flow rate, gas pressure and cathode diameter as well. Comparison of the calculated results with experimentally obtained results shows good agreement in terms of the average surface cathode temperature, with variation in gas pressure and cathode diameter.