Modelling and experimental evidence of the cathode erosion in a plasma spray torch

Abstract The lifetime of tungsten cathodes used in plasma spray torches is limited by processes leading to a loss cathode material. It was reported the literature that mechanism their erosion evaporation. A model ionization layer developed study diffusive transport evaporated atoms and ions produced due electron impact background argon plasma. shown Stefan–Maxwell equations do not reduce Fick law as one could expect for diluted species, which significant diffusion velocities ions. occurs distance few micrometers from surface leads strong sink, increases net flux far beyond obtained absence This shows are driven electric field towards resulting no removal species even if convection accounted for. possible found extending comprise an anode. extended resolves inter-electrode region provides parameters current density corresponding value at center under typical arc currents 600 800 A. presence anode causes reversal on side, pulls away cathode. can be further fortified convection. allows evaluate material realistic operating conditions quantitative agreement with measured values.