A FEM model was developed to simulate the temperature increase in the material due to the power input of a discharge, which is composed of three different phases: breakdown, arc and glow discharge. In this paper the results for the arc and the glow discharge are dealt with. The model is based on the heat diffusion equation and considers phase transformations. A molten and an evaporated region were simulated and their dimensions were compared with the dimensions of craters made on polished Pt-samples (in air at 1 and 9 bar, with electrode gap of 2 mm). The electrical energy was calculated with the voltage and current curves. Using results of calorimetric investigations published in literature, the fraction of energy absorbed by the electrodes was estimated. The best results of the simulated regions for the arc were obtained for the lower values of energy input. For the largest energies, the evaporated region is overestimated. The molten and evaporated regions are hemispherical and deeper than the craters, which present a flat shape. The glow discharge produces a temperature increase in the electrode of only 1.8 degree, because the energy is distributed in a large area of the cathode.
Pulsed non-self-sustained glow discharge with a large-area hollow cathode for nitriding of iron-based alloys
