An experimental comparison of the erosion in tungsten cathodes doped with different rare-earth elements

Abstract

Three different types of tungsten-based cathodes (thoriated, lanthanized and ceriated) were used in plasma torches operating at different current intensities ranging from 30 to 210 A. For each one of the current intensities used, the erosion rate was measured for each of the cathode types, thereby obtaining for them the curves describing the dependence of the erosion on the current intensity. The effects of erosion on the cathode surface were explored by scanning electron microscope and energy-dispersive x-ray spectrometer. On each of the types of cathodes studied, the cathodic erosion had a maximum for a critical value I* of the current intensity. The value of this critical current intensity depended on the dopant used. The following values were obtained: ITh* = 50 A for thoriated tungsten, ICe* = 80 A for ceriated tungsten and ILa* = 110 A for lanthanized tungsten.

An experimental study of thoriated tungsten cathodes operating at different current intensities in an atmospheric-pressure plasma torch

“…Our goal in the present paper is to investigate the behaviour of these cathodes over a wide range of arc current intensities. Thoriated tungsten cathodes have been experimentally studied by different authors [1][2][3][4][5][6][7][8][9][10][11], but in most of the studies, the cathodes were operated with only a few current intensities; therefore, the dependences of the cathode parameters on the arc current intensity I were not found.In the present paper, we discuss our experimental investigation of thoriated tungsten cathodes operating in the actual working conditions of an industrial plasma torch. We used arc current intensities ranging from 30 A to 200 A, which allows the investigation of cathode…”

Characterization of a spark discharge for dust cloud ignition

“…The cerium dopant promotes a lower electron work function and a higher current intensity. [14] Analyses by EDS (energy-dispersive X-ray spectrometry) and scanning electron microscopy (SEM) imaging show that the tip is depleted in cerium and appears darker than the rest of the electrode, which remains unaltered (see Figure 3). The same phenomenon is observed in several doped tungsten electrodes, showing three characteristic zones on the electrodes tip: a high-erosion zone coresponding to a bright emission area, a smooth dopant-depleted zone due to oxide vaporization without melting of the electrode metal, and, finally, a rough surface-dopant-enriched zone.…”

“…[5][6][7][8][9] In all cases, the electric spark interacts with material over a time duration of a few milliseconds, during which all chemical processes of heat transfer from the electric arc to the flammable product take place. [13][14][15] However, in the context of application to ignition of combustible material, the discharge plasma becomes the centre of interest, be it primarily a thermionic or field emission. In fact, the numerous theoretical and experimental studies on electric arcs generally deal with electrode phenomena in order to improve the performance of the electron emission of the cathode and its resistance to erosion.…”

“…In fact, the numerous theoretical and experimental studies on electric arcs generally deal with electrode phenomena in order to improve the performance of the electron emission of the cathode and its resistance to erosion. [13][14][15] However, in the context of application to ignition of combustible material, the discharge plasma becomes the centre of interest, be it primarily a thermionic or field emission. In addition, the spatio-temporal distribution of the plasma discharge parameters such as temperature and electron density is poorly known over a wide current density range.…”

Зависимости Теплофизических Параметров Активированных Термоэмиссионных Катодов От Тока В Стационарном Дуговом Разряде

“…Такой подход позволяет при атмосферном давлении в достаточно узком диапазоне рабочих токов (20−150 A) получать тепловые режимы, характерные для интенсивно охлаждаемых узлов сильноточных плазмотронов (10 2 −10 3 A). получены при измерении удельной эрозии активированных W-катодов на токах 30−200 A [11].…”