Erosion and Lifetime Evaluation of Molybdenum Electrode Under High Energy Impulse Current

Abstract

One of the factors of the functional life of the electrodes used in pulse current discharge depends on the erosion of electrodes. There are many areas that have not been investigated and many areas that require additional study. Some studies have presented results related to the erosion of electrodes made of Cu, Cu–W, Ti, graphite, stainless steel, etc. There is little information available on the erosion of molybdenum electrodes. The erosion of electrodes is related with the electrode material (conductivity, melting point, and density) and the Coulomb charge transferred per impulse. In this paper, molybdenum (Mo) was selected as the main electrode material, considering these factors in addition to high erosion resistance due to high work function and better formability. The performance of pulse discharge devices is mainly characterized by static breakdown voltage, prebreakdown voltage, recovery time, delay time, jitter, and reliability. The degradation of these performance parameters (PPs) is related to many critical factors affecting electrode erosion, consisting of peak current, electrode material, electrode geometry, electrode surface roughness, and gas type. The degree with which the electrode-erosion factors (EEFs) affect the PPs of the pulse discharge device relatively varies and has complex interrelationships, and the relative importance weight of each EEF in order to maximize the life of the pulse discharging device is calculated using quality function deployment and analytic network process methodology. This paper presents experimental work carried out to investigate the erosion characteristics of a molybdenum electrode. Testing was performed at 10–11-kA current discharge every 35 s at a rate of 300 discharges per day with a total of 10 000 shots. The experimental results for Mo electrodes indicate approximately 60 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu \hbox{g/C}$</tex></formula> for 5000-C transfers. For 10–11-kA current transfer with Mo electrodes, we can take about <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$8.5 \times 10^{5}$</tex></formula> shots with wear of 0.3 g without appreciable local wear.