Craters caused by high voltage ignition discharges on the surface of materials are important features of the erosion processes of electrodes. In this paper, a thermal simulation of the crater formation on a platinum cathode is carried out by means of the finite element method (FEM). The model is based on the modelling of cathode spots and includes phenomena such as ion bombardment, electron emission, vaporization, melting and heat conduction. The surface of the cathode is submitted to various ion power densities (1010–1012 W m−2) of different durations (0.1, 1 and 10 µs) over a disc of a radius a = 10 µm. By comparing the results of the simulation with experimental data of molten depths and molten volumes, characteristic values of the time, the ion power density and the current involved in the crater formation are determined. These values are related to the electrical characteristic of an ignition discharge, permitting the identification of the phase producing the crater. Furthermore, the contribution of the different heat dissipation mechanisms is evaluated and discussed.

Plasma erosion craters caused by electrical discharges on the surface of materials are important features of the erosion processes resulting in the degradation of electrodes. In the present work, electrical discharges were produced on a bi-metallic Ni/Cu multilayered surface. By means of Dual Beam techniques, coupling a focused ion beam (FIB) and a scanning electron microscope (SEM), not only the surface but also the sub-surface structure of the craters were investigated. Using the combination of SEM, FIB and STEM-EDX, a complete three-dimensional investigation of the craters were carried out. The analysis of the microstructure modifications as a function of depth enabled to determine the field of interaction between the plasma and the material.

This paper presents the characterisation of erosion craters caused by high voltage ignition discharges on the surface of electrodes. By means of FIB/SEM dual beam techniques such as FIB‐cross sectioning, FIB‐nanotomography and FIB‐EBSD, the microstructure modification below the crater surface is investigated, providing new insights into erosion crater phenomena. It demonstrates also that the use of FIB/SEM is ideally suited for assessing the microstructural nature of sub‐micron surface degradation features.

No abstract

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007