Electrode wear protection mechanism in meso–micro-EDM

A carbonaceous layer builds up on the electrode surface in electrical discharge machining (EDM) when using low wear settings. Current paper investigates the carbonaceous layer and its formation during the erosion. It is found that a diamond like amorphous carbon layer embedded with the micro and nanosized metallic debris from the work-piece is deposited on the erosion front of the electrode. The microstructure of the layer depends on the parameters such as applied current and pulse duration. The diamond like carbon layer with sp3 bonds has lower thermal conductivity and higher hardness compared to the base graphite material, protecting it against the wear. A dense layer with larger porosity is formed when using 20 A and stacked carbon layers with submicron porosity are formed during the erosion with 5 A. A simple thermal model is proposed to simulate the pulse duration values at which the protective carbonaceous layer forms over the complete frontal surface of the micro-scale electrodes with projection area below 1 mm2.