Material wear of the tool electrode and metal workpiece in electrochemical discharge machining

Due to its ability to machine both conductive and non-conductive materials, electrochemical discharge machining (ECDM), a non-traditional micromachining method, is widely used. It has high accuracy in metal processing, a high material removal rate (MRR), and a low tool wear rate (TWR). However, there has been little research on the situation that occurs when the TWR becomes higher than the MRR. Moreover, the wear mechanism is not clearly understood because of the complexity of ECDM. In this study, the mechanism by which the TWR becomes higher than the MRR is investigated from three important aspects: (i) type and concentration of the salt solution, (ii) pulse interval, and (iii) energy. Moreover, three processes were observed in the machining area based when electrical discharge machining and electrochemical machining occur together: (i) spark discharge, (ii) ionic bombardment, and (iii) expansion of the plasma channel. These processes are investigated in this paper using experimental data and images. The results show that expansion of the plasma channel in the machining area is the key to the switch in the wear mechanism where the ratio of the TWR and MRR is higher than 1. The surface characteristics of the brass tool electrode and the SUS304 workpiece electrode were analyzed using scanning electron microscopy (SEM) and energy dispersive spectrography (EDS). No signs of chemical etching were found on the tool electrode tip in the SEM images. Moreover, EDS identified tool electrode materials, such as copper and zinc, on the workpiece surface when the wear mechanism changes.