Electrochemical machining of groove on tungsten using bipolar pulses and auxiliary electrode

Abstract

Electrochemical machining (ECM) directly controls the dissolution of anodic materials in the fabrication of metallic parts. The electrochemical dissolution behavior of the workpiece material is determined by its electrochemical properties rather than its hardness. Consequently, it is easy to machine difficult-to-cut materials such as tungsten. However, conventional ECM using a unipolar pulse (UP-ECM) and a neutral electrolyte (NaNO₃ aq) is difficult to machine tungsten, because tungsten oxide (WO₃) with a high impedance is generated in the machining area, which hinders the further dissolution of tungsten. In our previous study, an ECM method using bipolar pulses and an auxiliary electrode (BPAE-ECM) was used to induce intensive hydrogen bubbles, thereby reducing stray corrosion. In this study, this method was used to remove WO₃ and machine grooves on tungsten. During the negative pulse period, the workpiece acts as the cathode and generates hydroxide ions (OH^-) from hydrogen evolution to dissolve WO₃, allowing the process to continue. Based on this theory, ECM experiments were conducted to investigate the machining characteristics of tungsten.