Observation of Workpiece Surface in ECM Process of WC Alloy Micro-pin with Bipolar Pulses

In this study, WC alloy micro-pins were fabricated by electrochemical machining using a NaNO3 aqueous solution and bipolar pulse supply. Since the influence of the pulse conditions on micro-pin formation is still unknown, the micro-pin fabrication was carried out by changing the pulse period, the pulse width, and the power supply system. Since finding what happens in the inter-electrode area may be helpful to understand the mechanism of machining using bipolar pulses, observations of the micro-pin surface during the process were carried out using a high-speed camera. As a result, it was found that the colour of pin surface becomes blue momentarily when the pulse voltage falls in the case of using a bipolar pulse power supply. In addition, the relationship between the pulse waveform and the blue appearance period was experimentally investigated and