Electrochemical micromachining on titanium using the NaCl-containing ethylene glycol electrolyte

Titanium has been widely applied in industry owing to its excellent properties such as low density, high strength, and corrosion resistance. Compared with traditional mechanical methods, electrochemical micromachining (EMM) has some inherent advantages for the shaping of hard metallic materials; therefore, it is a promising method for the micromachining of titanium. However, the high corrosion resistance of titanium owing to its stable oxide film is a drawback during EMM. To overcome this limitation, a novel electrolyte, NaCl-containing ethylene glycol (EG) solution, was applied in this study. The polarization behavior of titanium in the NaCl water-based and ethylene-glycol-based solutions was comparatively analyzed. In contrast to that in the water-based solution, no oxide film was formed during anodization in the NaCl-containing EG solution. This characteristic could potentially improve the machining performance of the EMM of titanium. Subsequently, the effect of the main process parameters on the machining performance was investigated. Accordingly, peak voltage of 40 V, pulse width of 25 μs, and feeding rate of 1 μm s−1 were selected as the optimum parameters. Using the optimum parameters, a high-quality microhole with 149.5 μm average diameter, 300 μm depth, and 7.6° taper angle was successfully EMM machined on titanium.