Effect of Aqueous Electrolyte Composition on the Efficiency of Electrochemical Machining of Additive Manufacturing Products Made of Ti–6Al–4V Alloy

Abstract

The influence of the anionic composition of an aqueous electrolyte on the efficiency of the electrochemical leveling of the initial microgeometry of samples obtained by selective electron beam melting (SEBM) at the following mode parameters was studied: a current density of 20 A/cm², an initial interelectrode gap of 0.3 mm, and an average electrolyte pumping speed of 12 m/s. Aqueous solutions of sodium chloride, nitrate, perchlorate, and bisalt electrolytes based on them were studied. It was shown that aqueous solutions of sodium perchlorate have the best microleveling properties among the working media studied, which provides the ability to reduce the parameters Ra and Rz from values of 35 and 180 μm, respectively, to values of 3.2 and 20 μm within 30 s of electrolysis in a direct-flow electrolyzer. It was established that the microgeometry leveling corresponds to the model of the secondary distribution of dissolution rates; two main factors were identified that significantly influenced the result: polarization of the electrodes and a decrease in the oxidation state of metal ions passing into the solution during electrochemical machining in the vicinity of the depression in relation to the protrusion due to changes in the local conditions of electrolysis. Microetching along the grain boundaries in the studied electrolytes was not detected at the adopted electrolysis mode parameters.