Improvements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinking and milling of titanium alloy

Abstract

Electrochemical milling is eminently suitable for machining aerospace parts (which usually have complex structures) because of its great flexibility. However, titanium alloys are particularly sensitive to changes in the flow field, which often cause severe pitting corrosion of the machined surface. Although electrochemical sinking and milling (ESM) can restrict the flow of electrolyte and reduce pitting corrosion, the quality of the machined surface is not ideal because the latter are susceptible to stray corrosion. To reduce such corrosion and improve the surface quality, the internal flow channel of the tool electrode and the cutting depth were investigated thoroughly. Extensive experiments revealed that stray corrosion could be reduced significantly and surface quality improved by controlling the electrolyte flow direction in the machining area, which was achieved by changing the style of the internal flow channel of the tool electrode. These reductions in corrosion and surface roughness were achieved using a tool electrode with a triangular internal flow channel. In addition, the main components and micro-hardness of the machined surface were close to that of the TB6 titanium alloy substrate, which helped to maintain the inherent high strength of the titanium alloy. The surface of the workpiece changed from being hydrophilic to being hydrophobic, which reduced the flow resistance.