Improvements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinkin
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provements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinking and milling of titanium alloy *
LIU Yang & QU NingSong
National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China Received June 30, 2020; accepted August 13, 2020; published online October 28, 2020
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. electrochemical sinking and milling, titanium alloys, flow direction, surface quality and characteristics Citation:
Liu Y, Qu N S. Improvements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinking and milling of titanium alloy. Sci China Tech Sci, 2020, , https://doi.org/10.1007/s11431-020-1708-3
1 Introduction To manufacture aerospace parts that are strong and lightweight, titanium alloys (which are typically hard-to-cut materials) are widely used. At present, the main machining methods used are high-speed milling and grinding, electrical discharge machining (EDM), and electrochemical machining (ECM) [1–4]. For high-speed milling and grinding, tool wear is a particularly serious problem. For EDM, a recast layer is formed readily on the machined surface, which seriously affects the surface properties. For ECM, tool wear or recast *
Corresponding author (email: [email protected])
layers are not created during machining, and so it has become an important technology for the manufacturers of aerospace parts [5–7]. “Electrochemical milling” is a brand new form of ECM that has great flexibility and is suitable for machining aerospace parts that have complex structures. This proc
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