Oscillatory behaviour in the electrochemical jet processing of titanium

When appraising the performance of titanium alloys for corrosion resistance in halide environments researchers have well understood pitting and growth mechanisms through electrochemical corrosion. This knowledge is yet to be exploited for the purpose of electrochemical jet processing, a versatile and selective machining technique that is ideal for high-value manufacturing. The applicability of the method towards processing titanium is hampered by the passivating nature oxides which form. In this study, the process of jet interaction with Ti-6Al-4V in the presence of halide electrolytes is deconstructed to establish the fundamental interactions between the jet and surface. This is used to propose the mechanism by which electrolyte, oxide layer and bulk interact to create unfavourable machining phenomena. These manifest as periodic electrochemical oscillations that are accompanied by aberrations in the resulting cut and are influenced by nozzle diameter, translation, current density and flow velocity. Such oscillations can be avoided completely through processing at current densities > 200 A/cm(2). Experimentation is also reported here identifying candidate electrolytes for superior processing of titanium considering feature precision at high current densities (> 300 A/cm(2)). This is valuable knowledge in terms of increasing material removal rate. In this regard, cut edge deviation is reduced by > 20% and profile deviation is reduced by > 40% when applying iodide-doped electrolytes, in comparison to commonly employed chloride solutions.