Electrochemical machining of refractory materials

The feasibility of the electrochemical machining (ECM) of pure TiC, ZrC, TiB₂ and ZrB₂ has been established. In addition, the ECM behaviour of a cemented TiC/10% Ni composite has been investigated and compared to that of its components, TiC and nickel. ECM was carried out in 2M KNO₃ and in 3 M NaCl at applied voltages of 10–31 V and current densities of 15–115 A cm^–2. Post-ECM surface studies on the TiC/Ni composite showed preferential dissolution of the TiC phase during machining.Nomenclature E ₀ thermodynamic equilibrium potential (V) - F Faraday's constant (96 500 Coul mol^–1) - toolpiece feed rate (cm s^–1 or mm min^–1) - I current (A) - i current density (A cm^–2) - k electrolyte conductivity (^–1 cm^–1) - l interelectrode gap (mm) - mass removal rate (g s^–1 or g min^–1) - M formula weight (g mol^–1) - Q electrolyte flow rate (l min^–1) - t electrolyte temperature (°C) - V applied voltage (V) - V _IR ohmic drop through electrolyte (V) - z apparent valence of dissolution (eq mol^–1) - _i overvoltages (V) - density of refractory materials (g cm^–3)