Electrochemical Machining of cemented carbides

• The electrochemical behavior of WCCo is a superposition of the behavior of the individual phases Co and WC
• A homogenous dissolution of the hard and binder phase is achieved using an electrolyte mixture of NH3 and NaNO3
• Co dissolves transpassively and the dissolution mechanism of WC is of active nature
• SEM and EDX analyses of the surface confirm the aforementioned statement.
• The current efficiency decreases from ≈ 100% at 5 Acm− 2 to ≈ 70% at 20 Acm− 2 and keeps constant at this value

The present work is focused on the electrochemical behavior of tungsten carbide cobalt in alkaline ammonia electrolytes under near-ECM conditions. Potentiodynamic measurements were carried out in an electrolyte mixture of sodium nitrate and ammonia. It could be shown that a homogenous dissolution of both phases, the hard phase tungsten carbide and the binder phase cobalt, is possible with this electrolyte mixture. Additionally, galvanostatic pulse experiments coupled with polarographic analysis of the waste electrolyte were carried out to investigate the current efficiency of the machining process. Current efficiencies between 70 and 100% can be achieved under the chosen conditions dependent on the current density.