Effect of tungsten carbide grain size in jet electrochemical machining

Electrochemical machining (ECM) of carbide metals, e.g. tungsten carbide, is highly challenging compared to ECM of metals, because these materials are composites of covalently bound carbides embedded in a metallic binder matrix. In the ECM process dissolving and passivating effects occur simultaneously and dissimilarly. Nora Schubert et al. Investigated a mixed electrolyte consisting of aqueous solutions of sodium nitrate (1.2 mol/l) and sodium hydroxide (0.6 mol/l), which is suitable for electrochemical shaping of tungsten carbide with cobalt binder [1]. In this study Jet Electrochemical Machining (Jet-ECM) of three different tungsten carbide alloys applying the mentioned mixed electrolyte is presented. The metallic binder of the hard metals is cobalt at a ratio of 6 %. The investigated materials differ with regard to the size of the carbide grains. Machining experiments in Jet-EC milling were accomplished to investigate the influence of the applied voltage as well as and the milling speed on the eroded structures. Therefore, the geometrical dimensions removal width and removal depth were detected and the surface finishes of the milled grooves were measured, each by confocal microscopy.