A study on the fine-finish die-sinking micro-EDM of tungsten carbide using different electrode materials

Abstract

In recent years, tungsten carbide (WC) and its composites (WC-Co) are widely used in the die and mold industries due to their unique combination of hardness, strength and wear resistance. Micro-EDM is one of the most effective methods for machining these extremely difficult-to-cut materials. However, numerous applications of WC often involve intense mechanical demands at the surface. Therefore, fine-finish micro-EDM of WC is becoming an imminent and important issue. In this study, investigations have been conducted with view of obtaining fine surface finish in the micro-EDM of WC using tungsten (W), copper tungsten (CuW) and silver tungsten (AgW) electrodes. It was found that the surface characteristics are dependent mostly on the discharge energy during machining. The fine-finish micro-EDM requires minimization of the pulse energy supplied into the gap. In addition, the surface finish was found to be influenced greatly by the electrical and thermal properties of the electrode material. The performance of the electrodes for the finishing micro-EDM was evaluated based on the achieved surface roughness and surface characteristics with respect to material removal rate (MRR) and electrode wear ratio (EWR). It was found that AgW electrode produces smoother and defect-free nanosurface with the lowest Ra and Rmax among the three electrodes. Besides, a minimum amount of material migrates from the AgW electrode to the WC workpiece during the finishing micro-EDM. On the other hand, CuW electrodes achieved the highest MRR followed by AgW. In the case of electrode wear, the W electrode has the lowest wear followed by CuW and AgW. Finally, considering all the performance parameters, AgW appears to be the best choice for finish die-sinking micro-EDM of WC. © 2008 Elsevier B.V. All rights reserved.