Wire-EDM cutting strategies of WC-Co hardmetals: Effect of number of EDM pass on surface integrity

In this study, the effect of the number of wire-EDM passes on the surface integrity of WC-Co hardmetals was investigated. As-received doughnut-shaped WC-25 wt%Co samples were wire EDM'ed with one, two, three and five passes. The resulting surface conditions were investigated in terms of macroscopic and microscopic examinations. Surface roughness and hardness measurements were carried out. Detailed SEM investigations were coupled with EDS analyses. Based on the experimental findings, a detailed cutting strategy was offered for WC-Co hardmetals depending on the expectations of surface conditions, production route, cost and productivity. If there is at least one subsequent process including material removal, wire-EDM with one pass is suggested to decrease cost and increase productivity. However, heat-affected zone (HAZ), recast layer and lower surface hardness region should be removed at subsequent production steps. If there are no production steps to remove HAZ, recast layer and lower surface hardness region, the number of wire-EDM passes should be maximised.