Analysis of electrical discharge machining gap phenomena on porous cemented carbides in water and oil by acoustic emission

Abstract

Porous cemented carbides are porous alloys consisting of fine tungsten carbide particles bonded by a metal binder, and are superior to porous ceramics in thermal conductivity and electrical conductivity. Porous cemented carbides are expected to be applied to functional mold components with excellent gas release properties. However, the machining characteristics of porous cemented carbides in electrical discharge machining (EDM), one of the effective machining methods, have not been clarified. In the previous report, we investigated the effect of porous cemented carbide on the EDMed surface properties of single pulse and continuous discharge surfaces and the composition of the melted and resolidified layer, and the machining mechanism discussed. In this study, single pulse and continuous EDM tests were conducted on cemented carbide and porous cemented carbides in oil and water. The distance between electrodes during EDM was measured using a digital displacement sensor, and AE waves generated during EDM were analyzed using an AE sensor, and gap phenomena of porous cemented carbide were discussed. Using this method, the distance between electrodes during discharge was larger on the EDMed surface than on the polished surface in oil, but smaller on the EDMed surface than on the polished surface in water. Furthermore, regardless of the working fluid, the maximum amplitude value was higher for single pulse discharge on the EDMed surface than for single pulse discharge on the polished surface.