Study of Surface Modification by Electrical Discharge Machining

* Yamanashi pref. Industrial technology center, Yamanashi, 400-0055, Japan ** Yamanashi University, Yamanashi, 400-8511, Japan *** Uddehorm K.K., Tokyo, 105-0003 ,Japan Abstract In this study we attempted to produce a high-quality surface through the use of Electrical Discharge Machining (EDM). We confirmed the formation of a hardened layer upon mixing Ti powder into the dielectric working fluid. However, surface roughness increased on the treated surface. In this experiment, we applied this treatment to a die having a complicated shape. Some characteristics of the layer modified by EDM were evaluated by surface roughness measurement, X-ray diffraction analysis, and SEM observation. The following results were obtained: 1) Although surface roughness was improved by finishing EDM after surface modification, surface hardness decreased only slightly, 2) When applying scanning EDM, it was evident that a modified layer formed on the surface, 3) When these surface modifications were applied to a metal stamping die for the production ofjewelry, a uniform modified layer was formed over the machined surface. 4) When heat treatment over 600°C was applied to a modified layer, its toughness increased, the hardness of the surface decreased.