Study of Graphite Tool Wear in EDM with Water-based Dielectrics and EDM Oil

Abstract

Using water-based dielectrics and high-energy density electrical discharge machining for titanium alloy and superalloy has shown promising economic advantages. Combined with sinking-EDM, its finishing quality can be further enhanced. However, the relatively high tool wear rates restrict the use of water-contained working fluid in sinking-EDM. As EDM is widely used for the machining of slots and holes, it is necessary to study the tool wear in these situations. In this paper, the mechanism of electrode loss is studied in 6 kinds of dielectrics, including EDM oil, WEDM working fluid, tap water, deionized water, emulsion, and polyethylene glycol solution. Two kinds of graphite materials were compared to explain the tool wear mechanism. Electrolysis consumption and discharge erosion were evaluated by experiments. The aim of this study is analyzing the effect of electrolysis and spark explosion on the performance of tool wear as well as their relation with dielectric characteristics. According to slot machining and electrode electrolysis experiments, carbon content and conductivity are regarded as the main influence factors. It is found that the dielectrics with higher carbon content can effectively reduce the tool wear in the machining process and electrolysis can lead to thinning of the electrode which makes it crumbly. This work can help compound suitable dielectrics and choose appropriate graphite electrode materials with lower tool wear in EDM machining.