Material removal rate and machining accuracy of electrical discharge machining (EDM) of Inconel 718 using copper electrode

Abstract

Electrical Discharge Machining (EDM) is a non-contact thermal machining process capable of machining conductive and semi-conductive materials. These capabilities bring to admission of machining materials that characteristically difficult to machine such as Inconel 718 due to its ability to maintain hardness at elevated temperature. Nickel based super alloy, Inconel 718 is one of the difficult to machine material that widely used in such high temperature application. The purpose of the study is to examine the Inconel 718 machinability by applied variable parameters such as peak current, pulse duration and repetitive used of electrode. To obtain the high performance measure in EDM, the selected peak currents were high where it is from 20 to 40A while for pulse duration is from 200 to 4μs. The performance measure that being evaluated are material removal rate (MRR), surface topography and machining accuracy. This research used Copper as electrode due to its high electrical conductivity and achieved highly in MRR. With the series of repetition used of electrode, the carbon layer known as black layer will formed at the surface contact of electrode. The relationship between the parameters and performance measure were more profound through the combination of machining parameters and black layer on the electrode. At high material removal rate, the surface topography of Inconel 718 look rougher with bigger sizes of nodules and craters produced. In the case of machining accuracy, it was found that, overall diameter overcut are less than 3.47%. The result shows that, even applying high peak current and pulse duration, the results of the machining accuracy is still acceptable.