Electrical Discharge Machining: A Comparative Surface Integrity Study for Incoloy-800

Abstract In this work, effect of EDM input process parameters namely current, pulse-on time, pulse-off time and flushing pressure on Incoloy-800 were investigated and surface morphology of Incoloy-800 machined using three different electrodes were compared. Incoloy-800 is a solid-solution strengthen alloy which has its application in high temperature environment as this is thermally stable up to 816° C and resists carburization, oxidation and sulfidation along with creep strength and rupture at elevated temperatures. Electrode materials chosen were copper, graphite and copper-tungsten as these three are commonly used electrodes for electrical discharge machining. Experiments were conducted in an economical way by varying the machining process parameters at three levels. Experiments were limited to nine based on Taguchi’s method based on L9 orthogonal array. This statistical technique reduced cost and time consumption for conducting experiments. Substrates machined were measured for surface roughness and surface morphology was studied using scanning electron microscope (SEM) and energy dispersive x-ray (EDX) spectroscopy. Influence of input parameters on surface roughness was drawn using Minitab-17 software by ANOVA. Better surface finishing was observed on substrate machined using composite (CuW) electrode and most influencing input process parameter for this electrode is pulse-on time. Increase of carbon percentage in the composition of Incoloy-800 is observed after machining. Chemical composition of Incoloy-800 has changed after EDM machining and amount of carbon percentage has increased in Incoloy-800 machined using all three electrodes which would probably increase brittle nature of the material. Less amount of increase in carbon percentage was observed in material machined using graphite electrode