Parametric Investigation into Alumina Nanopowder Mixed EDM of Inconel 825 Alloy Using RSM

Nanopowder mixed electrical discharge machining (NPMEDM) is a recent development in the non-traditional machining process. In this process, addition of powder into dielectric increases the spark gap between the electrodes resulting in more number of low intense sparks. Therefore, both the material removal rate (MRR) and surface finish improve. The present work investigates the effect of Al₂O₃ nanopowder mixed EDM oil on various responses like MRR and surface roughness (SR). The Al₂O₃ nanopowder is mixed with EDM oil at a concentration of 0.5 g/L. Pulse duration (T_on), peak current (IP) and gap voltage (GV) are taken as the process parameters. The experiment is designed using response surface methodology (RSM), where two sets of experiments have been conducted using two different dielectric conditions (i.e. EDM oil and powder mixed in EDM oil). Analysis of variance (ANOVA) shows that all the three selected parameters are significant for MRR and SR. The study shows that there is considerable increase in MRR and reduction in SR after mixing Al₂O₃ nanopowder in EDM oil. Using field emission scanning electron microscope (FESEM), a detailed study on the surface integrity of the machined surface has been carried out. It has been found that NPMEDM reduced microcracks, microholes, uneven deposit and recast layer thickness of the machined surface to a great extent.