Comparison in the performance of EDM and NPMEDM using Al2O3 nanopowder as an impurity in DI water dielectric

Abstract

In this paper, an attempt is made to explore the possibilities of modifying the dielectric by adding alumina (Al2O3) nanopowder for improving the machining performances. The performance of newly developed nano powder-mixed electrical discharge machining (NPMEDM) process is compared with conventional EDM. Peak current, gap voltage and pulse-on time are taken as considerable process parameters to investigate material removal rate (MRR), surface roughness (SR), recast layer thickness, surface morphology, surface topography and induced residual stress. It is observed that the nanopowder-mixed dielectric medium gives better surface finish and higher metal removal rate as compared to conventional dielectric. The value of MRR increases from 32.75 to 47\xa0mg/min and surface roughness improves from 2.245 to 1.487\xa0μm. Thereafter, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) investigation of the machined surface reveals that presence of micro-crack, micro-hole and uneven deposition decrease substantially during NPMEDM process. Also, induced tensile residual stress on the machined surface significantly reduces in this modified process. Further, the basic mechanism of these processes are investigated by analysing pulse train discharge waveforms and reveals the better sparking stability of NPMEDM process, which results in the higher MRR and better surface quality.