Performance of dielectric media (conventional EDM oil and distilled water) during machining of Inconel 825 super alloy

Abstract

Abstract In the present research work, performance of dielectric media (conventional EDM oil and distilled water) is studied in the context of machinability of Inconel 825 during electro-discharge machining. In this work, machinability is evaluated in purview of material removal efficiency, tool wear rate, and surface integrity of the machined specimen. Study of surface integrity includes morphological study as well as analysis of topographical measures like surface roughness, surface crack density, white layer thickness, foreign material migration, metallurgical characterization along with phase alteration and precipitation of intermetallic compounds and finally, micro-hardness tests. Experimental results suggest that as compared to EDM oil, distilled water (used as dielectric media) adversely affects the efficiency towards material removal, and promotes formation of rough surface. An important observation is that when EDM oil is used as dielectric media, carbide formation is attributed to the machined surface due to pyrolysis of hydro-carbon. While in case of distilled water, its decomposition causes oxide formation at the machined surface instead of carbides. Moreover, it is observed that peak discharge current imposes positive effect on both surface crack density, and white layer thickness. Microhardness depth profile confirms presence of hardened layer up to certain depth beneath the machined surface followed by gradual truncation, as distance is increased towards interior of the parent material.