Unravelling the analysis of electrical discharge machining process parameters, microstructural morphology, surface integrity, recast layer formation, and material properties: A comparative study of aluminum, brass, and Inconel 617 materials

Abstract

Inadequate research regarding how material characteristics affect vital yield parameters in EDM, particularly for aluminium, brass, and Inconel 617. An limited study has examined how EDM process parameters like peak current (Ip), gap voltage, and pulse on time (Ton) affect recast layer thickness, tool wear rate, surface roughness, crack density, globule formation, material removal rate, and crater formation. The interaction between thermal conductivity, microcracks, and recast layers in EDM is uncertain. Material characteristics' implications on XRD patterns and globule formation during EDM machining were not extensively investigated. EDM process parameters and their impacts on response variables such tool wear rate (TWR), material removal rate (MRR), surface roughness, and globule formation for diverse materials have received minimal analysis. In addition, non-ferrous workpiece materials are integral to the electrical discharge machining process. This study delves into how the physical properties of materials influence key yield parameters, including tool wear rate, surface roughness, crack density, globules, material removal rate, and crater formation. The investigation covers Inconel 617, brass, and aluminum, revealing peak current (Ip) as the most influential factor for highly thermally conductive materials when compared to gap voltage and pulse on time (Ton). Notably, Inconel 617 exhibits longer cracks, while aluminum displays smaller ones, and deeper cracks are found on the surface of aluminum, contrasting with the broader craters observed on Inconel 617. Recast layer thickness varies, ranging from 8.3 μm for brass to 13.8 μm for aluminum. The study validates response values extensively against experimental data and highlights brass's superior surface finish. It further uncovers that plasma-generated craters are predominantly semispherical, with the plasma's diameter expanding faster than the crater's size. Sub-surface re-solidification emerges as a source of stress and micro-cracks, which diminish material's fatigue strength. Notably, aluminum exhibits a greater number of elegant microcracks on the machined surface, while brass and Inconel 617 have fewer. Recast layer thickness measurements indicate approximately 13.8 μm for aluminum, 8.3 μm for brass, and 9 μm for Inconel 617. Additionally, the thermal erosion process enhances the microhardness of the machining zone's subsurface due to the formation of oxides and carbides and the re-solidification of particles. Different material characteristics are revealed through X-ray diffraction (XRD) patterns, while globules, small and spherical, weakly adhere to the machining zone's subsurface. In particular, aluminum machined surfaces feature fewer globules, while brass surfaces exhibit a higher quantity, attributed to their varying thermal conductivity. © 2023 The Authors