An in-depth analysis of MWCNTs and graphene nanofluids-based EDM: Investigating surface integrity in Inconel 825 superalloy

The current study systematically explores the potential of nanofluids (NFs) as dielectric media in EDM to enhance the surface integrity of Inconel 825. To achieve this objective, applying nanofluids involves ensuring uniform dispersion of nanoparticles, specifically emphasising efficient heat dissipation, thereby aligning EDM processes. This investigation focuses on utilising MWCNTs NFs, graphene NFs, and hybrid NFs (maintaining a 1:1 ratio of nanoparticles) with a hydrocarbon-based EDM oil as the base fluid. This study marks a pioneering attempt to implement these NFs in the EDM process for Inconel 825. Comprehensive characterizations of NFs have been conducted before their application in the EDM process. These have included assessments of hydrodynamic diameter, zeta potential, dynamic viscosity, thermal conductivity, and breakdown voltage. A comparative analysis has been performed between the outcomes of NFs-based EDM and conventional EDM (using EDM oil). The results show that using graphene NFs, followed by MWCNTs NFs and hybrid NFs, improves thermal conductivity and stability during the EDM process. This results in an enhanced material removal rate and better surface roughness. In-depth examinations of surface irregularities, surface microcracks, recast layer thickness, and grain orientation are carried out using scanning electron microscopy and electron backscattered diffraction. Moreover, residual stress and microhardness are systematically determined to gain further insights into surface integrity. The results indicate that the comparatively higher dispersion of graphene within base dielectric fluid provided better surface integrity for ED-machined parts.