Machinability investigation and surface modification of nano-TiB2 and AlN grafted MWCNT hybridized Al 7075 matrix ternary composite through powder-mixed EDM

Abstract

This paper accentuates powder-mixed electrical discharge machining (EDM) performance of a newly designed nano-TiB2 and AlN grafted multiwall carbon nano-tube (MWCNT) hybridized Al 7075 matrix ternary composite. The hybrid metal matrix composite (MMC) was fabricated through squeeze casting route, preceded by two-stage reinforcement addition, mechanical agitation, and ultrasonic treatment. EDM was carried out using cryogenic treated Cu electrode and Al2O3 particle-mixed dielectric medium. Influence of EDM process variables, that is, peak current ( I P), pulse-on time ( T ON), and powder concentration ( P C) on machinability of the hybrid MMC was studied considering material removal rate (MRR), tool wear rate (TWR), and average surface roughness ( Ra) as quality indicators. Effects of machining and Al2O3 particle addition on surface morphology of the hybrid MMC were also explored through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and elemental mapping. Results reveal elevation of MRR, reduction of TWR and improvement of surface finish during powder-mixed EDM in comparison to the non-mixed (conventional) EDM. Maximum traces of Al2O3 particle deposition was identified on the machined surfaces while using the powder concentration of 1.5 g/l within the dielectric.