Experimental investigations of using MWCNTs and nano-graphene particles for the enhancement of machining performance using powder-mixed EDM of Udimet-720

In this study, powder-mixed electrical discharge machining (PMEDM) was employed using two carbon-based nanopowders (multi-walled carbon nanotubes (MWCNTs) and nano-graphene) to enhance the machining characteristics of Udimet-720. Pulse-on-time, pulse-off-time, and current were selected as control variables, with material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) as output responses. Taguchi’s L9 design was utilized to conduct experimental trials. Empirical models were generated, and the output responses were optimized using the heat-transfer search algorithm technique. An objective function was formulated for simultaneous optimization, and the obtained solution was utilized to investigate the influence of carbon-based nanopowders (MWCNTs and nano-graphene). Results of simultaneous optimization have given the optimal parameter settings at T_on of 4 µs, T_off of 3 µs, and current of 18 A with optimal response values of MRR at 26.22 mg/min, TWR at 0.4759 mg/min, and SR at 5.91 μm. Under the same machining conditions, nano-graphene-based EDM at a 1 g/L concentration has yielded higher MRR and the lowest TWR and SR compared to MWCNTs-based EDM and conventional EDM. The machined surfaces were also investigated for surface defects through scanning electron microscopy. The surface defects, in terms of the formation of globules and micro-pores, were observed to be less pronounced for the use of graphene powder than for MWCNTs. The authors believe that the present work will be useful for machining hard materials, which are widely used in aeronautical applications.