Effect of multi-walled carbon nanotubes on the performance evaluation of nickel-based super-alloy–Udimet 720 machined using WEDM process

The diverse capabilities of nickel-based super-alloy (Udimet 720), like robust mechanical strength, ductility, resistance to excessive temperature deformation, and advanced corrosion and oxidation resistance, make it suitable for use in multiple applications. These super-alloys are identified as extremely difficult materials for machining to meet feature and manufacturing requirements. In the present work, we demonstrated the machining of Udimet 720 by employing the wire-electrical discharge machining (WEDM) technique. Pulse-on-time (Ton), pulse-off-time (Toff), current, and MWCNT amount were preferred as input variables. The effect of selected design variables was studied on material removal rate (MRR), surface roughness (SR), and recast layer thickness (RLT). Box-Behnken design was utilized to design an experimental matrix. For statistical analysis, analysis of variance (ANOVA) was employed. From ANOVA, the current had the highest contributor with 35.85% to affect MRR, while MWCNT amount was found to be the highest contributor for deciding the values of both SR and RLT with contributions of 42.66% and 40.07%, respectively. The addition of MWCNT at 1 g/L has substantially improved MRR from 0.8546 to 1.2199 g/min, SR reduced from 5.88 µm to 2.98 µm, and reduction in RLT from 17.8 to 11.61 µm. The passing vehicle search (PVS) algorithm was implemented, and the results of single-objective optimization presented the largest MRR of 1.8883 g/min, least SR of 1.89 µm, and least RLT of 9.70 µm. Additionally, a set of non-dominated solutions was obtained through Pareto optimal fronts. A small acceptable deviation was detected among the actual and forecasted results from PVS algorithm. It clearly reveals the acceptance of the PVS technique in the present study for Udimet 720. Lastly, the significance of MWCNT amount on surface textures was revealed by employing scanning electron microscopy (SEM).