Development and Application of Aluminium CNT Composite Electrode for Electro Discharge Machining

Abstract

Aluminium Metal Matrix Composites (Al-MMCs) are widely utilized in industry. This thesis presents a novel multistage ball milling (MSBM) technique for fabricating Al-MMCs via powder metallurgy (PM), incorporating 5 wt. % copper (Cu) and 0.5 1.5 vol. % CNTs. The five samples named as PM-Al, PM-Al-5Cu, PM-Al-5Cu-0.5 CNT, PM-Al-5Cu-1.0 CNT, PM-Al-5Cu-1.5CNT were prepared twice by conventional single-stage ball milling (SSBM) and new MSBM technique. The MSBM approach utilizes sequential mixing at different milling speeds to optimize CNT distribution and reduce structural degradation. Comparative analysis against SSBM revealed that the MSBM-processed Al-5Cu-0.5CNT composite exhibited superior electrical conductivity, thermal conductivity, and hardness. The developed MSBM processed Al composites are applied as electrode for the surface modification of Inconel 718 using Electro-Discharge Machining (EDM). Compared to cast copper electrodes, PM processed CNT reinforced Al-MMC electrodes achieved higher material transfer to the workpiece and notable changes in Inconel s surface composition, including increased deposition of Al, Cu, and Carbon (C), alongside reduced Nickel (Ni), Ferrous(Fe), and Chromium (Cr) content. Surface hardness improved maximum with the PM-Al-5Cu-1.5CNT electrode, while the PM-Al-5Cu-0.5CNT electrode yielded the best surface finish. The process capability analysis of PM processed Al, Al-Cu and Al-Cu-CNT EDM electrodes were done with newly developed univariate index (AI, Adev, Ca). Material removal rate (MRR), tool wear rate (TWR) and post EDM hardness were analyzed and compared with conventionally used Cast-Al and Cast-Cu electrodes. It was observed that among PM processed electrode Al-Cu was suitable for highest MRR, Al-Cu-0.5 CNT was suitable for lowest TWR, and all electrodes met specification limits for post EDM hardness. newline newline