EDM machinability and surface characterisation of Al-SiC metal matrix composites: ANOVA based response surface study

In the current work, machinability of an Al/SiC MMC was studied using the EDM process, a non-traditional machining technique used for precision and intricate machining purposes. The Al/SiC MMC was used as the workpiece while brass electrode were used to tool. The main aim was to investigate the effect of process input parameters Peak Current (Ip), Voltage Gap (Vg) and Pulse-on Time (Ton) on machined performance in terms of MRR, TWR and Ra. Central Composite Design (CCD) of Response Surface Methodology under was used to design the experiments and to analyse the results. To determine statistical significance of the input parameters on the response metrics, Analysis of Variance (ANOVA) was applied. The results show that moderate Ip, low Vg and high Ton combination gives better MRR. The optimal TWR reduction is achieved by setting Ip low, Vg high, and Ton low. To obtain good surface finish (low Ra) the best combination is low Ip and high Vg with medium Ton. In addition, the machined surfaces were observed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to analyse material removal mechanisms. Molten globules, micro-cracks and craters which are the typical morphology were observed by SEM arising from thermal damage in the process of cutting of tool. Further, EDS analysis confirmed the nature of oxides in the machining zone and put forth evidence for understanding EDM process on Al-SiC composites.