Surface Alteration of Al-7075 Alloy by Depositing Inconel 718 through Electrical Discharge Coating

The study aims to modify Al-7075 alloy surface by depositing Inconel 718 (IN718) through electrical discharge coating (EDC) process. Tool electrodes composed of 70% IN718-30% Al were prepared by powder metallurgy process by compacting them at different loads. Current and pulse on-time were altered during EDC to investigate their effects on the responses such as material transfer rate (MTR), tool wear rate (TWR) and surface roughness (Ra). A single index named overall evaluation criteria (OEC) was formulated to optimize the process parameters for higher MTR, TWR and lower Ra. Analysis of variance was implemented to find the importance of the parameters on the responses. Confirmation test was conducted at optimum condition of OEC, which resulted in 0.82% deviation in the experimental and predicted results. The layer thickness of the coatings was measured by visualizing the etched cross sections under microscope. The topography of the coatings, characterized by SEM, revealed the presence of globules, craters, cracks and redeposition layers. XRD and EDX analyses were used to authenticate the material migration from the tool to the work surface. Microhardness testing revealed a threefold enhancement in the coating surface compared to the base material, justifying the use of IN718 as a coating material.