Evaluating the Feasibility of Using Biodegradable Castor Oil as a Dielectric Medium during Micro-Electrical Discharge Machining of Inconel 718

Two dielectric fluids, namely hydrocarbon (HC)-based mineral oils and water-based dielectrics, are generally used during the micro-electro-discharge machining (micro-EDM) process. However, mineral oils often endanger health and safety risks to the operator and ecology. In contrast, the machining accuracy gets compromised using water-based dielectrics due to uncontrolled electrochemical dissolution. Therefore, concerted research efforts have been made to find an alternative, sustainable dielectric based on vegetable oils. In this context, the feasibility of using castor oil as a dielectric fluid during a milling variant of the micro-EDM process is evaluated. Further, its performance as a dielectric is assessed to that of EDM oil and deionized (DI) water for corresponding parametric settings. The material removal rate (MRR), surface roughness (SR), and width-over-cut (WOC) are considered the performance characteristics. The pulse current and pulse on/off periods are varied. Also, surface analysis is conducted using the optical interferometer and scanning electron microscope (SEM). The results revealed that castor oil rendered the highest MRR and SR and the least WOC among all three dielectrics for corresponding parametric settings.