Experimental investigation on electrochemical discharge machining of hastelloy

Abstract

The study examines the influence of various process parameters on Material Removal Rate (MRR), Tool Wear Rate (TWR) AND Surface Roughness (Ra) during the machining of Hastelloy using Electrical Discharge Machining (EDM) machined under NaOH dielectric medium. Results showed that a 20% NaOH concentration optimizes MRR at 0.889 mm³/min, while higher concentrations lead to process instability due to excessive bubble formation and discharge irregularities. The optimal current of 30 A improves MRR, but excessive melting occurs beyond this level, negatively impacting tool wear and surface finish. A pulse-on time of 45 µs produces the best surface finish of 1.786 µm), while longer pulse durations cause overheating and degrade surface quality. TWR was minimized at a gap distance of 2 mm, which allowed effective cooling and debris removal, reducing wear by 15%. Voltage levels between 12 V and 18 V resulted in the most stable discharges, yielding optimal MRR and Ra values. Lower current values stabilize TWR, while higher currents and longer pulse-on times increase wear. A gap distance of 2 mm minimizes TWR by ensuring effective cooling and debris removal. Optimal surface roughness is achieved with 30 A and 45 µs, where controlled discharges reduce surface imperfections. Higher NaOH concentrations induce rougher textures due to more aggressive sparks. SEM analysis confirms that process parameters significantly impact surface topography, characterized by craters, re-solidified debris, and microcracks. The optimized parameters identified from the results were 20% NaOH concentration, 30 A current, 45 µs pulse-on time, 2 mm gap distance, and voltage of 15 V.