Optimization of electrical discharge drilling parameters for precision micro-holes in SuperNi 276

Abstract

This study focuses on optimizing Electrical Discharge Drilling (EDD) parameters to enhance micro-hole precision in Super Ni 276, a nickel-chromium-molybdenum alloy valued for its corrosion resistance and temperature stability. The Taguchi fractional factorial method with an L16 orthogonal array is used to evaluate the influence of four key EDD parameters: tool diameter, peak current, pulse on time, and pulse off time. Micro-holes of 0.5 mm, 0.6 mm, 0.7 mm, and 0.8 mm diameters are drilled using copper and brass tube tools under constant voltage. The study analyzes material removal rate (MRR), tool wear rate (TWR), recast layer thickness, heat-affected zone (HAZ), and microhardness to determine the optimal tool material. Copper tools achieve a high MRR of 0.115938 mm³ /sec but show significant tool wear with a TWR of 0.7391 mm/sec. Brass tools, with a lower TWR of 0.0026 mm/sec, are suitable for longer tool life, though their maximum MRR is moderate at 0.065940 mm³ /sec, balancing efficient machining and wear. Copper tools produce thinner recast layers, enhancing surface quality, while brass tools create a larger HAZ due to higher heat generation. Copper tools yield higher recast layer hardness, ensuring surface durability and acceptable HAZ hardness, preserving base material integrity. Copper is ideal for high MRR and minimal thermal damage, while brass suits longer tool life and higher hardness across zones.