Performance analysis of copper and brass tools in micro-hole drilling of SuperNi 276 using electrical discharge drilling

SuperNi 276 is highly valued for its exceptional corrosion resistance and high-temperature performance, making it a critical material in the aerospace and power generation industries. However, fabricating precise micro-holes in this alloy poses challenges with conventional machining techniques. This study explores the use of electro discharge drilling (EDD) to produce high-quality micro-holes in SuperNi 276. Output parameters, including tool wear rate (TWR) and material removal rate (MRR), were measured by varying input factors such as pulse on time, pulse off time, and peak current, using tool diameters 0.5 mm, 0.6 mm, 0.7 mm, and 0.8 mm while maintaining a constant voltage of 2 V. The elemental composition of the recast layer and heat-affected zone (HAZ) was analyzed with energy-dispersive X-ray spectroscopy (EDS). Copper tools in EDD of SuperNi 276 achieve a higher maximum MRR of 0.115938 mm³/s but show significant tool wear with a TWR of up to 0.7391 mm/s. Brass tools, however, exhibit minimal TWR at 0.0026 mm/s, making them ideal for applications requiring longer tool life. Though the maximum MRR for brass is moderate at 0.065940 mm³/s, it offers a balance between efficient machining and reduced wear. Post-EDD, the thickness of the recast layer and HAZ were analyzed. Experimental results indicate that the copper tool exhibits a thinner recast layer and HAZ due to its high thermal conductivity. Microhardness testing showed that brass tools increase the hardness of the recast layer and minimize the HAZ due to superior heat dissipation, resulting in improved material integrity. This study also shows that brass tools maintain a composition similar to the base material, especially in the HAZ, with 58.0% Ni, showing optimal results, and balanced Cr, Mo, W, and Fe levels. Brass tools, under specific configurations, ensure consistent machining and material integrity with minimal wear.