Surface morphology and drilling characteristics of nitronic 50 alloy under varying micro-EDM parameters

Abstract Nitronic 50, a high-strength austenitic stainless steel, is micro-drilled in this study. The effects of three critical process parameters—Pulse on Time, Pulse off Time, and Power—on performance metrics such as Material Removal Rate (MRR), Surface Roughness (SR), Circularity (CR), and Taper Ratio (TR) are examined. With an ideal power range needed to preserve process stability, experimental data show that MRR rises with longer pulse on and off periods because of greater energy transfer and debris removal, respectively. By increasing pulse on time and optimising pulse off time for proper flushing, circularity improves while maintaining accuracy. Longer pulse durations tend to cause crater formation, which increases surface roughness; on the other hand, longer off times help cool and eject machined, which decreases surface roughness. Extended pulse on time causes the taper ratio to drop, whilst excessive pulse off time causes it to increase. Optical microscopy shows that hole damage, such as burrs and deformation, is mostly caused by drill wandering and thermal-mechanical stress. Misalignment is linked to entry-side flaws, whereas thrust and thermal softening are responsible for exit-side damage. For high-quality hole manufacturing in Nitronic 50, a balanced parameter selection is essential. For surface roughness, pulse off time was the most significant factor which contributed 64.78%. The f-value for the same is 21.88 which confirm the significance. Pulse on time also had a substantial effect 31.62% with F-value of 10.68. Power was the least dominating factor of 0.63% and it has lower f-value of 0.21. The experimental error was only 2.97% which indicates the reliability of the experiments.For MRR, circularity and taper ratio pulse on time was the dominant factor with the contribution of 54.29%, 85.367%, and 56.86%. These contributions indicate that the pulse on time is a critical factor for achieving efficiency in the micro drilling process. Pulse off time has a contribution of 42.85%, 11.47%, and 27.45%, for MRR, circularity and taper ratio. Power is the least factor in all the experiment outcomes. The percentage improvement in material removal rate (MRR) was improved by 12%, circularity, and taper ratio was decreased by 8% was achieved at the optimal parameter combination, compared with the baseline (initial) setting. The optimal levels of pulse-on time, pulse-off time, power, and other factors identified from the analysis.