Enhancing low-speed WEDM machining capabilities on Nitronic-50 with a constant frequency ultrasonic hybrid method

Abstract

Nitronic-50 stainless steel is a high-strength and corrosion-resistant austenitic premium steel. It requires improved surface characteristics due to its wide use in various applications like fasteners, marine hardware, hydroelectric-power turbines, pressure vessels, etc. This work focuses on machining hard-to-machine Nitronic-50 steel is unconventionally machined using constant frequency ultrasonic-aided low-speed wire electrical discharge machining (USV-LS-WEDM) to enhance its machined surface integrity. This method achieves effective results when cutting high-strength materials with intricate shapes. Material removal rate (MRR) and surface roughness (Ra) were measured by considering inputs such as servo voltage (SV), pulse off time (T_off), pulse on time (T_on) and current (I) with an ultrasonic-vibration range of 20,000 Hz. The appropriate selection and usage of LS-WEDM parameters is a challenging process and is done with parametric analysis. The MRR of Nitronic-50 was enhanced with an increase in T_on and I along with a reduction in T_off and SV. Surface roughness (Ra) decreased with a gradual reduction in T_on, I, and an increase in SV. The USV-WEDM was compared with a stand-alone WEDM indicating that the MRR for USV-WEDM was improved by 12% and the Ra was decreased by 9% due to effective distribution of spark discharges, which increased material erosion and redistribution of molten metal characteristics. Machining quality for hard-to-machine Nitronic-50 steel was certainly enhanced via hybrid ultrasonic vibration with the existing LS-WEDM.