Improvement of Micro-Electrochemical Discharge Machining of Austenitic Stainless Steel 316L using NaOH electrolyte containing N2

Abstract

Micro-Electrochemical discharge machining (μECDM) is a subjective choice in delicate micro machining operations, particularly in Micro-Electromechanical Systems (MEMS) industries for fabricating the microscale devices. Dielectric characteristic of electrolyte is a predominant parameter determining the performance of μECDM. Prevention of surface cracks, heat-affected zone, and surface irregularities on the machined specimen are research challenges that striving to find innovative experimental designs. This research adopts a new experimental setup where Nitrogen gas is introduced in the gap between the tool electrode and workpiece. The experiments were conducted using plain aqueous NaOH and Nitrogen gas assisted aqueous NaOH electrolytes in μECDM of Austenitic stainless steel 316L (SS 316L). Voltage, duty cycle, electrolyte concentration, and Nitrogen gas flow rate were varied to investigate the responses of the machining process namely Material removal rate (MRR) and Tool wear rate (TWR). The dielectric characteristic of the generated gas film has improved the current density across the gap and consequently enhanced the heat transformation from the spark through the discharge and hydrodynamic regimes to the workpiece effectively. Nitrogen gas assisted μECDM has produced MRR of 2.6 mg/min and TWR of 0.8 mg/min at 105V, 70 duty cycle, 15.708 wt% of NaOH electrolyte and 3 lit/min of Nitrogen gas flow. SEM and EDX results have evidenced the minimum surface irregularities which indicates the uniform metal removal on the machined components. The results of the confirmatory experiment reveal that there is about 10% of increase in MRR and 21% of decrease in TWR are achieved from Nitrogen gas assisted machining, compared to plain NaOH electrolyte machining.