Performance enhancement of electrochemical discharge micromachining of borosilicate glass using nitrogen gas assistance

Electrochemical Discharge Micro-Machining (ECDµM) of borosilicate glass commonly suffers from unstable discharges, surface cracking, low material removal (MR), and excessive tool wear (TW) when conventional liquid or air-based dielectrics are used. These issues limit machining efficiency and sustainable process development, especially when MR and TW are optimized independently. To overcome these limitations, this study investigates nitrogen gas as a regulated gaseous dielectric in combination with an aqueous sodium hydroxide (NaOH) electrolyte to enhance discharge stability and achieve balanced machining performance. Experiments were conducted by varying applied voltage, NaOH concentration and nitrogen gas flow rate, and the responses were analyzed using Response Surface Methodology (RSM), Grey Relational Analysis (GRA), and a Random Forest Algorithm (RFA). Stable machining was achieved within a nitrogen gas flow range of 3–5 L/min. At 120 V and 30 wt% NaOH, increasing the nitrogen gas flow rate from 3 to 5 L/min maintained MR at 4 mg while reducing TW from 3 to 2 mg. The optimal condition (134 V, 20 wt% NaOH, 4 L/min nitrogen gas flow rate) yielded 5 mg MR with negative TW (− 1 mg), while reducing electrolyte concentration by 33%. The Random Forest model predicted near-optimal parameters (119.89 V, 20.107 wt% NaOH, 4.31 L/min) with an average deviation of approximately 8%. These results establish nitrogen gas assisted ECDµM as a stable, energy-efficient and environmentally responsible approach for precision micromachining of brittle materials.