Electro-thermal surface evolution in EDM of dissimilar stainless-carbon steel welds: parametric effects and micro-texture correlations.

This study investigates surface formation during Electrical Discharge Machining (EDM) of dissimilar stainless-carbon steel welded joints fabricated by Tungsten Inert Gas (TIG) and Manual Metal Arc (ARC) welding using 316 and 309 filler metals. Experiments were conducted at gap voltages of 10-40 V, pulse-on times of 7-11 µs, and pulse-off times of 10-14 µs. The machined surfaces were characterized through six standardized roughness descriptors (Ra, Rq, Rt, Rz, Rsk, Rku) to capture amplitude and statistical texture features. TIG316 exhibited the smoothest and most stable morphology (Ra ≈ 1.6-2.0 μm), reflecting efficient heat dissipation and uniform plasma confinement, whereas TIG309 showed nonlinear roughness behavior that stabilized only at optimized pulse durations. ARC316 maintained moderate roughness with limited variation, whereas ARC309 deteriorated with excessive energy input due to thermal accumulation and recast-layer thickening. A dimensionless electro-thermal energy-density parameter ([Formula: see text]), obtained using common dataset-level min-max normalization, unified the effects of voltage and pulse timing, revealing that the lowest measured roughness occurred at [Formula: see text] = 0.023, 0.524, 0.438, and 0.000 for TIG316, TIG309, ARC316, and ARC309, respectively. The results establish a physics-based correlation between discharge energy and surface integrity and support weld-specific optimization of EDM processes in heterogeneous welded systems.