Statistical modeling and multi response optimization of wire electrical discharge machining of Haynes 230 with validation through microstructural characterization

Haynes 230, a high-temperature Ni–Cr–W–Mo superalloy valued for its oxidation resistance and thermal stability, exhibits severe deformation-induced hardening and tool wear during conventional machining. However, the machinability of this specific alloy under wire electrical discharge machining regimes remains largely uninvestigated. This study establishes a comprehensive response surface framework to systematically evaluate the independent and interactive influences of pulse-on time (On-Tp), pulse-off time (Off-Tp), peak current (Ip), spark-gap voltage (GVs), wire feed rate (FRw), and wire tension (Tw) on cutting rate (CR) and surface roughness (SR). ANOVA identified GVs and On-Tp as the primary governing factors dictating plasma channel dynamics. Multi-response desirability optimization successfully established an equilibrium processing window, yielding a validated, stable performance of CR = 1.80 mm/min and SR = 1.66 μm. Subsurface integrity is highly sensitive to variations in discharge energy density. The recast layer thickness altered from 10.6 μm under CR-optimized conditions to 2.4 μm under SR-optimized conditions, and was restricted to 4.85 μm within the multi-response optimized window. Characterization of the machined surface confirmed significant element partitioning within this zone, featuring the depletion of matrix constituents (Ni, Cr, Co), the relative enrichment of heavy refractory elements (W, Mo), and the interstitial infusion of oxygen and zinc due to dielectric decomposition and tool-electrode transfer. Composite microhardness increased from a bulk matrix baseline of 427–534 HV within high-energy zones, driven by ultra-rapid solidification rates, micro-segregation of secondary phases, and severe quench-induced strengthening. Ultimately, this work correlates validated macroscopic input boundaries with process-induced metallurgical evolution to establish an optimized, high-integrity manufacturing framework for critical aerospace components.