Surface Integrity Evolution in WEDM of Nickel-Based Superalloys: Formation and Implications of Recast Layer, Residual Stresses, and Microhardness—A Critical Review

Gurnam Singh; Neel Kanth Grover; Vivek Aggarwal

doi:10.55003/ETH.430401

Authors

Gurnam Singh IK Gujral Punjab Technical University, India
Neel Kanth Grover IK Gujral Punjab Technical University, India
Vivek Aggarwal IK Gujral Punjab Technical University, India

DOI:

https://doi.org/10.55003/ETH.430401

Keywords:

WEDM, Nickel-based superalloys, Recast layer, Surface integrity, Residual stress, Microhardness

Abstract

Wire Electrical Discharge Machining (WEDM) is widely applied for machining nickel-based superalloys used in aerospace and high-temperature systems; however, thermally induced surface alterations strongly affect structural reliability. This review synthesizes recast layer thickness (RLT), microhardness evolution, residual stress development, and elemental redistribution in precipitation- and solid-solution-strengthened alloys. Discharge energy—mainly governed by pulse-on time and peak current and influenced by gap voltage—controls melt-pool behavior, resolidification, chemical modification, and stress evolution. Reported RLT values vary from ~1 to 50 µm depending on machining regime, while low-energy multi-trim strategies can restrict thickness below ~5–6 µm for aerospace requirements. High discharge energy promotes Cu–Zn electrode transfer, oxygen incorporation, and tensile residual stresses (~200–800 MPa), increasing crack susceptibility. Microhardness response is alloy-dependent, often showing subsurface softening under aggressive conditions. This review establishes an energy–microstructure–performance framework for improving surface integrity in critical applications.

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