Wire arc additive manufacturing of Inconel 625: A review

Abstract

Wire arc additive manufacturing (WAAM) enables economical near-net-shape production of large Alloy 625 components, but repeated arc-heating cycles create location-dependent microstructures and properties. This critical narrative review synthesizes 2020–2026 evidence through a process–thermal history–microstructure– performance framework, emphasizing deposition mode, interpass control, segregation, defects, post-deposition heat treatment and mechanical/environmental response. The literature consistently reports a textured γ-Ni dendritic matrix with Nb–Mo enrichment and interdendritic constituents in the as-deposited condition. Low-heat-input, interrupted and field-assisted strategies can refine microstructure and improve selected tensile or wear outcomes, whereas uncontrolled heat accumulation increases heterogeneity. Solution treatment can dissolve Nb-rich constituents, while ageing may strengthen through precipitation; neither provides a universal benefit because grain growth, phase evolution and cooling route create competing effects. Cross-study comparison remains limited by inconsistent heat-input conventions, sparse thermal histories, non-uniform coupon extraction and insufficient fatigue, creep and service-environment data. The distinctive contribution is an evidence hierarchy, a condition-aware quantitative synthesis, an evidence-linked gap matrix and a minimum reporting framework for qualification-oriented research. Reliable WAAM Alloy 625 therefore requires control and reporting of the entire thermal trajectory rather than optimization of isolated welding parameters.