Directional microstructure and microhardness evolution in wire arc additive manufacturing of Inconel 625

Inconel 625 has wide industrial uses in energy, aeronautical and marine engineering due to its superior mechanical properties, corrosion resistance and capability to operate in adverse conditions. This study investigates the directional distribution and quantification of Laves and NbC phases in wire arc additive manufacturing (WAAM)-fabricated Inconel 625 using a novel combination of image segmentation, XRD peak normalisation and SEM-EDAX mapping. Anisotropic phase segregation was systematically analyzed across X-, Y- and Z-axes. Results show that Laves phases concentrate along Z-axis, potentially inducing brittleness while NbC phases are more homogeneously distributed, enhancing mechanical strength—particularly in Y-direction. Microhardness measurements confirm highest hardness along Z-axis, attributed to rapid cooling and fine grain structure. High relative density with minimal porosity was also confirmed. These findings offer new insight into solidification behaviour and anisotropic microstructure in WAAM components, highlighting key directions for process optimisation.