Revealing 3D strain and carbide architectures in additively manufactured Ni superalloys

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Abstract
Laser Additive Manufacturing (LAM)-induced directional solidification creates complex microstructures in nickel-based superalloys, featuring columnar grains with cellular sub-grains and carbides. Using Scanning 3D X-ray Diffraction (S3DXRD), we reveal orientation and intergranular strain relationships coupled to cellular sub-grain networks and primary cubic MC carbides. We analyzed 3D orientation and elastic strain fields across 82 γ grains and 37,000+ carbides in an ABD-900AM alloy produced via Directed Energy Deposition (DED). Cooling-induced solute segregation creates volumetric lattice parameter patterning in the γ phase, altering residual stress fields. Ti-, Ta-, and Nb-rich carbides form preferentially in these high-solute regions, exhibiting weak orientation relationships with parent γ grains. These results provide the first non-destructive 3D study linking rapid solidification segregation, deformation heterogeneity, and carbide architectures in additively manufactured Ni-superalloys. These insights provide crucial detail to rationalise LAM process parameter optimisation and the coupled spatially governed structural performance.

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