Residual stress mapping of additively manufactured Inconel 718 via synchrotron X-ray diffraction

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Abstract
Laser Powder Bed Fusion (LPBF) of Inconel 718 induces complex residual stresses that can lead to premature failure. This study investigates the residual stress field of an as-built plate using high-energy synchrotron X-ray diffraction. Cross-verification of peak-fitting algorithms demonstrated that the Pseudo-Voigt function was marginally more accurate, with peak-fitting-related uncertainties in stress calculation remaining below 15.3 MPa. The reconstructed field reveals an anisotropic “core compression, edge tension” pattern, dominated by longitudinal stresses. This pattern is fundamentally driven by the temperature gradient mechanism: constrained thermal expansion during heating induces compressive plastic deformation, which reverses to severe tension during constrained cooling shrinkage. This cycle imparts alternating downward ‘push’ and upward ‘pull’ bending moments at the edges. Ultimately, critical tensile stresses concentrate at lateral edges (reaching 791 MPa), resulting in macroscopic self-equilibration with a compressive core (-355 MPa). These insights can guide the optimization of scanning strategies to mitigate residual-stress-induced failures in additively manufactured components.

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