Residual stress determination in additively manufactured steels under different composition ratios and processing states

Abstract This study investigates the influence of varying compositional ratios of 316 L and 17-4PH stainless steel in functionally graded materials (FGM) on the microstructure and residual stress states of components produced by Laser-Directed Energy Deposition (DED-LB). Samples were fabricated under constant process conditions and analyzed in three conditions: as-built, stress-relieved, and mechanically treated by deep rolling. The individual alloys grew in columnar, needle-like grains, while the use of mixed compositions resulted in more homogeneous microstructures. X-ray diffraction revealed a dominant face-centered cubic (fcc) phase up to 60 wt% 17-4PH; higher ratios led to increased body-centered cubic (bcc) phase fractions due to ferrite-forming elements. Residual stresses were measured using the sin²ψ method. Annealing reduced the tensile stresses, while deep rolling induced compressive stresses up to − 300 MPa perpendicular to the additive manufacturing scanning direction. As the 17-4PH content increased, the variation in the residual stress values between processing states decreased. The results demonstrate that both material composition and post-processing have a significant effect on the resulting microstructure and residual stress state of DED-LB components.