Comparative residual stress analysis on a DED-Arc manufactured high-strength steel component using the contour method and XRD

Abstract Lightweight construction is a vital approach for reducing CO₂ emissions, as it contributes to the development of more energy-efficient structures and supports the overall goal of achieving carbon neutrality in the transition to sustainable manufacturing. Though, a topology-optimized design often leads to complex geometries. Additive manufacturing (AM) processes such as direct energy deposition with arc (DED-Arc) offer great design freedom due to the buildup of components in layers. Furthermore, DED-Arc enables efficient production due to the high deposition rate, process reliability, and good automation capability. Further efficiency can be achieved through weight optimization, enabled by high-strength steels. However, a major challenge is the process-induced residual stresses (RS) in the component, which arise primarily due to restrained shrinkage. High tensile residual stresses are detrimental as they increase the risk for several types of cracking and failures. Knowledge of residual stress distribution is crucial for predicting the service life of the component and structural integrity assessment, especially for safety-critical applications. Therefore, this study focuses on the use of the contour method (CM) to analyze the full field longitudinal residual stresses in an open hollow cuboid component (dimensions, 120 × 50 × 30 mm 3 ) manufactured by DED-Arc (low-alloyed high-strength steel with yield strength > 730 MPa). In CM, the component is cut along a desired plane of interest, and the contour of the deformed cut surface is measured. A finite element model is used to reconstruct the residual stresses field in the 2-dimensional plane of cut. In this paper, a modified cutting strategy was employed. After cutting, the deformed cut surfaces were measured utilizing two surface measurement techniques, i.e., coordinate measuring machine (CMM) and a 3D scanner. The accuracy of the CM was validated against surface stresses measured using X-ray diffraction (XRD). Additionally, a comparison of neutron diffraction experiments was conducted. The residual stresses were further correlated with hardness measurements. The results from surface measurement techniques showed good qualitative and quantitative agreement regarding the measured displacement contour. CM results revealed peak stresses in the DED-Arc walls; bending deformation in the substrate induces tensile stresses at the bottom of the substrate plate and compressive stresses in the middle top region. The residual stresses obtained from diffraction and CM showed a good agreement and correlated qualitatively with the hardness measurements. These results show that practical residual stress mapping and quantification using XRD accompanied by minimal application of CM for values in the bulk are suitable for identifying and minimizing detrimental welding-induced stresses in such high-strength AM lightweight components, even without the use of expensive methods such as neutron diffraction.