Effect of substrate detachment on residual stress redistribution in DED-Arc manufactured high-strength steel components

Abstract

Abstract Additive manufacturing by DED-Arc enables the production of large and complex high-strength steel components. However, the residual stress state generated during deposition can be significantly altered when the component is separated from the substrate plate as a final manufacturing step. This study investigates the residual stress relaxation and redistribution caused by substrate detachment in DED-Arc manufactured high-strength steel hollow cuboids. The component geometry was varied in terms of height, length, and wall thickness. Longitudinal residual stresses were measured by X-ray diffraction on the side wall surfaces before and after mechanical separation from the substrate plate. In addition, 3D scanning was used to quantify the resulting component distortion. The results show that substrate detachment causes a pronounced redistribution of longitudinal residual stresses, including a reduction of tensile stresses and, in some regions, the formation of compressive residual stresses. The stress differences before and after detachment can be interpreted as a superposition of relaxed longitudinal shrinkage stresses and released bending stresses arising from inhomogeneous restraint over the build height. The sign and magnitude of the bending contribution depend strongly on the component geometry. Low-build and high-build components show opposite bending tendencies after detachment, which is attributed to the interaction between substrate restraint, component stiffness and transformation-affected upper layers. Regression analysis of the geometry variation indicates that height, length, wall thickness, and the height–length interaction significantly affect the released bending stress, while component height is the dominant factor for the normal tensile stress relaxation. The findings demonstrate that substrate detachment is a critical step for residual stress redistribution and distortion in DED-Arc manufactured high-strength steel components and that geometry tailoring is usable to influence the resulting stress state.