Residual stress analysis of butt welds made of additive an tradionally manufactured 316L stainless steel plates

Abstract

Due to the limited building volume of powder bed additive manufactured (AM) methods, combining several AM parts for a larger part through a welding joint may be required. Through AM processes, Laser powder bed fusion (LPBF) has a great potential because it enables the production of nearly fulldensity components. But the residual stresses are still an issue in the wide application of this method. In this study residual stress analysis of butt joints made of 316L AM steel plates compared to conventional rolled steel plates were performed by X-ray diffraction with two different analysis methods: The commonly used sin² psi-method and the comparably new cos alpha-method. Complex residual stress states were determined at the welds made of AM steel plates compared to the welds made of conventional steel plates. High tensile residual stresses were determined in the AM plates depending on the layer orientation, but high compressive residual stresses were measured in the rolled steel plates. However, the residual stress level in the heat affected zone (HAZ) of the weld was comparably low in the AM steel plates and similar to the welds made of rolled steel plates. The residual stress analysis with the cos alpha-method showed the advantage of the comparable short measurement time based on small radiation time compared to the conventional sin² psi-method. A high influence of the layer orientation and manufacturing process was determined on the residual stress state at the base material. Close to the weld, relatively small differences in residual stress state between the investigated conditions were measured by both methods.