Characteristics of residual stress distribution in wire-arc additive manufactured layers of low transformation temperature material

High heat input in wire and arc additive manufacturing (WAAM) tends to result in high tensile residual stress, which adversely affects performance and service reliability. However, low-transformation-temperature (LTT) materials are susceptible to compressive residual stresses due to their low phase-transformation point. Here, the LTT material 10Cr10Ni was used as the deposited material to fabricate a pipe structure, and the contour method was applied to measure the residual stress distribution in the cross-section. A thermomechanical coupling analysis model was developed to investigate the residual stress generation mechanism in 10Cr-10Ni(LTT) during the WAAM process. The simulated deformation and residual stress distributions agree well with the measurements. Through simulation analysis of the deposition of different layers, we found the key to the generation of compressive residual stresses in the LTT layers lies in whether there is a transformation from austenite to martensite during the final thermal cycle. When the deposition height exceeded 5.405 mm (approximately four layers), compressive residual stresses were only generated in the last four LTT layers and transformed into tensile residual stresses in the other layers. This results in a concept called the effective region, which can be used as a guide for reducing stress in WAAM using LTT materials.