Residual stress investigation in additively manufactured samples

In the present study, additively manufactured (AM) samples of different sizes were analysed by the contour method (CM). Builds of three different volumes were examined to determine the influence of residual stress (RS) distribution along the z-axis on volumetric changes in the part. They were made using the direct energy deposition (DED) technique. Only a handful of reports cover the use of CM for finding the RS distribution in DED builds. This study aims to complement those with new findings. The contour method is a destructive technique whose main advantages are the absence of sample size limits and the ability to predict residual stresses at greater depths than other methods. In this study, residual stresses were evaluated in three stainless steel samples (35×35×35 mm, 25×25×25 mm, 15×15×15 mm) prepared by the DED method. Stainless steel 316L powder was blown into a melt pool created by a high energy laser source. The melted powder solidifies as the laser head moves along a predefined path. In order to protect the material from oxidation during deposition, argon is used as a shielding gas-fed continuously to the melt pool. 316L austenitic stainless steel was chosen for this experiment because it undergoes no phase transformations during deposition. This reduces the complexity of the metallurgical processes involved. Evaluation of the sections produced by the contour method was carried out using an optical precision measuring machine (3D scanner) and FE software.