Residual stresses and distortions in austenitic stainless steel 316L specimens manufactured by Selective Laser Melting

Sammanfattning: Residual stresses are one of the major challenges in additive manufacturing of metallic materials today. They are induced during manufacturing because of the rapid local heating and cooling and may cause distortions, cracking and delamination between layers. The magnitude of the residual stresses depends on factors such as manufacturing technology, material, part geometry, scanning strategy, process parameters, preheating temperature and density of the component. In the present work, the magnitudes of residual stresses and distortions in austenitic stainless steel 316L components manufactured by Selective Laser melting have been investigated. Four specimens with rectangular cross-sections where produced with different heights and wall thicknesses. The residual stresses were measured by two different methods, x-ray diffraction and Electronic Speckle Pattern Interferometry (ESPI) incremental hole drilling in order to see how well they correspond to each other. The results showed peaks of high tensile stresses in the building direction in all specimens. The magnitudes of stresses were similar in all four specimens. The largest distortions occurred when the wall thickness was increased, and the height was reduced. It was also shown that the measurements made by x-ray diffraction and ESPI incremental hole drilling were not consistent with each other. The latter showed unrealistically high measurements near the surface.