Effect of Build Orientation on Residual Stress and Microstructure in Inconel 625 Fabricated via Laser Powder Bed Fusion

Abstract

The reliability of parts produced by Laser Powder Bed Fusion (L-PBF) is still not at a great acceptance level. One of the major defects inherited in parts fabricated from L-PBF is a high level of residual stress. In this study, two build orientations i.e., vertical and diagonal, were used to fabricate Inconel 625 specimens to observe its effects on the residual stress magnitude and grain growth. A novel, Cos-α X-ray diffraction method was used to measure residual stress values along the top surface of the samples. Electron Backscattered Diffraction (EBSD) and kernel average misorientation (KAM) maps were employed to explain residual stress trends and differences between samples. Results indicate that the as-printed vertical sample possessed a higher tensile residual stress (77 ± 15 MPa) compared to the diagonally-printed sample (52 ± 12 MPa). The KAM map of the as-printed vertically oriented sample showed more pronounced local misorientations caused by dislocations compared to the diagonally-printed sample.