Residual Stress Measurement of Laser Powder Bed Fusion Additively Manufactured Hastelloy-X Through Crystal Plasticity Simulations and Neutron Diffraction Experiments

Abstract

The laser powder bed fusion additive manufacturing (LPBF-AM) technique enables the production of near-net-shaped metal components, but the concentrated heat input employed during manufacturing leads to the development of significant internal residual stresses. These residual stresses may cause considerable issues such as distortion, crack initiation during fabrication, and premature failure during service. In this study, neutron diffraction experiments were performed on a nickel-based superalloy, Hastelloy-X, to evaluate the state of residual stresses below and near the surface of as-built specimens as a function of LPBF-AM core process parameters. In addition, a crystal plasticity method was used to determine the diffraction elastic constants to provide a better estimation of residual stresses for textured specimens. The results indicate large tensile residual stresses of about 660 MPa along the scanning direction, counterbalanced by compressive ones below the surface. It is shown that internal and surface residual stresses increase with the laser specific energy. The use of various diffraction peaks for determining residual stresses is discussed and it is shown that while trends do not change, the magnitudes of measured stresses vary.