Residual Stress Gradient Built in X40CrMoVN16-2 Austenitic Steel Cube Manufactured by Laser Powder Bed Fusion
Résumé
Additive manufacturing processes and especially the family of laser powder bed fusion technologies have a great industrial potential since it enables, from metal powder beds, to produce full density complex monolithic parts. The high-temperature gradient resulting from the locally concentrated energy input leads to strong temperature fields driving non-negligible residual stress gradients, part deformations and crack formation. Resulting stress and texture gradients arise from the interdependent physical phenomena (metallurgical, thermal, mechanical and fluid mechanics) occurring during the process. Present work focuses on the residual stress being built in an austenitic stainless steel cubical shaped part of 1 cm side, prepared by a laser powder bed fusion process from a gas-atomized metallic powder (from martensitic X40CrMoVN16-2 stainless steel), through a full residual stress tensor mapping achieved thanks to neutron diffraction. Stress analyses incorporate morphological and crystallographic textures, as well as elastic anisotropy. Components of the principal stress tensor display compressive values close to the baseplate that develop into low compression, and a tensile stress state at the subsurface (surrounding thermal history effects). Results also underline the strong impact of matter environment (and thus thermal environment) onto stress gradient magnitude and the complex loading origins of the residual stress.