Research Progress on Defect Behavior, Microstructure, and Service Performance of Additively Manufactured Austenitic Stainless Steels

Additive manufacturing provides a promising route for the precision fabrication and property tailoring of austenitic stainless steels because of its high design freedom, rapid customization capability, and near-net-shape manufacturing advantages. However, rapid melting–solidification and non-equilibrium thermal cycling generate strongly textured columnar grains, dislocation-cell structures, retained δ-ferrite, and heterogeneous residual stresses. These features are often accompanied by pores, lack-of-fusion defects, cracks, and environment-sensitive degradation, which restrict reliable application in demanding engineering fields. This review critically summarizes recent progress in defect formation, microstructural regulation, and service performance of additively manufactured austenitic stainless steels, following a unified process–thermal history–defect/microstructure–property framework. Particular attention is given to the effects of solidification mode, crystallographic texture, grain-boundary characteristics, and post-processing on multiscale microstructures and process–defect–microstructure–performance relationships. Finally, key technical bottlenecks, scientific knowledge gaps, and future development directions are identified to guide further research and engineering applications.