Weldability, microstructure and mechanical properties of laser-welded selective laser melted 304 stainless steel joints

Abstract

Abstract Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhardness, tensile properties and corrosion resistance of the laser welded stress-relieved SLMed 304 stainless steel joints are investigated, as the different sections of stress-relieved SLMed 304 stainless steel are joined. Results show that the SLMed 304 stainless steel plates have a good laser weldability. The microstructure of laser-welded joints consists of the cellular dendrites in austenite matrix within columnar grains, exhibiting a coarser dendrite structure, lower microhardness (∼220\u2009HV) and tensile properties (tensile strength of ∼750\u2009MPa, and area reduction of ∼27.6%), but superior corrosion resistance to those of SLMed plates. The dendrite arm spacing of the joints varies from ∼3.7\u2009μm in center zone, to ∼5.0\u2009μm in fusion zone, to ∼2.5\u2009μm in epitaxial zone. The SLMed anisotropy shows a negligible effect on the microstructure and performance of the laser-welded joints. The laser welding along the building directions of the SLMed base plates can induce a slightly finer dendritic structure and higher tensile properties.