3D printing of ER308L structural components by means of a novel double-wire TIG-WAAM technology
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A double-wire TIG-WAAM 3D printing technology was successfully developed in the framework of the DWYN project, and used for the manufacturing of a 50x150x300 mm rectangular hollow section from ER308L steel with ultimate tensile strength and hardness in the range of the as-welded material with no considerable differences along the length of the specimen, indicating the homogeneity of the 3D printing process. The specimen presents relatively smaller yield strength and elongation (15.3 and 7.4%, respectively) than the as welded material, which could be due to the inherent anisotropy of the mechanical properties in 3D printed parts caused by the layer-by-layer deposition methodology. The printed sample shows no apparent porosity or impurities inside or between the layer boundaries, with an austenitic microstructure with columnar delta ferrite dendrites along the building direction caused by the fast cooling of the welding process. Mechanical and microstructural results indicate the potential of the as-machined double-wire TIG-WAAM 3D printed specimens for structural applications, although anisotropic mechanical properties should be taken in consideration at the same time that a further optimization of the process parameters and additional mechanical studies need to be carried out to completely assess the suitability of the technology for its use in highly demanding applications.