Directed energy deposition of steel 316L: Effects of build orientation

Metal Additive Manufacturing for the production of end parts is today the major interest in the field of layer-by-layer fabrication. Even if Powder Bed Fusion is by far the most diffused technology, powder-fed systems retain a specific attractiveness, mainly because they enable an easier manufacture of multi-material parts or even of composition-graded ones. These systems, recently categorized by ASTM standards under the term Directed Energy Deposition (DED), still suffer from scarce knowledge of part characteristics and of process robustness and repeatability. Among DED processes, Laser Consolidation (LC) allows the production of net-shape metal parts with good metallurgical soundness, high strength and ductility. As regards the mechanical performance, the non-coaxial architecture of the LC head poses the question of a secondary anisotropy, within each layer, in addition to the primary one that is due to the layerwise construction. The paper addresses the mechanical response and the microstructure obtained by LC with AISI 316L. The direction dependence of part properties is specifically explored. Remarkably high ductility, combined with high hardness and strength, are obtained. The effect of the relative orientation between the LC head and the part is quantified and associated with the observed microstructure.