The role of Directed Energy Deposition atmosphere mode on the microstructure and mechanical properties of 316L samples

• Published in: Additive manufacturing Vol. 34; p. 101274
• Main Authors: Aversa, Alberta, Saboori, Abdollah, Librera, Erica, de Chirico, Michele, Biamino, Sara, Lombardi, Mariangela, Fino, Paolo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2020
• Subjects: 316L; Atmosphere; Directed Energy Deposition; Oxide; Tensile properties; Oxide; Directed Energy Deposition; 316L; Atmosphere; Tensile properties
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2020.101274

•Directed Energy Deposition was used to process 316 L in different atmosphere modes.•A slightly higher oxide content was detected in samples built using shielding gas.•The mechanical properties in both conditions were extremely high.•Samples built in controlled atmosphere had slightly higher yield strength.•A correlation between tensile properties and oxide content is reported. Laser-Directed Energy Deposition was used to produce AISI 316L stainless steel samples. The effect of the protective atmosphere on the microstructure and mechanical performance of AISI 316L deposited parts was investigated by building samples using a simple nitrogen shielding gas or using a nitrogen-filled build chamber. The effect of the different processing conditions on the microstructure was evaluated by X-ray analysis, optical and scanning electron microscopy. Only slight differences in the cellular dendrites morphology of samples built under different protective atmosphere conditions were observed. However, the presence of oxides was monitored too: the oxides composition and area fraction were analysed and compared by image analyses, and it was demonstrated that the protective atmosphere mainly affects the oxides dimensions. The effect of the oxides and nitrogen pick-up on the mechanical performance of the samples was evaluated by tensile tests. The results revealed that the nitrogen-filled build chamber allowed the achievement of slightly higher tensile strength and elongation with respect to the other processing conditions as a consequence of the reduced size of the oxide inclusions.