On the scalability of strength and presumed size effects in SLM-produced 316L stainless steel

Abstract

Abstract. As additive manufacturing (AM) technology advances toward the production of structurally utilized metallic components, an accurate evaluation of mechanical properties becomes crucial. Understanding the effect of the printed cross-section size on material strength is exceptionally important since AM technology, especially laser powder bed fusion (L-PBF), enables topology optimization and favors the production of thin struts, lattice structures, and other small cross-sections, as well as thin-walled profiles. Structural designers need to know to what degree the size of the printed cross-section might affect material strength. This study focuses on the effect of printed cross-section size on the mechanical properties of L-PBF-produced 316L stainless steel. The findings reported in existing literature so far are conflicting, indicating a need for further investigation. In the presented paper, the mechanical properties of net-shape printed samples with cross-section diameters ranging from 2.5 mm to 6.0 mm are compared. Tensile tests reveal that smaller diameter net-shape samples exhibit lower strength compared to larger diameters. Machined samples display higher strength than net-shape samples. The observed size-dependent strength variations in L-PBF-produced 316L stainless steel can be explained by the surface layer being weaker than the core of the sample. Whether the effect is due to differences in microstructure between the surface and core of the sample or is simply caused by a reduction of the effective cross-sectional area due to surface roughness could be debated, but both factors are likely to contribute to the phenomenon.