Quasi-static and fatigue behavior of 316L stainless steel produced via material extrusion additive manufacturing: Insights from subtracted small-scale specimens

The mechanical anisotropy of 316L Material Extrusion Additive Manufacturing parts is investigated through tensile and fatigue tests on three groups of specimens printed in different layouts. Both regular and in-situ tensile tests proved a significant dependency of the strength and ductility of the parts on the loading direction, with a sequential effect on the fracture mechanisms. Moreover, the building orientation has a secondary effect on the residual porosity, which in turn impacts the axial fatigue failure mechanisms and the statistical significance of the results. Considering the tensile test results, a favorable building direction enables the printed parts to perform similarly to their conventionally manufactured counterpart. Interestingly, the fatigue data can be fitted by fatigue design curves obtained with the standard procedure. The examination of the data collected revealed that caution is required to acknowledge the variations in the mechanical response of the parts induced by the building orientation to offer top mechanical performances. Indeed, such variations might be mitigated by improving the quality of the printing phase, with a focus on porosity reduction and material adhesion strengthening.