Fracture and Tensile Characterization of Additively Manufactured Type 300 Series Stainless Steel in the Baseline and Hydrogen Charged Conditions

Abstract

Savannah River National Laboratory (SRNL) has characterized powder bed fusion processed Type 304L stainless steel for use as hydrogen storage and process vessels. As part of this characterization, a simple cylinder (C-cylinder) and a “D-cylinder” were fabricated using two different Laser Powder Bed Fusion (L-PBF) machines at two different sites. These four sample cylinders were electrical discharge machined (EDM) into cylindrical blanks and rectangular blanks and subsequently finished machined into tensile samples and single edge notched three-point bend fracture toughness samples, respectively. The microstructures of the cylinders were optically characterized parallel to the build direction and perpendicular to the build direction at three elevations. Samples were hydrogen charged using conditions to generate approximately 70 wppm (3700 appm) hydrogen. The sub-sized cylindrical tensile samples and fracture toughness samples were non-destructively characterized using computed tomography with a voxel size of nominally 80 microns. Metallographic analysis and CT indicated the samples are virtually pore free and exhibit the expected microstructure of L-PBF processing. The mechanical test samples were tested in the baseline and hydrogen charged conditions to determine the tensile and fracture toughness behavior; based on previous results, the baseline tensile and fracture properties are comparable to wrought material and the hydrogen properties exhibit similar characteristics to wrought materials.