Local Failure Strain and Reduction of Area Provide Early Metrics for Hydrogen Embrittlement in Microscale Austenitic Stainless Steel Tensile Specimens

Background: Hydrogen embrittlement is the phenomenon by which a metal loses ductility and strength due to the presence of hydrogen atoms within the lattice. Objective: In this technical note, we studied hydrogen embrittlement in microscale austenitic stainless steel specimens (AISI 303, 316L, and 316Ti) during quasistatic tensile testing as a function of charging conditions. Methods: In particular, microstructure, hydrogen content, global and local mechanical properties, and failure modes were investigated through scanning electron microscopy, thermal desorption spectroscopy, microscale tensile testing, and fractography. Results: The microstructural and hydrogen desorption measurements showed that hydrogen content was relatively invariant of microstructure with a 2× change between the low-pressure (LP) and high-pressure (HP) conditions. The micromechanical tests and fractographic images revealed negligible changes in global properties (tensile strength, global failure strain), but significant changes in local properties (local failure strain, reduction of area), with embrittlement. The extent of embrittlement increased as hydrogen content increased and microstructural stability decreased. Conclusions: Similar to results on macroscale specimens, the results from microscale tensile specimens showed reduction of area provided a reliable measure for hydrogen embrittlement. Local failure strain confirmed these trends. Moreover, the microscale method facilitated a significant decrease in time for hydrogen saturation and material for specimen fabrication, enabling testing of small components or local properties in large components.