Hydrogen Embrittlement Behavior of Plastically Pre-Strained and Cathodically Hydrogen-Charged 316H Grade Austenitic Stainless Steel

Abstract

In this work, the effects of electrochemical hydrogen charging of 316H grade austenitic stainless steel were investigated in order to characterize its hydrogen embrittlement (HE) resistance. The as-received 316H material was in a fully recrystallized (solution-annealed) material condition. The susceptibility to HE of the studied material was evaluated by determination of the embrittlement index from the results of conventional uniaxial tensile tests of nonhydrogenated and hydrogen-charged test specimens. The study was focused on the effects of two selected plastic pre-strain levels of tensile specimens on their resulting HE resistance. The selected pre-strains corresponded to the tensile stress conditions within the “yield stress–ultimate tensile strength” (YS–UTS) range and directly at the UTS point. The obtained embrittlement indices for the presently used pre-straining and hydrogen charging conditions indicated that the HE of the studied material states was small. However, it was revealed that the observed degradation of deformation properties of plastically pre-strained and hydrogen-charged materials was mainly caused by gradual plasticity exhaustion due to tensile straining, which well correlated with the observed effects indicated by electron backscatter diffraction analyses and indentation hardness measurements.

Keywords

• austenitic steel
• hydrogen embrittlement
• microstructure
• tensile test
• fractography