The Hydrogen Induced Mechanical Degradation of Duplex Stainless Steel

Abstract

This study considers the interaction between duplex stainless steel type 2205 and electrochemically charged hydrogen. Duplex stainless steels combine the mechanical properties of ferrite with the corrosion resistance of austenite and are widely used in many industrial applications. However, they are susceptible to hydrogen embrittlement. In this work, the steel microstructure is first characterized by scanning and transmission electron microscopy, X‐ray diffraction, and electron backscatter diffraction. Subsequently, melt extraction is done to determine the amount of hydrogen charged into the material, while in situ hydrogen charged tensile tests are combined with a fractography analysis to evaluate the effect of hydrogen on the mechanical behavior. The material displays a rather significant ductility loss of about 26% as a result of the applied hydrogen charging. Melt extraction identifies the increased hydrogen content in the steel microstructure (up to 50 wppm). Moreover, the hydrogen embrittled regions correspond well to the hydrogen diffusion penetration depth from the edges onwards. These cleavage brittle areas are observed up to the theoretical hydrogen diffusion distance, demonstrating the hydrogen embrittlement effect.

Evaluating the Hydrogen Embrittlement Susceptibility of Aged 2205 Duplex Stainless Steel Containing Brittle Sigma Phase

“…Saturation was not yet reached after 24 h of electrochemical hydrogen charging at room temperature as observed from the clearly increasing trend. Compared with a two‐phase austenite/ferrite 2205 DSS with the same composition studied in a previous work [ 18 ] and added to Figure 6 as a reference, the hydrogen concentration was largely reduced by the applied aging treatment (850 °C for 24 h) at similar charging times. As the hydrogen diffusion coefficient in austenite is lower than the one in ferrite and the aged specimen contained a higher austenite fraction (67% vs 50% 18 ), the overall diffusion speed of the aged sample was largely reduced.…”

“…Hydrogen concentration as a function of charging time for aged 2205 DSS; the data of Maria et al [ 18 ] were added to the graph as a reference.…”

“…Váñová similarly concluded that due to the intrinsic brittle character of their heat‐treated steel (±5% σ phase); the effect of hydrogen was not significant. In comparison, the data of Maria et al [ 18 ] were added to the graph (austenite/ferrite, 50/50). For the same charging conditions, an important ductility drop was observed for this microstructure.…”

“…Stress–strain tensile curves of aged 2205 DSS in air and in situ hydrogen charged condition; the data of Maria et al [ 18 ] were added to the graph as a reference. The data of the current work fully coincide.…”

“…[ 14–17 ] This undesirable phenomenon‐can ultimately have an unfavorable effect on the steel performance with very harmful consequences. [ 16–19 ] The analysis of the HE susceptibility of DSS is complex as both phases behave in a nonsimilar way with respect to their interaction with hydrogen. Ferrite shows a low hydrogen solubility and high hydrogen diffusivity, while austenite shows high hydrogen solubility and low diffusivity.…”