Study on failure behavior of Inconel 625 in a hydrogen-containing environment

Inconel 625 for hydrogenation heat exchangers was studied to investigate its failure behavior in a hydrogen-containing environment. Hydrogen was introduced into Inconel 625, and the effect of hydrogen on pitting behavior was studied with electrochemical test, chemical immersion experiment and other methods, and the initiation and propagation behavior of pitting corrosion and the fracture morphology before and after hydrogen charging were observed with microscopic characterization methods such as SEM and EDS. In addition, a slow strain rate tensile test was carried out to observe the stress-strain curve of Inconel 625 and analyze its strength and plasticity. The findings indicated that although hydrogen charging reduced the corrosion resistance of Inconel 625, but did not significantly impact pitting corrosion, with little change in pitting potential, with no significant changes in the pitting nucleation rate observed, pitting only propagating inside the precipitated phase, without propagating towards the matrix after the precipitated phase got fully solved. Even though the enrichment position of hydrogen in Inconel 625 coincided with very few initiation positions of pitting pits, hydrogen had no significant impact on pitting behavior, still with stronger repassivation ability in the condition of hydrogen charging. The sensitivity of Inconel 625 to hydrogen embrittlement significantly increased by hydrogen charging. After hydrogen charging, fracture morphology showed an intergranular fracture feature, and cleavages and secondary cracks also appeared.