Stress corrosion cracking behavior of T91 steel in low oxygen concentration liquid lead-bismuth eutectic at 450°C

Abstract

The compatibility issue of structural materials in liquid lead-bismuth eutectic environment significantly influences the safe operation of lead-cooled fast reactors, which becomes more complex in the presence of stress. However, the stress corrosion cracking behavior and mechanisms in liquid lead-bismuth eutectic environment remain unclear, especially at low oxygen concentration. In this study, the stress corrosion cracking behavior of T91 steel in low oxygen concentration liquid lead-bismuth eutectic environment at 450°C was investigated. The crack initiation mechanisms in T91 steel at the nano to micro scales are analyzed. It is found that stress promotes the formation of microchannels in the substrate. In addition, increasing stress also promotes the formation of low-angle grain boundaries, which enhance the diffusion of elements and the preferential formation of oxides at grain boundaries. The above process compromises the strength of grain boundaries and therefore results in the preferential initiation of microcracks at grain boundaries.