Liquid Metal Embrittlement of a 9Cr-1Mo Ferritic-martensitic Steel in Lead-bismuth Eutectic Environment under Low Cycle Fatigue

Ferritic-martensitic T91 steel is a candidate material for constructing the proton beam window of the MYRRHA nuclear reactor, which is being developed in SCK CEN, Belgium for transmuting long-lived nuclear waste. As one important part of the MYRRHA material qualification program, liquid metal embrittlement (LME), a phenomenon could cause premature brittle failure of components, is crucial to be checked for T91 steel in contact with lead-bismuth eutectic (LBE) which is the coolant and spallation target of MYRRHA. In the literature, low cycle fatigue (LCF) data of T91 in LBE environment are too limited for the design of the MYRRHA reactor. Therefore, the impact of LME on the LCF properties of T91 steel in LBE under the MYRRHA’s real operation conditions should be investigated in detail. In order to realize this goal, an innovative fatigue testing system, called LIMETS3, is constructed to allow LCF tests to be conducted under a wide variety of experimental conditions, covering the reactor operation temperature window and different oxygen concentrations of LBE. Reprehensive fatigue data are produced to contribute to the design of the reactor. A systematic microstructural investigation is performed to improve the understanding of the LME mechanism in the T91/LBE system.