Low cycle fatigue of EUROFER97 investigated for test blanket modules of ITER: An interlaboratory study

Several reduced-activation ferritic-martensitic (RAFM) steel grades have been proposed for structural applications in fusion reactors since the 1990s by several countries. The European reference RAFM steel EUROFER97 has been produced in four batches since 1998. It is intended for fabrication of Test Blanket Modules (TBM) for ITER as well as the blanket first wall and divertor cassettes of DEMO. RCC-MRx is the design code developed for high-temperature, research and fusion reactors by AFCEN. Its latest edition contains a provisional section dedicated to EUROFER97, aggregating properties of the first two batches, whereas a full qualification and final inclusion of a material requires three batches minimum. The completion of the code is required for the design assessment of TBM units in the frame of the nuclear licensing process. The EUROfusion project coordinates efforts to broaden the knowledge of EUROFER97 properties, which will be used for closing the database gaps in RCC-MRx. Low cycle fatigue (LCF) tests are a significant part of the EUROfusion test programme, since the material fatigue properties are indispensable for the component assessment owing to the cyclic nature of a tokamak operation. In this work we report the results of interlaboratory LCF tests on EUROFER97 batch 3 performed in a temperature range relevant for its application in ITER (RT–550 °C), wide selection of total strain ranges (0.3–1.5 %) and two values of strain ratio R_ε (0 and –1). Along with the estimated fatigue life and cyclic behaviour, a fractographic analysis done with scanning electron microscopy (SEM) is presented.