Creep-Fatigue Interaction in Eurofer 3 Electron Beam Welds

In future nuclear fusion reactors, structural materials will undergo a large thermal cycling due to pulsed operation and the occurrence of several maintenance periods. Therefore, the investigation of the combined role of creep and fatigue loading is of major importance. In this study, we focused on Eurofer 3 electron beam welds. Two different post-welding heat treatments were carried out: a two-step heat treatment (30 minutes at 980°C followed by 2 hours at 750°C) and a one-step heat treatment (2 hours at 750°C). Fatigue, creep and creep-fatigue tests were performed. A 550°C test temperature was chosen, corresponding to the upper operation temperature currently foreseen for this material. Creep-fatigue experiments were achieved by interrupting a fatigue test and then applying a creep loading until the fracture of the specimen. Several fatigue pre-stress conditions were studied. The post-weld heat treatment influence was analyzed. The damage contributions of fatigue and creep were studied using electron microscopy. The results were compared to previous results obtained on base material.