Structure and mechanical properties of EUROFER97 steel exposed to flowing Pb-17Li

Full text: One of the main tasks in a problem of designing of fusion reactors is maintenance of reliability of liquid metal blanket operation in extreme conditions: irradiation, strong magnetic fields and liquid Pb-17Li eutectic alloy flow. At the moment as a structural material the steel EUROFER 97 is considered, the corrosion rate of which in liquid Pb- 17Li eutectic alloy is minimal. However, at the moment there are no data about influence of strong magnetic field on corrosion of this alloy exposed to flowing Pb-17Li alloy. The aim of presented work is the experimental investigation of magnetic field (B=1.7T) influence on the structure and hardness of EUROFER 97 steel exposed to Pb-17Li eutectic alloy flow having velocity 2.5.-. 5 cm/s at 550 deg C. It was shown that the magnetic field causes faster detachment of corrosion layers that is associated with development of erosion processes due to turbulent flows. SEM images of attacked surfaces showed that without magnetic field dissolution of surface occurs uniformly both for ferrite and for martensite grains. At presence of a magnetic field there is a crushing of martensite phases and fast dissolution of interphase volumes. EDX point analyses of surfaces showed that magnetic field increases dissolution of chrome in investigated samples and activates the processes of mass transfer and sedimentation of some metals. The hardness of steel seem to be unaffected by corrosion processes in magnetic field