Precipitation behavior in F82H during heat treatments of blanket fabrication

Reduced Activation Ferritic/Martensitic steels are leading candidates for the structural material of DEMO blanket module, and they are really used for the ITER test blanket module. During the fabrication process of blanket module, the structural material is exposed to various heat conditions. Microstructural evolutions under the complicated heat history should be focused, because they determine the performance of blanket module. Especially, it is important to study precipitation behavior, because they significantly affect the creep property, the material toughness, and irradiation resistances of RAFMs. In this work, we studied precipitation behavior in the F82H-BA07 heat (8Cr-2W-V, Ta) under the heat treatments which simulate homogenizing, Hot Isostatic Pressing, and temperature fluctuations of actual normalizing. From the result of X-ray diffraction analysis on the electrochemically extracted residues, no fine particles such as tantalum and vanadium carbides precipitated under the simulated heat treatments. From the result of Electron Probe MicroAnalysis, it was suggested that fine precipitates of tantalum and vanadium should appear at lower temperatures such as the tempering temperature.