Improvement of HIP joint process on reduced activation ferritic/martensitic steels

Ogiwara, Hiroyuki; Tanigawa, Hiroyasu; Hirose, Takanori; Enoeda, Mikio

Reduced-activation ferritic/martensitic steels are leading candidate structural material for the blanket system of fusion reactors. The important issue in current stage is the finalization of detailed manufacturing specification for ITER test blanket module. Hot isostatic pressing (HIP) process is one of the most important methods to fabricate the first wall with cooling channels. The objective of this paper is to optimize HIP condition to obtain the excellent joints mechanical properties. Upper-shelf energy (USE) of HIP joints increased with increasing the out-gas temperatures before HIP treatments. Impact tests revealed that USE of HIP jointed specimens were 80 % of base metal specimens at 600 C and 50 % at 400 C. The difference of USE will be related to the Thermal Desorption Spectroscopy spectrum of gasses from F82H because temperatures of desorption peak of CO and CO were between 400 C and 600 C. This result indicated that CO and CO out-gassed from pre-HIP joints are the dominant factor of the impact properties. SEM observation on the fracture surface of HIP joint specimen revealed that a large number of oxides were not formed on the HIP joint. Based on the results, the pre-HIP treatment conditions had been optimized to reduce the number of oxides, and USE of HIP joint specimen become about 80 % of base metal.