Impact properties of reduced activation ferritic/martensitic steel, F82H jointed by hot isostatic pressing

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

Reduced-activation ferritic/martensitic steels are leading candidates for the blanket and first wall of fusion reactors. The important issue in current stage is the finalization of detailed manufacturing specification for ITER test blanket module. Hot isostaic pressing (HIP) process is one of the most important methods to fabricate the first wall with cooling channel. The objective is to optimize HIP condition with the excellent joints strength and microstructural evolution. The materials used were F82H steels. The joint was produced by solid state HIP method. Before HIP treatments, the gases in specimens were evaporated in the vacuum. This treatment was conducted to decrease oxidation on the surfaces. HIP treatments were carried out for 2 h at 1100 C - 140 MPa. The specimens were normalized at 960 C for 0.5 h and tempered at 750 C for 1.5 h. The bonding interface was characterized by scanning electron microscope. 1/3 charpy V-notch tests applied to the bonding strength. There were no significant difference in ductile-brittle transition temperatures of HIP jointed specimens and base metal specimens. Upper-shelf energy (USE) of HIP joint specimens at room temperature was lower than that of base metal specimens. The fracture had a large number of oxides. Therefore, the condition before HIP treatment was optimized to reduce the number of oxides. Because the density of oxides on the fracture was low level, its oxides along interface might be effective in the increase of USE. In the HIP process, Oxides along bonding interface are the dominant factor determining the impact properties of HIP jointed F82H steels. In this presentation, HIP processes will be reported that is effective in increasing USE.