Tensile and impact properties of F82H steel applied to HIP-bond fusion blanket structures

In a fusion reactor, a blanket made of a low activation material like F82H steel is fabricated by HIP (hot isostatic pressing) bonding method. In a previous study, grain coarsening has been found in specific HIP-bond region of a mock-up of blanket structures. To verify an effect of the coarsening on mechanical properties of the HIP-bond region, tensile and impact tests were done. In result of the tensile test, there was no significant influence of the coarsening on the tensile properties of the HIP-bond region up to 500 °C. In the impact test (RT ∼−50 °C), temperature at which the absorbed energy of the HIP-bond region changed markedly (−35 °C) was almost same to DBTT of the matrix region (−30 °C), but the absorbed energy at room temperature (RT) decreased by about 40% in comparison with that of the matrix region. The major factors were: (1) large inclusions in the HIP interface; and (2) brittle fracture in a part of the HIP-bond region due to grain coarsening. It is important to eliminate a contamination caused by the inclusions from the HIP bonding surfaces, and also it is necessary to suppress and/or refine the grain coarsening.