Mechanical characterization and performance of reduced scale mock-up for the CFETR first wall manufactured by SLM process

The blanket, one of the most important parts in China Fusion Engineering Test Reactor (CFETR), is the carrier with core function for fusion reactor application. First wall (FW) is the key unit of the blanket, facing the plasma directly and playing a decisive role in the fusion reactor. In this study, the reduced scale FW U-shaped mock-up formed by selective laser melting (SLM) was investigated. The influence of microstructure anisotropy on mechanical properties from vertical direction (z-x) and horizontal direction (x-y) was researched and the feasibility of SLM technology applied to nuclear fusion was explored. Experimental results show that the grain structure is mainly polygonal cellular crystals in x-y direction and elongated columnar crystals in z-x direction under scanning electron microscope (SEM) observation. This grain growth mode is attributed to the complicated temperature field inside molten pool. The inverse pole figures (IPF) in electron backscatter diffraction (EBSD) analysis suggest that the SLMed 316 L in z-x direction has the preferred orientation in (110) and (111) in x-y direction. Compared with 316 L forgings, SLMed 316 L showed higher average tensile strength, elongation rate and Vickers hardness in 2 directions. The impact toughness was enhanced compared with previous references, which demonstrated that SLM technology is proved an effective way to fabricate FW in the nuclear fusion field.