ODS-Eurofer - A Reduced Activation Ferritic Martensitic (RAFM) ODS-steel for Application in Advanced Blanket Concepts

R. Lindau (Sp), A. Möslang, M. Rieth, P. Norajitra, Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany) 
Advanced blanket concepts like the Dual-Coolant Pb-Li/He Blanket consist of a RAFM structure (e.g. Eurofer) with SiCf/SiC channel inserts and an ODS-plated First Wall to withstand the higher thermal and mechanical load.
To proof the feasibility of such a blanket concept not only suitable materials but also appropriate joining techniques have to be provided.
A sheet of ODS-Eurofer steel containing 0.3 wt.-% Yttria was produced in cooperation of FZK and PLANSEE. The production route included compaction of the mechanically alloyed steel powder by hot-isostatic-pressing and subsequent rolling. Different heat treatments were applied to study their effect on the mechanical properties.
Tensile tests between RT and 750°C revealed superior strength and ductility of the ODS steel compared to non-ODS RAFM steels like Eurofer 97. Impact tests on sub-size KLST specimens show improved properties compared to hipped ODS-Eurofer of the first generation. The Ductile-to-Brittle-Transition-Temperature (DBTT) could be shifted from values between +60 and +120°C to values between -40 and -80°C. The upper shelf energy (USE) was increased by about 40%. Creep tests in the temperature range between 600 and 700°C up to 10.000 h rupture time also confirm the good behaviour of ODS-Eurofer.
Diffusion welding is regarded as one of the most promising methods to produce ODS-plated structures. Blocks of ODS-Eurofer and Eurofer steel were joined together by hot isostatic pressing applying different sets of HIP cycles and post-weld heat treatments.
Tensile tests between RT and 700°C revealed good strength and ductility of the welded joints. The joints reached in any case the strength of the base Eurofer steel. Impact tests on KLST specimens of the dissimilar ODS/Eurofer joints revealed upper shelf energies up to 80% of Eurofer; DBTT is about ?50°C.

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