Tensile and impact properties of 9Cr tempered martensitic steels and ODS-FeCr alloys irradiated in a fast reactor at 325 °C up to 78 dpa

Abstract

Four 9Cr Reduced Activation martensitic steels, two ODS-FeCr alloys and one conventional 9Cr martensitic steel were irradiated in BOR-60 reactor to doses ranging from 40 to 78dpa at 325°C. Tensile, impact tests and fracture surface examinations were subsequently carried out. All 9Cr steels showed strong increases in yield stress, decreases in ductility and large shifts of the Ductile-to-Brittle transition temperatures, however the degradation of tensile and impact properties was much more pronounced for the conventional 9Cr–1MoVNb steel. This steel displayed a brittle tensile behavior above 40 dpa of exposure whereas EUROFER retained significant ductility up to 78dpa. MA957 ODS in the fine-grain non-recrystallised condition, exhibited moderate irradiation-induced hardening together with a ductile behavior up to the highest dose, but its impact properties after irradiation were inferior to those of 9Cr RA steels, while EUROFER ODS irradiated to 40dpa showed poor tensile and impact behavior.