Phase Instabilities Observed in EP-450 Ferritic-Martensitic Steel Irradiated at ～300℃ to 40.3 dpa in the BN-350 Fast Reactor

摘要

A spent fuel assembly wrapper was examined that served in the BN-350 fast reactor. It was made from Russian ferritic-martensitic steel designated 12Cr13Mo2NbVB or EP-450 with composition C-0.13; Cr-12.83, Ni-0.14; Mo-1.62; Nb-0.45; Si-0.4; Mn-0.34; V-0.16; B-0.004 wt.%. Thermal treatment involved normalization at 1050 ℃ and subsequent annealing at 750℃ for 1 hr. In its initial state EP-450 is usually employed in a two-phase condition with sorbite dominating over ferrite. Sorbite is a term used by Russians to characterize the desired optimal result of the decomposition of γ-Fe to α-Fe + Fe_3C upon cooling.