Embrittlement of ER309L stainless steel clad by sigma-phase and neutron irradiation

Abstract

The degradation of mechanical properties in RPV clad by the presence of sigma-phase and neutron irradiation was investigated using small punch (SP) tests. The irradiation doses at 290 degreesC ranged from 5.01 x 10(18) to 5.79 x 10(19) n/cm(2) (>1 MeV). After irradiation, the increase in SP ductile-to-brittle transition temperature (SP-DeltaDBTT) was approximate to14 K, independent of the fluence. However, it was more strongly affected by the amount of brittle sigma-phase. The cracking appearances in the SP specimens gradually changed from circumferential to radial cracking as a function of test temperature, content of sigma-phase and neutron irradiation. These results are discussed in terms of the different fracture stress of each phase as well as the irradiation-induced hardening combined with the changes of governing stress components for crack initiation during deformation by means of finite element stress analysis. (C) 2004 Elsevier B.V. All rights reserved.