Observations on high-temperature deformation and fracture of an irradiated austenitic stainless steel with additions of titanium and boron

Abstract

A chromium-nickel-molybdenum stainless steel with titanium and boron additions, solution-treated or solution-treated, cold-worked and recovery-annealed, was studied before and after irradiation in a thermal materials-testing reactor. Irradiations were performed at 700°C to almost complete boron-10 burn-up. The post-irradiation creep properties were compared with the creep properties of the steel as delivered and after a parallel annealing at 700°C. Broadly speaking, the creep strength of the solution-treated steels was not altered as a result of irradiation but was decreased by annealing at 700°C. The opposite was true for the cold-worked recovery-annealed material. These effects are due to different modes of TiC precipitation during or before testing and to the degree of recovery after cold work. Irradiation reduced the ductility to a varying degree, depending on the material condition. The smallest change was observed on 1100°C-annealed steel after cold work and recovery-anneal at 850°C. That condition also had the smallest grain size. The effect of irradiation on the ductility may be explained in terms of the diffusion of boron to the grain boundaries during irradiation at 700°C, and the influence of the resulting helium-rich zones at grain boundaries.