CORROSION IN STEEL T91 CAUSED BY FLOWING LEAD-BISMUTH EUTECTIC AT 400 °C AND 10~(-7) MASS SOLVED OXYGEN

摘要

Specimens produced from two different heats of ferritic/martensitic steel T91 were exposed to oxygen-containing flowing lead-bismuth eutectic (LBE) at 400 °C, 10~7 mass% solved oxygen and flow velocity of 2 m/s, for exposure times between around 1000 and 13,000 h. The occurring phenomena were analyzed and quantified using metallographic cross sections prepared after exposure. Oxidation causes a material loss of ＜10 μm after 13,000 h, while corrosion initiated by the solution of the steel elements may generally proceed around 15 to 30 μm deep into the material in the same amount of time. Oxide scales formed on both heats of T91 tend to buckle and detach. In the case of one of the investigated heats, a singular event of exceptionally severe solution-based corrosion was observed, with associated local material loss around 1.2 mm after 13,000 h. The results are compared especially with findings at 450 and 550 °C and otherwise similar conditions as well as austenitic steels tested in the identical experimental run.