Dissolution corrosion of FeCrAl alloy exposed to oxygen-depleted lead–bismuth eutectic containing Ni impurities at 600 ℃

Abstract

FeCrAl alloy is one of the potential candidates of structural materials due to its high strength, low radiation swelling and good oxidation resistance for the application of lead-cooled fast reactors (LFRs). Particularly, FeCrAl alloy can form protective Al-containing oxide scales after exposure to liquid oxygen-rich Pb and lead–bismuth eutectic (LBE) at 400–800 ℃, showing better performance than traditional commercial stainless steels such as T91, 316L and 15-15Ti. Given the possibility that oxygen in liquid metal could be consumed and not be supplied timely in some quasi-static regions of the actual coolant circuit, to figure out the corrosion behavior of FeCrAl alloy in oxygen-depleted LBE is necessary. In this work, the commercial FeCrAl alloy was exposed to static liquid LBE containing Ni impurities with 10−9 wt% oxygen concentration at 600 ℃ for up to 5000 h, and the surface and cross-sectional morphology of the samples was characterized and analysed. It is found that FeCrAl alloy underwent severe dissolution corrosion, and the maximum penetration depth of LBE reached 161.4 μm after the test for 5000 h; PbBi infiltrated into alloy matrix along the GBs and selectively leached Al from the affected grains. Besides, an interesting discovery is the Cr-rich thin layer at LBE/matrix interface and Ni3Al precipitates in LBE penetration front which should be attributed to the deposition of impurity elements dissolved in liquid LBE during the cooling process.