The high-temperature corrosion resistance of multicomponent intermetallic compounds in liquid lead-bismuth eutectic at 800 °C

Abstract

The lead-bismuth fast reactor is one of the most promising Generation IV nuclear reactor systems, operating at a core temperature of 800 degrees C with an efficiency of 50 % or more. However, corrosion problems severely hamper its power generation efficiency. Chemically complex intermetallic alloys (CCIMAs) with superior mechanical properties have emerged as potential candidates to mitigate this issue. The corrosion mechanism of an L12-type Co-Ni-Al-Ti-Ta-Nb-based CCIMA exposed to liquid lead-bismuth eutectic (LBE) was investigated at 800 degrees C. The results revealed the formation of double-layer scales in LBE. Preferential oxidation dominated within the first 72 h, following parabolic kinetics, while a combined oxidation and dissolution mechanism prevailed from 72 to 168 h, exhibiting concave kinetics. The initial oxidation is primarily attributed to the rapid formation of CoNiO2 and Al2O3 on the alloy surface. However, defects in the outer oxide layer (OOL) facilitated the penetration of LBE into the scale, and the varying solubility of alloying elements in LBE accelerated corrosion, leading to forming two distinct morphologies in the inner oxide layer (IOL). OOL formed by the preferential oxidation process effectively suppressed the dissolution rate of CCIMA in LBE, contributing to its remarkable dissolution resistance.