Si and Y co-alloying for superior LBE corrosion resistance through tailored interphases

Liquid metal corrosion has long been a critical threat to the safe operation of lead-cooled fast neutron reactors (LFRs) since the 1950s. In preventing such a degradation mode in the ferrite-martensite (F-M) steel—a commonly-used structure material in reactor core, the alloying elements of Si or Y are reported to be useful presumably due to the rapid formation of a dense oxide scale on the steel surface. Herein, we demonstrate a synergy of Si and Y in alleviating corrosion of the F-M steels in the liquid lead-bismuth eutectic at 600 °C. Atomic-scale characterizations indicate that, while Si introduces primarily SiO₂ pockets within the spinel layer, Y further prompts the SiO₂ and Cr₂O₃ formation at the interface of the oxide scale and the steel substrate, leading to unique interphase structure featuring amorphous SiO₂ and nanocrystalline Cr₂O₃ composite. In contrast to the scenario of the baseline steel, this dual-phase layer can significantly reduce the mass transfer and ameliorate the damage tolerance of the oxide||matrix interface. The attendant corrosion rate drop reaches up to ∼67 %. The findings demonstrate the synergistic effects of Si and Y in alleviating corrosion of F-M steels in simulated working conditions of advanced LFR, shedding lights on tackling corrosion through tailored interphases.