Electropulsing-Assisted Ultrasonic Surface Rolling and Pre-Oxidation Synergistically Enhance the Corrosion Resistance of Ferritic/Martensitic Steel in Liquid Lead-Bismuth

Abstract

This study investigates the corrosion susceptibility of ferritic/martensitic (F/M) steels in liquid lead-bismuth eutectic (LBE) environments by examining the effects of the electropulsing-assisted ultrasonic surface rolling process (EP-USRP) and pre-oxidation treatment on their corrosion behavior. The results demonstrate that, under optimized parameters, EP-USRP significantly reduces the surface roughness of the initial F/M steel by 46.7% (from Ra 0.197 µm to Ra 0.105 µm), enhances surface hardness by 35.9% (from 221.5 HV to 300.3 HV), and extends the depth of the strengthening layer beyond 1000 µm. Furthermore, the combination of EP-USRP and pre-oxidation treatment promotes the formation of a dense, polycrystalline MnCr2O4 layer at the oxide-substrate interface. This layer not only improves high-temperature oxidation resistance but also effectively mitigates dissolution attacks by LBE. After 3000 hours in LBE, the EP-USRP and pre-oxidized sample forms a Cr, Mn, and Si-rich internal oxidation layer at the oxide-substrate interface, significantly suppressing the outward diffusion of Fe. The total thickness of the corrosion layer is reduced to approximately 35.7% of that of the initial sample, while the maximum wear amount of the surface of the corrosion layer decreases to 57.6% (from 958.7 µm² to 551.7 µm²). These results demonstrate that the combination of EP-USRP and pre-oxidation treatment significantly enhances the corrosion resistance of F/M steels in LBE, providing a novel technological approach for optimizing structural materials in advanced nuclear reactor systems.

Keywords: Ferritic/martensitic steel, Electropulsing-Assisted Ultrasonic Surface Rolling, pre-oxidation, Liquid lead bismuth eutectic