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Abstract

Lead-cooled fast reactors and lead–bismuth eutectic (LBE) cooling systems are promising advanced nuclear technologies, but structural materials remain vulnerable to coupled corrosion and mechanical damage. Solid particles transported in LBE, such as oxide fragments and metallic debris, may induce localized erosion through impact and sliding, thereby compromising surface integrity and promoting subsequent corrosion. However, the atomic-scale mechanisms governing such damage remain unclear. In this study, molecular dynamics simulations were performed to investigate nanoindentation and nanoscratching of an Fe substrate by a solid Pb particle at 573 K. The mechanical response, surface morphology, local stress, crystal structure, and dislocation evolution were systematically analyzed. During indentation, the Fe substrate initially undergoes elastic compression and lattice distortion, followed by plastic relaxation through the nucleation and propagation of 1/2<111> dislocations. During scratching, combined normal compression and tangential shear drive irreversible plastic flow, producing continuous grooves and directional material pile-up. Structural analysis shows that high-pressure-induced phase transformation remains negligible, while plastic deformation is dominated by dislocation nucleation, propagation, reaction, migration, and annihilation. The synchronized fluctuations of normal and tangential forces further reveal strong coupling between contact mechanics and subsurface dislocation restructuring. These results provide atomic-scale insight into solid-particle-induced erosion damage and clarify the dominant role of dislocation-mediated plasticity in the initiation of mechanical damage–corrosion coupling in LBE environments.