Experimental and Molecular Dynamics-Based Study on the Influence Mechanism of a Lead–Bismuth Eutectic Corrosive Environment on the Thermal Conductivity of T91 Steel

Under lead–bismuth eutectic (LBE) corrosion conditions, the multilayer oxide layer that forms on T91 steel adversely affects on its thermal conductivity. This study systematically conducted corrosion experiments under varying temperatures, durations, oxygen concentrations, and bismuth (Bi) content. By combining microstructural characterization with laser flash measurements of thermal conductivity, the evolution of T91 thermal conductivity under different corrosion conditions was revealed. Based on these findings, molecular dynamics simulations based on the neuroevolution potential (NEP) framework were employed to construct a T91/Fe-Cr spinel/Fe3O4 multilayer heterojunction model, enabling precise determination of the intrinsic thermal resistances at the two interfaces. By coupling the interfacial thermal resistances with experimental data, the macroscopic effective thermal conductivities of Fe-Cr spinel and Fe3O4 in real corrosion environments were calculated to be 1.68 W/(m·K) and 2.19 W/(m·K), respectively. These values are significantly lower than those reported for pure phases, thus revealing the inhibitory effect of defects and pores in actual oxide layers on heat transport. This research establishes a multiscale analytical method spanning from atomic-scale interfacial thermal resistance to macroscopic heat transfer properties of oxide layers, thereby providing a theoretical basis and data support for the thermal performance evaluation and service life prediction of LFR structural materials.