A lattice Boltzmann phase-field model for duplex oxide growth and flow-induced corrosion of T91 steel in lead-bismuth eutectic

The oxidation and flow-induced corrosion of T91 steel in oxygen-controlled flowing lead-bismuth eutectic (LBE) are critical factors in evaluating its long-term performance in nuclear applications. In this study, a lattice Boltzmann phase-field model is developed to simulate the duplex oxidation process of T91, as well as the removal of the outer oxide layer, involving both dissolution and erosion caused by LBE flow. The phase-field equations governing both inner and outer oxidation, along with iron and oxygen diffusion inside the oxide scale, are solved using the lattice Boltzmann method. The effects of temperature, dissolved oxygen concentration, and flow velocity are quantitatively analyzed, with the impact of flow represented through a scale removal potential. The simulation results generally agree with experimental measurements and demonstrate improved predictive accuracy over existing oxidation-corrosion models. The dominant role of temperature in controlling duplex oxide growth is highlighted. An oxygen concentration on the order of $1\times 10^{-6}$ wt.% is found to balance protective oxide formation and stability under flow conditions. This study provides a practical modeling framework for long-term oxidation and corrosion assessment of structural steels and supports the selection of operational parameters for lead-cooled nuclear systems.