A mesoscale phase-field model of intergranular liquid lithium corrosion of ferritic/martensitic steels

TL;DR

This paper introduces a mesoscale phase-field model to simulate intergranular lithium corrosion in ferritic/martensitic steels, capturing microstructural effects and matching experimental data.

Contribution

The model uniquely simulates intergranular corrosion in 2D and 3D geometries without special front treatment, incorporating microstructural influences and saturation effects.

Findings

Grain density significantly affects corrosion susceptibility.

Grain size influences intergranular corrosion susceptibility.

Model accurately reproduces experimental weight loss and corrosion depth.

Abstract

A phase-field model is developed to simulate intergranular corrosion of ferritic/martensitic steels exposed to liquid lithium. The chromium concentration of the material is used to track the mass transport within the metal and liquid (corrosive) phase. The framework naturally captures intergranular corrosion by enhancing the diffusion of chromium along grain boundaries relative to the grain bulk with no special treatment for the corrosion front evolution. The formulation applies to arbitrary 2D and 3D polycrystalline geometries. The framework reproduces experimental measurements of weight loss and corrosion depth for a 9 wt\% Cr ferritic/martensitic steel exposed to static lithium at 600 $^\circ$C. A sensitivity analysis, varying near-surface grain density, grain size, and chromium depletion thickness, highlights the microstructural influence in the corrosion process. Moreover, the significance of saturation is considered and evaluated. Simulation results show that near-surface grain density is a deciding factor, whereas grain size dictates the susceptibility to intergranular corrosion.