电解液中 Na₂SiO₃ 浓度对铌合金微弧氧化膜层烧蚀性能的影响

Aiming to enhance the ablation resistance of niobium alloys, this study focused on the preparation of plasma electrolytic oxidation (PEO) coatings with varying porosity by modulating the concentration of Na₂SiO₃ in the electrolyte. The internal pore structure of the coating was reconstructed through X-ray computed tomography scanning, while the thermal ablation process was simulated using finite element analysis, facilitating the establishment of a comprehensive model for the thermal behavior of the coating. The results show that, as the concentration of Na₂SiO₃ increases, the porosity of the coating exhibits a trend of an initial decrease followed by an increase. Notably, at Na₂SiO₃ concentration of 10 g/L, the coating achieves its minimum porosity of 15.08%, with 40.2% of the pores exhibiting a pore-size ratio within the range of 0.6 to 0.7, thereby demonstrating the transition from interconnected voids to isolated pores. This phenomenon can be attributed to the presence of isolated pores, which decrease the coating’s density. Bowever, their spatial separation facilitates the dispersion of thermal stresses, thereby mitigating local stress concentrations and enhancing the coating’s ablation resistance. Conversely, the extensive presence of interconnected pores elevates the thermal conductivity of the coating, rendering it more susceptible to the formation of thermal stress concentration cracks, which consequently leads to more pronounced ablation of the coating.