Corrosion Science 257 (2025) 113351

Valence-dependent TiO₂ inhibition for enhancing oxidation resistance in Ti₂AlC via Zr/Nb Solid Solution
Yuxi Xu#, Guanshui Ma#, Zhongchang Li, Yan Zhang, Anfeng Zhang, Zhenyu Wang, Aiying Wang*

Ti₂AlC, as a typical MAX phase material, combines the excellent properties of both metals and ceramics for protective coatings used in harsh high-temperature conditions. However, concurrent existence of TiO₂ (rutile) and Al₂O₃ easily causes the rapid growth of oxide scales and poor oxidation durability. In this study, we explored the pivotal concept of vacancy-dependent Zr/Nb solid solution to improve the oxidation resistance of Ti₂AlC coating through the comprehensive atomic-scale calculations and microstructural characterizations. Results showed that the incorporated Zr and Nb concentration was about 5.3 and 5.2 at.% in high-purity Ti₂AlC coating, respectively, presenting the homogeneous substitutions for M-site Ti atoms within the nanolayered structure. Comparing with the pristine Ti₂AlC coating, both Zr and Nb solid solution distinctly inhibited the growth of TiO₂ and simultaneously promoted a continuous Al₂O₃ layer, enhancing oxidation resistance during 650 °C exposure. The density functional theory calculations revealed that either solid solution of Zr or Nb in Ti₂AlC significantly increased Ti vacancy formation energy, suppressing the generation of Ti vacancies that are essential for Ti diffusion. In addition, the higher valence state of Nb⁵⁺, compared to Zr⁴⁺ constituent was found to be more effectively inhibiting the growth of non-protective TiO₂ film.

URL：https://doi.org/10.1016/j.corsci.2025.113351