High hydrogen permeation resistance achieved in a novel (AlCrZr)O ternary oxide nanofilm

Ceramic coatings with high hydrogen permeation resistance are highly important for protecting metal components from hydrogen attack. In this work, we fabricated an ultrathin (AlCrZr)O nanofilm with superior hydrogen barrier efficiency via a facile sol‒gel technique. This novel ternary oxide nanofilm with an overall thickness of only 100 nm has a high hydrogen permeation reduction factor (PRF) of up to 2364 at 773 K, decreasing the hydrogen permeability by three orders of magnitude compared to that of the steel substrate. The permeation cycling performance and thermal shock resistance of the nanofilm were further evaluated, which demonstrated good stability, with its PRF consistently remaining at a level of 10³. These excellent performances of the (AlCrZr)O nanofilm were attributed to its uniquely layered structure, consisting of an amorphous Al‒Zr‒O layer at the top and a crystalline Cr₂O₃ layer underneath. The amorphous layer without grain boundaries complicated the hydrogen diffusion pathways and effectively increased the hydrogen resistance. Moreover, the crystalline Cr₂O₃ layer could help mitigate the thermal expansion mismatch between the nanofilm and the steel substrate, ensuring good stability of the barrier performance under thermal conditions. These findings underscore the significant potential of the (AlCrZr)O nanofilm for hydrogen embrittlement protection and provide a new framework for designing highly efficient hydrogen permeation barriers that combine superior performance with extended lifespans.