A dense Fe-Al/Al2O3 coating as tritium permeation barrier on CLAM steel by hot-dipping aluminizing

Exploring tritium permeation barriers with high permeation reduction factor (PRF) by an industrial scale process is crucial for tritium systems in fusion reactors. Herein, we fabricated a dense Fe-Al/Al2O3 coating by a simple hot-dipping aluminizing (HDA) method and optimized oxidation strategy. The microstructure, chemical composition, and crystallographic characteristic of obtained samples were investigated. And the permeation of deuterium through the sample was determined by gas-driven permeation (GDP) experiments. The results show that the obtained oxide coating mainly consisted of γ-Al2O3 layer and FeAl gradient transition layer. Notably, the Al2O3 layer formed by the oxidation of FeAl alloy coating possessed a high PRF value of 2394 at 550 °C. Compared with the direct oxidation of HDA sample, the oxide coating prepared by the alloy topcoat oxidation strategy was denser and had less defects. Meanwhile, the effect of Al topcoat and different FeAl alloy topcoats on the microstructure and performance of the oxide coating were investigated, respectively. And the formation mechanisms of oxide coatings prepared by different oxidation strategies were also analyzed.