A high performance and dense Fe-Al/Al2O3 tritium permeation barrier prepared on 316LSS at low temperature

Abstract Deuterium and tritium are easy to permeate into the fusion reactor internals, and Fe-Al/Al 2 O 3 composite coating can effectively hinder the permeation behavior of hydrogen isotopes. However, the temperature in the preparation process of Fe-Al/Al 2 O 3 coating in many literatures is high, which will affect the mechanical properties of 316L stainless steel. In this paper, Fe-Al/Al 2 O 3 coating was prepared by pack aluminizing, heat treatment and in-situ oxidation at low temperature of 700°C or less. The aluminized layer gradually transforms from Fe 2 Al 5 and FeAl 3 to FeAl and Fe 3 Al during heat treatment. Compared with the aluminized layer prepared at 650℃, the aluminized layer prepared at 600℃ is thinner and the heat treatment time is shorter. The thickness of the oxide layer prepared at 700℃ for 10h and 24h in pure O 2 atmosphere is 87 nm and 131 nm. The oxide layer has the microstructure of polycrystalline γ-Al 2 O 3 mixed with amorphous Al 2 O 3 . The sample aluminized at 600℃ and oxidized in pure O 2 atmosphere at 700℃ for 24h has the best deuterium permeation resistance, and the deuterium permeation reduction factor (PRF) in the range of 450℃-600℃ is higher than 5000. The PRF increases with the increase of temperature. The possible reason is that the deuterium permeability of 316LSS substrate increases greatly with the increase of temperature, while that of the coating samples is less affected by the temperature change. The excellent deuterium permeation resistance of the coating is due to the high density of the Al 2 O 3 layer.