Deuterium and tritium are easy to permeate into the fusion reactor internals, and Fe–Al/Al2O3 composite coating can effectively hinder the permeation behavior of hydrogen isotopes. However, the temperature in the preparation process of Fe–Al/Al2O3 coating in many literatures is high, which will affect the mechanical properties of 316 l stainless steel. In this paper, Fe–Al/Al2O3 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 Fe2Al5 and FeAl3 to FeAl and Fe3Al during heat treatment. Compared with the aluminized layer prepared at 650 °C, the aluminized layer prepared at 600 °C is thinner and the heat treatment time is shorter. The thickness of the oxide layer prepared at 700 °C for 10 h and 24 h in pure O2 atmosphere is 87 nm and 131 nm. The oxide layer has the microstructure of polycrystalline γ-Al2O3 mixed with amorphous Al2O3. The sample aluminized at 600 °C and oxidized in pure O2 atmosphere at 700 °C for 24 h has the best deuterium permeation resistance, and the deuterium permeation reduction factor (PRF) in the range of 450 °C–600 °C is higher than 5000. The PRF increases with the increase of temperature. The possible reason is that the deuterium permeability of 316 LSS 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 Al2O3 layer.
This paper describes the development of a Fe-Al/Al2O3 coating that effectively blocks the permeation of hydrogen isotopes like tritium into fusion reactor components. The coating is prepared at low temperatures (700°C or less) to preserve the mechanical properties of the 316L stainless steel substrate. The coating has a dense Al2O3 layer that provides excellent tritium/deuterium permeation resistance, even at high temperatures.