Study on the Hydrogen Isotope Permeation Behaviors of the FeAl/Al₂O₃ Composite Coating

Experiments on deuterium permeation through S.S.316L with FeAl/Al₂O₃ composite coating have been performed in the temperature range 277-600°C at driving pressures 1-50kPa. As comparison, the tests for samples with natural oxidation film and Ni-plating have also been performed. The apparent deuterium permeability in the sample with FeAl/Al₂O₃ coating is an order of magnitude lower than that with natural oxide layer, and is at least three orders of magnitude lower than that in the non-oxidized material by inference. The apparent activation energy of deuterium permeation is 76.6kJ/mol for the coated sample and 61.3kJ/mol for the sample with natural oxidation film. The exponential dependences of steady flux for the samples on the pressure are 0.89 for FeAl/Al₂O₃ coating, 0.65 for natural oxidation film, and 0.55 for Ni-plating, that reflects different permeation mechanism for various surfaces. In addition, the trapping effect of defects on hydrogen isotope was inferred according to the different characteristic of permeation flux curves for various samples.