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Abstract: An iron-aluminide and alumina tritium barrier coatings prepared by the high-activity pack-aluminizing and controllable pre-oxidizing processes have been investigated in this paper. A uniform iron-aluminide layer with Al content about 30wt% and thickness between 15 and 25μm was formed on the 316L samples at a temperature lower than 1043K. A surface alumina film with thickness about 200–500nm was selectively formed by pre-oxidizing the iron-aluminide layer. The 316L tube coated and oxidized only one side with the inner surface of Fe–Al and alumina composite coating achieved a Tritium Permeation Reduction Factor (TPRF) more than 3000 in the gas phase tritium permeation test. [Copyright &y& Elsevier]

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe 2 Al 5 layer was formed on CLAM substrate by pack cementation process with Fe 2 Al 5 donor powder and NH 4 Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe 2 Al 5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe 2 Al 5 as a function of processing parameters. The Wagner’s equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al. [ABSTRACT FROM AUTHOR]