A deuterium permeation barrier by hot-dipping aluminizing on AISI321 steel

Reducing the tritium permeation through structural materials is one focused issue in the International Thermonuclear Experimental Reactor (ITER). To achieve the target, the hot-dipping aluminizing (HDA) method is suggested for its potentials in applications. But low permeation reduction factors (PRFs) were often appeared on the coatings by HDA for through defects or visible cracks. In this work, we presented a deuterium permeation barrier coating with high PRF prepared by HDA method and subsequent oxidation, on AISI321 steel vessel sample. The external surface of the sample was protected by oxide passivation, inert atmosphere and molten salt before dipping in Al liquid at 1023 K for 30 min. Then the sample was oxidized at 1123 K in air for 4 h and at 1023 K in 10 ml/min Argon flow for 15 h. Four layers of the aluminide coating were obtained after HDA and oxidation processes, including Al2O3, Al, FeAl, and Fe3Al. High PRF values were achieved as 2530 at 773 K, and 790 at 823 K, through the aluminide coating.