Preparation and properties of FeAl/Al2O3 composite tritium permeation barrier coating on surface of 316L stainless steel

Abstract

In fusion reactors, preparing barrier coatings on the surface of steel structures is one of the most effective ways to reduce the penetration of hydrogen and its isotopes. An FeAl/Al2O3 composite tritium permeation barrier is a good choice for the current tritium permeation prevention technology because it has low enthalpy permeability, small thermal mismatch, good compatibility with lithium lead, and metallurgical bonding. In this study, FeAl/Al2O3 composite tritium permeation barrier coating was successfully prepared on the surface of 316L stainless steel by embedding method combined with in-situ thermal oxidation. By using test methods, such as TEM, SEM, EDS, and XRD, we found that the FeAl alloy transition layer was successfully formed on the surface of the aluminized matrix, thereby effectively relieving the thermal mismatch between the Al2O3 coating and the substrate. The results showed that the thickness of the aluminum-rich layer and the FeAl transition layer on the surface of the substrate were approximately 32 μm and 8 μm, respectively. In addition, α-Al2O3 layer formed on the surface of the aluminum-rich layer after oxidation was approximately 4 μm thick. According to the scratch test, the bond strength of the coating showed that the adhesion of the FeAl/Al2O3 composite coating was 52.4 N. The hydrogen permeation test results showed that the FeAl/Al2O3 composite coating remarkably improved the hydrogen barrier properties of the 316L stainless steel matrix.