Thermochemically synthesized -Al₂O₃ composite coating with high bonding strength and deuterium permeation resistance

Hydrogen isotope permeation in structural steels can cause severe issues, including steel brittleness, fuel loss, and radioactive pollution in fusion reactors. To tackle this issue, we report a simple synthesis of alpha-Al2O3/AlPO4 composite coating by the thermochemical reaction method to serve as an effective barrier hampering hydrogen isotope permeation. This coating was formed at 500 degrees C and composed of alpha-Al2O3 and AlPO4 phases. A relatively uniform and compact structure with thickness of similar to 35 mu m made its corrosion resistance reaching above 3000 times that of the 321 steel substrate. With just one-side coated, the alpha-Al2O3/AlPO4 coating achieved a considerable deuterium permeation reduction factor of 1935 at 450 degrees C, three orders of magnitude higher than 321 steels. What's more, after the deuterium permeation test, no pores or cracks were generated. The excellent bonding between the coating and the substrate was resulted from the formation of CrxPy at their interface induced by Cr diffusion from the substrate. The results obtained from the current study shed new light on seeking reliable and viable ceramic coatings to tackle hydrogen permeation issues.