Corrosion of reduced activation ferritic-martensitic steel CLF-1 by Li2TiO3 in ambient air

Abstract

In a solid tritium breeding blanket, tritium breeder Li2TiO3 is in contact with reduced activation ferritic martensitic steel at high temperatures for years and accordingly form a corrosion layer on the blanket structural steel. The effects of the corrosion layer on the deuterium permeability of RAFM steel CLF-1 were thus investigated. X-ray diffraction, secondary ion mass spectroscopy and high-resolution transmission electron microscopy proved the formation of a double layered corrosion products with a thickness of ∼200nm . A localized LiCrO2 (003)/LiFeO2 (003) interface between the outer layer LiFeO2 and the inner layer LiCrO2 was observed. With the increase of corrosion periods (120∼360 h), there is a first deuterium permeability increase due to cracking and an amorphization process occurred at the interface between the corrosion layer and the substrate. The CLF-1 steel corroded for 720 hours performed a lowest deuterium permeation flux as the amorphous oxides have been entirely crystallized. A localized corrosion mechanism coexisting with uniform corrosion was proposed to explain the changing deuterium permeability of the CLF-1 steel corroded by Li2TiO3 in 1 atm ambient air atmosphere. Our study provides a novel thought on reducing the tritium permeability of the RAFM steel.