Efficient deuterium permeation reduction coating formed by oxidizing the Fe-Cr-Al ferritic steel in reduced oxygen atmosphere at 973 K

Alumina is regarded as one of the most promising candidate tritium permeation barrier (TPB).Through thermal oxidization of Al-contained alloys Fe-Cr-Al, alumina layer with high hydrogen isotope permeation reduction ability can be obtained and after bonding with substrate such as reduced activation ferritic/martensitic (RAFM) steels, it can serve as TPB. In this work, efforts have been done to enhance the hydrogen isotope permeation reduction ability of the alumina layer on the Fe-Cr-Al ferritic steel by optimizing the oxidation process. The oxidation temperature of the Fe-Cr-Al ferritic steel was set as 973 K, which is lower than the final heat treatment temperature of the RAFM steel. Three different atmospheres have been employed for the oxidation process of the Fe-Cr-Al ferritic steel. Gas driven permeation (GDP) experiments have been performed to examine the deuterium permeation behavior of the oxidized Fe-Cr-Al ferritic steel. The deuterium permeability of the Fe-Cr-Al ferritic steel oxidized in argon with 100 ppm oxygen is 104 times lower than that of the RAFM steel at 823 K. Oxidation behavior among the Fe-Cr-Al ferritic steel oxidized in different atmospheres has been clarified by analyzing the microstructure and chemical composition of the oxide layer using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) methods. It is suggested that oxidizing the Fe-Cr-Al ferritic steel at reduced oxygen atmosphere could inhibit the growth of the iron oxide and chromium oxide in the oxide layer, thereby leading to a dense and compact alumina layer that has excellent hydrogen permeation reduction performance.