Hydrogen interaction characteristic of nanoscale oxide films grown on iron–nickel based stainless steel by selective thermal oxidation

Abstract

Hydrogen isotopes, the reaction ingredients in the nuclear fusion plant, can easily permeate through the stainless steel (SS) substrate, leading to the so-called hydrogen degradation. Generally, a widely accepted way to reduce the hydrogen permeation is to prepare a barrier coating on the substrate. Nevertheless, the coated layer has the inherent problem of incompatibility with the heterogeneous base materials. In this work, in-situ selective oxidation was used to explore the optimal oxides with the improved hydrogen resistance. Two types of layers thermally formed at 450 °C and 750 °C, respectively, were selected to investigate their hydrogen interaction characteristics. Comprehensive analyses, including Raman spectra, XPS, EIS and AES, indicate that the oxide formed at 450 °C is a better candidate of hydrogen permeation barriers, probably due to the formation of protective layers of chromia and FeCr2O4, while the oxides obtained at 750 °C, though exhibiting a much more stable phase, can rarely reduce hydrogen diffusion through the shortcuts of defects. This finding provides a potential new way to prepare a hydrogen permeation barrier.