Abstract
FeCrAl alloys are promising accident-tolerant fuel (ATF) cladding materials for applications in light water reactors (LWRs). Despite the excellent mechanical and antioxidation properties, this series of iron-based alloys has poor hydrogen embrittlement (HE) resistance due to the strong hydrogen uptaking ability. The hydrogen embrittlement effect can cause the degradation and premature failure of the material, and this effect can be enhanced by the high-temperature/high-pressure/high-irradiation environment in reactors. So, the potential danger should be taken seriously. In this paper, we have studied the hydrogen atom and molecule adsorptions on both Fe (100) and FeCrAl (100) surfaces to discover how the hydrogen atom and molecule (H/H2) interact with the Fe and FeCrAl (100) surface in the first place. The results show that there are strong element effects on the FeCrAl surface. The Al atom itself has no interaction with hydrogen. When the Al atom is beside the Fe atom, this Fe atom has a slightly lower interaction with hydrogen. However, the Al atom beside the Cr atom will enhance the hydrogen interaction with this Cr atom. On the other hand, when the Cr atom is beside the Fe atom, these two atoms (Fe–Cr bridge site) can reduce the interactions with H. In addition, when two Cr and two Fe atoms together make a four-fold site (FF site), the two Cr atoms can increase the interaction of the two Fe atoms with H. The element effects discovered can be a good guide for making hydrogen prevention coatings.
Highlights
Hydrogen embrittlement (HE) can cause a reduction in the tensile strength, ductility, fracture strength, and toughness of materials (Shen, 2010; Seki et al, 2012; Dwivedi and Vishwakarma, 2021)
All the first-principle calculations were performed to investigate the hydrogen adsorption on the FeCrAl alloy and pure iron (100) surface with different preadsorbed sites based on spin-polarized periodic density functional theory (DFT) (Hohenberg and Kohn, 1964; Kohn and Sham, 1965) using Vienna Ab-initio Simulation Package (VASP) (Kresse and Furthmüller, 1996)
EH2FeCrAl indicates the energy of the slab after H2 adsorption, EFeCrAl is the energy of the slab before H2 adsorption, and EH2 represents the energy of a single H2 molecule
Summary
Hydrogen embrittlement (HE) can cause a reduction in the tensile strength, ductility, fracture strength, and toughness of materials (Shen, 2010; Seki et al, 2012; Dwivedi and Vishwakarma, 2021). Due to the high mobility and chemical reactivity, the hydrogen atoms would permeate the surface and tend to aggregate inside the materials at defects, dislocations, voids, grain/ phase boundaries, microcracks, precipitates, interfaces, and so on The aggregated hydrogen atoms may form brittle hydrides with the alloy compositions and form hydrogen molecules again (Dwivedi and Vishwakarma, 2018). All these together will cause the local swelling and formation of microcracks. The AIDE mechanism had been proposed in the 1970s It hypothesizes that hydrogen at the crack tip will accelerate the dislocation emission. The HESIV mechanism suggests that hydrogen promotes the aggregation of vacancies to make microvoids, decreasing the ductility of materials
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