Evaluation of Hydrogen Trapping Capability at Interfaces Between Vanadium Carbide and Vanadium Nitride Nanoprecipitates with α-Fe by Density Functional Theory

The interface between dispersed compound nanoprecipitates and metal substrates can act as effective hydrogen traps, impeding hydrogen diffusion and accumulation, thus mitigating the risk of hydrogen embrittlement and hydrogen-induced coating failure. In this study, we considered the precipitation of vanadium carbide (VC) and vanadium nitride (VN) nanoprecipitates on a body-centered cubic Fe (α-Fe) substrate in the Kurdjumov–Sachs (K–S) orientation relationship. To evaluate the stability and hydrogen trapping ability of the interface, we used the first-principles method to calculate the interfacial binding energy and hydrogen solution energy. The results show that the stability of the interface was related to the type and length of bonding between atoms at the interface. The interface zone and the interface-like Fe zone have the best hydrogen trapping effect. We found that hydrogen adsorption strength depends on both the Voronoi volume and the number of coordinating atoms. A larger Voronoi volume and smaller coordination number are beneficial for hydrogen capture. When a single vacancy exists around the interface region, the harder it is to form a vacancy, and the more unstable the interface becomes. In addition to the C vacancy at the Baker–Nutting relationship interface found in previous studies being a deep hydrogen trap, the Fe and V vacancies at the α-Fe/VC interface and the V and N vacancies at the α-Fe/VN interface in the K–S relationship also show deep hydrogen capture ability.