Role of NbC in enhancing hydrogen embrittlement resistance of the ferritic steels

Hydrogen trapping at the NbC precipitates and its effects on the mechanical properties of the ferritic steels were investigated through combining experimental studies and theoretical modeling. Thermal desorption spectroscopy (TDS) verifies that ∼5nm NbC precipitates in Nb-addition ferritic steel act as effective hydrogen traps, with a hydrogen desorption activation energy of 70.41 kJ/mol. High resolution transmission electron microscopy (HRTEM) reveals the BCC-Fe/NbC interfaces with Kurdjumov–Sachs (K-S) orientation relationship (OR), (0 1) Fe //( 1 ) NbC and [ ] Fe //[0 ] NbC . NbC precipitate simultaneously enhances the mechanical properties and hydrogen embrittlement (HE) resistance. To meet the practical industrial applications, the effects of alloying elements on hydrogen trapping at the NbC/ferrite matrix interface were further investigated by first-principles calculation. First-principles calculations further reveal that low-atomic-number alloying elements (V, Cr) segregated at the K-S OR interface enhance hydrogen trapping ability by increasing interfacial hydrogen binding energy, while high-atomic-number elements (Mo, Ta, W, Re) strengthen interfacial bonding but weaken hydrogen trapping. V segregation at the Fe/NbC interface forms a deeper hydrogen trap with higher detrapping activation energy. Moreover, hydrogen binding energy at the interface is positively correlated with hydrogen Bader charge and Bader volume, providing a quantitative basis for alloy design. This work provides multiscale insights into designing HE resistant steels from an interface engineering perspective.