Hydrogen embrittlement poses a significant barrier to the widespread adoption and commercial viability of high/ultra-high strength steels [1,2]. In this study, the comparative impact of iron carbide, Niobium carbide (NbC), and vanadium carbide (VC) on the hydrogen embrittlement (HE) resistance of an advanced direct quenched and partitioned (DQ&P) steel is investigated. Through comprehensive analysis, we explored the hydrogen uptake levels and their consequential impact on the mechanical properties of DQ&P steel containing martensite laths, interspersed by fine film-like retained austenite (Figure 1), with or without the presence of different types of iron carbides, NbC, and VC. Employing advanced techniques such as thermal desorption spectroscopy (TDS), slow strain rate tests, hydrogen permeation tests, atom probe tomography, we unravel the hydrogen trapping capacity of different carbides, retained austenite and the underlying micro-mechanisms behind the HE sensitivity.

Furthermore, employing density functional theory (DFT), we investigate the interplay between the carbide-matrix interface and hydrogen trapping dynamics. DFT simulations illustrate that NbC exhibits a superior hydrogen capture force compared to VC and iron carbide, suggesting its potential for enhancing HE resistance. DFT predictions further corroborate the experimental results, particularly concerning the atom probe tomography. In essence, our study not only advances the fundamental understanding of HE in DQ&P steel, but also paves the way for the design of next-generation steels with unparalleled resistance against HE.