Roles of microstructural constituents and crystallographic texture on hydrogen-induced delayed fracture behavior in quenching and partitioning steels

Quenching and partitioning (Q&P) steels have attracted considerable interest for automotive applications due to their excellent strength–ductility balance. However, real components undergo complex forming operations, which introduce plastic deformation and residual stress that markedly influence hydrogen embrittlement (HE). Most prior studies have evaluated HE in undeformed specimens, leaving the effect of forming-induced strain and residual stress insufficiently understood. In this study, the hydrogen-induced delayed fracture behavior of two Q&P steels, one comprising a martensitic matrix with retained austenite and the other additionally containing ferrite, was systematically investigated. Cup-forming tests combined with HCl immersion revealed superior delayed fracture resistance in the intercritically annealed Q&P steel, especially along the rolling direction (RD). Kernel average misorientation (KAM) analysis indicated a reduced hydrogen trap density in the RD, and finite element simulations confirmed suppressed stress-driven hydrogen accumulation. Crystallographic texture analysis further demonstrated that recrystallized ferrite grains with a pronounced (111)[1−10] orientation were responsible for the enhanced crack resistance. These findings establish that tailoring ferrite texture provides an effective pathway to suppress hydrogen-induced delayed fracture in Q&P steels and offer a microstructural design strategy for improved HE resistance in formed components.