Interfacial engineering of inclusions for synergistic toughening and hydrogen embrittlement resistance in high-strength pipeline steels

High-strength pipeline steels are susceptible to hydrogen embrittlement (HE), with inclusions exacerbating this vulnerability. This study employed deoxidation to regulate inclusion/matrix interfacial properties, converting them into functional units that act as deep hydrogen traps and promote acicular ferrite (AF) nucleation. The atomic-scale structure, chemical characteristics, and hydrogen trapping capacity of inclusion/matrix interfaces exhibiting “mosaic” and “core-shell” microstructures were systematically investigated using aberration-corrected transmission electron microscopy and time-of-flight secondary ion mass spectrometry. Results reveal that both oxygen vacancies in inclusion/matrix interfaces and tensile strain fields in the matrix contribute to hydrogen trapping at incoherent interfaces. The TiO/Fe interface in “core-shell” inclusions exhibits stronger trapping capability than Ti₂O₃/Fe interface in “mosaic” inclusions. These interfaces also enhance AF nucleation and grain refinement, improving HE resistance and synergistic toughening. These findings provide a novel strategy for developing HE-resistant high-strength steels by interface engineering.