Hydrogen embrittlement behavior of tempered martensitic Ni–Cr–Mo low-alloy steel subjected to normalizing and annealing

This study investigates the hydrogen embrittlement behavior of tempered martensitic Ni–Cr–Mo low-alloy steel subjected to normalizing and annealing. Specimens were fabricated using three different heat treatments: quenching and tempering (QT), normalizing before quenching and tempering (NQT), and normalizing, annealing, quenching, and tempering (NAQT). Microstructural analysis revealed that NQT steel exhibited a refined and homogeneous microstructure, which led to the highest hydrogen embrittlement resistance. Thermal desorption analysis results indicated higher hydrogen content in the NQT and NAQT steels compared to QT steel. However, coarse intergranular carbides in NAQT steel facilitated localized hydrogen trapping, thereby reducing its hydrogen embrittlement resistance. These findings underscore the importance of optimizing heat treatment processes to enhance hydrogen embrittlement resistance in tempered martensitic steels.