Effect of austenitizing and tempering temperatures on hydrogen embrittlement of a Mo–V martensitic steel

This study systematically examined the effects of austenitizing and tempering temperatures on the hydrogen-embrittlement (HE) behavior of a Mo–V martensitic steel. Increasing the austenitizing temperature from 890 °C to 950 °C dissolved coarse undissolved carbides and produced a more homogeneous martensitic matrix, lowering the elongation loss under hydrogen charging from 9.3 % to 2.6 %. Raising the tempering temperature from 620 °C to 680 °C spheroidized plate-like carbides, promoted fine (Mo,V)C precipitation, and reduced dislocation density from 7.2 × 1014 m−2 to 4.6 × 1014 m−2, which collectively decreased elongation loss from 86.0 % to 10.1 %. These microstructural refinements and the formation of stable (Mo,V)C carbides enhanced irreversible hydrogen trapping and improved HE resistance. The results highlight the necessity of coordinated control of austenitizing and tempering schedules to optimize carbide distribution and durability of tempered martensitic steels in hydrogen-rich environments.