Role of vanadium content in hydrogen diffusion behavior in X80 pipeline steel

The role of vanadium content in hydrogen diffusion behaviour in X80 pipeline steel has been investigated. The results show that the hydrogen diffusion coefficient decreases from 1.54 × 10 −6 cm 2 s −1 in 1# steel with 0.03 wt-% vanadium to 9.97 × 10 −7 cm 2 s −1 in 3# steel with 0.14 wt-% vanadium due to the increase in irreversible and reversible traps. With the increase in vanadium content, more vanadium carbides precipitate in tested steels. The length (or number) of the low angle grain boundaries and special grain boundaries increase because of grain refinement, making the number of reversible traps increase. The dynamic condition of diffusible hydrogen in 3# tested steel with the largest number of hydrogen traps is the weakest. To weaken hydrogen-induced cracking dynamic condition, it is recommended to add 0.14 wt-% vanadium to X80 pipeline steel.