Effect of Cold-Rolling on Hydrogen Diffusion and Trapping in X70 Pipeline Steel

Abstract

In this investigation, we prepared samples with five different grain misorientations by cold-rolling an X70 pipeline steel plate. The hydrogen permeation and hydrogen visualization experiments were used to compute the diffusion parameters and to reveal the diffusion path in steel samples. The dual-polarized permeation experiment allowed us to show that permeability and effective diffusion coefficient were decreased with an increase in misorientation. Hence, the total and irreversible trapping sites were also raised with the extent of deformation in the steel. On the other hand, the visualization study permitted us to show that hydrogen diffusion intensity changes within the microstructure. The diffusion intensity increases in the order of non-deformed grains, grain boundaries, and deformed grains with deformed grains as the easiest path for hydrogen diffusion.