Banded ferrite–pearlite X65 pipeline steel was tested in high pressure hydrogen gas to
evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test
specimens were oriented in the steel pipe such that cracks propagated either parallel or
perpendicular to the banded pearlite. The ferrite–pearlite microstructure exhibited
orientation dependent behavior in which fatigue crack growth rates were significantly lower
for cracks oriented perpendicular to the banded pearlite compared to cracks oriented …