Abstract
The hydrogen-induced cracking (HIC) susceptibility of the X80 steel in H2S environment and its heated-treatment microstructure was evaluated. The field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and energy dispersive spectroscopy (EDS) were employed to study the morphology and chemical composition of the inclusions, precipitates and HIC cracks in the X80 steel. The hydrogen trapping efficiency was investigated by measuring the permeability (J ∞L) and the apparent diffusivity (D app). The results showed that heat-treated specimens had lower trapping efficiency, but were more susceptible to HIC. Most of the HIC cracks initiated from the inclusions rich in Mn, Al, Ca, and Ti, and propagated transgranularly in the original and air cooled specimens, but mainly intergranularly in water quenched specimens.
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