Hydrogen-induced cracking (HIC) is a hydrogen embrittlement phenomenon that occurs in a line pipe exposed to the sour environment. Generally, the initiation site of HIC is estimated by observing the fracture surface after the test. It is reported that typical initiation sites of HIC are non-metallic inclusions, such as elongated MnS, in the center segregation region. However, there is no in-situ observation technique that can establish a direct link between the initiation site and inclusion. In this study, an in-situ HIC measurement technique was developed to observe HIC initiation behavior and identify the initiation site of HIC. This technique is based on the combination of an automatic ultrasonic wave inspection (UT) system and energy dispersive X-ray spectroscopy (EDS). By overlaying the C-scan movie obtained using the UT system on the EDS map of the HIC fracture surface, as in projection mapping, the initiation site of HIC was related to the non-metallic inclusion directly. Additionally, the hydrogen concentration at the HIC initiation site was calculated using finite element analysis, whereas the critical hydrogen concentration (Cth) was obtained as the hydrogen concentration at the time of HIC initiation.

Subject
Hydrogen induced cracking, Energy dispersive X-ray spectroscopy, Steel surfaces, Materials, Hydrogen permeation, Hydrogen concentration, Permeability, Crack initiation, Fracture surfaces, Steel, Hydrophobic interaction chromatography, Hydrogen, Inclusions
Keywords:
Sour environment, Hydrogen-induced cracking, Inclusion, Hydrogen, Line pipe
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2022
Association for Materials Protection and Performance (AMPP)
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