کلیدواژهها
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Hydrogen induced cracking, Inclusions, Pipeline steel, Synchrotron radiation, 3D imaging
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چکیده
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Environmental conditions of service affect the resistance of pipeline steels to failure, as a result, the applied
stress which would be otherwise considered safe can be responsible for fracture due to hydrogen induced
cracking (HIC). The presence of hydrogen sulfide in natural gas is one of the main sources of hydrogen in steel.
HIC testing showed that cracks initiated from inclusions and propagated through the steel matrix along the crack
path that was occupied by inclusions. The number of inclusions and the distance between them as well as the
grain size between them was considered to be important for predicting failure. Shorter distance between inclusions
and smaller grains were found to facilitate HIC propagation. The hydrided specimens were subjected to
tensile stress until failure to generate stress-strain curves, ductility and toughness data. It was revealed that even
though most of the cracks initiate from rectangular and spinel inclusions, the globular inclusions have also
contributed to reducing the tensile strength, ductility and toughness. Synchrotron radiation 3D imaging of steel
structure was used to explain the features of the HIC cracks formation during tensile tests.
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