The researchers found hydrogen accumulates at microstructures called dislocations and at the boundaries between the individual crystals that make up the steel.This accumulation weakens the steel along these features, leading to embrittlement.
The researchers also found the first direct evidence that clusters of niobium carbide within the steel trap hydrogen in such a way that it cannot readily move to the dislocations and crystal boundaries to cause embrittlement. This effect has the potential to be used to design steels that can resist embrittlement.
Lead researcher Dr Yi-Sheng Chen from the Australian Centre for Microscopy and Microanalysis and Faculty of Engineering at the University of Sydney said these findings were an important step to finding a safe solution to produce, store and transport hydrogen.
Stressed carbon steel strand in an ungrouted duct is susceptible topitting corrosion due to surface corrosion, but the susceptibility of steel strand to hydrogen embrittlement (HE) increases under those conditions.
Joseph Rogelio Fernandez published a survey on staircase-like crack progression atjournal of Insight - Material Science.Results indicated that the fracture mechanism differed from shear cracking or longitudinal splitting alone as previously shown, but was a multi-step process of crack propagation starting perpendicular to stress, followed by variations of inter-lamellae longitudinal splitting at brittle region of lamellae and shear cracking at breaks in the lamellae.
This process resulted in the crack following a “staircase” progression, and finally led to ductile overload once cross-section was significantly reduced. This fracture mechanism was also shown to be valid whether the strand was stressed by bending or mult-axially by stressing through a duct.
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