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Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals.
Hydrogen embrittlement may occur as a side effect of electroplating processes. Delayed failure is the fracture of a component under stress after an elapsed time, is a characteristic feature of hydrogen embrittlement (2). Hydrogen entry into the material may be effected during plating, pickling, phosphating, melting, casting or welding.
Cold cracking—also known as delayed cracking, hydrogen-assisted cracking (HAC), or hydrogen-induced cracking (HIC)—is a type of defect that often develops after solidification of the weld when the temperature starts to drop from about 190 °C (375 °F); the phenomenon often arises at room temperature, and it can take up to 24 hours to appear even after complete cooling. [8]
Different types of crack growth (e.g. fatigue, stress corrosion cracking, hydrogen embrittlement) produce characteristic features on the surface, which can be used to help identify the failure mode. The overall pattern of cracking can be more important than a single crack, however, especially in the case of brittle materials like ceramics and ...
The exact mechanism that causes hydrogen embrittlement is still not determined, but many theories are proposed and are still undergoing verification. [1] Hydrogen atoms are likely to diffuse to grain boundaries of metals, which becomes a barrier for dislocation motion and builds up stress near the atoms.
Resistance to hydrogen and environmental embrittlement. In cast irons (from 250-550 HBW) these improvements include: Higher ductility and impact resistance for a given hardness, A low-distortion, repeatable dimensional response, Increased fatigue strength, Increased wear resistance for a given hardness.
High temperature hydrogen attack (HTHA), also called hot hydrogen attack or methane reaction, is a problem which concerns steels operating at elevated temperatures (typically above 400 °C (752 °F)) in hydrogen-rich atmospheres, such as refineries, petrochemical and other chemical facilities and, possibly, high pressure steam boilers.
The hydrogen production process also mechanically weakens the rods cladding because the hydrides have lower ductility and density than zirconium or its alloys, and thus blisters and cracks form upon hydrogen accumulation. [4] This process is also known as hydrogen embrittlement. It has been reported that the concentration of hydrogen within ...