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HIC

HIC: Hydrogen Induced Cracking
Definition:Material cracks initiated by atomic hydrogen. It is also known as hydrogen embrittlement.
Explanation:Hydrogen atoms are highly mobile within metals. They not only accommodate themselves in interstitial sites, but also accumulate locally in lattice defects, such as grain boundaries, dislocation strain fields, inclusions, etc. The materials are mechanically degraded when a critical amount of hydrogen is reached and crack initiates. The sources of hydrogen are various metallurgical, manufacturing, and application processes, such as pickling, galvanizing, welding, corrosion, and so on.

Depending on the material, hydrogen source and application condition, a number of HIC mechanisms have been proposed: such as hydrogen induced blisters, hydrogen pressure theory, hydrides formation theory, hydrogen enhanced localized plasticity, hydrogen enhanced decohesion, and so on. The important factors for HIC are suggested to be: susceptible materials, local stresses, and hydrogen concentration. The degradation process is complex because it is influenced by a bundle of interactive factors and cannot be explained by any single mechanism.
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Internal Hydrogen Assisted Cracking (IHAC) and Hydrogen Environment Assisted Cracking (HEAC) as distinguished by the source of offending hydrogen.
SFB-Link:High Mn steels are known to be susceptible to HIC. The underlying fracture mechanisms have been investigated on specimens after mechanical testing in combination with ab initio calculation of hydrogen interactions with different lattice defects, deformation mechanisms and fracture analysis.
References:ASTM F1459-06 .
ASTM G142-98.
NACE Standard TM0284.
ASTM STP 543.
ASTM STP 962.
R.P. Gangloff, Hydrogen assisted cracking of high strength alloys. Comprehensive Structural Integrity 6 (2003) 1-194.
Xiaofei Guo, Influences of Microstructure, Alloying Elements and Forming Parameters on Delayed Fracture in TRIP/TWIP-Aided Austenitic Steels, RWTH Aachen, 2012 (Dr. -Ing. Diss).