HIC, SSCC and SOHIC
HIC, SSCC, and SOHIC are different types of hydrogen-induced damage that can occur in metals, particularly in steel. Here is a table comparing their characteristics:
| Feature | Hydrogen Induced Cracking (HIC) | Sulfide Stress Cracking (SSC) | Stress-Oriented Hydrogen Induced Cracking (SOHIC) |
|---|---|---|---|
| Causes | Hydrogen absorbed during production, operations, or exposure to corrosive environments containing H2S | Exposure to sour environments containing H2S; the presence of sulfides in the steel microstructure | A combination of hydrogen absorption and stress, often in H2S-containing environments |
| Mechanism | Hydrogen atoms migrate to regions of high stress, combine to form molecular hydrogen, and create pressure, leading to cracks | Corrosive hydrogen atoms react with metal sulfides, leading to the formation of cracks under the influence of applied or residual stress | Hydrogen atoms collect along the planes of residual or applied stress, resulting in the development of cracks oriented parallel to the stress direction |
| Crack Orientation | Random, stepwise pattern, typically in the direction of the metal's rolling plane | Can be intergranular or transgranular, but often propagate in the direction of applied or residual stress | Cracks are oriented parallel to the direction of applied or residual stress, often forming multiple crack layers |
| Microstructure Affected | Typically affects the metal at or near the mid-thickness, following the rolling plane | Can affect any part of the metal's microstructure | Primarily affects the mid-thickness of the metal, similar to HIC, but can propagate deeper through the material |
| Prevention | Proper material selection, controlling H2S levels, using low hydrogen welding techniques, and applying coatings or inhibitors | Material selection, controlling H2S levels, using low hydrogen welding techniques, stress relief heat treatment, and applying coatings or inhibitors | Material selection, controlling H2S levels, using low hydrogen welding techniques, stress relief heat treatment, and applying coatings or inhibitors |