What is stress oriented hydrogen induced cracking?

What is stress oriented hydrogen induced cracking?

SOHIC is a type of cracking that can easily lead to failure and needs to be mitigated. It is made up of a series of HIC (hydrogen induced cracking) cracks that are stacked perpendicularly in the direction of through wall cracks and driven by high residual or applied stresses.

What is HIC corrosion?

HIC is another type of sour corrosion that occurs especially in carbon and low alloy steels when atomic hydrogen diffuses into the inclusions and trap sites of steel and combines to form molecular hydrogen at inclusions, traps, and void spaces.

What is hydrogen induced cracking test?

In essence, HIC testing is actually an evaluation of the steel for susceptibility to hydrogen embrittlement. The test procedure involves the evaluation of resistance of pressure vessel steel plate and pipework steels to hydrogen reduced cracking caused by hydrogen absorption from aqueous sulfide corrosion.

What causes hydrogen induced cracking?

Overview of Hydrogen Induced Cracking (HIC) Hydrogen Induced Cracking (HIC) is a common form of wet H2S cracking caused by the blistering of a metal due to a high concentration of hydrogen. The blistering damage tends to form parallel to the surface and to the direction of hoop stress.

What causes hydrogen cracking in welds?

Cracking usually occurs at temperatures at or near normal ambient. It is caused by the diffusion of hydrogen to the highly stressed, hardened part of the weldment.

How can you tell if hydrogen is cracking?

Surface-breaking hydrogen cracks can be readily detected using visual examination, liquid penetrant or magnetic particle testing techniques. Internal cracks require ultrasonic or radiographic examination techniques.

What is HIC in welding?

Summary. The presence of hydrogen in the weld metal or HAZ may lead to a form of cracking known as hydrogen-induced cracking (HIC). This form of cracking is also commonly referred to as “hydrogen-assisted cracking” (HAC) or “cold cracking” since it occurs at or near room temperature after the weld has cooled.

How HIC test is done?

HIC test method– NACE TM0284 Element performs HIC testing in accordance with NACE TM0284 by exposing unstressed test specimens to the specified environment saturated with hydrogen sulfide gas at 1 bar pressure for a duration of 96 hours for the standard test.

What does sour service mean?

Sour service occurs when a substance being transported or stored in a vessel has high amounts of hydrogen sulfide or sulfuric acid. From there, the hydrogen sulfide can be oxidized to form sulfuric acid. The sulfuric acid can then lead to corrosion.

How is hydrogen induced cracking ( HIC ) defined?

Overview of Hydrogen Induced Cracking (HIC) Contribute to Definition. Hydrogen Induced Cracking (HIC) is a common form of wet H2S cracking caused by the blistering of a metal due to a high concentration of hydrogen. The blistering damage tends to form parallel to the surface and to the direction of hoop stress.

Is there a threshold for hydrogen induced cracking?

For many steels, a threshold stress exists below which hydrogen induced cracking does not occur. This threshold is a function of the strength level of the steel and the specific hydrogen-bearing environment. Therefore, threshold stress or stress intensity for HIC is not considered a material property.

What’s the difference between Hic and stress cracking?

The HIC may promote one mode of fracture in an alloy rather than another form normally observed in benign environments. Thus, there are a variety of cracking patterns that can be observed; however, hydrogen stress cracking usually produces sharp singular cracks in contrast to the extensive branching observed for stress cracking corrosion (SCC).

What kind of cracking is caused by H2S?

Hydrogen Induced Cracking (HIC) is a common form of wet H2S cracking caused by the blistering of a metal due to a high concentration of hydrogen. The blistering damage tends to form parallel to the surface and to the direction of hoop stress. HIC usually occurs due to the effects…