HIC Testing-Circumstance that call for HIC test? 3

[bmoorthy]

1)Under what circumstance one has to call for HIC test in a material.

2)Is HIC test unique for Plate form or Pipes made from Plate?

3)Is it true that Forgings do not require HIC test?

4)Under what circumstance one calls for HIC test in a forging.

5)Where as for SSC/SCC test there are conditions under which one find out whether SSC test/Scc test is required or not (MR0175), But as regards HIC test there are no such tables or conditions readily available. Are there API/NACE publications that specify the conditions under which HIC test is recommended?

6)It is also beleived that in Clad plates (SS or Inconel/Incoloy)or Overlayed components HIC tests are not required for base material. Is it true.

7)Is HIC test unique to CS or Low Alloy material. Are High Alloy material exempted from HIC test?

 

[kenvlach]

Interesting question. I am not familiar with API codes, but have some general metallurgical comments. Hydrogen (and/or hydrogen sulfide) causes different types of damage in different materials. So, different tests for different materials & environments.

For the lower strength steels commonly used in pipe and plate, hydrogen induced cracking (HIC) occurs when hydrogen atoms diffuse to internal defects and inclusions (voids, sulfide, carbide) where it forms molecular gases (H₂, CH₄, H₂S). This creates internal pressure which can cause blistering and failure without any applied stress. The surface corrosion is a means for hydrogen to enter the metal. HIC vulnerability decreases as the steel's strength increases. Thus, HIC testing for 96 hours w/o any applied loading per NACE TM0284 is used.

Higher strength steels are vulnerable to hydrogen embrittlement (HE), where interstitial hydrogen atoms can cause damage w/o forming molecular gas. It greatly lowers the ductility of the steel under applied loading. Martensitic lattices are especially vulnerable. Corrosion isn't necessary for the 'pure' form of HE (unaccompanied by corrosion), also known as mechanical HE. Thus, high strength fasteners are tested under applied load per ASTM F519 or F1624.

Sulfide Stress Corrosion Cracking (SSCC) is a combination of HE and SCC, where H₂S in a corrosive, wet environment is the source of the hydrogen. Vulnerability increases with steel strength and applied load. Corrosion is involved, so a longer testing period. Thus, testing per NACE TM0177 is performed under an applied load for 30 days (hence, $$$).

You already know applications requiring SSCC testing. Suggest posting your HIC question on the API forum – forum809 Give the material & strength of the forging; (probably HIC testing if lower strength steel, SSCC if higher strength, but I don't know the dividing point).
Also, if you are in Middle East or South Asia, maybe this lab can help:

http://www.tcreng.com/

 

[SJones]

1.
Under circumstances where the user deems that the H2S content of fluids in contact with the material and the operating conditions may give rise to a HIC failure mode.

2.
No. It can be applied to any product form from which suitable test pieces can be machined. It is, principally, a test for "flat rolled steels or their products" as per ISO 15156-2 Table B.3 but can be applied to seamless pipe (see ISO 3183-3).

3.
It has become an established practice to forego HIC testing of carbon steel forgings subject to the sulphur content of the forging being restricted to a maximum of 0.025 wt% (see EFC 16)

4.
See 3 above.

5.
ISO 15156-2, Clause 8.

6.
If the principal purpose of the cladding, or overlay, is corrosion protection; the appropriate materials have been selected; and the user is satisfied with the integrity of the surface, then HIC testing of the carbon steel substrate could be viewed as being superfluous.

7.
HIC, as defined in ISO 15156, is not a failure mechanism of CRA materials.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/