Are Hydrogen Embrittlement Fractures Always Intergranular?

• Nov 24, 2021

• #2

Guest

mrfailure said:

I came across a claim during literature review for a failure that "HE failures are ALWAYS intergranular"

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With untempered martensite it can be pretty hard to tell by optical metallography. In the practical business of failure analysis I don't think this level of science is essential.
If factors required for EAC are all present - tensile stress, susceptible material, and environment (bad actor + temperature) then it is safe to presume HE mechanism, if other possible mechanisms have been eliminated from consideration.

Certainly 'CrMoV high-strength martensitic steel' and 'fasteners' are among the usual suspects...

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

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• Nov 24, 2021

• Thread starter
• #3

mrfailure

Materials

Aug 7, 2011

817

US

Thanks IM. Conditions appear to be right. I'm still looking into the environment to confirm HE could be induced. One question I am currently chasing down is whether the hydrogen could have been introduced from the thread lube. SEM/EDS suggests a carbon-based oil or grease containing aluminum and calcium.

 

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• Nov 24, 2021

• #4

EdStainless

Materials

May 20, 2004

16,375

Waukesha WI USA

The initial fracture may be intergranular, but once it begins to propagate all bets are off.
You see this is SS with CSCC, mixed mode is very common.

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P.E. Metallurgy, consulting work welcomed

 

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• Jan 25, 2022

• #5

MetallurgistJosh

Materials

Sep 23, 2019

1

US

I agree with ironic metallurgist: it can be very hard to tell with martensite, especially. Another option is to try ASTM F1624 testing using the actual material. It takes a sub-size specimen and determines the threshold for hydrogen embrittlement.

 

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