Are Hydrogen Embrittlement Fractures Always Intergranular?

[mrfailure]

I came across a claim during literature review for a failure that "HE failures are ALWAYS intergranular". I want to know what you think.

Specifics to the situation I am working with: I have fractured CrMoV high-strength martensitic steel fasteners that exhibit quasi-cleavage fracture. Can this morphology form under hydrogen damage?

 

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

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."

 

[mrfailure]

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.

 

[EdStainless]

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

 

[MetallurgistJosh]

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.