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Contamination of P91 Material By Carbon Steel

Contamination of P91 Material By Carbon Steel

Contamination of P91 Material By Carbon Steel

(OP)
Can anyone give me some more detailed information on the phenomenon of carbon contamination of P91 material when it comes into contact with carbon steel (e.g. when carbon steel is used to lift P91 material, some of the carbon steel material gets embedded into the P91 material).  Specifically, what happens to the microstructure of the P91, and what are the results of this kind of contamination?

RE: Contamination of P91 Material By Carbon Steel

It isn't carbon contamination, it is Fe contamination.  The embedded Fe in the surface corrodes very easily.  These locations can provide sites for the easy initiation of corrosion attack.

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Rust never sleeps
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RE: Contamination of P91 Material By Carbon Steel

(OP)
EdStainless:  Thanks for the response.  It is also possible that, if the contamination takes place prior to fabrication and PWHT that the carbon can react with the Cr in the P91 forming chromium carbides during PWHT at the contamination sites and alter the P91 material property?

RE: Contamination of P91 Material By Carbon Steel

(OP)
EdStainless:  Sorry, my previous post was supposed to be a question and not a statement.

RE: Contamination of P91 Material By Carbon Steel

I had never heard of carbon contamination of P91, but that doesn't mean it isn't possible. Sounds like the fabricator is on a fishing expediton to deflect criticism of their fab procedures and blame the erector.

What sort of microstructural changes have you detected? If you completed a hardness traverse and plastic film replication and found ferrite instead of martensite, then it is not carbon contamination, but fabricator education that is the root cause.

RE: Contamination of P91 Material By Carbon Steel

I concur with davefitz. Using iron contamination for an iron-base alloy steel is indeed a fishing expedition. There are no issues.

RE: Contamination of P91 Material By Carbon Steel

Concur with davefitz and metengr. Surface decarburization due to the multiple thermal treatments seen in P91 fabrications is of more concern. Carbon will not be added during heat treatment in oxidizing environments; it will be subtracted.

RE: Contamination of P91 Material By Carbon Steel

The only chance to add carbon is if the parts are heavily contaminated with oil or grease going into HT.
I would be more worried about oxidation/decarb damage in this grade also.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

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