hardness testing of 2205 Stainless

[donnaj]

We have parts manufactured from 2205 Stainless. The MTR shows the hardness at 22 RC. The welded parts were sent to be solution annealed after manufacturing. There are 2 separate parts both manufactured from the same bar stock - same heat. After solution anneal - the hardness is 26 RC on one part and 35 on the other. These were annealed at 1850 F for 1 hour and water quenched. These parts are going into H2S Service and must be suitable per NACE MR0175. We are trying to think of any reason for the large difference in the hardness range. If anyone has any suggestions or ideas we would appreciate any input.

Thanks

 

[EdStainless]

The hardenss test was done wrong.
Or the anneal temp was actually too low and/or the quench was delayed and intermetallics formed.

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Plymouth Tube

 

[Guest102023]

EdStainless,

I don't question your comments, but can intermetallics be responsible for such high hardness?

I would be interested in some good references on 2205 metallurgy, especially things that go wrong in welding the stuff (beyond the usual ACOM collection).

 

[remetaper]

Even if t=1820 is low ( t=1900 is more right ), Hrc =35 is high for a 2205 grade.
I agree with Edstainless because ,even with intermetallic phases in the structure, in order to reach Hrc = 35 , it means to have strongly "aged " by a soaking at certain risky temperature obtaining a large amount of intermetallic. And ,also in event of this situation Hrc =35 is still high.
Donnaj said a water queching was done presuming a rapid cooling.
Suspicion : are you sure that second part (Hrc =35) is 2205 ?

 

[EdStainless]

A few hours at the critical temp might get you this hard.
More realistically the hardness test is wrong.
Surface condition, sample prep, or some such thing.

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Plymouth Tube

 

[metengr]

Hardness testing should be re-visited because the typical is
256 HB. I don't believe the intermetallics are going to enable you to reach this level of reported hardness. Besides, the drop in toughness would be the obvious effect from intermetallics.

 

[mrfailure]

Given this discussion, I wonder if you would see any difference between the two structures in a mounted cross-section. Also, are there differences in microhardness between ferrite and austenite phases if both samples turn out to have similar structures?

Aaron Tanzer

http://www.lehightesting.com