F53 Duplex Sigma Phase Formation

[metmike]

Hi everyone,
I have another similar problem with the notorious F53 Duplex SS. I had 3" OD forgings of different shapes. They were processed as follows:
Close Die Hammer Forged @ ~2235-2250 F, then water quenched.
Annealed @ ~2015 F for 2 hours, then water quenched.

Two of the shapes passed mechanical testing and had no intermetallic sigma phase from the microstructure exam. But one shape did.
I am not sure why this one formed intermetallics, but the other two were fine.

Any specualtons/suggestions as to why this may have happened would be appreciated. I can try to provide any further info you may need.
I was also wondering if it was possible and worth re-annealling the failed shape to try and remove the intermetallic phase.

Please let me know. Thank you!

 

[metengr]

Sounds like a process problem/breakdown either related to cooling after forming or someone missed the solution anneal after forging. It can happen despite what others may say/think. You have the evidence.