Cut out all the welds.
First of all the PWHT is completely different for these materials.
When you do a dissimilar weld you get a carburized zone on the side of the high chromium and a decarburized on the low chromium content side.
The carburized side will exhibit high hardness and the decarburized low hardness and tensile strength.
Further more material such as p91 are very sensitive to PWHT. If not done properly you risk PWHT the material without having completed the austenite to martensite transformation. This will result in not-annealed martensite with extremely high hardness.
Honestly there are so many scenarios. Rejection of the welds is the only option, at least for the ones welded with b9 (p91) consumables.
Further more what about gas backing? Some weld p22 without purging, this however is a big no-no for p5, p9 and p91.

 

Hi
Thanks for your reply.
I was also thinking same for the welds which are welded with B9 filler rods.

However I would like to share some more information about the welds which are done using either ER80S-B2 or ER80S-B6 filler rods.The base metal is ASME SA P22 for all the welds. We have conducted hydro test,1.5 times design pressure and results acceptable. We have also performed RT and results are acceptable. Shielding gas used is Argon. Nominal chemistry of both these filler rods is different than the base metal. In long run how these welds will behave ? Can you suggest something. Do you think in any scenario we should not accept these welds ?

 

The fact that NDT, hydro etc were acceptable gives absolutely no information on the creep behavior.
Dissimilar welding in creep resistant steels always involves some kind of compromise. These areas are few and identified.
In your case all the joints are essentially dissimilar welds. This will have an impact in the life of the equipment as creep will begin early for all these joints.
You could risk it and proceed with accepting the welds but considering your subcontractor messed up so bad I would not have any faith in him doing all the other stuff properly (pre-heat, pwht etc).
Furthermore if you accept the welds you are responsible if repairs have to be made a lot earlier and the remaining life of the unit is considerably reduced.
If I was the responsible welding coordinator or the client I would simply reject all the welds. I understand that the cost and the delay in time would be great but I would back-charge this to the subcontractor.

 

Improperly welded chrome piping will fail over time. It may hydro, pass xray, and be pwht but it will be unpredictable once introduced to service stress. Weld procedures are in place for a reason. Cut the welds out.

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