UNS N08926 Alternative Material

[EStilli]

Hi guys, I have this question:

my client is asking for ball valves with CS body and 6MO (UNS N08926) trim.
Having valves up to 42", no vendor would never supply any integral N08926 ball! So I'm ready to expect deviations, for sure manufacturers will propose the ball in CS + 3mm cladding in...

...and here is the question: it is my understanding that UNS N08926 cannot be cladded, so, what cladding material can I accept as substitute? Alloy 625? Alloy 825? Any other?

Datas: Rating: 150, 300, 600. Pipelines for gas (ASME B31.8) and liquid (ASME B31.4) for SOUR Service (but I don't know neither H2S partial pressure, neither pH, neither chlorides concentration). Max Temp: 100 °C.

Thank you for your help.

 

[metengr]

Since you have little service information to go on and to match the above, I could see several options to overlay the ball -

ERNiCrMo-3 or
ERNiCrMo-13

 

[EStilli]

Hi metengr,
just to understand: for "overlaying the ball with ERNiCrMo-3" it is what I mean for "overlaying, or cladding, the ball with Inconel 625"?
So, when a manufacturer states that he offers a ball in CS + "3 mm clad in Inconel 625" more specifically, he is applying layers of ERNiCrMo-3 to the ball?
Thank you very much for this clarification!

 

[metengr]

Yes, EStilli.

 

[EdStainless]

First of all any of the 6%Mo alloys should do, there are a few.
Secondly, it they are doing weld overlay then the working surface should be required to meet the desired chemistry. This probably mans three layers of weld overlay, 309 plus two of the 6%Mo or Ni based alloy.
Or you can take the tack of trying to prove that you have the correct corrosion resistance in whatever overlay you have. (625 weld overlay has poor corrosion resistance due to severe segregation)

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Plymouth Tube

 

[JamesCKelly]

6%Mo grades such as N08926, a.k.a. Cronifer 1925hMo, are normally welded with 625 (ERNiCrMo-3) so that, in spite of Mo segregation, the weld bead will still meet corrosion resistance of the base metal.

Other 6Mo stainlesses, which may be more available in the size and product form you need, include AL-6XN (N08367) and 254 SMO (S31254).

The best, perhaps overkill, weld filler for such materials is, to my knowledge, INCO-WELD 686CPT (ERNiCrMo-14). Nevertheless, most 6%Mo stainlesses over the last quarter century have been welded with ERNiCrMo-3.