Yes provided the initial pass(es) is made with GTAW or GMAW with ER NiCrMo-3 filler metal and inert gas backing.

Depending on clad thickness and overall thickness sometimes multiple passes are made with the high alloy filler.

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Do you mean Alloy 625 or 825? Either way I would normally use ERNiCrMo-3 as a minimum.If the cladding were 625, I might use a superior corrosion resitant Ni-based alloy filler metal.

Thanks for response, what could be reason then some of the client ask for buttering with Alloy 625 or 825 on weld bevels on both sides prior to girth welding using E-NiCrMo-3(Alloy825) electrode.

Or can we weld first with ENiCrMo-3(Alloy 625) electrode for root and hot pass(considering cladding thickness is 3mm) followed by CS electrode for CS backing material.

You can try a hybrid procedure, with or without a buffer layer between the CRA and the CS, but it will more than likely fail qualification testing.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

The client is simply being more conservative in its approach to assuring a properly corrosion resitant weld is achieved. In my 45+ years experience, I have never seen such a client requirement and we always welded out with the appropriate Ni-based alloy filler metal. In thefield r in our shop, I would never permmit the hybrid procedure. There is too much potential for error leading to weld metal cracking.

I have usually seen these done with a hybrid procedure.
But passing the corrosion tests is very dependent on the heat input in the CS welds.
Too much heat can be bad.
Make sure that your alloy passes extend deeper than the clad by a good amount.
When you can get at both sides they usually weld the CS root and second pass first, then grind the alloy side and finish out the alloy welds, and then finish the CS welds.

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P.E. Metallurgy, consulting work welcomed