TTS weld failure in shell and tubes exchanger - duplex tubes

[ALIIM99]

Hi All,
we have gone thru a tube to tubesheet weld failure causing many joints leak for shell and tube reactor (steam generator). steam in shell side and gas in tube side.

tube made duplex SS (UNS 32205) and tubesheet is low alloy 1.25cr-0.5Mo with Ni82 overlay. so, the failed weld is between duplex tubes and nickel 82 clad (welding filler is Ni82).

I came to know thru many reading and technical discussion that such welding combination is not recommended as there is a high chance of forming intermetallic components and affecting toughness and corrosion properties (reference API 582).

Any previous experience or input is appreciated!

 

[EdStainless]

Have you checked the overlay? Is the chemistry at mid-thickness actually 82 or is there a lot of Fe dilution?
What about the weld dilution between the 82 and the 2205?
Did you use weld filler?
Since your operating temp is <300C any intermetallics had to form in the welding process.
It shouldn't be difficult to have fully austenitic welds between 82 and 2205.
Sounds like a weld process issue.

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