Alloy 625 overlay on 316L 2

[A__J__T]

Anybody have any ideas why there would be a requirement to overlay an existing 316L component with Alloy 625 for corrosion reasons, and have you ever come across this as a weld overlay option?
Thanks
George

 

[metengr]

What is the application? Yes, I have seen 625 CRO on 304, 316 and 316L because of severe wastage from fireside corrosion.

 

[MJCronin]

I know of a few "waste to energy" boilers that have used 625 overlay to protect the superheater boiler tubes.

Accelerated wastage in this particular type of boiler is due to the chlorides present in the burning plastics.

http://selector.specialmetalswelding.com/publica/PSA10_020_Zhang.pdf

They are also recommended for tube protection in Biomass boilers.

Babcock Power recommends various alloys and types of overlay for various areas of the boiler

https://www.babcockpower.com/pdf/BTA-BR-0001.pdf

MJCronin
Sr. Process Engineer

 

[A__J__T]

This application is only for sea water corrosion under hyperbaric conditions, more concerned about the weldability of Alloy 625 on 316L from a chemical composition of weld metal perspective.
Thanks
George

 

[metengr]

No real issues with 625 weld metal directly on 316l substate provided the weld deposit is thick enough to avoid reduced corrosion protection because of dilution, use low heat input and the GTAW process.

 

[EdStainless]

We have cold drawn tubes that had 625 explosively welded over 316 (and also T-11).
They would probably be better off with a "C" type alloy, but 625 will be compatable.

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P.E. Metallurgy, Plymouth Tube

 

[A__J__T]

Thanks to all for quick reply