duplex weld overlay on x65 pipe

[twoheads]

Is it possible to deposit duplex overlay to the bore of say x65 pipe without utilising a buttering run of dissimillar material before hand, and would i still have a interpass temperature issue as is the case with girth welds.

thanks

 

[metengr]

I would not recommend welding duplex stainless steel directly to CS because of the effects of base metal dilution that will significantly alter the performance characteristics of the duplex stainless steel weld overlay. From the reference material I have regarding welding of duplex stainless steels to carbon steel, this is considered a dissimilar metal weld and as such, you need to use 309LMoL as a butter layer.

 

[SJones]

It can be done solely with duplex ss consumables but austenitic alloys can also be used as the first layer and they tend to be cheaper than duplex. Assuming that corrosion testing will be part of the overlay welding procedure qualification, then, yes, you will still have an "interpass temperature issue".

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[MikeMet]

Weld overlay with duplex filler and no butter layer can be done successfully. The question has to be answered what do you need the overlay to do for you? If you are looking for a bit more erosion resistance due to higher strength, it can do that, but a hard facing type filler metal, such as Stellite or Colmonoy may be better. If you are looking for corrosion resistance you may need to use a super duplex filler metal to get a chemistry that is sufficent to give your required corrosion resistance. So decide what you really need from the overlay and then make an intellegent, informed decision.

 

[twoheads]

thanks Mick,
it will undoubtabley be for corrossion purposes, i will try to convince the customer that a 625 overlay would be more suitable.
I was more worried about metalurgical problems at the interface between the carbon steel and the duplex, dillution at the surface of the cladding i dont see as a problem as it will be done in two passes.
thanks to all who replied.

 

[strider6]

i think that the choice of 625 is correct. obataining the correct balance of ferrite/austenite of a duplex in a weld overlay is not easy. usually, i mean in my experience, the superduplex is used as a solid material and i've never seen a weld overlay with duplex.

S

Corrosion Prevention & Corrosion Control

 

[EdStainless]

In two passes with 309/2209 should work fine.
The weld filler grade of duplex will help assure that you get the correct phase balance. Moving to 625 will cost significantly more, and unless it is also done in multiple passes may not offer any better corrosion resistance.

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