monel 400 weld overlay cracks

[teokal]

Hi,
on SA105 material (thk 100mm) we are trying to perform weld overlay with Monel 400 [wire NiCu-7 1,6mm , flux SA FB 2 55 AC (DIN EN 760) manuf. OERLIKON]. The process is SAW.
the welding electrical parameters are: 300A, 32-34V.
The problem is that we have cracks (like spider net) on the welded surface, which continue inside the base metal... Does anyone have the experience to help me with this problem? I tried also with different preheat temperatures...
Thank you in advance...

 

[stanweld]

Excessive iron dilution will lead to hot cracking. For best results make the first layer with Nickel filler and the next layer with NiCu-7.

 

[EdStainless]

You don't say how much overlay you are trying to build. Typically a thin pass of 60 or 61 (I can't recall which) is used.
You also have to careful to keep things very clean. A tiny amount of S will also cause extensive cracking.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[metengr]

Based on past experience, I concur w/ stanweld

 

[strider6]

Why iron dilution will lead to hot cracking?
Hot cracking is not related to impurities like S?
S.

http://www.corrosionist.com

 

[EdStainless]

Look up the Special Metals welding guide. If says that excessive Fe dilution will lead to cracking. I haven't worked on Monel metallurgy for years, but it must have something to do with either solidification segregation or a phase composition that is hot-short.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[stanweld]

strider6,
There are a number of compositions in nickel base and iron-nickel-chrome alloys that are subject to hot cracking. Follow Ed's advice.