NiCrMo-3 Weld Overlay

[teokal]

Dear all,
I have tried almost everything (in order to eliminate the "almost", I need your help), but I cannot succed while performing a procedure test on SAW Weld Overlay of NiCrMo-3 (Alloy 625) onto P No1 plate (SA 516 Gr70). The wire diameter is 2,4, and electricity is DC (+). We have a huge experience in weld overlay, and this is something that I just can't make it... Believe it or not, NiCrMo-3 is my favourite consumable... We tried slow speed; we tried high speed; we tried several extensions of wire; we tried several heights of flux. The wire-flux combination is from the same company, and it is recommended by them. All the parameters from the data sheet of the consumables have been kept... Whatever we do, the Fe % after 2 passes is 13%! (max by code is 5%). This makes Mo % to drop. My last effort will be to use DC (-). What about DC (+) for first pass, and then DC (-), in order to avoid too much dillution?
Any ideas will be appreciated.

Only best result in absolutely necessary time

 

[stanweld]

Is your power supply constant voltage? Have you increased voltage to decrease penetration and increase bead width? Have you checked the wire chemistry?

 

[teokal]

Dear Stanweld,
As I describe, the current is DC (constant). The electrical parameters used, are those sugested by the wire and flux manufacturer. Yes, I have checked the wire chemistry, and is OK (as per wire's data sheet, and as per ASME II).
Today we tried with DC (-), and contrary to my expectations, the FE% on the 1st pass, was 47% !!!!!! Also, we tried to lower even more the amperage, voltage, speed, and this gave us better than before but yet not "typically" acceptable. "Typically" goes for the fact that no one really expects 4-5% Fe content on 2 layers of NiCrMo-3.
According to the manufacturer's specialist, the wire diameter is pretty big. They suggest to use 1,6mm wire. But then, management of the company will kill me, due to low productivity...
About higher voltage value, as you suggest, I will let you know tomorrow, after we try it.
Anyway, thank you Stanweld for your time...

Only best result in absolutely necessary time

 

[unclesyd]

I haven't kept up to date but I have been told that most overlay work was being done with pulsed-arc machines.

 

[metengr]

For SAW, I would use a RPDC (-) for the first pass to reduce dilution with the carbon steel substrate and switch to DC for the second pass.

 

[stanweld]

As I understand you, the power supply is constant current. Lower penetration can be had using constant voltage. I assume that your power supply is not interchangeable. If it is, I recommend changing to constant voltage mode or AC mode if you can.

 

[jrupert24]

We run same wire diameter, DCEP, 20 ipm first layer, then run very heavy weld on second layer, Inconel wire should be less than 1% Fe. After many many test plates, I have only passed a few qualifications with very tight controls. This is telling me that maybe its not meant to be. Not saying that is can't be done, but to be that close to the border line may indicate you will have issues in production. I do know its possible consistently with 1/16" dia, but then you do lose some productivity. However, the difference in cost of the Inconel in pounds using 1/16" (should be less than with 3/32") vs production time may make it worth it.