Welding of F11 buttered with Inconel 625

[arcpro]

While welding of nozzle to nozzle joint (nozzle material F11 - bevels buttered with Inconel 625) with ERNICr-3, we are finding cracks.
What can be the probable causes for the same?

[inconel]

Hi,

What was the metal temperature/preheat,material thickness .....?

[arcpro]

Preheating was done at 200 deg C on F11. Material thickness at the weld joint was 21 mm.
I do not know why the cracks were coming up in the weld joint just after welding few mm of length.

[ashfaqanwer]

I would suggest you must also look into the effectiveness of purging also.
Normally, it is very difficult to weld with Inconel using GTAW without effective purging and you end up with cracks in the root pass with oxidation of the welding material.

[moe]

I think this has happened due to rapid cooling after the weld metal has been deposited & sufficient hydrogen has been absorbed by the weld metal from the arc atmosphere.

[ashfaqanwer]

Good point made by moe.

[inconel]

While welding of nozzle to nozzle joint (nozzle material F11 - bevels buttered with Inconel 625) with ERNICr-3, we are finding cracks.
What can be the probable causes for the same?

Hi,

Could you please give some more info. for further investigation?

1.What was the welding process ?
2.What was the position of the joint during welding ?
3.What was the progression.ie, uphill or down hill(Normally uphill preferred in pr. vessel industry...But mistakes has been reported due to manual error.)
clock wise or anticlockwise(Left to right or vice versa in case of O-Let type joints)?

[arcpro]

Hi Inconel,
1. Welding process - GTAW
2. Welding was being made while pipe in the vertical position (fixed - 2G position)

[inconel]

Hi, This is the reply I received from one of my friend on your query,

Matching chemistry to Inconel-625 is typically E/ER-NiCrMo-3 weld metal, while for Inconel 600/601/690 Inconel-82/182 electrodes ( E/ER-NiCrFe-3) are recommended. The details posted in your query below looks a bit mixed up.ie, buttered with ERNiCrMo-3 and Welded with ERNiCr-3.

Both the alloys are user friendly, provided surface cleanliness is well maintained throughout the process.

Typically cracking in Inconel or Nickel base alloy overlay and subsequently in the weld groove can happen due to:-

1. Iron Dilution from base metal-which could be minimised through controlling the welding parameters and lowering heat input, especially for the first pass. Manual GTAW being slower in speed that other welding processes and the deposition of weld metal being less in volume compared to SMAW or GMAW, would generally cause more Iron Dilution.

2. Carbon, Sulphur and Phosphorous dilution, generally the steel manufacturers keep these elements very much under control. But if by chance they’re high, a one buttering layer with matching electrodes (e.g. ER-80SB2Lor E-8108B2L) followed by 2 layers of Inconel buttering would be of help.

3. If you’re performing straight Inconel buttering by GTAW, depending on the deposition thickness asked for in the specification it would be advisable to perform the same in 2-3 layers at least. This would help to reduce the “Iron” and other elements very much to the AWS specification requirements (SFA 5.14 or 5.11).

If the problem is persistent then the advisable route would be:-

1. Perform PMI on the overlay, by Portable Spectroscopy Metorex Arcmet or equivalent to detect the above mentioned elements. XRF can detect “Fe” but can not detect these elements.
2. If these elements are well within specification, proceed to weld as suggested in the attached electrode spec, i.e Alloy 625/E-NiCrMo-3.Do not weld Alloy 625/E-NiCrMo-3 buttered WEP with E-NiCrFe-3 electrodes, it’s not advisable. In a Nickel base alloys introduction of more and more alloying elements would cause lowering the melting point and would lead to cracking due to shrinkage stress during welding.

[engr.abrar]

What is your composition of purge gas, Ar99.99% or Ar+2%N?
In one of our project we have the same problem and is resolved by changing the composition of purge gas from A99.99% to Ar+2%N. For Inconel welding it is preferred to use mixture of gases rather then pure Ar as purge gas.