Merlin,

GTAW Technique for thin Inconel is not so different from stainless.

If the stuff is 0.030 or less you have some flexibility in choosing parameters unless your engineering documentation says otherwise. However, the tone of your post suggests your working without documentation.

Direct current straight polarity (DC-) (DCEN)

Assuming you have a decent TIG machine with a foot pedal your amperage need not be set above 25 or 30 amps

Electrodes may be 0.040 or .0063
Lanthanum 1.5 (Black)
Cerium (Orange)
Thorium 2% (Red)

An HW20 or equivalent TIG torch (air cooled ok for 0.030)

A gas lens is preferable but not required

Argon 15-20 cfh indoors

*Inconel* is a brand name and there are actually dozens of alloys and superalloys with that designator. Many of the Inco alloys have a tenacious oxide layer, which must be mechanically removed immediately prior to welding operations. These alloys are often more susceptible to contamination, becoming embrittiled if any contaminants (oil, grease, paint, carbon, water, etc) remain on or near the arc zone.

Argon purge on the backside of the weld and heat affected zone is essential in all cases

Pre weld annealing and Post weld stress relief are rare in thin Inco alloys but not unheard of, its up to you to find out if it's necessary in your application.

Fixturing and distortion control technique will vary from alloy to alloy, part to part and from tube to sheet. No answers here without more data


AWS Handbook Vol. 2 is an excellent resource for this kind of stuff.

Good luck

Lawrence

Merlin:
Lawrence is on track here. I work in an aerospace weld shop, and we weld inco assemblies from .020 or so up to .050.

DCEN
Amps set to 25 (typical)
10-20 CFM of Argon with back-gassing
Lanthanated and 2% thoriated tungsten, .040 dia
Gas lenses and ceramic cups (various sizes)

The key thing is to remove the "tenacious oxide layer" by vigorous sanding. After sanding, we usually use alcohol as a final "solvent clean."

Failure to remove the oxide layer will create various weld imperfections.

We weld a lot of Inco 718 (precipitation hardenable alloy via PWHT) - it is particularly suceptible to "strain age cracking." I suggest you refer to the AWS "Weldability" handbooks for more information.

Good luck.
Dave