Welding Inconel X750 4

[Metrics]

Does anyone have thoughts on TIG welding Inconel X750 to 316L stainless steel?

I want to weld a 3/4" "rod" of inconel to a "thick wall tube" of 316 (3/4" id). The parts would be slid together so the ends are even and the welded at the interface of the two parts. No filler metal.

Inconel would be in the precipitation hardened condition, 316 in annealed condition. Service temperature is -45 to +200F.

Is this a no problem weld or does it require special setup?

Thanks for any advice you can provide.

 

[metengr]

Please review the information below especially page 24;

http://www.specialmetals.com/documents/Inconel alloy X-750.pdf

 

[Metrics]

Thanks.

I have seen this sheet. It seems to imply that you can weld "normally" in the hardened condition if you don't expose it to higher temperatures afterwards.

Would it be right to assume that the advice applies only welding to X750 and similar alloys or would it apply in general to other readily weldable metals like 316?

Maybe I'm just being a little cautious given the expense of X750.

 

[metengr]

The advice applies to only the Inconel X-750 base metal heat affected zone. The 316 stainless steel would be unaffected because it does not harden by heat treatment.

I would strongly suggest you develop a welding procedure specification by using a mock-up. Have the coupon tested to evaluate the tensile and bend properties of the autogenous weld.

 

[Duwe6]

what metengr said. Bimetallic autogenous [no filler added] welds behave badly. Being a betting man, I will give 4:1 odds that filler will be required to pass the required tests to prove a PQR/WPS.

 

[TVP]

My initial thoughts are similar to Duwe6: the welds will likely have poor mechanical properties without filler, and may not have good geometry either. Why weld with no filler?

 

[Metrics]

Thanks for info. We weld Inconel 625 to 316L with no problem. It looks X750 maybe significantly different. Good to know!

No filler rod is just the standard process here. The weld has very significant impact on product performance. This process or EBwelding seems to work best throught our industry.

 

[dhengr]

Isn’t that kind of closed circular weld a very constrained weld with high potential of cracking in almost any case? Then add to that two dissimilar materials and cross section properties, and I’ll bet with Duwe6 on the need for filler. Obviously, this filler material should be compatible with the two base materials and provide the required strength, but otherwise the joint should be designed and prepared to allow for the use of a lower strength, softer, more yielding material, to prevent cooling or joint geometry type cracking.