316L to Inco 625 & 316L to Inco 718 (P8 to P43)

By Gerry Byrnes Date 04-26-2014 18:13

I have a few questions about these combinations and I am hoping some of you may be able to help me. My past experience has been in the (GTAW) joining of aircraft engine hardware, I am transitioning into the facilities engineering world. My task is to qualify our pipe welders and certify a procedure to join 316 stainless steel (SCH40) pipe to Inconel 625 and to Inconel 718. The pipe will experience temperatures as high as 1150 deg F and a working pressure of approx. 400 psi. Based on our search for inco piping for test coupons, the inco is not widely used in the facilities world. Sorry for the lengthly prelude but I thought it was worth mentioning. My questions are: I am leaning toward using (inco 625), a wire that it readily available at our plant and used for aircraft engine hardware. The chemical composition seems to be a good match and I confirmed that with some of our material engineers but it is flagged with the AMS color code scheme. Do I just refer to that notation in the WPS & WPQ or do I refer the the F number that is in Sect IX which really doesn't define the chemical composition %'s? My second question is: Do the coupons and specimens have to be heat treated based on the temperature and pressure that the finished product will see?

By kcd616

Date 04-27-2014 07:04

I have made that weld a time or two :wink:

but have no idea about the testing part
but you are on the right track
hope this helps
sincerely,
Kent

By js55

Date 04-28-2014 14:06

Gerry,
If the filler metal cert does not state ERNiCrMo-3 you will have to list the chemical composition of the AMS material on the PQR and then utilize matching compositions for the WPS.
Also, if you don't have an SFA specification you don't have an F number either.
You are better off using the ERNICrMo-3 as such. Or for that matter a SS filler.
Heat treatment is a consideration of material properties 'as qualified', not service related per se.
As for the 718, this is an age hardening material and is sometimes stress relief heat treated. You need to consult engineering to determine if this is the case.