[MuskokaCanada]

The coles notes version is:

316 parent metal
8" diameter solid x 6" long
2 separate sections to weld
minimum 0.06" buildup required after finish machining
Pre-machined 1/4 radius to ensure full penetration into corner
filler metal is stellite 6
procedure will not allow for a pass of Inconel under the stellite

I have had success with this job in smaller diameters like 3" but I seem to struggle with a crack of two on the larger diameter parts.

Do I have too much dilution of the parent metal when I'm welding the larger diameter?

Am I not allowing enough time between passes and interpass temperature is too high?

Thoughts?

[Arclight Ironworks]

You are most likely on the proper investigative path.

What defect (hot/centerline cracking, cold/underbead/traverse cracking, etc) are you experiencing? What can you tell us about the geometry of the machined joint? Single bevel? J groove? U groove? Are you working from a WPS?

PreHeat, IP Temps, and PWHT is definetly critical for fusing Stellite to Austenetic SS. Reference: Metallurgy - OFW of Stellite 6 to 304/316SS.

If your joint interface is not optimized, Then the admixture (filler metal + base metal) at the weld line becomes super critical. Minimizing the admixture is possible by changing the joint detail and/or minimizing penetration.

[Poland308]

Are you using temp sticks to determine interpass temps? If your using a laser thermo gun on a reflective surface it will give you faulty readings.

[MuskokaCanada]

This is not a "joining" procedure, it's just an overlay so there is no "joint" per se. The pre-machined diameter ends with a 1/4" radius so you don't need a lot of penetration to start the overlay.

I am using a weld positioner so the speed is constant and the beads look good.

The defect is occurring perpendicular to the weld direction and only on my larger diameter pieces, as I noted before. I just successfully completed two other stellite overlay pieces with a 4 1/2" OD with 0.045" per side required finished overlay after machining. *I say "successfully" but I haven't post machined them yet, they're sitting in vermiculite until morning to control cooling rate.

I do use a laser gun to determine interpass temps as my procedure wouldn't allow for temp sticks in our facility for ANY procedure. LOL. Crazy .. I'm aware. So my interpass on the smaller diameter pieces is between 300 and 350*F and on the larger 8" diameter failed piece it was always under 150*F.

I'll post about finished machining results on the 4.5" pieces tomorrow.

[Poland308]

Too cool can be just as bad as too hot. I recently did some repairs to a stress cracked boiler tube sheet. The pre heat was 250F And the interpass was 200F - 300F. With a post heat for about 30 minuets. Without this it would crack perpendicular to the weld about an hour after it cooled.

[MuskokaCanada]

The two 4 1/2" pieces turned out perfectly.

I'm so pissed about the 8" diameter one.