PWHT Inconel 625 (.625") to C/S (.625) with S/S clad
PWHT Inconel 625 (.625") to C/S (.625) with S/S clad
(OP)
Story line:
Vessel built 1994
Vessel diameter 7'0 ID
Top head, shell and bottom c/s 516 gr 70 (1.750"thk) with
s/s clad 304 (.125")=total=(1.875")
Steam jacket total vessel encompassed.
1st failure 2000
bottom head corroded,,,decision made to replace bottom
head with solid Inconel 625 and go to half pipe coils
just on the bottom head. Filler metal ERNICRMO-10
Process GTAW
2nd failure 2003
New Inconel head cir. weld developed through wall
cracking 45" at the toe of the Inconel weld to solid
Inconel head.
3rd failure 2010
Cir welds on bottom head two 30" through wall cracks.
Question: Previous WPS repair never called for PWHT.
Because we have three dissimilar metals with
a range of about 17% coefficient expansion
difference,,,wouldn't a PWHT in the soaking
range for Inconel help?
Vessel built 1994
Vessel diameter 7'0 ID
Top head, shell and bottom c/s 516 gr 70 (1.750"thk) with
s/s clad 304 (.125")=total=(1.875")
Steam jacket total vessel encompassed.
1st failure 2000
bottom head corroded,,,decision made to replace bottom
head with solid Inconel 625 and go to half pipe coils
just on the bottom head. Filler metal ERNICRMO-10
Process GTAW
2nd failure 2003
New Inconel head cir. weld developed through wall
cracking 45" at the toe of the Inconel weld to solid
Inconel head.
3rd failure 2010
Cir welds on bottom head two 30" through wall cracks.
Question: Previous WPS repair never called for PWHT.
Because we have three dissimilar metals with
a range of about 17% coefficient expansion
difference,,,wouldn't a PWHT in the soaking
range for Inconel help?





RE: PWHT Inconel 625 (.625") to C/S (.625) with S/S clad
I recommend you butter weld the carbon steel side with ERNiCr3 and then weld that to the I625 solid head with Inconel 112 for Incone A filler, as recommended by Special Metals. Much better from a fatigue and metallurgical aspect. If you want to PWHT to the carbon steel side before making the weld to the I625 head, it can be done.
I also recommend you do an FEA analysis of the weld joint to determine the effects of the heating coils and jacket on the shell with respect to stresses on the weld joint. May show you some issues that are contributing to the failure. I also recommend you get a boat sample of the crack for metallurgical analysis, again more data to show what's happening.
RE: PWHT Inconel 625 (.625") to C/S (.625) with S/S clad
RE: PWHT Inconel 625 (.625") to C/S (.625) with S/S clad
Thanks for you input and question.
The reactor is a batch epoxy reactor that swings from 100F to 400F 4-times a day.
RE: PWHT Inconel 625 (.625") to C/S (.625) with S/S clad