321 SS to 9cr
321 SS to 9cr
I have a client asking me to research a 321ss to 9cr repair procedure. After doing my own research, I will also consult with a metalurgist as well as a selected weld engineer and compare notes.
A crack was found in a fairly heavy 1.5" thk. x 12"-16" long 321 stainless lug welded to a 9cr pad welded to a 9cr pipe. Existing filler material or weld procedure unkonwn. Cracks are small but can be seen with the naked eye. My guess is this lug is in an approximate 1200f environment or possibly higher continuously. I do not know how often it cycles.
The 321ss Lug to the 9cr pad weld is a full penetration weld. Not sure why they chose this combination (I would have attached a 9cr lug/s directly to the header with a hole in it for pinning the stainless support hanger)
Initial research has me leaning towards grinding out the existing weld cracks to penetrant test acceptable, Apply 400 f preheat with ER preheating (if possible) GTAW process using,ERNiCr 3 filler, slow cool to ambient prior to heat treatment followed by normal 9cr heat treatment (1350-1425f, couple hour soak, slow cool under insulation).... No wet type NDE until after heat treatment. The rub with this is perhaps the 321 cant handle the heat treatment.
I see some have recommended a butter weld (presumably a 1/4" thk layer of enco 82 butter weld to the 9cr pad and heat treat) in new construction. Would this then eliminate the need for heat treatment of the lug to the butter weld?
This is not possible without complete removal (which whether they realize it or not is going to happen sooner or later). Their intent for now is to buy some time for a permanent fix later.