Creep Embrittlement of 1.25 Cr - 0.5Mo

[Montana1]

I am curious about repairing 1.25 Cr - 0.5 Mo vessel plate that has been in service in a catalytic reformer at 900F for 25 years. The nozzle repads show cracking in the HAZ when exposed to wet MT. I have read various articles regarding repair techniques. Some recommend a PWHT cycle of 1300F for 8 hrs prior to weld repair while others recommend a "full re-heat treatment" or normalizing at 1650F for some calculated time. Again, the normalizing is done prior to weld repair to bring back room temperature ductility. Has anyone had experience doing this?

 

[metengr]

Montana1:
I am not in agreement that thermal embrittlement is necessarily the issue here for the observed HAZ cracks. The molybdenum is helpful in retarding the effects of thermal embrittlement. I suspect you may have hydrogen damage as a result of service conditions, and if this is the case, you could perform a pre-bake of the repair areas to allow for the residual hydrogen to be removed followed by weld repair.

 

[stanweld]

We have made numerous similar repairs to Grade 11 in Power Plants and Petrochemical Plants with no preliminary heat treatments.

 

[eyec]

try taking a replication from the area and analyze it to see if it is embrittlement or hydrogen damage then go for the type of repair suggested for the damage mechanism.

Steven C
Senior Member
ThirdPartyInspections.com