We have been experiencing susceptibility to heat affected zone cracking in 800HT (UNS N08811) forgings. This has not been a problem with all heats but rather appears to be a random type problem. The problem to date has been limited to solely to forged material. All forgings are supplied to ASME SB-366 with required solution anneal (2100F~2180F} followed by rapid air or water quench. A limited metallurgical examination suggested that the cause was liquation cracking. Welding was performed by GTAW with ERNiCr-3, no preheat, maximum interpass 300F.
-- When issue arises, we have used a buttering type technique; welding a layer of ERNiCr-3 on the faying surface with lowest achievable heat input and no preheat and minimal interpass prior to making the actual weld. This alleviates the problem about 33% of the time.
Questions are as follows:
1) have others observed cracking problems when welding forgings made from 800HT type material?
2) what material controls (chemistry limitations, heat treat requirements, etc) were put in place to mitigate cracking susceptibility? have they been successful?
3) other special welding controls?
I have found only a couple of papers dealing with this issue. Most recent was an article in the AWS Journal by Dupont, however this study was on autogenous welding on tubing. Other than that there was some earlier work done at Oak Ridge which showed some heats of alloy 800 susceptible to cracking but with no real conclusions on how to mitigate.
Any comments or discussion would be appreciated. Any additional papers/references dealing with this topic would also be appreciated.
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