Quench vs. Hydrogen Assisted Crack
Quench vs. Hydrogen Assisted Crack
(OP)
I am seeing some strange cracking patterns in castings when performing MPI after the quench and temper operation. In some cases they appear similar to HAC. Can anyone suggest a way to differentiate between the two?





RE: Quench vs. Hydrogen Assisted Crack
Best regards - Al
RE: Quench vs. Hydrogen Assisted Crack
RE: Quench vs. Hydrogen Assisted Crack
RE: Quench vs. Hydrogen Assisted Crack
Regards, Wil Taylor
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RE: Quench vs. Hydrogen Assisted Crack
So you can have HAC or delayed cracking in weld repaired areas. The trick is to know the weld repaired locations and evaluate the crack morphology. In areas where no weld repairs have been confirmed the likelihood of HAC is remote.
RE: Quench vs. Hydrogen Assisted Crack
Good comment.
However, I would guess that the foundry would carry out weld repair before quench and temper operation. Also, in the event of major weld repairs the castings are normalized before quench and temper operation.
This good foundry practice would minimize the risk of cracks.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Quench vs. Hydrogen Assisted Crack
If the crack existed before HT, the inside of the crack would have been exposed to the heat treat atmosphere. Maybe if there was decarburization that could not be completely recovered during HT, you would see the effect of the crack surface being exposed to the atmosphere because the decarb just inside the opening of the crack would be more fully eliminated than at a similar depth away from the crack.
RE: Quench vs. Hydrogen Assisted Crack
RE: Quench vs. Hydrogen Assisted Crack
RE: Quench vs. Hydrogen Assisted Crack
It is really important to know the grade, it might be delayed cracking on weld repairs, it's not common on base material unless it's an HSLA (HY80 etc). If its a recurring problem, you could put a degas op in after your first normalise. The most effective is 300C for 24 hours per inch section thickness, but that might not be practical.
RE: Quench vs. Hydrogen Assisted Crack
The reason I brought this question up is the similarity of a "Fish eye" to a quench crack. This part is having a high percentage of cracks after Q&T, and has had some failures in the field. Origin appearance is very similar, just in some cases it's internal, and others is closer to a surface. I'm just trying to confirm I am not fighting the wrong issue.
RE: Quench vs. Hydrogen Assisted Crack
RE: Quench vs. Hydrogen Assisted Crack
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Quench vs. Hydrogen Assisted Crack