"Hydrogen Embrittlement"

Question:

"I have read a little about this subject, and cant seem to get a definite answer. For an automotive application one of our group is looking at brazing 17-4PH steel in 60% Hydrogen at approx 1120C for 5-10mins, is this likely to give problems with HE? I had a feeling that the solution treat after braze may do the trick, but Im a bit concerned about the comment you made about ageing, we plan to follow the standard H900 age which is done at 482C, can you explain a bit more how this may be a cause for concern?"

Answer:

Any hydrogen absorbed into the 17-4PH should be outgassed when cooling to ambient temperatures unless immediately quenched from brazing temperatures. If quenched but subsequently aged, it should outgas then. Depending on the aging temperature, 17-4PH may be susceptible to HE in service if placed in a corrosive environment. Aging temperatures below 1100F (593C) could be a problem. Aging 17-4 PH at 900F will result in a Rockwell C hardness of HRC 40+. At these hardness levels, depending on the intended service, it may be susceptible to HE if place in a corrosive aqueous environment. I have observed HE of 17-4 PH in downhole directional drilling service at these hardness levels. It will also be susceptible in seawater service, especially if cathodically protected.

 

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