Annealing 17-4PH

[sensij]

Would anyone care to speculate on what dew point level would need to be specified to avoid embrittlement of 17-4 in a hydrogen (bright) furnace @ 1950°F?

I have found some incredibly helpful information here in other threads as I have researched this project, hopefully I haven't missed a reference where the question is already answered.

Thanks,
-------Jason

 

[EdStainless]

You don't get hydrogen embrittlement in bright anneal because the annealed condition is not susceptible to it. As long as the pats are bright (say -50 DP or better) and the the parts exit into air at a temp of 250F or so you will be fine.

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Plymouth Tube

 

[sensij]

Ed,

Thanks for the response. I had found the text below in the Allegheny Ludlum data sheet for 17-4, and am concerned that the "bright" requirement might not be good enough. I've got some parts that became brittle with an H2 exit DP of -40. It sounds like my furnace might not be too far away from being able to do this, if I can get it tightened up a bit.

(

http://www.alleghenyludlum.com/ludlum/Documents/17-4Cdate082206.pdf):

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Material in the annealed condition should not generally be put into service. In this condition, the material has an untempered martensite structure and is less ductile than aged material. The untempered martensite may be subject to unpredictable brittle fractures. In corrosive environments, the untempered martensite is more sensitive to embrittling phenomena such as hydrogen embrittlement than material which has had one of the precipitation hardening heat treatments.

Jason

 

[EdStainless]

Did you cool to near room temp in Hydrogen? It would be better to allow parts to exit into air at 200-300F. If there is a bit of residual hydrogen this will allow a bake out.
The bigger issue is that if your surface isn't truly bright the oxide skin can trap hydrogen in the alloy and make it very difficult to remove.

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Plymouth Tube

 

[antmann2005]

just heat treat with in 4 hours and hydrogen enbrittlement is not an issue

 

[antmann2005]

i think its only an issue when pickling