overheated 316 question

Oct 08, 2005 3 Replies
P

I want to make some rocket parts from 316 stainless by diffusion brazing smaller parts into a larger assembly.



The assembly has to have both the cryogenic and high temperature strengths of 316, so using 316L is not an option.



The long heat-treatment cycle used for the diffusion brazing (includes 1 hr at 1065 C) will cause carbide? (I am not a metallurgist) growth problems.


Is there a way to treat the assembly after brazing to reverse that growth process - or do you have any other suggestions?


Accurate temperature cycling in controlled atmospheres is conveniently available. :)


Thanks,



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A
316 stainless is annealed at 1040-1120C. All carbides will dissolve uniformly into solution. Carbide precipitation can occur at temperatures between 425 and 900 °C. Depending upon the thickness, cool quickly through this temperature range. Use if water quenching does not cause distortion. Or air cool to around 950C and then water quench. You might want to try 321, 347, 348, and Carpenter 20Cb-3 stainless steels which are stabilized to prevent carbide precipitation.

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J

Carbide precipitation might not be an issue if the parts aren't subject to aqueous corrosion.

j
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A

In a cryo application, I'd be concerned with condensation.

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