Inco 718 AMS 5663/PWA1010

[johngkn]

How does the grain size influence the stress rupture life in this material? Can too fine be bad (ASTM #11-12)?
Heat Treat was: 1775 F +/- 25F 1hr at temp, fan air cool. 1325F 8hrs furnace cool to 1150F hold at 1150F until total precip. time is 18hrs then air cool. Material was had a final forge @ 1850F

I am only getting 19-20hrs of Stress Rupture life. I have had 2 labs who test this material all the time test this with almost identical results.

Thanks

 

[EdStainless]

What were your elongation in SR testing?
What about the tensile properties? Did you clear the minimums by a fair margin?
And while I am at it what was the annealed tensile properties before aging?
Was it reannealed after forging?

Yes, fine grain size will reduce creep/SR life, but since this material regularly goes >300hrs at the minimum stress levels this seems like a huge change.

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Plymouth Tube

 

[TVP]

As Ed mentioned, too fine a grain size will reduce stress-rupture life. ASTM 11-12 is too fine, probably should be no finer than 7-8 for optimal properties. Standard solution treated and aged Alloy 718 will have a grain size of 4-6.

 

[johngkn]

Thanks Gentlemen, as this is what I thought but I always like to ensure my thoughts.
Ed, I don't get annealed properties from the mill, just the solution and precip, to ensure it meets the spec. mins.
The mill had ESR at 90hrs, the Tensile properties were well over the mins.
The mill actually reported grain size at ASTM # 10, so I am not too far finer but I am not seeing the ESR hours.
I can raise my final forging temp which will enlarge the grain some, so I will give that a shot.