Effect of Precipitation Hardening on Elastic Modulus

[minger]

Hey guys, we have ordered some spring rings made out of Inconel 718. For some reason the company didn't finish the heat treat and the parts are just annealed, in the "dead-soft" condition.

I need to evaluate if these things are usable (they are actually supposed to be soft and were designed to be as soft as possible). Unfortunately I'm not a materials guy and cannot find any info on an "as-annealed" state of this stuff. Given a properly heat-treated piece, is there anything I can deduce about the elastic modulus from simply the hardess, or at least make a guess?

FYI, The spec calls for >36.0 HRC, and we have HRB 92, which ~14 HRC

Any help? Thanks,

 

[Mapes]

Forgive me if this comment is too basic, but elastic modulus is relatively insensitive to changes in microstructure such as precipitate size or density. (Hardness is a measure of resistance to permanent deformation, while elastic modulus is a measure of resistance to elastic deformation.) For example, steels are generally far harder than iron, their main constituent, but have approximately equal stiffness. Is there a reason you think that your specific samples would vary far from the general Inconel elastic modulus of ~200 GPa?

 

[Q_Goest]

Hi minger. I agree with Mapes. I've seen a lot of data and never seen anything that indicates a change in modulus due to change in hardness.

If the springs are annealed, I'd be much more concerned with the material yielding when put into use.

 

[minger]

OK, so the hardening pretty much only increases hardness and strength? Then, I only need to analyze whether or not these things will fail?

gotcha, thanks a bunch.