Effect of Precipitation Hardening on Elastic Modulus

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Discussion Overview

The discussion revolves around the effect of precipitation hardening on the elastic modulus of Inconel 718, particularly in the context of evaluating the usability of spring rings that are in an annealed state rather than heat-treated. Participants explore the relationship between hardness and elastic modulus, as well as concerns regarding material yielding.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the elastic modulus can be inferred from hardness measurements in the context of Inconel 718, noting that elastic modulus is generally insensitive to changes in microstructure.
  • Another participant supports this view, stating that they have not encountered data indicating a change in modulus due to variations in hardness.
  • A participant expresses concern about the potential for material yielding when the annealed springs are put into use, rather than focusing solely on elastic modulus.

Areas of Agreement / Disagreement

Participants generally agree that elastic modulus is not significantly affected by hardness in this context, but there is no consensus on the implications for the usability of the annealed springs, particularly regarding yielding.

Contextual Notes

Participants acknowledge the need to consider the specific conditions under which the springs will be used, as well as the limitations of applying general data on elastic modulus to specific samples.

Who May Find This Useful

This discussion may be useful for materials engineers, mechanical engineers, and professionals involved in the design and evaluation of components made from Inconel 718 or similar materials.

minger
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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,
 
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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?
 
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.
 
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.
 

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