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Is 'invar' a class of materials, a specific material, or both? From the OP: > There is, however, a class of metal alloys called Invars (think invariable), that

Is 'invar' a class of materials, a specific material, or both? From the OP: > There is, however, a class of metal alloys called Invars (think invariable), that stubbornly refuse to change in size and density over a large range of temperatures.

serf 3y ago
its a small set of nickel iron alloys that are available (to machinists at least) in a few configurations dictated by their iron/nickel content. with the addition of cobalt it becomes Kovar, a metal that is common for telescope use or joints where metal bonds to glass. they're all fairly proprietary and expensive. I've used Invar a lot in the production of heated press platens.
- doubleg72 3y ago
  Inconel is a name here in the US
  - buildsjets 3y ago
    Yes, it is a name, but no, is not THE name. Invar and Inconel are completely different alloys with completely different use cases. I have specified them both. In aerospace, Inconel 625 and 718 are used in high temperature structural and transport element applications in aircraft. Invar is never used in aircraft structure, but it is used to make tooling that needs to be invariant in size, especially composite layup mandrels that are cured in autoclave ovens.
Prcmaker 3y ago
It's a small family of the nickel alloys. Lots of iron, as the primary alloying element, then other things. Different invar alloys exist, with different goals of 'invariant'. None are truly invariant, but some will behave better in a thermal band than others. Changing the alloying can get you into kovars (covariant, typically to glass or ceramic) another family. Inconel is yet another family of nickel alloy, favoured for its strength under some conditions. Small percentage alloying changes can have a sizeable impact.