Super Invar 32-5 is a controlled-expansion iron-nickel-cobalt alloy (UNS K93500) developed to go one step further than standard Invar 36: by trading a small amount of nickel for roughly 4-5% cobalt, Super Invar achieves an even lower coefficient of thermal expansion — typically about half that of standard Invar — over a narrower but very stable temperature band roughly from -50°C to 100°C (-58°F to 212°F). Like standard Invar, this near-cancellation of thermal expansion is a magnetic effect tied to the alloy's austenitic iron-nickel-cobalt lattice, and it is a solid-solution alloy rather than a precipitation-hardened one, so its dimensional stability is inherent to composition, not heat treatment.

That extra margin of expansion control makes Super Invar the material of choice for the most precision-critical optical and aerospace hardware: telescope structures and mirror mounts, laser and metrology reference benches, precision measuring instruments, and other assemblies where even the small residual expansion of standard Invar 36 is too much. It also retains good oxidation and corrosion resistance for long-term dimensional stability in demanding environments.

A prior SAE cross-reference on this page ("5592, 5716") belonged to the unrelated 330 heat-resisting austenitic alloy family and has been removed rather than carried forward as a designation for this material.

The prior version of this page omitted cobalt entirely, which is the defining alloying addition that distinguishes Super Invar from standard Invar 36 — it has been added back in based on verified UNS K93500 reference data.

Super Invar shares standard Invar's difficult machining personality and, if anything, is slightly tougher to work due to the added cobalt. Like Invar 36, it is not a stainless steel in behavior despite superficially similar iron-nickel chemistry — it machines closer to a nickel-cobalt alloy, with gummy, difficult-to-break chips, a strong tendency toward built-up edge, and rapid work hardening whenever the cutting edge rubs instead of shearing cleanly. Hardness alone understates the difficulty: the alloy's plastic, adhesive behavior ahead of the tool is what drives tool wear, not raw hardness numbers.

The same fundamentals that apply to standard Invar apply here, with less margin for error: machine in the annealed condition wherever possible, use sharp positive-rake carbide, and take a decisive depth of cut to get below any work-hardened layer left by the previous pass rather than a light, rubbing cut that just work-hardens the surface further. Because Super Invar parts are almost always precision optical or metrology components, dimensional stability during machining matters as much as tool life — rigid setups, conservative feeds, and adequate coolant to control heat all help avoid distortion as well as tool wear.

Values run conservative relative to standard Invar 36 due to the added cobalt. Assumes a rigid setup, sharp positive-rake carbide, and the material in the annealed condition.

Turning

Parting / Grooving

Milling