AerMet 100 is an ultra-high-strength secondary-hardening steel, registered as UNS K92580 and specified under AMS 6532 and AMS 6478. It is important not to confuse it with a stainless grade — despite the "steel" naming convention used across this reference chart, AerMet 100 carries only about 3% chromium, well below the roughly 10.5% threshold needed for stainless behavior. Its strength instead comes from a cobalt-nickel matrix (around 13-14% cobalt, 11-12% nickel) alloyed with chromium and molybdenum, hardened through a martensitic transformation followed by an aging treatment that precipitates fine alloy carbides (M2C-type) through the matrix — a mechanism called secondary hardening, distinct from both conventional carbon hardening and the intermetallic-precipitation aging used in stainless PH grades or nickel-titanium maraging steels.

The payoff is an exceptional combination of properties rarely found together: ultimate tensile strength around 285 ksi (1965 MPa), yield strength near 230-240 ksi, and fracture toughness roughly double that of conventional 300M or 4340 steel at comparable strength levels. That profile makes AerMet 100 the material of choice for landing gear, arresting hooks, actuators, and other high-stress aerospace structural components where both strength and damage tolerance are critical.

Note: this page's prior content listed the ~0.23% carbon figure under a "Copper" row. AerMet 100 does not contain a significant copper addition; the 0.23% figure is nominal carbon content, corrected here per AMS 6532 / UNS K92580.

AerMet 100 is normally supplied and machined in the solution-treated and refrigerated condition prior to aging, at roughly 28-32 HRC — soft enough to machine with conventional carbide, but tougher than a plain alloy steel at that same hardness because of its cobalt content and fine, dispersed carbide structure. Expect higher cutting forces and somewhat faster tool wear than 4340 at comparable hardness; treat it more like a tough, high-alloy die steel than a standard structural alloy.

As with maraging steels and PH stainless grades, the practical approach is to remove the bulk of the material in the pre-aged condition and hold final critical dimensions for after aging wherever distortion allowances permit. Once AerMet 100 is aged (typically around 900°F / 482°C for 5 hours) it reaches its full 55-56 HRC service hardness, and cutting forces and abrasive wear increase sharply — post-age machining should be limited to light finishing or grinding operations.

Values apply to the pre-aged, solution-treated condition (roughly 28-32 HRC). Reduce speeds substantially and favor tougher, wear-resistant grades for any machining performed after aging (~55-56 HRC).

Turning

Parting / Grooving

Milling