AerMet 340 is the highest-strength member of Carpenter Technology's AerMet family, sitting above AerMet 100 and AerMet 310 in both strength and alloy content. Its nominal chemistry — 0.33% carbon, 12.0% nickel, 15.6% cobalt, 2.25% chromium, and 1.85% molybdenum — pushes carbon and molybdenum higher than the other two grades, which increases the volume of fine alloy carbide precipitated during aging and drives the alloy to a nominal 352 ksi (2430 MPa) ultimate tensile strength and 314 ksi (2160 MPa) yield strength. As with the rest of the family, this is a secondary-hardening martensitic alloy steel, not a stainless grade — at roughly 2.25% chromium it is well below the level needed for meaningful corrosion resistance, despite occasionally being grouped alongside stainless PH steels in some reference literature.

That extra strength comes with a real toughness trade-off: AerMet 340's Charpy V-notch impact energy (around 10.8 ft-lb / 14.6 J) is noticeably lower than AerMet 310's, and its fracture toughness, while still respectable for a steel at this strength level, is reduced accordingly. AerMet 340 is reserved for the most weight- and strength-critical aerospace and defense structural applications — landing gear and other highly loaded components where the extra strength margin over AerMet 310 is worth the reduced toughness and the more demanding processing it requires.

AerMet 340 is a proprietary Carpenter Technology alloy rather than an AISI/SAE, DIN, or UNS standard grade. No independently verifiable Wnr., DIN, or UNS cross-reference was found for this designation — specify and order this material by the AerMet 340 trade name and Carpenter's mill certification.

Nominal type-analysis figures per published AerMet 340 data. These match this page's prior content, which was correct as published — no correction needed here.

AerMet 340 carries the same secondary-hardening machining logic as the rest of the family — machine the bulk of the part in the pre-aged, annealed condition and hold final dimensions for after aging wherever possible — but it is the most demanding grade in the family to cut. Its higher carbon and molybdenum content produce a denser alloy-carbide structure even in the annealed state, which increases abrasive tool wear compared to both AerMet 100 and AerMet 310, and its reduced toughness relative to AerMet 310 makes it less forgiving of interrupted cuts, chatter, or aggressive engagement.

Rigid, vibration-free setups, sharp positive-rake carbide, conservative feeds, and generous coolant are essential. Given the strength this alloy is chosen for, most applications call for final aging (secondary hardening via alloy carbide precipitation, not a copper- or titanium-based intermetallic reaction) after the bulk of machining is complete, with any post-age work limited to light finishing or grinding.

Values apply to the pre-aged, annealed condition. As the highest-alloy, highest-strength grade in the AerMet family, favor the lower end of these ranges on interrupted cuts or less rigid setups. Reduce further once the part is aged.

Turning

Parting / Grooving

Milling