Same alloy, different trade name: Udimet 718 is Special Metals Corporation's trade designation for UNS N07718 - the identical nickel-chromium-iron superalloy marketed by other producers as Inconel 718. There is no chemical or metallurgical difference between Udimet 718 and standard Inconel 718; both names refer to the same AMS 5662/5663 specification. For that reason, the composition, designation equivalents, and machining data on this page are drawn directly from FM Carbide's Inconel 718 reference page to keep the two pages consistent.

Precipitation-hardened primarily through niobium and titanium additions that form strengthening gamma-double-prime and gamma-prime phases, this alloy delivers an unusually strong combination of high yield and tensile strength, good fatigue and creep-rupture resistance, and useful strength from cryogenic temperatures up to roughly 704°C/1300°F. It dominates rotating and static gas-turbine hardware - discs, shafts, casings, blades, and fasteners - in jet engines, industrial gas turbines, and turbochargers, as well as high-strength aerospace fastener and structural applications outside the hot section.

Because Udimet 718 is chemically identical to Inconel 718, its machining behavior is identical as well. It carries the classic difficulties of the nickel-superalloy family, and because this chemistry is the grade most shops encounter most often (regardless of which producer's trade name is stamped on the mill certificate), its behavior is the benchmark against which other HRSA materials are usually judged. Low thermal conductivity is the first obstacle: heat generated in the cut does not flow into the chip and workpiece the way it would in steel, so it concentrates at the tool-chip interface and accelerates crater wear, edge deformation, and thermal cracking.

Rapid work hardening is the second major factor. The same gamma-double-prime and gamma-prime precipitates that give this alloy its strength also make the surface harden aggressively under cutting stress - any rubbing, hesitation, or dull edge burnishes a hardened skin into the surface that is tougher to remove than the parent material. Consistent, adequate feed per tooth/revolution is essential so the edge is always cutting beneath the previous pass's affected layer rather than skating across it.

Unlike steel, this alloy does not soften appreciably at elevated cutting temperatures, so the edge stays under heavy mechanical load even as heat builds up, which drives notch wear and chipping if speeds are pushed too high. Rigid, vibration-free setups, sharp positive-rake carbide with a wear-resistant coating, moderate-to-low cutting speeds, and generous coolant delivery are the standard countermeasures.