Inconel 720 is a high-strength, precipitation-hardened nickel-chromium-cobalt superalloy developed for gas turbine disks and other rotating hardware that needs to hold up under both high mechanical stress and sustained heat. Compared with the 718 family, 720 trades some of that alloy's weldability and cold-forming ease for a much higher volume fraction of the gamma-prime strengthening phase, built around a notably high titanium and aluminum content. That microstructure gives it higher tensile and creep-rupture strength at elevated temperature than standard 718, which is exactly why it shows up in the hotter, more highly loaded sections of a turbine where 718's roughly 1300°F ceiling starts to fall short.

The alloy is normally supplied fully heat-treated — solution-treated and aged to develop its final gamma-prime structure — and shops essentially always machine it in that hardened, high-strength condition rather than as soft stock. Because so much of its strength comes from a dense population of fine strengthening precipitates rather than from cold work, 720 keeps a large fraction of its room-temperature hardness at the elevated temperatures generated during cutting, which is the central reason it machines noticeably harder than lower-titanium nickel alloys.

Typical applications include turbine disks, spacers, and other rotating components in aircraft engines and industrial gas turbines where higher strength and temperature capability than standard 718 is required.

Inconel 720 is one of the tougher nickel superalloys a shop will run, and the reason traces straight back to its chemistry. The unusually high titanium and aluminum content builds a dense network of gamma-prime precipitates that keep the material strong and hard well into the temperature range generated at the cutting edge. Combined with nickel's inherently low thermal conductivity, heat has nowhere to go except into the tool, so edge temperatures climb fast and flank wear accelerates if speeds aren't dialed back from what you'd run on a lower-strength nickel alloy.

Work hardening is aggressive on this material. A dull edge, light finishing pass, or any dwell time lets the surface harden before the next pass engages it, which drives notching and edge chipping on the following cut. Chip control also demands attention — 720 tends to produce tough, stringy chips that can smear across the rake face and re-weld to the tool under heat and pressure, a galling behavior common to high gamma-prime nickel alloys.

Rigid, vibration-free setups; sharp, positive geometries; and steady feed rates that avoid rubbing are essential. Expect noticeably lower cutting speeds and shorter tool life than on 718, with hot-hard, tough coated carbide grades performing best across turning, grooving, and milling operations.