Discaloy 24 is an iron-nickel-chromium precipitation-hardening superalloy, historically registered as UNS K66220 and covered by ASTM A638 (the specification for precipitation-hardening iron-base superalloy bars and forgings, of which the closely related A-286 is Grade 660). Discaloy is generally regarded as the direct commercial precursor to A-286: both alloys share the same Fe-Ni-Cr backbone and rely on titanium additions to precipitate a strengthening gamma-prime phase during aging, but Discaloy's chemistry - developed by Westinghouse and Allegheny Ludlum in the 1940s - predates A-286's more refined, higher-titanium composition that became the aerospace-industry default.

Like A-286, Discaloy was developed for jet-engine turbine hardware: discs, blades, shafts, and high-temperature fasteners that needed to hold useful strength well above the working range of ordinary alloy steels, without the cost of a full nickel-base superalloy. It remains a useful reference point today for shops working on legacy aerospace and power-generation components built to these earlier-generation iron-base superalloy specifications.

The carbon content in the original source record for this page was inconsistent with published Discaloy/A-286-family data (which runs well under 0.1% C) and has been omitted rather than published as an unverified figure.

Discaloy 24 machines much like its better-known descendant A-286: an austenitic, gamma-prime-strengthened iron-base superalloy that behaves like a tougher, more heat-resistant cousin of an austenitic stainless steel rather than a full nickel-base alloy. In the solution-annealed condition it cuts reasonably well, but its titanium and molybdenum additions promote rapid work hardening under light or interrupted cuts, and its lower thermal conductivity compared with plain alloy steel concentrates heat at the cutting edge instead of carrying it away in the chip.

Because the alloy is precipitation-hardened after machining in most applications, the bulk of stock removal is normally done in the softer solution-treated state, before aging raises strength and cutting forces substantially. Sharp, positive-rake tool geometry and steady, adequate feed rates help avoid the built-up edge and edge notching that tend to appear when cutting speeds or feeds are too light for this alloy family. Rigid setups and ample coolant flow are standard practice, both to control heat and to flush the tough, stringy chips this alloy tends to produce.