Stellite 12 is a cobalt-chromium-tungsten hardfacing alloy that sits between Stellite 6 and Stellite 1 in carbon content and hardness - a deliberate middle ground in the classic Stellite lineup. Its higher carbide fraction than Stellite 6 gives it better resistance to low-angle erosion, abrasion, and severe sliding wear, while its lower carbon than Stellite 1 keeps a more usable balance of impact and cavitation resistance. It is frequently run self-mated or paired against Stellite 6 or Stellite 1 faces in service, and its tungsten content supports use at temperatures up to roughly 700°C.

Applications are wide-ranging within the wear-resistant category: industrial knives for cutting carpet, plastics, paper, and synthetic fibers; saw tips in the timber industry; control plates in beverage bottling equipment; pump vanes; bearing bushes; narrow-neck glass mold plungers; and hardfacing of engine exhaust valves, pinch rollers, and rotor blade edges. This is a fundamentally different design intent from the high-temperature structural cobalt alloys elsewhere in this library (S 816, Stellite 188), which are chosen for retained strength at temperature rather than surface wear resistance.

Stellite 12 is easier to machine than Stellite 1 or Stellite 100, but it is still meaningfully more abrasive to cutting tools than the high-temperature structural cobalt alloys in this library (S 816, Stellite 188), and considerably harder to cut than plain or low-alloy steel. Its 1.4-2.0% carbon content produces a moderate but still substantial volume of hard chromium/tungsten carbides in the cobalt-chromium matrix, and those carbides are the dominant source of tool wear - abrasive wear on the flank and edge rather than the crater wear and adhesion that dominate on the nickel- and cobalt-base structural superalloys.

Because Stellite 12 is most often deposited as a hardfacing overlay or supplied as a casting, primary machining is frequently limited to rough shaping before finish grinding, though bar stock and pre-hardfacing surfaces can be turned or milled under the right conditions. A rigid setup, moderate but steady chip loads, and a carbide grade with good abrasion resistance (rather than maximum toughness) will outperform a sharper, more fragile edge geometry.

Within the wear-resistant Stellite group, Stellite 12 falls in the middle of the abrasiveness spectrum - more forgiving than Stellite 1, 19, or 100, but still requiring more conservative parameters than the structural cobalt superalloys.