Stellite 1 is a cobalt-chromium-tungsten hardfacing alloy from the classic "Stellite" family, and it sits at the extreme-wear end of that family. Where the high-temperature structural cobalt alloys in this library (S 816, Stellite 188) are chosen for retained strength at temperature, Stellite 1 is chosen for a completely different reason: it carries the highest carbon content of the common Stellite grades (2.0-3.0%), which produces a microstructure dominated by massive primary chromium/tungsten carbides in a cobalt-chromium matrix. That carbide volume fraction is what gives Stellite 1 its defining property - exceptional resistance to low-angle erosion and severe abrasive wear - at some cost to toughness and crack resistance compared to lower-carbon Stellite grades.

Typical applications lean toward sacrificial wear surfaces rather than structural parts: pump sleeves, rotary seal rings, wear pads, expeller screws, and bearing sleeves, generally applied as a cast or hardfaced deposit rather than machined from solid bar. Stellite 1 retains its hardness at temperatures in excess of 760°C (1400°F), and because of its high hardness and crack sensitivity, finished hardfaced deposits are normally brought to final dimension by grinding rather than by turning or milling.

Stellite 1 is one of the more demanding materials in this entire library to machine, and for a different reason than the nickel- and cobalt-base structural superalloys covered elsewhere. Its difficulty comes almost entirely from carbide volume fraction, not from work hardening or thermal softening resistance alone: at 2.0-3.0% carbon, the alloy's microstructure is packed with massive, hard primary carbides that behave more like an abrasive grinding medium than a conventional metal matrix under the cutting edge.

Because most Stellite 1 is supplied and used as a cast or hardfaced deposit rather than wrought bar, the manufacturer's own guidance is that finished deposits should be brought to size by grinding, not turning or milling. Where bar stock, castings, or pre-hardfacing surfaces do need to be machined, expect abrasive wear to dominate over adhesive or thermal wear mechanisms - tool life will generally be shorter than on the lower-carbon Stellite grades (6, 12, 21) at equivalent cutting parameters, and rigidity, low cutting speeds, and a very robust edge preparation matter more than a sharp, positive rake.

Compared to the high-temperature structural cobalt alloys in this library (S 816, Stellite 188), Stellite 1's high-carbide microstructure makes it meaningfully more abrasive to cutting tools despite its lower nominal operating temperature - this is a wear alloy engineered to resist abrasion, and that same property abrades the cutting tool.