Stellite 20 is a cast cobalt-chromium-tungsten alloy from the Stellite family of wear-resistant materials, distinguished by a very high carbon content (nominally 2.5%) that produces a dense network of hard chromium- and tungsten-rich carbides in the cobalt matrix. Chromium runs around 32.5% and tungsten around 17.5%, with nickel held below 2% and minor additions of molybdenum, iron, and silicon rounding out the balance. This is one of the most carbide-rich, abrasion-resistant grades in the numbered Stellite series - Kennametal, the current trademark holder, describes it as "one of the most abrasion-resistant standard cobalt-base alloys," with good corrosion resistance but comparatively low resistance to impact/mechanical shock.

Correction: the previous version of this page listed a hardness of 46 HRC. Kennametal's current published technical data for Stellite 20 gives a hardness range of 53-62 HRC, which is used below; the earlier figure could not be corroborated against manufacturer data and has been replaced.

Because of its extreme carbide loading, Stellite 20 is typically supplied as investment castings or applied as a hardfacing overlay onto wear-critical surfaces - valve components, extrusion tooling, cutting edges for abrasive materials, and other parts subject to severe abrasion or chemical attack - rather than machined from wrought bar. No AMS or ASTM designation is published for this grade in Kennametal's current data sheet, so no standard cross-reference number is listed here.

Stellite 20 sits at the difficult end of the cobalt-base alloy family. Its 2.5% carbon content and 17.5% tungsten produce one of the densest carbide networks of any standard Stellite grade, and that carbide volume fraction - not just bulk hardness - is what drives tool wear. The hard carbide particles act as an embedded abrasive, wearing down the cutting edge through mechanical abrasion in addition to the thermal and adhesive wear mechanisms common to cobalt alloys generally.

Like all cobalt-base alloys, Stellite 20 has low thermal conductivity, so heat generated in the cut concentrates at the tool-chip interface instead of dissipating into the workpiece, and it retains hardness at elevated temperature rather than softening the way many steels do at higher cutting speeds. Combined with 53-62 HRC bulk hardness, this means the cutting edge is under continuous, severe mechanical and thermal load throughout the cut.

In production practice, the highest-carbide Stellite grades (including 1, 3, and 20) are frequently finished by grinding rather than single-point cutting, precisely because of this combination of hardness and carbide density. Where turning or milling is required, very low cutting speeds, sharp positive-rake ground carbide edges, maximum rigidity, and continuous flood coolant are essential; expect shorter tool life than on the lower-carbon cast cobalt grades (such as Stellite 21, 30, or 31/X-40) covered elsewhere in this library.