Stellite Manufacturer — Cobalt-Chromium Alloy Wear & High-Temperature Parts

Stellite is a family of cobalt-chromium alloys engineered for extreme wear, galling, erosion and corrosion resistance, with the unusual ability to keep their hardness at high temperature. The cobalt matrix is strengthened by chromium and tungsten (or molybdenum) and by hard carbides, giving a material that outlasts hardened steels in sliding, cutting and high-temperature service. Stellite is a registered trademark; we manufacture cobalt-chromium alloys to these grade specifications.

Cobalt is the base (balance), with typically 20–33% chromium for corrosion and oxidation resistance, 3.5–19% tungsten or up to ~29% molybdenum for solid-solution strengthening, and 0.1–3% carbon which forms the hard chromium/tungsten carbides that give wear resistance. Small amounts of nickel, iron, silicon and manganese are also present. The carbon and tungsten/carbide content set the hardness — higher-carbon grades (Stellite 12, 20) are harder than lower-carbon grades (Stellite 21, 25).

Stellite 6 (UNS R30006) is the most widely used grade — the cobalt-alloy "workhorse". It contains about 1% carbon, 28% chromium and 4–5% tungsten, giving roughly 38–44 HRC hardness with an excellent all-round balance of wear, galling, corrosion, cavitation and heat resistance. It is the default for valve seats and trim, bushings, bearings, hardfacing and saw tips.

Stellite 12 (UNS R30012) has higher carbon (about 1.4%) and more tungsten (7–9.5%) than Stellite 6, giving a higher carbide volume and greater hardness (about 44–49 HRC). It sits between Stellite 6 and the very hard Stellite 1, and is chosen for more severe abrasion and low-stress wear where a little more hardness is needed without going fully to Stellite 1.

Both are cobalt-chromium-tungsten alloys, but Stellite 12 has more carbon and tungsten, so it has more hard carbides and is harder and more abrasion-resistant (~44–49 HRC) than Stellite 6 (~38–44 HRC). Stellite 6 is tougher and more forgiving with better impact and corrosion balance; Stellite 12 trades some toughness for extra abrasion resistance. Choose 6 for general wear and 12 for heavier abrasion.

Stellite 21 (UNS R30021) is a low-carbon (0.2–0.3%), molybdenum-bearing (5–6%) cobalt alloy with about 27% chromium. Its lower hardness (~27–40 HRC) is traded for excellent corrosion resistance, thermal-shock resistance, toughness and anti-galling behaviour, making it a favourite for valve trim, hot-work tooling and components that see corrosive media and thermal cycling.

Stellite 25, also called L605 or UNS R30605, is a cobalt-chromium-tungsten-nickel alloy (about 20% Cr, 15% W, 10% Ni) designed for high-temperature strength and oxidation resistance rather than maximum hardness. It is used for hot gas-path and high-temperature structural components in gas turbines and aerospace, and for high-temperature wear where ductility is also needed.

Stellite 6B is the wrought (rolled / forged) version of Stellite 6 — the same cobalt-chromium-tungsten chemistry produced as bar, plate and sheet rather than cast. The wrought processing gives improved toughness and ductility and a more uniform structure, so 6B is used where the part must be machined or formed from wrought stock, such as wear plates, bushes and bearing components.

We supply Stellite 1, 3, 4, 6, 6B, 6K, 12, 19, 20, 21, 25 (L605), 31, 694, Tribaloy T-400 and T-800, Cobalt F75 and TP80, with full chemical composition and equivalent UNS / AMS designations published in the grade table on this page. Other cobalt-alloy grades are made to your specification.

Common equivalents: Stellite 6 = UNS R30006 (AMS 5387/5373/5788); Stellite 12 = UNS R30012; Stellite 1 = UNS R30001; Stellite 21 = UNS R30021 (AMS 5385/5819); Stellite 25 = UNS R30605 (L605); Stellite 31 = UNS R30031 (AMS 5382, ASTM A732 Gr.31); Stellite 4 = UNS R30404; Cobalt F75 = UNS R30075; Tribaloy T-400 = UNS R30400. The full list is in the grade table above.

Two reasons: hard chromium and tungsten carbides are dispersed through the alloy and resist abrasion, while the cobalt matrix itself has a low stacking-fault energy that resists galling and adhesive wear and work-hardens under load. Crucially, cobalt alloys keep most of their hardness at red heat, so unlike hardened steels they do not soften and wear rapidly at high temperature.

Yes. The high chromium content gives good resistance to oxidation, many acids and chloride-bearing and corrosive media, and the cobalt base keeps useful strength and hardness up to roughly 800 °C and beyond (higher for the L605/Stellite 25 type). This combination of hot hardness and corrosion resistance is why Stellite is used for valve trim, turbine and high-temperature wear parts.

Valve trim (seats, seat rings, cages, balls, stems, plungers, pilots), sleeves, bushings, bearings, turbine rotors and stators, spinners and discs, extrusion dies and extruders, pelletizer knives, saw tips, scrapers, wearing strips, liners, erosion shields, nozzles, thermowell and protective tubes, and raw forms — welding rods, round bar, plate, sheet and tube. All can be made to your drawing and grade.

Investment (lost-wax), sand, centrifugal, vacuum and continuous casting; powder metallurgy; forging and rolling for wrought grades; hardfacing and cladding (weld overlay) onto steel substrates; surface coating; and precision CNC machining and grinding for final finishing. The route is chosen to suit the part shape, grade and quantity.

Yes. Stellite is widely applied as a weld-overlay hardfacing on carbon and stainless steel substrates — for example on valve seats, sealing faces and wear surfaces — so only the working surface is the expensive cobalt alloy. We supply Stellite welding rods and dense welding rods for this, and also produce solid cast and machined Stellite parts.

Stellite is hard and work-hardening, so it is difficult to machine by conventional turning; finished surfaces are usually produced by grinding, and complex features by CNC machining, EDM or as-cast to near-net shape. We CNC-machine and grind Stellite components to final dimensions and surface finish in-house.

Oil & gas, petrochemical, power generation, steel, glass (spinner discs), pulp & paper, plastic and metal extrusion, food processing and temperature measurement — anywhere components face severe wear, erosion, galling, corrosion or high temperature, such as control-valve trim, pump parts, turbine components, extrusion dies and saw tips.

Yes. Most of our Stellite work is made to order. Send your drawing, sample or specification with the required grade and we will manufacture the part — cast, wrought, hardfaced or machined — with material test certificates and PMI on request. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer and exporter from Mumbai, India.