Stellite Hardfacing Alloys
Stellite is a family of cobalt-chromium-tungsten-carbon alloys in which chromium and tungsten carbides sit in a tough, corrosion-resistant cobalt matrix. Hardness runs from about 30 HRC (Stellite 21, low carbon) through 40 HRC (Stellite 6) to 55 HRC (Stellite 1 and Stellite 20), and it is kept to 800 °C where tool steel has long softened. Tribaloy T-400 and Tribaloy T-800 replace the carbides with a hard Laves intermetallic phase for low-friction, galling-resistant surfaces.
Popular Stellite grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Stellite 6 | 541 | 834 | 8.44 | Not recommended | Good | General hardfacing; valve seats and pump parts |
| Stellite 21 | 495 | 710 | 8.33 | Poor | Good | Tough, shock-resistant trim and hot dies |
| Stellite 12 | 650 | 800 | 8.6 | Not recommended | Fair | Knife and cutter edges; more abrasion resistance |
| Stellite 1 | — | 620 | 8.69 | Not recommended | Poor | Severe abrasion where checking is tolerable |
| Stellite 6B | 620 | 1,000 | 8.38 | Not recommended | Poor | Solid wrought plate and bar wear parts |
| Tribaloy T-800 | 480 | 500 | 8.6 | Not recommended | Poor | Low-friction sliding wear, hot and corrosive |
| Stellite F | 480 | 650 | 8.68 | Not recommended | Fair | Exhaust-valve seat facing |
Choose Stellite for
Wear faces that also see corrosion, heat or both: valve seats and gates, pump shafts and sleeves, bushings, saw and shear blades, extrusion and hot-forging tooling, screw-conveyor flights, exhaust-valve seats — usually as a 1–3 mm weld, PTA or laser overlay on a steel body, sometimes as solid cast or wrought Stellite 6B.
Look elsewhere when
Pure abrasion at room temperature is the only problem (a chromium-carbide or tungsten-carbide overlay is harder and cheaper), the part is a die that can be through-hardened tool steel such as D2 or H13, the wear surface is inside the body (F75 and ASTM F1537 Alloy 1 carry the medical pedigree), or the geometry must be milled from solid — Stellite above 40 HRC is finished by grinding.
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Stellite by application
- Valve seats and trim
- Stellite 6 overlay for general service; Stellite 21 for steam and thermal-cycling trim; ERCoCr-A and ERCoCr-B are the AWS wire designations for Stellite 6 and Stellite 12 deposits.
- Knives, saws and shear blades
- Stellite 12 tips and edges for wood, paper and plastics cutting; Stellite 1 and Stellite 3 where the material being cut is abrasive; Stellite 6 where the blade also strikes.
- Sliding and galling wear
- Tribaloy T-400 and Tribaloy T-800 for bushings, seal rings and hot sliding contacts — the Laves phase gives a low friction coefficient and resists galling against steel and against itself.
- Solid wear parts
- Stellite 6B plate and bar for wear strips, guides and small components machined and ground from solid; cast Stellite 6 and Stellite 12 for shaped seats and nozzles.
Working with Stellite
- Overlay welding
- TIG, oxy-acetylene, PTA and laser cladding all deposit Stellite; preheat carbon steel to 200–400 °C and cool slowly to keep the overlay crack-free. Dilution from the steel lowers hardness, so a two-layer deposit or a nickel buffer layer is used where the full hardness is needed at the surface.
- Machining and grinding
- Stellite 21 and as-deposited Stellite 6 can be turned and milled with rigid setups, coated carbide and low speed; anything above 40 HRC, and all of Stellite 1, Stellite 12 and Stellite 20, is finished by grinding with silicon-carbide or CBN wheels. Allow 0.5–1 mm of grinding stock on an overlay.
- Heat treatment
- None. The hardness is set by the carbide fraction in the as-cast or as-deposited structure; stress-relieving at 600–700 °C after welding is the only thermal step. Stellite work-hardens further in service.
Other cobalt-chrome alloy series
Stellite Hardfacing Alloys — frequently asked
What is Stellite?
Stellite is a family of cobalt-chromium-tungsten-carbon alloys in which chromium and tungsten carbides sit in a tough, corrosion-resistant cobalt matrix. Hardness runs from about 30 HRC (Stellite 21, low carbon) through 40 HRC (Stellite 6) to 55 HRC (Stellite 1 and Stellite 20), and it is kept to 800 °C where tool steel has long softened. Tribaloy T-400 and Tribaloy T-800 replace the carbides with a hard Laves intermetallic phase for low-friction, galling-resistant surfaces.
Which grade of Stellite should I use?
Stellite 6 unless there is a reason not to: the general-purpose grade at about 40 HRC, tough enough to deposit crack-free, resistant to cavitation, erosion and corrosion at once — valve seats, pump sleeves, saw teeth. Stellite 12 (45–50 HRC) where abrasion matters more than impact, such as knife edges and cutter blades; Stellite 1 (50–55 HRC) for severe abrasion where some checking of the overlay is acceptable. Stellite 21 (28–35 HRC, work-hardening to over 40) for steam valve trim, hot-forging dies and anything that sees thermal or mechanical shock. Stellite 6B is the hot-rolled wrought version of Stellite 6 for solid plate and bar parts. Stellite F is the exhaust-valve facing alloy; Tribaloy T-800 for metal-to-metal sliding wear in corrosive or oxidizing service.
Which grade of Stellite is the strongest?
Stellite 12 has the highest yield strength in the series at 650 MPa; ERCoCr-A follows at 620 MPa. Values are for each grade's default condition.
Which grade of Stellite is easiest to machine?
G-CoCr28 (machinability poor, 15/100), then Stellite 21 (15/100).
Stellite 6 or Stellite 21?
Stellite 6 for abrasion, erosion and cavitation at about 40 HRC — the default overlay. Stellite 21 gives up hardness (28–35 HRC as deposited) for much better toughness and thermal-shock resistance and slightly better corrosion resistance thanks to its molybdenum, and it work-hardens to over 40 HRC in service. Steam valve trim, hot-forging dies and thick overlays that must not crack are Stellite 21; saw teeth and pump sleeves are Stellite 6.
Can Stellite be bought as a solid bar?
Yes, but less often than as welding consumable. Stellite 6B is hot-rolled Stellite 6 supplied as plate, sheet and bar for wear strips and machined parts; several grades are also investment-cast to shape. Most Stellite in service is a 1–3 mm deposit on a steel body because that puts the expensive alloy only where it wears, and the steel carries the load.