Stellite 6
A cobalt wear alloy for hardfacing
Typical values for the temper in the title
Stellite 6 is a cobalt-based alloy with about 28% chromium, 4–5% tungsten and about 1.2% carbon. Carbon and chromium form hard carbides, so it is highly resistant to wear, metal-to-metal galling and cavitation erosion, and keeps its hardness up to about 500 °C.
It is usually not a structural material, but one welded as an overlay (hardfacing) onto a steel or stainless part. It is the most common choice for valve seats and sealing faces, and is often used self-mated. It is also sold as castings and powder.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 890 MPa | database value |
| Yield strength Rp0.2 | 550 MPa | database value |
| Elongation A | 1% | |
| Modulus of elasticity E | 210 GPa | |
| Density ρ | 8.44 g/cm³ | |
| Hardness | about 36–45 HRC | per Stellite data |
| Machinability | 15% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Co cobalt | balance | |
| Cr chromium | 27–32 | carbides and corrosion resistance |
| W tungsten | 3–6 | strengthening and hardness |
| C carbon | 0.9–1.4 | forms carbides: wear resistance |
| Ni / Fe / Si / Mn / Mo | small amounts |
Ranges per Stellite (Kennametal) data.
Conditions and heat treatment
Stellite alloys are not hardened by ordinary heat treatment: hardness comes from carbides that form on solidification. So properties depend on the production route (casting, weld overlay or powder).
| Condition | Properties | When to choose it |
|---|---|---|
| Weld overlay (hardfacing) | about 36–45 HRC, depending on process and dilution | valve seats and wear faces |
| Casting | similar hardness | whole parts |
| Powder (PM) | finer structure | small parts |
Applications
- Valve seats and sealing faces
- Pump shafts and bearings
- Erosion and cavitation shields
- Hot cutting blades
- Hot wear surfaces
Fabrication
Welding
Welded as an overlay by TIG, stick electrode, laser or PTA, with ERCoCr-A filler. Preheating the base part is common to prevent cracks in the overlay. Dilution with the base reduces hardness.
Machining
Nickel alloys work harden, stay strong when hot, and wear tools. Use low speed, a steady feed that does not "rub", sharp rigid tools and plenty of coolant.
Machining
Very hard to machine: turn with carbide tools, and usually finish by grinding.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Stellite 21 | 655 / 450 MPa | Brazing / weld overlay | less carbon: tougher and more corrosion resistant, softer · material page |
| D2 | 800 MPa anneal / — | Not recommended | a hard tool steel, does not keep hardness when hot · material page |
| Inconel 625 | 827–1034 / 414–758 MPa | Excellent — ERNiCrMo-3 | a nickel alloy for corrosion-resistant overlay · material page |
Common mistakes
Welding a thick overlay without preheat
The overlay may crack.
Welding one thin layer and expecting full hardness
Dilution with the base lowers hardness. Two layers are sometimes needed.
Machining it like steel
The material is very hard. Plan stock for grinding.
Equivalents, standards and supply
| UNS | R30006 |
|---|---|
| Standards | AMS 5387 / AMS 5788 / AWS A5.21 ERCoCr-A |
| Forms | rod · powder · electrode |
| Producers | Kennametal Stellite · Deloro |
Learn more
Values are typical and for comparison only. For design, rely on the standard and the mill certificate. Sources: Stellite (Kennametal) and Elgiloy Specialty Metals data sheets, ASTM F1058, and the METAL HUB materials database. Stellite and Elgiloy are trademarks of their owners.
Updated: October 31, 2026