Cobalt Alloy (Stellite)
Cobalt Alloy (Stellite) – Wear and Heat Resistant Hard-Facing Alloy for Valve Seats and Cutting Edges
Stellite cobalt alloys (Co-Cr-W) are the benchmark hard-facing materials for applications requiring simultaneous resistance to wear, corrosion, and elevated temperatures. Unlike tool steels and nickel alloys, cobalt alloys retain hardness and wear resistance above 600°C, making them irreplaceable for valve seat overlays, saw blade tips, and biomedical implants subject to combined mechanical and corrosive attack.
Key Properties
- Tensile Strength: 897 MPa
- Hardness: 380 HB
- High-Temperature Wear Resistance: Excellent — retains hardness above 600°C
- Density: 8.30 g/cm³
- Corrosion Resistance: Fair to good in most environments
- Standards: AMS 5387 / ASTM F75
Common Applications
Power plant valve seat overlays, oil and gas choke valves, saw teeth and timber cutting tools, surgical implants (ASTM F75 cast cobalt alloy), gas turbine hot-section components, and food processing cutting equipment.
Material properties
| Material name | Cobalt Alloy (Stellite) |
|---|---|
| Type | Other Metals |
| Standard code | AMS 5387 / ASTM F75 |
| Tensile strength (MPa) | 897 |
| Yield strength (MPa) | 517 |
| Fatigue strength (MPa) | 345 |
| Elongation (%) | 5 |
| Hardness (Brinell) | 380 |
| Density (g/cm³) | 8.3 |
| Electrical resistivity (µΩ·in) | 90 |
| Thermal conductivity (W/m·K) | 14 |
| Melting range (°C) | 1285–1395 |
| Weldability | Fair |
| Formability | Poor |
| Shear modulus | 100 |
| Industry code | cobalt_alloy |