Materials/Metals and alloys/Collections
Cobalt and cobalt-base alloys
cobalt-alloysAbout cobalt and cobalt-base alloys
Cobalt and cobalt-base alloys (cobalt, L-605, CoCrMo, Havar, Phynox): strength, wear and corrosion data with sources.
Cobalt-base alloys keep their strength at high temperature, resist wear and corrosion and are biocompatible. They are used in turbine parts, medical implants, springs and thin foils.
At a glance
- Highest yield strength: Havar (UNS R30004) reaches 2,068 MPa. Lowest: UNS R30605 starts at 379 MPa. (3 of 4 grades have a sourced value.)
- Highest tensile strength: Phynox (UNS R30003) reaches 2,620 MPa. Lowest: UNS R30605 starts at 655 MPa. (4 of 4 grades have a sourced value.)
Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.
How they compare
The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.
| Material | Yield strength | Tensile strength | Density | Young's modulus | Thermal conductivity | Melting point |
|---|---|---|---|---|---|---|
| Cobaltmagnet, superalloy and battery metal | no data | 760 to 1,135 MPa | 8.9 g/cm³ | 209 to 211 GPa | 100 W/(m·K) | 1,495 °C |
| UNS R30605cobalt-base wrought superalloy for hot gas turbine parts, and CoCrMo cast and wrought grades for orthopaedic implants | 379 to 827 MPa | 655 to 1,172 MPa | 8.3 to 9.13 g/cm³ | 225 GPa | 9.4 W/(m·K) | 1,329 to 1,410 °C |
| Havar (UNS R30004)heat-treatable cobalt-base alloy for high-strength springs, pressure diaphragms and thin foil windows | 483 to 2,068 MPa | 965 to 2,275 MPa | 8.3 g/cm³ | 203 GPa | 13 to 14.7 W/(m·K) | 1,480 °C |
| Phynox (UNS R30003)non-magnetic cobalt-base spring alloy, also sold as Elgiloy, for high-strength springs, diaphragms and thin strip | 1,800 MPa | 689 to 2,620 MPa | 8.3 g/cm³ | 186 to 221 GPa | 12.5 W/(m·K) | no data |
What these materials are made of
Composition by weight, as printed in the sources for each grade (the first constituents listed).
| Material | Main constituents |
|---|---|
| Cobalt | Co 100.0% |
| UNS R30605 | Cr 19 to 21% · W 14 to 16% · Ni 9 to 11% |
| Havar (UNS R30004) | Co 42% · Cr 19.5% · Ni 12.7% · W 2.7% · Mo 2.2% · Mn 1.6% · C 0.2% |
| Phynox (UNS R30003) | Co 40% · Cr 20% · Ni 16% · Mo 7% · Fe 15% |
Where they are used
| Use | Grades |
|---|---|
| Cathode metal in lithium-ion cells (lithium cobalt oxide and nickel-manganese-cobalt cathodes) | Cobalt |
| Cobalt-base superalloys for aircraft gas turbine engines | Cobalt |
| Connectors, thermal switches and microsensors in aerospace electronics | Cobalt |
| Gas turbine combustion chambers and afterburners | UNS R30605 |
| Seal rings, springs and high-temperature ball bearings | UNS R30605 |
| Fan containment in supersonic aircraft (proposed in the study, not built) | UNS R30605 |
| Power springs | Havar (UNS R30004) |
| Metal diaphragms for burst discs | Havar (UNS R30004) |
| Gap spacers in magnetic heads | Havar (UNS R30004) |
| Helical and shaped springs | Phynox (UNS R30003) |
| Parts for satellite communications equipment | Phynox (UNS R30003) |
| Watch springs and axles | Phynox (UNS R30003) |
When each grade fits
| Material | Best for | Weakest at |
|---|---|---|
| Cobalt | Hot magnetic and load-bearing alloys: a Curie temperature of 1115 °C and a melting point of 1495 °C in the pure metal, with cobalt-base superalloys for aircraft gas turbines | Supply and fine powder: Congo (Kinshasa) mined an estimated 73 % of world cobalt in 2025, and finely divided cobalt can ignite in air |
| UNS R30605 | Hot gas-turbine hardware such as combustion parts, afterburners, seal rings and springs that must keep strength to about 1800 °F, and CoCrMo implant parts that need high strength with wear and corrosion resistance | Ductility after long exposure at intermediate temperatures (Rolled Alloys), a low cobalt-alloy hardness that comes only from cold working, and a cost and supply exposure to cobalt and tungsten, both on the critical-mineral list |
| Havar (UNS R30004) | Thin, high-strength springs, diaphragms and foil windows that must stay non-magnetic and resist corrosion in mild acids and seawater | Ductility once age hardened: cold rolled and heat treated strip elongates only 1 % in 2 in, and boiling 96 % sulfuric acid attacks it at 273.76 mils per year |
| Phynox (UNS R30003) | Thin, high-strength springs and diaphragms that must stay non-magnetic and resist corrosion in seawater and sour wells | Joining after age hardening, and no measured corrosion rates in the sources read |
Materials
cobalt-alloys/uns-r30605
Nickel superalloys • 27 sourced entries • 14 sources • 2026
cobalt-alloys/co
Heavy metals • 30 sourced entries • 9 sources • 2026
cobalt-alloys/uns-r30004
Nickel superalloys • 36 sourced entries • 9 sources • 2026
cobalt-alloys/uns-r30003
Nickel superalloys • 27 sourced entries • 10 sources • 2026