Cobalt–Nickel (Co–Ni) alloys are high-performance metallic systems that combine the high-temperature strength, wear resistance, and magnetic behavior of cobalt with the corrosion resistance, toughness, and ductility of nickel. These alloys are engineered for extreme environments where conventional steels and alloys fail.
Alloy System Overview
| Alloy Type | Typical Composition | Primary Focus |
|---|---|---|
| High-Ni Co–Ni | Ni 60–80%, Co balance | Corrosion resistance & ductility |
| High-Co Co–Ni | Co 60–80%, Ni balance | High-temperature strength & wear |
| Low-Expansion Alloys | Co–Ni–Fe | Dimensional stability |
| Magnetic Co–Ni | Controlled Co/Ni ratios | Magnetic performance |
Chemical Composition (Typical Ranges)
| Element | Range (wt%) |
|---|---|
| Cobalt (Co) | 20 – 80 |
| Nickel (Ni) | 20 – 80 |
| Chromium (Cr) | 0 – 30 |
| Molybdenum (Mo) | 0 – 10 |
| Iron (Fe) | 0 – 30 |
| Carbon (C) | ≤ 0.25 |
Key Mechanical Properties
| Property | Typical Range |
|---|---|
| Tensile Strength | 600 – 1200 MPa |
| Yield Strength | 300 – 900 MPa |
| Elongation | 10 – 40% |
| Hardness | 30 – 55 HRC |
| Fatigue Resistance | Excellent |
| Wear Resistance | Outstanding |
Physical Properties
| Property | Typical Value |
|---|---|
| Density | 8.3 – 9.1 g/cm³ |
| Melting Range | 1300 – 1500 °C |
| Elastic Modulus | 200 – 230 GPa |
| Thermal Expansion | 10 – 14 µm/m·K |
| Magnetic Behavior | Ferromagnetic / tunable |
Strengthening & Metallurgical Behavior
• FCC-dominant structure (Ni-rich systems)
• HCP ↔ FCC transformation in Co-rich alloys
• Solid-solution strengthening from Co–Ni interaction
• Carbide precipitation when Cr/Mo/C are present
• Excellent resistance to thermal softening
Corrosion & Environmental Resistance
Co–Ni alloys provide strong resistance to oxidation, hot corrosion, acids, alkalis, and aggressive chemical environments. Chromium and molybdenum additions further enhance corrosion performance.
Available Forms
Bars & rods
Sheets & plates
Tubes & pipes
Wire & foils
Powders (gas-atomized)
Castings & forgings
Applications
Aerospace
Turbine components
High-temperature fasteners
Bearings and wear surfaces
Medical
Orthopedic implants
Dental prosthetics
Surgical instruments
Magnetic & Electronics
Permanent magnets
Recording media
Precision sensors
Energy & Industrial
Catalysts
High-pressure valves
Hardfacing alloys
Advantages
✔ Exceptional high-temperature strength
✔ Outstanding wear & fatigue resistance
✔ Superior corrosion & oxidation resistance
✔ Tunable magnetic properties
✔ Long service life in extreme environments
Limitations
❌ High material and processing cost
❌ Difficult machining
❌ Higher density than Al/Ti alloys
❌ Over-engineered for low-stress use
Why Choose Cobalt–Nickel Alloys?
Choose Co–Ni alloys when strength, wear, corrosion, magnetic control, and thermal stability must coexist under extreme operating conditions.
Cobalt–Nickel alloys are elite engineering materials, trusted where failure is not an option.