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UNS R31233 Cobalt

R31233 cobalt is a cobalt alloy. It is typically furnished in the annealed (O) condition. It has a moderately high melting temperature among cobalt alloys. In addition, it has a moderately low thermal conductivity and a moderately high ductility.

The graph bars on the material properties cards below compare R31233 cobalt to other cobalt alloys (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

220 GPa 32 x 106 psi

Elongation at Break

17 %

Fatigue Strength

220 MPa 32 x 103 psi

Poisson's Ratio


Shear Modulus

85 GPa 12 x 106 psi

Tensile Strength: Ultimate (UTS)

1020 MPa 150 x 103 psi

Tensile Strength: Yield (Proof)

420 MPa 62 x 103 psi

Thermal Properties

Latent Heat of Fusion

320 J/g

Melting Completion (Liquidus)

1350 °C 2470 °F

Melting Onset (Solidus)

1330 °C 2430 °F

Specific Heat Capacity

440 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

12 W/m-K 7.1 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.0 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.1 % IACS

Otherwise Unclassified Properties


8.6 g/cm3 540 lb/ft3

Embodied Carbon

8.4 kg CO2/kg material

Embodied Energy

110 MJ/kg 49 x 103 BTU/lb

Embodied Water

480 L/kg 57 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

140 MJ/m3

Resilience: Unit (Modulus of Resilience)

410 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

23 points

Strength to Weight: Axial

33 points

Strength to Weight: Bending

26 points

Thermal Diffusivity

3.2 m2/s

Thermal Shock Resistance

25 points

Alloy Composition

Cobalt (Co) 44.7 to 63.3
Chromium (Cr) 23.5 to 27.5
Nickel (Ni) 7.0 to 11
Molybdenum (Mo) 4.0 to 6.0
Iron (Fe) 1.0 to 5.0
Tungsten (W) 1.0 to 3.0
Manganese (Mn) 0.1 to 1.5
Silicon (Si) 0.050 to 1.0
Nitrogen (N) 0.030 to 0.12
Carbon (C) 0.020 to 0.1
Phosphorus (P) 0 to 0.030
Sulfur (S) 0 to 0.020
Boron (B) 0 to 0.015

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM B815: Standard Specification for Cobalt-Chromium-Nickel-Molybdenum-Tungsten Alloy (UNS R31233) Rod

ASTM B818: Standard Specification for Cobalt-Chromium-Nickel-Molybdenum-Tungsten Alloy (UNS R31233) Plate, Sheet and Strip

ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys, Joseph R. Davis (editor), 2000

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015