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UNS R30816 (formerly Grade 671) Cobalt

R30816 cobalt is a cobalt alloy. Cited properties are appropriate for the annealed and aged condition. R30816 is the UNS number for this material. Older literature may refer to this material as ASTM Grade 671, but this is now discouraged.

It has the highest embodied energy among cobalt alloys. In addition, it has a very high melting temperature and a fairly low heat capacity.

The graph bars on the material properties cards below compare R30816 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

Brinell Hardness


Elastic (Young's, Tensile) Modulus

210 GPa 31 x 106 psi

Elongation at Break

23 %

Fatigue Strength

250 MPa 36 x 103 psi

Poisson's Ratio


Reduction in Area

22 %

Shear Modulus

81 GPa 12 x 106 psi

Tensile Strength: Ultimate (UTS)

1020 MPa 150 x 103 psi

Tensile Strength: Yield (Proof)

460 MPa 67 x 103 psi

Thermal Properties

Latent Heat of Fusion

300 J/g

Melting Completion (Liquidus)

1540 °C 2800 °F

Melting Onset (Solidus)

1460 °C 2660 °F

Specific Heat Capacity

420 J/kg-K 0.1 BTU/lb-°F

Thermal Conductivity

13 W/m-K 7.3 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Otherwise Unclassified Properties


9.1 g/cm3 570 lb/ft3

Embodied Carbon

20 kg CO2/kg material

Embodied Energy

320 MJ/kg 140 x 103 BTU/lb

Embodied Water

440 L/kg 52 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

190 MJ/m3

Resilience: Unit (Modulus of Resilience)

510 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

22 points

Strength to Weight: Axial

31 points

Strength to Weight: Bending

25 points

Thermal Diffusivity

3.3 mm2/s

Thermal Shock Resistance

28 points

Alloy Composition

Cobalt (Co)Co 40 to 49.8
Nickel (Ni)Ni 19 to 21
Chromium (Cr)Cr 19 to 21
Molybdenum (Mo)Mo 3.5 to 4.5
Tungsten (W)W 3.5 to 4.5
Niobium (Nb)Nb 3.5 to 4.5
Tantalum (Ta)Ta 3.5 to 4.5
Iron (Fe)Fe 0 to 5.0
Manganese (Mn)Mn 1.0 to 2.0
Silicon (Si)Si 0 to 1.0
Carbon (C)C 0.32 to 0.42
Phosphorus (P)P 0 to 0.040
Sulfur (S)S 0 to 0.030

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

Followup Questions

Similar Alloys

Further Reading

ASTM B639: Standard Specification for Precipitation Hardening Cobalt-Containing Alloys (UNS R30155 and UNS R30816) Rod, Bar, Forgings, and Forging Stock for High-Temperature Service

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