# 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

280

Elastic (Young's, Tensile) Modulus

210 *GPa* 31 *x 10 ^{6} psi*

Elongation at Break

23 *%*

Fatigue Strength

250 *MPa* 36 *x 10 ^{3} psi*

Poisson's Ratio

0.3

Reduction in Area

22 *%*

Shear Modulus

81 *GPa* 12 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

1020 *MPa* 150 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

460 *MPa* 67 *x 10 ^{3} 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

Density

9.1 *g/cm ^{3}* 570

*lb/ft*

^{3}Embodied Carbon

20 *kg CO _{2}/kg material*

Embodied Energy

320 *MJ/kg* 140 *x 10 ^{3} BTU/lb*

Embodied Water

440 *L/kg* 52 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

190 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

510 *kJ/m ^{3}*

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 *m ^{2}/s*

Thermal Shock Resistance

28 *points*

## Alloy Composition

Co | 40 to 49.8 | |

Ni | 19 to 21 | |

Cr | 19 to 21 | |

Mo | 3.5 to 4.5 | |

W | 3.5 to 4.5 | |

Nb | 3.5 to 4.5 | |

Ta | 3.5 to 4.5 | |

Fe | 0 to 5.0 | |

Mn | 1.0 to 2.0 | |

Si | 0 to 1.0 | |

C | 0.32 to 0.42 | |

P | 0 to 0.040 | |

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