# G-CoCr28 (2.4778) Cobalt-Chromium Alloy

G-CoCr28 cobalt is a cobalt alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 2.4778 is the EN numeric designation for this material. G-CoCr28 is the EN chemical designation.

It has the lowest tensile strength among cobalt alloys. In addition, it has the lowest thermal conductivity and the lowest embodied energy.

The graph bars on the material properties cards below compare G-CoCr28 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

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

Elongation at Break

6.7 *%*

Fatigue Strength

130 *MPa* 19 *x 10 ^{3} psi*

Poisson's Ratio

0.28

Shear Modulus

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

Tensile Strength: Ultimate (UTS)

560 *MPa* 81 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

260 *MPa* 38 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

320 *J/g*

Maximum Temperature: Mechanical

1200 *°C* 2190 *°F*

Melting Completion (Liquidus)

1330 *°C* 2430 *°F*

Melting Onset (Solidus)

1270 *°C* 2310 *°F*

Specific Heat Capacity

470 *J/kg-K* 0.11 *BTU/lb-°F*

Thermal Conductivity

8.5 *W/m-K* 4.9 *BTU/h-ft-°F*

Thermal Expansion

14 *µm/m-K*

## Otherwise Unclassified Properties

Base Metal Price

100 *% relative*

Density

8.1 *g/cm ^{3}* 510

*lb/ft*

^{3}Embodied Carbon

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

Embodied Energy

84 *MJ/kg* 36 *x 10 ^{3} BTU/lb*

Embodied Water

440 *L/kg* 53 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

31 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

160 *kJ/m ^{3}*

Stiffness to Weight: Axial

15 *points*

Stiffness to Weight: Bending

24 *points*

Strength to Weight: Axial

19 *points*

Strength to Weight: Bending

19 *points*

Thermal Diffusivity

2.2 *mm ^{2}/s*

Thermal Shock Resistance

14 *points*

## Alloy Composition

Co | 48 to 52 | |

Cr | 27 to 30 | |

Fe | 9.7 to 24.5 | |

Ni | 0 to 4.0 | |

Si | 0.5 to 1.5 | |

Mn | 0 to 1.5 | |

Mo | 0 to 0.5 | |

Nb | 0 to 0.5 | |

C | 0.050 to 0.25 | |

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

EN 10295: Heat Resistant Steel Castings

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