Dispersion Strengthened Co-28Cr-6Mo Alloy (ASTM F1537 Alloy 3, R31539)
R31539 cobalt is a cobalt alloy. ASTM F1537 Alloy 3 is the ASTM designation for this material. R31539 is the UNS number.
The properties of R31539 cobalt include three common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare R31539 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
13 to 22 %
Fatigue Strength
310 to 480 MPa 45 to 70 x 103 psi
Poisson's Ratio
0.29
Reduction in Area
13 to 23 %
Rockwell C Hardness
25 to 35
Shear Modulus
86 GPa 13 x 106 psi
Tensile Strength: Ultimate (UTS)
1000 to 1340 MPa 150 to 190 x 103 psi
Tensile Strength: Yield (Proof)
590 to 940 MPa 85 to 140 x 103 psi
Thermal Properties
Latent Heat of Fusion
320 J/g
Melting Completion (Liquidus)
1360 °C 2470 °F
Melting Onset (Solidus)
1290 °C 2350 °F
Specific Heat Capacity
450 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
13 W/m-K 7.6 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
Density
8.4 g/cm3 520 lb/ft3
Embodied Carbon
8.2 kg CO2/kg material
Embodied Energy
110 MJ/kg 46 x 103 BTU/lb
Embodied Water
530 L/kg 64 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
140 to 190 MJ/m3
Resilience: Unit (Modulus of Resilience)
780 to 2000 kJ/m3
Stiffness to Weight: Axial
15 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
33 to 44 points
Strength to Weight: Bending
27 to 32 points
Thermal Diffusivity
3.5 mm2/s
Thermal Shock Resistance
24 to 32 points
Alloy Composition
| Co | 57.7 to 68.7 | |
| Cr | 26 to 30 | |
| Mo | 5.0 to 7.0 | |
| Al | 0.3 to 1.0 | |
| Mn | 0 to 1.0 | |
| Si | 0 to 1.0 | |
| Ni | 0 to 1.0 | |
| Fe | 0 to 0.75 | |
| N | 0 to 0.25 | |
| La | 0.030 to 0.2 | |
| C | 0 to 0.14 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM F799: Standard Specification for Cobalt-28Chromium-6Molybdenum Alloy Forgings for Surgical Implants (UNS R31537, R31538, R31539)
ASTM F1537: Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539)
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015