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AWS BCo-1 (R39001) Filler Metal

AWS BCo-1 is a cobalt alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. BCo-1 is the AWS designation for this material. R39001 is the UNS number. It has the lowest melting temperature and a fairly low tensile strength among cobalt alloys.

The graph bars on the material properties cards below compare AWS BCo-1 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

200 GPa 29 x 106 psi

Poisson's Ratio


Shear Modulus

78 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

700 MPa 100 x 103 psi

Thermal Properties

Brazing Temperature

1150 to 1230 °C 2100 to 2250 °F

Latent Heat of Fusion

420 J/g

Melting Completion (Liquidus)

1150 °C 2100 °F

Melting Onset (Solidus)

1120 °C 2050 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Expansion

12 µm/m-K

Otherwise Unclassified Properties


8.1 g/cm3 510 lb/ft3

Embodied Carbon

8.0 kg CO2/kg material

Embodied Energy

110 MJ/kg 48 x 103 BTU/lb

Embodied Water

430 L/kg 51 gal/lb

Common Calculations

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

24 points

Strength to Weight: Bending

22 points

Thermal Shock Resistance

21 points

Alloy Composition

Cobalt (Co)Co 46 to 54
Chromium (Cr)Cr 18 to 20
Nickel (Ni)Ni 16 to 18
Silicon (Si)Si 7.5 to 8.5
Tungsten (W)W 3.5 to 4.5
Boron (B)B 0.7 to 0.9
Iron (Fe)Fe 0 to 1.0
Carbon (C)C 0.35 to 0.45
Aluminum (Al)Al 0 to 0.050
Titanium (Ti)Ti 0 to 0.050
Zirconium (Zr)Zr 0 to 0.050
Phosphorus (P)P 0 to 0.020
Sulfur (S)S 0 to 0.020
Selenium (Se)Se 0 to 0.0050
Residualsres. 0 to 0.5

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

Followup Questions

Similar Alloys

Further Reading

AWS A5.8: Specification for Filler Metals for Brazing and Braze Welding