Cobalt-Chrome Alloy AWS BCo-1 DIFFUSION
Heat-treated state
UNS R39001
Pick when joint ductility, remelt temperature and stress-rupture life must be raised for hot-section service.
Values for the DIFFUSION condition
Other AWS BCo-1 tempers and conditions
AWS BCo-1 is listed in 2 conditions; see the grade overview at AWS BCo-1.
- AS-BRAZED
- DIFFUSION
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As-brazed joint (1149–1204 °C, vacuum or dry H₂, no diffusion cycle) | Property set for the solidified seam straight out of the braze cycle — hardest and most brittle condition. | 400 | 450 | 1 | 55 HRC | 1.5 % IACS |
DIFFUSIONThis page Brazed + diffusion heat treatment (hold near/above braze temperature to homogenize B/Si) | Pick when joint ductility, remelt temperature and stress-rupture life must be raised for hot-section service. | 470 | 620 | 4 | 43 HRC | 1.7 % IACS |
What is AWS BCo-1 DIFFUSION?
AWS BCo-1 DIFFUSION is AWS BCo-1 heat treated to DIFFUSION — pick when joint ductility, remelt temperature and stress-rupture life must be raised for hot-section service. AWS BCo-1 DIFFUSION has a density of 8.4 g/cm³ (0.303 lb/in³), lighter than 57% of cobalt-chrome alloy grades. It melts at 1,121°C (2,050 °F).
Advantages
- High service temperature — 1,050°C (1,922 °F), better than 100% of cobalt-chrome alloy grades
Limitations
- Difficult to weld — 15/100, worse than 96% of cobalt-chrome alloy grades
AWS BCo-1 DIFFUSION properties
Typical room-temperature values for AWS BCo-1 DIFFUSION; 22 are specific to this condition. Other listed values are AWS BCo-1 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
AWS BCo-1 DIFFUSION has a density of 8.4 g/cm³ (0.303 lb/in³), lighter than 57% of cobalt-chrome alloy grades. It melts at 1,121°C (2,050 °F).
Mechanical3
Thermal5
AWS BCo-1 DIFFUSION is rated for continuous service to 1,050°C (1,922 °F). It conducts heat at 14.5 W/m·K (8.38 BTU/hr·ft·°F), better than 64% of cobalt-chrome alloy grades. Thermal expansion is 13.8 µm/m·K (7.67 µin/in·°F).
Electrical2
AWS BCo-1 DIFFUSION has an electrical resistivity of 1.02×10⁻⁶ Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (72/100), worse than 61% of cobalt-chrome alloy grades.
Sustainability3
Producing a kilogram of AWS BCo-1 DIFFUSION takes about 155 MJ of energy and emits 12 kg of CO₂ — more than 52% of cobalt-chrome alloy grades. Typical recycled content is 10%.
Manufacturability4
AWS BCo-1 DIFFUSION's machinability is not recommended (10/100, better than 52% of cobalt-chrome alloy grades); weldability poor (15/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AWS BCo-1 DIFFUSION
Is AWS BCo-1 easy to machine?
The alloy is never machined as a bulk product; the as-brazed seam is hard and brittle — dress only by grinding with SiC/diamond wheels.
Can AWS BCo-1 be welded?
Not a welding consumable: fusion welding of the boron-bearing seam cracks; repair by re-brazing in a fresh furnace cycle.
Can AWS BCo-1 be formed, bent or molded?
B and Si make the alloy unworkable, so it is atomized to powder and supplied as paste, transfer tape or pressed/sintered preforms.
What surface finishes work on AWS BCo-1?
Vacuum or dry-hydrogen brazing at 1149–1204 °C with 0.025–0.075 mm joint clearance and scrupulously clean, oxide-free surfaces; add a post-braze diffusion cycle to raise remelt temperature and reduce seam brittleness.
AWS BCo-1 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Croxidation/sulfidation resistance | 18 – 20 | 19 |
| Ni | 16 – 18 | 17 |
| Wsolid-solution strengthening | 3 – 4 | 4 |
| Simelting point depressant | 7.5 – 8.5 | 8 |
| Bmelting point depressant; diffuses into base metal | 0.7 – 0.9 | 0.8 |
| C | 0.35 – 0.45 | 0.4 |
| Fe | ≤ 1 | — |
| other (total)total of all other elements, max | ≤ 0.5 | — |
| Cobalance, ~ 50 % | balance | — |
AWS BCo-1 DIFFUSION — frequently asked
What is AWS BCo-1 DIFFUSION used for?
AWS BCo-1 DIFFUSION is typically used for hardfacing overlays, valve seats, pump sleeves and wear plates. In short: cobalt-base brazing filler; 980 °C joint service; not a welding consumable.
Is AWS BCo-1 DIFFUSION easy to machine?
Not especially — machinability is rated not recommended (10/100, better than 52% of cobalt-chrome alloy grades). The alloy is never machined as a bulk product; the as-brazed seam is hard and brittle — dress only by grinding with SiC/diamond wheels.
Can AWS BCo-1 DIFFUSION be welded?
Not readily — weldability is rated poor (15/100). Not a welding consumable: fusion welding of the boron-bearing seam cracks; repair by re-brazing in a fresh furnace cycle.
What surface finishes work on AWS BCo-1 DIFFUSION?
Vacuum or dry-hydrogen brazing at 1149–1204 °C with 0.025–0.075 mm joint clearance and scrupulously clean, oxide-free surfaces; add a post-braze diffusion cycle to raise remelt temperature and reduce seam brittleness.
Can AWS BCo-1 DIFFUSION be formed, bent or molded?
B and Si make the alloy unworkable, so it is atomized to powder and supplied as paste, transfer tape or pressed/sintered preforms.
What is the maximum service temperature of AWS BCo-1 DIFFUSION?
AWS BCo-1 DIFFUSION is rated for continuous use to about 1,050°C (1,922 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- AWS A5.8/A5.8M — Specification for Filler Metals for Brazing and Braze Welding (BCo-1, UNS R39001) — American Welding Society (2019)
- ASM Handbook Vol.6 — Welding, Brazing and Soldering (cobalt-base brazing filler metals) — ASM International (1993)
- ASM Specialty Handbook: Nickel, Cobalt and Their Alloys — ASM International (2000)
- High-temperature braze powder / paste datasheets (Co-base BCo-1 type) — Höganäs / Wall Colmonoy / Lucas-Milhaupt (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.