Precious Metal BAu-4
UNS P00820
BAu-4 is an 82%Au-18%Ni gold-nickel brazing filler (AWS BAu family, UNS P00820) that solidifies as a single-phase solid solution with high oxidation resistance and useful strength at temperature.
Reference datasheet — BAu-4 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
BAu-4 tempers and conditions
BAu-4 is supplied in one standard condition, AS-BRAZED.
Supply forms, finishes and certifications
Ways BAu-4 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FOIL | Foil / Strip | Supply form |
PREFORM | Machined/stamped rings, washers and discs | Supply form |
WIREDefault | Wire / Rod | Supply form |
PASTE | Powder plus organic binder in syringe/cartridge | Printing process |
POWDER | Atomized, −140/+325 mesh for paste and tape blending | Printing process |
What is BAu-4?
BAu-4 is an 82%Au-18%Ni gold-nickel brazing filler (AWS BAu family, UNS P00820) that solidifies as a single-phase solid solution with high oxidation resistance and useful strength at temperature. It is the standard choice for brazing nickel-based superalloys and stainless steel in aerospace turbine assemblies, and is supplied as wire, foil, powder, paste and stamped preforms. As-brazed properties are about 340 MPa tensile, 210 MPa yield and 25% elongation, with a formability rating of 78. Cost is driven almost entirely by the gold content, so a lower-gold BAu grade or a Ni-based filler is used wherever the joint temperature allows. BAu-4 has a density of 15.9 g/cm³ (0.574 lb/in³), heavier than 81% of precious metal grades. It melts at 950°C (1,742 °F). BAu-4 has a yield strength of 210 MPa (30.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — stronger than 61% of precious metal grades. Elongation at break is 25% and the elastic modulus is 105 GPa (15.2 Msi).
What is BAu-4 used for?
- Jet engine component brazing
- Nickel superalloy joints
- High-temperature vacuum furnace parts
- Turbine seal assemblies
Advantages
- High service temperature — 800°C (1,472 °F), better than 90% of precious metal grades
Limitations
- Low electrical conductivity — 7 % IACS, worse than 89% of precious metal grades
- High embodied carbon — 14,000 kg CO₂/kg, worse than 88% of precious metal grades
- Heavy — 15.9 g/cm³ (0.574 lb/in³), worse than 81% of precious metal grades
BAu-4 properties
Typical room-temperature values; bars are the position among precious metal grades.
Physical3
BAu-4 has a density of 15.9 g/cm³ (0.574 lb/in³), heavier than 81% of precious metal grades. It melts at 950°C (1,742 °F).
Mechanical9
BAu-4 has a yield strength of 210 MPa (30.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — stronger than 61% of precious metal grades. Elongation at break is 25% and the elastic modulus is 105 GPa (15.2 Msi).
Thermal6
BAu-4 is rated for continuous service to 800°C (1,472 °F). It conducts heat at 60 W/m·K (34.7 BTU/hr·ft·°F), worse than 72% of precious metal grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
BAu-4 conducts electricity at 7 % IACS, worse than 89% of precious metal grades.
Chemical & Environmental2
Corrosion resistance is excellent (92/100), better than 73% of precious metal grades.
Sustainability4
Producing a kilogram of BAu-4 takes about 205,000 MJ of energy and emits 14,000 kg of CO₂ — more than 87% of precious metal grades. Typical recycled content is 45%.
Manufacturability6
BAu-4's machinability is fair (35/100, worse than 73% of precious metal grades); weldability fair (40/100); formability very good (75/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the precious metal family
Yield strength against density for every precious metal grade FabDigit runs. BAu-4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BAu-4
Is BAu-4 easy to machine?
Soft and gummy — use sharp, polished carbide or HSS tooling, light cuts and full swarf capture for precious-metal recovery.
Can BAu-4 be welded?
Not a structural weld alloy; joints are made by vacuum or dry-hydrogen furnace brazing at 950–1010 °C with short dwell to limit Ni erosion of thin sections.
Can BAu-4 be formed, bent or molded?
Excellent cold ductility — readily drawn to fine wire, rolled to <50 µm foil and stamped into preforms with interstage annealing.
BAu-4 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 |
|---|---|---|
| Augold, per AWS A5.8 BAu-4 / UNS P00820 | 81.5 – 82.5 | 82 |
| Other (total)total of all other elements, including impurities | ≤ 0.15 | |
| Ni | balance |
What surface finishes work on BAu-4?
Braze fillets need no coating; light ultrasonic or acid cleaning removes flux/binder residues, and the joint takes a bright polish without plating.
Equivalent designations
Standards and trade names that resolve to Precious Metal BAu-4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- P00820
- Also called
- AWS BAu-4
How much does BAu-4 cost?
BAu-4 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BAu-4 — frequently asked
What is BAu-4 used for?
BAu-4 is typically used for jet engine component brazing, nickel superalloy joints, high-temperature vacuum furnace parts and turbine seal assemblies. In short: high-temperature BAu filler; oxidation-resistant Au-Ni braze; superalloy brazing standard.
What is the yield strength of BAu-4?
BAu-4 has a typical yield strength of 210 MPa (30.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — stronger than 61% of precious metal grades.
Is BAu-4 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 73% of precious metal grades). Soft and gummy — use sharp, polished carbide or HSS tooling, light cuts and full swarf capture for precious-metal recovery.
Can BAu-4 be welded?
With care — weldability is rated fair (40/100). Not a structural weld alloy; joints are made by vacuum or dry-hydrogen furnace brazing at 950–1010 °C with short dwell to limit Ni erosion of thin sections.
What surface finishes work on BAu-4?
Braze fillets need no coating; light ultrasonic or acid cleaning removes flux/binder residues, and the joint takes a bright polish without plating.
Can BAu-4 be formed, bent or molded?
Excellent cold ductility — readily drawn to fine wire, rolled to <50 µm foil and stamped into preforms with interstage annealing.
What is the maximum service temperature of BAu-4?
BAu-4 is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BAu-4 cost?
BAu-4 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.8M/A5.8:2019 Specification for Filler Metals for Brazing and Braze Welding — American Welding Society (2019)
- ASM Handbook Vol.6 — Welding, Brazing and Soldering (Gold brazing filler metals) — ASM International (1993)
- Brazing Handbook, 5th ed. — American Welding Society (2007)
- Gold-nickel braze filler metal (Au-18Ni) product data — precious-metal braze producers (Materion / Umicore / ) (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.