Nickel Alloy BNi-4
UNS N99640 · ISO B-Ni4
BNi-4 is a nickel-silicon-boron brazing filler metal (UNS N99640) from the AWS A5.8 nickel braze family, formulated with lower boron than BNi-3.
Reference datasheet — BNi-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.
BNi-4 tempers and conditions
BNi-4 is supplied in 2 conditions, soft to hard.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Diffusion-brazed / post-braze diffusion heat treated joint | Long hold above the braze temperature dissolves boride centre-line, raising joint remelt temperature and ductility. | 350 | 560 | 6 | 25 HRC | 1.9 % IACS |
As-brazed joint (deposited filler metal) | Design condition for joint strength after a 1010–1175 °C vacuum or dry-hydrogen braze cycle. | 400 | 450 | 2 | 33 HRC | 1.6 % IACS |
Supply forms, finishes and certifications
Ways BNi-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 | Amorphous/ductile ribbon foil preform | Supply form |
PASTE | Braze paste | Printing process |
POWDERDefault | Atomised powder | Printing process |
TAPE | Transfer tape / flexible sheet preform | Printing process |
What is BNi-4?
BNi-4 is a nickel-silicon-boron brazing filler metal (UNS N99640) from the AWS A5.8 nickel braze family, formulated with lower boron than BNi-3. It is selected for joints sensitive to boride embrittlement, such as thin-wall stainless assemblies, and is supplied as powder, paste, foil and tape; the deposit has a density of 8.2 g/cm3 and an as-brazed hardness near 33 HRC. The deposit contains no chromium, so it oxidises above roughly 900 C and needs a coating or parent-metal passivation for aggressive service. Where high-temperature oxidation resistance governs, BNi-5 is the nearest alternative. BNi-4 has a density of 8.2 g/cm³ (0.296 lb/in³), lighter than 63% of nickel alloy grades. It melts at 980°C (1,796 °F). BNi-4 has a tensile strength of 450 MPa (65.3 ksi), weaker than 94% of nickel alloy grades. Elongation at break is 2% and the elastic modulus is 190 GPa (27.6 Msi).
What is BNi-4 used for?
- ductile joint brazing
- stainless steel assemblies
- food and medical equipment brazing
Advantages
- Conducts heat well — 30 W/m·K (17.3 BTU/hr·ft·°F), better than 93% of nickel alloy grades
Limitations
- Limited ductility — 2%, worse than 95% of nickel alloy grades
- Hard to polish — 55/100, worse than 95% of nickel alloy grades
- Needs corrosion protection — 42/100, worse than 94% of nickel alloy grades
- Difficult to weld — 15/100, worse than 87% of nickel alloy grades
BNi-4 properties
Typical room-temperature values; bars are the position among nickel alloy grades.
Physical3
BNi-4 has a density of 8.2 g/cm³ (0.296 lb/in³), lighter than 63% of nickel alloy grades. It melts at 980°C (1,796 °F).
Mechanical8
BNi-4 has a tensile strength of 450 MPa (65.3 ksi), weaker than 94% of nickel alloy grades. Elongation at break is 2% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal6
BNi-4 is rated for continuous service to 900°C (1,652 °F). It conducts heat at 30 W/m·K (17.3 BTU/hr·ft·°F), better than 93% of nickel alloy grades. Thermal expansion is 13.5 µm/m·K (7.5 µin/in·°F).
Electrical2
BNi-4 has an electrical resistivity of 1.1×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 94% of nickel alloy grades.
Sustainability4
Producing a kilogram of BNi-4 takes about 185 MJ of energy and emits 14 kg of CO₂ — more than 73% of nickel alloy grades. Typical recycled content is 15%.
Manufacturability5
BNi-4's machinability is not recommended (12/100, worse than 86% of nickel alloy grades); weldability poor (15/100).
Common Calculations4
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 nickel alloy family
Yield strength against density for every nickel alloy grade FabDigit runs. BNi-4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BNi-4
Is BNi-4 easy to machine?
Solidified filler is hard and boride-bearing — remove excess fillets by grinding or EDM rather than turning; keep joint clean-up to a minimum.
Can BNi-4 be welded?
Not a fusion-welding filler; braze in vacuum (10⁻⁴ mbar range) or dry hydrogen at 1010–1175 °C with joint clearances of about 0.025–0.10 mm.
Can BNi-4 be formed, bent or molded?
Supplied as powder, paste, tape or rapidly-solidified ribbon; only the amorphous ribbon can be cut and formed into preforms.
BNi-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 |
|---|---|---|
| Si | 3 – 4 | 3.5 |
| B | 1.5 – 2.2 | 1.8 |
| Fe | ≤ 1.5 | 0.5 |
| C | ≤ 0.06 | 0.03 |
| P | ≤ 0.02 | |
| S | ≤ 0.02 | |
| Al | ≤ 0.05 | |
| Ti | ≤ 0.05 | |
| Zr | ≤ 0.05 | |
| Other elements, total | ≤ 0.5 | |
| Ni | balance |
What surface finishes work on BNi-4?
Chromium-free deposit oxidises above ~900 °C — apply aluminide or Cr-rich coatings, or passivate the parent stainless after brazing, for aggressive service.
Surface treatments FabDigit runs on nickel alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Nickel Alloy BNi-4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N99640
- ISO
- B-Ni4
How much does BNi-4 cost?
BNi-4 is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BNi-4 — frequently asked
What is BNi-4 used for?
BNi-4 is typically used for ductile joint brazing, stainless steel assemblies and food and medical equipment brazing. In short: lower boron than BNi-3; more ductile brazed joints; chromium-free deposit.
What is the tensile strength of BNi-4?
BNi-4 has a typical tensile strength of 450 MPa (65.3 ksi) — weaker than 94% of nickel alloy grades. Strength varies by condition: see the 2 listed tempers.
Is BNi-4 easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 86% of nickel alloy grades). Solidified filler is hard and boride-bearing — remove excess fillets by grinding or EDM rather than turning; keep joint clean-up to a minimum.
Can BNi-4 be welded?
Not readily — weldability is rated poor (15/100). Not a fusion-welding filler; braze in vacuum (10⁻⁴ mbar range) or dry hydrogen at 1010–1175 °C with joint clearances of about 0.025–0.10 mm.
What surface finishes work on BNi-4?
Chromium-free deposit oxidises above ~900 °C — apply aluminide or Cr-rich coatings, or passivate the parent stainless after brazing, for aggressive service.
Can BNi-4 be formed, bent or molded?
Supplied as powder, paste, tape or rapidly-solidified ribbon; only the amorphous ribbon can be cut and formed into preforms.
What is the maximum service temperature of BNi-4?
BNi-4 is rated for continuous use to about 900°C (1,652 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BNi-4 cost?
BNi-4 is a high-cost nickel alloy ($$$$), 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 A5.8/A5.8M Specification for Filler Metals for Brazing and Braze Welding — American Welding Society (2019)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering (Nickel brazing filler metals) — ASM International (1993)
- AWS Brazing Handbook, 5th ed. — American Welding Society (2007)
- Nickel braze filler metal powder/paste/foil datasheets (Ni-Si-B family) — Various braze alloy producers (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.