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Nickel Alloy BNi-4 DIFF-BRAZED

Heat-treated state

UNS N99640 · ISO B-Ni4

Long hold above the braze temperature dissolves boride centre-line, raising joint remelt temperature and ductility.

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Values for the DIFF-BRAZED condition

Other BNi-4 tempers and conditions

BNi-4 is listed in 2 conditions; see the grade overview at BNi-4.

Compare all 2 conditionsHide
Condition · open for datasheetBest forYield MPaTensile MPaElong. %HardnessConductivity
DIFF-BRAZEDThis page
Diffusion-brazed / post-braze diffusion heat treated joint
Long hold above the braze temperature dissolves boride centre-line, raising joint remelt temperature and ductility.350560625 HRC1.9 % IACS
AS-BRAZED
As-brazed joint (deposited filler metal)
Design condition for joint strength after a 1010–1175 °C vacuum or dry-hydrogen braze cycle.400450233 HRC1.6 % IACS

What is BNi-4 DIFF-BRAZED?

BNi-4 DIFF-BRAZED is BNi-4 heat treated to DIFF-BRAZED — long hold above the braze temperature dissolves boride centre-line, raising joint remelt temperature and ductility. BNi-4 DIFF-BRAZED has a tensile strength of 560 MPa (81.2 ksi), weaker than 74% of nickel alloy grades. Elongation at break is 6% and the elastic modulus is 195 GPa (28.3 Msi). BNi-4 DIFF-BRAZED 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).

Advantages

  • Conducts heat well — 35 W/m·K (20.2 BTU/hr·ft·°F), better than 95% of nickel alloy grades

Limitations

  • Hard to polish — 55/100, worse than 95% of nickel alloy grades
  • Needs corrosion protection — 48/100, worse than 93% of nickel alloy grades
  • Limited ductility — 6%, worse than 90% of nickel alloy grades
  • Difficult to weld — 20/100, worse than 84% of nickel alloy grades

BNi-4 DIFF-BRAZED properties

Typical room-temperature values for BNi-4 DIFF-BRAZED; 23 are specific to this condition. Other listed values are BNi-4 reference data and may not represent this condition. Bars are the position among nickel alloy grades.

Physical3

BNi-4 DIFF-BRAZED 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).

Density8.2 g/cm³0.3 lb/in³
Melting Point (Solidus)980°C1,796 °F
Liquidus Temperature1,065°C1,949 °F

Mechanical8

BNi-4 DIFF-BRAZED has a tensile strength of 560 MPa (81.2 ksi), weaker than 74% of nickel alloy grades. Elongation at break is 6% and the elastic modulus is 195 GPa (28.3 Msi).

Elastic (Young's) Modulus195 GPa28.3 Msi
Shear Modulus73 GPa10.6 Msi
Poisson's Ratio0.31
Tensile Strength (Ultimate)560 MPa81.2 ksi
Elongation at Break6%
Shear Strength300 MPa43.5 ksi
Hardness, Rockwell C25 HRC
Hardness, Vickers255 HV

Thermal6

BNi-4 DIFF-BRAZED is rated for continuous service to 980°C (1,796 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), better than 95% of nickel alloy grades. Thermal expansion is 13.5 µm/m·K (7.5 µin/in·°F).

Thermal Conductivity35 W/m·K20.2 BTU/hr·ft·°F
Specific Heat Capacity460 J/kg·K0.11 BTU/lb·°F
Thermal Expansion (CTE, 20–100 °C)13.5 µm/m·K7.5 µin/in·°F
Latent Heat of Fusion285 J/g123 BTU/lb
Max Service Temperature (continuous)980°C1,796 °F
Min Service Temperature-196°C-321 °F

Electrical2

BNi-4 DIFF-BRAZED has an electrical resistivity of 9.2×10⁻⁷ Ω·m.

Electrical Resistivity9.2×10⁻⁷ Ω·m36.2 µΩ·in
Magnetic Responseweakly magnetic

Chemical & Environmental3

Corrosion resistance is fair (48/100), worse than 93% of nickel alloy grades.

Galvanic Potential (seawater, vs SCE)-0.2 V
Corrosion ResistanceFair48/100
Chemical Resistance SummaryGood in dry oxidising gas and neutral water up to ~900 °C; no chromium means poor resistance to wet corrosion, chlorides, sulphur-bearing atmospheres and strong acids compared with Cr-bearing BNi grades.

Sustainability4

Producing a kilogram of BNi-4 DIFF-BRAZED takes about 185 MJ of energy and emits 14 kg of CO₂ — more than 73% of nickel alloy grades. Typical recycled content is 15%.

Embodied Energy (primary production)185 MJ/kg79,536 BTU/lb
Embodied Carbon (primary production)14 kg CO₂/kg
Embodied Water300 L/kg35.9 gal/lb
Typical Recycled Content15%

Manufacturability5

BNi-4 DIFF-BRAZED's machinability is poor (18/100, worse than 61% of nickel alloy grades); weldability poor (20/100).

MachinabilityPoor18/100
WeldabilityPoor20/100
CastabilityGood60/100
Brazeability / SolderabilityExcellent92/100
PolishabilityGood55/100

Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.

Working with BNi-4 DIFF-BRAZED

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.

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.

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.

ElementSpec limit (wt %)Nominal
Si3 – 43.5
B1.5 – 2.21.8
Fe≤ 1.50.5
C≤ 0.060.03
P≤ 0.02—
S≤ 0.02—
Al≤ 0.05—
Ti≤ 0.05—
Zr≤ 0.05—
Other elements, total≤ 0.5—
Nibalance—

BNi-4 DIFF-BRAZED — frequently asked

What is BNi-4 DIFF-BRAZED used for?

BNi-4 DIFF-BRAZED 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 DIFF-BRAZED?

BNi-4 DIFF-BRAZED has a typical tensile strength of 560 MPa (81.2 ksi) — weaker than 74% of nickel alloy grades. Strength varies by condition: see the 2 listed tempers.

Is BNi-4 DIFF-BRAZED easy to machine?

Not especially — machinability is rated poor (18/100, worse than 61% 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 DIFF-BRAZED be welded?

Not readily — weldability is rated poor (20/100). 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 DIFF-BRAZED?

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 DIFF-BRAZED 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 DIFF-BRAZED?

BNi-4 DIFF-BRAZED is rated for continuous use to about 980°C (1,796 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.

Sources

  1. AWS A5.8/A5.8M Specification for Filler Metals for Brazing and Braze Welding — American Welding Society (2019)
  2. ASM Handbook Vol. 6 — Welding, Brazing and Soldering (Nickel brazing filler metals) — ASM International (1993)
  3. AWS Brazing Handbook, 5th ed. — American Welding Society (2007)
  4. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.