Nickel Alloy BNi-5a
UNS N99651 · ISO B-Ni5a
BNi-5a is a modified BNi-5 nickel braze filler (UNS N99651) with adjusted boron and silicon for improved flow while retaining the high-chromium oxidation resistance of the AWS A5.8 nickel braze family.
Reference datasheet — BNi-5a 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-5a tempers and conditions
BNi-5a 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 |
|---|---|---|---|---|---|---|
no post-braze diffusion cycle | Baseline condition straight out of the vacuum furnace; hardest and most brittle because of retained centreline borides. | 420 | 480 | 1 | 55 HRC | 1.3 % IACS |
Diffusion heat treated after brazing | Select where joint ductility, higher remelt temperature and creep life matter; boron diffuses into the parent metal and the brittle centreline is largely eliminated. | 430 | 650 | 5 | 36 HRC | 1.6 % IACS |
Supply forms, finishes and certifications
Ways BNi-5a is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
PREFORM | Sintered preform | Supply form |
PASTE | Powder pre-mixed with organic binder | Printing process |
POWDERDefault | Gas-atomized brazing powder | Printing process |
TAPE | Transfer tape / flexible sheet preform | Printing process |
What is BNi-5a?
BNi-5a is a modified BNi-5 nickel braze filler (UNS N99651) with adjusted boron and silicon for improved flow while retaining the high-chromium oxidation resistance of the AWS A5.8 nickel braze family. It is used on turbine and nickel-alloy hardware where capillary fill in tight, long joints is the limiting factor; deposit density is 7.85 g/cm3 with a maximum service temperature of 950 C. Forms are atomized powder, binder paste, tape and sintered preform. The deposit is hard and boride-bearing, cannot be weld repaired, and rates about 30 C lower in service temperature than standard BNi-5. BNi-5a has a density of 7.85 g/cm³ (0.284 lb/in³), lighter than 95% of nickel alloy grades. It melts at 1,030°C (1,886 °F). The elastic modulus is 200 GPa (29 Msi).
What is BNi-5a used for?
- Turbine hardware brazing
- High-temperature nickel alloy assemblies
- Tight-clearance capillary joints
- Stainless steel vacuum-brazed assemblies
- Hot-section static components
- Heat exchanger and manifold joints
Limitations
- Difficult to machine — 5/100, worse than 99% of nickel alloy grades
- Difficult to weld — 10/100, worse than 94% of nickel alloy grades
- Hard to polish — 60/100, worse than 84% of nickel alloy grades
BNi-5a properties
Typical room-temperature values; bars are the position among nickel alloy grades.
Physical3
BNi-5a has a density of 7.85 g/cm³ (0.284 lb/in³), lighter than 95% of nickel alloy grades. It melts at 1,030°C (1,886 °F).
Mechanical6
The elastic modulus is 200 GPa (29 Msi).
Thermal6
BNi-5a is rated for continuous service to 950°C (1,742 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), better than 71% of nickel alloy grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
BNi-5a conducts electricity at 1.4 % IACS, worse than 65% of nickel alloy grades.
Chemical & Environmental2
Corrosion resistance is very good (70/100), worse than 77% of nickel alloy grades.
Sustainability3
Producing a kilogram of BNi-5a takes about 200 MJ of energy and emits 14 kg of CO₂ — more than 78% of nickel alloy grades. Typical recycled content is 10%.
Manufacturability5
BNi-5a's machinability is not recommended (5/100, worse than 99% of nickel alloy grades); weldability not recommended (10/100).
Common Calculations2
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-5a is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BNi-5a
Is BNi-5a easy to machine?
The solidified braze deposit is a hard boride/silicide-bearing alloy — remove only by grinding or EDM, never expect conventional turning or milling.
Can BNi-5a be welded?
Not a welding consumable; fusion welding over a BNi-5a joint causes hot cracking and boride liquation, so re-braze rather than weld repair.
Can BNi-5a be formed, bent or molded?
Supplied as atomized powder, binder paste, tape or sintered preform — no wrought forming; control joint gap to 0.025–0.075 mm for capillary flow.
BNi-5a 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 |
|---|---|---|
| Cr | 18.5 – 19.5 | 19 |
| Si | 7 – 7.5 | 7.25 |
| Bmelting-point depressant, diffuses into parent metal | 1 – 1.3 | 1.15 |
| C | ≤ 0.06 | |
| Fe | ≤ 0.5 | |
| P | ≤ 0.02 | |
| S | ≤ 0.02 | |
| Al | ≤ 0.05 | |
| Ti | ≤ 0.05 | |
| Zr | ≤ 0.05 | |
| Other (total) | ≤ 0.5 | |
| Ni | balance |
What surface finishes work on BNi-5a?
Braze in vacuum (10⁻⁴ mbar) or dry hydrogen at about 1120–1205 °C, hold briefly, then apply a diffusion cycle; fillets can be blended and passivated with the parent stainless steel.
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-5a in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N99651
- ISO
- B-Ni5a
How much does BNi-5a cost?
BNi-5a is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BNi-5a — frequently asked
What is BNi-5a used for?
BNi-5a is typically used for turbine hardware brazing, high-temperature nickel alloy assemblies, tight-clearance capillary joints, stainless steel vacuum-brazed assemblies, hot-section static components and heat exchanger and manifold joints. In short: improved flow versus BNi-5; high-chromium oxidation resistance; 950 C service limit.
Is BNi-5a easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 99% of nickel alloy grades). The solidified braze deposit is a hard boride/silicide-bearing alloy — remove only by grinding or EDM, never expect conventional turning or milling.
Can BNi-5a be welded?
Not readily — weldability is rated not recommended (10/100). Not a welding consumable; fusion welding over a BNi-5a joint causes hot cracking and boride liquation, so re-braze rather than weld repair.
What surface finishes work on BNi-5a?
Braze in vacuum (10⁻⁴ mbar) or dry hydrogen at about 1120–1205 °C, hold briefly, then apply a diffusion cycle; fillets can be blended and passivated with the parent stainless steel.
Can BNi-5a be formed, bent or molded?
Supplied as atomized powder, binder paste, tape or sintered preform — no wrought forming; control joint gap to 0.025–0.075 mm for capillary flow.
What is the maximum service temperature of BNi-5a?
BNi-5a is rated for continuous use to about 950°C (1,742 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BNi-5a cost?
BNi-5a is a high-cost nickel alloy ($$$$), 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 A5.8M/A5.8 Specification for Filler Metals for Brazing and Braze Welding — American Welding Society (2019)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering — ASM International (1993)
- Brazing Handbook, 5th ed. — American Welding Society (2007)
- Nickel-base brazing filler metal powder datasheets — Wall Colmonoy / Höganäs / Lucas-Milhaupt (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.