Boron Nitride
also Hex Boron Nitride, White Graphite
Boron Nitride is a lamellar, graphite-like nitride ceramic supplied hot-pressed or pressed and sintered in grades such as GRADE-BO, GRADE-CA, HP-99, GRADE-XP and BN-SiO₂, plus CVD-grown PBN and high-pressure cBN.
Reference datasheet — Boron Nitride 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.
Values for the Pressed & Sintered condition
Boron Nitride tempers and conditions
Boron Nitride is supplied in 8 conditions, soft to hard. Pressed & Sintered is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
High-purity (>99 %) binder-free hot-pressed hBN | Choose for semiconductor, crystal-growth and vacuum-furnace parts where boron-oxide outgassing, moisture pickup or metal-ion contamination cannot be tolerated. | 25 | 60 W/m·K | |||
Grade XP | High-purity fine-grain hot-pressed hBN with low binder content — clean, low-outgassing and near-isotropic, for crucibles, insulators and semiconductor fixtures. | 30 | 40 W/m·K | |||
Pressed & SinteredDefault hot-pressed hBN with boric-oxide bond (Grade A type) | General-purpose machinable hBN block/rod for molten-metal contact, insulators and break rings; cheapest route, but the B2O3 bond is hygroscopic. | 35 | 33 W/m·K | |||
Grade BO | Hot-pressed hexagonal BN with boric-oxide (B₂O₃) bond — high strength and excellent machinability, but hygroscopic and limited to moderate air temperatures. | 35 | 27 W/m·K | |||
Grade CA | Calcium-borate bonded hot-pressed hBN — moisture-resistant version of bonded BN with higher strength and service to ~1000 °C in air. | 45 | 25 W/m·K | |||
BN-SiO₂ | Choose when strength, wear and non-hygroscopic behaviour matter more than maximum thermal conductivity — jigs, nozzles, high-humidity or load-bearing insulators. | 50 | 25 W/m·K | |||
Pyrolytic boron nitride | Choose for MBE effusion-cell crucibles, GaAs/InP growth boats and microwave-tube windows: pore-free, ultra-pure, no binder, usable to ~1800 °C in vacuum. | 100 | 60 W/m·K | |||
Cubic boron nitride, sintered polycrystalline | Choose only as a superhard cutting/wear material: second only to diamond in hardness and, unlike diamond, chemically stable against ferrous alloys up to ~1000 °C. | 4,000 HV | 200 W/m·K |
What is Boron Nitride?
Boron Nitride is a lamellar, graphite-like nitride ceramic supplied hot-pressed or pressed and sintered in grades such as GRADE-BO, GRADE-CA, HP-99, GRADE-XP and BN-SiO₂, plus CVD-grown PBN and high-pressure cBN. At 2.0 g/cm³ it is light, electrically insulating, lubricious and stable to 1000 °C with 33 W/m·K conductivity, and a machinability score of 85 lets shops cut finished crucibles, insulators and break rings straight from billet. Strength is very low (35 MPa tensile, 45 GPa modulus) and B₂O₃-bonded grades pick up moisture, so it is not a structural material; use silicon nitride or alumina where load or erosion matters. Boron Nitride has a density of 2 g/cm³ (0.0723 lb/in³), lighter than 88% of ceramic grades. It melts at 2,973°C (5,383 °F). Boron Nitride has a tensile strength of 35 MPa (5.08 ksi), weaker than 71% of ceramic grades. The elastic modulus is 45 GPa (6.53 Msi).
What is Boron Nitride used for?
- Crucibles for molten metal
- Electrical insulators and feedthroughs
- Break rings for horizontal continuous casting
- Mould release and setter plates
- Thermocouple protection sleeves
- Plasma chamber insulators
- Microwave tube windows in PBN
Advantages
- Easy to machine — 85/100, better than 91% of ceramic grades
- Lightweight — 2 g/cm³ (0.0723 lb/in³), better than 88% of ceramic grades
Limitations
- Hard to polish — 25/100, worse than 97% of ceramic grades
- Low stiffness — 45 GPa (6.53 Msi), worse than 85% of ceramic grades
- Low fracture toughness — 1 MPa·√m (0.91 ksi·√in), worse than 84% of ceramic grades
Boron Nitride properties
Typical room-temperature values for Boron Nitride-Pressed & Sintered; bars are the position among ceramic grades.
Physical4
Boron Nitride has a density of 2 g/cm³ (0.0723 lb/in³), lighter than 88% of ceramic grades. It melts at 2,973°C (5,383 °F).
Mechanical9
Boron Nitride has a tensile strength of 35 MPa (5.08 ksi), weaker than 71% of ceramic grades. The elastic modulus is 45 GPa (6.53 Msi).
Thermal5
Boron Nitride is rated for continuous service to 1,000°C (1,832 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), better than 64% of ceramic grades. Thermal expansion is 2 µm/m·K (1.11 µin/in·°F).
Electrical5
Boron Nitride is an electrical insulator with a dielectric strength of 40 kV/mm (1,016 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (70/100), worse than 59% of ceramic grades.
Sustainability4
Producing a kilogram of Boron Nitride takes about 250 MJ of energy and emits 20 kg of CO₂ — more than 67% of ceramic grades. Typical recycled content is 0%.
Manufacturability3
Boron Nitride's machinability is excellent (85/100, better than 91% of ceramic grades).
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 ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Boron Nitride is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Boron Nitride
Is Boron Nitride easy to machine?
Machines like hard chalk — turn, mill, drill and tap dry with sharp carbide or HSS tooling at high speed and low feed; use dust extraction and avoid water coolant on B2O3-bonded grades.
Can Boron Nitride be welded?
Not weldable; join by mechanical clamping, threaded/pinned assemblies, or high-temperature BN/alumina cements and metallized-then-brazed interfaces.
Can Boron Nitride be formed, bent or molded?
Made by uniaxial hot pressing or CIP + pressureless nitridation of hBN powder into billets, then finish machined; PBN is grown as free-standing CVD shells on graphite mandrels, cBN is HP/HIP-sintered at GPa pressures.
Boron Nitride 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 |
|---|---|---|
| Bstoichiometric BN | 42 – 44 | 43.6 |
| B2O3boric-oxide bond phase in pressed & sintered grades; <0.5 % in high-purity and PBN grades | 0 – 6 | 3 |
| SiO2only in BN-SiO2 composite grades (borosilicate/calcium-borate bond) | 0 – 40 | 0 |
| CaOoptional calcium-borate bond addition | 0 – 5 | 0 |
| Nstoichiometric BN | balance |
What surface finishes work on Boron Nitride?
No plating or anodizing; surfaces are lightly ground or lapped only, remain matte and can leave a lubricious film — bake parts at 200–500 °C in vacuum/inert before high-temperature or vacuum service to drive off absorbed moisture.
Equivalent designations
Standards and trade names that resolve to Boron Nitride in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- Hex Boron NitrideWhite Graphite
How much does Boron Nitride cost?
Boron Nitride is a high-cost ceramic ($$$$), pricier than about 98% 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.
Boron Nitride — frequently asked
What is Boron Nitride used for?
Boron Nitride is typically used for crucibles for molten metal, electrical insulators and feedthroughs, break rings for horizontal continuous casting, mould release and setter plates, thermocouple protection sleeves and plasma chamber insulators. In short: machinable thermal insulator.
What is the tensile strength of Boron Nitride?
Boron Nitride has a typical tensile strength of 35 MPa (5.08 ksi) — weaker than 71% of ceramic grades. Strength varies by condition: see the 8 listed tempers.
Is Boron Nitride easy to machine?
Yes — machinability is rated excellent (85/100, better than 91% of ceramic grades). Machines like hard chalk — turn, mill, drill and tap dry with sharp carbide or HSS tooling at high speed and low feed; use dust extraction and avoid water coolant on B2O3-bonded grades.
Can Boron Nitride be welded?
Not weldable; join by mechanical clamping, threaded/pinned assemblies, or high-temperature BN/alumina cements and metallized-then-brazed interfaces.
What surface finishes work on Boron Nitride?
No plating or anodizing; surfaces are lightly ground or lapped only, remain matte and can leave a lubricious film — bake parts at 200–500 °C in vacuum/inert before high-temperature or vacuum service to drive off absorbed moisture.
Can Boron Nitride be formed, bent or molded?
Made by uniaxial hot pressing or CIP + pressureless nitridation of hBN powder into billets, then finish machined; PBN is grown as free-standing CVD shells on graphite mandrels, cBN is HP/HIP-sintered at GPa pressures.
What is the maximum service temperature of Boron Nitride?
Boron Nitride is rated for continuous use to about 1,000°C (1,832 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Boron Nitride cost?
Boron Nitride is a high-cost ceramic ($$$$), pricier than about 98% 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
- ASM Engineered Materials Handbook, Vol. 4: Ceramics and Glasses — ASM International (1991)
- Combat Boron Nitride Solids — Grades A, AX05, M, HP — Momentive Performance Materials / Saint-Gobain (2021)
- Boron Nitride Machinable Ceramics and PBN Crucibles — Kennametal / CoorsTek / Shin-Etsu (2022)
- Boron nitride (hexagonal, pyrolytic, cubic) property records — MatWeb / Ceramic Industry Materials Handbook (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.