B4C RB
Grade
RB = reaction bonded (silicon infiltrated) boron carbide, 8–20 % free Si
Pick silicon-infiltrated near-net shapes for large-area armour panels at the lowest cost; the 8–20 % free silicon lowers hardness and usable service temperature.
Values for the RB condition
Other B4C tempers and conditions
B4C is listed in 3 conditions; see the grade overview at B4C.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RBThis page Reaction bonded (silicon infiltrated) boron carbide, 8–20 % free Si | Pick silicon-infiltrated near-net shapes for large-area armour panels at the lowest cost; the 8–20 % free silicon lowers hardness and usable service temperature. | — | — | — | 2,400 HV | 55 W/m·K |
Pressureless sintered B4C | Choose pressureless sintering with C/SiC aids for complex shapes and large parts below hot-pressing cost, accepting slightly higher porosity and marginally lower strength and hardness. | — | — | — | 2,800 HV | 30 W/m·K |
HPDefault Hot pressed (pressure sintered) B4C, >99 % TD | Default when density, hardness and ballistic performance must be highest: pressure sintered to >99 % of theoretical density for armour plate, blast nozzles and neutron-absorbing elements. | — | — | — | 3,000 HV | 35 W/m·K |
What is B4C RB?
B4C RB is B4C in the RB grade — pick silicon-infiltrated near-net shapes for large-area armour panels at the lowest cost; the 8–20 % free silicon lowers hardness and usable service temperature. B4C RB has a tensile strength of 300 MPa (43.5 ksi), stronger than 68% of ceramic grades. The elastic modulus is 380 GPa (55.1 Msi). B4C RB has a density of 2.55 g/cm³ (0.0921 lb/in³), lighter than 80% of ceramic grades. It melts at 2,450°C (4,442 °F). HP is the default condition FabDigit quotes; RB is available on request or by drawing note.
Advantages
- Lightweight — 2.55 g/cm³ (0.0921 lb/in³), better than 80% of ceramic grades
B4C RB properties
Typical room-temperature values for B4C RB; 13 are specific to this condition. Other listed values are B4C reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
B4C RB has a density of 2.55 g/cm³ (0.0921 lb/in³), lighter than 80% of ceramic grades. It melts at 2,450°C (4,442 °F).
Mechanical12
B4C RB has a tensile strength of 300 MPa (43.5 ksi), stronger than 68% of ceramic grades. The elastic modulus is 380 GPa (55.1 Msi).
Thermal5
B4C RB is rated for continuous service to 1,200°C (2,192 °F). It conducts heat at 55 W/m·K (31.8 BTU/hr·ft·°F), better than 70% of ceramic grades. Thermal expansion is 4.5 µm/m·K (2.5 µin/in·°F).
Electrical2
B4C RB has an electrical resistivity of 0.01 Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (78/100), better than 53% of ceramic grades.
Sustainability4
Producing a kilogram of B4C RB takes about 260 MJ of energy and emits 22 kg of CO₂ — more than 69% of ceramic grades. Typical recycled content is 0%.
Manufacturability3
B4C RB's machinability is not recommended (6/100, better than 61% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with B4C RB
Is B4C easy to machine?
After sintering only diamond grinding, ultrasonic machining or laser processing are effective; wire EDM can be used where conductivity is sufficient. Green machining before sintering is the most economical route to complex geometry.
Can B4C be welded?
Not fusion weldable; join to metals by active brazing (Ti-bearing Ag-Cu-Ti fillers), diffusion bonding, or mechanical/adhesive clamping. Watch for reaction with Fe and Ni at high temperature.
Can B4C be formed, bent or molded?
Shaped from powder by dry pressing or isostatic pressing plus pressureless sintering above 2200 °C, hot pressing at 2100 °C/30 MPa, or silicon-infiltrated reaction bonding. Complex shapes are best made by the RB route.
What surface finishes work on B4C?
Diamond lapping and polishing reach Ra < 0.05 µm. Armor parts are normally bonded to UHMWPE or aramid backing; electroplating and anodizing do not apply.
B4C 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 B4C is 78.3 wt% B; 10B abundance ~19.9% | 76 – 79.5 | 78.3 |
| free Cfree carbon | ≤ 1.5 | 0.6 |
| B2O3surface oxide | ≤ 0.5 | 0.2 |
| Fe | ≤ 0.3 | 0.1 |
| Sifree Si up to 8-20% in reaction-bonded grades | ≤ 0.3 | 0.1 |
| Ccombined carbon; free carbon usually <1.5% | ≥ 20 (balance) | — |
B4C RB — frequently asked
What is B4C RB used for?
B4C RB is typically used for body armor plates, sandblasting nozzles, neutron shielding and wear-resistant components. In short: hardest common structural ceramic; lowest-density armor ceramic; neutron-absorbing boron content.
What is the tensile strength of B4C RB?
B4C RB has a typical tensile strength of 300 MPa (43.5 ksi) — stronger than 68% of ceramic grades. Strength varies by condition: see the 3 listed tempers.
Is B4C RB easy to machine?
Not especially — machinability is rated not recommended (6/100, better than 61% of ceramic grades). After sintering only diamond grinding, ultrasonic machining or laser processing are effective; wire EDM can be used where conductivity is sufficient. Green machining before sintering is the most economical route to complex geometry.
Can B4C RB be welded?
Not fusion weldable; join to metals by active brazing (Ti-bearing Ag-Cu-Ti fillers), diffusion bonding, or mechanical/adhesive clamping. Watch for reaction with Fe and Ni at high temperature.
What surface finishes work on B4C RB?
Diamond lapping and polishing reach Ra < 0.05 µm. Armor parts are normally bonded to UHMWPE or aramid backing; electroplating and anodizing do not apply.
Can B4C RB be formed, bent or molded?
Shaped from powder by dry pressing or isostatic pressing plus pressureless sintering above 2200 °C, hot pressing at 2100 °C/30 MPa, or silicon-infiltrated reaction bonding. Complex shapes are best made by the RB route.
What is the maximum service temperature of B4C RB?
B4C RB is rated for continuous use to about 1,200°C (2,192 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C750 — Nuclear-Grade Boron Carbide Powder — ASTM International (2015)
- ASM Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- Boron Carbide (B4C) Technical Data — CoorsTek (2023)
- Hexoloy / Norbide boron carbide product data — Saint-Gobain Ceramics (2022)
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.