In industrial fields that require extremely high hardness, high temperature resistance, and corrosion resistance, silicon carbide (SiC) has become the preferred material for mechanical seals, kiln furniture, and wear-resistant components. However, not all silicon carbide is the same. Silicon carbide mainly comes in two forms: Sintered Silicon Carbide (SSiC) and Reaction Bonded Silicon Carbide (RBSC or RBSiC). Although they look similar, they differ significantly in manufacturing process, performance, and application areas. For buyers who purchase ceramic materials in bulk, understanding these differences is essential.
Sintered Silicon Carbide (SSiC) is a high-purity, high-strength ceramic that is very suitable for corrosive and high-temperature environments. Reaction Bonded Silicon Carbide (RBSC) is lower in cost and easier to shape, but its heat and chemical resistance are weaker. The correct choice depends on your performance needs, design complexity, and budget constraints.
With a basic understanding of both, let’s now take a closer look at the differences between the two in terms of composition, manufacturing process, physical properties, and typical applications.
What’s the difference between Reaction Bonded Silicon Carbide and Sintered Silicon Carbide?
The main difference between SSiC and RBSC lies in how they are made, which directly affects their chemical composition, mechanical properties, thermal behavior, and cost structure.
Manufacturing Process
Sintered Silicon Carbide (SSiC) uses high-purity SiC powder, which is directly bonded at high temperatures (usually >2000°C) through pressureless sintering or hot pressing, without the need to add binders or silicon. The entire material is a pure silicon carbide structure (>99% SiC), with high density, low impurities, and a more uniform and stable structure.
Reaction Bonded Silicon Carbide (RBSiC) is produced by mixing carbon powder with silicon carbide powder, and then introducing molten silicon in a vacuum or inert atmosphere for reaction sintering. The molten silicon reacts with carbon to generate new silicon carbide, thereby bonding the entire structure together. This method uses a relatively lower temperature (around 1450–1650°C), has good formability, but leaves a small amount of unreacted free silicon.
Material Composition
SSiC composition:
- Silicon Carbide (SiC): ≥99%
- Sintering aids: trace amounts of B (boron), C (carbon), Al₂O₃ or Y₂O₃ (<1%)
- No free silicon, no binders, no residual carbon
RBSC composition:
- Silicon Carbide (SiC): about 85–90%
- Free Silicon (Si): about 5–10%
- Residual Carbon (C): small amount (0.1–1%)
- Impurity elements: Fe, Al, Ca, O in trace amounts (generally <0.5%)
Mechanical and Thermal Properties
| Property | SSiC (Sintered) | RBSC (Reaction Bonded) |
| SiC content | >99% | 85–94% |
| Max operating temperature | ~1650°C | About 1350–1400°C |
| Density | ~3.1 g/cm³ | ~3.0 g/cm³ |
| Flexural strength | >400 MPa | 250–300 MPa |
| Hardness (Vickers) | ~2500 | ~1800 |
| Thermal shock resistance | Moderate | Excellent |
| Corrosion resistance | Excellent | Moderate |
| Machinability | Poor (requires diamond tools) | Good (can achieve net shaping) |
| Cost | Higher | Lower |
Advantages of SSiC and RBSiC
Although both are forms of silicon carbide, due to differences in structure and bonding, they differ significantly in application suitability.
SSiC advantages:
High purity and high density: SSiC contains ≥99% silicon carbide, no free silicon or binding phase, and grains are bonded through covalent bonds, resulting in an extremely dense structure (density 3.15 g/cm³). This purity ensures excellent chemical stability and mechanical strength.
High temperature resistance: SSiC can operate stably for long periods in environments above 1600°C without failure due to melting of free silicon.
Excellent corrosion resistance: Since it does not contain free silicon, SSiC exhibits extremely high chemical inertness in strong acids, strong alkalis, and oxidative environments, especially in media like HCl, H₂SO₄, NaOH, HNO₃, where it is hardly corroded.
Extremely high hardness and wear resistance: With a Mohs hardness of up to 9.5, second only to diamond. Suitable for mechanical seal rings, valve seats, nozzles, agitator sleeves, and other high-wear components.
Excellent oxidation resistance and dimensional stability: SSiC forms a dense and stable oxide film that prevents further oxidation; it has a low thermal expansion coefficient (4.0×10⁻⁶/K), suitable for high-precision mechanical or optical applications.
High insulation and compatibility with high-purity environments: In the electronics and semiconductor industries, SSiC is used as structural components or support bases, with extremely low ionic contamination, ensuring compatibility with vacuum and cleanroom environments.
RBSiC advantages:
Good formability, can manufacture complex structures: RBSiC uses liquid silicon infiltration reaction technology and can manufacture large-size, thin-walled, or complex geometrical components, such as rollers, kiln furniture, linings, etc. Its shaping freedom is a distinct advantage that SSiC cannot achieve.
Lower cost, high cost-effectiveness: With lower manufacturing temperatures (1450–1650°C) and controllable processes, production costs are about 20–40% lower than SSiC, making it very suitable for mass industrial applications.
Good thermal conductivity: Due to the presence of free silicon phase, it has high thermal conductivity (120–150 W/m·K) and good thermal shock performance, suitable for high-temperature furnaces, heat exchange equipment, kiln support structures, etc.
Excellent mechanical strength and thermal shock resistance: Although its strength is slightly lower than SSiC, RBSiC can still maintain stability in thermal cycling and mechanical impact environments and is not prone to cracking.
In summary: When your application involves chemicals, pressure, high temperature, or wear, choose SSiC. When cost, complex shapes, or thermal shock are priority concerns, choose RBSC.
What are the different types of silicon carbide?
In industrial applications, silicon carbide (SiC) is mainly divided into three commercial grades based on differences in manufacturing process and performance: Sintered Silicon Carbide (SSiC), Reaction Bonded Silicon Carbide (RBSC or RBSiC), and Recrystallized Silicon Carbide (RSiC). Each type has obvious differences in purity, density, mechanical performance, and applicable scenarios.
Sintered Silicon Carbide (SSiC)
In the production process of Sintered Silicon Carbide, no binders are added. It usually uses high-purity SiC powder, densified directly through pressureless sintering at temperatures above 2100°C. It is characterized by high purity, dense structure, no free silicon, and high mechanical strength, corrosion resistance, and chemical stability.
Widely used in chemical processing equipment, semiconductor manufacturing, mechanical seal rings, high-end pump components, and precision valves that require high purity and high corrosion resistance.
Reaction Bonded Silicon Carbide (RBSC)
RBSC is formed by mixing carbon and SiC powder, then infiltrating with molten silicon. During the sintering process, a reaction forms new SiC, with free silicon as the bonding phase. Its main characteristics include:
- Good formability, can produce complex shapes
- Lower cost, high cost-effectiveness
- High strength and hardness, but contains a certain amount of free silicon (Si)
Widely used in refractory materials, kiln furniture, mechanical parts, pump and valve linings, nozzles, and rollers in industrial areas that require a balance between cost and strength.
Recrystallized Silicon Carbide (RSiC)
Made by sintering SiC particles at extremely high temperatures (~2500°C), allowing them to recrystallize and bond without using any binders. It is porous and lightweight, commonly used for kiln furniture and structural supports.
Which industries use Sintered and Reaction Bonded Silicon Carbide?
| Industry | Common Applications of SSiC | Common Applications of RBSC |
| Chemical | Seal rings, impellers, restrictors | Combustion tubes, gas diffusers |
| Metallurgy | Nozzles, armor plates, wear plates | Kiln furnace supports, beam systems |
| Power & Energy | High-wear pump bodies, valves | Heat exchangers, flue linings |
| Semiconductors | Wafer carriers, processing systems | Fixture components |
| Ceramics & Glass | Abrasive injectors, linings | Burner components, kiln furniture |
When selecting, the team should determine: operating temperature, corrosion exposure, need for complex design, expected wear cycle.
Where can you buy silicon carbide materials in bulk?
At Hengxin, we offer sintered and reaction bonded silicon carbide products—suitable for industrial applications.
Why buy from Hengxin?
- Factory-direct pricing: No middlemen
- Delivery time: Thanks to our 3,000 m² in-house factory
- Large inventory: A variety of shapes and sizes, ready to ship
- Support services: Custom dimensions and technical guidance available
Email: kesen@hxnewmaterial.com
Contact us now to request technical specifications, minimum order quantity, or samples.
