Performance Comparison Between Recrystallized Silicon Carbide and Conventional Silicon Carbide

Silicon carbide (SiC) is a high-performance ceramic material widely used in applications involving high temperature, wear resistance, and chemical corrosion. As application scenarios continue to diversify, SiC materials have evolved into various types, including Reaction-Bonded SiC (RB-SiC), Self-Sintered SiC (SSiC), Hot-Pressed SiC (HP-SiC), and Recrystallized Silicon Carbide (RSiC). Among these, RSiC exhibits unique physical and chemical characteristics due to its distinctive microstructure and sintering process that excludes sintering additives. This article provides a detailed comparison between RSiC and conventional SiC across several aspects—composition, structure, processing, performance, and applications—to help engineers and materials scientists select the most appropriate SiC material for their needs.

1. Composition and Structural Differences

2. a) Raw Material Composition

RSiC typically uses high-purity SiC powders (≥98%) and is sintered without any additives, preserving material purity.

Conventional SiC materials (e.g., RB-SiC or SSiC) require the addition of oxide-based sintering aids such as alumina, yttria, or boron oxide to lower sintering temperatures and promote densification.

1. b) Microstructure

RSiC features large SiC grains (tens to hundreds of microns) connected via neck growth during recrystallization. The resulting structure is open-pored and exhibits relatively low density (about 75–85%).

Conventional SiC is more densely sintered (≥95% density) with fine, evenly distributed grains, low porosity, and narrow pore distribution, offering higher mechanical strength.

2. Manufacturing Process Comparison

Item	Recrystallized SiC (RSiC)	Conventional SiC (RB-SiC, SSiC)
Sintering Temperature	1950–2200°C	1650–2100°C (depending on additives)
Sintering Atmosphere	Vacuum, inert, or reducing	Vacuum, inert, or reactive gases
Sintering Mechanism	Grain surface recrystallization	Liquid-phase or solid-state sintering via additives
Sintering Duration	Long (6–20 hours)	Moderate
Cost	High	Relatively lower

3. Physical and Chemical Property Comparison

Property	RSiC	Conventional SiC (RB/SSiC)
Thermal Shock Resistance	Excellent (>100 heat-cool cycles)	Moderate to good (40–80 cycles)
Thermal Conductivity (W/m·K)	25–35	10–20
Porosity (%)	15–25 (open)	<5 (mostly closed)
Oxidation Resistance	Excellent (stable SiO₂ film)	Excellent (depends on additives)
Corrosion Resistance	Exceptional (chemically inert)	Good (some additive leaching)
Flexural Strength (MPa)	60–90	250–400
Maximum Operating Temperature	Up to 1800°C	1600–1750°C

Summary: While RSiC has slightly lower mechanical strength, it excels in thermal shock resistance, high-temperature capability, corrosion resistance, and thermal conductivity. This makes it ideal for extreme thermal environments. On the other hand, conventional SiC is more suitable for applications requiring high mechanical loads or tight dimensional tolerances.

4. Typical Application Scenarios

Application	RSiC	Conventional SiC (RB/SSiC)
Kiln Furniture	✔ Long lifespan, thermal shock resistant	✔ Moderate durability
High-Temp Heat Exchanger Tubes	✔ High thermal conductivity	❌ Susceptible to thermal fatigue
Chemical Reactor Linings	✔ Excellent corrosion resistance	✔ Moderate resistance
Mechanical Seal Rings	❌ Insufficient strength	✔ High hardness and density
Nozzles and Blast Pipes	❌ Prone to wear	✔ High impact resistance

Clearly, RSiC is better suited for thermally dynamic and chemically aggressive high-temperature environments, such as radiant tubes, support plates, and furnace tubes. Conventional SiC is ideal for mechanically demanding parts, such as nozzles, bushings, and precision sealing components.

5. Material Selection Guidelines

Consider the following factors when selecting between RSiC and conventional SiC:

Operating Temperature: Choose RSiC for continuous use above 1600°C.

Thermal Cycling: For frequent heating/cooling conditions, RSiC is preferred.

Mechanical Load: For high-load or impact-prone parts, go with dense RB/SSiC.

Corrosive Atmospheres: For aggressive chemical environments, RSiC offers better reliability.

Cost vs. Lifecycle: RSiC may cost more initially, but provides better durability and long-term economic value.

6. Conclusion

Recrystallized SiC and conventional SiC each have their strengths and are not mutually exclusive. Understanding their structural and performance differences allows for informed material selection, improving efficiency, safety, and overall system reliability. Looking ahead, as high-temperature equipment trends toward more extreme and precise conditions, RSiC will continue to expand its role. Meanwhile, conventional SiC remains crucial for applications demanding high strength and dimensional accuracy.

Read our related blog – The Economic Impact Of Long-Lifespan Saggars On Lithium Battery Production. For regular updates, follow us on LinkedIn.