Compare Pressureless Sintered Silicon Carbide (SSiC) and Recrystallized Silicon Carbide (RSiC). Learn the differences in porosity, strength, thermal conductivity, creep resistance, corrosion resistance, and service life to select the right material for high-temperature applications.
When selecting silicon carbide materials for high-temperature industrial applications, engineers often compare two of the most widely used materials:
- Pressureless Sintered Silicon Carbide (SSiC)
- Recrystallized Silicon Carbide (RSiC)
Although both materials are based on silicon carbide (SiC), their performance can differ significantly under real operating conditions.
The most important difference is not temperature capability.
The real difference is porosity.
RSiC contains an open porous structure with apparent porosity up to 17%, while SSiC is nearly fully dense with almost zero open porosity.
This difference directly affects:
- Mechanical strength
- Corrosion resistance
- Thermal conductivity
- Creep resistance
- Service life
- Long-term structural reliability
For kiln furniture, lithium battery furnaces, chemical equipment, semiconductor processing systems, and other demanding industrial applications, understanding this difference is critical.
| Material | Open Porosity |
|---|---|
| SSiC | ≈0% |
| RSiC | ≤17% |
Although porosity may appear to be a simple structural characteristic, it often determines how a material performs under real operating conditions.
Open pores act as:
- Crack initiation sites
- Oxidation pathways
- Corrosion channels
- Stress concentrators
The higher the porosity, the greater the risk of degradation during long-term service.
RSiC consists of:
- Large SiC grains
- Open pore network
- Lightweight structure
Advantages include:
✔ Good thermal shock resistance
✔ Lower density
✔ Lightweight kiln furniture construction
✔ Cost-effective manufacturing for large components
SSiC consists of:
- Fine SiC grains
- Strong grain bonding
- Nearly fully dense structure
Advantages include:
- ✔ High mechanical strength
- ✔ Excellent corrosion resistance
- ✔ Superior wear resistance
- ✔ Outstanding dimensional stability
- ✔ Long service life
| Property | Unit | SSiC | RSiC |
| SiC Content | % | ≥98 Vol% | ≥99% |
| Density | g/cm³ | ≥3.06 | 2.65–2.75 |
| Open Porosity | % | ≈0 | ≤17 |
| Vickers Hardness | HV1 | 2350 | 1800–2000 |
| Rockwell Hardness | R45N | 93 | – |
| Flexural Strength (20°C) | MPa | 320–400 | 90–100 |
| Flexural Strength (High Temp) | MPa | 300–400 @1300°C | 100–110 @1200°C |
| Elastic Modulus | GPa | 410 | Lower |
| Thermal Expansion Coefficient | 10⁻⁶/K | 4.0 | 4.6 |
| Thermal Conductivity (20°C) | W/m·K | 196 | Lower |
| Thermal Conductivity (1200°C) | W/m·K | 60 | 35–36 |
| Thermal Shock Resistance | ΔT °C | >350 | Very Good |
| Max Service Temperature (Air) | °C | 1650 | 1650 |
One of the most significant differences between SSiC and RSiC is mechanical strength.
SSiC
- 320–400 MPa at room temperature
- 300–400 MPa at 1300°C
RSiC
- 90–100 MPa at room temperature
- 100–110 MPa at 1200°C
This means SSiC provides approximately:
than RSiC.
For applications such as:
- Silicon carbide rollers
- Long-span kiln beams
- Lithium battery furnace components
- Structural kiln furniture
this difference becomes extremely important.
Because RSiC contains open pores:
- Vapors can penetrate the structure
- Oxidation progresses more easily
- Corrosive species can reach deeper regions
Over time this may lead to:
- Surface degradation
- Strength reduction
- Structural weakening
Near-zero porosity significantly reduces:
- Chemical penetration
- Oxidation pathways
- Internal corrosion
As a result, SSiC performs exceptionally well in:
- Lithium battery material production
- Chemical processing systems
- Semiconductor equipment
- Corrosive furnace atmospheres
SSiC: 60 W/m·K
RSiC: 35–36 W/m·K
SSiC transfers heat significantly faster.
Benefits include:
- Reduced thermal gradients
- More uniform temperature distribution
- Lower thermal stress concentration
This contributes directly to improved reliability.
Due to its porous structure:
- Grain boundary sliding occurs more easily
- Stress concentrates around pores
- Long-term deformation increases
The dense structure provides:
- Strong grain bonding
- Elastic modulus of approximately 410 GPa
- Excellent dimensional stability
For continuous operation exceeding 1000 hours, SSiC generally maintains geometry much better than RSiC.
✔ Lightweight construction is important
✔ Thermal shock resistance is the primary requirement
✔ Mechanical loads are relatively low
Typical applications include:
- Setter plates
- Lightweight kiln furniture
- Burner nozzles
- Thermal cycling structures
✔ High mechanical loads exist
✔ Long-span structures are required
✔ Corrosive atmospheres are present
✔ Long service life is critical
Typical applications include:
- Silicon carbide rollers
- Silicon carbide beams
- Thermocouple protection tubes
- Lithium battery kiln furniture
- Chemical processing equipment
Explore our silicon carbide solutions:
- Pressureless Sintered SiC Roller Rods
- SSiC Beams
- SSiC Plates
- SSiC Saggers
- Thermocouple Protection Tubes
- RSiC Beams
- RSiC Rollers
- RSiC Setter Plates
- RSiC Kiln Furniture
Website:
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SSiC typically provides three to four times higher flexural strength than RSiC.
Both materials perform well.
RSiC is often selected for lightweight thermal cycling applications, while SSiC offers a larger safety margin due to its significantly higher strength.
For high-load, corrosive, or continuous-operation environments, SSiC generally provides a significantly longer service life.
The pressureless sintering process creates a nearly fully dense microstructure, resulting in higher strength, better corrosion resistance, superior wear resistance, and longer operational life.
Although both SSiC and RSiC are silicon carbide materials, their engineering performance differs significantly.
- Lightweight construction
- Good thermal shock resistance
- Cost-effective solutions for low-load applications
- Near-zero porosity
- Exceptional mechanical strength
- Superior corrosion resistance
- Outstanding creep resistance
- Longer operational lifetime
For demanding high-temperature applications requiring structural stability, reliability, corrosion resistance, and long service life, pressureless sintered silicon carbide (SSiC) is typically the preferred engineering choice.
Our engineering team can help evaluate:
- Operating temperature
- Mechanical load
- Thermal cycling conditions
- Expected service life
Contact us for material selection support:
Website: https://www.hitech-ceram.com/
Email: Scarlett.s@kegugroup.com
Shaanxi Kegu New Material Technology Co., Ltd.
Advanced Silicon Carbide Ceramic Solutions for High-Temperature Industries.
