Recrystallized Silicon Carbide (RSiC / RSC) — for Kiln Furniture, Burner Nozzles & High-Temperature Structural Parts

If your furnace cycle runs above 1450°C, involves rapid heating/cooling, and a sintering aid or free-silicon phase would become the weak link — this is the material page you should read before you specify. RSiC is not “another SiC grade.” It is the grade you choose when thermal shock resistance and chemical purity matter more than maximum density.

The one distinction that changes every downstream decision

Most supplier pages list RSiC density, porosity, and strength, and stop there. That information is necessary but not sufficient. The decision-relevant question is: why would anyone deliberately choose a silicon carbide with 10–20% open porosity over a dense SSiC that looks better on a data sheet?

The answer is in the microstructure. RSiC is produced by sintering high-purity SiC powder at roughly 2200–2450°C without sintering additives. Silicon carbide grains grow through an evaporation–condensation mechanism, forming direct neck bonds between grains. The material shrinks very little during firing, and the space that dense SiC would fill with sintering aids or free silicon remains as connected, open porosity. That porosity is not a manufacturing defect. It is the functional feature that gives RSiC its thermal shock tolerance and chemical inertness.

This is the judgment criterion that separates a buyer who understands SiC grades from one who is comparing only the density column.

RSiC vs. SSiC vs. SiSiC/RBSiC: the selection table most suppliers do not put on their product page

Selection rule: match the grade to temperature, atmosphere, chemical contact, and thermal cycle — not to the abbreviation “SiC.” If the application requires a dense, low-porosity surface for sealing or wear, RSiC is the wrong choice. If the application involves repeated rapid heating and cooling above 1450°C, and a free-silicon or sintering-aid phase would become the failure origin, RSiC is often the only SiC grade that survives.

Technical specifications — the numbers that matter for specification and incoming inspection

The table below reflects the property range you should use as a benchmark when evaluating any RSiC supplier’s data sheet. Values vary by grain size, forming route, and firing profile; a supplier quoting a single number without a range should be asked for the test standard and sample geometry.

Data sources integrated from supplier data sheets; ranges reflect normal commercial variation, not a guarantee for every geometry.

Where RSiC is the correct specification — and where it is the wrong one

Specify RSiC when the failure mode is thermal shock or chemical attack at temperature

Kiln furniture for fast-firing cycles. Thin setter plates, beams, and rollers that see repeated rapid heating and cooling above 1450°C. The low shrinkage during RSiC sintering allows thin-walled sections without warping, and the open porosity accommodates thermal strain that would crack a denser body.

Burner nozzles and radiant tubes. RSiC burner nozzles are specified in shuttle, tunnel, and roller kilns because they resist oxidation and thermal cycling up to ~1650–1700°C without the cracking that occurs in reaction-bonded SiC when free silicon becomes the weak phase.

Semiconductor and photovoltaic furnace components. High-purity RSiC is used for LPCVD paddles, boats, and diffusion furnace internals where metallic contamination and particle generation must be controlled. The absence of sintering aids is the specification driver here, not density.

Component protection tubes in atmosphere furnaces. The connected porosity of RSiC does not compromise chemical inertness in most furnace atmospheres, and the material tolerates the thermal gradients across the tube wall without spalling.

Do not specify RSiC when the requirement is density, sealing, or maximum strength

If the part must hold a vacuum seal, provide a lapped wear surface, or carry a structural load where SSiC’s higher density and strength are the governing properties, RSiC is the wrong grade. Similarly, if the part is large, geometrically complex, and cost-sensitive below ~1400°C, SiSiC/RBSiC is usually the more appropriate choice — its free silicon fills the porosity and enables near-net-shape manufacturing, at the cost of high-temperature and chemical limits.

Answers to the questions buyers actually ask before sending an RFQ

Is RSiC the same as SSiC? No. SSiC is pressureless-sintered with sintering aids and is dense. RSiC is recrystallized without additives and retains open porosity by design. They are different materials with different property trade-offs, not synonyms.

Can RSiC be used above 1650°C in air? The practical continuous limit in air is approximately 1600–1650°C. Some suppliers cite higher numbers for short-term or inert-atmosphere service; ask for the atmosphere and duration behind any higher claim.

Does the porosity mean the part is weaker or lower quality? It means the material is trade-off-optimized for thermal shock and purity, not for maximum strength. If your application does not require those properties, a denser grade may serve you better. Porosity is a specification variable, not a defect label.

What is the difference between RSiC and SiSiC/RBSiC in chemical service? SiSiC/RBSiC contains free silicon, which restricts long-term use above ~1400°C and reduces resistance to strong alkali and hydrofluoric-acid-containing environments. RSiC has no free silicon and no glassy grain-boundary phase, which is why it is preferred when chemical inertness at temperature is a requirement.

Can RSiC parts be supplied as custom geometries, not only standard plates and tubes? Yes, within the geometric constraints of the recrystallization process. RSiC is well suited to thin-walled, large-footprint shapes such as setter plates and beams, but extremely thick sections or complex internal cavities may be more economically produced in a reaction-bonded grade. Share a drawing and the operating conditions for a manufacturability assessment.