Silicon Carbide Seal Rings: SSiC & RBSiC Supplier | MAC
Silicon Carbide Seal Rings: Sintered and Reaction-Bonded Grades to Your Drawing
We supply silicon carbide seal rings in sintered (SSiC) and reaction-bonded (RBSiC) grades to your drawing: US-based engineering, application support and quality assurance, with factory-direct global manufacturing.
We quote flat, stepped, rotating and stationary SiC seal rings to your drawing
A silicon carbide seal ring is the hard face in a mechanical seal — the rotating ring on the shaft, the stationary mating ring in the housing, or both. We quote them as flat, single-step, double-step and grooved rings from your dimensioned drawing, formed by pressing, injection moulding and high-temperature sintering, then finished by CNC diamond grinding of the fired ceramic.
Stepped geometries are specified where a balanced face or a retainer shoulder is required. Grooved faces appear where a lift feature is part of the seal design. Because the step and the sealing face are both produced after firing, their geometry follows the drawing rather than the tooling.
In practical terms, send the drawing and we quote against it. We do not hold a standard ring catalogue to substitute against.
Sintered SSiC and reaction-bonded RBSiC are not interchangeable seal face grades
Sintered silicon carbide (SSiC) contains no free silicon. Reaction-bonded silicon carbide (RBSiC, also SiSiC) retains metallic silicon — approximately 10% nominal per the CoorsTek silicon carbide brochure, and 10–30% in the CoorsTek safety data sheet 02107 for SC-2. That second phase changes chemical resistance and maximum service temperature far more than it changes hardness or thermal conductivity.
Property | Sintered SiC (SSiC) | Reaction-bonded SiC (RBSiC / SiSiC) |
Free silicon | ≈10% nominal — CoorsTek silicon carbide brochure; 10–30% — CoorsTek SDS 02107 (SC-2) | |
Density | 3.10 g/cm³ — Hexoloy SA TDS; 3.15 g/cm³ — CoorsTek UltraSiC; 3.15 g/cm³ — CeramTec ROCAR S1 | 3.10 g/cm³ — CoorsTek SC-RB; 3.07 g/cm³ — CeramTec ROCAR SiG/SiF |
Hardness | Knoop 2,800 kg/mm² at 0.1 kg load — Hexoloy SA TDS; Knoop 26 GPa at 100 g load — CoorsTek UltraSiC; Vickers HV0.5 2,300 — CeramTec ROCAR S1 | Knoop 24.5 GPa at 100 g load — CoorsTek SC-RB; two-phase, Vickers HV0.2 1,200 in the silicon phase and 2,700 in the SiC phase — CeramTec ROCAR SiG/SiF |
Flexural strength, room temperature | 380 MPa 4-point and 550 MPa 3-point — Hexoloy SA TDS; 480 MPa — CoorsTek UltraSiC; 410 MPa per DIN EN 843-1 — CeramTec ROCAR S1 | 462 MPa (MOR at 20 °C) — CoorsTek SC-RB; 340–350 MPa per DIN EN 843-1 — CeramTec ROCAR SiG/SiF |
Fracture toughness | 4.60 MPa·m½ — Hexoloy SA TDS; 3.5 MPa·m½ — CoorsTek UltraSiC; 4.1 MPa·m½ — CeramTec ROCAR S1 | 4.0 MPa·m½ — CoorsTek SC-RB; 4.0 MPa·m½ — CeramTec ROCAR SiG/SiF |
Thermal conductivity | 125.6 W/m·K at room temperature, falling to 102.6 W/m·K at 200 °C — Hexoloy SA TDS; 150 W/m·K at room temperature — CoorsTek UltraSiC; 115 W/m·K over 20–100 °C — CeramTec ROCAR S1 | 125 W/m·K at 20 °C — CoorsTek SC-RB; 115–120 W/m·K — CeramTec ROCAR SiG/SiF |
Coefficient of thermal expansion | 4.02 ×10⁻⁶/K over room temperature to 700 °C — Hexoloy SA TDS | 4.3 ×10⁻⁶/°C over 25–1,000 °C — CoorsTek SC-RB |
Maximum service temperature | 1,900 °C in air — Hexoloy SA TDS; 1,500 °C oxidising and 1,800 °C inert — CeramTec ROCAR S1 | 1,000 °C maximum use — CoorsTek SC-RB; 1,350 °C — CeramTec ROCAR SiG/SiF |
Figures are vendor typical values measured under different test methods, shown side by side rather than averaged. Expansion and conductivity are both reported against a stated temperature range, so read each with its range as well as its grade; the Hexoloy SA data sheet gives density as 3.10 g/cm³ where Saint-Gobain's web page for the same grade lists 3.15, and the data sheet value is the one cited here.
The two grades sit close on density, thermal conductivity and fracture toughness, which is why they are quoted against each other. They separate on temperature ceiling and on chemistry. AZoM also reports that reaction-bonded silicon carbide is more chip resistant than the sintered version, which matters on thin sections and sharp step edges.
Published ceilings for reaction-bonded grades do not agree: CoorsTek gives 1,000 °C for SC-RB, CeramTec 1,350 °C for ROCAR SiG and SiF. Treat the ceiling as grade-specific rather than as a property of reaction-bonded silicon carbide generally.
From an engineering perspective, specify the process route, not just "silicon carbide".
Free silicon makes reaction-bonded SiC the wrong grade for caustic and HF service
Free silicon is attacked by strong alkalis and by hydrofluoric acid. In Saint-Gobain's submersion testing, Hexoloy SA sintered silicon carbide lost 2.5 mg/cm² per year in 50% sodium hydroxide at 100 °C, while reaction-bonded silicon carbide at 12% silicon lost more than 1,000 mg/cm² per year in the same medium.
Medium and temperature | Sintered SiC — Hexoloy SA | Reaction-bonded SiC, 12% Si | Saint-Gobain weight-loss class |
50% NaOH at 100 °C | 2.5 mg/cm²·yr | >1,000 mg/cm²·yr | Completely destroyed within days |
45% KOH at 100 °C | <0.2 mg/cm²·yr | >1,000 mg/cm²·yr | Completely destroyed within days |
10% HF + 57% HNO₃ at 25 °C | <0.2 mg/cm²·yr | >1,000 mg/cm²·yr | Completely destroyed within days |
Both columns from the Hexoloy SA technical data sheet, Saint-Gobain. Test conditions: 125 to 300 hours of submersive testing, continuously stirred.
CeramTec states the chemical resistance of its reaction-bonded grades as limited up to pH 10. Materials-selection guidance in Pump Industry Magazine reaches the same conclusion: reaction-bonded silicon carbide should not be used with caustics, other high-pH chemicals, or strong acids. A John Crane tutorial by Brian Kalfrin and Jack Bagain, reported in Turbomachinery Magazine, adds the thermal limit — above 1,410 °C (2,570 °F) the free silicon melts and strength decays.
This is where second-sourcing on a drawing that says only "silicon carbide" fails. Both grades satisfy that callout, both will quote, and one of them is destroyed within days in 50% caustic. In practical terms: if your fluid runs above pH 10 or contains hydrofluoric acid, specify a sintered grade with no free silicon, and give us the concentration and temperature at RFQ so the quote names the grade rather than the family.
The mating face decides the grade as much as the fluid does
A silicon carbide ring is rarely specified alone. API 682, fourth edition, treats reaction-bonded and self-sintered silicon carbide equally as default face materials across Categories 1 to 3, and its default pairing runs one premium-grade, blister-resistant carbon-graphite ring against one silicon carbide ring.
Mating face | Basis | Source |
Carbon-graphite, premium blister-resistant grade | The standard's default pairing | API 682 4th edition / ISO 21049, via the EagleBurgmann application guide |
Silicon carbide, self-mated | Frequently used where slurry handling causes particle wear | US Patent 5,080,378 |
Tungsten carbide (cemented carbide) | Listed as a mating-ring material | US Patent 5,080,378, claim 7 |
Alumina | Listed as a mating-ring material | US Patent 5,080,378, claim 7 |
US Patent 5,080,378 states that silicon carbide sintered parts are increasingly combined with carbon parts or with other silicon carbide parts because they allow a higher PV limiting value, and that two silicon carbide sliding parts are frequently used where particle wear from slurry handling is the problem.
What does API 682 specify as default seal face materials?
Both reaction-bonded and self-sintered silicon carbide qualify as defaults under the fourth edition, so the standard does not choose between the two grades for you. The fluid and the mating face do.
When is graphite-loaded silicon carbide considered for dry running?
Graphite-loaded grades exist in the market — 3M Grades P and G, CeramTec ROCAR G5. The John Crane tutorial reported in Turbomachinery Magazine notes that free graphite reduces friction, improving dry-run survivability, in crude oil, finished products and light hydrocarbon service.
From an engineering perspective, name the mating face on the drawing; it changes the grade recommendation.
Alumina, zirconia and silicon nitride cover duty that silicon carbide does not
Silicon carbide is not the only ceramic specified for seal faces. We also quote alumina at 99.5% purity, yttria-stabilised zirconia and silicon nitride. Property data for each, with its own grades and sources, sits on the alumina material page, the zirconia material page, and our alumina, zirconia and silicon carbide comparison, rather than being restated here.
For procurement purposes, if your print allows an alternative ceramic, say so at RFQ and the quote can carry both options.
Manufacturing is factory-direct: Engineering, application support and quality assurance are US-based
Our model is US-based engineering, application support and quality assurance with factory-direct global manufacturing. Production runs through our affiliate, Shenzhen Microns Advanced Ceramics Technology Co., Ltd. Disclosed here because it bears on your landed cost, your documentation trail and your schedule.
Duties and surcharges change, so we quote landed cost at the time of RFQ rather than publishing a rate that will be out of date before you order.
For procurement purposes, send three things alongside the drawing: the documentation your specification requires, your required delivery date, and whether this is a qualification quantity or a production release. Each is confirmed against on the quote.
An SiC seal ring quote needs the duty data, not just the dimensions
A silicon carbide seal ring is quoted from duty data as well as dimensions, because the fluid, the temperature and the mating face decide which grade can be offered before any dimension is priced. Our RFQ form accepts STEP, STP, DWG and PDF files, so native CAD reaches engineering review directly.
Data we need | What it determines |
Dimensioned drawing and 3D model | Quotable geometry and grinding scope |
Ring role: stationary or rotating | Which face carries the drive and anti-rotation feature |
Geometry: flat, single-step, double-step, grooved | Forming route and post-firing operations |
Your acceptance criteria for the sealing face | What the quote must be inspected against |
Mating-face material | Grade recommendation and pairing check |
Process fluid, concentration and pH | Whether a free-silicon grade is permissible |
Operating temperature range | Grade ceiling selection |
Pressure and shaft speed, or PV | Duty severity and pairing |
Prototype and production quantities | Forming route economics |
Why are critical dimensions specified in the fired-and-ground condition?
Precision Ceramics notes that silicon carbide can be machined green, biscuit or fully dense, but that sintering shrinks the body by approximately 20%, which makes it impossible to hold very tight tolerances pre-sintering. Critical faces and diameters are therefore produced by grinding after firing. The Hexoloy SA data sheet also advises chamfering or radiusing all edges, so mark the edge treatment you need on the drawing.
In practical terms, an RFQ carrying fluid, temperature, pressure, speed and mating face is quotable on first pass.
Sourcing note. Every property figure above is reproduced from a named manufacturer data sheet or published standard, with its grade, test condition and source stated in the cell it appears in. Where vendors disagree, both figures are published with their sources rather than reconciled into one number.
Technical content reviewed by Mark Ma, Lead Materials Engineer, Microns Advanced Ceramics. Reviewed 2 October 2026.
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