Silicon Carbide and Hard Materials

Materials ·

Silicon carbide (SiC), alumina (Al2O3), tungsten carbide (WC), and other technical ceramics are used as pump shaft sleeves, seal faces, bearings, and impeller wear components where extreme hardness, corrosion immunity, and dimensional stability under abrasive or chemically aggressive conditions are required — environments that destroy metallic and polymeric alternatives within hours of operation.

History

Silicon carbide as an abrasive was first produced by Edward Goodrich Acheson in Monongahela City, Pennsylvania, USA in 1891 using the Acheson Process (electric furnace sintering of sand and coke), and he named it Carborundum. Reaction-bonded silicon carbide (RBSiC) for mechanical seal faces was developed by Norton Company and General Electric in the USA during the 1960s for high-temperature nuclear reactor pump applications. The first commercial SiC mechanical seal faces for industrial pumps were introduced by Burgmann (now EagleBurgmann) in Germany around 1970. Pressureless-sintered SiC (SSiC) with superior purity and chemical resistance was commercialized by Ceradyne and ESK in the 1980s for semiconductor and chemical pump applications.

Key Properties

  • Density: 3.1 g/cm3 (SSiC) — lighter than all metallic pump materials
  • Hardness: 2500 to 2800 HV — exceeds tungsten carbide (1500 to 1700 HV) and all metals
  • Flexural strength: 300 to 500 MPa
  • Thermal conductivity: 120 W/mK — better than most metals, excellent for mechanical seal faces
  • Coefficient of thermal expansion: 4.0 x 10-6 per K — very stable dimensions under temperature cycling
  • Zero porosity in sintered grade — no chemical absorption into the material body

Corrosion and Chemical Resistance

  • Essentially inert to all acids (including HF up to 49 percent), alkalis, and organic solvents at ambient temperature
  • Resistant to hydrofluoric acid at all concentrations — rare among hard engineering materials
  • Not attacked by seawater, oxidizing acids, or organic media at any concentration or temperature
  • Only attacked by: molten alkalis and strong base solutions above 180 degrees C, and by fluorine gas
  • Alumina (Al2O3): slightly less chemical resistance — attacked by HF and strong alkalis
  • Tungsten carbide (WC with Co binder): cobalt binder leaches in strong acids — specify Ni binder for acid service

Grades and Standards

  • SSiC (sintered SiC): ASTM C1494 — primary grade for seal faces and bearings
  • RBSiC (reaction-bonded): ASTM C1306 — shaft sleeves and impeller wear rings
  • Alumina Al2O3 (98 and 99.7 percent purity): ASTM C1499 — pump bearing bushings
  • Tungsten carbide (6 percent Co binder): ISO 9587 — pump shaft sleeves in abrasive slurry service
  • SEMI standard S2 governs SiC component purity for semiconductor process chemical contact

Applications

  • Mechanical seal faces in virtually all industrial pump types (paired SiC-SiC or SiC-carbon)
  • Shaft sleeves in slurry and abrasive liquid handling pump assemblies
  • Bearings and bushings in canned motor and magnetic drive pumps (zero leakage designs)
  • Impeller wear rings in high-wear slurry pump applications
  • Throat bushing in high-temperature high-pressure boiler feed pumps
  • Hydrofluoric acid and ultra-pure semiconductor chemical pump wetted-path components (SSiC)
  • Mining and dredge pump wear liners using tungsten carbide in elastomer matrix

Advantages

  • Highest hardness of any practical pump material — extreme abrasion resistance
  • Essentially universal chemical resistance to all industrial process fluids encountered in pump service
  • Excellent dimensional stability — no creep or deformation under sustained mechanical load
  • Very low friction coefficient when SiC-SiC seal faces operate in a lubricated condition
  • Long service life in abrasive slurry — often 10 times longer than 316L stainless impellers

Limitations

  • Brittle — susceptible to fracture from thermal shock or mechanical impact during installation
  • Very high cost for custom-machined pump components versus metallic alternatives
  • Cannot be welded or plastically deformed — machining requires diamond tooling throughout
  • Limited complex shape achievable — intricate pump casings not practical in ceramic materials
  • Tight tolerances require skilled grinding — longer manufacturing lead times than metal machining

Selection Criteria

  • Specify SSiC seal faces for all chemical pumps handling acids, alkalis, or solvents — the universal default for mechanical seals
  • Pair SiC rotating face with carbon stationary face to minimize friction and heat generation in the seal
  • Use RBSiC or tungsten carbide (6 percent Co binder) shaft sleeves in slurry pumps where abrasive wear is the primary failure mode
  • For HF acid service: SSiC is the only recommended hard seal face material — carbon and tungsten carbide are attacked by HF
  • Budget 4 to 8 week lead time for custom-profile SiC pump components from specialist ceramic manufacturers

Top 10 Manufacturers

  • 1. EagleBurgmann (Germany) — ~20% of SiC pump component market; SiC mechanical seal faces for all pump industries
  • 2. John Crane Inc. (USA) — ~18%; SiC seal face technology for chemical and oil/gas pump mechanical seals
  • 3. Flowserve Corporation (USA) — ~10%; SiC seal faces and shaft sleeves for ANSI and API process pumps
  • 4. Morgan Advanced Materials (UK) — ~8%; SSiC and Al2O3 pump bushings and seal faces for industrial use
  • 5. Ceratec Technical Ceramics (Netherlands) — ~6%; custom SSiC pump components for the chemical industry
  • 6. 3M Advanced Materials (USA) — ~5%; Hexoloy SiC pump seal faces and abrasion-resistant wear components
  • 7. Kyocera Corporation (Japan) — ~5%; precision SiC and Al2O3 pump bearing and seal face components
  • 8. CoorsTek Inc. (USA) — ~5%; technical ceramic pump shaft sleeves and impeller wear liners
  • 9. Kennametal Inc. (USA) — ~4%; tungsten carbide shaft sleeves for slurry and abrasive pump service
  • 10. Saint-Gobain Ceramics (France/USA) — ~4%; Silit SiC and Alundum Al2O3 pump wear components