Ceramic rings and seal rings serve as wearing seats, seal faces, spacers and bearing races. Most are simple in outline and extremely demanding on the two flat faces.
Silicon carbide rings are the premium seal face for abrasive and high-temperature duty. Silicon carbide running against silicon carbide is a standard pairing in severe-service seals, because it resists both the abrasive wear and the thermal distortion that opens a seal face.
Silicon carbide is chosen when a part must survive abrasion, high temperature and thermal shock at the same time. Hardness reaches 2200-2500 HV, thermal conductivity of 120-200 W/m·K is several times that of steel, and expansion of 4.0 ×10⁻⁶/K keeps it in shape through fast temperature swings.
It is brittle and electrically semiconducting, so it is not used where electrical isolation matters, and its hardness makes diamond grinding the only practical finishing route.
Specifications
| Outer diameter | 5-200 mm |
| Inner diameter | 3-180 mm |
| Height | 2-40 mm |
| Wall thickness | 1-20 mm |
| Face flatness | 0.005 mm |
| Parallelism | 0.01 mm |
| Seal face finish | Ra 0.05-0.1 µm lapped |
Silicon Carbide Properties
| Composition | Sintered silicon carbide (SSiC) |
| Density | 3.10-3.15 g/cm³ |
| Vickers hardness | 2200-2500 HV |
| Flexural strength | 400-500 MPa |
| Fracture toughness | 3-4 MPa·m½ |
| Max. service temperature | 1400°C in air (1600°C inert) |
| Thermal conductivity | 120-200 W/m·K |
| Thermal expansion (20-1000°C) | 4.0 ×10⁻⁶/K |
Machining and Tolerances
Rings are cut from pressed or extruded tube stock or pressed individually, then both faces are ground and lapped together so they stay parallel. Seal faces are lapped to Ra 0.05-0.1 µm, and we inspect flatness under monochromatic light rather than with a dial indicator.
Where It Is Used
- Mechanical seal faces and mating rings in pumps and mixers
- Wear rings and throttling discs in valve trim
- Insulating spacers in high-voltage stacks
- Bearing races for corrosive or high-temperature service
- Precision spacers and shims in optical and metrology assemblies
Frequently Asked Questions
How flat can a seal face be made?
Lapped seal faces are held to 0.005 mm flatness or better, verified under monochromatic light. Below about 0.3 light bands the result depends more on the lapping method than on the material.
Do you supply matched seal pairs?
Yes. A rotating ring and its stationary seat are lapped as a pair so the two faces are matched, which shortens run-in and reduces the risk of initial leakage.