Ceramic plungers and pistons reciprocate inside a bore, displacing fluid or transmitting motion. They are used where steel would score, corrode or wear the bore out.
Silicon carbide plungers are used in severe-service pumps handling abrasive or high-temperature fluids. The 2200-2500 HV surface resists scoring by hard particles, and the conductivity carries frictional heat away from the 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
| Diameter | 5-80 mm |
| Length | up to 400 mm |
| Cylindricity | 0.005 mm |
| Diameter tolerance | ±0.005 mm ground |
| Surface finish | Ra 0.4 µm ground, Ra 0.2 µm polished |
| Straightness | 0.02 mm per 100 mm |
| End form | flat, domed, grooved or threaded |
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
Plungers are centreless ground then lapped to size and finish. Surface finish matters more than the number suggests: a plunger polished to Ra 0.2 µm will outlast one at Ra 0.4 µm by a wide margin because it stops abrading the seal.
Where It Is Used
- High-pressure pump plungers in water jetting and dosing
- Metering pump pistons in chemical and pharmaceutical dosing
- Valve and dispensing pistons in filling equipment
- Pump components in HPLC and analytical instruments
- Wear pistons for slurry and abrasive fluid service
Frequently Asked Questions
What finish do you recommend for a seal running face?
Ra 0.2 µm polished, and smoother where the seal material allows it. Seals fail from abrasion long before the ceramic itself wears, so the best value in a plunger is usually the finish rather than the grade.
Can the plunger be joined to a metal drive?
Yes, and it is worth designing carefully. We recommend a compliant interface or a bonded joint that does not load the ceramic in tension, since ceramic carries compression far better than tension or bending.