What is a Silicon Nitride Plunger?
A silicon nitride plunger is a precision Si₃N₄ ceramic piston rod that reciprocates inside a pump head, passing through fixed packing or seals to pressurise or meter the working fluid. It is chosen when metal plungers develop wear tracks, corrosion marks or sealing drift under repeated strokes in high-pressure, metering, dosing or filling duty.
Silicon Nitride Plunger Specifications
| Silicon Nitride Plunger | |||
| Item No. | Diameter (mm) | Length (mm) | GPSN / HPSN / Custom Grade (%) |
| AT-SN-ZS001 | 2 | 20 | 85-99 |
| AT-SN-ZS002 | 2 | 50 | 85-99 |
| AT-SN-ZS003 | 3 | 50 | 85-99 |
| AT-SN-ZS004 | 4 | 50 | 85-99 |
| AT-SN-ZS005 | 5 | 50 | 85-99 |
| AT-SN-ZS006 | 6 | 60 | 85-99 |
| AT-SN-ZS007 | 6.75 | 50 | 85-99 |
| AT-SN-ZS008 | 7.5 | 100 | 85-99 |
| AT-SN-ZS009 | 8 | 30 | 85-99 |
| AT-SN-ZS010 | 10 | 40 | 85-99 |
| AT-SN-ZS011 | 12 | 10 | 85-99 |
| AT-SN-ZS012 | 12 | 40 | 85-99 |
| AT-SN-ZS013 | 15 | 10 | 85-99 |
| AT-SN-ZS014 | 15 | 40 | 85-99 |
| AT-SN-ZS015 | 20 | 80 | 85-99 |
| AT-SN-ZS016 | 20 | 40 | 85-99 |
| AT-SN-ZS017 | 25 | 50 | 85-99 |
| AT-SN-ZS018 | 30 | 80 | 85-99 |
| AT-SN-ZS019 | 2-80 | 20-200 | 85-99 |
Structural Silicon Nitride Material Reference
Use these values to compare Si₃N₄ against other materials early in your design. They come from standardized material tests, not from finished plungers in service — so actual allowable load, wear rate and seal behavior depend on your geometry, media and operating conditions.
| Property | Unit / Condition | AD-SIN-ST Typical Value |
|---|---|---|
| Bulk density | g/cm³, typical | 3.2 |
| Flexural strength | MPa, typical | 700 |
| Fracture toughness K<sub>IC</sub> | MPa·m½, method-dependent | 6.5 |
| Thermal conductivity | W/(m·K), typical | 20 |
| Apparent porosity | vol%, sintered body | <0.3 |
| Poisson’s ratio | dimensionless, typical | 0.25 |
| Rockwell hardness | HRA, typical | 92–94 |
Select the Contact Pair and Define the Fit
| Pairing under review | Specify together | Decision evidence |
|---|---|---|
| SiC or zirconia guide/bushing | Actual ceramic grades, bore/plunger tolerances, working length and surface | Fit assessment, medium compatibility and relevant contact-pair test or operating evidence |
| Metal guide/bushing | Alloy, bore geometry, alignment, temperature and lubrication/flushing | Cold and operating fit, surface acceptance and wear objective |
| PTFE / composite packing | Packing formulation, working diameter, preload and sealing travel | Packing supplier’s assembly requirements and leakage / wear acceptance |
| Elastomer seals | Compound, seal geometry, medium/cleaning chemistry and temperatures | Seal-system compatibility and assembly requirements |
Define Clearance and Seal Requirements Clearly
Specify whether the guide fit uses radial or diametral clearance. For both mating parts, provide the dimensions, tolerance limits and measurement temperature. Then check how operating temperatures, fluid conditions and lubrication affect the fit.
Define packing compression or preload separately, following the specification for the selected seal system.
If the piston carries a seal that moves with it, provide a piston-and-cylinder assembly drawing. Clearly show:
- Which part moves and its direction of motion
- Where the seal is located
- Which components are to be supplied
This helps ensure the quotation covers the intended parts.
Why Use Silicon Nitride for Pump Plungers?
| Engineering Need | How Si₃N₄ Helps | Buyer Note |
|---|---|---|
| Wear control under repeated strokes | High hardness and stiffness help reduce surface wear on the working band. | Final life depends on pressure, media, seal material and alignment. |
| Seal and packing stability | A ground or polished sealing surface helps maintain stable contact with PTFE, elastomer or composite packings. | Surface finish should be specified by working-zone requirements. |
| Corrosion resistance | Silicon nitride can be used with many water-based, salt and chemical media where metal plungers may corrode. | Media compatibility should be checked before quotation. |
| Dimensional stability | Low thermal expansion and high modulus help maintain plunger geometry during repeated motion. | Clearance must be reviewed with pump-head design. |
| Custom pump integration | Shoulders, threaded ends, flats and transition radii can be designed to match the drive and packing layout. | Drawings or worn samples are recommended for RFQ. |
Si3N4 ceramic plunger Packing
- Each silicon nitride plunger is individually wrapped in soft protective material to prevent contact damage and micro-chipping.
