Huahao Sealing · Carbon Graphite Components
Carbon graphite is self-lubricating and grease-free; metal alloy seals require external lubrication. This article compares friction coefficient, wear life, temperature and corrosion resistance, and maintenance cost to guide pump and compressor material selection.
Metal alloys (bronze, babbitt, Stellite) have long served as pump and compressor bearing/seal materials, but they depend on external lubrication; once the lubricant film breaks down at high temperature, adhesive wear and seizure follow. Carbon graphite layered structure provides self-lubrication, running stably even under dry friction, with chemical inertness against corrosion. This comparison quantifies the operating envelope across 8 parameters.
| Property | Carbon Graphite Seal | Metal Alloy Seal |
|---|---|---|
| Self-lubricating (grease-free) | ✓ | ✗ |
| Dry friction coefficient | 0.04–0.08 | 0.20–0.40 |
| Max temperature (unlubricated) | 500°C | 150°C |
| Acid/alkali corrosion resistance (pH 0–14) | ✓ | ✗ |
| Wear on shaft | 极低（保护轴） | 高（需淬火轴） |
| Relative life (dry/semi-dry service) | ×3–6 | ×1.0 |
| Impact resistance / load capacity | ◐ (中) | ✓ (高) |
| Maintenance requirement | 免维护 | 定期补脂/换油 |
In dry, semi-dry, high-temperature, or corrosive service (high-temp ovens, molten salt pumps, chemical reactors, food machinery, seawater pumps), carbon graphite seals last 3–6× longer than metal alloys and are maintenance-free, while protecting the shaft journal from wear. Only in high-impact, heavy-load applications with guaranteed continuous lubrication (hydraulic cylinder bushings, low-speed heavy-duty journal bearings) do metal alloys remain irreplaceable thanks to their load and impact capacity.
Carbon graphite has a layered hexagonal crystal structure with weak interlayer bonding (van der Waals forces). Under shear, layers slide easily and transfer to form a lubricating film, giving a dry friction coefficient of just 0.04–0.08 without any grease.
In high-impact, heavy-load, low-speed applications with guaranteed continuous lubrication (e.g. hydraulic cylinder bushings, rolling-mill bearings). Metal alloys have higher impact and load capacity; carbon graphite may fracture under heavy impact.
No — it protects the shaft. Carbon graphite is softer than the metal shaft, so wear occurs preferentially on the graphite (sacrificial wear part), leaving the shaft journal virtually unworn. Only the graphite ring needs replacement to restore precision.
Under dry or semi-dry friction, carbon graphite typically lasts 3–6× longer than metal alloys, because metal alloys suffer adhesive wear and seizure when starved of lubricant, while carbon graphite maintains stable self-lubrication.
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