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When it comes to choosing bearing materials, designers and manufacturers have a variety of options at their disposal. Two popular materials used for high-performance bearings are ceramic and steel. Here, we will compare the advantages and disadvantages of ceramic bearing and steel bearings, high lighting their differences in terms of material properties, performance, and applications.
The composition of ceramic bearings is a bit more complex than steel bearings. While steel bearings are made of pure steel, ceramic bearings are made of a combination of ceramic materials, typically consisting of silicon nitride, zirconia, or alumina. Compared to steel bearings, ceramic bearings have a number of advantages:
| Item | Unit | Si3N4 | ZrO2 | Al2O3 (99.5%) | SiC | Bearing Steel |
| Density | g/cm3 | 3.23 | 6.05 | 3.92 | 3.12 | 7.85 |
| Coefficient of Friction | MPa•m1/2 | 0.0010 | 0.0012 | |||
| Water Absorption | % | 0 | 0 | 0 | 0 | 0 |
| Coefficient of Linear Thermal Expansion | 10-6/k | 3.2 | 10.5 | 8.5 | 3 | 12.5 |
| Modulus of Elasticity (Young’s Mod.) | GPA | 300 | 210 | 340 | 440 | 208 |
| Poisson’s Ratio | / | 0.26 | 0.3 | 0.22 | 0.17 | 0.3 |
| Hardness (Hv) | MPa | 1500 | 1200 | 1650 | 2800 | 700 |
| Flexural Strength (@ R.T.) | MPa | 720 | 950 | 310 | 390 | 520 (tensile strength) |
| Flexural Strength (700°) | MPa | 450 | 210 | 230 | 380 | / |
| Compressive Strength (@R.T.) | MPa | 2300 | 2000 | 1800 | 1800 | / |
| Fracture Toughness, Kb | MPa*m1/2 | 6.2 | 10 | 4.2 | 3.9 | 25 |
| Thermal Conductivity (@R.T.) | W/m*k | 25 | 2 | 26 | 120 | 40 |
| Electrical Resistivity (@R.T.) | Ω*mm2/m | >1013 | >1015 | >1016 | >103 | 0.1~1 |
| Max. Use Temperature (no loading) | °F | 1050 | 750 | 1500 | 1700 | 300 |
| Corrosion Resistance | / | Excellent | Excellent | Excellent | Excellent | Poor |
When it comes to performance, ceramic bearings typically outperform their steel counterparts in several key areas:
However, when it comes to load capacity, steel bearings generally outperform ceramic bearings due to their higher elasticity and ductility. This means that steel bearings can bear heavier loads without experiencing plastic deformation.
The choice between ceramic and steel bearings ultimately depends on the specific application and its requirements. Ceramic bearings are typically used in high-performance applications where high speeds, extreme temperatures, and corrosion resistance are critical. Some typical use cases for ceramic bearings include:
On the other hand, steel bearings are generally more versatile and can be used in a wide range of applications. Some typical use cases for steel bearings include:
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