Ceramic Bearings

Ceramic hybrid bearings are comprised of ceramic rolling elements (balls) enclosed in a ferrous (typically steel) inner and outer race. Since these bearings are constructed from many materials, they often operate in hybrid capacities. We also build ceramic bearings (i.e., bearings with ceramic races), but they are not as common because they are less durable.

We construct the rolling elements in ceramic bearings using several ceramic materials, including

• Silicon nitride (Si3N4)
• Aluminum oxide (Al2O3)
• Zirconium oxide (ZrO2)
• Silicon carbide (SiC)

Applications that involve high speeds and high loads often involve ceramic bearings. These bearings offer several benefits over conventional steel bearings, including enhanced acceleration capability, increased stiffness, and reduced friction. Hybrid ceramic bearings also offer the benefit of not allowing electrical currents to run through the bearing, which allows for prolonged use.

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Benefits of Ceramic Bearings

Manufacturers prize ceramic bearings because of their speed advantage over their steel counterparts. This benefit stems from their four main characteristics:

• Reduced rolling resistance
• Reduced weight
• Increased durability
• Increased stiffness

Reduced rolling resistance mainly results from the ceramic balls’ increased smoothness, dimensional stability, and increased uniformity over steel ball bearings. These properties ensure that applied loads are uniformly distributed over all rolling elements. Additionally, ceramic materials have a significantly lower coefficient of friction (~20–30 times less) than steel ball bearings with standard seals and lubrication. This reduced friction results in reduced rolling resistance and faster rotational speeds.

The reduced weight of ceramic bearings also contributes to their overall enhanced performance over steel bearings. Ceramic materials can weigh up to 40% less than comparable steel bearings. This reduced weight translates to decreased centrifugal loads exerted on the outer race as the bearing spins. This reduction of forces allows ceramic bearings to operate up to 20–40% faster than conventional steel bearings while using considerably less energy to maintain their speed.

Ceramic bearings are also harder than steel bearings and therefore are more durable. Studies show that ceramic bearings can last anywhere between 5 and 20 times longer. The smoother surface of the ceramics also significantly reduces the risk of bearing seizure with little to no lubrication. Furthermore, ceramic bearings can operate in harsh environments due to their resistance to corrosion and degradation. Finally, their electrical insulation properties eliminate the risk of electrical erosion and pitting of the rolling elements.

Ceramic Bearing Applications

Space-exploration applications and other aerospace industry products often rely on ceramic bearings. The lightweight and vacuum-compatible bearings make them ideal for satellites and spacecraft, which require optimal weight capacities to enhance flight dynamics and acceleration. Additionally, these bearings can operate without lubricants such as heavy greases and oils, which tend to attract contaminants that interfere with sensitive electrical components. There are many common applications that touch our daily life. Most Railroad Traction Motors are experiencing improved life from Ceramic materials. Chemical and mixing applications also benefit from the use of ceramic bearings, especially in terms of preventing contamination. Because ceramic bearings are chemically inert, they do not react with harsh chemicals or leach particulates into sensitive solutions. The corrosion-resistant property of ceramic bearings makes them ideal for washdowns with strong acidic or alkaline chemical cleaning solutions. Furthermore, the lack of oil- and grease-based lubrication reduces the chance of bacterial growth and contamination.

Some additional applications of ceramic bearings include:

High-speed mills
High-speed machining
Precision instruments
Pumps and compressors