ZrO2 or zirconium dioxide is a tough ceramic material with expansion properties very similar to steel. This is an advantage when considering shaft and housing suitability for high temperature applications. Zirconia bearings weigh approximately 70% of steel bearings. Zirconia bearings have high hardness, very smooth wear surfaces and can run without lubrication, so they are often used where very low rotational resistance is important. Their coefficient of friction is very low compared to steel bearings or even hybrid bearings. ZrO2 bearings have a coefficient of friction of approximately 0.0012 at ambient temperature and lightly loaded air.
The ZrO2 full ceramic ball bearings listed below are available with cages (or locators) made of PEEK, PTFE. Bearings with a bore diameter above 8mm can also be fitted with 316 stainless steel cages. Additionally, we stock full complement ZrO2 bearings in stock. These come without cages and extra balls. For full complement types, the rated load is approximately 20% higher, but the maximum speed can be reduced by up to 70%. As for bearing cages, PEEK is often the stock of choice due to its strength and durability. If an alternative cage material is required to handle specific chemicals or extreme temperatures beyond the range of PEEK, it can be manufactured to order. Metric ZrO2 bearings are not magnetic or conductive and are highly resistant to most chemicals. They are also extremely water resistant, which is why they are often used in marine applications, especially where the equipment is completely submerged or where 316 marine grade bearings cannot handle the load or speed. It is important to note that if the ZrO2 is in contact with steam or hot water for an extended period, there may be some weakening of the material over time.
Full complement ZrO2 metric bearings or bearings with 316 stainless steel cages can be used at temperatures up to 400°C. When the temperature is higher than the ambient temperature, the maximum speed should be reduced, especially if the bearings are not lubricated. Due to the lower maximum temperature of the cage material, bearings with PEEK cages are rated for temperatures up to 250°C. It may be preferable to use looser radial clearance at high temperatures, especially when the inner ring temperature may be higher than the outer ring temperature, as this will reduce the radial clearance of the bearing. Our ZrO2 metric bearings come standard with a looser C3 radial clearance.
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