Industrial applications in challenging environmental conditions call for special bearing solutions. Bearing manufacturer NKE Austria GmbH has developed hybrid bearings for precisely these applications.
NKE hybrid bearings consist of ultrapure steel bearing rings and ceramic rolling elements made of bearing grade silicon nitride Si3N4 . The silicon nitride rolling elements are 60 percent lighter than those made from steel and are suitable for very high rotating speeds. Consequently, NKE hybrid bearings can reach limit speeds that are over 20 percent higher than conventional standard bearings. Even at these very high and demanding speeds, NKE hybrid bearings demonstrate excellent performance characteristics and minimal running noise. There are therefore particularly well suited for use in high-speed electric motors.
The ceramic rolling elements have high wear resistance and can achieve better results under extremely demanding conditions, such as poor lubrication, thereby extending service life significantly. The very good ‘dry-running properties’ of a hybrid bearing play an extremely critical part in substantially enhancing the reliability of an application.
The tribological properties of a hybrid bearing are very good due to the special material pairing of ceramic and bearing steel. Very little frictional heat is generated, even at high speeds.
In addition, the service life of the bearing is extended by the use of ultrapure bearing steel. The rolling elements are corrosion-resistant and have very high rigidity. The raceway and roller geometry of the hybrid bearings have been specially optimised to guarantee perfect contact geometry and high load capacity.
Typical applications for hybrid bearings include electric motors (AC/DC), wind turbine generators, high speed applications or traction motors for railway vehicles. Hybrid bearings with ceramic rolling elements are primarily designed for applications in which maximum electrical isolation is required and/or high speeds are involved. Hybrid bearings offer maximum isolation protection because the ceramic rolling elements themselves have an electrically insulating effect and thus prevent a corresponding passage of current. The use of frequency inverters often causes electrical damage to the bearing. With lower currents, a bearing with an electrically insulating coating among other measures can help to alleviate this. But only a hybrid bearing offers optimum protection against very high currents.
Depending on the demands of the application and the size of the bearing, the cages for the hybrid bearings are available in steel sheet, brass or polyamide; customised cage designs are also possible at the customer’s request. Frequently used hybrid bearing types include deep groove hybrid ball bearings, which are available from stock or with short lead times. Other bearing types or special designs can be manufactured to customer specifications upon request.