Rolling elements
The use of hybrid bearings is becoming increasingly important in the field of rolling bearings. In a hybrid bearing, the inner and outer ring are still made of steel, but ceramic materials such as Si3N4 are used as rolling elements.
The ceramic rolling elements ensure a significant
reduction in weight, which allows
higher speeds
and
lower temperatures.
This also protects the lubricant, which thus has a longer service life. This results in
up to ten times longer service life of a hybrid bearing compared to comparable conventional steel bearings, since these bearings can continue to run even if the lubrication is insufficient.
Another advantage of hybrid bearings is the high corrosion resistance of the rolling elements, which is why these bearings can also be used with aggressive media.
However, the use of the hybrid bearings available so far is limited to those applications where the advantages of the ceramic rolling elements used are indispensable, since hybrid bearings are associated with significantly higher costs compared to steel bearings. Further problems of today's ceramics are, on the one hand, the strongly differing coefficient of thermal expansion of the Si3N4 rolling elements (3.5 ppm/K) compared to steel rings (11.5 ppm/K), when the bearings have to function in different temperature ranges, and, on the other hand, the high modulus of elasticity of the ceramic rolling element, whereby only a small contact ellipse can form and the surface pressure is increased.
Ceramic rolling elements made of Metal-like Ceramic (MLC) now offer completely new possibilities here. By optimizing the material for use with steel, it is ideally suited for use in hybrid bearings. MLC offers a coefficient of thermal expansion adapted to steel, which means that the bearings operate reliably over a wide temperature range. In addition, rolling elements made of MLC offer a significantly lower modulus of elasticity than Si3N4 ceramics, resulting in a larger contact ellipse and thus reducing the surface pressure, which relieves the steel components of the bearing. In addition, the innovative manufacturing process makes these rolling elements significantly more cost-effective to produce than conventional ceramic rolling elements. This means that the great advantages of hybrid bearings can even be used at a significantly reduced price.