SKF - Rolling Bearings

Designs and variants
• Reduced risk of smearing between silicon
nitride and steel surfaces
Even under inadequate lubrication conditions,
there is reduced risk of smearing
between silicon nitride and steel surfaces.
This en ables hybrid bearings to operate
much longer in applications where there are
high speeds and fast accelerations, or applications
where there is an insufficient hydrodynamic
film to support undisturbed bearing
operation (i.e. k < 1, † Selecting bearing
size, page 61). For conditions where k < 1, it
is common to apply k = 1 for hybrid bearings
for bearing life calculations. Hybrid bearings
may perform well when lubricated with
ultra-thin film forming media, such as
refrigerants, typically used in compressor
applications or fuel pumps, enabling oil-free
designs.
• Runs faster, lasts longer
Combine the lower density of silicon nitride
with its lower coefficient of friction, high
hardness and the fact that silicon nitride
does not smear the raceways under poor
lubrication conditions, and the result is a
bearing that runs faster and longer even
under the most difficult operating
conditions.
• Low coefficient of thermal expansion
A silicon nitride rolling element has a lower
coefficient of thermal expansion than a
same-sized rolling element made of bearing
steel. This means less sensitivity to temperature
gradients within the bearing and more
accurate preload/clearance control.
When designing bearing arrangements
for very low temperatures, a hybrid bearing
with greater internal clearance than standard
may need to be selected. In these cases,
contact the SKF application engineering
service.
• Speed capability
Typically, hybrid bearings have a higher
speed cap ability than same-sized bearings
with steel rolling elements, however, in
some cases, the cage execution may limit
the attainable speed.
15F
1221