Smaller, Faster, Hotter:
Optimisation of Bearings
for Challenging Applications
Adding new design features or applying
making it more robust and resistant to oil-
extend lubricant life, sometimes up to five
special techniques and coatings to
off events. In the case of lubricant failure/
times longer than conventional steel ball
bearing components can optimise the
starvation, the silver-plating acts like a
bearings.
performance of bearings for challenging
solid, dry lubricant, allowing the bearing to
applications, providing unique bearing
continue running for a short period of time
Examples of applications for ceramic
solutions to clients’ problems, says Nick
or in an emergency situation. Application
hybrid bearings include high-speed
Dowding, Business Development Manager
examples include aerospace starter
vacuum pumps, medical/surgical hand
at The Barden Corporation (UK) Ltd.
generator bearings and bearings for air
tools and aerospace fans and generators.
conditioning units on trains.
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Adding value and improving bearing
performance by incorporating new
design features such as special
flanges, shafts and housings.
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Materials
Ceramic hybrid bearings
In materials technology, the most
For high-speed applications, replacing the
appropriate bearing materials can
steel balls with ceramic (silicon nitride)
be selected to maximise bearing
Optimising bearing performance by
balls can radically improve bearing
performance. Special ring materials
replacing traditional bearing materials
performance in several ways. First, because
are used successfully in aerospace and
with s pecial materials for high speed,
ceramic balls are much lighter than steel
non-aerospace applications, combining
high temperature or harsh operating
balls, reducing centrifugal forces and
superior corrosion and wear resistance
environments.
improving dynamic conditions whilst their
with the ability to withstand higher
The use of surface coatings such as
surface finish is almost perfectly smooth,
dynamic loads than conventional bearing
sub-micron sputtered coatings to
they exhibit vibration levels two to seven
steels. When used in conjunction with
further optimise bearing performance
times lower than conventional steel
ceramic balls, significant gains in bearing
and to make bearing behaviour
ball bearings. At higher speeds, internal
life and performance can be achieved.
more predictable/consistent in harsh
loading in the bearing is also reduced.
environments.
Secondly, ceramic hybrid bearings also
There are many different design features
run at significantly lower operating
and techniques that can be applied to
temperatures, which in conjunction with
a bearing to optimise and improve its
the lower mass allows running speeds to
performance in order to meet particularly
increase by as much as 40-50%. Lower
challenging (i.e. high speed, high
operating temperatures and reduced
temperature, harsh operating conditions)
heat build up inside the bearing helps
applications. These techniques include
applied coatings, altering the geometry of
a specific bearing component or replacing
conventional bearing materials with high
performance alternatives.
Ring materials can be optimised
for specific applications. The four
predominant ring materials used
by Barden are AISI 440C (corrosionresistant steel), SAE 52100, AISI
M50 and Cronidur 30®. For high
temperature applications (up
to 345°C) AISI M50 tool steel or a
special tempered version of
Cronidur 30® are suitable and are
widely used in high temperature
aerospace accessory applications
such as bleed valve systems on
aircraft.
Silver-plating of metal cages
In some high speed, high temperature
applications, steel cages can be coated
with silver to improve lubrication
performance and reliability. Silver plating
improves the lubricity of the bearing,
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PECM Issue 21
Cronidur 30® is a martensitic throughhardened, high nitrogen, corrosionresistant steel that can also be induction
case hardened. This material enhances
corrosion-resistance and improves the
fatigue life and wear resistance.