INDIA Cerobear vFINAL DR 24/6/08 11:05 Page 34
Semiconductor India
Cerobear rolling bearings could already materials in the bearing even lead to a bearings can withstand all requirements of
demonstrate their outstanding characteristics greater number of shots with the same gas the aerospace industry, as well.
under various circumstances: Many filling.
manufacturers of coating plants have The operating of new components in rolling
already noticed the advantage of dry Another area where Cerobear rolling bearings contributes to massive
running hybrid or full ceramic bearings. For bearings are used in is the cleaning of developments in their areas of application.
example, rolling bearings have been used in wafers. Here, one takes advantage of the High performance ceramic groups play a
handling systems in vacuum application and extreme corrosion resistance of Si3N4 full vital role in this regard, although; only two
under high thermal stress. ceramic bearings. The cleaning medium is ceramics prove to be adequate material to
also used for the lubrication of the bearing be used in rolling bearings.
The lifetime of safety bearings for magnetic since the use of grease is not allowed in this
bearings, as used in turbomolecular pumps, application. Hot isostatic pressed silicon nitride is
could be 40 times increased. Safety especially applicable. Full ceramic bearings
bearings are exposed to extreme shock As mentioned above Cerbear bearings are consist of rings and balls made of Si
3
N
4
.
loads and accelerations. also used in other fields of application. The positive properties this ceramic include
Nearly every aseptic bottle filling machine extreme over rolling resistance, low density,
They need to be able to reach a rotational in the food industry worldwide is equipped very good corrosion resistance, high
speed of about 40.000 1/min within 100ms. with hybrid bearings. The chemical and bio hardness and stiffness, as well as good
For this application hybrid bearings do industry mainly takes advantage of the temperature and abrasion characteristics.
provide two advantages: First, light ceramic extreme corrosion resistance in agitators for These properties are the result of the mainly
balls can be accelerated faster than steel chemical processes. covalent bonding of the ceramic built up.
balls and second, the friction loss in rolling
contact is 20 to 30% lower. Bearings are even in direct contact to very After the development of series production
corrosive liquids. A great leap forward technology for manufacturing powder,
The bearing related down time of excimer could be done in the reachable speeds for Si
3
N
4
is the most frequently used ceramic
lasers in the production of semi conductors machine tool applications by using in rolling bearings today.
worldwide could be reduced to Cerobear bearings.
approximately 1/32 by applying full Typical Si
3
N
4
materials are alloyed with
ceramic bearings. The lower friction and weight of ceramic yttrium oxide (Y
2
O
3
) or magnesia oxide
allow characteristic speeds up to 3500000 (MgO). Due to the very small expansion co-
In this application, the bearings directly run mm/min. Another field of application is the efficient of Si
3
N
4
the fit calculation requires
in aggressive process gas. Ideal adapted drive of solar panels of satellites. Hybrid special attention. Information regarding
Material characteristics Si
3
N
4
ZrO
2
100 Cr 6
Density ρ g/cm
3
3,2 6,1 7,85
Heat expansion coefficient α 10
-6
/K 2,8 9,6 11,5
Elasticity modulus E GPa 320 200 210
Poisson number v 1 0,27 0,29 0,3
Hardness HV10 N/mm
2
1 600 1 200 700
Bending strenght σB N/mm
2
700 1 000 > 2 500
Fracture toughness KIc MPa m
1/2
710> 20
Temperature range boundary °C 1000 400 180
Heat conductivity Λ W/m • K 30…35 2 40…45
Spec. electrical resistance Ω • mm
2
/m 1,00E+19 1,00E+00
Tab 1: Material characteristics of Si3N4, ZrO2 and 100 Cr6
34 www.semiconductor-india.com | Summer 2008
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