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Ceramic Ball Bearings

Use of Ceramic Materials in Ball Bearings

Today's engineers have many options available to them when faced with extreme, or demanding operating conditions. This includes the use of ceramic materials that have many benefits in a variety of applications. The most common use is producing the rolling elements- the balls, from a ceramic material with the inner and outer rings made from traditional, heat-treated, chrome or stainless steel. These bearings are commonly referred to as Hybrid Bearings. With improvements in manufacturing technology, Full Ceramic Bearings are also readily available. These bearings have both the inner and outer rings in addition to the rolling elements manufactured from ceramic material. While hybrid and full ceramic bearings demand a premium price, they are often the most economical solution when considering the cost of a failure and the total cost of ownership for the end-user. 

Hybrid Bearings

The most common configuration is with chrome or stainless steel rings, and ceramic balls. Nitrogen enhanced stainless steel ring material is also available.

The most common ceramic material for the balls is silicon nitrideSi3N4. Compared to traditional steel balls, this material has desirable properties for rolling bearings, such as,

  • lightweight (approximately 60% lighter than bearing steel)
  • high hardness - over 75 HRc
  • higher elastic modulus - stiffer
  • lower coefficient of thermal expansion
  • higher maximum operating temperature - 1000⁰C
  • highly polished surface finish resulting in lower friction

Balls made of zirconiaZrO2, are also available. This ceramic material has some properties similar to those of silicon nitride but differs in that it has some mechanical and thermal properties much closer to that of the alloy steel that the rings are made from. This can be desirable in maintaining the preload and contact angle over a broad range of operating temperatures.  

Characteristics Unit Chrome Steel Stainless Steel Nitrogen Enhanced Stainless Steel Si3N4 ZrO2
Density g/cm3 7,85 7,85 7,85 3,2 6,0
Hardness Rc >60 >58 >60 >75 >75
E-Modulus GPa 210 200 218 320 200
Poissons Coefficient   0,28 0,28 0,3 0,26 0,3
Expansion Coefficient x 10-6 °C 10,9 10,1 10,1 2,9 10
Top Temperature Limit °C 170 260 500 1000 600
Corrosion Resistance   limited good very good very good good
Electrical Conductivity   conductor conductor conductor isolator isolator
Magnetism   magnetic magnetic magnetic not magnetic not magnetic

An AST Applications Engineer should be consulted for a full analysis of the operating conditions and potential failure modes. 

Benefits of Hybrid Ceramic Bearings:

  • higher stiffness and rigidity reduces deflection
  • increased the limiting speed, RPM
  • less adhesive wear, there is no cold welding
  • better lubricant life
  • lower noise levels and vibration
  • no electrical arcing through the balls

Applications for Hybrid Ceramic Bearings:

  • machine tool spindles
  • pumps - submersible, fuel, vacuum
  • dental drills
  • optical scanners
  • electric motors
  • aerospace applications
  • laboratory equipment
  • applications that require higher speeds, longer life, and lower friction

Full Ceramic Bearings

Full Ceramic Bearings are often the answer for extreme environments, such as high temperatures, corrosive chemicals, steam, and hard vacuum. These bearings have both the inner and outer rings in addition to the rolling elements manufactured from ceramic material. Like the balls in hybrid bearings, the rings in full ceramic bearings are typically manufactured from silicon nitrideSi3N4 or zirconia, ZrO2. Retainers in full ceramic bearings are typically made from high-performance plastics such as PEEK or PTFE. Full complement versions are also available. 

Benefits of Full Ceramic Bearings:

  • resistant to acid, salt and water, and blood
  • non-magnetic
  • lower coefficient of friction
  • resistant to electricity
  • corrosion-resistant
  • lighter, smoother and stiffer

Applications for Full Ceramic Bearings:

  • MRI equipment
  • vacuum environments
  • semiconductor manufacturing
  • radiotherapy
  • food processing industries
  • any extreme environment requiring non-corrosive, non-conductive or non-magnetic bearings

An AST Applications Engineer should be consulted for a full analysis of the operating conditions and potential failure modes. 

AST Bearings is proudly presenting our new certificates for both the NJ and CA locations: AST Bearings’ ISO 9001:2015 Certificates

To learn more about what the ISO 9001 standard is, the differences between the 2015 and 2008 versions, and how AST verifies customer satisfaction: Learn About AST Bearings’ certification to ISO 9001:2015

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