FOR EXTREME SPECIAL ENVIRONMENTS

CERAMIC BEARINGS

Japan Quality

CAT. NO. B1013E-A

Ceramic Bearing Development Story
Introduction to Application Examples
1 Machine tools
2 Film manufacturing equipment
3 Power generation equipment
4 Industrial furnaces
5 Production equipment
6 Semiconductor manufacturing equipment
7 Motor, Industrial machinery
8 Medical equipment
9 Home electrical appliances
10 Outer space, Leisure
11 Automobiles, Motorcycles

World’s first successful practical application of ceramic bearings“Aren’t there any bearings that can be used in seawater?”…One of our customers asked this question,
triggering our efforts to develop the ceramic bearing.
Initially, we attempted to use alumina as the raw material,
but it split quickly and cracks developed…
Following this, research stalled and ended after approximately five years.
Research resumed again in 1978;
this time with the development team consisting of five members.

Cooperation

3
3,4
4
5,6
7,8
9,10,11
12
13
13,14
14
15,16

Features
Properties of ceramic materials

Additionally, a material manufacturer known for

1
2
3
4

leading ceramics research was invited to join the effort.
Starting with silicon nitride as the raw material,
strength was reinforced using a sintering additive andMaterial characteristics
Rolling fatigue of ceramic materials
Ceramic materials suitable for rolling bearings
Composition of ceramic bearings

17
18
19
19

a hot pressing process eliminated cracking.

Production Process

As a result, the first ceramic bearings were commercialized in 1984.
Some of our customers had doubts about strength in the beginning,

Ceramics Production Process

stating “If ceramic cracks, it will surely split in two!”

1 Production Process

At that time, customers would hit the bearings with a hammer to test their strength.

20

Product Details

Doing this, the concrete below the bearing was the only thing that cracked!

Ceramic Bearing Product Details

Finding practical applications was initially difficult,but their strength and high-speed performance were gradually recognized, and

Good!

1
2
3
4

ceramic bearings began to be utilized for the main spindles of machine tools.
Next, they began receiving attention from semiconductor manufacturers owing to the

Rolling fatigue life of ceramic bearings
Static load rating of ceramic bearings
Impact strength of ceramic bearings
Fitting of ceramic bearings

21
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23
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characteristics of not using oil and not producing waste.

Performance

Ceramic bearings were then utilized in a section of experimental equipment on thespace shuttle Colombia, expanding their range of applications.

Ceramic Bearing Capacities

As productivity improved, ceramic bearings began being used in themass production of computer HDDs and automobile engines.

1
2
3
4

Koyo

Their excellent performance has been recognized andapplications have received various awards, such as the Japan Fine Ceramics Award.

Corrosion resistanceNon-magnetic performance
Insulation
High-speed performance

25,26
26
27
28

Product Introduction

And now…

1 Ceramic balls“For ceramic bearings, the answer is JTEKT”
1

2

29

Introduction to Application Examples

1

CERAMIC BEARINGS

Machine tools
CERAMIC BEARINGS

1

Spindle (Angular Contact Ball Bearing)

Product : Hybrid Ceramic Bearings

Machine tool spindle bearings are required to have superior rotational performance at extremely high speeds, quick
acceleration/ deceleration, high rigidity, and reduced temperature rises.
Hybrid Ceramic Bearings, which satisfy these requirements, are widely used in this application.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque2

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Product: Hybrid Ceramic Bearings (with special features)

A photographic film production line treats film surfaces by applying a high voltage.
Hybrid Ceramic Bearings are widely used in such environments, because the ceramic inner ring and balls serve as insulators.

● 20% to 30% reduction in temperature rise
● Upper limit of rotational speed range is
1.2-1.5 times higher(compared to Koyo steel bearings)● Insulation under high voltage environments

Use Conditions

High voltage

Use Conditions

Rotational speed: 25 000 min（d m n ＝ 2.75 × 106）
Lubrication: Oil or Grease
Spindle power: 75 kW

Rotational speed: 200 min
Temperature: Room temp.
Lubrication: Grease−1

2

Photographic Film
Manufaturing Equipment−1

Spindle (Cylindrical Roller Bearing)

Product : Hybrid Ceramic Bearings

Seizure resistance performance under unbalanced load conditions due to misalignment improved at the Vertical Spindle
Machining Center.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque3

Power generation equipment
CERAMIC BEARINGS

1● 20% to 30% reduction in temperature rise
● Upper limit of rotational speed range is
1.2-1.5 times higher(compared to Koyo steel bearings)

Wind Turbine Generator

Product: Hybrid Ceramic Bearings

Wind Turbine Generator are strongly required to operate for extensive periods of time without the need of maintenance.
However, bearings used in generators are subject to electrical pitting, which may cause the bearings to break down.
Hybrid Ceramic Bearings, which have superior durability and reliability, are widely used in such aerogenerators.

Use Conditions

Rotational speed: 12 000 min−1
Lubrication: Grease● Prevention of electrical pitting● Extension of grease service life
(three times longer than Koyo steel bearings)
Use Conditions

2

Rotational speed: 2700 min−1
Temperature: Below freezing point toapprox. 60°C
Lubrication: Grease

Film manufacturing equipment
CERAMIC BEARINGS

1

Liquid Crystal Polarizing Film
Manufacturing Equipment

Product : Corrosion Resistant Hybrid Ceramic Bearings

Liquid crystal polarizing film manufacturing equipment use acid solution, alkaline solution, dying solution, distilled water,and other solutions.
In such corrosive environments, Corrosion Resistant Hybrid Ceramic Bearings are widely used.

● Corrosion resistance to solutions such as acidsolution, alkaline solution, dying solution,and distilled water

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque2

Micro Gas Turbine Generator

Product: Hybrid Ceramic Bearings

The world's smallest gas turbine generators emit clean exhaust emissions and hence are friendly to the environment.
Hybrid Ceramic Bearings are used in these generators because they are low in vibration and noise generation, and haveexcellent high speed performance.

● Improved reliability in high speed rotation

TurbineBall bearings
Film coil

Generator rotor

Film rewinding coil

Generator stator

Use Conditions

Use Conditions

Rotational speed: 80 min−1
Temperature: Room temp. to 80°C
Lubrication: Chemical solution

Chemical solution

3

Rotational speed: 10 000 min−1（d m n ＝ 2.22 × 106）
Temperature: 200°C
Lubrication: Oil

Ball bearing
Ball bearing

4

Introduction to Application Examples

4

CERAMIC BEARINGS

Industrial furnaces
CERAMIC BEARINGS

1

Liquid Crystal Panel Bonding and
LC Sealing Furnace

Product : Hybrid Ceramic Linear Motion Ball Bearings

Substrate bonding press jigs for use in furnaces must be low in particle emissions and have a long service life under hightemperature conditions.
The Clean Pro Hybrid Ceramic Linear Motion Ball Bearings are widely used for such jigs.

● Suitable for clean environments thanks
to low particle emissions

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque4

Tube Annealing Furnace Guide Rolls

Product: Hybrid Ceramic Bearings

The guide roll bearings installed inside tube annealing furnaces are used under high temperatures without lubrication.
Hybrid Ceramic Bearings are suitable for such applications.

● Compatible with high temperature environments

Liquid crystal panel press jig

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Guide roller (ceramic)

Bearing
Use Conditions

Use Conditions

Stroke speed: 5 mm/s
Temperature: 200°C
Ambient pressure: Normal pressure
Lubrication: Clean pro coating

2

Furnaces Cars

Rotational speed: 300 min−1
Temperature: 300°C
Linear motionball bearings

Liquid crystal panel

Product: High Temperature Hybrid Ceramic Bearings

The bogies, conveyers and other carrier systems used in furnaces are exposed to high temperatures.
Because of their high heat resistance, High Temperature Hybrid Ceramic Bearings are used in such applications.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueDiffusion Furnace Dolly

Product: Full-complement Ceramic Ball Bearings

Conditions in a diffusion furnace are harsh, including not only high temperature, but also corrosive gas.
Incorporating a rolling mechanism for the conveyor dolly in the furnace enables smooth conveyance to be obtained, thereby
leading to improvements in product quality and productivity.

● Compatible with high-temperature environments● Corrosion-resistant against corrosive gases● Contributes to improved productivity● Applicable to high temperature environments

Use Conditions

Use Conditions

Rotational speed: 10 to 500 min
Temperature: 500°C
Lubrication: Graphite

Temperature: 800°C or higher
Ambient pressure: Corrosive gas atmosphere
Load: 5N

−1

3

5Baking Furnace Cars

Product: High Temperature Hybrid Ceramic Bearings

In the kiln that bakes fluorine resin onto the heat rollers of copying machines, conveyor bearings must be low in particle
emissions under high temperatures. Because it is structurally difficult to mount bearings accurately, High temperature Hybrid
Ceramic Bearings are used for this application, along with aligning rings.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Compatible with high temperature environments

Use Conditions

Rotational speed: 3 to 10 min−1
Temperature: 400 to 500°C
Lubrication: Graphite

56

Introduction to Application Examples

5

CERAMIC BEARINGS

Production equipment
CERAMIC BEARINGS

1

Aluminum Electrolytic Capacitor
Manufacturing Equipment

Product: High Corrosion Resistant Ceramic Bearings

In an aluminum foil electrolytic capacitor manufacturing equipment, a strong acid solution is used to treat the aluminum foils.
High Corrosion Resistant Ceramic Bearings are widely used in such highly corrosive environments.

● Corrosion resistance to strong acid solution

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

RollerAluminum foil

Chemical solution(Hydrochloric acidor sulfuric acid)

Use Conditions

Rotational speed: 50 min−1
Temperature: 90°C
Lubrication: Chemical solution(hydrochloric acid and sulfuric acid)2

Synthetic Fiber
Manufacturing Equipment

4

Steel Wire Stranding Machine

Product: Hybrid Ceramic Bearings

Steel wires for radial tires are produced by stranding steel wires to attain the required strength. In steel wire stranding
machines, which involve high speed rotation, Hybrid Ceramic Bearings are used for improved service life and stability.

● Reduced temperature rises● Reliable durability

Acid solution, alkaline solution, water, and other liquids are used in synthetic fiber yarn reinforcing processes. Corrosion
Resistant Hybrid Ceramic Bearings are applied in such corrosive environments.

● Corrosion resistance under acid solution,
alkaline solution and water

Clean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Ball bearings

Ball bearings

Use Conditions

Rotational speed: 6 000 min−1 or higher
Lubrication: Grease

SpindleSpindleWire stranding section

RollerProduct: Corrosion Resistant Hybrid Ceramic Bearings

VacuumVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque5

Jet Electrostatic Coating Machine

Product: Hybrid Ceramic Bearings

In a jet electrostatic coating machine, grease may escape from the spray nozzle due to the air motor, affecting the quality ofthe paint to be coated.
To resolve this problem, Hybrid Ceramic Bearings that do not use grease are used.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Prevention of grease scattering● Prevention of paint contamination

Yarn

Use Conditions

Electrostatic
coating spraynozzleUse Conditions

Rotational speed: 20 to 100 min
Temperature: Room temp. to 90°C
Lubrication: Chemical solution−1

Rotational speed: 20 000 min−1
Lubrication: Fluorine polyme

Chemicalsolution

Bell-like structure view

Roller3

DVD Sputtering Equipment

Product: Hybrid Ceramic Bearings

To improve reliability further, Hybrid Ceramic Bearings are used.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque6

Blister Packaging Equipment

Product: High-temperature Hybrid Ceramic Bearings

As heater roll bearings used in processing reach high temperatures during operation, conventional bearings are quickly
damaged.
Incorporating high-temperature ceramic bearings extends the bearing replacement cycle and improves productivity.

● Applicable to high-temperature environments● Contributes to improved productivity● Insulation

Use Conditions

Temperature: 250°C
Load: 900N
Lubrication: Grease

7

Clean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Heater roll

Use Conditions

Rotational speed: 300 min−1
Temperature: Room temp.
Lubrication: Grease

Vacuum8

Introduction to Application Examples

CERAMIC BEARINGS

6 Semiconductor manufacturing equipment
CERAMIC BEARINGS

Transfer Robot for Semiconductorand LCD Manufacturing Equipment Product: K Series Full-Complement Hybrid Ceramic Ball Bearings
For application in transfer robots for semiconductor and liquid crystal manufacturing equipment, bearings are required to be
low in particle emissions and have a long service life.
Bearings may be delivered incorporated in arm units for improved assemblability and maintainability.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Bearings used in etching machines must be resistant to halogen, hydrofluoric acid, and other corrosive gasses, as well as
low in particle emissions. To meet these requirements, PTFE coated Hybrid Ceramic Bearings are used.

Use Conditions

Temperature: Room temp. to 200°C
Ambient pressure: 10−3 Pa
Lubrication: Grease or clean pro coating

Temperature: Room temp. to 60°C
Ambient pressure: Normal to 10−2 Pa
Load: Radial load of 10 N
Lubrication: PTFE coating

Bearing unit for application to transfer robots

Electron Beam Lithography

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Product: Non-magnetic Hybrid Ceramic Bearings

The bearings in semiconductor production electron beam lithography are exposed to strong magnetic fields.
Because of their non-magnetic characteristics, Hybrid Ceramic Bearings are used in such machines.

● Compatible with vacuum, strong magnetic
field environments

5

Vacuum Evaporator

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Bearings

Arms
Door

Product: High Temperature Hybrid Ceramic Bearings (with special features)

Bearings used in the planetary section of vacuum evaporator are required to be high in durability under high temperatures,
high load (moment) conditions. To ensure a long bearing life under high temperature conditions, High temperature Hybrid
Ceramic Bearings with special features are used.

● Improved reliability in vacuum andhigh temperature environments

Use Conditions

Use Conditions

Rotational speed: 100 min
Temperature: Room temp.
Ambient pressure: 10−5 Pa
Lubrication: Grease

Rotational speed: 1 to 30 min−1
Temperature: 200 to 400°C
Ambient pressure: 10− 6 to 10− 8 Pa
Lubrication: Molybdenum disulfide or silver−1

3

Product: Hybrid Ceramic Bearings (with special features)● Resistant to corrosive ambient gases such as
halogen and hydrofluoric acid
● Suitable for clean environments thanks to low
particle emissions

Use Conditions

2

Etching Equipment

Preparatorychamber● Applicable to vacuum environments andclean environments● Optimal for machine size reduction

4

Reaction chamber

1

Gates in Chemical Vapor
Deposition Equipment

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Product: Hybrid Ceramic Ball Bearing Clean Pro Linear Motion Ball Bearings

Hybrid Ceramic Ball Bearings and Clean Pro Linear Motion Ball Bearings are widely used for the doors of the chemical vapor
deposition (CVD) equipment.

● Applicable to high temperature, vacuum andclean environments

Linear motion ball bearings
Motor

6

Spin-dryer for Wafer Cleaning
Equipment

Vibration plate mounting jig

Product: Corrosion Resistant Hybrid Ceramic Bearings

In semiconductor wafer cleaning processes, wafers are cleaned in cleansing chemicals, rinsing liquids, distilled water, andother liquids before drying.
Because of their high corrosion resistance, Corrosion Resistant Hybrid Ceramic Bearings are widely used in wafer cleaners.

● Corrosion resistance to solutions such as
cleaning chemicals, rinsing liquids, anddistilled waterContainer
Bearing

Deep grooveball bearing

Use Conditions

Rotational speed: 10 to 200 min−1
Temperature: 200°C
Ambient pressure: Normal to 10−4 Pa
Lubrication: Clean pro coating

Door

Use Conditions

Rotational speed: 2 000 to 3 000 min−1
Temperature: Room temp.
Lubrication: Grease

ExhaustDeep groove ball bearing

9

10

ExhaustFlywheel

HEPA filter
FlywheelContainer

Introduction to Application Examples

CERAMIC BEARINGS

6 Semiconductor manufacturing equipment

7

CERAMIC BEARINGS

7

CERAMIC BEARINGS

Wafer Transfer Equipment

Product: Hybrid Ceramic Linear Way Bearing Units (with special features)

For application in wafer transfer equipment, low particle emissions performance is required.
For such devices, Clean Pro Hybrid Ceramic Linear Way Bearing Units are widely used.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Suitable for clean environments thanks to
low particle emissions● Corrosion resistant to cleaning agent
splashes

Polygon Scanner Motor

Product: Hybrid Ceramic Bearings

Hybrid Ceramic Bearings, which exhibit superior high speed performance, are widely used in high speed polygon scanner
motors.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueIdler

Use Conditions

Driving pulley

Stroke speed: 350 mm/s
Temperature: Room temp.
Ambient pressure: Normal pressure
Lubrication: Clean pro coating

Rail

Linear way bearing

Wafer Cleaning Equipment for
Chemical Mechanical Polishing System

Product: Corrosion Resistant Ceramic Bearings

Driven pulley
Belt

BracketIn the semiconductor multilayer production process, each wafer surface should be treated to maintain evenness. This
process uses chemical mechanical polishing equipment, and the cleaner attached to the equipment uses Corrosion ResistantCeramic Bearings.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Corrosion resistance to corrosive solutions

Rotational speed: 26 000 min−1 or higher
Lubrication: Grease2

Ultrasonic Motor in Magnetic Resonance Imagers

Product: Ceramic Bearings

The motors installed in magnetic resonance imagers (MRI) use magnetism insensitive Ceramic Bearings.

● Compatible with strong magnetic field environments

Use Conditions

Use Conditions

Rotational speed: 100 min
Temperature: Room temp.
Lubrication: Fluorine polymer

Rotational speed: 500 min−1
Temperature: Room temp.
Lubrication: Grease

−1

9

1

● Excellent reliability in high speed rotation

Use Conditions

8

Motor, Industrial machinery

Turbo Molecular Pump

Product: Full-Complement Hybrid Ceramic Ball Bearings (with special features)

Magnetic bearings are used in turbo molecular pumps driven at extremely high speeds. To protect the blades from fracture incase of a power failure or magnetic failure, touchdown bearing units are used. As touchdown bearings, Full-Complement
Hybrid Ceramic Ball Bearings are used to increase the service life of the touchdown bearings under severe hostile conditions.

● Improved reliability in vacuum environments

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque3

Switched Reluctance Motor

Product: Hybrid Ceramic Bearings

For high speed, high efficiency switched reluctance (SR) motors, which do not use coils or permanent magnets, Hybrid
Ceramic Bearings are applied.

● Excellent reliability in high speed rotation

Use Conditions

Use Conditions

Rotational speed: 20 000 to 60 000 min−1
Ambient pressure: 1 Pa
Lubrication: Molybdenum disulfide or silver

Rotational speed: 30 000 min−1
Lubrication: Grease

1112Introduction to Application Examples

8

CERAMIC BEARINGS

Medical equipment
CERAMIC BEARINGS

1

Blood Contrifuge

Product: Hybrid Ceramic Bearings (with special coating)Corrosion resistance is required of bearings to be used in blood contrifuge especially to physiological saline.
Hybrid Ceramic Bearings with bearing rings coated with a corrosion resistant film are suitable for such corrosive environments.

● Corrosion resistance to physiological saline

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

2

Shaft

Product : Hybrid Ceramic Bearings

Bearing defects occur due to electric pitting in various motors.
Hybrid ceramic bearings are utilized as a measure against electric pitting.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torqueVacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Prevention of electrical pittingHigh frequency motor
Supernatantliquid outlet

Fan Motor

Spherical plain
bearing

Rotor

Ceramic bearing
Rotor
Use Conditions

Use Conditions

Mechanical seal

Rotational speed: 20 000 min−1
Temperature: –10 to 10°C
Lubrication: Grease

Ball bearing &Spherical plain bearing
Sample inlet

Rotational speed: 5 000 min−1
Temperature: –10 to 120°C
Lubrication: Grease

Bearing mounted section

Mechanical seal

2

Ultrasonic Motor in Magnetic Resonance Imagers

Product: Ceramic Bearings

The motors installed in magnetic resonance imagers (MRI) use magnetism insensitive Ceramic Bearings.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque10

Outer space, Leisure
CERAMIC BEARINGS

1● Compatible with strong magnetic field environments

Outer Space Experimentation Equipment

Product: Ceramic Bearings

Utilized in experimental equipment on a space shuttle.
Stainless-steel bearings using fresh water as the lubricant experience abrasion and do not reach the required service life.
Using general ceramic bearings enables the required service life to be attained.
Use Conditions

Rotational speed: 500 min−1
Temperature: Room temp.
Lubrication: Grease● Long Service Life under Freshwater Lubricating Conditions

Use Conditions

9

Rotational speed: 10 000 min−1
Temperature: 30°C
Load: Radial 5N, Axial 10N
Lubrication: Fresh waterHome electrical appliances
CERAMIC BEARINGS

1

Air-conditioner motors

Product : Hybrid Ceramic Bearings

When using motors equipped with inverter control such as air-conditioner motors, there is a possibility of electric pitting
defects occurring on motor bearings.
Using a ceramic — which is an insulator — as the rolling elements eliminates electric pitting.

● CElectric pitting prevent through insulation performance

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque2

Inline Skates

Product : Hybrid Ceramic Bearings

Because of their low running torque and high durability, Hybrid Ceramic Bearings are widely used in speed skates.

● Low torque and improved durability

Use Conditions

Use Conditions

Rotational speed: 3 000 min−1
Load (preload): 1.5% C
Lubrication: Grease

Rotational speed: 10 000 min−1
Lubrication: Oil or grease

13

14

Introduction to Application Examples

11

CERAMIC BEARINGS

Automobiles, Motorcycles
CERAMIC BEARINGS

1

Turbocharger

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Product: Hybrid Ceramic Bearings

Bearings supporting the main shaft of the turbocharger are responsive during acceleration and durable when using
low-viscosity, dirty oil.
Hybrid ceramic bearings with superior reliability are utilized.

● Service life three times longer than thatof ordinary bearings● Acceleration response improved 20%● Oil quantity reduced 80%

4Rally Car Hub Units

Product: Hybrid Ceramic Bearings

Excellent abrasion resistance even under severe environmental conditions has improved durability and reliability.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Utilized in the car entered in the
Paris-Dakar Rally in 1997 and 1998
● Rigidity improved● Unsprung weight reduced

Use Conditions

Rotational speed: 180 000 to
210 000 min−1
Temperature: 350°C
Lubrication: Oil
Photos: Courtesy of Mitsubishi Motors Corporation

2

Fuel Injection System Control Valve

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque

Product: Ceramic Ball

The common rail system (fuel injection system), which enables diesel engines to feature high power, good fuel economy and low
emissions, is equipped with Ceramic Balls in the control valves.

● Compatible with high pressure fuel injection thanks to
improved wear resistance and seizure resistanceMotorcycle Superchargers

Product: Hybrid Ceramic Bearings

The new superchargers for large motorcycles utilize lightweight, high-strength ceramic balls capable of high-speed rotation. The
incorporation of ceramic balls has achieved bearings with excellent high-speed performance, heat resistance and abrasion
resistance. Additionally, when using hybrid ceramic bearings, high output is achieved even for race-specification motors operating
under harsh conditions.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● High-speed performance, heat resistanceand abrasion resistance improved● Contributes to achieving high output
supporting race specifications

Ceramic ballSolenoid valve

5

135 MPa
Use Conditions

Maximum pressure: 135 MPa

NozzleInjection
Photos: Courtesy of Kawasaki Heavy Industries, Ltd.

3

Wheel Bearings for Solar Cars

Product: Hybrid Ceramic Bearings

Stable operation of the motor section under severe open conditions of running eight hours or more per day. Improvements inweight reduction, durability and reliability.
Suppressing spinning resistance and efficiently transferring the driving force to the wheels contributes to saving power.

VacuumClean

High
temperature

Corrosive

Electric
field

Magnetic
field

High speed

Abrasion
resistanceLow torque● Australia: Covered over 3,000km vertically● South Africa: Covered over 4,000km

Use Conditions

Rotational speed: 1 000 min−1
Lubrication: Grease

Photo: Courtesy of Tokai University

15

16

Features

CERAMIC BEARINGS

Properties of ceramic materials
CERAMIC BEARINGS

1 Material characteristics

2 Rolling fatigue of ceramic materials

Table 1 below lists the mechanical and physical properties of major ceramic materials used as bearing materials. Table 2 compares silicon nitride and high carbon
chromium bearing steel.

The individual ceramic materials were tested for rolling fatigue under oil
lubrication and under water lubrication, to evaluate their applicability as
bearing material. Figs. 1 and 2 show the results of the tests.
The figures indicate that each ceramic material has a certain level of rolling
fatigue strength and that silicon nitride has the highest fatigue strength among
the ceramic materials tested.

Ceramic Material

Silicon Nitride
Si3N4

Zirconia
ZrO2

Silicon Carbide
SiC

g/cm3

3.2

6.0

3.1

Linear expansion coefficient

K−1

3.2×10−6

10.5×10−6

3.9×10−6

Vickers hardness

HV

1 500

1 200

2 200

Module of longitudinal elasticity

GPa

Property

Unit

Density

320

220

380

0.29

0.31

0.16

1 100

1 400

500

6

5

4

℃

800

200

1 000 or higher℃

750 or higher

350

350

20

3

70

680

460

670

Poisson's ratio
MPa

Three point bending strength

MPa・m1/2

Fracture toughness
Heat resistance (in atmospheric air)Thermal shock resistance
Coefficient of thermal conductivity
Specific heatW/（m・K）
J/（kg・K）

Test conditions

Silicon nitride（Si3N4）

1 250

Oil lubrication

Water lubrication

LubricantSpindle oil

City water

Ball

Bearing steel

Ceramic

Load

Increased in stages at every 1.08 × 10 7 cycles

Rotational speed

1 200 min−1

Zirconia（ZrO2）

1 000

Load (per ball), N

Table 1 Mechanical and physical properties of ceramic materials used as bearing materials

Test equipment
750

500

Silicon carbide
（SiC）

250

LubricantTable 2 Comparison of characteristics of silicon nitride and high carbon chromium bearing steel0

Property

Unit

Silicon Nitride
Si3N4High Carbon Chromium Bearing Steel
SUJ2

Density

g/cm3

3.2

7.8

Decrease in centrifugal force induced by rolling elements (balls or rollers)→ Longer service life and reduced bearing temperature rises

Linear expansion coefficient

K−1

3.2×10−6

12.5×10−6

Decreased internal clearance change due to reduced bearing temperature rises→ Lowered vibration and reduced preload changes

Vickers hardness

HV

1 500

750

Module of longitudinal elasticity

GPa

320

208

0.29

0.3

Heat resistance

℃

4.32

5.4

6.48

7.56

8.64

Fig. 1 Comparison in rolling fatigue life under oil lubrication

Ball ( 9.525 mm )Flat ceramic plateLess deformation in rolling contact areas→ Higher rigidity

800

180

Retention of superior load carrying characteristics under high temperature

Low

Useful in acid or alkaline solutions

Magnetism

Non-magnetic

Ferromagnetic

Conductivity

insulator

conductor

Prevents electrical pitting

Covalent bond

Metallic bondDecrease in adhesion (or material transfer) due to oil film thinning in rolling contact areas

Bond

3.24

1 250

High

Corrosion resistance

2.16

Stress loading cycles, × 10 7

Decreased rotational fluctuation in ferromagnetic field due to non-magnetization

Load

1 000

Load (per ball), N

Poisson's ratio

1.08

Advantages of Ceramic Bearings

Silicon nitride（Si3N4）

750

500

250

0

Test equipment appearance

Zirconia（ZrO2）

Silicon carbide
（SiC）
1.08

2.16

3.24

4.32

5.4

6.48

7.56

8.64

Stress loading cycles, × 10 7

Fig. 2 Comparison in rolling fatigue life under water lubrication

Fig. 3 Rolling fatigue life test conditions and test equipment

17

18

Features

Production Processes

CERAMIC BEARINGS

Ceramics Production Processes
CERAMIC BEARINGS

3 Ceramic materials suitable for rolling bearings

1 Production processes

Table 3 shows the results of evaluating the ceramic materials in terms of their characteristics and the rolling fatigue strength. Among the ceramic materials tested,silicon nitride is the most suitable as rolling bearing material.
JTEKT uses the silicon nitride produced by the hot isostatic pressing (HIP) method as the standard ceramic material for bearings.

With silicon nitride, characteristics such as density and strength can vary greatly depending on the manufacturing method and manufacturing conditions.
Therefore, it is necessary to strictly control items such as shape, sintering and other processes when manufacturing silicon nitride for ball and roller bearings.
The general manufacturing process is shown in Fig. 5.

Table 3 Ratings of ceramic materials as rolling bearing materials
Application to rolling bearings
Rating4

Performance and use

Characteristics

・Comparable to bearing steel in load carrying capability and service life ・High speed ・High vacuum
・Suitable for high performance applications
・Heat resistant ・Non-magnetic

Silicon nitride
Si3N4

◎

Zirconia
ZrO2○

・Useful under a limited load・Applicable in highly corrosive chemicals

・Highly corrosion resistant

Silicon carbide
SiC○

・Useful under a limited load・Applicable in highly corrosive chemicals

・Highly corrosion resistant・Corrosion resistant・High rigidity

・Highly heat resistantComposition of ceramic bearings

Raw materials

The raw materials used are silicon nitride (Si3N4) fine powder and a sintering additive.

Preparation

The raw material powder is wet blended using a solvent. During this process, the silicon nitride
powder and sintering additive are mixed evenly in the slurry state.

Raw material preparation

Drying and granulation

A binder is placed in the mixed slurry and a sprayer device is used to produce spherical particles
with a fixed granularity from the slurry state.

Formulation powder

Molding

The granulated powder is poured into a mold and compacted into the proper shape by compression.

Machining

Bearing components are machined until a state close to the final form taking shrinking and layer
alteration caused by contraction during sintering into consideration.

Molding(May be omitted depending items such as shape and accuracy of the compact.)

Degreasing

Koyo ceramic bearings are divided into Full Ceramic Bearings (with allcomponents, namely, the outer ring, inner ring and rolling elements, made ofceramic) and Hybrid Ceramic Bearings (with only the rolling elements madeof ceramic). The outer ring and inner ring of the Hybrid Ceramic Bearings are
made from special steel, including high carbon chromium bearing steel. The
cage may be made of a metallic material, resin, or composite material,
depending on the intended operating conditions of the bearing.

Compact is heated in the degreasing furnace to remove organic matter such as binders.

Ceramic

Sintering

Full Ceramic Bearing

Fig. 4 Composition of ceramic bearings

Hybrid Ceramic Bearing

HIP
Grinding process
Inspection

In the next process of hot isostatic pressing (HIP), a sealed sintered form without openings iscreated by applying sufficient gas pressure to the compact.

A detailed sintered form is attained in a high- temperature, high-pressure gas environment.

The sintered form attained in the HIP process is ground to the dimensions and surface state of the
final product.

The surface is checked after processing to ensure it does not contain cracks or pinholes.

Fig. 5 Ball and roller Bearing Silicon Nitride Manufacturing Process

19

Sintering

20

HIP

Product Details

CERAMIC BEARINGS

Ceramic Bearing Product Details
CERAMIC BEARINGS

Basic dynamic load rating
The ISO standard defines the basic dynamic load rating as the pure radial load(for radial bearings), constant in magnitude and direction, under which the basic
rating life of 1 million revolutions can be obtained, when the inner ring rotates
while the outer ring is stationary or vice versa. The basic dynamic load rating
represents the resistance of a bearing against rolling fatigue.

1 Rolling fatigue life of ceramic bearings

2 Static load rating of ceramic bearings

A typical service life test for Ceramic Bearings and steel bearings was performed
under the conditions specified in Fig. 7.
The test results showed that the service life of Ceramic Bearings was equal to or
longer than that of steel bearings, exceeding the calculated life.
The Ceramic Bearings were found to exhibit flaking (Fig. 6) when their service
life terminated. The same phenomenon was observed on the steel bearings
whose service life terminated.
Based on these findings, as the dynamic load rating of a Ceramic Bearing, that ofa steel bearing of the same dimensions can be used.

The basic static load rating of a steel bearing represents a load that produces a
localized permanent deformation in the rolling element/raceway contact area,
impeding smooth rotation.
However, ceramic materials, which are highly rigid, produce little permanent
deformation. Therefore, the theory of the basic static load rating for steel
bearings is not applicable to ceramic bearings.

Basic static load rating
The basic static load rating is defined as the static load which corresponds to thecalculated contact stress shown below, at the center of the most heavily loaded
raceway/rolling elements.
Self-aligning ball bearings：4 600 MPa
Other ball bearings：4 200 MPa
Roller bearings：4 000 MPa

Ceramic ball

Ceramic inner ring

Static load rating of Full Ceramic Bearings
When exposed to continuous excessive loads, ceramic materials may break
down; however, before breakdown occurs, the materials develop cracking.
Fig. 8 compares the load measurements at which ceramic balls developed
cracking with the basic static load ratings of steel bearings. Fig. 9 shows themeasurement system.
As these results show, the loads at which cracks develop on the Full Ceramic
Bearing are far higher than that of the basic static load rating of steel bearings.
This means that the basic load ratings specified in the ISO standard can be usedas the allowable static loads of the Full Ceramic Bearing.

70

Table 4 Load ratings of ceramic bearings

Static load rating
C 0r

Comparable to steel
bearings

85% that of steel
bearings

Load, kN

Comparable to steel
bearings

Crackdeveloping load

10

4

3
5
2

Note) The steel bearings here refer to bearings consisting of rings and rolling elements both madeof high carbon chromium bearing steel.
1

2

4

6

8 10

20

6206

Bearing steel (SUJ2)

Specification

0.5

̶

0.5

1.3

1.9

̶

1.9

2.6

5.2

̶

5.2

3.9

9.3

̶

9.3

0.65

0.4

̶

0.4

1.3

1.3

0.11

1.41

2.6

4.0

0.41

4.41

3.9

6.8

1.18

7.98

Basic static load rating for steel bearing(load that generates a contact stress of 4 600 MPa)
Load

25

50

75

Ball

Dimensions, mm
30 × 62 × 16
(bore × outside dia. × width)

Load
meter

Fig. 8 Crack developing loads for Full Ceramic Bearings

Flat plate

Noise
Filter andsuppressor
amplifierAcoustic emission
transducer
Filter andamplifierCondition

Load

5 800 N

Rotational speed

8 000 min−1

Lubrication oil

AeroShell Turbine Oil 500

Temperature

70 ± 2 ℃

Recorder100Fig. 9 Crack generating load measurement system

Fig. 7 Rolling fatigue life of Full ceramic bearings and steel bearings
21

0.65

(Ball diameter Dw)2，mm2

Bearing number Material (outer/inner rings and balls)
Silicon nitride (Si3N4)

Permanent deformation(sum of averages), mm

10Rolling fatigue test conditions
NC6206Ball

Load cell

Calculated life ratio(actual life / calculated life)

Permanent deformation (average), mm
Flat plate (bearing steel)

These results indicate that ceramic balls do not suffer permanent deformationand that the permanent deformation produced on the flat steel plate by theceramic balls is approximately 1.2 times the sum of the deformation producedon the flat plate by steel ball and the deformation that the steel ball undergo.
Accordingly, the static load rating of Hybrid Ceramic Bearings can be determinedbased on the permanent deformation of their bearing steel rings. JTEKT uses theload equal to 85% of the static load rating of steel bearings as the static load
rating of the Hybrid Ceramic Bearings.

5

Failure, %Comparable to steel
bearings

LoadkN

Steel ball

6

30

Dynamic load rating
Cr

Table 5 Measurements of permanent deformation producedon flat steel plate and balls

7

Full Ceramic Bearing
NC6206

Steel bearing
6206

50

Full Ceramic Bearing

The theory of the static load rating for steel bearings is applicable to Hybrid
Ceramic Bearings because their outer and inner rings are made of steel andaccordingly any deformation is permanent.
Table 5 shows the results of a test for which a high carbon chromium bearing
steel ball and ceramic ball were pressed against a flat plate of high carbon
chromium bearing steel and the resulting permanent deformations (indentation
depths) on the flat plate and balls were measured.

Fig. 6 Flaking on ceramic ball and inner ring

JTEKT defines the dynamic load rating and static load rating of ceramic bearings
based on the results of their service life tests, the maximum allowable static loadof the ceramic materials, the elastic deformation test results of high carbon
chromium bearing steel, and other related data, as shown in Table 4.

Hybrid Ceramic
Bearing

Static load rating of Hybrid Ceramic Bearings

Ceramic ballSilicon nitride, a ceramic material, is more rigid than high carbon chromium
bearing steel; therefore, a bearing including silicon nitride components is subject
to a higher contact stress on the area of contact between bearing raceways androlling elements. Accordingly, to estimate the service life of ceramic bearings,
whether the rolling bearing theory is applicable or not is critical.

22

Counter

Product Details

CERAMIC BEARINGS

3 Impact strength of ceramic bearings

4 Fitting of ceramic bearings

To evaluate the impact strength of ceramic bearings, ceramic balls werecrushed by two methods: by a static load and an impact load. The test results
are shown in Fig. 10. Fig. 11 shows the testing methods.
This figure shows that the impact strength of the ceramic bearings is almost
equal to the static load strength, which means the bearings possess sufficient
impact strength.

When using ceramic bearings, it should be noted that ceramic materials arelargely different from steel materials in the coefficient of linear expansion.
Attention should therefore be paid to fitting stresses and temperature rises.
The following are the results of evaluating the fitting of a Ceramic Bearing ona stainless steel shaft.

Static crushing test
Load

Table 6 Typical results of static strength test on ceramic bearing shaft fitting
Interference, L10µm

Ring's fracture stress
MPa

Solid shaft

50

399

Hollow shaft

68

332

Table 7 Typical results of dynamic strength test on ceramic bearing shaft fitting
Housing
99

Outer ring

Jig made ofbearing steel

80

Inner ring

Ceramic balls(9.525 mm in dia.)Max. allowable stress for ring
MPa

Solid shaft

31

243

Hollow shaft

43

204

Shaft

60

Impact crushing load

40

Failure, %Max. allowable interferenceµm

Static crushing load

20
10

Fig. 12 Bearing fitting

5

Maximum stress produced by fitting

Impact crushing test

2
1

Weight 50 kg
0

1 2

5

10

20

30 40

100

Crushing load, kN
Load cellFig. 10 Comparison of static load and impact load that crush ceramic balls

Table 6 shows the results of a static strength test conducted on a ceramic ring
fitted on a stainless steel shaft. Table 7 shows the results of a dynamic
strength test (running test) conducted on a ceramic ring fitted on a stainlesssteel shaft.
Based on the results of these tests, JTEKT makes it a rule for the maximum
stress produced by interference to be no greater than 150 MPa when aceramic inner ring is fitted on a stainless steel shaft.
Consult JTEKT for applications requiring tighter fitting.

Fig. 13 Ceramic inner ring damaged by dynamic strength test

Influence of temperature
During operation, bearing temperature exceeds the ambient temperature.
When a ceramic bearing is operated on a stainless steel shaft or in a stainlesssteel housing, the interference with the shaft increases due to the difference inlinear expansion coefficient while the interference with the housing decreases.
(When the outer ring is loose-fitted, the clearance increases.)
To determine the class of fit for a ceramic bearing, the maximum temperatureduring operation should be assessed carefully.

Dropping

Jig made ofbearing steel

Ceramic balls(9.525 mm in dia.)■ The maximum stress generated on the inner ring due to the interference with the shaft can be determinedfrom the following equation:
D i2 + d 2
σ = P m・ 2 − 2
Di dFig. 11 Ceramic ball crushing test method

23

P m = ⊿ deff

(

2 +

)

d Di dd+ νB +E B D i2 −d 2ES2

( dd dd − )
2+

2−

2

0

2

0

νS

-1

24

σ

: Maximum circumferential stress to interference

（MPa）

Pm

: Pressure of contact on fitting surface（MPa）d , Di: Inner ring bore diameter and outside diameter（mm ）⊿ deff: Effective interference of inner ring

（mm ）

d0

: Bore diameter of hollow shaft（mm ）E B , νB

: Bearing's modulus of longitudinal elasticity and Poisson's ratio（MPa）

E S , νS

: Shaft's modulus of longitudinal elasticity and Poisson's ratio （MPa）

Performance

CERAMIC BEARINGS

Ceramic Bearing Capacities
CERAMIC BEARINGS

2 Non-magnetic performance
There are two types of ceramic corrosion: One is the corrosion of thealumina-yttria system sintering aid (Al2O3-Y2O3), which is used to bake ceramicmaterials. To avoid this type of corrosion, corrosion resistant silicon nitride
treated with a spinel sintering aid (MgAl2O4) should be used. Fig. 14 shows themass reduction and bending strength deterioration of corrosion resistant silicon
nitride dipped in an acid or alkaline solution for a given period of time.
The other type of corrosion is the corrosion of the silicon nitride itself. For use
in a highly corrosive solution, bearings made of zirconia (ZrO2) or siliconcarbide (SiC) may be effective.
To select a ceramic bearing for use in a highly corrosive environment, its
corrosion resistance to the specific condition should be carefully examined.

Table 8 shows the corrosion resistance of ceramic materials. Silicon nitride,
which is used as the standard material of the ceramic bearings, is excellent incorrosion resistance. However, it may develop corrosion in a highly corrosive
chemical, a high temperature, or other highly corrosive ambient condition.
Table 8 Corrosion resistance of ceramic materials○：Almost resistant△：Slightly susceptible

×：Susceptible

Si3N4

Corrosion
resistantsilicon nitride
Si3N4

Zirconia
ZrO2

Silicon Carbide
SiC

Hydrochloric acid

△

◯

◯

◎

Nitric acid

△

◯

◯

◎

Sulfuric acid

△

◯

◯

◎

Phosphoric acid

◯

◯

◯

◎

Fluorine acid

△

△

×

◎

Corrosive
solutions

Ceramic
Silicon nitride
materials (standard)

Sodium hydroxide

△

△

◯

△

Potassium hydroxide

△

△

△

△

Sodium carbonate

△

△

△

△

Sodium nitrate

△

△

△

△

Water and saltwater

◎

◎

◎

◎

Note) The corrosive natures of individual solutions differ largely depending on the concentrationand temperature. Note that mixing two or more chemicals may increase the corrosivity.

80℃, 35 ％ HCl × 100h

80℃, 35 ％ KOH × 100h

Standard Corrosion
resistantStandard Corrosion
resistant

80℃, 35 ％ HCl × 100h

80℃, 35 ％ KOH × 100h

Bearings may be exposed to magnetic fields in some applications, including
equipment associated with super conductivity, semiconductor production
facilities and medical examination facililies. If steel bearings are used for suchapplications, the running torque may fluctuate or the magnetic field may be
disturbed . Non-magnetic bearings should be used for such applications. As a
non-magnetic material for such bearings, beryllium copper has conventionallybeen used. However the use of beryllium copper should be avoided since it
contains beryllium, a substance of environmental concern.
For such applications, JTEKT supplies Hybrid Ceramic Bearings, whose rings
are made of non-magnetic stainless steel and rolling elements are made of aceramic material, or the full ceramic bearings.

0.2

0.1

0

Bending strength deterioration, %◎：Fully resistant

Mass reduction, %1 Corrosion resistance

Table 10 Non-magnetic bearings and relative permeability

40

Relative permeability

30
20
10
0

Standard Corrosion
resistantNon-magnetic Hybrid Ceramic Bearings

1.01 or lower

Ceramic Bearing

1.001 or lower(Ref.) Beryllium copper

1.001 or lower

Fig. 16 shows a rolling fatigue strength evaluation result for various
non-magnetic materials. As can be seen from the figure, non-magnetic stainlesssteel is superior to beryllium copper in rolling fatigue strength.

Standard Corrosion
resistantFig. 14 Anticorrosive performance of corrosion resistant silicon nitride
4

Silicon nitride

Service life of corrosion resistant bearings

3

Load, kN

Table 9 lists the bearings suitable for applications requiring corrosion resistance, along with their major applications.
Table 9 Typical corrosion resistant Ceramic Bearings
Bearing Materials

Corrosion Resistant Hybrid Ceramic Bearing
Ceramic Bearing
Corrosion Resistant Ceramic Bearing
High Corrosion Resistant Ceramic Bearing

In water, alkaline environment andreactive gas
In a slightly acidic environment, alkaline
environment and reactive gas
In a strongly acidic environment, strongly
alkaline environment and reactive gas
In a strongly acidic environment, strongly
alkaline environment and corrosive gas

Bearing Rings

Balls

SUS630Silicon nitride

Silicon nitride

Silicon nitride

Corrosion resistant silicon nitride
Silicon carbide

Beryllium copper

Hybrid Ceramic Bearing(Bearing rings: SUS440C)

100

SUS440C has a longer service life than SUS630; however, the former steel is notsuitable for use in water because it may rust and cause contamination.
Ceramic Bearings may develop wear at an early stage of use depending on thecharacteristics of the solution, temperature, and load. Please contact JTEKT
before using Ceramic Bearings in solutions.

Ceramic Bearing

300

400

500

Test conditions
50

Service life ratingof steel bearings

Rotational speed

1 200 min –1

Temperature

Room temp.

10

Down to 3%
5

Lubricant
1
10

50

100

Test conditions
Bearing No.: 6206 or equivalent
Rotational speed: 1 500 min−1

500

1 000

5 000

10 000Service life, hCeramic balls（9.525 mm）

Radial load:
Ceramic Bearing: 1 470 N
Corrosion Resistant Hybrid Ceramic Bearing: 196 N
Hybrid Ceramic Bearing: 196 N

Test specimen
Load

Fig. 15 Comparison in underwater service life of Ceramic Bearings
25

200

Time, hCorrosion resistant silicon nitride
Silicon carbide

Non-magnetic stainless steel

190

enough, such as in water, it is important to evaluate in advance the susceptibilityof the bearings to corrosion and the relationship between the bearing load andwear in the solution.

When Ceramic Bearings are operated in a solution, the solution serves as alubricant. This means the solution is closely associated with the service life of
the bearings. Fig. 15 shows the service life evaluation results for three types ofCeramic Bearings under water.
The Ceramic Bearings terminate their service life due to the flaking on the
bearing ring or ball surfaces.
In case of the Hybrid Ceramic Bearings, ceramic balls do not develop flaking or
wear. Their service life ends due to wear attributed to the minute corrosion ofstainless steel bearing rings.
When bearings are used in a solution whose lubrication performance is not

Corrosion Resistant Hybrid
Ceramic Bearing(Bearing rings: SUS630)

Failure, %Applications

2

Fig. 16 Comparison of non-magnetic materials in rolling fatigue strength26Performance

CERAMIC BEARINGS

3 Insulation

4 High-speed performance

A cause of bearing failure in motors or generators is electric pitting. Electric
pitting occurs when a surface in rolling contact is locally molten due to sparks
produced over the very thin lubricating oil film on the surface when electricity
passes through the bearing in operation.
Electric pitting appears as a series of pits or a series of ridges on the surface inrolling contact, which is shown in Fig. 17 and Fig. 18.
An estimation of the mechanism that causes electric pitting on a bearing isshown in Fig. 19.

Hybrid Ceramic Bearings, whose rolling elements are made of a ceramic material
with a density lower than that of bearing steel, are most suitable for high speed
applications. This is because reduced mass of rolling elements suppresses thecentrifugal force of the rolling elements, as well as slippage attributable to the
gyro-moment, when the bearings are in operation.
Thanks to their superior high speed performance, Hybrid Ceramic Bearings areused in turbochargers and on machine tool spindles.

Continuous sparks of weak current
Example of electric pitting on inner ring raceway surface

Seizure limit at high speed
Fig. 21 shows the seizure limits of Hybrid Ceramic Bearings and steel bearings.
The limits were measured by gradually reducing lubricating oil feed rate.
Compared with general purpose steel bearings, Hybrid Ceramic Bearings
consume smaller amount of lubricating oil under the same speed condition, while
they can run at a higher speed under the same luburicating oil feed rate condition.

Power losses at high speed

Fig. 18
Electric pitting generated on
general purpose bearings(ridges)Wave-like wear
marks along entire
inner ring raceway
surfaceTo avoid such pitting, a bypass is provided to ensure that no electric current
passes through the bearing. Another method is to use an insulating bearing thatcan block electric current.
Since ceramic materials exhibit an excellent insulation performance, Hybrid
Ceramic Bearings consisting of ceramic rolling elements can be used as
insulating bearings.
Hybrid Ceramic Bearings prevent electric pitting, also reduce bearing
temperature rise, and lengthen grease service life. For these reasons, Hybrid
Ceramic Bearings assure long term maintenance free operation and high speed
equipment operation.

Steel bearing, seizedHybrid Ceramic Bearing, runningHybrid Ceramic Bearing, seized
0.5

0.4

Lubrication oil feed rate, L/min.

Wave-like wear

2

Steel bearings

Power loss, kW

1.5

0.3

Steel bearing
seizure limit
0.2

HybridCeramic Bearing
seizure limit

0.1

1
0

40

60

80

100

120

Rotational speed, ×103 min−1

HybridCeramic Bearings
0.5

Fig. 21 Comparison between Hybrid Ceramic Bearings andsteel bearings in seizure limit

Electrical potential difference generated
between inner and outer ring when motor runs0

Current flows through oil film between
raceway rolling surface/balls
Bearing rings

Rolling portion surface
temperature rises - softens

Ball rolling
Rolling surface wear

Wave-life wear occurs

Fig. 19 Estimation of electric pitting (wave-like wear) occurrence mechanism
27

20

40

60

80

100

Rotational speed, ×103 min−1

Balls

Fig. 17
Electric pitting generated on
general purpose bearings(pits)

Steel bearing, running

Fig. 20 compares power losses between the Hybrid Ceramic Bearings andsteel bearings.
When compared to steel bearings, the Hybrid Ceramic Bearings lose smaller
power during high speed operation. The power loss decreases with increasing
rotational speed.
The Hybrid Ceramic Bearings also have superior antiseizure characteristics,
which means that they consume smaller amount of lubrication oil and thereby
reduce rolling resistance (power loss).

Hybrid Ceramic Bearings
Steel bearings
High speed tool steel (M50)

Material
Dia.
Number of balls
Cage

Condition
Axial load
Rotational speed (max.)
Lubricating oil
Ambient temperature

Ceramic(Si3N4)High speed tool steel(M50)
6.35 mm9
Polyimide resin
Specification
200 N
100 000 min−1
AeroShell Turbine Oil 500
Room temp.

Fig. 20 Comparison in power loss between Hybrid Ceramic Bearings and steel bearings28

Product Introduction

1

CERAMIC BEARINGS

Ceramic balls
CERAMIC BEARINGSJTEKT also supplies Ceramic Balls (silicon nitride), which have excellent
resistance to wear and seizure, and are usable in corrosive environments andultrahigh vacuums. Other major features of these balls are excellent heat
resistance (up to 800°C), high rigidity, lightweight (40% compared tobearing steel), non-magnetic, and have insulating characteristics.
The Ceramic Balls are useful in many applications such as jigs, tools,
gauges, solenoid valves, check valves, other valve varieties, high grade
bicycle parts, automotive parts, and machine components.

Table of Dimensions and Masses
Nominal dimension
mm

inch

Nominal outside
diametermm

Precision
grade 1)inch

Nominal outside
diametermm

Nominal dimension

Mass 2)(per piece)mm

Precision
grade 1)Mass 2)(per piece)

0.80.800 00

0.866 mg

7/16

11.112 75

1.0

1.000 00

1.691 mg

15/32

11.906 25

1.200 00

2.922 mg

1/2

12.700 00

1.587 50

6.766 mg17/32

13.493 75

4.2 g

2.000 00

13.530 mg

9/16

14.287 50

4.9 g

22.836 mg

19/32

15.081 25

5.8 g

36.262 mg

5/8

15.875 00

6.8 g
11.7 g

1.2
1/16
2.0
3/32

2.381 25

7/64

2.778 121/8

3.175 00

54.129 mg

3/4

19.050 00

3 and 52.320 8 g
5 and 102.854 5 g
3.46 g3.500 00

72.511 mg

13/16

20.637 50

5/32

3.968 75

0.105 7 g

7/8

22.225 00

18.6 g3/16

4.762 500.182 7 g

15/16

23.812 50

22.8 g7/32

5.556 250.290 1 g

125.400 00

27.7 g15/64

5.953 120.356 8 g

1 1/8

28.575 00

39.5 g46.4 g3.5

1/4

6.350 00

0.433 0 g

1 3/1630.162 50

17/64

6.746 880.519 4 g

1 1/4

31.750 00

9/32

7.143 75

0.616 6 g

1 5/1633.337 50

0.845 8 g

1 1/2

38.100 00

5/16

7.937 50

11/32

8.731 25

3/8

9.525 00

1.461 5 g

13/32

10.318 75

1.858 2 g

540

14.9 g54.1 g60

62.7 g93.5 g1.125 7 g

Notes 1) For the grades, those specified in JIS B 1501 shall apply.
2) The masses are calculated on the basis of 3.23 g/cm3 in density.

Numbering System

5/32 G5 NCR
Material code: silicon nitride ceramic
Precision grade code
Nominal dimension

29

30

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CAT. NO. B1013E-A
Printed in Japan '15.12-1CCH