NEW PRODUCTCorrosion Resistant Bearings
JTEKT has a series of “EXSEV* bearings for use in special environments”
that responds to various special environments such as vacuum or hightemperature conditions where normal lubricants and grease cannot be used,
and we have been providing such bearings broadly for customers such as in
the semi-conductor manufacturing field. The environment which especiallyrequires corrosion resistance is not only the semi-conductor manufacturing
field, but also many other fields such as FPD, film manufacturing equipment,
and chemical applications manufacturing processes, and various corrosion
resistant bearings are being used. This article introduces its features.
* Extreme Special Environment

1. Main Materials and Corrosion Resistant Test Results
The bearings used in corrosive environments are splashed with or immersed in strong acid, strong alkali, and otherhighly corrosive chemical liquids, therefore selection of materials suitable for applications is required. This is why
corrosion resistant bearings are composed of ceramics and stainless steels. Table 1 shows the characteristics of thematerials, Fig. 1 shows the scope of application of corrosion resistant materials (bearing ring), and Table 2 and Fig. 2show the corrosion resistant test examples.
Table 1 Characteristics of Ceramics and Stainless Steels
Material

Bearingcomponent
Density, g/cm3Hardness
Modules oflongitudinalelasticity, GPa

Ceramics
SiliconNitride(Si3N4)

Corrosion
Resistant
Silicon Nitride(Si3N4)

Zirconia(ZrO2)

SiliconCarbide(SiC)

3.2
1 500 HV

3.2
1 500 HV

6.0
1 200 HV

3.1
2 200 HV

320

320

220

380

208

196

208

Table 2 Test conditions of corrosion resistance (CASS)HighLoadability (durability)

Stainless steelPrecipitation
High-hardness
Martensitic
hardeningand corrosionstainless steel
stainlessresistant(SUS440C)
steel
stainless steel(SUS630)
7.65
7.70
7.68
60 HRC
40 HRC
60 HRC

Silicon Nitride(Si3N4)

Corrosion Resistant
Silicon Nitride (Si3N4)

Liquid used

Zirconia (ZrO2)
Silicon Carbide
High-hardness and (SiC)
corrosion-resistant stainless steel＊Low
Alkali environment
Acid environment
HighHigh
Environment
Martensitic stainless steel
Precipitation hardening stainless steel
SUS440C
SUS630Sodium chloride: 50 ± 5 g/8
Copper chloride (II): 0.26 ± 0.02 g/8pH

3.0 to 3.2

Temperature

50 ± 2℃

Test time

4h

CASS test is a spraying test method to check thecorrosion resistance. CASS complies with JIS Z 2371.
CASS: Copper-Accelerated Acetic Acid Salt Spray

Fig. 1 Scope of application of corrosion resistant materials(bearing ring)

JTEKT CORPORATIONJTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)85

NEW PRODUCTCorrosion Resistant
Silicon Nitride (Si3N4)

High-hardness and corrosionresistant stainless steel

HighPrecipitation hardening
stainless steel (SUS630)

Martensitic stainless steel(SUS440C)

Corrosion Resistance

Bearing steel(SUJ2)

Low

Fig. 2 Corrosion resistant test examples (CASS test results)

2. Product Line-up
The line-up of our main corrosion resistant bearings is shown below.
■ Ceramic bearing ring
ProductnameProductspeciﬁcations

Environment

Corrosion ResistantCeramic Bearings

Ceramic Bearings

High Corrosion ResistantCeramic Bearings

Silicon Nitride (Si3N4)

Corrosion Resistant Silicon Nitride (Si3N4)

Silicon Carbide (SiC)

Outer ring Inner ring Ball

Outer ring Inner ring Ball

Outer ring Inner ring Ball

Fluorocarbon resin

Fluorocarbon resin

Fluorocarbon resinCage

Cage

Acidity: Weak
Alkalinity: Middle
Load: HighAcidity: Middle
Alkalinity: Middle
Load: HighCage

Acidity: Strong
Load: Low

■ Stainless steel bearing ring
ProductnameCorrosion Resistant Hybrid
Ceramic Bearings

Corrosion Guard Pro Bearings

Precipitation hardening
stainless steel (SUS630)

Product
speciﬁcations

High-hardness and corrosion-resistant stainless steel

Outer ring Inner ring

Outer ring Inner ring

Silicon Nitride (Si3N4)

Corrosion Resistant Silicon Nitride (Si3N4)
BallBallPEEK resin

Fluorocarbon resin

Cage

Cage
Austenitic stainless steel
ShieldEnvironment

Acidity: WeakAlkalinity: Weak
Load: Low

Acidity: Weak
Alkalinity: Weak
Load: Middle

3. Application Examples
Such as film manufacturing equipment, wafer cleaning equipment, aluminum foil capacitor manufacturing equipment,
food machinery, and chemical liquid stirring equipment.
*1 EXSEV is a registered trademark of JTEKT Corporation.
(Industrial Machinery Application Engineering Dept., Bearing Operations Headquarters)

JTEKT CORPORATION86

JTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)