|
Silicone
Nitride
Silicon nitride performs much better
than steel in rolling contact fatigue making it an
ideal rolling element material for bearings. It is
significantly harder with a 60% lower density and
a 50% higher Young’s Modulus than typical bearing
steels. These properties when combined with a low
thermal expansion and coefficient of friction against
steel are essential to improved rolling element performance
in a bearing.
Si3N4 vs. Steel
as a Bearing Material
| Property
|
Ceramic
|
M50
|
440C
Steel
|
Vacuum
Melt
|
Air
Melt
|
|
|
Si3N4 |
Steel |
|
52100
Steel |
52100
Steel |
|
Density
(g/cc)
|
3.2
|
7.6
|
7.8
|
7.8
|
7.8
|
| Hardness
(Rc)
|
>78
|
64
|
59
|
62
|
62
|
| Elastic
Modulus
(GPa)
|
320
|
190
|
200
|
210
|
210
|
| PoissonÕs
Ratio
|
0.26
|
0.28
|
0.28
|
0.28
|
0.28
|
| Thermal
Expansion
Coefficient
(10-6/C)
(RT
to 800C)
|
2.9
|
12.3
|
10.1
|
10.9
|
10.9
|
| Max
Use Temp (C)
|
1000
|
320
|
180
|
180
|
180
|
| Material
Fatigue
Life,
Wear
Resistance |
>100X
|
10X
|
0.8X
|
5X
|
1X
|
|
•