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Ceramic Bearing and Bearing Ball
Ceramic material are noted for their characters of high strength in high temperature, good wearability, high rigidity, corrosion resistance, high  temperature resistance, electrical insulation, non-magnetic, there characters qualify them for replacing steel to make bearing to meet the requirements in a severe condition where a steel bearing can¡¯t wyghstand. Ceramics material which can be used in making bearings, in clued mainly Silicon carbide(SiC), Silicon Nitride(Si3N4), Zirconia(ZrO2) and Alumina(Al2O3) etc. Si3N4 is in speaking form, which bearing steel also has but ZrO2 and Al2O3 fail in a crush form, a catastrophic failure. They are  mainly used for the transmit device of high temperature furnaces; high-speed rotation field; aviation and airspace fields; the main shaft of machine tools; chemical machinery, food industry and marine industry; high vacuum field; strong magnetic environment; roller skates, model airplanes and motor-driven toys so on in civil use etc.
Specification
| |
Bearing
steel |
Stainless
steel |
Si3N4 |
ZrO2 |
SiC |
Al2O3 |
Density g/cm3 |
7.85 |
7.9 |
3.20-3.30 |
6.00 |
3.10 |
3.95 |
Coefficient of linear expansion 10-6/K |
10.0 |
11.0 |
3.2 |
10.5 |
4.5 |
8.5 |
Poisson's ratio |
0.30 |
0.30 |
0.26 |
0.30 |
0.20 |
0.22 |
Hardness
HV HRC |
700
60-66 |
55-60 |
1300-1600
75-80 |
1000-1200
70 |
2500min
85-90 |
1600-1800
80 |
Bending strength Mpa |
2400 |
|
600-1000 |
950-1200 |
450 min |
300-500 |
Fracture toughness Mpam1/2 |
25 |
|
5.0-7.0 |
8.0-10.0 |
3.0-4.0 |
3.0-4.0 |
Thermal conductivity
W/mk |
30-40 |
15 |
35 |
2-3 |
150 |
30 |
Special electrical
resistance
¦¸ mm2/m |
0.1-1 |
0.75 |
108-1018 |
105-1015 |
10-103 |
108-1018 |
Max working
temperature ¡æ |
120 |
300 |
800 |
|
1400 |
|
Corrosion resistance |
poor |
poor |
good |
good |
good |
Good |
Stress cycles
(50% failed) |
107 |
|
107-109 |
105 |
|
|
No lubrication friction |
Large |
Large |
Little |
Little |
Little |
|
Magnetism |
Magnetism |
Magnetic |
No |
No |
No |
No |
Centrifugal force |
Very large |
Very large |
Little |
Large |
Little |
Middle |
Operate temperature
increasing |
High |
High |
Low |
|
Low |
|
Size stability |
Unstable |
Unstable |
Stable |
Unstable |
Stable |
Unstable |
Conductivity |
Conductor |
Conductor |
Insulator |
Insulator |
Conductor |
Insulator |
Rolling contact failure form |
Spalling |
Spalling |
Spalling |
Crush |
Crush |
Crush |
|
