For long term performance ball bearings must have some form of lubrication. Grease and oil is recommended whenever the application will allow it.
Generally grease is selected for low to medium speed applications and oil is selected for high speed applications.
Special environments such as vacuum, high and low temperatures may not allow conventional lubrication. In some applications the addition of grease or oil could contaminate a product. Many specialty lubrications are available to satisfy specific operating conditions.
For low speed low load applications or for when cleanliness and vacuum call for it a solid dry film lubricant coating such as Tungsten Disulfide or Moly Disulfide is a viable option.
Many specialty lubrications are available to satisfy specific operating conditions those listed below are our most common and are for comparison purposes only. There is no perfect lubrication and for specialty applications selection is made on a case by case basis. Data sheets should be analyzed for suitability.
| MFG | BRAND | SPEED CAPABILITY | OPERATING TEMPERATURE |
|---|---|---|---|
| CHEVRON | SRI | LOW TO HIGH | -20 F to 305 F |
| EXXON | POLYREX-EM | LOW TO HIGH | -20 F to 350 F |
| DUPONT | KRYTOX | LOW TO MED | -50 F to 600 F |
| CASTROL | BRAYCOTE 601 | LOW TO HIGH | -112 F to 400 F |
| KLUBER | ISOFLEX NB52 | LOW TO HIGH | -58 F to 302F |
Solid lubricants offer excellent lubrication under extreme conditions.
When conditions exceed the limitations of wet lubricants as is found in high temperature vacuum applications, a dry solid lubricant coating can provide the boundary between rolling element and raceway reducing stress and increasing life.
These coatings are most beneficial to all steel bearings running dry where the boundary created by the coating can reduce micro-welding. For hybrid type bearings coatings can add additional life for critical applications.
| Properties | Tungsten Disulfide (WS2) | Molybdenum Disulfide (MoS2) |
|---|---|---|
| Color | Silver Gray | Blue-Silver Gray |
| Appearance | Crystalline Solid | Crystalline Solid |
| Melting Point (º C) | 1250º C | 1185º C |
| Adhesion | Mechanical-molecular interlock | - |
| Density | 7.4 grams/cc | 5.0 grams/cc |
| Molecular Weight | 248 | 160 |
| Coefficient of Friction | 0.03 – inclined plane technique | 0.03 – inclined plane technique |
| Thermal Stability in Air | COF <0.1 till 1100ºF (594ºC) | COF <0.1 @600ºF (316ºC) increases to 0.5 @1100ºF (594ºC) |
| Thermal Stability in Argon | COF <0.1 till 1500ºF (815ºC) | COF increases rapidly starting @800ºF (426ºC) COF >0.1 @900ºF (482ºC) |
| Load Bearing Ability | Same as substrate to 350,000 PSI | to 250,000 PSI |
| Lubrication Temperature Range | Ambient: from -273ºC to 650ºC Vacuum(10-14 Torr): from -188ºC to 1316ºC | Ambient: from -185ºC to 350ºC Vacuum: from -185ºC to 1100ºC |
| Chemical Stability | Inert, non-Toxic | Inert, non-Toxic |
| Magnetism | Non-Magnetic | Non-Magnetic |
| Electrical Properties | Has Semiconductor properties | - |
| Rockwell Hardness | 30HRc | |
| Coating Film Thickness | 0.5 micron | 0.5 micron |
| Corrosion Resistance | Minor delay, will not inhibit | Minor delay, will not inhibit |