A wind gearbox bearing is standard chrome steel with an unstandard level of documentation: the steel cleanliness and the traceability are what the price buys. Wind Turbines duty is very long life, oscillating pitch and yaw motion, moisture ingress; the material is what decides whether the bearing survives it.
| Industry duty | combined radial, axial and tilting-moment load over a 20-year life target |
|---|---|
| Typical media | moisture, salt air offshore, old grease |
| Housing temperature | −30 to +60 °C |
| Material and grade | through-hardened chrome steel — 100Cr6 / 52100 |
| Hardness | 59–65 HRC |
| Temperature ceiling | 120 °C (200 °C stabilised) |
| Corrosion / chemical | none — rusts without protection |
| Relative cost | 1.0× of a standard 52100 bearing |
A wind turbine gearbox is designed for 20 years with no oil change to speak of and no easy access. The bearings see load reversals, slip and a lubricant that degrades slowly. Under those conditions the fatigue life depends on the size and population of non-metallic inclusions in the steel far more than on the hardness, which is why a wind bearing is bought on a cleanliness specification and a 3.1 certificate with a heat number that can be traced to the melt.
| Position | Bearing type | Material / finish | Why it works there |
|---|---|---|---|
| Planet gear | Cylindrical roller | 52100, NU/NJ, C3, special cleanliness | High radial load in a small envelope; steel cleanliness drives life. |
| Helical stage | Tapered roller | 52100, matched pair | Combined load; preset removes field adjustment. |
| Main shaft | Self-aligning roller | 52100, 240xx/241xx, C3 | Very high load with shaft deflection. |
| Generator drive end | Deep groove ball | 52100, C3, insulated option | Speed with light load; converter voltage is the risk. |
| Material | Fit here | Choose it when |
|---|---|---|
| 100Cr6 / 52100 | Best fit | The volume choice, bought on steel cleanliness and traceability. |
| Si3N4 | Workable alternative | Generator and high-speed positions where converter voltage erodes the raceway. |
| Bronze | Workable alternative | Yaw and pitch sliding surfaces rather than rolling positions. |
Because of the documentation and the steel quality, not the alloy. A bearing with the same dimensions and a generic certificate is a different product.
A subsurface crack that forms under repeated load reversals with slip, and propagates to spalling. It is a wind gearbox failure mode and it is influenced by the steel and the lubricant additive package.
Usually the same grade at a much larger size, with a case or a through-hardened structure chosen for the load. The housing and the seal are the harder problem.
Hardness, temperature, corrosion and equivalents for 52100 chrome steel.
Read →Typical duty, recommended types and suffixes for wind energy.
Read →Generator & high speed — generator bearings and high-speed stages where converter voltage and speed limit steel.
Read →Yaw & pitch sliding — yaw drive bushes, pitch bearing spacers and blade root sliding surfaces.
Read →Send the position, bore size, quantity and the medium it sees. We reply with the material certificate, clearance class, lubricant and price within 30 minutes on working days.