FRETTING CORROSION AND ITS EFFECTS
When converting to a self-lubricating bearing, the external lubricant film is removed from the bearing load zone. This allows contact between the bearing and the shaft. This contact can cause fretting corrosion under the following conditions:
Examples of fretting corrosion causes
| Motion |
Example |
| Small angles of oscillation |
Toggle linkage |
| Small relative motion |
Linear movement of a shaft in a shock absorber |
| Vibration |
Torsional vibration from a diesel engine crank shaft or an unbalanced electric motor |
| Cyclic loading |
Variable speed belt drives |
| |
Metallic surfaces exposed to the above conditions start to fatigue. Particles break off and begin to oxidize resulting in fretting corrosion. It can occur at high or low loads. In ferrous metals this produces a residue of iron oxide, a reddish appearing dust commonly called Jeweler’s rouge. These metallic particles are very abrasive and can cause wear of the shaft surface and bearing. This can occur even if the shaft surfaces are 50 RC or harder.
*Fretting corrosion of steel shafts.
Fretting Corrosion Solutions
A hard, corrosion resistant wear surface will minimize fretting corrosion. Several processes have been used to eliminate fretting corrosion as follows:&
- Polished hard chrome plating .0003/.0005 inches thick.
- Electroless nickel plating .0003/.0005 inches thick.
- Melonite QPQ heat treatment.
Other considerations are necessary when selecting the above processes. Contact engineering for an in-depth analysis.
Melonite QPQ™ is a trademark of Houghton Durferrit GmbH, Germany. |
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