What Does Fretting Mean?
Fretting is wear that occurs as two or more materials are repeatedly moved against one another under a load. Vibration is one of the most common causes of fretting. Fretting causes the surface of one or more of the materials involved to be degraded. This degradation often consists of grooves and pits. Surface degradation from fretting allows for corrosion of the materials to occur.
Corrosionpedia Explains Fretting
The movement involved during fretting does not have to be large; its magnitude is sometimes measured in micrometers.
The grooves and pits caused by fretting reduce the fatigue strength of the material because the grooves and pits act as stress concentrators. Furthermore, if the oxide layer that is constantly being removed by the fretting has a higher hardness than the base material, then the previously worn off oxide layer in between the two materials will act as an abrasive and increase the amount of fretting that occurs. The constant removal of a material's oxide layer allows for even more of the material to be oxidized. This type of corrosion is known as fretting corrosion.
There are several ways to reduce the risk of fretting. One way is to use a lubricant, which reduces the friction between the materials. Another way is to increase the smoothness of the material's surface, which reduces the friction caused by the materials in contact.