Fretting

If the debris and/or surface subsequently undergo chemical reaction, i.e., mainly oxidation, the mechanism is termed fretting corrosion.

Fretting damage in steel can be identified by the presence of a pitted surface and fine 'red' iron oxide dust resembling cocoa powder.

The particles are much harder than the steel surfaces in contact, so abrasive wear is inevitable; however, particulates are not required to initiate fret.

Fretting in Aluminium causes black debris to be present in the contact area due to the fine oxide particles.

Fretting examples include wear of drive splines on driveshafts, wheels at the lug bolt interface, and cylinder head gaskets subject to differentials in thermal expansion coefficients.

The relatively soft and thin gold plating used on most high quality electrical connectors is quickly worn through exposing the underlying alloy metals and with fretting debris the impedance rapidly increases.

Somewhat counterintuitively, high contact forces on the mated connector pair (thought to help lower impedance and increase reliability) can actually make the rate of fretting even worse.

If the bearing movement is limited to small motions the damage caused may be called fretting or false brinelling depending on mechanism encountered.

[14] However, softer materials such as polymers can show the opposite effect when they capture hard debris which becomes embedded in their bearing surfaces.