Abrasive wear (granular wear; tridimensional wear) is the loss of material due to sliding in the presence of hard particles, when a hard surface or particle slides over another surface and removes material from that surface by cutting or furrowing action. Some degree of surface darkening occurs as a result of wear, with the degree of darkening varying depending on the coarseness and characteristics of the abrasive particles. As the surface is rotated, and possibly the material on the cage is worn away, the number of abrasive particles gradually increases, and eventually the wear enters into an accelerated process, leading to bearing failure.

Although the surface will generally have a certain degree of darkening, but when the abrasive particles are very fine when the polishing effect will occur, the formation of a very bright surface.

Adhesive wear

Adhesive wear is the transfer of material from one surface to another, accompanied by frictional heating and sometimes surface tempering or rehardening. This process creates localised stress concentrations and can lead to cracking or spalling in the contact zone.

In the case of inadequate lubrication, smearing (slipping, bonding, scratching, roughening) occurs when sliding occurs and the localised temperature rise due to friction causes the contact surfaces to adhere, resulting in material transfer.

Smearing often occurs between the rolling element and the raceway if the rolling element is underloaded and strongly accelerated when it re-enters the load zone. In the case of severe smearing, sticking occurs. In contrast to the gradual accumulation of abrasive wear, smearing often occurs suddenly.

Smearing also occurs on retaining surfaces and roller end faces due to insufficient lubrication. In the case of full complement rolling element (no cage) bearings, smearing also occurs at the contact between the rolling elements due to lubrication and rotational conditions.

If the bearing collar is mounted on the shaft or in the housing, the clamping force is insufficient to cause the collar to move relative to its support surface (creep), smearing (also known as gluing) can occur on the bearing ID surface, OD surface, or on the support surface of the shaft and housing bore. As there is a small difference between the diameters of the two parts, this results in a small difference in their circumferences. As a result, radial loads relative to the collar rotation bring the two parts into contact at a series of consecutive points, and the two contacting parts rotate relative to each other at small differential speeds. Ring relative to its support surface with a small speed difference made by this rolling motion is called ‘creep’.

Peristalsis occurs, the ring and support surface contact area of the rough peaks are rolled, so that the surface of the ring presents a bright appearance. In the creep process of rolling mill often occurs, but not always accompanied by the ring and bearing surface contact sliding, and therefore can also see other damage, such as abrasion marks, micro-motion abrasion and wear. Under certain load bearing conditions, when the excess between the collar and the bearing surface is not large enough, micro-abrasion is dominant.

In addition, when a clearance fit is used in the radial direction, creep occurs between the end face of the collar and its axial nei ghbours, which can lead to transverse thermal cracks in severe cases, eventually causing the collar to crack.