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Adhesion arises from friction between two surfaces, for example, when metal surfaces move against each other under pressure. Microscopic material transfer can lead to chipping, micro-welding, and irreparable damage, especially if unsuitable material pairings are used.

Abrasion describes the loss of material due to hard particles or rough contact surfaces. The resulting wear can vary greatly depending on the abrasion resistance of the material and the lubrication.

Cavitation occurs when local pressure drops develop in liquids, causing vapor bubbles to form and subsequently implode. The resulting micro-jets and shock waves attack the surface of a component at specific points, causing material loss through erosion. Components in pumps, turbines, or valves, which are exposed to high flow velocities and fluctuating pressure conditions, are particularly vulnerable.

Surface fatigue results from cyclical stresses, such as pressure fluctuations or vibrations. It leads to cracking within the base material and promotes spalling.

Tribo-oxidation occurs when friction and temperature stimulate chemical reactions. This process forms oxide layers that can provide protection but are also susceptible to wear. Careful material selection is essential to address this interaction, especially in high-temperature applications.

Wear refers to the progressive loss of material on the surface of a solid body, caused by mechanical, thermal, or chemical influences resulting from relative movement between contacting surfaces. It leads to a change in material properties and can impair the functionality of components. The most important wear mechanisms are abrasion, adhesion, surface fatigue, and tribo-oxidation, each caused by different physical and chemical processes.