Wear is the unwanted change of the surface of utensils by draw running of small particles due to mechanical causes, e.g. friction, with surfaces sliding one on the other.

It arises for example at camps, at clutches, transmissions, nozzles and brakes. Wear is one of the principal reasons for construction unit damage and the associated loss of machines and devices. The decrease of wear is around a substantial possibility increasing the life span from machines and devices to and of saving thus costs and raw materials. On the other hand one tries not to limit that wear which can be avoided on construction units which can be exchanged simply which one summarizes under the term wearing part.

Definition according to DIN 50320 (standard 1997 were withdrawn): Wear is caused the progressive waste from the surface of a firm body (base), by mechanical causes, i.e. contact and relative motion of a firm, liquid or gaseous

The field of activity, which is concerned with friction and wear, is called tribology.

Measured variables on wear

• Base (material, form, surface)
• Zwischenstoff (kind, particle size among other things)
• (material, form, surface)
• Load (size of, course)
• Kind of the movement (, roles, pushing slide)
• Surrounding atmosphere (e.g. air, inert gas, vacuum)
• Temperature (height, course)

Wear is always a system property, not a characteristic of the components involved.

Verschleissmechanismen

Wear is determined mainly by four different verschleissmechanismen:

wear

If affecting construction units lie on top of one another themselves firmly, then the contact surfaces cling together due to adhesion. When sliding particles are then cut. Develop in such a way holes and shed-like material particles, which remain often sticking to the sliding surface of the harder partner. One calls this verschleissmechanismus wear or wear arises with lubrication lacking.

shit develops, if construction units without Zwischenstoff are moved against each other or the Zwischenstoff by high surface pressure are displaced. With wear outer zone particles are cut.

Abrasiver wear

If hard particles of a lubricant or roughness points penetrate one the friction partner into the outer zone, then it comes to cutting and micro machine cutting. One calls this wear abrasiven wear or Furchverschleiss.

For the avoidance of abrasivem wear lubricants should be supervised and renewed if necessary. In principle can be prevented with the construction of a tribologischen system to abrasivem wear. Instead of metallic mating metal plastic or ceramel mating should be preferred. In principle it applies that with metallic mating a favorable relationship (e.g. hard carbide in tough Zwischenstoff) between firmness and tenacity should be aimed at.

A special role plays abrasiver wear contained in plants, in which media are promoted, the sharp-edged, hard particles. For example abrasiver wear in pipings and pumps, by the water with suspended matters (sand), finery and concrete (aggregates) plays a role or filled plastic masses (fillers), approximately to capping plants, to promote are. In these cases abrasiver wear is a substantial cause for the of the life span of durchflossenen construction units.

Abrasiver wear can be determined with a mechanical testing method over the Taber Abraser in such a way specified according to ISO 9352, ASTM D 1044 or DIN EN standard 438 - 2,6. Here with sandpaper provided wheels with a defined pressure are pressed against the rotary surface of the sample test specimens. Measured variable is usually the mass loss of the sample test specimen after a certain number of revolutions.

Abrasiver wear is a machine cutting in the microbe realm.

is a verschleissmechanismus, which is caused by changing mechanical stresses. Consequence is a disorder of the surface, i.e. and grows microcrack in the material layers near the surface develops. arises for example in antifriction bearings by constant rolling over. This wear, also rolling wear mentioned, lets develop or Pittings. Since tensions promote the in the surface, compression stresses can be brought into the surface as counter measure. Suitable procedures are nitrating, oxidizing or shot-peening of the surfaces

Tribooxidation

And their destruction by movement of the construction units one calls the education of intermediate layers, e.g. oxide coatings, due to chemical reaction Tribooxidation or reaction layer wear. It nearly always arises together with wear. This verschleissmechanismus, which develops due to chemical reaction and mechanical destruction of the reaction layer, is a tribochemische reaction. An example of Tribooxidation is fretting corrosion.

See also

• Corrosion
• Moral wear
• VDI 3822 sheets 5: "“Damage by tribologische demands"”

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