Abrasive and Adhesive Wear

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Abrasive wear happens when the particular material is being removed from one surface, by another harder material. In results, hard particles of the debris between the 2 surfaces are formed. The terms scratching, gouging or scoring are used depending on the degree of abrasive wear. In simple words, the harder material scratches the softer material.

There are 2 condition in which abrasive wear occurs. The 2 body abrasion and 3 body abrasion. In the former, the harder surface rubs the other. Examples of these include mechanical grinding, cutting and machining. The latter involves a third body. This third body is generally a small particle of abrasive between the 2 softer rubbing surfaces.

Microscopically, abrasive wear causes asperities of the harder surface to press into the softer surface, with plastic flow of the softer surface formed around the harder asperities. These result in ‘microploughing’ and ‘microcracking’ where tangential motion is imposed.

This abrasive wear can be reduced by applying ‘hydrodynamic’ or ‘elastohydrodynamic’ lubricants at various film thickness. This separates the surfaces and wash out any contaminant particles in between. Using the correct coating material and various thermally sprayed techniques greatly benefits the resistance to abrasive wear.

Adhesive wear is often referred to ‘scuffing’. This happens when adhesive junctions that are newly formed lock together and as 2 surfaces slide across each other under pressure. When normal pressure is being applied, local pressure at the asperities become extremely high. Often times, the yield stress is exceeded. Then these asperities deform plastically until the real area of contact has increased sufficiently to support the earlier, applied load.

If no lubricants are used, asperities are to be cold welded together. Otherwise, junctions will shear and form new junctions. This said wear mechanism not only destroys the sliding surfaces, but permits the generation of wear particles. In turn, these wear particles lead to cavitation that can cause component failure.

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