Wear

WearIntroduction about the wear

Types of wear

Adhesive wear

ContGenerally, adhesive wear occurs when two bodies slide over or are pressed into each other, which promote material transfer. This can be described as plastic deformation of very small fragments within the surface layers. Theasperitiesor microscopic high points orsurface roughnessfound on each surface, define the severity on how fragments of oxides are pulled off and adds to the other surface, partly due to strong adhesive forces between atoms.Adhesive wear is a common fault factor in industrial applications such assheet metal forming(SMF) and commonly encountered in conjunction with lubricant failures and are often referred to as welding wear or galling due to the exhibited surface characteristics, phase transition and plastic flow followed by cooling.SEM micrograph of adhesive wear (transferred materials) on 52100 steel sample sliding against Al alloy. (Yellow arrow indicate sliding direction)

Archards theory of sliding wear

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Abrasive wearAbrasive wear occurs when a hard rough surface slides across a softer surface.ASTM International (formerly American Society for Testing and Materials) defines it as the loss of material due to hard particles or hard protuberances that are forced against and move along a solid surface.

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Abrasive wear

Abrasive wear occurs when a harder material is rubbing against a softer material.

WhereV = wear volume, L = sliding velocityN = applied load, s = surface strengthK = wear coefficient

Two body wear

Three body wear

Corrosive wear

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Fatigue wear

FRETTINGFretting refers to wear and sometimes corrosion damage at the asperities of contact surfaces. This damage is induced under load and in the presence of repeated relative surface motion, as induced for example by vibration.Fatigue and Fracture defines fretting as: "A special wear process that occurs at the contact area between two materials under load and subject to minute relative motion by vibration or some other force.The contact movement causes mechanical wear and material transfer at the surface, often followed by oxidation of both the metallic debris and the freshly exposed metallic surfaces. Because the oxidized debris is usually much harder than the surfaces from which it came, it often acts as an abrasive agent that increases the rate of both fretting and a mechanical wear called false brinelling.Delamination theory of wear

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Delamination wear

A wear process where a material loss from the surface by forces of another surface acting on it in a sliding motion in the form of thin sheets.

Mechanisms of delamination wear Plastic deformation of the surfaceCracks are nucleated below the surfaceCrack propagation from these nucleated cracks and joining with neighbouring one After separation from the surface, laminates form wear debris

Wear testing methods

Erosive wear Testing MethodsIn jet impingement method