Wear (erosion): causes, mechanisms, and prevention in solids
Wear is the progressive loss of material from solid surfaces caused by mechanical action. This article explains primary wear mechanisms, history, testing, industrial examples, and strategies to reduce damage.
Wear is the progressive loss or removal of material from a solid surface caused by relative motion and mechanical interaction with another body. Studied within materials science and the interdisciplinary field of tribology, wear is not a single phenomenon but a set of mechanisms that produce surface damage and debris over time.
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Mechanisms and principal types
Practitioners commonly group wear into a few principal categories based on how material is detached. The most widely cited classes are:
- Adhesive wear — material transfers locally when asperities weld together under load and then separate.
- Abrasive wear — harder particles or protuberances plow or cut material from a softer surface; a classic example involves grinding with an abrasive grit (abrasion).
- Surface fatigue — repeated stresses cause crack initiation and spallation beneath the contact area, common in rolling elements.
- Corrosive/tribochemical wear — chemical or electrochemical reactions weaken the surface and accelerate mechanical removal.
Other important modes include erosive wear from high-velocity particles and fretting, a small-amplitude oscillatory wear. These mechanisms often act together rather than in isolation.
History and study
Systematic attention to wear expanded in the 20th century as machines and engines demanded reliable moving parts. Landmark technical surveys and national studies highlighted the economic impact of friction and wear and promoted coordinated research into lubrication, surface engineering and testing methods. Modern wear science combines laboratory experiments, modeling and failure analysis to understand how contact pressure, sliding speed, material hardness and environment influence damage.
Practical examples and importance
Wear affects nearly every engineered contact: bearings, gears, cutting tools, seals, railroad wheels, and medical implants all rely on controlled wear behaviour to function safely and predictably. In some systems wear is fatal (component seizure, leakage), while in others it is expected and managed (disc brake pads, sacrificial coatings).
Testing, measurement and mitigation
Engineers use standardized lab tests such as pin-on-disk, ball-on-flat and sliding rigs to compare materials and lubricants and to determine wear rates and wear coefficients. Common strategies to reduce wear include:
- Selecting harder or tougher materials and engineered alloys
- Applying surface treatments and coatings (carburizing, nitriding, PVD/CVD films)
- Designing to reduce contact stresses and avoid sharp edges
- Using lubrication or solid films to separate surfaces
- Controlling the environment to limit corrosive attack
Understanding wear requires considering mechanics, materials and chemistry together. Detecting early wear, analyzing debris, and choosing the right combination of materials, surface engineering and maintenance are central to extending service life and reducing failure risk. For further technical background see sources on material removal and surface damage.
Influencing variables
- Basic body (material, shape, surface)
- Intermediate (type, particle size, etc.)
- Counterbody (material, shape, surface)
- Load (magnitude, time course)
- Type of movement (gliding, rolling, pushing)
- surrounding atmosphere (e.g. air, inert gas, vacuum)
- Temperature (altitude, time course)
Wear is always a system property, not a property of the components involved: There are always (at least) two components in interaction, often still an intermediate medium (fluid). In contrast, material fatigue and chemical ageing are also possible without the involvement of a second component.
Mechanisms
Wear is mainly determined by four different wear mechanisms:
Adhesive wear
Adhesive wear occurs in the event of insufficient lubrication. If components in contact lie firmly on top of each other under high surface pressure, the contact surfaces adhere to each other as a result of adhesion. During sliding, particles of the surface layer are sheared off. This results in holes and scale-like material particles, which often adhere to the sliding surface of the harder partner. This wear mechanism is called adhesive wear.
Example:
Protective oxidation layers are broken through as a result of adhesion due to the high local pressure at individual surface roughness hills. This results in local micro cold welding. Due to the strain hardening, the material does not subsequently
crack in the area between the two welds (fusion zone), but in the adjacent areas.
Abrasive wear
When hard particles of a lubricant or roughness peaks of one of the friction partners penetrate the surface layer, scoring and micro-chipping occur. This wear is referred to as abrasive wear, furrow wear or erosive wear - the latter can also be caused by fluids. The material loss caused by abrasion is called wear.
To prevent abrasive wear, lubricants should be monitored and replaced if necessary. In principle, abrasive wear can already be prevented during the design of a tribological system. Instead of metallic pairings, metal-plastic or metal-ceramic pairings should be preferred. As a general rule, in the case of metallic pairings, a favourable ratio (e.g. hard carbides in a tough intermediate material) between strength and toughness should be aimed for.
Abrasive wear plays a special role in systems in which media are conveyed that contain angular, hard particles. For example, abrasive wear plays a role in pipelines and pumps through which water with suspended solids (sand), plaster and concrete (aggregates) or filled plastic masses (fillers) are to be conveyed, for example in potting systems. In these cases, abrasive wear is a major cause of the shortening of the service life of components through which water flows.
Abrasive wear can be determined with a mechanical test method using the so-called Taber abrasor according to ISO 9352, ASTM D 1044 or DIN EN standard 438 - 2.6. In this process, wheels equipped with abrasive paper are pressed against the rotating surface of the test specimens with a defined pressure. The measured variable is usually the loss of mass of the specimen after a certain number of revolutions.
In the case where abrasive solids are suspended in fluids and cause wear, the term hydroabrasion is used.
Surface disruption
Surface disruption is a wear mechanism caused by alternating or swelling mechanical stresses. The result is a disruption of the surface, i.e. microcracks develop and grow in the material layers near the surface. Surface disruption occurs, for example, in rolling bearings due to constant overrolling. This wear, also called rolling wear, causes pitting. Since tensile stresses in the surface promote surface disruption, compressive stresses can be introduced into the surface as a countermeasure. Suitable processes are nitriding, oxidizing or shot peening of the surfaces.
Tribooxidation
The formation of intermediate layers, e.g. oxide layers, as a result of chemical reaction and their destruction by movement of the components is called tribo-oxidation or reaction layer wear. It almost always occurs together with adhesive wear. This wear mechanism, which occurs as a result of chemical reaction and mechanical destruction of the reaction layer, is a tribochemical reaction. An example of tribo-oxidation is fretting corrosion.
Questions and answers
Q: What is wear in materials science?
A: Wear in materials science is the erosion of material from a solid surface by the action of another solid.
Q: What discipline does the study of the processes of wear fall under?
A: The study of the processes of wear falls under the discipline of tribology.
Q: How many principal wear processes are there?
A: There are four principal wear processes.
Q: What are the four principal wear processes?
A: The four principal wear processes are abrasion, adhesion, surface fatigue, and erosion.
Q: What is abrasion in wear processes?
A: Abrasion is a wear process where the material is removed due to mechanical action, such as rubbing or scraping.
Q: What is adhesion in wear processes?
A: Adhesion is a wear process where material is transferred from one surface to another due to friction.
Q: What is surface fatigue in wear processes?
A: Surface fatigue is a wear process where repeated cycles of loading and unloading cause cracks to form on the surface of a material, leading to material loss.
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AlegsaOnline.com Wear (erosion): causes, mechanisms, and prevention in solids Leandro Alegsa
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