Adhesive Wear

Adhesive wear can lead to several types of failures, significantly impacting the performance and longevity of mechanical components. Here are the common failures associated with adhesive wear:

1. Galling: This occurs when severe adhesive wear causes the surfaces to seize and weld together. It results in significant material transfer and surface damage, leading to operational failure.
2. Scoring: Visible grooves or scratches appear on the surface due to repeated adhesive contact. This type of failure can reduce the efficiency of sliding components and increase friction.
3. Seizing: The surfaces lock together due to strong adhesive forces, often leading to a sudden and complete failure of the component. This can halt machinery operations and cause extensive damage.
4. Material Transfer: Particles from one surface transfer to another, leading to uneven wear and potential imbalance in rotating machinery. This can cause vibrations and reduced precision in operations.
5. Surface Fatigue: Repeated adhesive contact can lead to surface fatigue, characterized by the initiation and growth of cracks. Over time, this results in the spalling or flaking of material.
6. Pitting: Small pits or craters form on the surface due to localized adhesive failure. This can compromise the structural integrity of components and lead to premature failure.

Preventing adhesive wear involves selecting appropriate materials, applying surface coatings, using effective lubricants, and ensuring proper maintenance practices to reduce direct contact and friction between surfaces.

Adhesive wear occurs when two surfaces slide against each other and microscopic material fragments stick, tear, and transfer between them. It often appears as galling, scoring, or material buildup, especially in high-friction metal-to-metal contact.
Cohesive wear, on the other hand, involves the material failing from within — not from surface-to-surface interaction. Internal stresses, fatigue, or thermal cycling can cause cracks or spalling to form and release fragments from the substrate itself.
The key difference is this:

• Adhesive wear starts between surfaces due to adhesion.
• Cohesive wear starts within the material due to internal weakness.

Understanding the mechanism helps determine the right countermeasure — whether it’s reducing surface contact with coatings or improving the material’s structural resilience.

Adhesive wear happens when metal surfaces in contact stick at microscopic points under pressure. As these surfaces slide, small fragments tear away, causing material transfer between parts. It’s common in gears, bearings, and components with sliding metal-to-metal contact.

Abrasive wear occurs when a harder material or foreign particles cut into the surface, removing material directly. This is typical in cutting, grinding, or contaminated environments like mining and drilling.

While both involve surface damage, adhesive wear is driven by material transfer, while abrasive wear removes material through cutting or plowing action.

Adhesion is explained by several mechanisms that describe how surfaces bond:

• Mechanical Interlocking: Adhesive fills surface irregularities, locking into microscopic pores to create a physical bond.
• Electrostatic Attraction: Oppositely charged surfaces generate electrostatic forces that help hold materials together.
• Diffusion: Molecules from the adhesive and substrate intermix at the interface, forming bonds through molecular entanglement.
• Chemical Bonding: Strong covalent, ionic, or hydrogen bonds form between the adhesive and substrate at the molecular level.

In real-world applications, multiple adhesion mechanisms often work together to create durable, reliable bonds.