Deep Dive

Gear Wear

Gear wear in its many forms reduces efficiency, but is also detrimental to gear reliability.
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Gears
/ Wear
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Types of Gear Wear

Gears are subjected to various types of wear due to continuous contact and load transmission. Understanding these types of wear is crucial for diagnosing issues and implementing preventive measures to extend the lifespan of gears. Here are the primary types of wear that gears can experience:
abrasive wear in gears

Abrasive Wear

Abrasive wear occurs when hard particles or asperities on the gear surface or contaminants in the lubricant create a grinding effect, removing material from the gear teeth. This type of wear is essentially a mechanical scraping or cutting action where the harder material acts like sandpaper against the softer material. Abrasive wear can be either "two-body abrasive wear" (where the roughness is part of one of the actual surfaces in contact) or "three-body abrasive wear" (where loose particles move between the two surfaces).

Characteristics

  • Scratched or grooved surfaces.
  • Roughened tooth flanks.
  • Increased clearance between gear teeth

Causes

  • Contaminants such as dust, dirt, or metal particles in the lubricant.
  • Poor lubrication quality.
  • Rough initial surface finish.
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Adhesive Wear (Scuffing or Galling)

Adhesive wear, also known as scuffing or galling, occurs when two metal surfaces slide against each other under high pressure, causing material transfer from one surface to the other. This can result in localized welding and tearing. Adhesive wear is common in applications where high contact pressures and sliding motions are involved, like in gear teeth during power transmission.

Characteristics

  • Metal transfer between contacting surfaces.
  • Rough, torn, or smeared surfaces.
  • Micro-welds and subsequent tearing of material.

Causes

  • Insufficient lubrication leading to metal-to-metal contact.
  • High sliding velocities and loads.
  • Poor surface finish or material compatibility.
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Surface Fatigue Wear (Pitting & Spalling)

Surface fatigue wear results from repeated cyclic stress on the gear teeth surfaces, leading to the formation of cracks and subsequent material removal in the form of pits or larger flakes (spalling).

Characteristics

  • Small pits or craters on the gear tooth surface (pitting).
  • Larger flakes of material breaking off (spalling).
  • Rough and uneven surfaces.

Causes

  • High cyclic loads.
  • Inadequate lubrication.
  • Material defects or improper heat treatment.
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Corrosive Wear

Corrosive wear occurs when chemical reactions, typically oxidation or the presence of corrosive agents, degrade the gear material, leading to material loss and surface damage.

Characteristics

  • Rust or oxide formation on the gear surface.
  • Pitting or etching.
  • Weakened material structure.

Causes

  • Exposure to moisture, acids, or other corrosive substances.
  • Inadequate protection from environmental factors.
  • Contaminated lubricant.
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Fretting Wear

Fretting wear occurs at the contact surfaces of gears due to small oscillatory motions, which can lead to material fatigue and the formation of fine debris.

Characteristics

  • Fine, powdery debris at the contact surfaces.
  • Surface discoloration or corrosion.
  • Micro-cracks and surface damage.

Causes

  • Micro-movements between contacting surfaces.
  • Insufficient lubrication or lack of lubrication.
  • Relative motion under load.
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Impact Wear

Impact wear results from repeated impacts or shocks on the gear teeth, causing localized deformation and material removal.

Characteristics

  • Dented or deformed surfaces.
  • Chipped or broken gear teeth.
  • Surface cracks and fractures.

Causes

  • Sudden load changes or shocks.
  • Misalignment or improper installation.
  • Overloading of gears
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Polishing Wear

Polishing wear occurs when very fine abrasive particles smoothen the gear surface over time, leading to a polished appearance but also to a reduction in material.

Characteristics

  • Smooth, shiny surfaces.
  • Gradual material loss.
  • Reduced tooth profile accuracy.

Causes

  • Presence of fine abrasive particles in the lubricant.
  • Continuous light loading.
  • Overly aggressive initial surface finishing processes.
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Our GearCoat DLC provides extreme wear resistance, improving efficiency and elongating gear life.
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