Definition: Abrasion is the removal or displacement of surface material by hard, sharp particles or hard asperities.
Identification: Abrasion results in smooth, clean scratches or gouges in the direction of sliding. Wear steps are often present at the ends of teeth where contact is not made. Abrasion can cross the pitch line, and is maximum at the tips and roots of teeth.
Discussion: Abrasion is a wear process. Abrasion caused by hard loose particles is known as three body abrasion. Abrasion caused by hard asperities or embedded particles is known as two body abrasion.
Prevention: Remove abrasive particles. Drain and flush lube after first 50 hours of operation. Use tight seals and filtered breathers. Use surface hardened gears, smooth surfaces, and high viscosity lubrication.