Rolling Contact Fatigue

Rolling contact fatigue occurs when repeated rolling or sliding contact between surfaces generates high localized stresses below the surface. Over time, these stresses create subsurface cracks that eventually propagate to the surface, causing spalling, pitting, or flaking. This failure mode is common in bearings, gears, and raceways that experience continuous rolling motion under load.

Fretting wear, by contrast, is driven by surface-level micro-movements under load, causing adhesion, pitting, and oxidation where parts experience small oscillations without full rolling motion.

While both mechanisms can lead to surface damage and eventual failure, rolling contact fatigue originates below the surface, while fretting wear is a surface-driven phenomenon.

Rolling contact fatigue (RCF) occurs when surfaces in repeated rolling contact—such as those in bearings, gears, and rail-wheel systems—undergo stress cycles that lead to subsurface crack initiation and eventual spalling or flaking.

Key Causes of RCF:

1. Cyclic Loading: Continuous rolling creates alternating stresses below the surface, which gradually cause crack growth over time.
2. Heavy Loads: Higher contact pressures amplify stress levels and accelerate fatigue damage.
3. Material Imperfections: Inclusions, voids, or microstructural defects can trigger early crack formation.
4. Surface Condition: Roughness, scratches, or dents serve as stress risers, promoting crack propagation.
5. Insufficient Lubrication: Poor lubrication increases friction and surface stress, raising the risk of fatigue damage.
6. Contaminants: Dirt or metal particles entering the rolling contact zone can create micro-pits and initiate failures.

How to Prevent RCF:

• Use premium materials with high fatigue resistance.
• Apply surface hardening processes like carburizing, nitriding, or wear-resistant coatings such as Armoloy TDC.
• Maintain effective lubrication to reduce contact stress and minimize wear.
• Monitor and clean systems regularly to remove contamination and detect early-stage damage.

Targeting these stress and surface conditions can dramatically increase the service life of critical components exposed to rolling fatigue.