White etching cracks (brittle flaking and axial cracks)
Early cracks in the steel that standard life calculations do not predict. Urgency
The steel could not carry the stress: broken in one event, or cracked progressively.
What white etching cracks (brittle flaking and axial cracks) looks like
- Flaking that is brittle and angular, often early, with cracks running below the surface
- Axial cracks in the inner ring, or cracks that follow the raceway
- Only a metallurgical section shows the white-etching network under the surface
Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.
How white etching cracks (brittle flaking and axial cracks) develops
Under high stress and slip, the steel can transform into a hard, brittle white-etching structure that cracks. The networks are linked to brittle flaking and probably axial cracking. Research is still under way, but the picture so far points to a mechanical root cause, with high stress and slip. Gearbox and wind-turbine bearings are the best-known cases.
How fast it progresses: The cracks can start early in life and run fast. Normal vibration trending may give little warning, so inspect in service.
Causes of white etching cracks (brittle flaking and axial cracks)
Operating conditions
- Rapid load changes, high loads and slip conditions
- Transient and shock loading in the drivetrain
Lubrication
- Thin films, starvation, and conditions that allow sliding
Environment & sealing
- Stray current or hydrogen in the steel are among the other suspects under study
Bearing selection
- A bearing that is lightly loaded and likely to skid
How to confirm it is white etching cracks (brittle flaking and axial cracks)
- Only a lab can confirm it: cut and etch a section of the failed ring
- Look at the history: a failure far inside the calculated life with brittle flaking and cracks
- Rule out the common causes first (lubrication, contamination, current, fits)
How to fix and prevent white etching cracks (brittle flaking and axial cracks)
- Rule out the standard causes first, then ask the bearing maker for a metallurgical analysis
- Avoid skid and slip: keep a minimum load, avoid rapid load reversals, and pick the right lubricant
- Consider the maker’s special treated or coated bearings for the application
Easily confused with
- Subsurface-initiated fatigue: Ordinary fatigue spalls start later in life and are not brittle.
- Fatigue fracture: A fatigue fracture goes through the ring cross-section.
Catching white etching cracks (brittle flaking and axial cracks) early
High-frequency envelope analysis and oil debris monitoring give the earliest warning. Trend them, and inspect with a borescope on schedule.
Other fracture modes
Questions about white etching cracks (brittle flaking and axial cracks)
What causes white etching cracks (brittle flaking and axial cracks) in a bearing?
Rapid load changes, high loads and slip conditions. Thin films, starvation, and conditions that allow sliding. Stray current or hydrogen in the steel are among the other suspects under study.
How do you fix or prevent white etching cracks (brittle flaking and axial cracks)?
Rule out the standard causes first, then ask the bearing maker for a metallurgical analysis. Avoid skid and slip: keep a minimum load, avoid rapid load reversals, and pick the right lubricant. Consider the maker’s special treated or coated bearings for the application.
What does white etching cracks (brittle flaking and axial cracks) look like?
Flaking that is brittle and angular, often early, with cracks running below the surface. Axial cracks in the inner ring, or cracks that follow the raceway.