In the world of industrial machinery, bearings are the silent workhorses that keep operations running smoothly. When they fail, production halts, costs skyrocket, and downtime ensues. For maintenance engineers and plant managers, a failed bearing is not just a broken part—it is a forensic clue. The specific patterns of damage on a bearing raceway tell a detailed story about the health of the machine, the quality of the lubrication, and the precision of the installation.
Understanding the distinct differences between Scoring, Spalling, and Brinelling is essential for Root Cause Analysis (RCA). By decoding these failure modes, you can move beyond simple replacement and address the underlying mechanical issues, ensuring longer asset life and improved reliability.
The Importance of Visual Diagnosis
According to international standards like ISO 15243, rolling bearing damages are classified into specific categories based on their visual characteristics. Identifying these early can prevent catastrophic failure. While a bearing might look “worn out” to the untrained eye, a specialist can distinguish between a lubrication failure and a load issue simply by looking at the surface texture.
Below is a high-level comparison of the three most common failure modes to help you identify them quickly.
Comparison of Common Bearing Failures
| Failure Mode | Visual Characteristic | Primary Root Cause |
|---|---|---|
| Spalling | Flaking or pitting of the raceway surface; material peels away in layers. | Material Fatigue (Cyclic Stress) |
| Scoring | Longitudinal scratches or grooves in the direction of rotation; rough surface. | Lubrication Failure / Contamination |
| Brinelling | Permanent indentations (dents) in the raceway, often spaced at rolling element intervals. | Static Overload or Impact Shock |
Spalling: The Sign of Fatigue
Spalling is the classic sign of rolling contact fatigue. It is often what engineers expect to see when a bearing reaches the end of its calculated L10 life. However, premature spalling indicates a more serious problem.
What it looks like:
Spalling begins as microscopic cracks below the surface (subsurface origin) or at the surface (surface origin). As the stress cycles continue, these cracks propagate until small chunks of metal break loose. This leaves behind irregular, flake-like cavities or pits on the raceway.
Spalling begins as microscopic cracks below the surface (subsurface origin) or at the surface (surface origin). As the stress cycles continue, these cracks propagate until small chunks of metal break loose. This leaves behind irregular, flake-like cavities or pits on the raceway.
What it tells you:
- Normal End of Life: If the bearing has run for its expected service life, spalling is simply the result of metal fatigue.
- Excessive Load: If spalling occurs early, the bearing may be under a heavier load than designed. This could be due to incorrect selection or unexpected operational forces.
- Misalignment: If the spalling is not uniform across the raceway (e.g., heavier on one side), it indicates the shaft and housing are not aligned, creating a “point load.”
- Improper Clearance: Insufficient internal clearance can increase stress, accelerating fatigue.
Scoring: The Evidence of Friction and Contamination
Unlike spalling, which is a fatigue phenomenon, scoring is a tribological failure. It is often referred to as “scuffing” or “galling” and is a clear indicator that the protective lubricant film has been compromised.
What it looks like:
Scoring appears as scratches, grooves, or a rough, torn surface texture on the raceway or rolling elements. These marks usually align with the direction of motion. In severe cases, the heat generated can cause discoloration (blueing) of the steel.
Scoring appears as scratches, grooves, or a rough, torn surface texture on the raceway or rolling elements. These marks usually align with the direction of motion. In severe cases, the heat generated can cause discoloration (blueing) of the steel.
What it tells you:
- Lubrication Failure: The oil or grease film was too thin to separate the metal surfaces. This results in metal-to-metal contact, causing adhesion and tearing.
- Contamination (Abrasive Wear): Hard particles—such as dust, dirt, or metal shavings—have entered the bearing. These particles act like cutting tools, plowing through the raceway surface.
- High Speed/Temperature: Extreme operating conditions can degrade the lubricant viscosity, leading to a breakdown of the oil film and subsequent scoring.
Actionable Tip: If you see scoring, check your seals immediately. In many cases, the ingress of water or abrasive particles is the silent killer of bearings.
Brinelling: The Mark of Impact
Brinelling is distinct because it is a plastic deformation rather than a removal of material. It represents a physical change in the geometry of the bearing raceway caused by force.
What it looks like:
You will see distinct, permanent indentations (dents) in the raceway.
You will see distinct, permanent indentations (dents) in the raceway.
- True Brinelling: Caused by a heavy static load or a sharp impact while the bearing is stationary. The indentations are spaced exactly at the distance between the rolling elements.
- False Brinelling: Caused by vibration while the machine is not rotating (e.g., during transport). This creates wear marks that look like corrosion but are actually fretting damage.
What it tells you:
- Installation Error: The most common cause of true brinelling is improper installation. If a hammer is used to force a bearing onto a shaft, or if force is applied through the wrong ring, the rolling elements can dent the raceway.
- Shock Loads: The machine may be experiencing impacts (e.g., a crusher or hammer mill) that exceed the yield strength of the bearing steel.
- Transport Damage: If false brinelling is present, it suggests the bearing was not secured properly during shipping or the equipment was subjected to vibration while idle.
Summary of Root Causes and Solutions
To assist in your diagnosis, we have compiled a detailed breakdown of these failure modes, their specific triggers, and the recommended corrective actions.
| Failure Mode | Specific Indicators | Likely Causes | Recommended Solutions |
|---|---|---|---|
| Spalling | Irregular flaking, subsurface cracks, audible noise/vibration. | 1. Excessive load. 2. Misalignment. 3. Fatigue limit reached. |
1. Re-evaluate load calculations. 2. Check shaft/housing alignment. 3. Select a bearing with higher dynamic load rating. |
| Scoring | Longitudinal scratches, surface roughness, discoloration from heat. | 1. Insufficient lubrication. 2. Abrasive particles (dirt/water). 3. Slip/creep. |
1. Increase lubricant viscosity or quantity. 2. Improve sealing (e.g., labyrinth seals). 3. Check fit tolerances to prevent creep. |
| Brinelling | Regularly spaced dents (True) or axial wear marks (False). | 1. Hammering during installation. 2. Static shock loads. 3. Vibration during transport. |
1. Use induction heaters or hydraulic tools for mounting. 2. Redesign to absorb shock loads. 3. Lock bearings during transport. |
Conclusion: Turning Failure into Insight
A failed bearing is a missed opportunity if it is simply thrown away. By examining the raceways for Spalling, Scoring, or Brinelling, you gain access to a historical record of your machine’s operation.
- Spalling asks you to check your loads and alignment.
- Scoring demands you inspect your lubrication and sealing.
- Brinelling warns you to improve your handling and installation practices.
By integrating these visual inspections into your maintenance routine, you transform reactive repairs into proactive reliability strategies. Remember, the goal is not just to replace the part, but to ensure the machine runs better than it did before.
FAQ: Understanding Bearing Failure
Here are answers to common questions regarding bearing diagnostics and failure modes.
What is the difference between Spalling and Brinelling?
Spalling is a fatigue failure where material flakes off the raceway due to cyclic stress. Brinelling is a plastic deformation where permanent dents are pressed into the raceway due to static overload or impact.
What causes Scoring on a bearing?
Scoring is primarily caused by lubrication failure or contamination. It occurs when the oil film is too thin to separate metal surfaces, or when hard particles (like dirt) scratch the raceway.
Can a bearing be reused if it has Brinelling?
No. Brinelling creates permanent indentations that alter the bearing’s geometry. This will lead to excessive vibration, noise, and rapid secondary damage if the bearing is put back into service.
How can I prevent False Brinelling?
False brinelling is caused by vibration while the machine is stationary (e.g., during transport). To prevent it, lock the bearings to prevent movement or use proper packaging to isolate the equipment from external vibration.
Does Spalling always mean the bearing reached the end of its life?
Not necessarily. While spalling is the expected end-of-life failure mode, if it occurs prematurely, it indicates issues such as excessive load, misalignment, or insufficient internal clearance
Post time: May-29-2026