Which bearing wear is primarily caused by impact loads?

• A. Spalling
• B. Scoring
• C. Brinelling
• D. Discoloration

Answer: (C)

When a bearing faces a sudden, high load or a heavy shock, the contact surfaces can yield locally and form permanent indentations. This plastic deformation under impact creates small pits on the raceways or balls known as brinelling. Those indentations degrade the smooth rolling of the bearing and can become initiation sites for fatigue cracks, leading to premature failure even if lubrication is adequate.

This is distinct from spalling, which is surface flaking caused by rolling contact fatigue from repeated cycles—not a single impact event. Scoring involves grooves or scratches from abrasive wear or metal-to-metal contact, typically due to contamination or insufficient lubrication, rather than an impact-induced deformation. Discoloration signals overheating or corrosion rather than the mechanical indentation associated with brinelling.

So the wear most associated with impact loads is brinelling.