Bearing failure modes: identify spalling, brinelling, false brinelling and the rest

Updated 2026-10-04

Why identification beats replacement

A removed bearing is a failure report. When the same model — 6205-2RS in a motor, 32208 in a hub, 22210 on a conveyor — fails repeatedly, the steel was not the problem; an unresolved load, environment or mounting condition was. Read the damage pattern before fitting the replacement.

First, separate two situations:

• End of service life — after long running near or beyond the rated L10, damage is broadly distributed and the bearing has honestly worn out.
• Premature failure — early damage concentrated in a pattern. Each pattern below maps to a specific cause and correction.

The damage-pattern table

1. Rolling-contact fatigue — spalling / flaking

• Looks like: pitted, scaly patches of metal breaking out of the raceway or rolling elements, starting below the surface and growing into craters with sharp edges.
• Meaning: the terminal mechanism of every bearing after enough load cycles; broadly distributed spalling after full service is normal.
• Investigate when: it occurs early or is localised — contamination dents, edge loading or electrical erosion often act as initiation sites.
• Correction: re-rate the load; for localised early spalling, find the initiating cause in the sections below.

2. Brinelling — true indentation

• Looks like: distinct round or oval depressions at rolling-element spacing; you can feel them with a fingernail.
• Cause: static overload, a shock while stationary, or driving the bearing home through the rolling elements during mounting.
• Correction: mount by heating the inner ring (max 120 °C); eliminate shock loads; if equipment rests on the bearing under load, relieve it during transport.

3. False brinelling — vibration wear while stationary

• Looks like: polished or rust-coloured shallow recesses at element positions, often with fine dark debris; less sharply indented than true brinelling.
• Cause: minute reciprocating sliding between elements and races under vibration while the bearing is not rotating — standby pumps, equipment on trucks, idling conveyors.
• Correction: isolate vibration, rotate standby equipment on a schedule, or specify a bearing/grease combination intended for fretting conditions.

4. Fretting corrosion on the fits

• Looks like: reddish-brown or black oxide powder and shiny worn patches on the bore or outside diameter where the ring met the shaft or housing.
• Cause: a loose ring creeping on its seat — wrong fit for which ring rotates, or a shaft worn undersize.
• Correction: assign fits correctly (interference on the rotating ring), restore shaft dimensions, and recheck clearance choice — interference and heat consume internal clearance.

5. Electrical pitting — fluting / washboard

• Looks like: fine regular grooves across the raceway, dark frosted areas, or — under magnification — evenly spaced arc marks.
• Cause: shaft current discharging through the contact, most often in VFD-driven motors.
• Correction: shaft grounding ring, insulated or hybrid bearing, or conductive grease; a standard replacement fails the same way, usually faster.

6. Smearing and skidding damage

• Looks like: torn, glazed or transferred metal on raceways and roller ends; sometimes blued steel from heat.
• Cause: rolling elements sliding instead of rolling under light load, rapid acceleration, or marginal/aged lubrication.
• Correction: correct preload where appropriate, verify lubricant viscosity at operating temperature, and avoid sustained running under too light a load for the bearing type.

7. Contamination — abrasive wear and particle dents

• Looks like: dull, honed or scratched raceways, wear flats on elements, and random small dents from hard particles; grease looks gritty.
• Cause: dirt entering during mounting or through failing seals, and contaminated lubricant.
• Correction: clean assembly practice, intact seals, filtered lubricant; in washdown or grit duty, move from shields to contact seals — see 6205 vs 6205-2RS.

8. Edge loading and misalignment

• Looks like: spalling concentrated along one edge of the raceway, often on the same side in both failed bearings from a position.
• Cause: shaft deflection, housing misalignment, or a non-self-aligning bearing in an imperfect seat.
• Correction: align the seats, stiffen the shaft, or select a self-aligning type (self-aligning ball, spherical roller or CARB) for structural misalignment.

9. Seal and grease ageing

• Looks like: hardened, cracked or shrunken seal lips; grease that is dry, caked, separated or darkened; corrosion inside a nominally sealed bearing.
• Cause: the sealed-for-life grease or elastomer reaching its temperature/time limit — typically before the steel is fatigued.
• Correction: replace based on grease-life conditions, check actual operating temperature against the designation, and where relubrication is required by the duty, specify an open or shielded arrangement instead.

Inspection procedure

1. Remove carefully — do not wash away the evidence; keep the bearing and a sample of its grease.
2. Photograph before cleaning: raceways, elements, cage and both fits, with something for scale.
3. Wash in solvent and inspect under magnification in good light; rotate the inner ring to expose the full race.
4. Locate the pattern using the table above — distributed vs localised, at element pitch vs random, on the fits vs the contact surfaces.
5. Record the context: running hours, load/speed, temperature history, lubricant and interval, mounting date, and whether the equipment was idle under vibration.
6. Decide and document: end-of-life replacement, or root-cause correction plus replacement. A short note on the housing saves the next person re-diagnosing the same failure.

A useful ordering of suspects

For a small ball bearing in an electric motor, think electrical pitting → grease life → contamination; for a hub bearing, setting and contamination → brinelling from mounting; for conveyor and heavy positions, misalignment/edge loading → fretting on fits → lubrication. The evidence on the steel decides, not the reputation of the brand.