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Speckles and Discoloration

Speckles and Discoloration

Condition Cause Solution

Speckles

  • Raceway surface is matted and speckled.
  • Speckles are clusters of tiny dents.

Discoloration

  • The surface color has changed.
  • Ingress of foreign objects
  • Poor lubrication
  • Temper color by overheating.
  • Deposition of deteriorated oil on surface

Speckles

  1. Improvement in sealing efficiency
  2. Filtration of oil
  3. Improvement in lubrication system

Discoloration

  1. Oil deposition is removable by wiping with an organic solvent (oxalic acid).
  2. If roughness is not removable by polishing with sandpaper, it is rust or corrosion. If completely removable, it is temper color due to overheating.

Photo: Inner ring of double row tapered roller bearing (RCT bearing)

  • Inner ring of double row tapered roller bearing (RCT bearing)
  • Raceway surface is speckled
  • The cause is electric pitting.

Photo: Ball of deep groove ball bearing

  • Ball of deep groove ball bearing
  • Speckled all over
  • The cause is foreign objects and poor lubrication

Photo: Outer ring of spherical roller bearing

  • Outer ring of spherical roller bearing
  • Partial oil deposition on raceway surface

Photo: Spherical roller bearing

  • Spherical roller bearing
  • Discoloration of inner and outer ring raceway surfaces
  • The cause is deterioration of lubricant.