Doosan DX60R Shop Manual page 106

Frettage
Corrosion set up by small relative movement of parts with no
lubrication.
Replace bearing. Clean all related parts. Check seals and
check for proper lubrication.
Heat Discoloration
Heat discoloration can range from faint yellow to dark blue
resulting from overload or incorrect lubrication.
Excessive heat can cause softening of races or rollers.
To check for loss of temper on races or rollers, a simple file test
may be made. A file drawn over a tempered part will grab and
cut metal, whereas a file drawn over a hard part will glide
readily with no metal cutting.
Replace bearing if overheating damage is indicated. Check
seals and other related parts for damage.
Stain Discoloration
Discoloration can range from light brown to black caused by
incorrect lubrication or moisture.
If the stain can be removed by light polishing or if no evidence
of overheating is visible, the bearing can be reused.
Check seals and other related parts for damage.
General Maintenance Procedures
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