How can you identify an overheated wheel or journal once it has cooled down?

Identifying an overheated wheel or journal after it has cooled down can effectively be done by observing discolored metal. When a wheel or journal overheats, it can cause a change in the metal's physical properties, which often results in discoloration. This discoloration occurs because excessive heat can alter the metal's microstructure, leading to visible changes in color. For instance, the metal may appear bluish, purplish, or even blackened in areas that have experienced extreme temperatures, indicating potential damage or degradation.

The other methods may not reliably indicate previous overheating. Listening for unusual sounds, although important during operations, would be less effective once the component has cooled down. Using a thermal gun is useful for assessing temperature during operation, but once the part has cooled, this method becomes ineffective for identifying past overheating. Examining the wheel's alignment can point to operational issues but doesn't provide direct evidence of overheating. Observing discoloration, therefore, serves as a clear visual indicator of prior thermal stress on the wheel or journal.