Channeling behavior of lubricating greases in rolling bearings: Identification and characterization

The churning phase, i.e., the early phase in bearing operation, ends when the grease has been migrated from in-between the rolling elements to the unswept area. This process is often called “channeling or clearing”. In the present study, early stage temperature profiles of running bearings are used to identify the length of this phase using different greases. It is shown that grease undergoes a microstructural change during the channeling/churning phase. Good (“peak type”) channeling greases maintain their structural integrity and undergo only a very short period of churning, whereas for poor (“plateau type”) channeling greases a significant microstructure degradation occurs. This is ascribed to the longer churning phase. The channeling properties may be attributed to the microstructural flexibility of greases.