New Type of Rolling Contact Damage of a Deep-Groove Ball Bearing under Grease Lubrication

摘要

A new type of rolling contact damage that has never been observed under oil lubrication was found in the fatigue tests of the deep-groove ball bearings #6206 under pure radial load and grease lubrication. Two pure radial load levels 9.14 kN and 12.13 kN were applied on the test bearings. To control the occurrence of seizure, the test bearing's inner ring speed was maintained at 1800-2500 min{sup}(-1) and 600-800 min{sup}(-1), respectively, to keep the outer ring temperature below 339 K. The grease used in the tests was composed of a special lithium complex thickener and mineral base oil. In appearance, the damage had a few circular cracks in the ball revolution direction, dented about 20 μm in the surface of a rolling raceway, occurred only in the raceway of fixed races and distributed widely within a loaded zone. Under the surface there were a lot of cracks propagated at 60-80° to the rolling surface at not only the damage position but also at other parts. Cracks at the damage position just opened to the surface. We supposed that the damages were caused by metal-to-metal contacts due to lubricant starvation under grease lubrication.