Friction and wear of pivot jewel bearing in oil-bath lubrication for high rotational speed application

Oil-lubricated pivot jewel bearings are used in the vertical support systems for small, high speed rotating machinery such as flywheels for energy storage, fabric spindles, and centrifuges. The friction and wear of a tool steel pivot tip spinning in a corundum jewel cup were studied experimentally. The contact stress conditions at the tip were analyzed by a finite element method. The friction coefficients of the pivot jewel varied from 0.10 to 0.05, which are typical of boundary lubrication. Wear tests of samples from three groups of bearings indicated that abrasive wear, fatigue wear and adhesive wear occurred in a sequence. The size of the damage of the contact surface varied form 1 μm to dozens of μm. Abrasive and fatigue wear were also observed on the harder jewel cup surface. A wear index based on surface appearance was used to categorize the wear process on the bearing.