FATIGUE LIVES AND MATERIAL PROPERTIES OF SILICON NITRIDE BALLS FOR HYBRID BEARING APPLICATIONS

摘要

Hybrid bearings equipped with steel rings and high quality silicon nitride rolling elements enjoy significant performance advantages over all-steel bearings. Starting material, blank processing, and ball finishing are all critical to achieving high quality silicon nitride rolling elements. In this study, silicon nitride balls from various sources were examined. Optical microscopy and SEM were used to locate and identify surface and bulk defects. Mechanical properties such as hardness and fracture toughness were measured by Vickers indentation. The rolling contact fatigue life of the silicon nitride balls was evaluated in a specially-designed tribological test rig. Fatigue lives were found to correlate strongly with the level of surface defects, but not significantly with microstructure and mechanical properties.