Defects and Mechanical Properties of Silicon Nitride Ball Bearings for Electric Vehicle Reducers

Abstract

In this study, two types of Si3N4 ball bearings for integrated-type EV reducers developed via different manufacturing processes were analyzed to study the microstructure of the balls and the defects that may occur during the manufacturing process. Three types of defects were confirmed that can reduce the fatigue life of Si3N4 ball bearings in operating environments. The microstructure was analyzed to identify the main additive components of each bearing, and pore defects with a size of less than 1 μm, and the types (particle defects or surface defects) and sizes of defects, were analyzed using LSCM, OM, and SEM. Hardness and fracture toughness, which are representative mechanical properties of ceramic materials, were evaluated. The results, evaluated using a Vickers indentation crack-based method, were statistically analyzed to confirm differences in hardness and fracture toughness between the two samples.