Contact fatigue of silicon nitride

Ceramics are interesting in various tribological applications, such as roller bearings, cam roller followers and valves as it means improved performance and an increased lifetime. In hybrid bearings silicon nitride balls are used with steel races and cages. The objective of this work was to study the influence of microstructure and environment on cyclic contact fatigue of silicon nitride. A WC ball was cycled on a silicon nitride disc in an MTS 880 to simulate the loading conditions in a hybrid bearing. Four silicon nitrides were tested with a maximum contact pressure of 5–15 GPa, 100,000–5,000,000 cycles and a frequency of 10 Hz. Cracks and indentations were studied by LOM, SEM and interference microscopy.