Failure mechanisms and damage evolution of ceramic balls under coupled Impact–Sliding motion

With the increasingly harsh operating environment of aero-engine mainshaft systems, bearing rolling elements are frequently subjected to periodic impact-sliding coupling during cyclic entry into the load zone and interactions with cage pockets, posing significant challenges to bearing reliability. Under such conditions, the failure behavior and damage evolution of ceramic balls become highly complex. In this study, in-house-developed Si₃N₄ ceramic balls reinforced with TiN and WC are systematically investigated in tribo-pairs with 8Cr4Mo4V and G13Cr4Mo4Ni4V bearing steels under impact-sliding motion. Experiments were conducted at a contact stress of 2.34 GPa, a relative sliding speed of 10 m/s, and an impact frequency of 15 Hz. Surface damage and material transfer were characterized using white-light interferometry, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that TiN-reinforced Si₃N₄ ceramic balls are more prone to adhesive wear and brittle spalling when paired with G13Cr4Mo4Ni4V steel, whereas WC-reinforced Si₃N₄ ceramic balls mainly exhibit mild abrasive wear with suppressed metal transfer. Time-dependent analysis further indicates that the damage mechanism of WC-reinforced Si₃N₄ ceramic balls evolves toward adhesive-spalling failure against G13Cr4Mo4Ni4V steel, while a stable running-in and surface polishing behavior is observed when paired with 8Cr4Mo4V steel. These findings provide experimental insight into failure analysis and material selection of hybrid ceramic bearings for aero-engine applications.