Experimental Study of Cyclic Rolling-Contact Fatigue of Silicon Nitride Balls

摘要

A newly developed pure-rolling fatigue test rig with three contact points for bearing balls was used to perform rolling-contact fatigue (RCF) tests. The fatigue properties of GCr_15 steel balls and two kinds of Si_3N_4 ceramic balls (GSN-200 and NBD-200) produced with different technologies were compared. Life test data, summarized in accordance with the Weibull theory, showed that the life of the GSN-200 balls was close to that of the GCr_15 balls, whereas the life of the NBD-200 balls was much longer than those of GSN-200 and GCr_15. Under the same working condition, the temperature rise of all the ceramic balls was lower than that of the steel balls. Ball surfaces were examined after failure with optical microscopy and scanning electron microscopy. It was identified by test that the failure mode of ceramic balls was surface spall. The research shows that subsurface cracks play a dominant role in spalling failure. These cracks originated from volume defects of the material and propagate to form elliptical fatigue spalls.