Rolling contact fatigue of silicon nitride bearing balls under pure rolling condition

A newly developed pure rolling fatigue test rig with three contact points for bearing bails was used to perform rolling contact fatigue （RCF） tests. The fatigue properties of GCrl5 steel bails and two kinds of Si3N4 ceramic balls （GSN-200 and NBD-200） produced with different technologies were compared. Ball surfaces were examined after failure with optical microscope and scanning electron microscope （SEM）. It was identified by tests that the failure mode of ceramic balls was surface spail. The main factor of ceramic bail failure was principal tensile stress. Life tests data, summarized in accordance with the Weibull theory, showed that the life of GSN-200 balls was close to that of GCrl5 balls, whereas the life of NBD-200 balls was much longer than those of GSN-200 and GCr15. Under the same working condition, the temperature rise of all ceramic bails was lower than that of steel balls, and their crack propagation rates were slower than that of steel balls.