Accelerated four-ball and five-ball rolling tests were performed on HIPed Si3N4 ball samples (rough lapped with surface
roughness value Ra0.08 μm and Rq0.118 μm) in fully lubricated condition. The contact load and the stress cycles per minute
for four-ball rolling and five-ball rolling tests were maintained the same. The rolling track appearances of five-ball tests reveal
severe sliding occurred. In one case, the opposite arc cracks were generated all over the two sides of the rolling track, and this
could not be explained by simplified kinematics model. The failure mechanisms were discussed, which suggest the sliding on the
two sides of the track was in the opposite direction
