Abstract
Using the commercial ball bearing steel, we have studied the effects of retained austenite in the heat-treated structure on the rolling fatigue life. The results of the experiments are summarized as follows:
(1) The fatigue life depends largely on the quality of the matrix (tempered martensite), and becomes maximum when the solid solute C% is 0.5∼0.6% on quenching.
(2) In the fatigue test, both the surface and the internal hardness of the rolling part of the ball bearing steel increase to a great extent when a large amount of retained austenite is contained.
(3) A semicircular stress-affected zone is present at the rolling part in the fatigue test, where plastic flow and tempering effects are recognized in the matrix. It is also found that the retained austenite gradually decomposes during testing.
(4) The presence of the retained austenite plays an auxiliary role in improvements of the fatigue life and reduces its irregularity.
