überrollungsbedingte Werkstoffstrukturänderungen bei der Hochtemperaturbeanspruchung von Wälzlagern

Effects of thermally and mechanically induced microstructural material changes on failure mechanisms during rolling contact fatigue were investigated. Research was executed with angular contact ball bearings made from steels Cronidur 30, M50 and 100Cr6. Temperatures up to 200 °C, contact pressures up to 2400 MPa and up to 10 8 cycles of overrolling could be loaded with a special test rig. Microstructural changes as a consequence of the combined mechanical and thermal stresses have been detected by X-ray diffraction analysis of residual stresses and retained austenite as well as by metallographic inspection. The loading of the ball bearings particularly for higher temperatures and high contact stresses resulted in changes of residual stresses and changes of the Full Width Half Maximum (FWHM). Smallest changes of residual stresses and FWHM occur in the material M50 whereas Cronidur 30 exhibited somewhat higher changes of these measured quantities. In the Cronidur 30 no transformations of retained austenite could be detected. Obviously contact stresses lower 2400 MPa are not sufficient to transform larger quantities of retained austenite. A deformation number increases slightly with the number of cycles affected partially by the test procedure with interruptions leading to additional changes of residual stresses and FWHM in surface layers. Lightmicroscopy prove that no microstructural changes arise. Estimates of a rolling contact fatigue limit from deformation numbers correlate well with literature data. Maximum values are obtained for Cronidur 30 with the consideration of mentioned restrictions in the test procedure.