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Oral Poster

Rolling contact-induced near-surface microstructural alteration in high nitrogen bearing steel

Thursday (27.09.2018)
16:09 - 16:12 S1/01 - A5
Part of:

White etching cracks (WECs) in roller bearing applications lead to premature failures occurring at as early as 10-20% of L10 bearing life. The high nitrogen alloyed martensitic bearing steel X30CrMoN15-1 is reported to have a remarkably higher WEC-resistance compared to conventional martensitic bearing steels. The reason for this is still unclear. To clarify this, we have studied rolling contact fatigue behavior of the X30CrMoN15-1 deep groove ball bearing by scanning electron microscopy and atom probe tomography. Both, SEM-energy dispersive X-ray spectroscopy and atom probe tomography measurements, reveal C, N gradients within a depth of 15 μm below the raceway of the fatigued bearing. In contrast, in the case of the as-received bearing, both C, N atoms are homogeneously distributed in the matrix. This difference indicates the dissolution of precipitate phases (M23C6 and M2N) under the effect of cyclic rolling contact in the near-raceway region. Through such dissolution process an enrichment of their easily diffusible alloying elements C and N is obtained in the surrounding martensitic matrix. Besides, we were able to detect precipitates at different stages of dissolution in the near-raceway region of the fatigued bearing by electron channeling contrast imaging. It is supposed that dissolution of precipitates starts when strain within the precipitate phases has been accumulated to a certain extent.

Yu Qin
Max-Planck-Institut für Eisenforschung GmbH
Additional Authors:
  • David Mayweg
    Max-Planck-Institut für Eisenforschung GmbH
  • Prof. Dr. Dierk Raabe
    Max-Planck-Institut für Eisenforschung GmbH
  • Dr. Michael Herbig
    Max-Planck-Institut für Eisenforschung GmbH