Phase transformation in the subsurface of case carbonitrided bearing steels under rolling contact fatigue

GH Jiang and SX Li and JB Pu and F Yu, TRIBOLOGY INTERNATIONAL, 169, 107468 (2022).

DOI: 10.1016/j.triboint.2022.107468

Although considerable effort has been made to understand the microstructural change in white etching area (WEA) of bearing steels under rolling contact fatigue (RCF), the WEA formation mechanism remains unclear at atomic scale. We interpreted the nanocrystallization and phase transformation via high-resolution transmission electron microscope images combined with molecular dynamic simulations. A lamellar morphology of WEA was generated under RCF loading. The results showed that the matrixes surrounding WEA consist of lamellar microstructures with different orientations. This indicates that there is a sharp deformation transition between the WEA and the matrix. Austenite phase transformation and amorphization were observed in the WEA. MD simulation revealed that the deformation-driven phase transformation involves three stages: face-centered-cubic (fcc) to body- centered-cubic (bcc) phases, bcc to amorphous phase and bcc to fcc transformations. The bcc and newly-formed fcc phases follows Kurdjumov- Sachs orientation relationship of 110fcc // 111bcc.

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