White Etching Areas

  Visualization of white etching areas Copyright: © IWM
 

Motivation

In recent years, several applications (wind turbines, railways, automotive) have increasingly reported early failures in bearings made of 100Cr6 steel. Particularly in the wind turbines, these damages are of high operational and economic importance. The damage occurs in the form of axial cracks or smallpox-like breakouts on the running surface of the bearing rings. Metallographic studies reveal areas of the track that cannot be etched and are therefore referred to as "White Etching Areas" or "WEA" for short. Cracks that lead to damage of the bearing, pass through or along the WEA and therefore are also called "White Etching Cracks" (WEC). Although numerous explanations for this phenomenon are given in the literature and discussed controversially, the causal reasons for the appearance of the phenomenon WEA / WEC are still largely unclear. Effective and sustainable measures to prevent the camp early failures require the correct and profound understanding of the physical mechanisms that cause damage.

Goal

  • Understanding of the WEA's formation mechanisms and WEC-related damage mechanisms
  • Evaluation of existing failure hypotheses and their improvement
  • Prediction of conditions leading to formation of WEA by means of FE-modelling and simulation

Content

  • Identification of pre-stages leading to the formation of WEA/WEC failure
  • Assessment of influencing factors and identification of thresholds
  • Microstructural analysis and characterization of tested samples by Scanning Electron Microscopy (SEM), Electron backscatter diffraction (EBSD) and Transmission Electron Microscopy (TEM)
  • Investigation of the mechanical behavior, Visco-plastic and metal plastic effects, during formation of WEA’s
  • Multi-scale modelling and simulation of mechanisms which leads to formation of WEA’s

Funding

DFG (Deutsche Forschungsgemeinschaft)

Publications

  • Oezel, M.; Schwedt, A.; Janitzky, T.; Kelley, R.; Bouchet-Marquis, C.; Pullan, C.; Broeckmann, C.; Mayer, J. (2018): Formation of white etching areas in SAE 52100 bearing steel during rolling contact fatigue testing − Influence of diffusible hydrogen
  • Eser, A., Bezold, A., Broeckmann, C., Schruff, I., Greeb, T.: Simulation des Anlassens eines dickwandigen Bauteils aus dem Stahl X40CrMoV5-1, HTM Journal of Heat Treatment and Materials 69 (2014), p. 127-137
  • Duscha, M., Eser A., Klocke, F., Broeckmann, C., Wegner, H., Bezold, A.: Modeling and simulation of phase transformation during grinding, Advanced Material Research 223 (2011), p. 743-753
  • Diederichs, A.M.; Schwedt, A.; Mayer, J.; Dreifert, T.: Electron Microscopy analysis of structural changes within White Etching Areas. Materials Science & Technology 32 (2016), p. 1683-1693