Microstructural changes in White Etching Cracks (WECs) and their relationship with those in Dark Etching Region (DER) and White Etching Bands (WEBs) due to Rolling Contact Fatigue (RCF)

- Detailed analysis of WEC features in comparison to DER/WEBs has been performed.
- Similar microstructure alterations were observed in both WECs and DER/WEBs.
- Distinguishing feature of WEC is the formation of nanocrystalline ferrite.
- Homogeneous Cr/inhomogeneous C redistributions within the WEC network are observed.
- A hardness heterogenisation in WEC is observed.

Substantial microstructural changes, such as Dark Etching Region (DER), White Etching Bands (WEBs) and White Etching Cracks (WECs), can occur in typical bearing steels such as AISI 52100 and 4320 due to Rolling Contact Fatigue (RCF). Although it has been reported that DER and WEBs typically appear in bearings over extended rolling cycles (>100 × 106) as a result of material deterioration under high-stress RCF while WECs are found to occur in much earlier of bearing's life (<20% the calculated L10 life), differences and relationship between DER/WEBs and WECs are not fully investigated or understood. This study investigated the microstructural alterations in WECs in an AISI 52100 through-hardened martensitic bearing using a combination of characterisation methods and the results are directly compared with those observed in DER and WEBs due to high-stress RCF (Šmeļova et al., 2017). The results show that, although the features maybe initiated by different causes, there are many similarities between the microstructural alterations in WECs and DER/WEBs, such as the carbide disintegration, and carbon and chromium movement that plays a role in the formation and development of microstructural alterations in all three features.