Investigation on butterfly white etching area formation mechanism and crack source at different stages in M50 bearing steel

• Published in: Tribology international 2024-05, Vol.193, p.109429, Article 109429
• Main Authors: Yang, Liqi, Xue, Weihai, Cao, Yanfei, Liu, Hongwei, Duan, Deli, Li, Dianzhong, Li, Shu
• Format: Article
• Language: English
• Subjects: Butterfly white etching area; Formation mechanism; M50 bearing steel; Rolling contact fatigue
• ISSN: 0301-679X
• DOI: 10.1016/j.triboint.2024.109429

Rolling contact fatigue tests with different stresses and cycles have been conducted to study the formation mechanism and crack source of butterfly white etching area (WEA) in different stages of M50 bearing steel. The results suggest that the structural transformation is prior to cracks. The initial microstructure is the nanocrystalline α-Fe formed by dislocation assisted carbon migration. With the extension of cycles, unlike the previous studies, the butterfly-origin carbide is refined into Mo2C and M7C3 nanocrystalline by the accumulated dislocation clusters. Subsequently, the increase of interfacial energy drives the metal elements diffusion and thus the formation of amorphous structures. A new mechanism called diffusion-assisted dislocation has been proposed for butterfly WEA formation. [Display omitted] •The evolution of butterfly WEA in M50 bearing steel has been studied under different stresses and cycles.•A new detailed formation mechanism of butterfly WEA is proposed.•The structural transformation of butterfly WEA is prior to cracks.•M2C carbides are more likely to cause butterfly WEA and cracks.