A novel microstructure of carbide-free bainitic medium carbon steel observed during rolling contact fatigue.pdfVIP

Scripta Materialia 114 (2016) 13–16 Contents lists available at ScienceDirect Scripta Materialia journal homepage: /locate/scriptamat A novel microstructure of carbide-free bainitic medium carbon steel observed during rolling contact fatigue Chunlei Zheng a, Bo Lv a,b,?, Fucheng Zhang a, Zhinan Yang a, Jie Kang a, Li She a, Tiansheng Wang a a State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China b School of Environmental Chemical Engineering, Yanshan University, Qinhuangdao 066004, China article info Article history: Received 24 September 2015 Received in revised form 19 November 2015 Accepted 19 November 2015 Available online 12 December 2015 Keywords: Carbide-free bainitic steel Rolling contact fatigue Nanocrystalline Inclusion abstract A novel microstructure caused by rolling contact fatigue has been observed in a carbide-free bainitic medium carbon steel. The microstructure is associated with localized non-uniform deformation, and is in the form of vortices of plastic deformation centred on non-metallic inclusions in the vicinity of the contact surface. The resulting severe plastic deformation led to the formation of nanocrystalline material, where fatigue cracks initiated and propagated along the upper edge of the nanocrystalline area. ? 2015 Elsevier Ltd. All rights reserved. Carbide-free bainitic steels (CFBS) are excellent structural material and have been widely applied in industry, such as railway frogs, rails and bearings [1,2]. In the service of railway frogs, rails and bearings, rolling contact fatigue (RCF) is the main failure mode, which leads to microstructural change and mechanical property decay in the surface or subsurface of the steels. Bhadeshia [3,4], Evans et al. [5–8] and Lund [9] determined that the RCF performance of steels is affected by many factors, such as slip, lubrication state, especially non-metallic inclusions. Evans et al. [5–8] and other researchers [9–11] indicated tha