Laboratory simulation of martensite formation of white etching layer in rail steel

Micro and Nanoscale Characterization of Complex Multilayer-Structured White Etching Layer in Rails

“…Furthermore, the identified nano-twinning in the WEL, Figures 7a-b and 8, is expected in martensite. This morphology was observed for martensite produced through heat treatment (e.g., by laser treatment [3,17]) of rail steels with a similar composition to the steel considered in this study. Moreover, the redistribution of manganese is an important indicator of a high temperature increase, possibly up to 1400 • C, in rails [6].…”

“…Formation of WELs, in accordance with the aforementioned hypotheses, are strongly supported by separate laboratory simulations. For example, (ultra)fast heat treatments can produce martensite with hardness and grain sizes comparable to those of the studied WEL in rails [17], or martensite with a high hardness and a twinned substructure [3]. A similar white layer is also commonly observed in the surface of loaded components, exposed to a significant temperature increase, e.g., during surface machining [18] and hard turning [19,20].…”

“…The studied WELs were taken from an R260Mn grade rail track (chemical composition: Fe-0.67 wt.% C-1.51 wt.% Mn-0.21 wt.% Si). The rail was originally implemented between 1989 and 2007 in a straight track site between Meppel and Steenwijk in the Netherlands [17]. Corrosion and oxidization products formed in the rail surface during the storage, due to unprotected laboratory storage in air after removal.…”

“…After the relevant sample preparation procedure [17], the cross-sectional WEL specimen shown in Figure 1b was characterized via electron backscatter diffraction (EBSD). An FEI Quanta-450 field emission gun scanning electron microscope (FEG-SEM) (FEI, Hillsboro, OR, USA), equipped with a Hikari-Pro EBSD detector (EDAX Inc., Mahwah, NJ, USA), was used for the scans.…”

“…However, automatic orientation mapping methods, e.g., electron backscatter diffraction (EBSD) and the recently developed automatic crystallographic orientation mapping in transmission electron microscopy (ACOM-TEM) with an improved spatial resolution [21,22], have only been employed in a few of the aforementioned studies. The EBSD and ACOM-TEM methods provide accurate crystal orientation and misorientation measurements and are inherently useful in revealing the deformation structures in the WEL [17] and the strain gradient in the rails [23,24]. Characterization and quantification of such structures by other methods, such as TEM and APT, are difficult.…”