(V) Correlative light, electron and in-situ Raman imaging of modern and historic railway tracks, linking wear and corrosion behavior to microstructure and composition

Monday, September 13, 2021: 1:20 PM
242 (America's Center)
Mr. Andy Holwell , Carl Zeiss Microscopy Ltd, Cambourne, United Kingdom
Dr. Roger Barnett , Carl Zeiss Microscopy Ltd, Cambourne, United Kingdom
Ute Schmidt , WITec GmbH, Ulm, Germany
Rail track metallurgy and cross-sectional profile have evolved since the early twentieth century to meet ever more demanding requirements of wear resistance, hardness and durability, in order to cope with increasing demands of speed, weldability and rolling contact performance. The microstructure is engineered to have high hardness, resistance to rolling contact fatigue and durability to environmental degradation.

Mechanical and corrosion damage in worn 1930s and 1950s rails were compared against unused but environmentally corroded modern rail. Multimodal correlative microscopy and in situ Raman spectroscopy allowed qualitative evaluation of deformation and corrosion mechanisms, against differences in metallurgy and microstructure such as inclusion content, grain size, crystal phase, decarburization and wear.

In-situ correlative Raman imaging was carried out in a field emission scanning electron microscope, correlated with multiple contrast methods in light microscopy, high resolution secondary electron imaging and energy-dispersive x-ray spectroscopy. Light microscopy, EDS and Raman were used together to characterize the microstructure, oxides and inclusions in each rail, localized to specific regions of mechanical damage. This provided a correlation between regions of high wear and deformation with the corrosion species and the contemporary composition of the rail steels. The integration of a Raman microscope in the chamber of the SEM uniquely allows rapid correlative workflows and overlay of spectra with optical and electron imaging.