A rail’s microscopic grain structure determines whether it cracks or holds up under a speeding train’s weight. This project will watch those grains deform in real time inside a scanning electron microscope—something never done before for rail steels. Standard rails cost the UK £3.9 billion in renewals in 2021/22, and wear and rolling contact fatigue limit how long tracks last. Advanced steels and laser-clad coatings are harder and more resistant, but engineers still don’t understand exactly how their refined microstructures respond to service loads or why damage like white etching layers from grinding still appears. By combining electron backscatter diffraction, nanoindentation, and high-resolution digital image correlation inside the microscope, the team will map strain fields at the grain level for the first time. If successful, this work could guide the design of rails that last longer, require less grinding, and need fewer replacements—cutting both cost and carbon emissions from rail maintenance. It also tests laser-clad additive repair to restore worn sections without creating weak interfaces, potentially extending the life of premium rail materials. The project is applied materials science with a clear industrial target.
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This project aims to deepen our understanding of the mechanisms of damage initiation in advanced rail materials and how the microstructure of the materials affects this. This project will be undertaken in collaboration with The Royce Institute leveraging their world-leading expertise and equipment investment in materials characterisation and has been developed following introductions to their Tescan And Newtek In-Situ Testing (TANIST) facility during the Metallics CDT conference. The Royce Institute’s state-of-the-art facilities, including Electron Backscatter Diffraction (EBSD) and in-situ Digital Image Correlation (DIC), will provide unparalleled in-situ data on the evolution of microstructure and crack initiation and growth, at a scale not seen previously in the development of rail steels. The proposed research aligns perfectly with the focus of this call on advanced materials and its commitment to supporting collaborative research. Within standard grade rails, wear and RCF are critical challenges limiting the lifespan of rail infrastructure, incurring substantial economic costs (£3.9bn on renewals in 2021/22), carbon costs and hindering railway capacity increases. Previous approaches to extending standard grade (R260) railway track component life include regular maintenance, such as grinding, which is conducted to maintain rail profiles (preventive), to keep contact conditions optimum and to remove damage such as cracks (corrective). Advanced rail steels, such as heat-treated grades (350HT), high performance alloys (e.g. HP335) and laser clad coatings (e.g., Martensitic Stainless Steel (MSS)) offer a significant leap forward in rail infrastructure, offering a promising solution to the financial and safety critical challenges of rail wear and rolling contact fatigue (RCF). Although railways have been around since the 1800s every advance in materials is met with an increase in demand (speed, axle loads, drive to reduce maintenance need), so these remain live issues that limit transition to a low carbon transport future. Most recently, advanced rail materials with refined microstructures which provide a harder material with greater resistance to deformation and crack initiation, but they have not resolved the underlying issues. This project will provide a better understanding of the way in which the intricate microstructure of these materials respond to services loads and the consequent damage initiation mechanisms such as white etching layer (WEL) from grinding. This will allow further material design improvements to create rail, which is more durable, easier to maintain and ultimately more sustainable. Collaboration with The Henry Royce Institute will enable novel in-situ testing within the scanning electron microscope (SEM) with High resolution digital image correlation (HRDIC) to provide an in-depth study of the microstructure of advanced rail materials using novel techniques for rail development. Through the study of the behaviour of the microstructure of advanced rail materials with EBSD, nanoindentation and in-situ SEM with HRDIC, visualisation of strain fields will be possible for the first time which will help our understanding of how the grain size and orientation affects deformation. As advanced rail materials are developed it is critical to understand how the refined microstructure behaves with common damage mechanisms to design against current problems. This project will explore the potential of laser-clad additive repair to extend the lifespan of advanced rail materials. By applying a targeted area of like-on-like material, we aim to optimise the microstructure and ensure the repaired region is as durable as the original material whilst avoiding weakness at the interface of different materials.
Albert Smith (Co-Investigator)David Fletcher (Co-Investigator)Jack Donoghue (Co-Investigator)Kamran Mumtaz (Co-Investigator)Kate Tomlinson (Principal Investigator)Roger Lewis (Co-Investigator)
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