Abstract
Due to the increasing demand on pearlitic rails to support heavier loads and higher speeds, grooved rails for tramways and light rail transit (LRT) require strengthening via alloying or heat treatment, i.e. accelerated cooling after hot-rolling. In this study, the wear performance of five different commercial grades is compared using unlubricated twin-disc testing and detailed microstructural characterisation. Results indicate that the vanadium-alloyed steel experiences less than half the wear rate of a heat-treated grade with a similar hardness. This is attributed to the increased stability and toughness of vanadium-containing cementite, as compared to pure cementite. The evidence suggests that vanadium partitions into the cementite lamellae during the formation of pearlite. This improvement in wear resistance due to vanadium could enable an approximately two-fold reduction in the maintenance and life cycle costs relative to heat-treated rail alternatives.
Highlights
The demand to subject rails to higher speeds, greater traffic densities, heavier loads, and mixed traffic enhances damage, mainly in the form of wear, plastic deformation, corrugation, and rolling-contact fatigue cracking [1]
R290V displays less than half the wear rate of an alloy with similar hardness, R290GHT, despite having a higher true interlamellar spacing
For the specific rolling and cooling conditions of the alloys studied in this work, vanadium does not seem to play a role as a grain refiner
Summary
The demand to subject rails to higher speeds, greater traffic densities, heavier loads, and mixed traffic enhances damage, mainly in the form of wear (loss of rail profile), plastic deformation, corrugation, and rolling-contact fatigue cracking [1]. In the case of tramways and light rail transit, the most prominent damage mechanism is wear due to the dense traffic, frequent braking and acceleration of vehicles, sharp turns, and variable loads. A traditional approach to increase the wear resistance is the refinement of the interlamellar spacing of pearlite [2,3], either through alloying or accelerated cooling after rolling, in order to increase the hardness without compromising toughness [4,5,6]. Accelerated cooling can be achieved using compressed air, but is maximised by using water sprays. This can lead to undesired microstructures if water accumulates at cavities in rails with intricate geometries such as grooves. An alternative is to add certain elements such as vanadium or chromium with the aim of increasing the hardness, allowing to reduce the carbon content to improve the weldability of the alloys
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