Abstract
Rail foot covered by a fastener will suffer from crevice corrosion, leading to thinning and localized attack of crevice interior posing a risk of failure. This work investigated crevice corrosion behavior of a typical pearlitic high-speed rail steel U75V, focusing for the first time on the effect of pearlitic microstructure refinement achieved by heat treatment with different cooling rates 2, 5, and 10°C/s. Under anodic polarization, localized dissolved spots presented on the as-received sample, where crevice corrosion mostly initiated from. For cooling rates 2 and 5°C/s, localized dissolved spots were also observed but crevice corrosion was mostly presented as general corrosion instead of from local spots, ascribed to enhanced tendency of uniform dissolution due to microstructure refinement and homogenization. For cooling rate 10°C/s, crevice corrosion expanded flocculently, ascribed to preferential dissolution of pearlitic nodules with entangled cementite due to over refinement. Crevice corrosion was obviously accelerated by microstructure refinement. Cooling rates 5 and 10°C/s led to the fastest and slowest expansion of the corroded area, respectively, while the corrosion depth was just the opposite based on the same amount of metal loss. This work provides important information regarding the effect of pearlitic microstructure refinement on crevice corrosion and introduces a facile method forin situmonitoring of crevice corrosion.
Highlights
Rapid development of the high-speed railway industry requires high reliability and durability of materials
This well agrees to Katiyar et al (2018) who reported that refined microstructure was helpful on decreasing the corrosion rate, but further refinement may lead to accelerated corrosion again
The effect of pearlitic microstructure refinement on crevice corrosion has been studied on a typical high-speed rail steel U75V via facile in situ monitoring during electrochemical measurement
Summary
Rapid development of the high-speed railway industry requires high reliability and durability of materials. Contact–impact, fatigue (or rolling contact fatigue, i.e., RCF), and corrosion are the main reasons for material degradation in rail tracks (Hernandez et al, 2007; Shurpali et al, 2012; Hernandez-Valle et al, 2013; Shariff et al, 2013; Safa et al, 2015; Zhao et al, 2015; Yazici and Yilmaz, 2018; Liu et al, 2019). Among these issues, corrosion attracts far less attention than the others while its damage is no less (Xu et al, 2021). Due to the special structure between the fastener system and rail foot section, the crevice corrosion issue on the rail track has been reported by Panda et al (2008), Panda et al (2009) and has been recently investigated in details by the authors of this work, especially under conditions of varying gap size (Xu et al, 2022)
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