Abstract
The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism. The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage. Based on the two basic principles of surface strengthening and friction reduction, a substrate (AISI 4135 steel) surface was treated by laser quenching (LQ), plasma nitriding (PN), and bonded MoS2 coating. Systematic fretting wear tests were conducted, and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated. The results indicate that the wear resistances of the LQ- and PN-treated surfaces were significantly improved, and their main wear mechanisms were abrasive wear, delamination, and oxidation wear. The MoS2 coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property, but it incurs the highest wear rate and failure in the form of plastic deformation. Furthermore, the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface, consequently resulting in a significant reduction in wear. An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation, which provides a reference for the anti-fretting protection of related mechanical components.
Highlights
Railways, as the most widely used type of land transportation, play a crucial role in promoting the development of economies and trade worldwide [1]
Sharp and strong diffraction peaks can be observed at 2θ angles of 44.46°, 64.75°, and 82.11° on the surfaces of the substrate and laser quenching (LQ) samples, corresponding to the α-Fe phase with high crystallinity
Three surface treatments were applied to the locking pin material (AISI 4135 steel), the fretting wear experiments and various characterization analyses were performed
Summary
As the most widely used type of land transportation, play a crucial role in promoting the development of economies and trade worldwide [1]. The existence of various types of rail gauges in different countries and regions has hampered further improvements in the comprehensive efficiency of railway transport. Multiform variable gauge trains have been produced and put into service around the world [2], and China has developed a high-speed variable gauge bogie system (see Fig. 1(a)) for the 1,435/1,520 mm gauge switch. As one of the key components of the bogie, the locking mechanism (as shown in Fig. 1(b)) has the function of a wheel track switch and mechanical locking, and its running reliability strongly determines the safe operation of the trains. During the process of wheel track switching, the locking pin will be jacked up by a ramp track (the spring will be compressed), and will be separated from the matching locking block. Thereafter, the bogie will be moved away from the ramp, the spring will be reset to make
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