Surface damages on rail became severe with the increase in the axle load and speed. Laser cladding was used to repair the local damages on rail surfaces to ensure the service performance and prolong the life of rails. In the present study, five types of cladding materials (304, 314, 2Cr13, 316L, and 434L) were clad at a small part (trapezoidal shape) of the rail disc to simulate the defected rail in the field. Vickers hardness tester, optical microscopy (OM), scanning electron microscopy (SEM), and electron-dispersive X-ray spectroscopy (EDS) were employed to investigate the service properties of the repaired rail discs. Results indicated that all these five clad rail discs had lower wear-rates than the unclad rail disc. The wear-rates decreased with the increase in the initial hardness of the clad layer. Cracks with large angles mainly propagated along the boundary at the front edge, while at the rear edge, the crack morphology was closely related to the hardness of clad layer. 434L would induce the minimum wear loss and the modest rolling contact fatigue (RCF) of the repaired rail disc, which could be the potential cladding material for repairing the damaged rail.

The impact of the complex braking environment on the service performance of the repair fusion cladding was studied, which is of great significance to improve the ability of the train wheel track system to resist the extremely harsh environment. In this paper, a 316L stainless steel coating was prepared using laser fusion cladding repair technology for the local damage location of the train wheel tread. The MS-HT1000 high-temperature wear tester was used for the experiment. Then, the influence of different braking conditions on the friction and wear performance of the repaired specimens at room temperature and high temperature was analyzed. The results showed that the microstructure of the laser-repaired 316L stainless steel coating was dendritic and eutectic, and its physical phase was mainly composed of austenite, Fe-Cr, and carbides. The wear rate increases with the rise in the shaft weight load, indicating that the higher the contact load, the more severe the wear. In contrast, the influence of the friction coefficient in a room temperature environment is less variable. With an increase in the braking frequency, the wear of the specimen firstly rises and then decreases, and when the frequency is 1 Hz, the value of the wear rate at room temperature is the largest, and the wear surface appears as more peeling layers, and a large amount of wear debris is randomly distributed, which manifests as the wear mechanism being characterized by abrasive wear and adhesive wear. Therefore, different factors affect the wear level of the material differently, with the axle weight load having the greatest influence. The relevant results help to provide corresponding theoretical references for the optimization of parameters under the braking condition of the wheel tread, which ensures the normal operation of the braking system when driving.

Oleic acid-treated ZrO₂ particles were added to lithium grease at 0, 0.2, 0.4, 0.6, and 0.8 wt.%. Friction and wear were evaluated by reciprocating ball-on-disc tests using a GCr15 steel ball (6 mm) and GCr15 disc under 10 N, 3 Hz, 5 mm stroke, 30 min, and 25 ± 2 °C. The 0.4 wt.% formulation gave the lowest average coefficient of friction (0.058, 34.1% lower than the base grease), the smallest wear-scar width (331.05 μm, 17.5% lower), and the lowest wear volume (0.0017 mm³, 73.4% lower). After 360 h of intermittent salt-spray exposure, the 0.4 wt.% group showed the least visible rust, and its corrosion current density in 3.5 wt.% NaCl was 6.77 × 10⁻¹⁰ A·cm⁻², the lowest among the tested formulations. Increasing the content to 0.6–0.8 wt.% increased the coefficient of friction, wear, and corrosion current density again. Thus, within the tested range, 0.4 wt.% oleic acid-treated ZrO₂ simultaneously improves the friction-reducing, anti-wear, and anticorrosion performance of lithium grease. The mechanism still requires verification by particle-dispersion characterization, tribofilm composition analysis, and coating microstructure testing.