Assessing the impact of thermal loading from brake shoes on microstructure and mechanical properties in various railway wheel steels: a comparative study

This research delves into the intricate relationship between microstructure and mechanical properties of railway wheels, focusing on the effects of thermal loading induced by brake shoes. Eight distinct wheel steels were investigated, revealing significant variations both in microstructure and mechanical properties, particularly influenced by carbon content and temperature reached. To replicate the effects of shoe braking, three different heat treatment conditions at various holding temperatures were applied to the samples. Ferritic-pearlitic steels exhibited properties primarily governed by the pearlite phase, impacting fracture toughness. Alloy-enriched steels displayed microstructures featuring traces of bainite, affecting mechanical properties. The heat treatment conducted at temperatures ranging from 700°C to 970°C resulted in substantial microstructural transformations, influencing mechanical properties. While some steels demonstrated improvements in mechanical properties post-treatment, most of them exhibited decreased performances. Notably, the heat treatment induced alterations in the original perlite morphology and grain size leading to a decrease in hardness and strength, coupled with an increase in ductility. However, fatigue crack growth behaviour remained consistent across materials, indicating minimal sensitivity to heat treatment. These findings offer valuable insights into railway wheel steel behaviour under thermal stress, informing strategies for enhancing performance and durability in real-world applications.