Tracking the railway line in-service behaviour through metallurgical and mechanical property characterisation

Wear, contact-impact, fatigue and corrosion properties are important factors initiating rail track degradation and are composition dependent. This work focuses on the effect of chromium content on the metallurgical and mechanical properties of the the rail steels. Two medium steel railway tracks differing in their chromium content, alloy MS02 with 0.02 wt% Cr and alloy MS03 containing 0.72 wt% Cr, were characterised in order to predict their in-service performance as a function of their chemical composition. The microstructural analysis revealed in MS02 a relatively coarser grain size, consisting of pearlite and grain boundary ferrite. MS03 showed a fully pearlitic structure with no grain boundary ferrite. The average distance between cementite lamella in rail MS03 is shorter than that in MS02. The Rockwell C hardness values of MS02 were lower than those of MS03 which is in agreement with the microstructural analysis. As expected, a finer pearlitic structure observed in rail MS03 resulted in a superior tensile and impact properties as compared to MS02. These data indicate that MS03 with a fully pearlitic structure gives a better wear resistance and higher strength than MS02 and, it is anticipated to give a better corrosion and oxidation resistance due to higher chromium content.