Microstructure and mechanical properties of novel rail steels

Abstract

Four new rail steels, alloyed with Cu, Cr, Ni and Si, were designed to improve the corrosion resistance of conventional C–Mn rail steel. The mechanical behaviour of these four rail steels were tested and compared qualitatively with C–Mn, Cu–Mo and Cr–Mn rail steels. While the strengths of Cu–Mo, Cr–Mn, Cr–Cu–Ni and Cr–Cu–Ni–Si rail steels were comparable; the strengths of Cu–Ni and Cu–Si steels were relatively low. The ductility of Cu–Mo and Cu–Ni rail steels were higher compared to C–Mn and Cr–Mn rail steels. The optimum combination of strength and ductility was realised in the case of Cu–Mo rail steel, followed by Cr–Cu–Ni and Cr–Cu–Ni–Si rail steels. The tensile properties have been understood by considering microstructural (notably, lamellar spacing of pearlite) and fracture surface features. The effect of alloying elements on hardness and tensile properties has been explained based on their effect in shifting the continuous cooling transformation curves as well as austenite stability region, in addition to solid solution strengthening and strengthening by carbide formation.