The significance of Nb interface segregation in governing pearlitic refinement in high carbon steels

Abstract The effect of Nb on interlamellar spacing of pearlite in high-carbon steel and redistribution of Nb atoms between ferrite and cementite was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT). The results of the experiments suggest that Nb atoms were incorporated in the cementite lattice forming Nb-alloyed cementite, which was present as a solute. The segregation of Nb atoms at the ferrite/cementite boundary forms non-equilibrium chemical boundaries. It is proposed that Nb exhibits a strong solute drag effect, which is effective in preventing migration of interphase boundary, leading to the refinement of pearlite interlamellar spacing.