Coarsening resistance of M2C carbides in secondary hardening steels: Part III. Comparison of theory and experiment

Abstract

A model for the coarsening resistance of multicomponent carbides was used to study the effect of Mo and Cr on the coarsening kinetics of M2C carbides in commercial AF1410 and experimental alloy steels. Experimental studies of coarsening behavior of the carbides in these steels have been made by using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The measured coarsening rate constant agrees with model predictions within a factor of 2 to 3. The coarsening kinetics of M2C carbides in these alloys is found to be controlled by the volume diffusion of alloying element M. A Cr-Mo alloy steel with the predicted optimum composition showed the slowest coarsening kinetics and highest hardness at long tempering times.