Coarsening behavior for M23C6 carbide in 12 %Cr-reduced activation ferrite/martensite steel: experimental study combined with DICTRA simulation

Abstract

Based on the multi-component aspects of thermodynamics and diffusion, coarsening behavior of M23C6 (M = Cr, Fe, W) carbide at 650 °C in 12 %Cr-reduced activation ferrite/martensite steel has been investigated experimentally using scanning transmission electron microscopy, combined with DICTRA simulation. Both the experimental measurements as well as the simulations indicate that the interfacial energy of M23C6 carbide in this steel at 650 °C is probably 0.5 J m−2, and the coarsening rate of M23C6 carbide is very low. The influence of a change in Mn, V, and Ta content and temperature on the coarsening rate of M23C6 carbide is also investigated. The results show that the coarsening rate is increased by adding Mn and reduced by V and Ta addition, respectively, while an increase in the coarsening rate by an order of magnitude with increasing temperature per 50 °C between 600 and 750 °C. Precipitation of Laves (Fe2W) phase during aging has a negligible effect on the coarsening of M23C6.