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

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.