Investigations on the growth kinetics of Laves phase precipitates in 12% Cr creep-resistant steels: Experimental and DICTRA calculations

The growth kinetics of Laves phase precipitates (type Fe2W) in the early stage of creep (650 °C for 10,000 h) in two 12% Cr ferrite–martensitic steels has been investigated. In one alloy the Laves phase formed on tempering, while in the second alloy the Laves phase precipitated during creep. Kinetic simulations were performed using the software DICTRA. The particle size of the Laves phase was measured on transmission electron microscopy samples. The equilibrium phase fraction of the Laves phase was reached in the first thousand hours. Simulations of particle growth showed good agreement with the experimental results. Competitive growth between M23C6 and the Laves phase showed that M23C6 carbides reached their equilibrium after 12 days, whereas the Laves phase reached equilibrium after 3 months. Simulations of the influence of the interfacial energy and addition of Co, Cu and Si on Laves phase precipitation are presented.