Eutectic Precipitate Dissolution and Microstructure Evolution of Cr–W–Co Heat-Resistant Steel with Varying Ce Contents

Abstract

The evolution of the microstructure, the dissolution kinetics of (Fe,Cr)₂W Laves phase and the microhardness of Cr–W–Co heat-resistant steel with different Ce concentrations during homogenization were investigated. The mechanism of the influence of Ce on the Cr–W–Co heat-resistant steel during homogenization process was clarified. The homogenization kinetic equation considering lattice parameters and specimen thickness correction was established. The activation energy for Laves phase dissolution in the steel with 0, 0.01 and 0.03 mass pct Ce is determined based on Johnson–Mehl–Avrami–Kolmogorov model to be 302.12, 293.26 and 278.43 kJ/mol, respectively. The activation energy for the dissolution of Laves phase decreases with increasing the Ce content, leading to an increase in the volume fraction of dissolved Laves phase in the steel with the increase in the Ce content from 0 to 0.03 mass pct after the soaking for 7 hours. The homogenization degree of alloying elements Cr, W, V and Nb increases with the Ce content in steel increases after homogenization treatment. The reduction in the standard deviation of microhardness of the steel after homogenization reflects a decrease in the microsegregation degree of alloying elements.