Effect of Initial Microstructure on the Coarsening Behavior of Cementite Particles

Abstract

The effect of initial microstructures, martensite and bainite, on the coarsening behavior of cementite particles during tempering at 973 K for medium carbon steels has been investigated. The coarsening of cementite particles in bainite proceeded more slowly than in martensite, due to the thermal stability of cementite particles in bainite. The coarsening of cementite particles proceeded by a combination of the different coarsening mechanisms. The observed coarsening kinetics in martensite were found as a combination of boundary diffusion and diffusion along dislocation for cementite particles at boundaries, and a combination of boundary diffusion and matrix diffusion for cementite particles within laths. In bainite, the coarsening was controlled by a combination of boundary diffusion and diffusion along dislocation for intergranular particles, and controlled mainly by diffusion along dislocation for intragranular particles.