Effect of initial microstructure an the coarsening behavior of cementite particles

The effect of initial microstructures, martensite and bainite, on the coars ening 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 sta bility of cementite particles in bainite. The coarsening of cementite parti cles 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, a nd a combination of boundary diffusion and matrix diffusio n for cementite particles within laths. In bainite, the coarsening was cont rolled by a combination of boundary diffusion and diffusion along dislocati on for intergranular particles, and controlled mainly by diffusion along di slocation for intragranular particles.