Advances in the Kinetic Theory of Carbide Precipitation

Abstract

Abstract. The precipitation, coarsening and reversion of carbides can determine the quality of steels. This paper is a review of efforts towards better, practical theory for all of these solid-state reactions. IntroductionCarbides are the essence of thermomechanically-processed microalloyed steels which are used in the hundreds of millions of tonnes in creating the infrastructure which leads to a better quality of life. Carbides also feature in special steels, such as the creep-resistant alloys which allow a greater efficiency in the generation of electricity. There is therefore a requirement to understand and model all aspects of carbides in the microstructure of iron and its alloys.

On the effect of long-term creep on the microstructure of a 12% chromium tempered martensite ferritic steel

“…Microstructural, chemical and crystallographic information on the phases in such microstructures can serve as input and/or validation criteria for thermodynamic and kinetic calculations. Most importantly, however, such microstructural changes affect the properties of tempered martensite ferritic steels [40] and the consequences of these changes need to be well understood for a safe operation of critical components in fossil-fired high-temperature plants.…”

“…Today there is a good understanding of the factors that govern the kinetics of carbide precipitation and growth [38][39][40]. It is important to highlight two aspects that characterize our material.…”

Carbide-free bainite in steels

“…although the carbon concentration changes at the cementite-ferrite interface, silicon does not change at all through the interface, indicating that the concentration of silicon is uniform throughout both phases. The trapping of silicon in cementite dramatically reduces the free energy change associated with precipitation, with a corresponding large reduction in precipitation kinetics (Bhadeshia, 2003;Bhadeshia et al, 2003), as Fig. 12.4 illustrates.…”

Effect of annealing process on the abnormal grain growth behavior during carburizing of 20CrMnTi steel

“…Diffusional growth and LSW coarsening model for TiC particlesAccording to diffusional growth theory, the evolution of average diameter d of TiC particles with time t follows the parabolic law[11,12], i.e.…”