Non-equilibrium analysis of the graphitization process in cast irons

Editorial Board PCSS Journal; S.V. Bobyr

doi:10.15330/pcss.26.3.520-525

Authors

S.V. Bobyr Uppsala University, Angstrom Laboratory, Uppsala, Sweden; Iron and Steel Institute of Z.I. Nekrasov, National Academy of Sciences of Ukraine, Dnipro, Ukraine

DOI:

https://doi.org/10.15330/pcss.26.3.520-525

Keywords:

thermodynamics, graphitization, cast iron, alloying elements, vacancies, diffusion

Abstract

A diffusion-vacancy mechanism has been developed that describes the process of graphitization of cast iron, and does not use the pressure of graphite on the matrix to explain the diffusion of iron. The values of thermodynamic forces and kinetic coefficients were calculated for the case of graphitization of a binary alloy of the Fe–C system with 2.5% C at 1100°C. It was established that under the conditions of a stationary flow of vacancies during the graphitization of cast iron in the solid phase, the concentration of vacancies at the γ-phase – graphite boundary is approximately 0.97723 times less than the concentration of vacancies in the γ-phase. An assessment was made of the influence of alloying elements, using the example of chromium and silicon, on the graphitization of cast iron with 2.5% C. A thermodynamic parameter of graphitization was proposed that takes into account the influence of all alloying elements and characterizes the degree of stability of graphite under these conditions.

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