Modelling of grain boundary segregation kinetics that are responsible on irreversible and reversible temper embrittlement of engineering steels

Abstract

There are presented the computer models of multicomponent grain boundary segregation (GBS) that are formed at quenching or tempering of engineering steels. The modelling of these processes requires different algorithms. The dynamic model of segregation at quenching is based on solution of independent diffusion and adsorption-desorption equations for various impurities in steel tied by feedback. The model of segregation under tempering considers the influence of alloying and tempering parameters on concentration and thermodynamic activity of carbon in the α-solid solution. It is based on regression analysis of experimental data on grain boundaries chemical composition obtained by Auger spectroscopy. There is established that grain boundary enrichment by harmful impurities (S and P) is possible after carbon and nitrogen segregation dissolution. The models allow to analyze the competition of elements during formation of GBS and to establish main factors responsible on development of different kinds of embrittlement in engineering steels with various alloying and content of harmful impurities.