F. R. Kapsalamova, S. А. Krasikov.
ABSTRACT
A thermodynamic analysis of phase transformations in the multicomponent system Fe-Ni-Cr-Cu-Si-C has been carried out, which is of interest for a promising metallothermal technology for producing a wear-resistant alloy. To assess the phase composition and structure of the alloy, we used a computer calculation of characteristic polythermal sections of the phase diagram of the system using the Thermo-Calc software package (version TCW5), based on numerical modeling of phase equilibrium by the CALPHAD method and using the TTFe – Thermotech Fe-based Alloys Database, which contains information about chemical elements and is intended for calculating stable and metastable phases in multicomponent alloys. Phase transformations were considered at temperatures from 300 to 1400°С and variable contents of alloying elements Ni, Cr, Cu, Si, C with a step of 100ºC. The polythermal sections of the phase diagram of the Fe-Ni-Cr-Cu-Si-C system are calculated and the critical temperatures of phase transformations in the alloy and the chemical compositions of the phases formed in them (α, β, β2, γ, γ2, L) are determined. The results of thermodynamic modeling showed that as the alloy based on iron is alloyed, its microstructure becomes more complex and the phase composition changes, which take place during gas-flame surfacing. To study the process of solidification in order to obtain quantitative information about the stages of crystallization of the alloy, the critical temperatures separating them, the composition and amount of precipitated phases, the effect of temperature was revealed. The nature of the temperature dependence of the crystallization of the melt showed a transition at 950°С nonequilibrium crystallization of the melt to the stage of equilibrium, which suggests a fine-grained structure of the coating. Thermodynamic analysis made it possible to predict the ferrite-martensitic structure of the coating with inclusions of ledeburite in the case of metallothermal technology for obtaining a wear-resistant alloy. The constructed polythermal sections showed that the complete dissolution of all components in the liquid phase occurs at a temperature of ~ 1400°C.
KEY WORDS:
thermodynamic modeling, transformations, Thermo-Calc, mechanochemical alloying, surfacing material
DOI: 10.31857/S0235010621030087