Measurement of the Growth Interface Temperature of Eutectic Carbides and Prediction of Solidification Microstructure in the Fe-Cr-C System

摘要

Alloying elements as Cr, W, V, Mo have been added to high speed cast iron for hot rolling to improve fracture toughness and wear resistance. It is important to control solidification structures of these cast irons including eutectic carbides, M_3C, M_7C_3, M_6C and MC, so, it is very important to predict which carbide will solidify for a certain composition and solidification condition. This predictive criteria can be determined by measuring the interface temperature of each carbide in various samples with different solute elements, compositions and growth rates. In this report, firstly the solidification of eutectic carbides such as γ+M_3C and γ+M_7C_3 in Fe-Cr-C ternary system was measured during directional solidification. The relationship between solidification temperature and growth rate was obtained. In eutectic solidification along the γ+M_7C_3 and γ+M_3C mono-variant lines, each coefficient of undercooling k, according to the equation ΔT = kV~(1/2) was obtained. Then, using these data and the calculated phase diagram, the phase selection map for γ+M_3C/γ+M_7C_3 eutectic transition in the Fe-Cr-C system was obtained. The comparison between this map and the experimental microstructures is discussed.