Phase Equilibria in the Cr–Fe–Si–C System in the Composition Range Representative of High-Carbon Ferrochromium Alloys Produced in South Africa

Alloys in the composition range of Cr 50–65, Si 0–10, C 4–8 %, balance Fe were subjected to differential thermal analysis, the classical quench method, microscopic examination, X-ray diffraction and electron-microprobe analysis. The liquidus temperatures and a considerable proportion of the phase constitutions have been determined for these alloys. The primary phase is (Cr,Fe)₇C₃ over the entire range of alloys investigated. Two pseudo-binary eutectics were identified; these eutectic reactions result in the formation of (Cr,Fe)₇C₃ and either α-or γ-iron–chromium solid solution, together with a eutectic reaction, which results in the formation of γ-iron–chromium solid solution and (Cr,Fe)₂₃C₆. There is a peritectic reaction between liquid alloy and (Cr,Fe)₇C₃ that yields (Cr,Fe)₂₃C₆, and a peritectoid reaction in which (Cr,Fe)₇C₃ and α-iron–chromium solid solution react to form (Cr,Fe)₂₃C₆. Those phases that contain silicon have been identified.