Projection of the Solidus Surface of the Fе–Mo–C System at 0−40 at.% Carbon

Abstract

The solidus projection of the Fe–Mo–C system in the composition range 0−40 at.% C is constructed for the first time using EDX, SEM, HT-DTA, HT-XRD, Pirani–Alterthum method, Vickers microhardness measurement, and CALHPAD modeling technique. It is established that there are three-phase equilibria М₆C + (Мо₂С) + (Мо), М₆С + (Мо) + σ, М₆С + σ + R, М₆С + R + (α-Fe), М₆С + (α-Fe) + (γ-Fe), М₆С + (γ-Fe) + (Мо₂С) and (γ-Fe) + (Мо₂С) + Fe₂MoC on the solidus surface, whose temperatures are decreasing from 1484 to 1100 ºС. It is shown that М₆С-carbon intermetallide is a linear phase in terms of carbon on the solidus surface with the homogeneity range Fe_38,2–45,3Mo_47,5–40,4C_14,3 for metal components, within which the lattice parameters change from 1.1152(3) to 1.1072(8) nm. CALPHAD modeling shows that there are three-phase equilibria with participation of orthorhombic stabilized (Fe₃C)-cementite and monoclinic molybdenum Fe₂MoC-cementite: (γ-Fe) + (Fe₃C) + С, (γ-Fe) + (Fe₃C) + Fe₂MoC, (Fe₃C) + Fe₂MoC + С, Fe₂MoC + (Mo₂C) + C on the solidus besides the above-mentioned equilibria.