The Phase Diagram of the System Titanium—Molybdenum—Carbon

Abstract

The phase diagram of the boundary system Mo-C has been redetermined at high carbon contents. A higher carbide of molybdenum (cubic, NaCl type of lattice, homogeneity range 37–40 at.% C) has been found to form by a peritectic reaction at 2560°C; at 2000–2200°C this undergoes a polymorphic transformation into the low-temperature hexagonal form, which subsequently, at 1630°C, decomposes into the lower carbide and carbon. A phase transformation occurs in the lower carbide of molybdenum at 1170°C. The phase diagram of the ternary Ti-Mo-C system has been determined. Its principal features are: the system is divided into two triangles by the Mo-TiC section; the cubic carbides of molybdenum and titanium form a continuous series of solid solutions; at low temperatures titanium stabilizes the phase based on the higher hexagonal carbide of molybdenum.