Carbon – Molybdenum – Titanium

Abstract

The knowledge of phase relations in the C-Mo-Ti system is very important for several advanced materials, especially for high temperature and wear resistant applications. Main attention is given to the behavior of the B1 type TiC carbides and the MoxC carbides, which strongly influence the properties of industrial materials. Molybdenum alloys are very important candidate materials for such applications because of their high melting point, high thermal conductivity, low sputtering yields etc. On the other hand, there are problems with their mechanical properties at low temperatures (radiation embrittlement). The addition of TiC can significantly improve the low-temperature ductility after irradiation [2005Kit], which strongly improves the practical value of the alloy. TiC based cermets are another important class of materials, used as possible substitutes for the widely used WC-Co based hard metals for cutting applications. They have lower toughness in comparison with the latter, but better wear resistance and high-temperature properties. The presence of Mo improves the properties of such alloys thus increasing the need for detailed information about the phase diagram of C-Mo-Ti system. The first study of the C-Mo-Ti system was an isothermal section at 1710°C published by [1956Alb], which appeared later in the review by [1961Eng], but no new phase diagram data were published here. The quasibinary section of the diagram was described by [1963Ere], [1968Zak, 1969Zak, 1970Zak] studied the Mo rich part of the phase diagram, but the most detailed study of this system was published by [1969Rud, 1970Rud], who studied the liquidus surface and selected isothermal and temperature-composition sections. Other phase diagram sections were also published by [1969Ere, 1970Zak, 1970Ere1, 1970Ere2]. The overviews of experimental results were published by [1981Hol, 1984Hol, 1994McH, 1999Ban], in particular, [1985Ere] gave a comprehensive review of experimental work to date, including their own studies. The review comprised a number of isothermal sections, vertical sections, solidus and liquidus surfaces and a reaction scheme. The theoretical study of C-Mo-Ti system was carried out by [1990Vel], and full assessment of this system was published by [1996Shi], based on the above mentioned experimental results. A general overview of crucial features of the C-Mo-X (X = Ti, W, Ta etc.) phase diagrams was published by [1974Vel, 1988Vel1], nevertheless, no detailed phase diagrams are shown in these two papers. Details of experimental works on the phase equilibria, crystallography and thermodynamics of the ternary C-Mo-Ti system are listed in Table 1. Several authors e.g. [1936Mol, 1972Sam1, 1972Sam2, 1975Sam, 1977Tre, 1979Shu, 2002Kou, 2005Kit] studied material properties of the C-Mo-Ti system, especially with respect to the properties of carbide phases in the Mo-TiC alloys (see Notes on Material Properties and Miscellaneous).