THE TI-MO-C-N SYSTEM - STABILITY OF THE (TI,MO)(C,N)(1-X) PHASE

The hard constituents in cermet cutting tools are based on titanium ca rbonitride, mostly with additions of molybdenum and tungsten carbides and usually other carbides such as TaC, NbC, ZrC,VC, etc. In order to gain insight into the typical cermet ''core-rim'' structure, the Ti-Mo -C-N system was investigated in the region of the (Ti,Mo)(C,N)(1-x) ph ase. Specific experiments were performed: (Ti,Mo)(C,N)(1-x) samples we re annealed in nitrogen atmosphere and substoichiometric (Ti,Mo)C-1-x as well as (Ti,W)C-1-x were subjected to nitriding treatments. Althoug h complete equilibrium may not have been reached in any of these exper iments, they showed that the phase separation may occur at substoichio metric compositions but probably not at high nitrogen activities.