Group IVB carbonitrides

Tables I and 2 give a short overview of the properties important for technical applications of the most well characterized and important binary transition metal carbides and nitrides. Some specific properties which cannot easily be listed in a table, as well as the properties of transition metals carbonitrides) especially those of the most commonly used group ivb carbonitrides) are described in detail later.

Very interesting is the color change of the stoichiometric group ivb carbonitrides as a function of the [C]/([C] -I- [N]) ratio (Fig. 13). The higher number of the period the more the vivid violet color extends into the ternary region starting from the yellow colored nitrides. 

For the group IVB carbonitrides also data for well characterized f.c.c. phases exist [80]. The average linear thermal expansion (which is the linearized thermal expansion as a function of temperature) for the three carbonitrides is ... 

W. Lengauer, S. Binder, K. Aigner, Solid state properties of group IVb carbonitrides. Journal of Alloys and Compounds 217, pp 137-147, (1995)... 

W Lengauer, S Binder, K Aigner, P Ettmayer, A GuiUoiu, J Debuigne. Solid state properties of group IVb carbonitrides. J Alloys Compounds 217 137, 1995. 

A mixture of metallic, covalent and ionic components prevails in the bonding of transition metal carbides, nitrides, and carbonitrides. The metallic character is shown by the high electrical conductivities of these compounds. The bonding mechanism has been described extensively by a variety of approaches for calculating the density of states (DOS) and hence the electron density in f.c.c. transition metal carbides, nitrides, and oxides [11]. In the DOS of these compounds there is a minimum at a valence electron concentration (VEC) of 8, which corresponds to the stoichiometric composition of the group ivb carbides TiC, ZrC, and HfC. Transition metal carbides have a lower DOS at the Fermi level than the corresponding transition metal nitrides, hence the electrical properties such as electrical and thermal conductivity and the superconducting transition temperature, T, are lower than those of the nitrides. 

Because of the evident similarities between transition metal carbides and transition metal nitrides, carbon can be replaced completely by nitrogen in the IVB and VB group carbides, without changing the structure of the binary phases. Within the IVB-VIB group, only one ternary phase Cr2(C,N)2 has been reported [62]. Solid solubility in the VIB group carbonitride systems Cr-C N and Mo-C-N is not complete because in the boundary systems the crystal structures of the carbide and nitride phases are different. 

Transition metal carbide, nitride and carbonitride layers of the IVB group made by CVD (chemical vapor deposition) and PVD (physical vapor deposition) are produced in order to increase the service life of hardmetal tools [18,21,108] for cutting and milling operations. About 90% of cutting tools are coated. 

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