Ternary transition metal carbides

Holleck, H., Ternary Carbide Systems of Actinoids wifli Transition Metals of Other Groups (in German), in Binary and Ternary Transition Metal Carbide and Nitride Systems , Petzow, G. (Ed.) Gebraeder Bomtraeger Berlin, Stuttgart, 92-111 (1984) (Crys. Structure, Phase Diagram, Phase Relations, Review, 91)... 

Because of the evident structmal similarities between transition metal carbides and transition metal nitrides the carbon atoms in group 4 and 5 carbides can be replaced completely by nitrogen without changing the structme of the binary phases. So far only one distinct ternary phase Cr2 (C,N)2 has been reported. Intersolubihty between the binary nitrides and carbides in the group 6 carbonitride systems Cr-C-N and Mo-C-N is not complete because of the differences in the crystal structmes of the carbide and nitride phases. 

Upon additional alloying ternary carbonitrides quaternary carbonitrides are obtained. The group 4 and 5 transition metal carbides and nitrides are completely miscible except TiN-VC and ZrN-VC. Thus, modified material properties can be obtained (see also Section 9.2). Information on the properties of these carbides are still scarce," a few data are given in Figure 13 and Table 4. 

Ternary phases with structures different from those of the phases of the binary boundary systems are more the exception than the rule. Such phases have been reported in the systems Nb-Mo-N, Ta-Mo-N, Nb-Ta-N, Zr-V-N, Nb-Cr-N, and Ta-Cr-N. Information about ternary transition metal-nitrogen systems is often available for specific temperatmes only. This is even more the case for quaternary nitride systems, which play a role in the production of carbonitride cermets where quaternary compounds of the types (Ti,Mo)(C,N) and (Ti,W)(C,N) are of interest (see Carbides Transition Metal Solid-state Chemistry), as well as in layer technology where titanium nitride-based coatings of the type Ti(C,B,N) are prepared by magnetron sputtering. Layers consisting of ternary compounds of the type (Ti,Al)N and (Ti,V)N also have favorable properties with respect to abrasion resistance. 

In a similar multiphase system, transition metal carbides were used as additives for pressureless sintering of TiB2, yielding composites of binary and ternary borides [218,296]. Attrition milled powder mixtures of TiB2 with 3-10 mass-% Co or Ni and 20-35 mass-% WC have been sintered in a vacuum at temperatures between... 

The effects on the properties of transition metal carbides and nitrides produced by metal sublattice doping have been studied for quite an extended period. So far, large groups of ternary (and more complex) carbide and nitride alloys of the M M i (C,N) type, where M, M are metals, have been synthesised (see Goldschmidt (1967) or Samsonov, Upadkhaya and Neshpor (1974)). In this chapter we review the results of researches on the electronic structure and interatomic bonding in such solid solutions. 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

Complex Carbides. Complex carbides are ternary or quaternary intermetaUic phases containing carbon and two or more metals. One metal can be a refractory transition metal the second may be a metal from the iron or A-groups. Nonmetals can also be incorporated. 

Finally, numerous ternary metal carbides containing Ln metals, transition metals, and discrete Q units are also well established.35 In many such carbides the C—C distance are in the range 1.32 to 1.47 A and have been described as double bonds. Thus, they are formally derivatives of the ethyl-enic tetraanion Q", e.g., Ln3M(Q)2 (M = Fe, Co, Ni, Ru, Rh, Os, and Ir). The Q units can bind to the transition metal atoms in a 1,1 (7-IVa),... 

There are several families of ternary carbide phases with transition metals and main gronp elements. Several of them are of structnral interest snch as the H-phases, the filled /3-manganese type carbides and the /c-carbides. The rj-phases are formed in carbon-deficient hardmetals and canse embrittlement. 

Ternary systems between two different metal atoms and carbon containing mostly Fe with minor amounts of transition metals are used as structural materials alloys of the transition carbides, mainly WC, containing Co, Fe or Ni as a binder, are used as cutting tools and wear-resistant surfaces and alloys between the various actinide carbides or the transition metals are used as nuclear fuel. 

Mi) Actinide-Metal Group. Alloys of U-Pu-C and U-Zr-C can be used as a nuclear fuel. Both systems are characterized by extensive mutual solubility and no ternary compounds. However, U forms ternary carbides with several transition metals to give the compound UMCj, where M = Mo, W, Re, Rh, Ir, Mn, Cr, Ni, Co, Fe or Tc. 

The reaction of ternary carbides with nitrogen has attracted interest because of a novel type of phase separation occurring in double pseudobinary solid solutions of transition-metal multicomponent carbonitrides. Rudy has investigated the system Ti-Mo-C-N and has found that the homogeneous solid solution (Ti, Mo) (C, N), formed at high temperatures, disproportionates into two phases, both of which are isostructural and have nearly the same lattice parameters. One of the two phases is a Ti carbonitride rich in N and poor in Mo, the other is a Ti-Mo carbide rich in Mo hut poor in N. This type of disproportionating is bound to occur in most of the double-pseudobinary carbonitride systems... 

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