Carbonitride

Mixed compound of a carbide and a nitride of the same element, for example niobiumcarbonitride (NbC, NbN) or vanadium-titaniumcarbonitride (Ti(C,N)VC, VN) (Fig. 1).

Commercial production of carbonitrides is performed in vacuum furnaces by carbo-thermal reduction and nitriding of titanium oxide at high temperatures. Subsequent grinding ensures the required grain distribution. The powder produced by this patented procedure has a spherical morphology and particularly narrow grain distribution in contrast to titaniumcarbonitride (Ti(C,N)), which is made of titanium metal.

Titanium carbonitrides are the base material for production of cermets, a metal-ceramic composite similar to hard metals, with great hardness, good resistance against oxidation and excellent wear resistance providing appropriate toughness. Cermets are used in tools for machining of metals. In the same way as the conventional WC-Co hard metals, cermets also require special additives, such as molybdenum carbide (Mo2C), TaC, NbC, and in special cases also WC. These additives can also be produced in the form of solid solution mixed crystals using titaniumcarbonitride.

In combination with Al2O3, Ti(C, N) makes for extremely robust and wear resistant cutting ceramics, for example used for machining of cast iron.

 

  • Fig. 1: Titanium-vanadium carbonitrides appearing gray and raised, 300:1, etched using HNO3, interference contrast, oblique illumination; the small black inclusions are sulfides
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