Thermodynamic modeling and preparation of hafnium carbide coatings in the hafnium–carbon–fluorine system

Thermodynamic modeling of the Hf–C–F system has been carried out in wide temperature and pressure ranges. Analysis of the calculated molecular composition of the vapor phase in equilibrium with Hf + HfC and the vapor phase in equilibrium with C + HfC has shown that the chemical vapor transport of hafnium under isothermal conditions is mediated by lower hafnium fluorides. The content of the lower hafnium fluorides increases with increasing temperature and decreasing total pressure in the system. Reactive hafnium carbide deposition on a carbon material, with CF4 as a transport agent, has been studied experimentally. The coating obtained in this way is sufficiently dense and consists of hafnium carbide nanocrystals ranging in size from 100 to 200 nm.