Chemical deposition process for coatings: the problems of mass and heat transfer

Abstract

The known variants of deposition of thermal barrier coatings (TPC) of ZrO2-Y2O3 by the MO CVD method are analyzed. It is established that the use of this method in principle allows obtaining ceramic coatings with the required columnar structure, low thermal conductivity and technologically acceptable growth rates. It is shown that the main limiting factor in the coating growth rate is the productivity of the precursor vapor sources used. The analysis of known variants of realization of heat and mass transfer at the use of various precursors with a wide range of thermal parameters for the given process is carried out. The results of experimental studies and numerical modeling of the kinetics of sublimation of a number of precursors in the flow of an inert gas Ar, He or their mixtures in a given range of temperatures and gas flow rates are obtained. It is established that when sublimating a single precursor particle under forced convection, the mass transfer intensity of a given compound in the helium stream is several times greater than mass exchange in argon with other closely related parameters, such as the flow velocity and the temperature of the oncoming flow. At the same time, the temperature of the particle is lowered, which can be an important factor in increasing the thermal stability of the vapors. It is shown that there is an additional possibility to control the sublimation of the precursor with the Ar/He mixture.