VANADIUM OXI-CARBIDE COATINGS DEPOSITED BY OMCVD IN AN ISOTHERMAL REACTOR

This paper reports on the influence of both the vaporization mechanism and gaseous transport phenomena, on the properties of vanadium oxi-ca rbide coatings. In order to study the influence of the residence time of the gaseous mixture on the properties of the deposited layer, a spe cific device has been built. In this device the temperature of the rea ctor wall is very accurately controlled to the vaporization temperatur e of the precursor by a heat pipe disposed inside a furnace, whereas t he temperature of the substrate is imposed independently. A vacuum-tig ht sliding device allowed varying the length between the vaporization crucible and the deposition substrate. A complete factorial design wit h three factors and two levels, was carried out for two characteristic vaporization temperatures of the precursor. We studied the influence of three parameters on the thickness and composition of the deposits: the substrate temperature, the hydrogen flow rate, and the distance be tween the vaporization crucible and the steel substrate.