Abstract
To obtain Zirconium Carbide (ZrC) coating with columnar structure, which is optimal for resistance to heat shocks, chemical vapor deposition was used. Three series of multi-steps were carried to decrease the degree of supersaturation of active [C]: reducing concentration of C3H6, substituting C3H6 by lower-carbon-content hydrocarbons and the last increasing the flow rate of H2. Scanning electron microscopy show the morphology evolution of ZrC coatings from two-dimensional platelets, to fine grains, to polycrystals with different shapes and to columnar with domed tops. When the flow rate of H2 reach maximum (0.3m3/h), the columnar grains have a width of 1-2μm and a preferred orientation of (220). It is regarded as the change of limiting step of active [C] involving the reaction of formation of ZrC is the key factor for evolution.
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