High Temperature Behavior of Plasma Sprayed ZrB₂-SiC Composite Coatings

ZrB₂-SiC composites are considered a class of promising materials for aerospace applications such as nose and leading edges of re-entry vehicles. Results on such materials obtained by hot isostatic pressing have confirmed their high resistance to the oxidation at temperature up to 2000°C. Ongoing work has shown that such materials can be obtained in the form of coatings by means of Plasma Spraying techniques. On this regard, the most critical aspect was correlated to the decomposition of the SiC phase at a temperature quite lower than the melting point of ZrB₂. Experimental evidence indicated that such decomposition can be avoided when a proper methodology of preparation of the starting powders is adopted, and if suitable thermal spraying parameters are selected. In any case, high temperature oxidation testing (up to 1800°C) confirmed the outstanding behaviour of this materials obtained by plasma spraying. This paper is focussed on preliminary studies of oxidation behaviour for plasma sprayed ZrB₂-SiC composites suitable for thermal protection shields.