In the next generation vehicles for orbital flights, the configuration presently adopted by e.g. the Space Shuttle, characterised by blunt surfaces, will be substituted by sharp profiles,which reduce the aerodynamic resistance and allow the vehicle to manoeuvre during the landing phase . Such a favourable configuration has not been adopted up to now due to the very high temperatures (higher than 2200 K) caused by aerodynamic friction on sharp profiles; another aspect of paramount importance is that such high temperatures are reached in an oxidising environment. Moreover, reusability and maintainability are critical issues.
High temperature resistant ceramics, such as C/C and C/SiC, widely used in the realisation of space vehicles, cannot operate in a so critical application. As a consequence, a completely innovative class of materials, denominated UHTC (ultra high temperature ceramic) is under development [3,4]. UHTC are composite ceramics constituted of a matrix of borides (TiB2, ZrB2, HfB2) with a dispersion of carbide particles (e.g., SiC, ZrC, HfC). The most investigated composition is based on a ZrB2 matrix and a SiC particles dispersion (1540 vol.%). At high temperature, ZrB2 provides mechanical resistance, whilst SiC generates an oxidation protective scale on the material surface.
An innovative, proprietary methodology was developed to produce, by plasma spraying deposition, a ceramic composite containing SiC particles dispersed in a ZrB2 matrix . With such a technique both coatings and free standing parts were fabricated. In spite of the well known difficulty to obtain plasma sprayed coatings containing SiC, characterisation results evidenced that the used process did not affect the phase composition.
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