BEHAVIOUR OF CF/ZRB2-SIC COMPOSITE PREPARED BY CERAMIC PREPREG METHOD IN HIGH ENTHALPY GAS FLOW

High-temperature ceramic materials Cf/ZrB2-SiC consisting of a refractory ZrB2-SiC matrix reinforced with continuous carbon fibres (Cf) are of intense interest as candidates for the development of next-generation thermal protection for propulsion systems designed to operate under extreme conditions of temperature, mechanical load, and aggressive gas flows. The focus of these studies is on the oxidative and ablative stability, which is crucial for the practical application of high-temperature materials. In the present work, high-temperature Cf/ZrB2-SiC composites were prepared by the ceramic prepreg method based on carbon fibre tow impregnation with ceramic slurry, formation of unidirectional ceramic ribbons, followed by their lay-up, pyrolysis, and silicon melt infiltration. The morphology and phase distribution over the volume of ceramic Cf/ZrB2-SiC composites have been studied by electron microscopy with energy-dispersive spectroscopy performed at different accelerating voltages. For the first time, the behaviour of such materials under the conditions of exposure to high-speed plasma flow at temperatures as high as 2100 °C has been investigated. Air pressure was 0.35 MPa, air flow rate was 6 m3/h. The composite demonstrates rather stable behaviour up to 2000 °C for 300 s. A comparative analysis of the composite microstructure before and after gas dynamic tests has been carried out. The phase and elemental composition, as well as the cross-sectional morphology of the composite, are determined. It is shown that the ablative stability of the composite is due to the formation of complex microstructure, in which several sublayers can be distinguished, and each of them prevents oxygen diffusion inside the composite. Temperature increase up to 2100 °C leads to a significant degradation of the composite. The obtained data can be used for further improvement of the composition of high-temperature composites suitable for the stable functioning of power system parts and units under extreme conditions.