Protection against oxidation, by CVD or SPS coatings of hafnium carbide and silicon carbide, on carbon/carbon composites
September 17-20, 2017
protection of carbon/carbon composites against oxidation at high temperatures. However HfC and most of metallic carbides present a non stoechiometric composition with carbon vacancies. As a consequence, the oxidation resistance is poor at low temperatures (500-1000°C). In order to overcome this main drawback the HfC can be associated with silicon carbide (SiC) presenting a better oxidation resistance at lower temperatures.
Two coating routes have been studied; the first one is the Chemical Vapour Deposition which enables to obtain very thin coatings and the second one is the Spark Plasma Sintering technique which permits to get new microstructures of coatings.
On first hand, this study describes the CVD conditions for the deposition of HfC from the metallic hafnium pellets to get hafnium chlorides followed by the reduction of the chlorides by H2 and the deposition of HfC with the methane as carbon precursor. This enables to get an alternated multilayer microstructure made of a first layer of SiC on top of which the first layer of HfC is deposited and so on to a ten alternated layer deposit .
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Alexandre Allemand, S Jacques, Y Le Petitcorps, O Szwedek, and C Verdon, "Protection against oxidation, by CVD or SPS coatings of hafnium carbide and silicon carbide, on carbon/carbon composites" in "Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications IV", Jon Binner, The University of Birmingham, Edgbaston, United Kingdom Bill Lee, Imperial College, London, United Kingdom Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/uhtc_iv/22