Silicon Carbide Whiskers Reinforced Alumina Coatings on SiC-SiC Composites

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This Small Business Innovation Research Phase I project describes a unique way to produce adherent, improved thermal shock resistance coatings on SiC-SiC composites. Silicon carbide is being evaluated for industrial heat exchanger applications. High temperature use of SiC ceramics in corrosion environments is limited to about 1200ÝC in heat exchanger applications. Several attempts were made to apply a protective alumina external layer over the SiC substrate. Thermal mismatch between alunina and SiC made it impossible to obtain adherent alumina coatings on SiC substrate. Providing strong-adherent whiskers are growing-off the substrate, the subsequent deposition of alumina coatings will result in a formation of adherent, increased toughness, and thermal shock resistant alumina coating. Thermomechanical properties of the SiC-reinforced alumina coating will be dependent on the whiskers as well as alumina coating properties. Tailoring of whiskers properties and coating microstructure will be performed in order to obtain adherent alumina coatings on SiC substrates, capable of surviving thermal cycling up to 1400ÝC.