In this work, a low-temperature melting composition located within the glass-forming region of the Y 2 O 3 -Al 2 O 3 -SiO 2 (YAS) system is proposed and tested as a protective coating for SiC ceramics. Glassy coatings 197 µm thick were obtained by flame spraying YAS granules on SiC substrates that had been grit blasted and coated with a Si bond layer. Bulk glasses of the same composition were also produced for use as a reference material. The hardness, elastic modulus, and thermal conductivity of the coatings and bulk specimens were evaluated and compared and the effect of heat treatment was investigated. Crystallization occurred in both the bulk glass and coating during isothermal treatments in air at 1100-1350 °C, but it did not compromise system integrity due to crack healing.

A new type of thermal barrier coating (TBC) based on metal-glass composite (MGC) has been recently presented. Beside the availability of conventional manufacturing routes of the coating, e.g. by vacuum plasma spraying (VPS) or slip casting, there are two main advantages of the new TBC: The thermal expansion coefficient can be easily adjusted to the substrate by changing the metal to glass ratio of the composite and the severe oxidation of the bondcoat layer can be reduced due to the gastightness of the glassy phase. Nevertheless, oxidation of the metal phases cannot be fully suppressed up to now. Concepts for a multilayer system and an improved oxidation resistance of a MGC based on suitable heat treatments and on alternative glass compositions have been developed. Results from isothermal oxidation experiments and from thermal cycling in burner rig facilities will be discussed.