Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high-temperature furnaces and heat transfer surfaces that can operate at temperatures much higher than those prevalent in current cod-fired power plants. The combination of elevated temperatures and hostile combustion environments requires the development and application of advanced ceramic matertals in these designs. The objectives of the present program are to evaluate the (a) chemistry of gaseous and condensed products that artse during combustion of coal; (b) corrosion behavior of candidate materials in air, slag, and salt environments for application in the combustion environments; and (c) residued mechanics properties of the materials alter corrosion. The program emphasizes temperatures in the range of 1000- 1400°C for ceramic materfals and 600- 1000°C for metallic alloys. Coal/ash chemistries developed on the basis of thermodynamic/ldnetic calculations, together with slags from actual combustors, are used in the program. The materials being evafuated include monolithic silicon carbide from several sources: silicon nitride, silicon carbide in alumina composites, silicon carbide fibers in a silicon carbide-matrix compoosite and some advanced nickelbase alloys. The paper presents results from an ongoing program on corrosion performance of candidate ceramic materials exposed to air, salt, and slag environments and their effect on flexural strength and energy absorbed during fracture of these materials.
Keywords: corrosion, ceramics, coal ash, silicon carbide, mechanical properties, thermodynamics