Corrosion And Its Effect On Mechanical Properties Of Materials For Advanced Combustion Systems PDF Download

Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high temperature furnaces and heat transfer surfaces capable of operation at much elevated temperatures than those prevalent in current coal-fired power plants. The combination of elevated temperatures and hostile combustion environments necessitate development/application of advanced ceramic materials in these designs. The present paper characterizes the chemistry of coal-fired combustion environments over a wide temperature range of interest in these systems and discusses preliminary experimental results on several materials with potential for application in these systems. An experimental program has been initiated to evaluate materials for advanced combustion systems. Several candidate materials have been identified for evaluation. The candidates included advanced metallic alloys, monolithic ceramics, ceramic particulate/ceramic matrix composites, ceramic fiber/ceramic matrix composites, and ceramic whisker/ceramic matrix composites. The materials examined so far included nickel-base superalloys, alumina, stabilized zirconia, different types of silicon carbide, and silicon nitride. Coupon specimens of several of the materials have been tested in an air environment at 1000, 1200, and 1400°C for 168 h. In addition, specimens were exposed to sodium-sulfate-containing salts at temperatures of 1000 and 1200°C for 168 h. Extensive microstructural analyses were conducted on the exposed specimens to evaluate the corrosion performance of the materials for service in air and fireside environments of advanced coal-fired boilers. Additional tests are underway with several of the materials to evaluate their corrosion performance as a function of salt chemistry, alkali vapor concentration, gas chemistry, exposure temperature, and exposure time.