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Ceramic tubes made of aluminium oxide, sialon, and several commercial silicon carbides were exposed for about 500 h at 1200 to 1220 C to the combustion products from either No. 6 fuel oil or a mixture of 10% bituminous coal in No. 6 fuel oil (COM). After exposure to combustion products from No. 6 fuel oil, the linear thermal expansion at 1000 C for sintered ..gamma..chemically bond-SiC was 17% greater than it was before the experiment. For CVD SiC and siliconized SiC, there was no change. For alumina, it decreased by about 30%. When exposed to COM combustion products, the thermal expansion of the ..gamma..chemically bond-SiC increased slightly, and that of siliconized KT SiC increased by about 16% at 1000 C. Significant thermal expansion differences were observed between the upstream and downstream sides of the tubes for sintered ..gamma..chemically bond-SiC, the KT SiC, and the alumina. The strength after exposure for ..cap alpha..-SiC decreased by about 4%; the others remained unchanged. The helium permeability increased after exposure. The greatest increase occurred for tubes exposed only to residual fuel oil. 6 references. |
