High-Temperature Corrosion Of Aln-Based Composite Ceramic In Air And In Combustion Products Of Commercial Fuel. I. Corrosion Of Ceramic Composites In The AlN - SiC System In Air And In Combustion Products Of Kerosene And Diesel Fuel

• Published in: Powder metallurgy and metal ceramics 2004-03, Vol.43 (3-4), p.179-186
• Main Authors: Lavrenko, V A, Baxter, D J, Panasyuk, A D, Desmaison-Brut, M
• Format: Article
• Language: English
• ISSN: 1068-1302
• DOI: 10.1023/B:PMMC.0000035707.58363.f5

We have established that scale formed upon oxidation of ceramic composites in the AlN - SiC system in air at temperatures up to 1550 deg C contains mullite 3Al2O3 * 2SiO2 as the major phase of the outer layer, which provides its high protective properties. The inner layer of the scale contains beta-SiO2, alpha-Al2O3, and a fairly small amount of the oxynitride Al10N8O2. In dry air, even at 1500 deg C with a long holding time (50 h), material of 50 mass% AlN - 50 mass% SiC retains extremely high corrosion resistance. We have shown that upon prolonged (up to 240 h) oxidation of the indicated ceramic in the combustion atmosphere of S- and Na-containing fuels (kerosene and marine diesel fuel) at 1200-1300DGC, along with mullite in the scale we see formation (due to reaction of beta-cristobalite with Al2O3 and gaseous Na2O and NaOH) of low-viscosity silicate glass Na2SiO3 and NaAlSiO4. Together with impurity Fe2O3 and gaseous Na2SO4, it partially destroys the protective mullite layer and leads to degradation of the protective properties of the scale.