Alum Shiji ¦Â-sialon-al <sub> 2 </ Sub> O <sub> 3 </ Sub>-sic Composite Material Preparation, Properties And Microstructure

The preparation, high temperature properties and microstructure of bauxite based β-Sialon/Al₂O₃/SiC composites have been investigated detailedly in this paper.Bauxite based β-Sialon bonded corundum/SiC composites have been prepared by nitridation reaction method at 1500℃ for 5 hours, using fused corundum and SiC grains and bauxite, Al and Si fines as starting materials. The main crystal phases of composites are corundum and SiC, bond crystal phase is β-Sialon; The bulk density, porosity, room temperature MOR, CCS are 2.7g/cm³, less than 22%, more than 17MPa, 60Mpa respectively.The HMOR, Stress-Strain and high temperature bending creep properties have been studied by three points bending method, it shows that the HMOR-T curves are very similar to the I curve, MOR increases with temperature rise up to 1000℃, after which, it decreases very slowly, HMOR at 1400℃ is higher than that at room temperature; Stress-stain indicates that the composites present elastic deformation before 600 ℃ and elastic modulus is more than 10000MPa, after that, it is plastic deformation; The creep active energy is about 220kJ/mol and stress index factor is close to 1, the creep mechanism is diffusion creeping controled by crystal boundary diffusion.Studies on Thermal Shock Resistance by water-cooling show that the critical temperature is 600℃ and the residual strength holding ratio is more than 50% at 1300 ℃. Which indicates that the β-Sialon/Al₂O₃/SiC composites possess excellent thermal shock resistance.The results of isothermal oxidation show that the initial oxidation temperature of composites is about 800 ℃; The results of non-isothermal oxidation indicate that the oxidation type is protected oxidation, the oxidation process is composed of three stages, i.e. initial stage(before 20min), intermediate stage(during 20min to 2 hours) and final stage(after 2hours); Glass coating with 0.4mm thickness can be observed on the surface of the oxidized samples, compact oxidation layer with 0.8mm thickness is found under the glass coating.Studies on slag corrosion by static crucible method shows that the thickness of slag corrosion layer is about 2mm, the penetrative depth is about 5⁹mm, and penetrative rate increases with time following conics equation, the penetrative depth of the slag in the composites decreases with Sialon content increasing; Erosion products are MgAl₂O₄ and...