Abstract
This paper will discuss powder materials consolidation in the Si3N4 + Y2O3 system where full density has been achieved by liquid phase sintering. The role of the sintering additives during densification and their influence on structural properties will be reviewed. Room temperature strength is controlled by residual porosity over a wide range of phase composition and chemical content. Strength maintenance to elevated temperature is increased by the reduction of flux content in the liquid phase. Fluxes increase fluidity of the liquid phase and suppress its crystallization. Oxidation performance depends on the in situ oxidation characteristics of the minor phase composition and the influence of fluxes from the substrate which dissolve into the surface layer altering its oxygen diffusion rate. Turbine blades have been fabricated from this family of ceramics by injection molding. Final sintered densities >99% theoretical have been achieved with close dimensional control.
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