Shrinkage Reduction in Silica-based Refractory Cores Infiltrated with Boehmite

Infiltration of silica‐based refractory cores with colloidal boehmite slurry has the effect of greatly reducing sintering shrinkage, as required for precision casting. Only 300 ppm of equivalent alumina is sufficient to decrease the shrinkage from RT to 1600°C more than three‐fold. Microstructural observations and XPS measures show that the silica grains are homogeneously coated with a reaction film which hinders viscous flow.