STRENGTHENING OF ALPHA-ALUMINA-CONTAINING PORCELAIN BODIES BY LAMINATION WITH DIFFERENT COMPOSITIONS

Strengthening of alpha-alumina-containing porcelain bodies was investi gated by lamination with different compositions by two techniques. One was coating technique, in which the test bars were dip-coated with sl urry of different batches, containing less amount of alpha-alumina. Co ating caused an increase in bending strength of 24% with adequate coat ing thickness. Nevertheless, a formation of a crack at the surface led to a decrease in strength remarkably if the surface layer exceeded a critical thickness. The other was ''double slip casting'' technique, l aminated bodies were made from two batches designated as surface and i nternal layers by sequential slip casting. Double slip casting yielded thick surface layer without any crack, thus substitution of zircon fo r alumina at the surface layer increased the mean bending strength fro m 38 to 44 kgf/mm2 and Weibull modulus from 6 to 17.