Casting of reactive metals into ceramic molds

The process of coating a foundry mold with a coating comprising, the foundry mold material being reactive with reactive metals and alloys, comprising

• applying to at least the surfaces of said foundry mold which come into contact with said reactive metals or alloys, a composition consisting essentially of
• a refractory material selected from the group consisting of yttrium oxide, zirconium oxide, fused yttrium oxide, fused zirconium oxide, fused stabilized zirconium oxide, and fused mixtures of zirconium oxide and yttrium oxide;
• and a sufficient amount of an yttria sol binder.

A cast ceramic core having a configuration around which the metal is cast to form the desired molded article, said core consisting essentially of a refractory material selected from the group consisting of yttrium oxide, zirconium oxide, fused yttrium oxide, fused zirconium oxide, fused stabilized zirconium oxide, and fused mixtures of zirconium oxide and yttrium oxide;

• and a sufficient amount of an yttria sol as a binder.

A process for making a refractory article having low reactivity with reactive metals consisting essentially of providing an yttria sol, mixing said sol with a refractory material selected from the group consisting of yttrium oxide, zirconium oxide, fused yttrium oxide, fused zirconium oxide, fused stabilized zirconium oxide, and fused mixtures of zirconium oxide and yttrium oxide to form a coating composition, applying at least one coating of said coating composition to a surface object shaped in the desired configuration, heating the resulting coated surface object to a sufficiently high temperature to melt or burn out the material of the surface object, thereby sintering said coating composition into the desired shape.

A process for making a refractory article having low reactivity with reactive metals consisting essentially of providing an yttria sol, mixing said sol with a refractory material selected from the group consisting of yttrium oxide, zirconium oxide, fused yttrium oxide, fused zirconium oxide, fused stabilized zirconium oxide, and fused mixtures of zirconium oxide and yttrium oxide;

• to form a coating composition, applying a first coating of said coating composition to a surface body shaped in the desired configuration, and thereafter applying at least one second coating of a refractory to said surface body having the first coating thereon, heating the resulting coated body to a sufficiently high temperature to melt or burn out the body material, thereby sintering said coating composition into the desired shape.

A process for making a ceramic core comprising coating the inside of a core mold with a slurry consisting essentially of yttria sol and a refractory material, and before the coating is dry, applying thereto finely divided refractory and permitting the coating to dry, thereafter applying to the coating a mixture of a refractory and a binder therefor and permitting this mixture to gel to form a core, thereafter removing the core from the mold and firing said core at a sufficiently high temperature to bond the coating and the silica refractory.

A process for casting a reactive metal in a mold having low reactivity with reactive metals consisting essentially of providing a yttria sol,

• mixing said sold with a refractory material to form a coating composition,
• applying said coating composition to a pattern shaped in the desired configuration, allowing the coating to gel, heating the resulting coated pattern to a sufficiently high temperature to melt or burn out the pattern material, thereby sintering said coating composition into the desired shape, thereafter casting said metal size into the mold.