Ceramic shell mold

Claim 2

In a method for making a shell mold which comprises: a. making an expendable pattern of a part to be cast, b. dipping the expendable pattern into a slurry of a refractory material and a binder to form a moist coating on said pattern, c. sprinkling a coarse refractory powder on said moist coating, d. drying said moist coating, and e. repeating steps b, c and d, whereby said shell mold is built up to a desired thickness, the improvement wherein said binder consists essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica and said binder developing excellent green strength.

Claim 3

The method according to claim 1 wherein the fibrous alumina is acid stabilized at a pH of about 3.0 to 4.5.

Claim 4

The method according to claim 1 wherein the refractory material comprises one or more of quartz, fused silica, monoclinic zirconia, stabilized electrically fused zirconia, mullite, aluminosilicates, calcined alumina, fused alumina, ceria or yttria.

Claim 5

The method according to claim 1 wherein the refractory material comprises one or more of alumina, zirconia or yttria.

Claim 6

The method according to claim 1 wherein the shell mold comprises two coats of refractory, each coat being bonded with said colloidal alumina binder and said shell mold being supported by a solid mold structure.

Claim 7

The method according to claim 1 wherein the shell mold comprises one coat of refractory, said coat being bonded with said colloidal alumina binder and said shell mold being supported by a solid mold structure.

Claim 8

The method according to claim 1 wherein the shell mold comprises one coat of refractory bonded with colloidal alumina being supported by an additional shell structure employing a different binder than said alumina.

Claim 9

The method according to claim 1 wherein the expendable pattern is a wax pattern.

Claim 10

The mold produced by the method of claim 1.

Claim 11

In a method for producing castings of alloys having directionally solidified grains wherein a molten alloy is poured into a shell mold, the improvement which comprises employing as the shell mold one produced by a method comprising: a. making an expendable pattern of a part to be cast, b. dipping the expendable pattern into a slurry of a refractory material and a binder to form a moist coating on said pattern, c. sprinkling a coarse refractory powder on said moist coating, d. drying said moist coating, and e. repeating steps b, c and d, whereby said shell mold is built up to a desired thickness, said binder consisting essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 12

In a method for producing castings of alloys having directionally solidified grains wherein a molten alloy is poured into a shell mold, the improvement which comprises employing as the shell mold one produced by a method comprising: a. making an expendable pattern of a part to be cast, b. dipping the expendable pattern into a slurry of a refractory material and a binder to form a moist coating on said pattern, c. sprinkling a coarse refractory powder on said moist coating, d. drying said moist coating, and e. repeating steps b, c and d, whereby said shell mold is built up to a desired thickness, said binder consisting essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 13

The method according to claim 10 wherein th alloy comprises nickel and cobalt and one or more of hafnium, zirconium, tungsten, aluminum, titanium, niobium, molybdenum, carbon, silicon, manganese or yttrium.

Claim 14

The method according to claim 11 wherein the alloy comprises nickel or cobalt and one or more of zirconium, aluminum or titanium.

Claim 15

The method according to claim 10 wherein the mold is heated to 2000° F. to 3100° F. prior to pouring the molten alloy therein.

Claim 16

The method according to claim 10 wherein the mold is heated to 2750° F. to 3100° F. prior to pouring the molten alloy therein.

Claim 17

The method according to claim 10 wherein the refractory comprises one or more of alumina, ceria, zirconia and yttria.

Claim 18

In method for casting an alloy comprising pouring a molten alloy in a shell mold, the improvement which comprises forming the shell mold from a slurry of binder and a refractory material, wherein said binder consists essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 19

In method for casting an alloy comprising pouring a molten alloy in a shell mold, the improvement which comprises forming the shell mold from a slurry of binder and a refractory material, wherein said binder consists essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 20

The method according to claim 16 wherein the mold is preheated to an elevated temperature prior to pouring molten alloys therein.

Claim 21

The method according to claim 17 wherein the mold is heated to 2000° to 3100° F. prior to pouring the molten alloy therein.

Claim 22

The method according to claim 17 wherein the mold is heated to 2750° F. to 3100° F. prior to pouring the molten alloy therein.

Claim 23

The method according to claim 16 wherein the refractory comprises one or more of alumina, ceria, zirconia and yttria.

Claim 24

In a method of making a shell mold refractory coating comprising dipping a pattern into a slurry of binder and a refractory material, the improvement wherein said binder consists essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 25

In a method of making a shell mold refractory coating comprising dipping a pattern into a slurry of binder and a refractory material, the improvement wherein said binder consists essentially of an acid stabilized, fibrous colloidal alumina as an aqueous sol, said binder being essentially free of silica, and said binder developing excellent green strength.

Claim 26

The shell mold produced by the process of claim 21.