A ceramic casting shell is formed by a method comprising the steps of coating a wax former with one or more layers of a ceramic slurry; drying the or each layer of ceramic slurry; wherein the dried layer or layers of ceramic slurry form a ceramic shell; applying over the ceramic shell, a coating of a polymer material; heating the formed assembly to melt and remove the wax former, wherein the polymer coating acts as a strengthening layer to the ceramic shell during the wax removal process; and subsequent to removal of the wax former, heating the ceramic shell to melt and remove the polymer coating. The polymer coating is preferably the outer coating of the ceramic shell. The polymer coating may be applied by spraying, dipping or painting onto the ceramic shell.

A casting slurry for producing shell molds for casting parts includes a metal alloy, the slurry includes powder particles and a binder, the binder includes colloidal yttrium oxide, and the powder particles includes calcia-stabilized zirconia.

A mullite shell mold for casting includes a facecoat layer containing ceramic flour. The mullite shell mold also includes a first layer disposed on the facecoat layer. The first layer can contain sintered ceramic media. The facecoat layer and the first layer can each contain less than 1 wt % crystalline silica.

A powder binder product for use in making a slurry for investment casting molds comprising Nano-sized powders; and an organic polymer powder, wherein it does not require aqueous colloidal silica to produce slurries used to build investment casting molds. The Nano-sized powders comprise fumed alumina, boehmite, fumed silica, or fumed titanium oxide or combinations thereof. The coarse refractory powder, combined with the powder binder for mold manufacture, comprises milled zircon, tabular alumina or fused alumina, fused silica, alumino-silicate, zirconia, and yttria or combinations thereof. The organic polymer in a powder binder comprises a cellulose-based material. A powder investment casting binder, that once fired, consists of up to 96 weight percent aluminum oxide.

A composition which comprises a soluble or partially soluble phosphate, a refractory material and less than 1% of an oxide or hydroxide of magnesium or calcium. The composition may be mixed with water to form an investment casting slurry into which a wax pattern may be dipped. Slurry coated onto the pattern may be set by applying a stucco composition which comprises an oxide or hydroxide of magnesium or calcium. Coats of set slurry may be built up on the pattern to form an investment casting shell.

The invention concerns a method of manufacturing a shell mould (1) with several layers (2, 3, 4, 5), including at least one contact layer (2), from a model (6) of wax or other similar material of a part to be manufactured, the method comprising a step of dipping the model (6) into a contact slip forming the contact layer (2) and comprising an inorganic or organic binder and a powder, wherein the powder is a mullite-zirconia composite.

Various embodiments of making an investment casting mold are disclosed. The method includes coating a sacrificial pattern with a prime layer that includes a first refractory slurry and a first refractory stucco; at least partially hardening the prime layer; and coating the prime layer with an intermediate layer that includes a second refractory slurry and a second refractory stucco. The method further includes at least partially hardening the intermediate layer; coating the intermediate layer with a first backup layer that includes a first thixotropic agent, the first thixotropic agent including a first polymer emulsion; coating the first backup layer with a second backup layer that includes a second thixotropic agent, the second thixotropic agent including a second polymer emulsion; and at least partially hardening the first backup layer and the second backup layer.

A powder binder product for use in making a slurry for investment casting molds comprising Nano-sized powders; and an organic polymer powder, wherein it does not require aqueous colloidal silica to produce slurries used to build investment casting molds. The Nano-sized powders comprise fumed alumina, boehmite, fumed silica, or fumed titanium oxide or combinations thereof. The coarse refractory powder, combined with the powder binder for mold manufacture, comprises milled zircon, tabular alumina or fused alumina, fused silica, alumino-silicate, zirconia, and yttria or combinations thereof. The organic polymer in a powder binder comprises a cellulose-based material. A powder investment casting binder, that once fired, consists of up to 96 weight percent aluminum oxide.

The invention concerns a method of manufacturing a shell mould (1) with several layers (2, 3, 4, 5), including at least one contact layer (2), from a model (6) of wax or other similar material of a part to be manufactured, the method comprising a step of dipping the model (6) into a contact slip forming the contact layer (2) and comprising an inorganic or organic binder and a powder, wherein the powder is a mullite-zirconia composite.

Various embodiments of making an investment casting mold are disclosed. The method includes coating a sacrificial pattern with a prime layer that includes a first refractory slurry and a first refractory stucco; at least partially hardening the prime layer; and coating the prime layer with an intermediate layer that includes a second refractory slurry and a second refractory stucco. The method further includes at least partially hardening the intermediate layer; coating the intermediate layer with a first backup layer that includes a first thixotropic agent, the first thixotropic agent including a first polymer emulsion; coating the first backup layer with a second backup layer that includes a second thixotropic agent, the second thixotropic agent including a second polymer emulsion; and at least partially hardening the first backup layer and the second backup layer.