Precision molded refractory articles and method of making

Claim 2

A PROCESS FOR FORMING A REFRACTORY ARTICLE COMPRISING THE STEPS OF: WARM MIXING MULTI-MODAL REFRACTORY POWDER UNDER REDUCED PRESSURE WITH UP TO 45 VOLUME PERCENT OF THERMOPLASTIC BINDER; HEATING THE POWDER-BINDER MIXTURE ABOVE THE SOFTENING TEMPERATURE OF SAID BINDER; MOLDING THE RESULTINNNG SOFTENED MIXTURE IN A HEATED FLEXIBLE MOLD TO FORM AN ESSENTIALLY VOID-FREE GREEN MOLDED ARTICLE HAVING THE SHAPE AND SIZE OF SAID MOLD;

Claim 3

A process for forming a precision molded article comprising the steps of: mixing two or more refractory powders to form a multi-modal refractory powder; warm mixing said multi-modal powder under reduced pressure with no more than 40 volume percent of a suitable thermoplastic binder; cooling the powder-binder mixture to a solid; milling the solid powder-binder mixture to a granular consistency; heating the powder-binder mixture above the softening temperature of said mixture. extruding the heated into an evacuated warm elastic mold; vibrating said mold and its warm contents; isostatically pressurizing the warm mold and its contents to a pressure of about 100 p.s.i.; cooling said molds and its contents to room temperature; demolding said contents by applying a vacuum to the outside of said elastic mold thereby forming a green molded article; packing the green molded article in a nonreactive refractory powder; heating said green molded article to volatilize the thermoplastic binder and to consolidate the refractory powder forming a refractory skeleton causing a shrinkage of less than 2 percent; placing the refractory skeleton in contact with a suitable infiltrant material; heating the refractory skeleton and infiltrant material above the melting point of said infiltrant whereby said infiltrant melts and wicks into the refractory skeleton; cooling the infiltrated part to room temperature to form a precision molded article.

Claim 4

A process for forming a precision molded article comprising the steps of: mixing two or more refractory powders to form a multi-modal refractory powder; warm mixing said multi-modal powder under reduced pressure with no more than 40 volume percent of a suitable thermoplastic binder; cooling the powder-binder mixture to a solid; milling the solid powder-binder mixture to a granular consistency; heating the powder-binder mixture above the softening temperature of said mixture. extruding the heated into an evacuated warm elastic mold; vibrating said mold and its warm contents; isostatically pressurizing the warm mold and its contents to a pressure of about 100 p.s.i.; cooling said molds and its contents to room temperature; demolding said contents by applying a vacuum to the outside of said elastic mold thereby forming a green molded article; packing the green molded article in a nonreactive refractory powder; heating said green molded article to volatilize the thermoplastic binder and to consolidate the refractory powder forming a refractory skeleton causing a shrinkage of less than 2 percent; placing the refractory skeleton in contact with a suitable infiltrant material; heating the refractory skeleton and infiltrant material above the melting point of said infiltrant whereby said infiltrant melts and wicks into the refractory skeleton; cooling the infiltrated part to room temperature to form a precision molded article.

Claim 5

The process of claim 2 where said precision molded article is an electrical discharge machining electrode, said refractory is tungsten, and said infiltrant is copper.

Claim 6

The process of claim 2 where said precision molded article is an injection molding die cavity, said refractory is tungsten carbide and said infiltrant is a beryllium-copper alloy.