Method of making ceramic composite articles by inverse shape replication of an expendable pattern

Claim 1

A method for producing a self-supporting ceramic composite body having therein at least one cavity which inversely replicates the geometry of a pattern, said composite body comprising (1) a ceramic matrix obtained by oxidation of a parent metal to form a polycrystalline material consisting essentially of (i) the oxidation reaction product of said parent metal with an oxidant, and, optionally, (ii) one or more metallic constituents; and (2) a filler infiltrated by said matrix, the method comprising the steps of: (a) providing an expendable pattern material; (b) packing said pattern material within a bed of conformable filler to inversely replicate therein the geometry of said pattern material, said bed of filler being characterized by (1) being permeable to said oxidant when required for said oxidant to contact the molten parent metal in step (c) and being permeable to infiltration by the growth of the oxidation reaction product through said filler, and (2) at least in a support zone thereof enveloping said pattern material having sufficient cohesive strength to retain the inversely replicated geometry within said bed; (c) replacing said pattern material with a quantity of parent metal and maintaining a temperature above the melting point of said parent metal but below the melting point of said oxidation reaction product to maintain a body of molten parent metal and, at said temperature, (1) reacting the molten parent metal with said oxidant to form said oxidation reaction product, (2) maintaining at least a portion of said oxidation reaction product in contact with and between said body of molten metal and said oxidant, to progressively transport molten metal from said body of molten metal through the oxidation reaction product and into said bed of filler to concurrently form said cavity in said bed of filler as oxidation reaction product continues to form at the interface between said oxidant and previously formed oxidation reaction product, and (3) continuing said reacting for a time sufficient to at least partially infiltrate said filler within said oxidation reaction product by growth of the latter to form said composite body having said cavity therein; and (d) separating the resulting self-supporting composite body from excess filler, if any.

Claim 2

A method for producing a self-supporting ceramic composite body having therein at least one cavity which inversely replicates the geometry of a pattern, said composite body comprising (1) a ceramic matrix obtained by oxidation of a parent metal to form a polycrystalline material consisting essentially of (i) the oxidation reaction product of said parent metal with an oxidant, and, optionally, (ii) one or more metallic constituents; and (2) a filler infiltrated by said matrix, the method comprising the steps of: (a) providing an expendable pattern material; (b) packing said pattern material within a bed of conformable filler to inversely replicate therein the geometry of said pattern material, said bed of filler being characterized by (1) being permeable to said oxidant when required for said oxidant to contact the molten parent metal in step (c) and being permeable to infiltration by the growth of the oxidation reaction product through said filler, and (2) at least in a support zone thereof enveloping said pattern material having sufficient cohesive strength to retain the inversely replicated geometry within said bed; (c) replacing said pattern material with a quantity of parent metal and maintaining a temperature above the melting point of said parent metal but below the melting point of said oxidation reaction product to maintain a body of molten parent metal and, at said temperature, (1) reacting the molten parent metal with said oxidant to form said oxidation reaction product, (2) maintaining at least a portion of said oxidation reaction product in contact with and between said body of molten metal and said oxidant, to progressively transport molten metal from said body of molten metal through the oxidation reaction product and into said bed of filler to concurrently form said cavity in said bed of filler as oxidation reaction product continues to form at the interface between said oxidant and previously formed oxidation reaction product, and (3) continuing said reacting for a time sufficient to at least partially infiltrate said filler within said oxidation reaction product by growth of the latter to form said composite body having said cavity therein; and (d) separating the resulting self-supporting composite body from excess filler, if any.

Claim 7

The method according to any of the foregoing claims wherein the pattern material is selected from the group consisting of polystyrenes, polyurethane foam, expendable grade wax, and mixtures thereof.

Claim 8

The method according to any of the foregoing claims wherein said oxidant is a vapor-phase oxidant.

Claim 9

The method according to any of the foregoing claims wherein said oxidant is a solid or a liquid at said temperature.

Claim 13

The method according to any of the foregoing claims wherein said par ent metal is selected from the group consisting of aluminum, silicon, titanium, tin, zirconium and hafnium.

Claim 14

The method according to any of Claims 1 and 3-12, including removing said pattern material by chemical or physical means, preheating said bed of filler to a temperature at or above the temperature of said parent metal, and while maintaining said bed of filler at the preheating temperature, adding said quantity of molten parent metal.

Claim 15

The method according to any of the foregoing claims wherein said filler includes a solid oxidant or a liquid oxidant as a component thereof.

Claim 16

The method according to any of the foregoing claims wherein said parent metal is an aluminum parent metal, said oxidant is an oxygen-containing gas and said temperature is from about 850°C to about 1450°C.

Claim 17

The method according to any of the foregoing claims including using at least one suitable dopant material in conjunction with said parent metal.

Claim 18

The method according to any of the foregoing claims including providing at least one dopant material at least partially within said filler.

Claim 20

The method according to any of the foregoing claims including incorporating a bonding agent into said filler, at least in said support zone thereof.

Claim 21

The method according to any of the foregoing claims wherein said filler is further characterized by having, at least in a support zone thereof enveloping said pattern material, sufficient cohesive strength to retain the inversely replicated geometry within said bed upon transport of said parent metal as defined in step (c).