Pressure forming of metal and ceramic powders

Abstract

A method of pressure forming a brown part from metal and/or ceramic particle feedstocks includes: introducing into a mold cavity or extruder a first feedstock and one or more additional feedstocks or a green or brown state insert made from a feedstock, wherein the different feedstocks correspond to the different portions of the part; pressurizing the mold cavity or extruder to produce a preform having a plurality of portions corresponding to the first and one or more additional feedstocks, and debinding the preform. Micro voids and interstitial paths from the interior of the preform part to the exterior allow the escape of decomposing or subliming backbone component substantially without creating macro voids due to internal pressure. The large brown preform may then be sintered and subsequently thermomechanically processed to produce a net wrought microstructure and properties that are substantially free the interstitial spaces.

What is claimed is: 
     
         1 . A brown metal, a brown ceramic, or a brown metal and ceramic preform, the preform comprising:
 a) at least one insert, the insert comprising an insert metal powder, an insert ceramic powder, or an insert metal and ceramic powder mixture; and   b) a first composition surrounding the at least one insert, the first composition comprising:
 i) a first composition metal powder, a first composition ceramic powder, or a combination of the first composition metal and ceramic powders; and 
 ii) a binder comprising a carrier component, 
   c) wherein at least the first composition has a microstructure that includes micro voids and interstitial paths, the interstitial paths residing between and connecting to adjacent micro voids, and   d) wherein the micro voids of the first composition have a micro void size that is about 1-10 times a particle size of the first composition metal powder, the first composition ceramic powder, or the combination of the first composition metal and ceramic powders.   
     
     
         2 . The preform of  claim 1  wherein the first composition comprises at least one first composition ceramic powder having particles from about 2 microns to about 150 microns in size. 
     
     
         3 . The preform of  claim 2  wherein the at least one first composition ceramic powder has particles from about 25 microns to about 150 microns in size. 
     
     
         4 . The preform of  claim 1  wherein the first composition ceramic powder is selected from the group consisting of alumina particles, yttrium particles, lanthanum oxide particles, zirconia particles, and combinations thereof. 
     
     
         5 . A brown metal, a brown ceramic, or a brown metal and ceramic preform, the preform comprising:
 a) a plurality of inserts, each insert of an insert metal powder, an insert ceramic powder, or an insert metal and ceramic powder mixture, wherein at least two of the plurality of inserts are of different insert compositions of the insert metal powder, the insert ceramic powder, or the insert metal and ceramic powder mixture; and   b) a first composition surrounding the plurality of inserts, the first composition comprising:
 i) a composition metal powder, a composition ceramic powder, or a combination of composition metal and composition ceramic powders; and 
 ii) a binder comprising a carrier component, 
   c) wherein at least the first composition has a microstructure that includes micro voids and interstitial paths characteristic of the carrier component having been volatilized from the binder; and   d) wherein the micro voids of the first composition have a micro void size that is about 1-10 times a particle size of the first composition metal powder, the first composition ceramic powder, or the combination of the first composition metal and ceramic powders.   
     
     
         6 . The preform of  claim 5  wherein the first composition comprises at least one first composition ceramic powder having particles from about 2 microns to about 150 microns in size. 
     
     
         7 . The preform of  claim 6  wherein the at least one first composition ceramic powder has particles from about 25 microns to about 150 microns in size. 
     
     
         8 . The preform of  claim 6  wherein the at least one first composition ceramic powder is selected from the group consisting of alumina particles, yttrium particles, lanthanum oxide particles, zirconia particles, and combinations thereof. 
     
     
         9 . A brown metal, a brown ceramic, or a brown metal and ceramic preform, the preform comprising:
 a) a plurality of inserts, each insert of the same insert metal powder, insert ceramic powder, or insert metal and ceramic powder mixture, wherein at least two of the plurality of inserts are of different particles sizes of the insert metal powder, the insert ceramic powder, or the insert metal and ceramic powders; and   b) a first composition surrounding the plurality of inserts, the first composition comprising:
 i) a composition metal powder, a composition ceramic powder, or a combination of composition metal and ceramic powders; and 
 ii) a binder comprising a carrier component, 
   c) wherein at least the first composition has a microstructure that includes micro voids and interstitial paths characteristic of the carrier component having been volatilized from the binder; and   d) wherein the micro voids of the first composition have a micro void size that is about 1-10 times a particle size of the first composition metal powder, the first composition ceramic powder, or the first composition metal and ceramic powders.   
     
     
         10 . The preform of  claim 9  wherein the first composition comprises at least one first composition ceramic powder having particles from about 2 microns to about 150 microns in size. 
     
     
         11 . The preform of  claim 10  wherein the at least one first composition ceramic powder has particles from about 25 microns to about 150 microns in size. 
     
     
         12 . The preform of  claim 9  wherein the first composition ceramic powder is selected from the group consisting of alumina particles, yttrium particles, lanthanum oxide particles, zirconia particles, and combinations thereof. 
     
     
         13 . A method of producing a consolidated preform for a part, comprising the steps of:
 a) providing a green or brown preform comprising:
 i) a first portion comprising a first metal and/or ceramic powder composition dispersed in a binder; 
 ii) one or more additional portions, at least one of which shares a boundary with the first portion, each additional portion comprising a metal and/or ceramic powder composition dispersed in a binder that is different from at least the first portion; and 
   b) sintering the preform to bind the powder particles to each other to produce a consolidated, unitary preform.   
     
     
         14 . The method of  claim 13  further performing a densification process on the preform subsequent to sintering to densify at least a portion of the consolidated, unitary preform. 
     
     
         15 . The method of  claim 13  wherein at least one additional portion comprises a core that is substantially surrounded by the composition of the first portion. 
     
     
         16 . The method of  claim 15  wherein the core is completely surrounded by the first portion. 
     
     
         17 . The method of  claim 16  wherein the core comprises a majority of the part by weight or volume. 
     
     
         18 . The method of  claim 15  wherein the core comprises a metal composition that is less expensive or of coarser particles than the surrounding first portion. 
     
     
         19 . The method of  claim 18  wherein the first portion comprises a biocompatible metal and/or ceramic that is suitable for use as an implantable medical device. 
     
     
         20 . The method of  claim 13  wherein the preform comprises at least two additional portions. 
     
     
         21 . The method of  claim 15  wherein there are two of more additional portions, one or both being surrounded by a majority of the first portion. 
     
     
         22 . The method of  claim 13  wherein the part comprises a large part. 
     
     
         23 . The method of  claim 13  wherein one of the binders comprises polysaccharide (agar) or acetal. 
     
     
         24 . The method of  claim 13  wherein the consolidated, unitary preform has a complex geometry. 
     
     
         25 . The method of  claim 14  wherein the portion being densified is a metal portion having an initial density that is 97% or less than its theoretical alloy density and the density of the part following the densification is at least 98% of that value. 
     
     
         26 . The method of  claim 25  wherein the part comprises one or more parts for use in a hip replacement assembly, the parts comprising a acetabular shell, a femoral head, and/or a femoral stem. 
     
     
         27 . The method of  claim 25  wherein the part comprises one or more parts for use in a knee replacement assembly, the parts comprising a femoral component and/or a tibial tray. 
     
     
         28 . The method of  claim 25  wherein the part comprises one or more parts for use in a shoulder replacement assembly, the parts comprising a humeral stem, a glenoid sphere, and/or a glenoid fixation device. 
     
     
         29 . The method of  claim 25  wherein the part comprises a lumbar fixation device. 
     
     
         30 . The method of  claim 25  wherein the part comprises an orthopedic screw device configured to couple with adjacent vertebrae. 
     
     
         31 . The method of  claim 25  wherein the part comprises a disc replacement device configured with a portion that extends between adjacent vertebrae and portions transverse to the extension that couples to the outer surfaces of at least one of the adjacent vertebrae. 
     
     
         32 . The method of  claim 25  wherein the part comprises a spinal fixation assembly that includes a set of elongate, parallel rods, the rods having apertures for receiving fasteners for anchoring the rods. 
     
     
         33 . The method of  claim 35  wherein the part comprises a spinal fixation plate for coupling two or more adjacent vertebrae in fixed relation, the plate comprising a body having apertures spaced at an interval designed to match outer surfaces of a sequence of two or more vertebrae, the apertures sized to receive fasteners to anchor the fixation plate to the vertebrae. 
     
     
         34 . A method of pressure forming a part from metal and/or ceramic particle feedstocks, comprising the steps of:
 a) introducing into a mold cavity or extruder a first feedstock and one or more additional feedstocks or an insert made from a feedstock, wherein the different feedstocks correspond to the different portions of the part;   b) pressurizing the mold cavity or extruder to produce a preform having a plurality of portions corresponding to the first and one or more additional feedstocks; and   c) debinding the preform.   
     
     
         35 . The method of  claim 34  wherein the first portion and the one or more additional portions are consolidated in the same mold cavity or extruder at the same time. 
     
     
         36 . The method of  claim 34  wherein the first portion and the one or more additional portions are consolidated in different molds and the green or brown inserts from the separate molds are placed in a single mold and the inserts are pressure molded to form a consolidated unitary green or brown preform. 
     
     
         37 . The method of  claim 34  wherein the pressure forming comprises a direct compression molding process. 
     
     
         38 . The method of  claim 37  wherein the binder comprises a carrier component and a backbone component, and the debinding comprises causing the carrier component to volatize at temperatures under 750° F., and leaving behind micro voids and interstitial paths from the interior of the preform to the exterior, and subsequently allowing the escape of, decomposing, or subliming of the backbone component. 
     
     
         39 . The method of  claim 38  wherein the binder comprises acetal, polysaccharide(agar), polyethylene glycol, an aromatic esther, naphthalene, paradichlorobenzene and/or wax. 
     
     
         40 . The method of  claim 37  wherein the pressure forming comprises an injection molding process. 
     
     
         41 . The method of  claim 37  further comprising sintering the unitary preform to create a consolidated preform. 
     
     
         42 . The method of  claim 41  further comprising a densification process to further densify the consolidated preform into a part. 
     
     
         43 . The method of  claim 42  wherein the further densification process comprises a forging process. 
     
     
         44 . The method of  claim 42  wherein the density of the element before the step of further densification is less than about 97%, as a percentage of theoretical alloy density, and after the thermomechanical processing it is greater than 98% of the theoretical alloy density. 
     
     
         45 . The method of  claim 34  wherein the pressure molding comprises applying from about 500 to about 5000 PSI to at least a portion of the contents of the mold. 
     
     
         46 . The method of  claim 41  wherein the sintering process is performed at temperature range of from about 1,600° F. to about 2,400° F. 
     
     
         47 . The method of  claim 42  wherein the further densification process comprises a mechanical process performed on an automated machine having machine executable instructions for performing the process.