Novel cermets and molten metal infiltration method and process for their fabrication

Abstract

Cermet comprising ceramic and metal components and a molten metal infiltration method and process for fabrication thereof. The light weight cermets having improved porosity, strength, durability, toughness, elasticity fabricated from presintered ceramic powder infiltrated with a molten metal or metal alloy. Alumina titanium cermets biocompatible with the human body suitable for bone and joint replacements.

What is claimed is:  
     
         1 . A cermet comprising a ceramic powder presintered into a porous ceramic matrix and infiltrated with a molten metal or metal alloy.  
     
     
         2 . The cermet of  claim 1  wherein the ceramic powder is selected from the group consisting of aluminum oxide, beryllium oxide, zirconium oxide, hafnium oxide, vanadium oxide, aluminum nitride, beryllium nitride, zirconium nitride, hafnium nitride, vanadium nitride, aluminum boride, beryllium borate, zirconium boride, hafnium boride, vanadium boride, aluminum silicate, zirconium silicate, hafnium silicate, vanadium silicate, beryllium silicate and a mixture thereof.  
     
     
         3 . The cermet of  claim 2  wherein the infiltrating metal or metal alloy is selected from the group consisting of titanium, aluminum, magnesium, nickel, lithium, copper, iron, silicon, manganese, cobalt, molybdenum, niobium, zirconium, calcium and their combination.  
     
     
         4 . The cermet of  claim 3  wherein the metal or metal alloy is infiltrated into a ceramic powder presintered into a porous ceramic matrix at a temperature higher than is the melting point of the infiltrating metal or metal alloy.  
     
     
         5 . The cermet of  claim 4  wherein the ceramic powder is aluminum oxide having particle sizes from about 10 to about 50 microns.  
     
     
         6 . The cermet of  claim 5  wherein the aluminum oxide has particle sizes about 10 microns.  
     
     
         7 . The cermet of  claim 6  wherein the aluminum oxide is presintered into the porous ceramic matrix at temperature from about 1450° C. to about 1550° C. and infiltrated with molten titanium alloy at temperature lower than 1450° C.  
     
     
         8 . The cermet of  claim 7  wherein the porous ceramic matrix has about zero to about 50 degrees wetting angle.  
     
     
         9 . The cermet of  claim 8  wherein the particle sizes of the presintered porous ceramic matrix are about the same as the particle sizes of the ceramic powder used.  
     
     
         10 . The cermet of  claim 9  wherein the metal alloy is binary, ternary or quaternary alloy selected from alloys shown in Table 1.  
     
     
         11 . A bone implant fabricated from a cermet comprising a ceramic powder presintered into a porous ceramic matrix and infiltrated with a molten metal or metal alloy.  
     
     
         12 . The implant of  claim 11  wherein the ceramic powder is selected from the group consisting of aluminum oxide, zirconium oxide, hafnium oxide, vanadium oxide, aluminum nitride, zirconium nitride, hafnium nitride, vanadium nitride, aluminum boride, zirconium boride, hafnium boride, vanadium boride, aluminum silicate, zirconium silicate, hafnium silicate, vanadium silicate, beryllium oxide, beryllium nitride, beryllium borate, beryllium silicate and a mixture thereof.  
     
     
         13 . The implant of  claim 12  wherein the infiltrating metal or metal alloy is selected from the group consisting of titanium, aluminum, magnesium, nickel, lithium, copper, iron, silicon, manganese, cobalt, molybdenum, niobium, zirconium, calcium and their combination.  
     
     
         14 . The implant of  claim 13  wherein the ceramic powder is pressed into a near-net shape of the bone implant, presintered into a porous ceramic matrix at a temperature higher than is the melting point of the infiltrating metal or metal alloy and infiltrated with the molten metal or metal alloy at temperature lower than the sintering temperature of the ceramic powder.  
     
     
         15 . The implant of  claim 14  wherein the ceramic powder is aluminum oxide having particle sizes from about 10 to about 50 microns presintered into the porous ceramic matrix at temperature from about 1450° C. to about 1550° C. and infiltrated with molten titanium alloy at temperature lower than 1450° C.  
     
     
         16 . The implant of  claim 15  wherein the porous ceramic matrix has about zero to about 50 degrees wetting angle.  
     
     
         17 . The implant of  claim 16  wherein the particle sizes of the aluminum oxide presintered into a porous ceramic matrix are about the same as the particle sizes of aluminum oxide used.  
     
     
         18 . The implant of  claim 17  wherein the metal alloy is binary, ternary or quaternary alloy selected from alloys shown in Table 1 having the melting point lower than 1450° C.  
     
     
         19 . A process for fabrication of cermets comprising of a ceramic powder infiltrated with a molten metal or metal alloy, said process comprising steps: 
 (a) presintering a ceramic powder selected from the group consisting of any one or a mixture of aluminum oxide, aluminum nitride, aluminum boride, aluminum silicate, hafnium oxide, hafnium nitride, hafnium boride, hafnium silicate, vanadium oxide, vanadium nitride, vanadium boride, vanadium silicate, beryllium oxide, beryllium nitride, beryllium borate and beryllium silicate at its sintering temperature and proper atmospheres into a porous ceramic matrix of a desired shape;    (b) molten metal infiltrating the matrix of step (a) with a metal selected from the group consisting of titanium, nickel, magnesium, calcium, aluminum, lithium, copper, iron, silicon, manganese, cobalt, molybdenum, niobium, zirconium, and their combination wherein said selected metal having a melting point lower than the sintering temperature of the powder of step (a).    
     
     
         20 . The process of  claim 21  wherein additionally a wetting angle of the metal or metal alloy is determined before the compact of step (a) is infiltrated.  
     
     
         21 . The process of  claim 20  wherein the wetting angle for the metal and ceramic compact interaction is zero or is not larger than about 60 degrees.  
     
     
         22 . The process of  claim 21  wherein the ceramic powder is presintered under vacuum.  
     
     
         23 . The process of  claim 22  wherein the molten metal is infiltrated evenly into the ceramic presintered compact.  
     
     
         24 . The process of  claim 23  wherein the ceramic powder is aluminum oxide.  
     
     
         25 . The process of  claim 24  wherein the aluminum oxide powder has particle sizes from about 10 μ to about 50 μ.  
     
     
         26 . The process of  claim 25  wherein the sintering temperature is between 1400° C. and 1660° C.  
     
     
         27 . The process of  claim 26  wherein the aluminum oxide has particle sizes about 10 μ.  
     
     
         28 . The process of  claim 27  wherein the sintering temperature is about 1500° C.  
     
     
         29 . The process of  claim 28  wherein the metal used for molten-metal-infiltration is titanium alloy.  
     
     
         30 . The process of  claim 29  wherein the temperature used for titanium alloy is lower than the sintering temperature of the ceramic powder compact.  
     
     
         31 . The process of  claim 30  wherein the metal is the titanium alloy selected from the group of binary, ternary and quaternary alloy shown in Table 1.  
     
     
         32 . The process of  claim 31  wherein the titanium alloy contains about 20-30% of nickel.  
     
     
         33 . The process of  claim 32  wherein the temperature for molten-metal-infiltration is under 1500° C.  
     
     
         34 . The process of  claim 33  wherein the ceramic powder additionally contains an additive selected for the group consisting of calcium oxide, magnesium oxide and sulfur present in an amount for about 0.01 to about 1%.