Mullite-containing investment casting core

Abstract

An investment casting core includes a mullite-containing core body. The body can be made by providing a mullite-containing powder, forming the powder into a green body, and sintering the green body to form the mullite-containing core body.

1 . An investment casting core comprising:
 a mullite-containing core body; and   a metallic core body joined to the mullite-containing core body, and the mullite-containing core body has a coefficient of thermal expansion that is within 2% of a coefficient of thermal expansion of the metallic core body.   
     
     
         2 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has, by weight, 40% or greater of mullite. 
     
     
         3 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has, by weight, 40-90% of mullite. 
     
     
         4 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has a material selected from the group consisting of alumina, silica, magnesia, yttria, calcia, zirconium silicate and combinations thereof. 
     
     
         5 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has, by weight, 40-90% of mullite and 60-5% of silica. 
     
     
         6 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has a material selected from the group consisting of magnesia, yttria, calcia and combinations thereof. 
     
     
         7 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has zirconium silicate. 
     
     
         8 . (canceled) 
     
     
         9 . The investment casting core as recited in  claim 1 , wherein the metallic core body is selected from the group consisting of molybdenum, tungsten, tantalum, rhenium, niobium and combinations thereof. 
     
     
         10 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has, by weight, 80-90% mullite, 15-5% silica, 2.5-10% alumina, 0-2.5% zircon, 0-5% of one or more of: calcia, magnesia and yttria. 
     
     
         11 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body has a multi-modal or bi-modal grain size distribution. 
     
     
         12 . A method of making an investment casting core, the method comprising:
 providing a mullite-containing powder;   forming the mullite-containing powder into a green body;   sintering the green body to form a mullite-containing core body; and   joining the mullite-containing core body to a metallic core body, and selecting a composition of the mullite-containing powder to obtain a coefficient of thermal expansion of the mullite-containing core body that matches a coefficient of thermal expansion of the metallic core body.   
     
     
         13 . The method as recited in  claim 12 , including providing the mullite-containing powder in a blend with a binder, and the forming includes molding the blend into the green body. 
     
     
         14 . The method as recited in  claim 12 , wherein the mullite-containing powder has at least a bi-modal particle size distribution of mullite particles. 
     
     
         15 . The method as recited in  claim 12 , wherein the mullite-containing powder has a material selected from alumina, silica, magnesia, yttria, calcia, zirconium silicate and combinations thereof in a powder with at least a bi-modal particle size distribution. 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . A method of investment casting, the method comprising:
 casting a metallic component at least partially around an investment casting core that has a mullite-containing core body and a metallic core body joined to the mullite-containing core body. the mullite-containing core body having a coefficient of thermal expansion that is within 2% of a coefficient of thermal expansion of the metallic core body.   
     
     
         19 . The method as recited in  claim 18 , wherein the mullite-containing core body has a material selected from the group consisting of alumina, silica, magnesia, yttria, calcia, zirconium silicate and combinations thereof. 
     
     
         20 . The method as recited in  claim 18 , further comprising a metallic core body joined to the mullite-containing core body. 
     
     
         21 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body includes yttria. 
     
     
         22 . The investment casting core as recited in  claim 1 , wherein the mullite-containing core body includes calcia. 
     
     
         23 . The method as recited in  claim 18 , wherein the mullite-containing core body includes yttria. 
     
     
         24 . The method as recited in  claim 18 , wherein the mullite-containing core body includes calcia. 
     
     
         25 . The method as recited in  claim 12 , wherein the mullite-containing core body includes yttria. 
     
     
         26 . The method as recited in  claim 12 , wherein the mullite-containing core body includes calcia. 
     
     
         27 . The investment casting core as recited in  claim 1 , wherein the metallic core body is adhesively joined to the mullite-containing core body.