Investment mold having metallic donor element

Abstract

An investment mold includes a refractory investment wall that has a surface region that bounds at least a portion of a mold cavity for receiving a molten metallic material. At least a portion of the surface region includes at least one metallic donor element with respect to the molten metallic material. Upon exposure of the surface region to the molten metallic material, the metallic donor element dopes into the molten metallic material. The method can be used to fabricate a cast article. The cast article can include a body formed of a metallic material having at least one reactive metallic element with respect to reactive-element-loss in an investment casting process. The body can include at least one internal passage that has a surface region that is compositionally rich in the reactive metallic element, which is doped into the body from the surface region of the refractory investment wall.

What is claimed is: 
     
         1 . An investment mold comprising:
 a refractory investment wall having a surface region bounding at least a portion of a mold cavity for receiving a molten metallic material, at least a portion of the surface region including at least one metallic donor element with respect to the molten metallic material, such that upon exposure of the surface region to the molten metallic material the at least one metallic donor element dopes into the molten metallic material.   
     
     
         2 . The investment mold as recited in  claim 1 , wherein the at least one metallic donor element is selected from the group consisting of yttrium, lanthanum, hafnium, erbium, calcium, magnesium, and combinations thereof. 
     
     
         3 . The investment mold as recited in  claim 1 , wherein the at least one metallic donor element includes yttrium. 
     
     
         4 . The investment mold as recited in  claim 1 , wherein the refractory investment wall is an investment core having a refractory body and a coating of the at least one metallic donor element thereon. 
     
     
         5 . The investment mold as recited in  claim 1 , wherein the surface region includes an amount of the at least one metallic donor element sufficient to increase a sub-targeted amount of at least one metallic element in the molten metallic material at least to a targeted amount. 
     
     
         6 . The investment mold as recited in  claim 1 , wherein the at least one metallic donor element includes multiple metallic donor elements. 
     
     
         7 . A method of controlling composition of a cast component in an investment casting process, the method comprising:
 introducing a molten metallic material into a mold cavity, the molten metallic material initially having a sub-targeted amount of at least one metallic element; and   doping at least one metallic donor element from a surface region of a refractory investment wall bounding at least a portion of the mold cavity into the molten metallic material to increase the sub-targeted amount at least to a targeted amount of the at least one metallic element.   
     
     
         8 . The method as recited in  claim 7 , wherein the at least one metallic donor element is selected from the group consisting of yttrium, lanthanum, hafnium, erbium, calcium, magnesium, and combinations thereof. 
     
     
         9 . The method as recited in  claim 7 , wherein the at least one metallic donor element includes yttrium. 
     
     
         10 . The method as recited in  claim 7 , wherein the refractory investment wall is an investment core within the mold cavity, the refractory investment wall having a refractory body and a coating of the at least one metallic donor element on the refractory body. 
     
     
         11 . The method as recited in  claim 7 , wherein the at least one metallic donor element includes multiple metallic donor elements. 
     
     
         12 . An investment cast article comprising:
 a body formed of a metallic material having at least one reactive metallic element with respect to reactive-element-loss in an investment casting process, the body including at least one internal passage having a surface region that is compositionally rich in the at least one reactive metallic element.   
     
     
         13 . The investment cast article as recited in  claim 12 , wherein the body has a single crystal microstructure or a directionally solidified microstructure. 
     
     
         14 . The investment cast article as recited in  claim 12 , wherein the at least one reactive metallic element is selected from the group consisting of yttrium, lanthanum, hafnium, erbium, calcium, magnesium, and combinations thereof.