Metal injection molding process and components formed therewith

Abstract

A process of producing a metallic component having a desired shape that includes at least one nonuniform section, as well as metallic components produced by such a process. The process uses a composition containing a mixture of a polymeric binder and a metal powder that includes particles of an alloy having a reactive element that renders the alloy uncastable. The composition is metal injection molded to yield a green compact having a shape corresponding to the shape of the metallic component, including its at least one nonuniform section. A majority of the binder is then removed from the green compact, and then the green compact is sintered to remove a remainder of the binder and fuse particles of the metal powder together to form the metallic component and the nonuniform section thereof.

1 . A process of producing a metallic component having a desired shape that includes at least one nonuniform section, the process comprising:
 providing a composition comprising a mixture of a metal powder and a polymeric binder, the metal powder comprising particles of an alloy that contains at least one reactive element that renders the alloy uncastable;   metal injection molding the composition into a mold cavity having a shape corresponding to the shape of the metallic component so as to yield a green compact having a shape corresponding to the shape of the metallic component that includes the at least one nonuniform section of the metal component;   removing a majority of the binder from the green compact; and then   sintering the green compact to remove a remainder of the binder and fuse particles of the metal powder together to form the metallic component and the at least one nonuniform section thereof.   
     
     
         2 . The process of  claim 1 , wherein the step of removing the majority of the binder from the green compact comprises treating the green compact to a solvent and/or a thermal treatment. 
     
     
         3 . The process of  claim 1 , wherein the reactive element is lanthanum, yttrium, zirconium and/or hafnium. 
     
     
         4 . The process of  claim 1 , wherein the alloy of the metal powder is a cobalt-based alloy. 
     
     
         5 . The process of  claim 4 , wherein the metal powder consists of the particles of the cobalt-based alloy. 
     
     
         6 . The process of  claim 4 , wherein the cobalt-based alloy consists essentially of, by weight, 20-24% Ni, 20-24% Cr, 13-15% W, 0.2-0.5% Si, 0.05-0.15% C, 0.02-0.12% La, up to 3% Fe, up to 1.25% Mn, up to 0.015% B, and the balance cobalt and incidental impurities. 
     
     
         7 . The process of  claim 6 , further comprising hot isostatic pressing the metal component following the sintering step. 
     
     
         8 . The process of  claim 6 , wherein the metal component has a microstructure that contains networks of agglomerated carbide precipitates at grain boundaries thereof following the sintering step. 
     
     
         9 . The process of  claim 8 , further comprising a solution heat treatment performed on the metal component following the sintering step to reduce the agglomerated carbide precipitates to discrete carbides at the grain boundaries. 
     
     
         10 . The process of  claim 9 , wherein the solution heat treatment comprises heating the metal component to a temperature of about 1200° C. to about 1275° C. 
     
     
         11 . The process of  claim 9 , wherein the solution heat treatment comprises heating the metal component to a temperature of about 1220° C. to about 1250° C. 
     
     
         12 . The process of  claim 1 , wherein the metallic component is a combustor heat shield of a gas turbine engine. 
     
     
         13 . The process of  claim 12 , wherein the at least one nonuniform section is a tapered wall region and/or a turbulator of the heat shield. 
     
     
         14 . A combustor heat shield of a gas turbine engine, the heat shield comprising:
 a hot-side surface adapted to face hot combustion gases within a combustor of the gas turbine engine;   a cold-side surface adapted to face away from the hot combustion gases within the combustor;   at least one nonuniform section chosen from the group consisting of at least one tapered wall region between a midportion and an end portion of the heat shield and turbulators on the cold-side surface of the heat shield;   a cobalt-based alloy composition that contains at least one reactive element that renders the heat shield uncastable; and   a polycrystalline microstructure formed by a metal injection molding process to contain discrete carbides at grain boundaries of the microstructure.   
     
     
         15 . The combustor heat shield of  claim 14 , wherein the cobalt-based alloy composition consists essentially of, by weight, 20-24% Ni, 20-24% Cr, 13-15% W, 0.2-0.5% Si, 0.05-0.15% C, 0.02-0.12% La, up to 3% Fe, up to 1.25% Mn, up to 0.015% B, and the balance cobalt and incidental impurities. 
     
     
         16 . The combustor heat shield of  claim 14 , wherein the at least one nonuniform section comprises the at least one tapered wall region between the midportion and the end portion of the heat shield. 
     
     
         17 . The combustor heat shield of  claim 16 , wherein the heat shield further comprises an opening within the midportion and adapted for receiving a fuel nozzle of the combustor, and the tapered wall region increases the stiffness of the heat shield. 
     
     
         18 . The combustor heat shield of  claim 14 , wherein the at least one nonuniform section comprises the turbulators on the cold-side surface of the heat shield. 
     
     
         19 . The combustor heat shield of  claim 14 , wherein the heat shield is installed in the combustor. 
     
     
         20 . The combustor heat shield of  claim 19 , wherein the combustor is a lean-burning combustor.