Graded metallic structures and method of forming; and related articles

Abstract

A metallic structure having a graded microstructure is provided. The metallic structure comprises a graded region comprising a plurality of grains having a gradient in grain size varying as a function of position between a first median grain size at an outer region and a second median grain size at an inner region and a plurality of dispersoids dispersed within the microstructure. The first median grain size is different from the second median grain size. A method of forming a metallic structure having a graded microstructure is also provided. The method comprises: providing a metallic structure comprising at least one reactive species; diffusing at least one reactant at a controlled rate from an outer region of the metallic structure towards an inner region of the metallic structure to form a gradient in reactant activity; reacting the reactant with the reactive species to form a plurality of dispersoids; and heat treating the metallic structure to achieve grain growth so as to form a graded microstructure.

1 . A metallic structure having a graded microstructure comprising:
 a graded region comprising a plurality of grains having a gradient in grain size varying as a function of position between a first median grain size at an outer region and a second median grain size at an inner region, wherein the first median grain size is different from the second median grain size; and   
       a plurality of dispersoids dispersed within the microstructure. 
     
     
         2 . The metallic structure of  claim 1 , wherein the metallic structure comprises a material selected from the group consisting of cobalt, nickel, iron, and titanium. 
     
     
         3 . The metallic structure of  claim 2 , wherein the metallic structure comprises a material selected from the group consisting of a cobalt-based super alloy, a nickel-based super alloy, and a titanium-based alloy. 
     
     
         4 . The metallic structure of  claim 3 , wherein the metallic structure comprises a nickel-based super alloy. 
     
     
         5 . The metallic structure of  claim 1 , wherein the metallic structure comprises an alloy selected from the group selected from the group consisting of UNS N07718, UNS N13100, UNS N09706, MX4, RENE104, RENE95, RENE88DT, and UDIMET 720. 
     
     
         6 . The metallic structure of  claim 1 , wherein the first median grain size has a value in the range from about 100 nanometers to about 1 micrometer. 
     
     
         7 . The metallic structure of  claim 6 , wherein the first median grain size has a value in the range from about 100 nanometers to about 500 nanometers. 
     
     
         8 . The metallic structure of  claim 1 , wherein the second median grain size has a value in the range from about 10 micrometers to about 100 micrometers. 
     
     
         9 . The metallic structure of  claim 8 , wherein the second median grain size has a value in the range from about 10 micrometers to about 50 micrometers. 
     
     
         10 . The metallic structure of  claim 1 , wherein the dispersoid comprises a material selected from the group consisting of an oxide, a nitride, a boride, a carbide, an oxynitride, a carbo-nitride. 
     
     
         11 . The metallic structure of  claim 10 , wherein the dispersoid comprises an oxide. 
     
     
         12 . The metallic structure of  claim 11 , wherein the oxide comprises an oxide selected from the group consisting of alumina, yttria, hafnia, lanthanum oxide, nickel oxide, thoria, titania, zirconia, erbium oxide, ceria, and yttrium aluminum oxide. 
     
     
         13 . The metallic structure of  claim 12 , wherein the dispersoids comprise yttria. 
     
     
         14 . The metallic structure of  claim 1 , wherein the dispersoids have a median size in the range from about 10 nanometers to about 1 micrometer. 
     
     
         15 . The metallic structure of  claim 1 , wherein the dispersoids have a median size in the range from about 10 nanometers to about 100 nanometers 
     
     
         16 . The metallic structure of  claim 1 , wherein the metallic structure is structurally stable in a temperature about 600° C. to about 1100° C. 
     
     
         17 . The metallic structure of  claim 1 , wherein the metallic structure is a bulk monolithic structure. 
     
     
         18 . A gas turbine component comprising the metallic structure of  claim 1 . 
     
     
         19 . A turbine airfoil comprising the metallic structure of  claim 1 . 
     
     
         20 . An aircraft engine disc comprising the metallic structure of  claim 1 . 
     
     
         21 . A method of forming a metallic structure having a graded microstructure, comprising:
 providing a metallic structure comprising at least one reactive species;   diffusing at least one reactant, at a controlled rate, from an outer region of the metallic structure towards an inner region of the metallic structure, to form a gradient in reactant activity;   reacting the reactant with the reactive species to form a plurality of dispersoids; and   heat treating the metallic structure to achieve grain growth, so as to form a graded microstructure,   wherein the graded microstructure comprises a graded region comprising a plurality of grains having a gradient in grain size varying as a function of position between a first median grain size at an outer region and a second median grain size at an inner region, wherein the first median grain size is different from the second median grain size; and   a plurality of dispersoids dispersed within the microstructure.   
     
     
         22 . The method of  claim 21 , wherein the metallic structure comprises a material selected from the group consisting of a cobalt-based super alloy, a nickel-based super alloy, and a titanium-based alloy. 
     
     
         23 . The method of  claim 22 , wherein the metallic structure comprises a titanium-based alloy. 
     
     
         24 . The method of  claim 21 , wherein diffusing a reactant comprises exposing the metallic structure to an effective activity of the reactant. 
     
     
         25 . The method of  claim 24 , wherein exposing the metallic structure to an effective activity of the reactant comprises exposing the metallic structure to a gaseous phase of the reactant. 
     
     
         26 . The method of  claim 24 , wherein exposing the metallic structure to an effective activity of the reactant comprises exposing the metallic structure to a liquid phase of the reactant. 
     
     
         27 . The method of  claim 21 , wherein diffusing the reactant, at a controlled rate, comprises providing the reactant at a controlled partial pressure. 
     
     
         28 . The method of  claim 21 , wherein heat treating the metallic structure to achieve grain growth comprises heating at a temperature in a range from about 600° C. to about 1200° C. 
     
     
         29 . The method of  claim 21 , wherein the reactive species comprises a material selected from the group consisting of an oxide former, a carbide former, a nitride former, and a boride former. 
     
     
         30 . The method of  claim 29 , wherein the reactive species comprises a plurality of oxide formers. 
     
     
         31 . The method of  claim 21 , wherein the reactive species comprises at least one selected from the group consisting of aluminum, yttrium, hafnium, lanthanum, erbium, thorium, titanium, magnesium, cerium, and erbium. 
     
     
         32 . The method of  claim 21 , wherein the reactant comprises a material selected from the group consisting of oxygen, boron, carbon, and nitrogen. 
     
     
         33 . The method of  claim 21 , wherein the dispersoids comprise a material selected from the group consisting of an oxide, a nitride, a boride, a carbide, a oxynitride, an intermetallic, and a carbo-nitride. 
     
     
         34 . The method of  claim 21 , wherein the first median grain size has a value in the range from about 100 nanometers to about 1 micrometer. 
     
     
         35 . The method of  claim 21 , wherein the second median grain size has a value in the range from about 10 micrometers to about 50 micrometers. 
     
     
         36 . The method of  claim 21 , wherein reacting the reactant with the reactive species comprises:
 decomposing a precursor particles, dispersed within the metallic structure, into a product comprising a secondary reactive species and a secondary reactant; and   reacting the secondary reactant with the reactive species.