Aircraft components with porous portion and methods of making

Abstract

A cooled wall segment for a gas turbine engine, including a body defining a contact surface configured to be in contact with circulating hot gas and an outer surface configured to be in contact with cooling air, the body including at least one retention element complementary to a retention element of the engine. The body has a first portion including the at least one retention element, and a porous second portion made of a porous material permeable to air and containing a plurality of interconnected pores, the porous material having a porosity greater than that of the first portion, the second portion being engaged to the first portion and defining at least part of the contact surface, the second portion defining at least part of a fluid communication between the outer surface and the contact surface through the interconnected pores. Methods of forming components are also discussed.

1 . A cooled wall segment for a gas turbine engine, the segment comprising:
 a body defining a contact surface configured to be in contact with circulating hot gas and an outer surface configured to be in contact with cooling air, the body including at least one retention element complementary to a retention element of the engine, the body having:
 a first portion including the at least one retention element, and 
 a porous second portion made of a porous material permeable to air and containing a plurality of interconnected pores, the porous material having a porosity greater than that of the first portion, the second portion being engaged to the first portion and defining at least part of the contact surface, the second portion defining at least part of a fluid communication between the outer surface and the contact surface through the interconnected pores. 
   
     
     
         2 . The segment as defined in  claim 1 , wherein the second portion defines at least an upstream part of the contact surface. 
     
     
         3 . The segment as defined in  claim 1 , wherein the segment is a shroud segment, the first portion defining at least a part of the outer surface having a plurality of cooling holes defined therethrough, the cooling holes defining part of the fluid communication between the outer surface and the contact surface. 
     
     
         4 . The segment as defined in  claim 3 , wherein the body has a plenum defined therein, the first portion including an outer wall defining the outer surface and an opposed plenum surface bordering the plenum, the outer wall having the plurality of cooling holes defined therethrough defining a fluid communication between the outer surface and the plenum, the body having a fluid communication between the plenum and the at least part of the contact surface through the second portion. 
     
     
         5 . The segment as defined in  claim 4 , wherein the second portion also includes a surface bordering the plenum, the fluid communication between the plenum and the contact surface being formed only through the second portion. 
     
     
         6 . The segment as defined in  claim 4 , wherein the plenum is completely enclosed by the first portion, the first portion having at least one fluid passage defined therethrough between the plenum and the second portion. 
     
     
         7 . The segment as defined in  claim 3 , wherein the body further includes an intermediate portion made of another porous material permeable to air and containing a plurality of interconnected pores, the other porous material having a porosity greater than that of the first portion, the intermediate portion extending intermediate the first and second portions, the second portion being configured as a coating extending across at least the intermediate portion to define the at least part of the contact surface, the fluid communication between the outer surface and the contact surface being defined through the pores of the intermediate and second portions. 
     
     
         8 . The segment as defined in  claim 6 , wherein the intermediate portion is more permeable to air than the second portion. 
     
     
         9 . The segment as defined in  claim 1 , wherein the porous material defines an abradable coating. 
     
     
         10 . The segment as defined in  claim 3 , wherein the body further includes a coating extending across at least the second portion to define another part of the contact surface, the coating being less permeable to air than the second portion, the fluid communication between the outer surface and the contact surface being defined through the second portion between the first portion and the coating. 
     
     
         11 . The segment as defined in  claim 4 , wherein the plenum is filled with porous material. 
     
     
         12 . The segment as defined in  claim 1 , wherein the segment is a heat shield segment, the body further including a third portion made of another porous material permeable to air and containing a plurality of interconnected pores, the other porous material having a porosity greater than that of the first portion, the first and third portions cooperating to define the outer surface of the body, the second portion being configured as a coating extending across inner surfaces of the first and third portions, the second portion and third portion defining the fluid communication between the outer surface and the contact surface through the interconnected pores. 
     
     
         13 . The segment as defined in  claim 12 , wherein one of the first and third portions includes a plurality of spaced apart pieces, the pieces being interconnected by the other of the first and third portions. 
     
     
         14 . The segment as defined in  claim 1 , wherein the porosity of the porous material defining the second portion is from 7% to 70%. 
     
     
         15 . The segment as defined in  claim 1 , wherein the porosity of the porous material defining the second portion is at least 70%. 
     
     
         16 . The segment as defined in  claim 1 , wherein the second portion is engaged to the first portion by a material connection formed through one or both of a debinding step and a sintering step of a metal injection molding process. 
     
     
         17 . A method of forming a shroud segment for a gas turbine engine through a powder injection molding process, the method comprising:
 forming a green body of the shroud segment, including:   forming a first part from a first feedstock, the first part defining an open cavity,   filling the open cavity with a second part made of a second feedstock, and   enclosing the second part with a third part made of the first feedstock, the third part extending over the second part and cooperating with the first part to close the open cavity; and   debinding and sintering the green body while the second part supports the third part to prevent collapse of the third part within the cavity such that the second feedstock defines a porous material permeable to air and containing a plurality of interconnected pores.   
     
     
         18 . A metal-injection molded component comprising a body having a first portion and a second porous portion made of a porous material, the porous material having a porosity greater than that of the first portion. 
     
     
         19 . The metal-injection molded component of  claim 18 , wherein the porous portion is embedded within the first portion, such that the porous portion is unexposed to an exterior of the component. 
     
     
         20 . The metal-injection molded component of  claim 18 , wherein the component defines a contact surface configured to be in contact with circulating hot gas and an outer surface configured to be in contact with cooling air, and wherein the second portion is permeable to air and contains a plurality of interconnected pores, the second portion being engaged to the first portion and defining at least part of the contact surface, the second portion defining at least part of a fluid communication between the outer surface and the contact surface through the interconnected pores.