Patent Application
20080254276
This invention is directed generally to coatings applied to metal foams, and more particularly to coatings applied to metal foams usable with cooling systems of turbine airfoils.
Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine vane and blade assemblies to these high temperatures. As a result, turbine vanes and blades must be made of materials capable of withstanding such high temperatures. In addition, turbine vanes and blades often contain cooling systems for prolonging the life of the vanes and blades and reducing the likelihood of failure as a result of excessive temperatures. Many conventional cooling systems of turbine airfoils are formed of the same materials used to form the turbine airfoils. However, different heating loads are typically found throughout a turbine engine and within a cooling system of a turbine engine. Thus, a need exists for different materials that are better suited for forming cooling systems of a turbine engine.
This invention relates to a coating system for attaching a surface layer to a foam material. In at least one embodiment, the coating system may be usable as a component of a cooling system of a turbine engine. The coating system may include preparing an outer surface of the foam such that at least a portion of the porous structure forming the foam material extends outwardly from a plane in which an outer surface of filler in the foam material resides. The surface layer is attached to the outer surface and to exposed portions of the porous structure, which enables an enhanced mechanical connection between the surface layer and the foam material.
The coating system may be formed with a method of forming a surface coating on an outer surface of foam that includes removing filler from the outer surface of the foam to expose a porous structure of the foam, whereby portions of the porous structure extend outwardly from a newly formed outer surface of the filler. The filler may be removed using an appropriate leaching process. The porous structure may be, but is not limited to being, formed from a nickel based superalloy or FeCrAl. A surface layer may be applied to the outer surface of the filler and to exposed portions of the porous structure, whereby the surface layer is attached to the porous structure at least in part due to mechanical interaction with the portions of the porous structure extending outwardly from the newly formed outer surface of the filler. The surface layer may be applied via spraying or via infiltration of a metallic powder. If a metallic powder is used, the powder may be subjected to a heat treatment or HIPing, or both. In one embodiment, the surface layer may be applied to a single outer surface of the foam. In another embodiment, the surface layer may be applied to two outer surfaces of the porous structure, whereby the two outer surfaces of the porous structure are generally planar and generally opposite to each other. The filler material may then be removed from remaining portions of the porous structure, such as with an appropriate leaching process.
In some embodiments, the foam may not be received with filler within the pores of the material. In such an embodiment, the porous structure may be infiltrated with a removable filler before removing the filler from the outer surface of the foam. The filler may be, but is not limited to being, a ceramic filler.
An advantage of this invention is that at least a portion of the porous structure forming the metal foam may be exposed and protrude from an outer surface of the filler in the foam, thereby enabling the surface layer to be attached to the metal foam, at least in part, due to the mechanical interaction with the portions of the porous structure extending outwardly from the outer surface of the filler. Such a configuration significantly increases the ability of the surface layer to remain attached to the porous structure.
These and other embodiments are described in more detail below.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.
As shown in
The coating system 10 may include a foam material 14, as shown in
The next step may include removing the filler 24 from the outer surface 16 of the foam 14 to expose the porous structure 18 of the foam 14, as shown in
A surface layer 12 may then be applied to the outer surface 16 of the filler 24 and exposed portions of the porous structure 18, as shown in
The remaining filler material 24 may then be removed from the porous structure 18 to leave an unfilled foam material 14. The unfilled foam material with the surface layer 12 may be usable in advanced cooling systems of turbine engines and turbine airfoils of turbine engines.
In at least one embodiment, as shown in
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.
