BRAZING TAPE OR PREFORM FOR MICROCHANNELS IN A THERMAL BARRIER COATING
A brazing tape or preform includes a layer of a brazing material, and a plurality of ceramic members affixed to the layer. The plurality of ceramic members are configured to be removable by a ceramic solvent. The plurality of ceramic members are comprised of a plurality of water-soluble ceramic members. The ceramic solvent used to remove the ceramic members is water. The brazing material is selected from the group comprising, nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof. The ceramic members comprise, about 60% to about 70% by weight of alumina (Al2O3), about 15% to about 25% by weight of zircon (ZrSiO4) flour, about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4), and about 5% by weight of sugar. The brazing tape may be configured as a flexible tape, and the brazing preform may be configured as a pre-sintered preform.
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This application is a continuation of application Ser. No. 15/062,563 filed on Mar. 7, 2016, and is hereby incorporated by reference.
BACKGROUND OF THE INVENTIONThe method, brazing tape and brazing preform described herein relates generally to thermal barrier coatings. More specifically, the method relates to forming micro channels in a thermal barrier coating with the use of a brazing tape or preform having water-soluble ceramic members.
In gas turbines, air is drawn into and is compressed by a shaft-mounted rotary-type compressor. The compressed air is mixed with fuel in combustors. The mixture is burned, and the hot exhaust gases are passed through a turbine mounted on a shaft. The flow of gas turns the turbine, which turns the shaft/rotor and drives the compressor and fan (for aircraft applications). In land based applications, the turbine may drive a generator. In aircraft applications, the hot exhaust gases flow from the back of the engine, driving it and the aircraft forward.
During operation of gas turbines, the temperatures of combustion gases may exceed 3,000° F., considerably higher than the melting temperatures of the metal parts of the turbine, which are in contact with these gases. Operation of these turbines at gas temperatures that are above the metal part melting temperatures is a well-established art, and depends in part on supplying cooling air to the metal parts through various methods. The metal parts that are particularly subject to high temperatures, and thus require particular attention with respect to cooling, are the metal parts forming combustors and parts located aft of the combustor.
The hotter the turbine inlet gases, the more efficient is the operation of the turbine. There is thus an incentive to raise the turbine inlet gas temperature. However, the maximum temperature of the turbine inlet gases is normally limited by the materials used to fabricate the components downstream of the combustors such as the vanes and the blades of the turbine. In current engines, the turbine vanes and blades are made of nickel-based superalloys, and can operate at temperatures of around 2,100° F.
The metal temperatures can be maintained below melting levels with current cooling techniques by using a combination of improved cooling designs and thermal barrier coatings (TBCs). For example, with regard to the metal blades and vanes employed in gas turbines, some cooling is achieved through convection by providing passages for flow of cooling air from the compressor internally within the blades so that heat may be removed from the metal structure of the blade by the cooling air. Such blades have intricate serpentine passageways within the structural metal forming the cooling circuits of the blade.
Small internal orifices have also been devised to direct this circulating cooling air directly against certain inner surfaces of the airfoil to obtain cooling of the inner surface by impingement of the cooling air against the surface, a process known as impingement cooling. In addition, an array of small holes extending from a hollow core through the blade shell can provide for bleeding cooling air through the blade shell to the outer surface where a film of such air can protect the blade from direct contact with the hot gases passing through the engine, a process known as film cooling.
In another approach, a thermal barrier coating (TBC) is applied to the turbine blade component, which forms an interface between the metallic component and the hot gases of combustion. The TBC includes a ceramic coating that is applied to the external surface of metal parts to impede the transfer of heat from hot combustion gases to the metal parts, thus insulating the component from the hot combustion gas. This permits the combustion gas to be hotter than would otherwise be possible with the particular material and fabrication process of the component.
TBCs include well-known ceramic materials, for example, yttrium-stabilized zirconia (YSZ). Ceramic TBCs usually do not adhere well directly to the superalloys used as substrate materials. Therefore, an additional metallic layer called a bond coat is placed between the substrate and the TBC. The bond coat may be made of a nickel-containing overlay alloy, such as a MCrAlY, where M is an element selected from the group consisting of Ni, Co, Fe and combinations thereof, or other compositions more resistant to environmental damage than the substrate. Alternatively, the bond coat may be a diffusion nickel aluminide or platinum aluminide, which is grown into the surface of the substrate and whose surface oxidizes to form a protective aluminum oxide scale that provides improved adherence of the ceramic top coatings. The bond coat and overlying TBC are frequently referred to as a thermal barrier coating system.
BRIEF DESCRIPTION OF THE INVENTIONIn an aspect of the present invention, a brazing tape includes a layer of a brazing material, and a plurality of ceramic members are affixed to the layer. The plurality of ceramic members are configured to be removable by a ceramic solvent. The plurality of ceramic members are comprised of a plurality of water-soluble ceramic members. The ceramic solvent used to remove the ceramic members is water. The brazing material is selected from the group comprising, nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof. The ceramic members comprise, about 60% to about 70% by weight of alumina (Al2O3), about 15% to about 25% by weight of zircon (ZrSiO4) flour, about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4), and about 5% by weight of sugar. The brazing tape may be configured as a flexible tape, and the brazing preform may be configure as a pre-sintered preform. A plurality of micro channels are formed in a thermal barrier coating by voids left from the plurality of ceramic members.
In another aspect of the present invention, a brazing tape or brazing preform includes a layer comprised of a brazing material, and a plurality of ceramic members are affixed to the layer. The plurality of ceramic members are configured to be removable by a ceramic solvent. The ceramic members may be water-soluble ceramic members, and in this case the ceramic solvent is water. The brazing material may be nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof. The ceramic members may be about 60% to about 70% by weight of alumina (Al2O3), about 15% to about 25% by weight of zircon (ZrSiO4) flour, about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4), and about 5% by weight of sugar. The layer may also be configured as a flexible tape or a pre-sintered preform.
In yet another aspect of the present invention, a preform includes a layer comprised of a brazing material, and a plurality of ceramic members are affixed to the layer. The plurality of ceramic members are configured to be removable by a ceramic solvent. The ceramic members may be water-soluble ceramic members, and in this case the ceramic solvent is water. The brazing material may be nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof. The ceramic members may be about 60% to about 70% by weight of alumina (Al2O3), about 15% to about 25% by weight of zircon (ZrSiO4) flour, about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4), and about 5% by weight of sugar. The layer may also be configured as a pre-sintered preform.
One or more specific aspects/embodiments of the present invention will be described below. In an effort to provide a concise description of these aspects/embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with machine-related, system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “consisting,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters, material constituents and/or environmental conditions are not exclusive of other parameters, constituents or conditions of the disclosed embodiments. Additionally, it should be understood that references to “one embodiment”, “one aspect” or “an embodiment” or “an aspect” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments or aspects that also incorporate the recited features.
The ceramic members 250 may be comprised of a water soluble ceramic material containing about 60% to about 70% by weight of alumina (Al2O3), about 15% to about 25% by weight of zircon (ZrSiO4) flour, about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4), and about 5% by weight of sugar. A water soluble ceramic is described in U.S. Pat. No. 6,024,787, which is incorporated herein by reference. Other water-soluble ceramic materials/compositions may be used as well, and the advantage of a water soluble material is that water can be used to remove or dissolve the ceramic members 250. Other ceramic solvents could be used to remove water soluble or non-water soluble ceramic members, but water is a preferred option as it is environmentally friendly, widely available and relatively inexpensive.
The filler metal layer 230 may be comprised of any suitable brazing material. Non-limiting example materials are nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof. A few specific examples of filler metals are, BNi-2, BNi-9 and DF-4B, however, any suitable brazing material may be used as required for the specific application and substrate.
An advantage provided by the present invention is that micro channels can be formed in thermal barrier coatings, without affecting or damaging the substrate. Thermal barrier coatings having micro channels have improved heat dissipation, and when the micro channels are connected to a cooling circuit even greater TBC performance may be achieved.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. The terms “about” and “approximately” as applied to a particular value of a range applies to both values, and unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims
1. A brazing tape comprising:
- a layer comprised of a brazing material; and
- a plurality of ceramic members affixed to the layer; and
- wherein the plurality of ceramic members are configured to be removable by a ceramic solvent.
2. The brazing tape of claim 1, the plurality of ceramic members comprised of a plurality of water-soluble ceramic members.
3. The brazing tape of claim 2, wherein the ceramic solvent used to remove the ceramic members is water.
4. The brazing tape of claim 1, the brazing material selected from the group comprising:
- nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof.
5. The brazing tape of claim 1, the plurality of ceramic members comprising:
- about 60% to about 70% by weight of alumina (Al2O3);
- about 15% to about 25% by weight of zircon (ZrSiO4) flour;
- about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4); and about 5% by weight of sugar.
6. The brazing tape of claim 1, wherein the layer is configured as a flexible tape.
7. A brazing tape or a brazing preform comprising:
- a layer comprised of a brazing material; and
- a plurality of ceramic members affixed to the layer; and
- wherein the plurality of ceramic members are configured to be removable by a ceramic solvent.
8. The brazing tape or preform of claim 7, the plurality of ceramic members comprised of a plurality of water-soluble ceramic members.
9. The brazing tape or preform of claim 8, wherein the ceramic solvent used to remove the ceramic members is water.
10. The brazing tape or preform of claim 8, the brazing material selected from the group comprising:
- nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof.
11. The brazing tape or preform of claim 10, the plurality of ceramic members comprising:
- about 60% to about 70% by weight of alumina (Al2O3);
- about 15% to about 25% by weight of zircon (ZrSiO4) flour;
- about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4); and
- about 5% by weight of sugar.
12. The brazing tape of claim 11, wherein the layer is configured as a flexible tape.
13. The brazing preform of claim 11, wherein the layer is configured as a pre-sintered preform.
14. A brazing preform comprising:
- a layer comprised of a brazing material; and
- a plurality of ceramic members affixed to the layer; and
- wherein the plurality of ceramic members are configured to be removable by a ceramic solvent.
15. The brazing preform of claim 14, the plurality of ceramic members comprised of a plurality of water-soluble ceramic members.
16. The brazing preform of claim 15, wherein the ceramic solvent used to remove the ceramic members is water.
17. The brazing preform of claim 15, the brazing material selected from the group comprising:
- nickel, nickel alloys, cobalt, cobalt alloys, iron, iron alloys, and combinations thereof.
18. The brazing preform of claim 15, the plurality of ceramic members comprising:
- about 60% to about 70% by weight of alumina (Al2O3);
- about 15% to about 25% by weight of zircon (ZrSiO4) flour;
- about 5% to about 15% by weight of sodium hydrogen phosphate (Na2HPO4); and
- about 5% by weight of sugar.
19. The brazing preform of claim 15, wherein the brazing preform is configured as a pre-sintered preform.
Type: Application
Filed: Apr 6, 2017
Publication Date: Sep 7, 2017
Applicant: General Electric Company (Schenectady, NY)
Inventors: Yan Cui (Greer, SC), Srikanth Chandrudu Kottilingam (Greenville, SC), Brian Lee Tollison (Honea Path, SC)
Application Number: 15/480,806