Patent Application
20140137408
The embodiments described herein relate generally to turbine engines, and, more specifically, to fabricating components with micro-channel cooling therein.
In a turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases. Energy is extracted from the gases in a high pressure turbine (HPT), which powers the compressor, and in a low pressure turbine (LPT), which powers a fan in a turbofan aircraft engine application, or powers an external shaft for marine and industrial applications.
Engine efficiency increases with temperature of combustion gases. However, the combustion gases heat the various components along their flow path, which in turn requires cooling thereof to achieve a long engine lifetime. Typically, the hot gas path components are cooled by bleeding air from the compressor. This cooling process reduces engine efficiency, as the bled air is not used in the combustion process.
In exemplary turbine engine components, thin metal walls of high strength superalloy metals are typically used for enhanced durability while minimizing the need for cooling thereof. Various cooling circuits and features are tailored for these individual components in their corresponding environments in the engine. For example, a series of internal cooling passages, or serpentines, may be formed in a hot gas path component. A cooling fluid may be provided to the serpentines from a plenum, and the cooling fluid may flow through the passages, cooling the hot gas path component substrate and coatings. However, this cooling strategy typically results in comparatively low heat transfer rates and non-uniform component temperature profiles.
In one aspect, a method of forming a hot gas path component is provided. The method includes forming at least one groove in an outer surface of a substrate, wherein the at least one groove has a base and a top. The method further includes filling the at least one groove with a filler. The method also includes applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component. The filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.
In another aspect, a method of coating a hot gas path component including a substrate with at least one groove formed in an outer surface of the substrate is provided. The method includes filling the at least one groove with a filler. The method also includes applying at least one cover layer over at least a portion of the outer surface of the substrate such that the at least one groove and the at least one cover layer define at least one micro-channel for cooling the component. The filler is automatically removed from the at least one micro-channel during application of the at least one cover layer.
In yet another aspect, a method of assembling a turbine engine assembly is provided. The method includes providing a turbine engine including a compressor, a combustor, and a turbine. The method also includes coupling at least one hot gas path component to the turbine engine including forming at least one groove in an outer surface of the hot gas path component. The method includes filling the at least one groove with a filler. Additionally, the method includes depositing at least one structural coating over at least a portion of the outer surface of the hot gas path component such that the at least one groove and the at least one structural coating define at least one micro-channel for cooling the hot gas path component. The filler is automatically removed from the at least one micro-channel during deposition of the at least one structural coating.
Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and/or claimed in combination with any feature of any other drawing.
The present disclosure is directed generally to rotary machine components, particularly hot gas path components, formed with cooling features, such as micro-channels, to facilitate cooling of the respective components. In particular, aspects of the present disclosure are directed to methods of forming micro-channels in a hot gas path component for use in a turbine engine where a filler material used during formation of the micro-channels is automatically removed during the formation process.
Turbine engine 10 may include a plurality of hot gas path components 100 (shown in
When hot gas path component 100 is exposed to hot gas flow 22, hot gas path component 100 is heated by hot gas flow 22 and may reach a temperature at which hot gas path component 100 fails. A cooling system for hot gas path component 100 is provided to allow turbine engine 10 to operate with hot gas flow 22 at a high temperature, and to increase the efficiency and performance of turbine engine 10.
A method of coating hot gas path component 100 is described with reference to
Substrate 110 is typically cast prior to forming grooves 132 in outer surface 112 of the substrate. Substrate 110 may be formed from any suitable material, described herein as a “first material.” Depending on the intended application for hot gas path component 100, the first material may include Ni-base, Co-base, and Fe-base superalloys, and the like. The Ni-base superalloys may be those containing both γ and γ′ phases, particularly those Ni-base superalloys containing both γ and γ′ phases wherein the γ′ phase occupies at least 40% by volume of the superalloy. Such alloys are known to be advantageous because of a combination of desirable properties including high temperature strength and high temperature creep resistance. The first material may also include a NiAl intermetallic alloy, as these alloys are also known to possess a combination of superior properties including high temperature strength and high temperature creep resistance that are advantageous for use in turbine engine applications used for aircraft. In the case of Nb-base alloys, coated Nb-base alloys having superior oxidation resistance will be preferred, such as Nb/Ti alloys, and particularly those alloys comprising Nb-(27-40)Ti-(4.5-10.5)Al-(4.5-7.9)Cr-(1.5-5.5)Hf-(0-6)V in an atom percentage. The first material may also include an Nb-base alloy that contains at least one secondary phase, such as an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride. Such alloys are analogous to a composite material in that they contain a ductile phase (i.e. the Nb-base alloy) and a strengthening phase (i.e., an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride).
Coating 150 extends along outer surface 112 of substrate 110. Coating 150 conforms to outer surface 112 and covers grooves 132 forming channels 130. Coating 150 includes one or more layers 50. In the illustrated embodiment, coating 150 is just the first layer 50, or structural coating, that covers grooves 132. In another embodiment, a single layer may be all that is used. In alternative embodiments, however, hot gas path component 100 may include additional layers 50, such as a bondcoat and a thermal barrier coating (TBC). In one embodiment, coating 150 includes a second material, which may be any suitable material, bonded to outer surface 112 of substrate 110. For particular configurations, coating 150 has a thickness in the range of 0.1 to 2.0 millimeters, and more particularly, in the range of 0.1 to 1 millimeter, and still more particularly 0.1 to 0.5 millimeters for industrial components. For aviation components, coating 150 has a thickness in the range of 0.1 to 0.25 millimeters. However, other thicknesses may be utilized depending on the requirements for a particular hot gas path component 100.
Coating 150 may be deposited using a variety of techniques. In one embodiment, coating 150 is disposed over at least a portion of outer surface 112 of substrate 110 by performing an ion plasma deposition. Briefly, ion plasma deposition includes placing a cathode formed of a coating material into a vacuum environment within a vacuum chamber, providing substrate 110 within the vacuum environment, supplying a current to the cathode to form a cathodic arc upon a cathode surface resulting in erosion or evaporation of coating material from the cathode surface, and depositing the coating material from the cathode upon the substrate outer surface 112.
In one embodiment, the ion plasma deposition process includes a plasma vapor deposition process. Non-limiting examples of coating 150 include structural coatings, bond coatings, oxidation-resistant coatings, and thermal barrier coatings. In some embodiments, coating 150 includes nickel-based or cobalt-based alloys, and more particularly includes a superalloy, or a NiCoCrAlY alloy. For example, where the first material of substrate 110 is a Ni-base superalloy containing both γ and γ′ phases, coating 150 may include these same materials.
In other embodiments, coating 150 is disposed over at least a portion of outer surface 112 of substrate 110 by performing a thermal spray process. For example, the thermal spray process may include combustion spraying or plasma spraying, the combustion spraying may include high velocity oxygen fuel spraying (HVOF) or high velocity air fuel spraying (HVAF), and the plasma spraying may include atmospheric (such as air or inert gas) plasma spray, or low pressure plasma spray (LPPS), which is also known as vacuum plasma spray or VPS). In one embodiment, a NiCrAlY coating is deposited by HVOF or HVAF. In alternative embodiments, techniques for depositing one or more layers of coating 150 include, without limitation, sputtering, electron beam physical vapor deposition, electroless plating, and electroplating.
In one embodiment, it is desirable to employ multiple deposition techniques for forming coating 150. For example, with reference to
More generally, the second material used to form coating 150 includes any suitable material that permits hot gas path component 100 to function as described herein. In one embodiment of hot gas path component 100, the second material is capable of withstanding temperatures of approximately 1150° C., while the TBC can withstand temperatures of approximately 1320° C. Coating 150 is compatible with and adapted to be bonded to outer surface 112 of substrate 110. This bond may be formed when coating 150 is deposited onto substrate 110. Bonding may be influenced during the deposition by many parameters, including the method of deposition, the temperature of substrate 110 during the deposition, whether the deposition surface is biased relative to the deposition source, and other parameters. Bonding may also be affected by subsequent heat treatment or other processing. In addition, the surface morphology, chemistry, and cleanliness of substrate 110 prior to the deposition can influence the degree to which metallurgical bonding occurs. In addition to forming a strong metallurgical bond between coating 150 and substrate 110, it is desirable that this bond remain stable over time and at high temperatures with respect to phase changes and interdiffusion, as described herein. By compatible, it is preferred that the bond between these elements be thermodynamically stable such that the strength and ductility of the bond do not deteriorate significantly over time (e.g., up to 3 years) by interdiffusion or other processes, even for exposures at high temperatures of approximately 1,150° C. for a Ni-base alloy substrate 110 and Ni-base coating 150, or higher temperatures of approximately 1,300° C. where higher temperature materials are utilized, such as Nb-base alloys.
In one embodiment where the first material of substrate 110 is an Ni-base superalloy containing both γ and γ′ phases or a NiAl intermetallic alloy, second materials for coating 150 may include these same materials. Such a combination of coating 150 and substrate 110 materials is preferred for applications where the maximum temperatures of the operating environment are below 1650° C. In an embodiment where the first material of substrate 110 is an Nb-base alloy, second materials for coating 150 may also include an Nb-base alloy, including the same Nb-base alloy.
In some embodiments, such as applications that impose temperature, environmental, or other constraints that make the use of a metal alloy coating 150 undesirable, it is preferred that coating 150 include materials that have properties that are superior to those of metal alloys alone, such as composites in the general form of intermetallic compound (IS)/metal alloy (M) phase composites and intermetallic compound (IS)/intermetallic compound (IM) phase composites. Metal alloy M may be the same alloy as used for substrate 110, or a different material, depending on the requirements of hot gas path component 100. These composites are, in general, similar in that they combine a relatively more ductile phase M or IM with a relatively less ductile phase Is, in order to create coating 150 with the advantages of both materials. Further, in order to have a successful composite, the two materials must be compatible. As used herein in regard to composites, the term “compatible” means that the materials must be capable of forming the desired initial distribution of their phases and maintaining that distribution for extended periods of time, as described above, at temperatures of 1,150° C. or greater without undergoing metallurgical reactions that substantially impair the strength, ductility, toughness, and other important properties of the composite. Such compatibility can also be expressed in terms of phase stability. That is, the separate phases of the composite should be stable during operation at operating temperature over extended periods so that the phases remain separate and distinct, retaining their separate identities and properties, and do not become a single phase or a plurality of different phases due to interdiffusion. Compatibility can also be expressed in terms of morphological stability of the interphase boundary interface between the IS/M or IS/IM composite layers. Such instability may be manifested by convolutions that disrupt the continuity of either layer. It is also noted that within a given coating 150, a plurality of IS/M or IS/IM composites may also be used, and such composites are not limited to two material or two phase combinations. The use of such combinations is merely illustrative, and not exhaustive or limiting of the potential combinations. Thus M/IM/IS, M/IS1/IS2 (where IS1 and IS2 are different materials), and many other combinations are possible.
In an embodiment where substrate 110 includes an Ni-base superalloy comprising a mixture of both γ and γ′ phases, IS may include Ni3 [Ti, Ta, Nb, V], NiAl, Cr3Si, [Cr, Mo]xSi, [Ta, Ti, Nb, Hf, Zr, V]C, Cr3C2, and Cr7C3 intermetallic compounds and intermediate phases, and M may include an Ni-base superalloy comprising a mixture of both γ and γ′ phases. In Ni-base superalloys comprising a mixture of both γ and γ′ phases, the elements Co, Cr, Al, C, and B are nearly always present as alloying constituents, as well as varying combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the constituents of the exemplary IS materials described correspond to one or more materials typically found in Ni-base superalloys as may be used as the first material (to form substrate 110), and thus may be adapted to achieve the phase and interdiffusional stability described herein. As an additional example in the case where the first material (substrate 110) includes NiAl intermetallic alloy, Is may include Ni3 [Ti, Ta, Nb, V], NiAl, Cr3Si, [Cr, Mo]xSi, [Ta, Ti, Nb, Hf, Zr, V]C, Cr3C2, and Cr7C3 intermetallic compounds and intermediate phases and IM may include a Ni3Al intermetallic alloy. Again, in NiAl intermetallic alloys, one or more of the elements Co, Cr, C, and B are nearly always present as alloying constituents, as well as varying combinations of Ti, Ta, Nb, V, W, Mo, Re, Hf, and Zr. Thus, the constituents of the exemplary IS materials described correspond to one or more materials typically found in NiAl alloys as may be used as the first material, and thus may be adapted to achieve the phase and interdiffusional stability described herein.
In an embodiment where substrate 110 includes an Nb-base alloy, including an Nb-base alloy containing at least one secondary phase, IS may include an Nb-containing intermetallic compound, an Nb-containing carbide, or an Nb-containing boride, and M may include an Nb-base alloy. It is preferred that such IS/M composite includes an M phase of an Nb-base alloy containing Ti such that the atomic ratio of the Ti to Nb (Ti/Nb) of the alloy is in the range of 0.2-1, and an IS phase comprising a group consisting of Nb-base silicides, Cr2 [Nb, Ti, Hf], and Nb-base aluminides, and wherein Nb, among Nb, Ti and Hf, is the primary constituent of Cr2 [Nb, Ti, Hf] on an atomic basis. These compounds all have Nb as a common constituent, and thus may be adapted to achieve the phase and interdiffusional stability.
In addition to coating system 150, the interior surface of groove 132 (or of the micro-channel 130, if the first layer of coating 150 is not particularly oxidation resistant) can be further modified to improve its oxidation and/or hot corrosion resistance. Suitable techniques for applying an oxidation-resistant coating (not shown) to the interior surface of grooves 132 (or of micro-channels 130) include vapor-phase or slurry chromiding, vapor-phase or slurry aluminizing, or overlay deposition via evaporation, sputtering, ion plasma deposition, thermal spray, and/or cold spray. Example oxidation-resistant overlay coatings include materials in the MCrAlY family (M={Ni, Co, Fe} and Y={yttrium or another rare earth element}) as well as materials selected from the NiAlX family (X={Cr, Hf, Zr, Y, La, Si, Pt, Pd}).
Additionally, it is desirable to limit the depth of groove 132 in order to facilitate the automatic removal of the filler during the deposition process, wherein the depth is defined as the distance between the base of the groove and outer surface 112 of substrate 110. By forming the re-entrant shaped grooves 132 with a depth in the range of approximately 0.5 mm to approximately 1.27 mm (0.020 inches to 0.050 inches), the filler can be automatically removed during the coating application process, thereby eliminating the difficult filler removal processing step for conventional micro-channel forming techniques.
In addition, by forming re-entrant shaped grooves 132 with narrow openings 136 (tops) in the range of approximately 0.127 mm to approximately 0.4 mm (0.005 inches to 0.016 inches), openings 136 can be bridged by coating 150 and the filler can be automatically removed during the coating application process, thereby eliminating the difficult filler removal processing step for conventional micro-channel forming techniques. In the embodiment illustrated, coating 150 completely bridges grooves 132, such that coating 150 seals micro-channels 130.
As discussed above, although micro-channels 130 are shown as re-entrant shaped micro-channels, micro-channels 130 may have any configuration, for example, they may be straight, curved, or have multiple curves, etc. For the example, in one embodiment, the grooves are rectangular shaped. Specifically, base 134 of each of grooves 132 is substantially the same width as top 136 of groove 132. In some embodiments, openings 136 (tops) are in the range of approximately 0.127 mm to approximately 0.4 mm (0.005 inches to 0.016 inches), whereby openings 136 can be bridged by coating 150. In addition, the depth of grooves 132 may be in the range of approximately 0.5 mm to approximately 1.27 mm (0.020 inches to 0.050 inches), whereby filler material 120 can be automatically removed during the coating application process, thus eliminating the difficult filler removal processing step for conventional micro-channel forming techniques.
The primary benefit of using filler material 120 described above to fill grooves 132 is that filler material 120 is automatically removed as vapor during the complete coating process. A benefit beyond automatic removal is that the filler can withstand the initial impact velocity and the temperature of coating 150, whereby enough filler remains in grooves 132 to assure that no coating 150 collects in grooves 132.
After application of filler material 120 to grooves 132, outer surface 112 of substrate 110 may be cleaned and prepared for coating, such as by machining, grit blasting, washing, and/or polishing outer surface 112, including the portions of filler material 120 that form or extend past outer surface 112. Once outer surface 112 of substrate 110 is suitably cleaned and prepared, one or more surface coatings may be applied to outer surface 112 over filler material 120, as depicted in
A method of manufacturing hot gas path component 100 is described with reference to
As indicated in
As indicated in
In the exemplary embodiment, as shown in
Exemplary embodiments of the methods for forming cooling channels are described above in detail. The methods are not limited to the specific embodiments described herein, but rather, steps of the methods may be utilized independently and separately from steps described herein. For example, the methods described herein may have other industrial or consumer applications and are not limited to practice with turbine components as described herein. Rather, one or more embodiments may be implemented and utilized in connection with other industries.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly stated. The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “approximately” used in connection with a quantity is inclusive of the stated value, and has the meaning dictated by context, (e.g., includes the degree of error associated with measurement of the particular quantity). In addition, the term “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, references to “one embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.
This written description uses examples to disclose the invention, including the best mode, and 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 language of the claims.
