Turbine repair procedures

Abstract

Turbine repair process, including: Providing a damaged turbine component (101) comprising a substrate made of ceramic matrix composite material (121), wherein the damaged turbine component (101) has a higher pressure region (103) in a cavity of the turbine component (101) and a lower pressure region (105) outside the turbine component (101), wherein the higher pressure region (103) is at a higher pressure than the lower pressure region (105), wherein the damaged turbine component (101) has an opening (109) between the higher pressure region (103) and the lower pressure region, Introducing particles (107) suspended in a fluid into the cavity forming the region (103) of higher pressure, the particles (107) migrating to the opening (109) due to the pressure difference, and at least partially repairing the opening (109) between the higher pressure region (103) and the lower pressure region (105) by allowing at least a portion of the particles (107) to contact and adhere to the ceramic composite material (121), thereby at least partially closing the opening (109) and forming a repaired turbine component (101).

Description

DECLARATION REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] The United States Government retains license rights to this invention and the right, under limited circumstances, to require the patent owner to license it to others on reasonable terms under the terms of Government Contract No. DE-FC26-05NT42643 awarded by the United States Department of Energy. FIELD OF THE INVENTION

[0002] The present invention is directed to turbine components and methods for repairing turbine components. More specifically, the present invention is directed to repaired coatings on turbine components and methods for repairing coatings on turbine components. BACKGROUND OF THE INVENTION

[0003] Gas turbine components are exposed to thermally, mechanically, and chemically hostile environments. For example, in the compressor section of a gas turbine, atmospheric air is compressed to, for example, 10 to 25 times atmospheric pressure and adiabatically heated, for example, to between 427°C and 677°C (800°F and 1250°F) during operation. This heated and compressed air is fed into a combustor where it is mixed with fuel. The fuel is ignited, and the combustion process heats the gases to very high temperatures, for example, more than 1650°C (3000°F). These hot gases flow through the turbine, where blades attached to rotating turbine disks extract energy to drive the turbine fan and compressor, and through the exhaust system, where the gases provide enough energy to rotate a generator rotor to produce electricity.

[0004] Operation under these conditions can create vulnerability to damage, e.g., from foreign objects striking turbine components such as blades. Blade damage can lead to reduced turbine operating efficiency, more frequent repairs, shorter durations between scheduled repairs, and / or cost inefficiencies.

[0005] US 6,283,356 B1 describes a method for repairing a depression in the surface of an article. The method comprises providing a first and a second metal powder. The first powder has a first melting temperature and the second powder has a second melting temperature lower than the first melting temperature. The first powder is disposed in the depression so as to substantially fill the depression at least to the surface of the article. US 7,258,530 B2 discloses an airfoil formed from a plurality of prefabricated, structural ceramic matrix composite panels. Each panel is formed to have an open shape with opposite ends that can move freely during drying, curing, and / or firing of the ceramic matrix composite material to minimize interlaminar stresses caused by anisotropic sintering shrinkage.DE 600 37 473 T2 describes a method to reduce or prevent material loss of silica and silicon-containing materials in high-temperature combustion gas environments, such as those found in industrial land-based turbines, aircraft engines, automobiles and heat exchangers, by injecting an effective amount of elemental silicon and / or silicon-containing compound into the combustion air or directly the combustion gas during operation of an engine.

[0006] A method for in-situ turbine repair, a repaired coating, and a repaired turbine component that do not suffer from one or more of the above disadvantages would be desirable in the art. BRIEF DESCRIPTION OF THE INVENTION

[0007] The object of the invention is achieved by the turbine repair method according to claim 1. The turbine repair method according to the invention comprises the following steps: Providing a damaged turbine component comprising a ceramic matrix composite substrate, the damaged turbine component having a higher pressure region within a cavity of the turbine component and a lower pressure region exterior of the turbine component, the higher pressure region being at a higher pressure than the lower pressure region, the damaged turbine component having an opening between the higher pressure region and the lower pressure region;

[0008] Introducing particles suspended in a fluid into the cavity forming the region of higher pressure, the particles migrating towards the opening due to the pressure difference; and

[0009] at least partially repairing the opening between the higher pressure region and the lower pressure region by allowing at least a portion of the particles to contact and adhere to the ceramic composite material, thereby at least partially closing the opening and forming a repaired turbine component. SHORT DESCRIPTION OF THE DRAWING Fig. 1 schematically shows an example of the inventive turbine repair method of an exemplary turbine component according to the disclosure. Fig. 2 schematically shows an example of the inventive turbine repair method of an exemplary coating according to the disclosure.

[0010] Wherever possible, the same reference numerals are shown in the figures to represent the same parts therein. DETAILED DESCRIPTION OF THE INVENTION

[0011] Provided is an example of the turbine repair method of the invention, a repaired coating, and a repaired turbine component. Embodiments of the present disclosure extend the useful life of turbine components, allow in-situ repair of coatings and / or turbine components, prevent damage due to oxidation, prevent contamination of engine components, or combinations thereof. One embodiment allows silicon molecules to migrate through a cooling passage and adhere to the walls of holes formed by damage from foreign and / or self-imposed objects, e.g., through Braunian motion and / or thermal energy they exhibit. The molecules are eventually converted to silicon dioxide and reduce recession rates of ceramic matrix composite substrates due to increased localized amounts of SiO2 molecules near the damaged portion.

[0012] Fig. 1 and Fig. 2 schematically show an example of the turbine repair method according to the invention. Each of the Fig. 1 and Fig. 2 shows a turbine component 101A, followed by the turbine component 101B after the occurrence of the damage, and the turbine component 101C after the repair according to an embodiment of the method. Fig. 2 shows sectional views corresponding Fig. 1 along lines AA, BB and CC. The turbine repair method is applicable to a suitable turbine component 101. As shown in Fig. 1, in one embodiment, the turbine component is a turbine blade 100 or a turbine vane. Other suitable turbine components include, but are not limited to, a dovetail, a shaft, a platform, a vane, a tip cap, a dendrite, or any other suitable component having a pressure differential.

[0013] As in Fig. 2, the turbine component 101 includes a higher pressure region 103 and a lower pressure region 105. The higher pressure region 103 of the turbine component 101 is bound by one or more layers that include a ceramic matrix composite material 121. In one embodiment, the ceramic matrix composite material 121 defines a cavity within the turbine component 101, such as a core of the turbine blade 100. In one embodiment, the core is fractured into two or more cavities.

[0014] Near the lower pressure region 105, the turbine component 101, in one embodiment, includes a coating, such as an environmental barrier coating (EBC) 115 on the turbine component 101. In one embodiment, the EBC 115 extends around the turbine component 101, such as through a suction side and through a pressure side. The EBC 115 includes a suitable number of layers or materials capable of operating under the conditions of the lower pressure region 105. The layer(s) of the EBC 115 is / are applied using a suitable method capable of applying material to ceramic matrix composites. For example, suitable methods include, but are not limited to, atmospheric plasma spraying, reactive ion implantation, chemical vapor deposition, plasma-enhanced chemical vapor deposition, immersion coating, electrophoretic deposition, or a combination thereof.Suitable layers are silicon-based and / or include silicon dioxide, such as a bond coat that provides chemical compatibility with ceramic matrix composites. Another suitable layer is a transition layer, such as barium strontium aluminosilicate (BSAS), (Yb,Y)2Si2O7, mullite with barium strontium aluminosilicate, or a combination thereof, that provides resistance to water vapor penetration, chemical compatibility with the bond coat, a coefficient of thermal expansion compatible with ceramic matrix composites, or a combination thereof. Another suitable layer is a top coat, such as Y2SiO5 or barium strontium aluminosilicate, that provides water vapor recession and / or a coefficient of thermal expansion compatible with ceramic matrix composites. In further embodiments, the EBC 115 includes a thermally grown oxide layer.

[0015] During operation of a turbine employing turbine component 101, the higher pressure region 103 and the lower pressure region 105 are under different conditions. For example, during operation, the higher pressure region 103 is at a higher pressure than the lower pressure region 105, resulting in the pressure differential. The pressure differential decreases after a portion of the EBC 115 and the ceramic matrix composite material 121 is removed, e.g., due to damage to the lower pressure region 105 by foreign objects. Such damage forms an opening 109 between the higher pressure region 103 and the lower pressure region 105.

[0016] In one embodiment, prior to foreign object damage, turbine component 101A operates at a predetermined range of pressure differential, e.g., between about 3% and 10% greater than an outer zone (such as a hot gas path) and / or greater than about 0.2068 bar, greater than about 0.3447 bar, at about 0.3447 bar, between about 0.2068 bar and about 0.4826 bar, between about 0.3447 bar and about 0.4826 bar, or any suitable combination, subcombination, range, or subrange thereof. After foreign object damage occurs, or after foreign object damage has occurred, the pressure differential between higher pressure region 103 and lower pressure region 105 of turbine component 101B decreases. In one embodiment, the decreased pressure differential is identified, allowing identification of the damage without visual inspection.Due to the occurrence of damage caused by the foreign object, the turbine repair method is applied.

[0017] Additionally or alternatively, such identification of foreign object damage may be based on monitoring a predetermined pressure range for the higher pressure region 103 and / or a predetermined pressure range for the lower pressure region 105. In one embodiment, the predetermined pressure range for the higher pressure region 103 is between about 3% and about 10% higher than an outer zone (such as a hot gas path and / or the lower pressure region 105). Following foreign object damage, the pressure within the higher pressure region 103 is reduced.

[0018] The higher pressure region 103 and the lower pressure region 105 may also operate under temperature differences, resulting in a temperature differential. For example, in one embodiment, the higher pressure region 103 operates at a lower temperature, such as between about 371.1°C and about 815.6°C, and the lower pressure region 105 operates at a higher temperature, such as between about 648.9°C and about 1371.0°C.

[0019] The opening 109 may be formed by foreign object damage between the higher pressure region 103 and the lower pressure region 105, resulting in a drop in the pressure difference between the higher pressure region 103 and the lower pressure region 105. The foreign object has a random size based on structured particles and / or agglomerates coming from upstream sections. In one embodiment, the foreign object damage corresponds to a foreign particle having a dimension greater than about 1.4 mm, greater than about 1.6 mm, greater than about 1.8 mm, greater than about 2.0 mm, greater than about 2.2 mm, or any suitable combination, subcombination, range, or subrange thereof. The opening 109 has a cavity geometry formed through the EBC 115 and the ceramic matrix composite 121. In one embodiment, the opening 109, e.g.,, a channel, a cylindrical recess or hole, a conical recess or hole, a frusto-conical recess or hole, a gap / crack, or any combination thereof.

[0020] To repair the damage, the opening 109 is at least partially repaired by one or more of the particles 107 introduced through the higher pressure region 103. In one embodiment, the particles 107 are introduced through a feeder 123 located, for example, in the dovetail portion of the turbine blade 100. The particles 107 migrate to the opening 109, for example, based on the pressure differential, and contact the ceramic matrix composite 121. A portion of the particles 107 contact the EBC 115 and / or are ejected into the lower pressure region 105. The particles 107 that contact the EBC 115 do not substantially adhere. At least a portion of the particles 107 that contact the ceramic matrix composite 121 adhere. These particles 107 interrupt the opening 109 and thereby at least partially fill the entire damaged passage and allow, for example,, increasing the pressure differential such that the higher pressure region 103 and the lower pressure region 105 differ in pressure within the operating range that existed prior to the foreign object damage, and at least partially repair the turbine component 101C. In one embodiment, the particles 107 are converted into other materials, such as a molten ceramic and / or an oxidized material (e.g., silicon dioxide), by the presence of heat and / or oxygen.

[0021] The particles 107 are any suitable particles that can be introduced into the higher pressure region 103 and at least partially repair the opening 109. In one embodiment, the particles 107 include elemental silicon. In another embodiment, the oxygen and / or moisture of the higher pressure region 103 converts some or substantially all of the particles 107 into silicon dioxide.

[0022] The particles 107 are of any suitable geometry and size that allow introduction into the higher pressure region 103 and at least partially repair the opening 109. In one embodiment, one or more of the particles 107 are spheroidal, spherical, cuboidal, substantially planar, complex-shaped, or a combination thereof. In one embodiment, one or more of the particles 107 are nanosized, e.g., having a maximum dimension within a nanometer range, such as between about 2 nm and 10 nm, between about 5 nm and about 6 nm, less than about 20 nm, less than about 10 nm, less than 5 nm, or any suitable combination, subcombination, any suitable range, or subrange thereof. In one embodiment, one or more of the particles 107 have a µm size, e.g.,they have a maximum dimension within a µm range, such as less than about 2 µm, less than about 1 µm, between about 1 µm and about 2 µm, about 1 µm, or any suitable combination, subcombination, range, or subrange thereof.

[0023] The particles 107 are introduced in a suitable manner so as to allow, for example, the continued operation of a turbine utilizing the turbine component 101 without stopping. In one embodiment, the particles 107 are suspended in a fluid, such as a liquid and / or a gas. In one embodiment, the particles 107 are introduced into the supply 123 by injection, e.g., with air and / or other gases.

[0024] In one embodiment, the particles 107 are introduced with air. In one embodiment, the particles are introduced with the air at ppm by weight Si between about 0.07 and about 4, between about 0.07 and about 0.2, between about 1 and about 2, between about 2 and about 3, between about 3 and about 4, or any suitable combination, subcombination, range, or subrange thereof.

[0025] In one embodiment, the particles 107 are introduced intermittently, e.g., to form about 1 thousandth of an inch of material in the opening 109 per day, at a rate of about 4 moles or any other suitable rate that allows the turbine component 101 to be repaired. In one embodiment, the particles 107 are introduced during operation of a turbine utilizing the turbine component.

[0026] After repair, the turbine component 101, such as the blade 100, includes a repaired region 111 of the repaired coating with a silicon dioxide material 202 deposited on and surrounded by the ceramic matrix composite material 121, corresponding to a region of foreign object damage, such as the opening 109. In one embodiment, the silicon dioxide material 202 is deposited on and completely surrounded by a portion of the ceramic matrix composite material 121 and / or the EBC 115. In one embodiment, the silicon dioxide material 202 includes intercalated elemental silicon that has not been oxidized. In this embodiment, the repaired region 111 has a hardness between the hardness of silicon dioxide and silicon.

[0027] While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, the invention is not intended to be limited to the particular embodiment disclosed as the best mode for carrying out this invention, but the invention will include all embodiments falling within the scope of the appended claims.

Claims

[1] Turbine repair process, comprising: Providing a damaged turbine component (101) comprising a substrate made of ceramic matrix composite material (121), wherein the damaged turbine component (101) has a higher pressure region (103) in a cavity of the turbine component (101) and a lower pressure region (105) outside the turbine component (101), wherein the higher pressure region (103) is at a higher pressure than the lower pressure region (105), wherein the damaged turbine component (101) has an opening (109) between the higher pressure region (103) and the lower pressure region, Introducing particles (107) suspended in a fluid into the cavity forming the region (103) of higher pressure, the particles (107) migrating to the opening (109) due to the pressure difference, and at least partially repairing the opening (109) between the higher pressure region (103) and the lower pressure region (105) by allowing at least a portion of the particles (107) to contact and adhere to the ceramic composite material (121), thereby at least partially closing the opening (109) and forming a repaired turbine component (101). [2] The method of claim 1, further comprising identifying a pressure difference between the higher pressure region (103) and the lower pressure region (105) prior to introducing the particles (107) into the higher pressure region (103). [3] The method of claim 1, wherein the higher pressure of the higher pressure region (103) is 3% higher than the lower pressure of the lower pressure region (105). [4] The method of claim 1, wherein the higher pressure of the higher pressure region (103) is 10% higher than a lower pressure of the lower pressure region (105). [5] The method of claim 1, wherein the higher pressure of the higher pressure region (103) is between 3% and 10% higher than a lower pressure of the lower pressure region (105). [6] The method of claim 1, wherein the particles (107) include elemental silicon. [7] The method of claim 1, wherein the lower pressure region (105) is at a temperature between 648.9°C and 1371.0°C. [8] The method of claim 1, wherein the higher pressure region (103) is at a temperature between 371.1°C and 815.6°C. [9] The method of claim 1, wherein the particles (107) are smaller than 20 nm. [10] A method according to claim 1, wherein the particles (107) are smaller than 2 µm. [11] A method according to claim 1, wherein the introduction of the particles (107) is carried out by injection with compressed air. [12] The method of claim 1, wherein the higher pressure region (103) is defined by a layer including ceramic matrix composite material (121). [13] The method of claim 1, wherein the repaired turbine component (101) is a turbine blade (100), a shroud, or a nozzle. [14] The method of claim 1, wherein the repaired turbine component (101) includes a repaired region (111) having a silicon material deposited thereon and surrounded by the ceramic matrix composite material (121). [15] The method of claim 1, wherein at least a portion of the particles (107) after at least partially repairing the opening (109) are oxides. [16] The method of claim 1, wherein at least a portion of the particles (107) is melted after at least partially repairing the opening (109).

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