Patent Description:
Gas turbine engines typically include a compressor section to pressurize inflowing air, a combustor section to burn a fuel in the presence of the pressurized air, and a turbine section to extract energy from the resulting combustion gases. The compressor section typically may comprise alternating rows of rotors and stators, ending with an exit guide vane. The exit guide vane may be angled to remove swirl from the inflowing air, before directing air into a diffuser assembly. The stators of the compressor section may be configured to rotate about an axis of the stator, resulting in wear in a case of the stator assembly.

<CIT> discloses a method for repairing a turbine component. The method includes: removing a turbine component from a turbine rotor assembly; identifying at least one flaw in the turbine component; and direct metal laser melting (DMLM) or direct metal laser depositing (DMLD) a fill material to fill the at least one flaw in the turbine component, forming a repaired turbine component.

<CIT> discloses a process of remanufacturing a backplate used in turbochargers which includes using a mask or an anti-bonding agent and a thermal metal spray. The mask or anti-bonding agent protects the portions of the backplate from being sprayed. The thermal metal spray can be sprayed on a sealing surface of the backplate that is worn during use. Once the process is completed, the backplate can be inspected to ensure that it meets or exceeds the manufacturer's original specifications.

<CIT> discloses a vane shroud for a gas turbine engine having a cylindrical shaped body and a hole arranged at a circumference of the body. The hole is for receiving a trunnion from a variable vane. A counterbore is arranged concentrically around the hole on a radially inward facing surface of the body, and receives a trunnion hub from the variable vane. A shrink-fit insert is seated into the counterbore such that the trunnion hub is provided with a contact surface, and the shrink-fit insert is secured to the shroud through an interference fit.

From a first aspect, the invention provides a method for repairing a pocket of a case for a variable stator assembly as claimed in claim <NUM>.

In various embodiments, depositing the coating is performed in layers for the wear portion of each stator pocket in the plurality of stator pockets. The plurality of wear depths may be received through a gauge. The coating may be a nickel-aluminum plasma coating. The method may further comprise commanding, via the processor, a milling machine to remove a lip at least partially defined by the wear portion of each pocket in the plurality of stator pockets prior to commanding the coating spray torch to deposit the coating. In various embodiments, commanding the milling machine to remove the lip may further comprise machining the lip to a machined depth based on a respective depth in the plurality of wear depths for a respective stator pocket in the plurality of stator pockets. The wear portion of each stator pocket in the plurality of stator pockets may include a recess having an axial portion, a radial portion, and a circumferential portion relative to a centerline defined by an aperture through the stator pocket in the plurality of stator pockets.

From a further aspect, the invention may provide a repair method as claimed in claim <NUM>.

In various embodiments, the repair method may further comprise measuring a wear depth of the wear recess prior to removing the lip. The repair method may further comprise removing the lip based on the measured wear depth. The repair method may further comprise depositing the plasma spray coating to a thickness, the thickness determined based on the wear depth of the recess. The repair method may further comprise aligning a coating spray torch with the recess prior to deposing the plasma spray coating into the wear recess. In various embodiments, aligning the coating spray torch may comprise rotating the variable stator case relative to the coating spray torch. The method may further comprise removing a second lip from a second stator pocket of the variable stator case, the second stator pocket disposed adjacent to the stator pocket. The method may further comprise depositing a first layer in the wear recess, and depositing a second layer into a second wear recess of the second stator pocket of the variable stator case.

From a still further aspect of the invention, a control system for repairing a variable stator case of a gas turbine engine as claimed in claim <NUM> is provided.

In various embodiments, the controller is further operable to: command the rotatable fixture to rotate and align the coating spray torch with a second wear recess of the first pocket in the plurality of pockets; and command the coating spray torch to deposit a second portion of the plasma spray coating into the second wear recess. The controller may be further operable to deposit a plurality of layers in the first wear recess. The controller may be further operable to deposit the plurality of layers to a thickness, the thickness based on the wear depth for the first wear recess.

A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the following illustrative figures. In the following figures, like reference numbers refer to similar elements and steps throughout the figures.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein.

The scope of the disclosure is defined by the appended claims and their legal equivalents rather than by merely the examples described. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, coupled, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

As used herein, "aft" refers to the direction associated with the tail (e.g., the back end) of an aircraft, or generally, to the direction of exhaust of the gas turbine engine. As used herein, "forward" refers to the direction associated with the nose (e.g., the front end) of an aircraft, or generally, to the direction of flight or motion. As used herein and unless defined otherwise, "radial" refers to a direction outward from a gas turbine engine centerline, and "axial" refers to a direction from aft to forward or vice versa.

In various embodiments, a system and method of repairing a stator pocket for a gas turbine engine is disclosed herein. In various embodiments, the method may comprise mask unworn portions of the stator pocket, grit blast and spray the worn portion with nickel coating using dual wire arc methods on the worn stator pockets, and then machining the stator pocket to a predetermined blueprint, in accordance with various embodiments. Typically, nickel coating is used on flat and full-hoop circumferential surfaces (i.e., simpler geometry flat planar and flat annular surface) with line-of-site spray access for dimensional restoration. In various embodiments, each stator pocket in the plurality of stator pockets <NUM> includes a counterbore which comprises an aperture <NUM> and a pocket recess <NUM>. Nickel coating is not usually used on complex geometry such as the counterbores. The use of nickel coating, in accordance with the systems and methods disclosed herein, is not for the material properties, such as using a weld would be. Instead, the systems and methods of the present disclosure are purely for a dimensional restoration of the flowpath. In various embodiments, the repair method and system disclosed herein include repairing the stator back to a predetermined specification without welding, pre-machining, or local fabrication details. In various embodiments, the worn areas may be restored back to the predetermined specification with minimal operation steps relative to typical repair methods to properly restore a gas path surface.

The wear depth may vary from stator pocket to stator pocket. The size of the counterbore for a respective stator pocket may be relatively small, which would likely prevent one skilled in the art from pursuing nickel coatings as described herein. The number of locations of wear may be several per vane assembly being repaired. In various embodiments, by having almost every stator pocket as having variable, and complex shapes, and an angle of the wear providing potential line of sight issues, using nickel coating as the solution is unique, in accordance with various embodiments.

With reference to <FIG>, a gas turbine engine <NUM> is shown according to various embodiments. Gas turbine engine <NUM> may be a two-spool turbofan that generally incorporates a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. In operation, fan section <NUM> can drive coolant (e.g., air) along a path of bypass airflow B while compressor section <NUM> can drive coolant along a core flow path C for compression and communication into combustor section <NUM> then expansion through turbine section <NUM>. Although depicted as a turbofan gas turbine engine <NUM> herein, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures.

Gas turbine engine <NUM> may generally comprise a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis A-A' relative to an engine static structure <NUM> or engine case via several bearing systems <NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. Engine central longitudinal axis A-A' is oriented in the Z direction on the provided X-Y-Z axes. It should be understood that various bearing systems <NUM> at various locations may alternatively or additionally be provided, including for example, bearing system <NUM>, bearing system <NUM>-<NUM>, and bearing system <NUM>-<NUM>.

Low speed spool <NUM> may generally comprise an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure compressor <NUM> and a low pressure turbine <NUM>. Inner shaft <NUM> may be connected to fan <NUM> through a geared architecture <NUM> that can drive fan <NUM> at a lower speed than low speed spool <NUM>. Geared architecture <NUM> may comprise a gear assembly <NUM> enclosed within a gear housing <NUM>. Gear assembly <NUM> couples inner shaft <NUM> to a rotating fan structure. High speed spool <NUM> may comprise an outer shaft <NUM> that interconnects a high pressure compressor <NUM> and high pressure turbine <NUM>. A combustor <NUM> may be located between high pressure compressor <NUM> and high pressure turbine <NUM>. A mid-turbine frame <NUM> of engine static structure <NUM> may be located generally between high pressure turbine <NUM> and low pressure turbine <NUM>. Mid-turbine frame <NUM> may support one or more bearing systems <NUM> in turbine section <NUM>. Inner shaft <NUM> and outer shaft <NUM> may be concentric and rotate via bearing systems <NUM> about the engine central longitudinal axis A-A', which is collinear with their longitudinal axes. As used herein, a "high pressure" compressor or turbine experiences a higher pressure than a corresponding "low pressure" compressor or turbine.

The core airflow may be compressed by low pressure compressor <NUM> then high pressure compressor <NUM>, mixed and burned with fuel in combustor <NUM>, then expanded over high pressure turbine <NUM> and low pressure turbine <NUM>. Turbines <NUM>, <NUM> rotationally drive the respective low speed spool <NUM> and high speed spool <NUM> in response to the expansion.

Gas turbine engine <NUM> may be, for example, a high-bypass ratio geared aircraft engine. In various embodiments, the bypass ratio of gas turbine engine <NUM> may be greater than about six (<NUM>). In various embodiments, the bypass ratio of gas turbine engine <NUM> may be greater than ten (<NUM>). In various embodiments, geared architecture <NUM> may be an epicyclic gear train, such as a star gear system (sun gear in meshing engagement with a plurality of star gears supported by a carrier and in meshing engagement with a ring gear) or other gear system. Geared architecture <NUM> may have a gear reduction ratio of greater than about <NUM> and low pressure turbine <NUM> may have a pressure ratio that is greater than about five (<NUM>). In various embodiments, the bypass ratio of gas turbine engine <NUM> is greater than about ten (<NUM>:<NUM>). In various embodiments, the diameter of fan <NUM> may be significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> may have a pressure ratio that is greater than about five (<NUM>:<NUM>). Low pressure turbine <NUM> pressure ratio may be measured prior to inlet of low pressure turbine <NUM> as related to the pressure at the outlet of low pressure turbine <NUM> prior to an exhaust nozzle. It should be understood, however, that the above parameters are exemplary of various embodiments of a suitable geared architecture engine and that the present disclosure contemplates other gas turbine engines including direct drive turbofans. A gas turbine engine <NUM> may comprise an industrial gas turbine (IGT) or a geared aircraft engine, such as a geared turbofan, or non-geared aircraft engine, such as a turbofan, or may comprise any gas turbine engine as desired.

Referring now to <FIG> and still to <FIG>, according to various embodiments, each of low pressure compressor <NUM>, high pressure compressor <NUM>, low pressure turbine <NUM>, and high pressure turbine <NUM> in gas turbine engine <NUM> may comprise one or more stages or sets of rotating blades and one or more stages or sets of stationary vanes axially interspersed with the associated blade stages but non-rotating about engine central longitudinal axis A-A'.

In various embodiments, compressor stages and/or turbine stages may comprise multiple interspersed stages of blades and vanes. Within the rotor assemblies <NUM> of gas turbine engine <NUM> are multiple rotor disks, which may include one or more cover plates or minidisks. The blades <NUM> rotate about engine central longitudinal axis A-A', while the vanes <NUM> remain stationary with respect to engine central longitudinal axis A-A'.

With continued reference to <FIG> schematically shows, by example, a portion of an engine section <NUM> with variable vanes <NUM>, which is illustrated as a compressor section <NUM> of gas turbine engine <NUM>. It will be understood that the repair systems and methods disclosed herein may be applicable to any variable vane assembly (e.g., an assembly with a variable vane <NUM>).

Engine section <NUM> may include alternating rows of blades <NUM> and vanes <NUM> comprising airfoils <NUM> that extend into the core flow path C. For example, the rotor assemblies <NUM> can carry a plurality of rotating blades <NUM>, while each vane assembly can carry a plurality of vanes <NUM> that extend into the core flow path C. Blades <NUM> create or extract energy (in the form of pressure) from the core airflow that is communicated through the gas turbine engine <NUM> along the core flow path C. Vanes <NUM> direct the core airflow to the blades <NUM> to either add or extract energy. Vanes <NUM> may be arranged circumferentially about engine central longitudinal axis A-A'. In various embodiments, a set of blades <NUM> may be coupled about a circumference of a generally circular disk <NUM>, which may be disposed radially inward of core flow path C. Disk <NUM> with blades <NUM> may comprise a rotor assembly <NUM> configured to rotate about engine central longitudinal axis A-A'. Blades <NUM> and vanes <NUM> may generally be referred to as airfoils <NUM>.

Vane <NUM> has an airfoil body <NUM> having a leading edge <NUM> facing a forward direction in the gas turbine engine <NUM> and a trailing edge <NUM> facing an aft direction. An airfoil <NUM> may include a pressure side wall (i.e. having a generally concave surface) and a suction side wall (i.e. having a generally convex surface) joined together at the respective leading edge <NUM> and trailing edge <NUM>. Each vane <NUM> may include an inner diameter (ID) case <NUM> at an inner diameter end of the airfoil body <NUM> and an outer diameter (OD) case <NUM> disposed at an OD end of the airfoil body <NUM>. For example, the airfoil body <NUM> may extend radially outward from ID case <NUM> at the inner diameter end of the airfoil body <NUM> to the OD case <NUM> at the outer diameter end of the airfoil body <NUM>.

In various embodiments, vane <NUM> is a variable vane. A "variable vane" as defined herein, refers to a vane <NUM> configured to rotate about a vane axis defined through the airfoil body <NUM> of the vane <NUM>. In this regard, the vane <NUM> may be configured to vary an angle of attack of the airfoil body <NUM>, in accordance with various embodiments. In various embodiments, in response to varying the angle of attack of the airfoil body <NUM>, a pocket disposed in the OD case <NUM> may wear over time. In various embodiments, the wear may be circumferential in nature and vary across pockets adjacent to respective vanes within a stator assembly <NUM>.

Referring now to <FIG>, a portion of a stator assembly <NUM> is illustrated in a partially radial direction (i.e., at an angle about an engine centerline), in accordance with various embodiments. The stator assembly <NUM> may be in accordance with stator assembly <NUM> from <FIG>. The stator assembly <NUM> may include a compressor case <NUM> having a gas path surface <NUM>. Although described herein as including a compressor case <NUM>, any case having a gas path surface <NUM> effected due to wear is within the scope of this disclosure. For example, a turbine case experiencing wear may utilize the repair systems and methods disclosed herein, in accordance with various embodiments. In various embodiments, a gas path surface (e.g., gas path surface <NUM>) is on an OD case (e.g., OD case <NUM> of <FIG>) and an ID case (e.g., ID case <NUM>). Thus, in various embodiments, the gas path surface <NUM> of stator assembly <NUM> may be a radially inner surface of the compressor case <NUM> in response to the compressor case <NUM> being the OD case, and the gas path surface <NUM> of the stator assembly <NUM> may be a radially outer surface of the compressor case <NUM> in response to the compressor case <NUM> being an ID case. In various embodiments, the OD case <NUM> and/or the ID case <NUM> of stator assembly <NUM> from <FIG> may be in accordance with the compressor case <NUM>. In various embodiments, only the OD case <NUM> from <FIG> is in accordance with compressor case <NUM>.

In various embodiments, the compressor case <NUM> comprises a plurality of stator pockets <NUM> disposed in through the gas path surface <NUM> and into the compressor case <NUM>. In various embodiments, each stator pocket in the plurality of stator pockets <NUM> includes a counterbore (i.e., an aperture <NUM> and a pocket recess <NUM>). In various embodiments, the aperture <NUM> is configured to receive a shaft therethrough and the pocket recess <NUM> of each stator pocket in the plurality of stator pockets <NUM> is configured to interface with a mating portion <NUM> of a variable vane <NUM> of the stator assembly <NUM>. During operation of the variable stator over time, a pocket sidewall <NUM> of each stator pocket in the plurality of stator pockets <NUM> may wear to some extent. After a number of engine cycles for a gas turbine engine (e.g., gas turbine engine <NUM> from <FIG>) a portion of stator pockets in the plurality of stator pockets <NUM> may be repaired by a method and system disclosed herein.

For example, with reference now to <FIG>, the compressor case <NUM> after numerous cycles of gas turbine engine <NUM> from <FIG> is illustrated, in accordance with various embodiments. <FIG> includes the variable vanes (e.g., variable vane <NUM> from <FIG>) removed for clarity. In response to operation over time, the pocket sidewall <NUM> of each stator pocket in the plurality of stator pockets <NUM> may wear, creating a wear portion <NUM> for each stator pocket in the plurality of stator pockets <NUM>. In various embodiments, the wear portion <NUM> may be in a circumferential direction in pocket sidewall <NUM> and be disposed in a portion of the pocket sidewall <NUM> of a respective stator pocket in the plurality of stator pockets <NUM>.

Referring now to <FIG>, a cross-sectional view along section line A-A of a stator pocket <NUM> in the plurality of stator pockets <NUM> from <FIG> with a wear portion <NUM> is illustrated from <FIG> is illustrated, in accordance with various embodiments. The gas path surface <NUM> is disposed opposite a non-gas path surface in a radial direction. In various embodiments, the wear portion <NUM> is a recess <NUM> disposed in a pocket sidewall <NUM> of stator pocket <NUM> in the plurality of stator pockets <NUM> from <FIG> in a radially outward direction from a central axis defined by a respective aperture <NUM> (as shown in <FIG>) of stator pocket <NUM>. In various embodiments, the recess <NUM> defined by the wear portion <NUM> may have a complex geometry (i.e., having a radial portion, an axial portion, and a tangential portion relative to the central axis defined by the respective aperture <NUM> (as shown in <FIG>).

In various embodiments, the stator pocket <NUM> with the wear portion <NUM> of <FIG> may result in increased drag and efficiency loss for a stator assembly relative to a stator assembly prior to operation (e.g., as shown in <FIG>). The efficiency may be lost due to air flow through the wear portion <NUM> instead of through the engine section (e.g., engine section <NUM> from <FIG>). In addition, misalignment of the variable vane (e.g., variable vane <NUM> from <FIG>) may cause added allowable variation of the mating portion <NUM> of variable vane <NUM> from <FIG> in the stator pocket <NUM>. In this regard, the variable vane <NUM> may tip and cause the air to not hit the next blade (e.g., an aft blade <NUM> of stator <NUM> in <FIG>) at an intended angle, resulting in aerodynamic loss of compressor efficiency relative to a stator assembly without wear portion <NUM>. In various embodiments, the added variability in the aperture (e.g., aperture <NUM> from <FIG>) where the variable vane (e.g., variable vane <NUM> from <FIG>) are aligned and held in place reduces the rotation accuracy of the variable vane <NUM> about the central axis of the aperture <NUM>, also reducing efficiency and increasing leakage from the gas path surface <NUM>.

In various embodiments, the wear portion <NUM> may include a lip <NUM> defined by the gas path surface <NUM>, pocket sidewall <NUM> and a first wear surface <NUM> disposed radially adjacent the gas path surface <NUM>.

Referring now to <FIG>, a repair process <NUM> for repairing a plurality of stator pockets of a case for a variable stator assembly is illustrated, in accordance with various embodiments. The repair process <NUM> may include receiving the case (step <NUM>) and cleaning the case (step <NUM>). The case may be in accordance with stator assembly <NUM> as illustrated in <FIG> (i.e., after numerous cycles of engine operation with wear portions in each stator pocket of the plurality of stator pockets <NUM> from <FIG>).

The repair process <NUM> may further comprise measuring a wear depth for the wear portion of each pocket in the plurality of stator pockets (step <NUM>). In various embodiments, the wear depth measurement may be sent to a controller for a repair system, in accordance with various embodiments. For example, a wear depth may be measured for each pocket via a dimensional measurement gauge. The dimensional measurement gage may be in communication with a controller of the repair system (e.g., via a network connection, a hardwire connection, or the like). In various embodiments, in response to receiving the wear depth of a specific pocket in the plurality of pockets, the controller may associate the wear depth with the specific pocket for the repair process. For example, the wear depth of each pocket in the plurality of pockets may be measured in a predetermined order, then the plurality of pockets may be repaired in the same order, in accordance with various embodiments.

In various embodiments, the repair process <NUM> further comprises machining the lip of each pocket in the plurality of pockets (step <NUM>). In various embodiments, the lip of each pocket in the plurality of pockets may be machined based on the measured depth from step <NUM>. In this regard, only case material up to a depth of a respective wear portion for a specific pocket may be removed. In this regard, the repair process <NUM> may prevent excess case material from being removed (i.e., if lip were machined to a predetermined depth as opposed to a measured depth), in accordance with various embodiments.

In various embodiments, the repair process <NUM> may further comprise an inspection of the case (step <NUM>). In various embodiments, an inspection may ensure that the lip of each pocket in the plurality of pockets is removed to a sufficient depth (i.e. at or past the measured depth).

In various embodiments, the repair process <NUM> further comprises masking a portion of the case (step <NUM>). With brief reference to <FIG>, a compressor case <NUM> with a masked portion <NUM> (shown with cross-hatching) and an un-masked portion <NUM> is illustrated. With combined reference to <FIG> and <FIG>, the masked portion <NUM> may include the aperture <NUM> of each pocket in the plurality of stator pockets <NUM> and the gas path surface <NUM>, and the un-masked portion may include the pocket recess <NUM>, the pocket sidewall <NUM> and the wear portion <NUM> of each pocket in the plurality of stator pockets <NUM>. In various embodiments, masking the portion of the case may include ultraviolet (UV) masking, hard masking, or the like.

In various embodiments, the repair process <NUM> further comprises grit blasting the unmasked portion of the case (step <NUM>). In various embodiments, the unmasked portion may be prepared to receive a spray coating in response to the grit blasting.

In various embodiments, the repair process <NUM> further comprises spraying a coating into the wear portion of each pocket in the plurality of pockets (step <NUM>). In various embodiments, spraying the coating may comprise depositing a first layer in each pocket in the plurality of pockets, followed by depositing a second layer in each pocket in the plurality of pockets until a height of each pocket in the plurality of pockets is equal to or greater than the measured depth of each respective pocket in the plurality of pockets from step <NUM>. In various embodiments, the coating may comprise a nickel-aluminum plasma, a molybdenum-nickel-aluminum plasma, aluminum-graphite composite plasma, or the like. In various embodiments, the coating comprises nickel-aluminum plasma. In this regard, the thickness of the coating to be applied may not be limited, and the coating may include additional bonding ability compared to other spray coatings. In various embodiments, spraying the coating of step <NUM> may be performed via a double-wire feed and plasma arc additive manufacturing process (DFW-PAM).

In various embodiments, the repair process further comprises removing the masking (step <NUM>), a final machining (step <NUM>), and a visual and dimensional inspection (step <NUM>). The final machining and visual inspection may ensure the case is within predetermined tolerances of an original geometric tolerance of the originally manufactured case, in accordance with various embodiments.

Referring now to <FIG>, a control system <NUM> for repairing a wear portion of each pocket in a plurality of pockets of a case (e.g., compressor case <NUM> from <FIG>), in accordance with various embodiments. The control system <NUM> includes a controller <NUM> and a database <NUM>. The controller <NUM> may include one or more logic devices such as one or more of a central processing unit (CPU), an accelerated processing unit (APU), a digital signal processor (DSP), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like. In various embodiments, the controller <NUM> may further include any non-transitory memory known in the art. The memory may store instructions usable by the logic device to perform operations.

The control system <NUM> may further include a database or remote memory <NUM>. The database <NUM> integral to the control system <NUM> or may be located remote from the control system <NUM>. The controller <NUM> may communicate with the database <NUM> via any wired or wireless protocol. In that regard, the controller <NUM> may access data stored in the database <NUM>. The database <NUM> may be configured to receive wear depths of a wear portion for each pocket in a plurality of pockets of a case (e.g., compressor case <NUM> from <FIG>) from a gauge <NUM>. The gauge <NUM> may be configured to measure a wear depth of a wear portion of a pocket as described previously herein.

In various embodiments, the control system <NUM> may comprise a milling machine <NUM>. In this regard, the controller <NUM> may command the milling machine to mill a lip of a pocket in the plurality of pockets (e.g., the lip <NUM> from <FIG>) to a predetermined depth. In various embodiment the predetermined depth may be measured, as previously disclosed herein, or the predetermined depth may be determined any other way in the art, such as pre-setting a milling depth based on a maximum depth of a wear portion in the plurality of pockets. In various embodiments, the milling machine <NUM> may be integral with the control system <NUM> or a separate component. In various embodiments, milling may be performed manually, and the control system <NUM> may be for spraying step <NUM> from repair process <NUM> in <FIG> only.

The control system 600further comprises a coating spray torch <NUM> and a rotatable fixture <NUM>. The rotatable fixture <NUM> is configured to rotate relative to the coating spray torch <NUM>. The coating spray torch may be aligned with wear portion of a pocket disposed in a flow path surface of a case to be repaired (e.g., wear portion <NUM> from <FIG>).

In various embodiments, the wear depths may be measured manually and manually input into the database <NUM>. In various embodiments, the database <NUM> may store a location of each pocket in the plurality of pockets relative to a location of the rotatable fixture <NUM>. In this regard, the controller <NUM> may command the rotatable structure to a first position. The first position may align the coating spray torch with a wear portion of a pocket in the plurality of pockets (e.g., wear portion <NUM> from <FIG>). In various embodiments, the controller <NUM> may determine a total thickness to be deposited in the wear portion based on the first location and a stored depth for the wear portion. In various embodiments, the stored depth may be a measured depth (e.g., from gauge <NUM>), or a depth inputted into the database <NUM>. The controller <NUM> may then command the coating spray torch <NUM> to deposit a first layer in the wear portion and repeat the process for a next wear portion of an adjacent pocket in the plurality of pockets. The controller <NUM> may then rotate the rotatable fixture <NUM> to align the coating spray torch <NUM> to a second wear portion of the adjacent pocket in the plurality of pockets. The controller <NUM> may then repeat the determining the total thickness and depositing a first layer steps above.

In various embodiments, the controller <NUM> may repeat the process above until the wear portion of each pocket in the plurality of pockets is filled with the coating deposited from the coating spray torch <NUM>. In various embodiments, by depositing the coating in layers, as opposed to all at once, the coating may form a stronger bond with the case, in accordance with various embodiments.

Referring now to <FIG>, a repaired case <NUM> for a stator assembly (e.g., stator assembly <NUM>) is illustrated, in accordance with various embodiments. In various embodiments, the repaired case <NUM> includes the case <NUM> (e.g., compressor case <NUM> from <FIG> without the lip <NUM>) and a bonded coating <NUM>. In various embodiments, the bonded coating <NUM> may be configured to define a portion of a repaired gas path surface <NUM>.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the invention The scope of the invention is accordingly to be limited by nothing other than the appended claims and their legal equivalents, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

Claim 1:
A method for repairing a pocket (<NUM>) of a case (<NUM>) for a variable stator assembly (<NUM>), the method comprising:
receiving, via a processor, a plurality of wear depths, each wear depth in the plurality of wear depths corresponding to a wear portion (<NUM>) in a stator pocket in a plurality of stator pockets (<NUM>);
determining, via the processor, a plurality of thicknesses of a coating to be deposited based on the plurality of wear depths, each thickness of the coating in the plurality of thicknesses corresponding to the wear portion for each stator pocket in the plurality of stator pockets; and
commanding, via the processor, a coating spray torch (<NUM>) to deposit the coating in the wear portion of each stator pocket in the plurality of stator pockets,
characterised in that the commanding the coating spray torch to deposit the coating further comprises:
commanding, via the processor, the coating spray torch to deposit a first layer of the coating in a first pocket in the plurality of stator pockets;
commanding, via the processor, a rotatable fixture (<NUM>) to rotate the case and align the coating spray torch with a second pocket in the plurality of stator pockets; and
commanding, via the processor, the coating spray torch to deposit a second layer of the coating in the second pocket in the plurality of stator pockets.