Integral turbine outer ring low hardness seal coating, method of manufacture and protective tooling

Abstract

The application provides a whole turbine outer ring low-hardness sealing coating, a preparation method and a protection tool. The sealing coating comprises a dense metal bonding layer and a porous abradable sealing surface layer which are sequentially deposited on the surface of an alloy base; the main component of the dense metal bonding layer is NiCoCrAlY, and the components include 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al and 0.05-2 wt.% of Y. The sealing coating can effectively improve the wear condition of the blade, reduce the gas leakage amount and improve the efficiency of the aero-engine; and an eccentric spraying method is provided for the whole turbine outer ring, the coating preparation method and process parameters are optimized, the performance of the sealing coating of the whole turbine outer ring of the aero-engine is improved, so as to meet the more severe use requirements of the contemporary engine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of abradable seal coating, in particular to a whole turbine outer ring low-hardness seal coating, a preparation method and a protection tool. BACKGROUND

[0002] With the rapid development of the aviation field in China, the design of the aero-engine needs to pursue higher thrust-to-weight ratio, higher efficiency, lower energy consumption, longer life, etc., and the performance of some existing engines has already failed to meet the current demand. In recent decades, through the improvement of core temperature, the use of lightweight materials and the application of advanced structural design, the performance of gas turbine engines has been gradually improved. In addition, by controlling the gap between the rotating parts and the stationary parts in the turbomachinery, the goal of further improving the engine efficiency can be achieved. Ideally, the working medium of the engine should flow on the surface of the rotor along the expected airflow path. In fact, the gap between the rotor and the stator will produce a leakage flow, which bypasses the rotor tip and cannot contribute to the power output, ultimately resulting in a loss of overall efficiency. The traditional solution often adopts a conservative design, i.e. to retain a large gap, which not only leads to excessive tip leakage, but also generates vortex at the tip due to the interaction with the main airflow. Many studies have proven the impact of excessive gap on engine performance and efficiency. However, a small gap will inevitably cause friction and collision between the rotating blades and the casing, and ultimately lead to damage to multiple components, even catastrophic failure. In order to solve the above problems, in the compressor or turbine, an abradable seal coating is prepared by thermal spraying as an inner lining of the casing around the rotor tip.

[0003] At the same time, with the development of aero-engines, more and more guide vanes and turbine outer ring integrated structure designs have appeared. The whole turbine outer ring can significantly reduce the assembly difficulty and improve the assembly precision. The traditional seal coating is usually coated on the split turbine outer ring. For the whole turbine outer ring, the traditional split turbine outer ring seal coating preparation process cannot be directly used, otherwise problems such as pollution of non-sprayed surface, serious non-uniformity of coating thickness, etc. will occur.

[0004] In summary, how to develop and prepare a low-hardness seal coating for the whole turbine outer ring is a problem to be solved by those skilled in the art. SUMMARY

[0005] In view of the problems of pollution of non-spraying surface and serious unevenness of coating thickness of the integral turbine outer ring sealing coating, an integral turbine outer ring low-hardness sealing coating, a preparation method and a protection tool are provided in the embodiment of the application.The sealing coating can effectively improve the wear condition of the blade, reduce the gas leakage amount and improve the efficiency of the aero-engine.The preparation method and the process parameters are optimized, the performance of the integral turbine outer ring sealing coating of the aero-engine is improved, so as to meet the more stringent use requirements of the contemporary engine.

[0006] The embodiment of the application provides the following technical scheme: an integral turbine outer ring low-hardness sealing coating, the sealing coating comprises a dense metal bonding layer and a porous abradable sealing surface layer which are sequentially deposited on the surface of an alloy base body.

[0007] The main component of the dense metal bonding layer is NiCoCrAlY, and the components include 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al and 0.05-2 wt.% of Y; the main component of the porous abradable sealing surface layer is a metal coating or a ceramic coating.

[0008] According to an embodiment of the application, the porous abradable sealing surface layer adopts any one of an Al-Si-based sealing coating, a NiCoCrAlY-based sealing coating and a YSZ-based sealing coating, and the porous abradable sealing surface layer comprises 10-25 wt.% of polyphenyl ester.

[0009] According to an embodiment of the application, the porous abradable sealing surface layer adopts the NiCoCrAlY-based sealing coating, and the components of the NiCoCrAlY-based sealing coating include 30-60 wt.% of Ni, 15-30 wt.% of Co, 15-30 wt.% of Cr, 3-5 wt.% of Al and 0.05-2 wt.% of Y.

[0010] According to an embodiment of the application, the thickness of the dense metal bonding layer is 0.1-0.5 mm, and the standard deviation of the coating thickness of different parts is less than 20 mu m; the thickness of the porous abradable sealing surface layer is 0.2-1.5 mm, and the standard deviation of the coating thickness of different parts is less than 50 mu m.

[0011] The application further provides a preparation method of the integral turbine outer ring low-hardness sealing coating, mainly comprising the following steps:

[0012] Step 1, installing a spraying protection tool and pretreating the alloy base body surface of the turbine outer ring;

[0013] Step 2, preparing a dense metal bonding layer on the surface of the alloy substrate; the main component of the dense metal bonding layer is NiCoCrAlY, and the components include 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al, and 0.05-2 wt.% of Y;

[0014] Step 3, preparing a porous abradable seal surface layer on the dense metal bonding layer by atmospheric plasma spraying.

[0015] According to an embodiment of the present application, step 3 includes:

[0016] Step 3.1, loading the workpiece with the prepared dense metal bonding layer into a fixture and fixing it to an automatic rotary table;

[0017] Step 3.2, manually controlling the mechanical hand gun outlet to aim at the corresponding spraying position of the workpiece, and setting the motion trajectory, speed and other parameters of the mechanical hand;

[0018] Step 3.3, setting the spraying current to 180 A-250 A, the gas flow to Ar 20-70 slpm and H2 2-15 slpm, and preheating the workpiece to 80-200℃ after the plasma arc is stable;

[0019] Step 3.4, starting the powder feeder to deposit the porous abradable seal surface layer; the process parameters are set as follows: powder feeding rate 1-12 g / min, powder feeding angle 60-90°, powder feeding carrier gas rate 5-15 L / min, spraying power 15 kW-40 kW, spraying distance 60-150 mm, and deposition time 10 min-80 min; and the porous abradable seal surface layer is prepared;

[0020] Step 3.5, turning off the plasma gun to end the spraying; after the workpiece is cooled, post-processing operation is performed to polish and clean the non-spraying surface.

[0021] According to an embodiment of the present application, the eccentric spraying mode is used in step 3, that is, the position of the gun is offset from the center position of the circular turbine component, so that the spraying beam flow and the substrate surface of the turbine component form a non-orthogonal incident spraying mode.

[0022] According to an embodiment of the present application, during the spraying process of step 3, the turbine outer ring rotates on the rotary table at a speed of 30-90 r / min, and the tangent vector of the rotation direction and the flame vector direction has an included angle of <90°.

[0023] The present application also provides a spraying protection tool for an integral turbine outer ring low-hardness seal coating, which is used for shielding and protecting the non-spraying area, and the spraying protection tool comprises:

[0024] The assembly surface protection tooling is in a hollow ring shape and is fixedly assembled around the turbine outer ring for protecting the non-sprayed assembly surface area of the turbine outer ring, and the blade protection tooling is in a circular shape and is assembled in the central area of the turbine outer ring for protecting the blades in the middle of the outer ring; wherein the thickness of the blade protection tooling gradually decreases from the central area to the edge.

[0025] According to an embodiment of the present application, the thickness of the assembly surface protection tooling is 3-10 mm, and the thickness of the edge part of the blade protection tooling is 3-5 mm.

[0026] Compared with the traditional seal coating, the above-mentioned at least one technical solution adopted by the embodiments of the present specification can achieve at least the following beneficial effects:

[0027] (1) The embodiments of the present application optimize the coating composition to obtain a low-hardness seal coating, reduce the Al content, and increase the Co and Cr content, so as to ensure the high-temperature oxidation resistance of the coating while reducing the coating hardness to less than 65HR15Y.

[0028] (2) The embodiments of the present application design a blade protection tooling with a reinforcing rib or a variable thickness structure of "thick in the middle and thin at the edge", and use aluminum alloy and other materials with low internal stress, so as to effectively avoid the heat buckling deformation of the baffle during spraying and the shielding interference on the sprayed surface.

[0029] (3) The embodiments of the present application adopt the spraying technical path of "eccentric spraying + flame rotation + low power", successfully solve the problems of flame flow disorder, uneven thickness, particle sputtering and other problems encountered in the coating spraying process of the integral turbine outer ring, and realize the high-quality preparation of the seal coating of the integral turbine outer ring, so that the coating surface is smooth and the thickness is uniform. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 is a preparation method flowchart of the low-hardness seal coating of the integral turbine outer ring of the embodiments of the present application;

[0032] Figure 2 is a first schematic diagram of the rotation direction and eccentric spraying of the integral turbine outer ring of the embodiments of the present application;

[0033] Figure 3Figure 2 is a second schematic view of the rotating direction and eccentric spraying of the integral turbine outer ring according to an embodiment of the present application;

[0034] Figure 4 Figure 5 is a schematic view of an assembly surface protection tool according to an embodiment of the present application;

[0035] Figure 5 Figure 6 is a schematic view of a blade protection tool according to an embodiment of the present application;

[0036] Figure 6 Figure 7 is a schematic view of a blade protection tool provided with a reinforcing rib structure according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] The embodiments of the present application will be described in detail below with reference to the drawings.

[0038] The embodiments of the present application will be described in detail below with reference to the drawings.

[0039] The embodiments of the present application provide an integral turbine outer ring low-hardness sealing coating, which comprises a dense metal bonding layer and a porous abradable sealing surface layer deposited in sequence on the surface of an alloy base body; the main component of the dense metal bonding layer is NiCoCrAlY, and the components include 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al, and 0.05-2 wt.% of Y; and the main component of the porous abradable sealing surface layer is a metal coating or a ceramic coating.

[0040] The embodiments of the present application are prepared by using an atmospheric plasma spraying method. The thickness of the dense metal bonding layer is 0.1-0.5 mm, and the standard deviation of the coating thickness at different positions is less than 20 μm; and the thickness of the porous abradable sealing surface layer is 0.2-1.5 mm, and the standard deviation of the coating thickness at different positions is less than 50 μm. The thickness of the porous abradable sealing surface layer can be more than 1 mm, the coating thickness at different positions is uniform, the standard deviation is not more than 50 μm, and the prepared coating surface is smooth, and the roughness Ra is 6.3-12.5 μm.

[0041] In some embodiments of the present application, the porous abradable seal surface layer uses any one of Al-Si-based seal coating, NiCoCrAlY-based seal coating, YSZ-based seal coating, wherein the porous abradable seal surface layer includes 10-25 wt.% of polystyrene. The porous abradable seal surface layer uses 10 wt.%-25 wt.% of polystyrene as a pore-forming agent to improve the porosity of the coating. The mass fraction of polystyrene needs to be analyzed according to the actual service conditions and blade materials to balance the bonding strength and the abradable performance.

[0042] In the embodiments of the present application, the porosity of the porous abradable seal surface layer is greater than 30%, the bonding strength is greater than 10 MPa, and the surface Rockwell hardness is less than 65 HR15Y.

[0043] In one embodiment of the present application, the porous abradable seal surface layer uses a NiCoCrAlY-based seal coating, wherein the components of the NiCoCrAlY-based seal coating include 30-60 wt.% of Ni, 15-30 wt.% of Co, 15-30 wt.% of Cr, 3-5 wt.% of Al, and 0.05-2 wt.% of Y. The components of the NiCoCrAlY-based seal coating are NiCoCrAlY and 15 wt.% of polystyrene. The NiCoCrAlY has a lower Al content and a higher Co and Cr, which maintains the high-temperature oxidation resistance of the coating while reducing the content of β-hard phase, thereby further reducing the hardness of the coating.

[0044] In a preferred embodiment, the components of the porous abradable seal surface layer NiCoCrAlY are: 50-60 wt.% of Ni, 15-20 wt.% of Co, 15-20 wt.% of Cr, 3-5 wt.% of Al, and 0.05-2 wt.% of Y.

[0045] In a preferred embodiment, the components of the dense metal bond layer NiCoCrAlY are: 50-60 wt.% of Ni, 10-12 wt.% of Co, 10-12 wt.% of Cr, 7-10 wt.% of Al, and 0.05-2 wt.% of Y, which is prepared by atmospheric plasma spraying.

[0046] The dense metal bond layer and the porous abradable seal surface layer are both NiCoCrAlY, but the specific components are different. The characteristic of the porous abradable seal surface layer is that the Al content is low and the Co and Cr contents are high, which can achieve the goal of reducing the hardness of the surface layer.

[0047] As shown in Figure 1 The embodiments of the present application also provide a preparation method of the integral turbine outer ring low-hardness seal coating, mainly including the following steps:

[0048] Step 1, install the spray protection tooling and pretreat the alloy substrate surface of the turbine outer ring;

[0049] Step 2, prepare a dense metal bond layer on the alloy substrate surface; the main component of the dense metal bond layer is NiCoCrAlY, and the components include 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al, and 0.05-2 wt.% of Y;

[0050] Step 3, prepare a porous abradable seal surface layer on the dense metal bond layer by atmospheric plasma spraying.

[0051] In specific implementation, the alloy substrate surface pretreatment includes operations such as removal of surface grease and stains, sandblasting, and the like. Before sandblasting, the protection tooling needs to be installed to avoid roughening of the non-sprayed surface.

[0052] In some embodiments of the present application, step 3 includes:

[0053] Step 3.1, load the workpiece with the prepared dense metal bond layer into a fixture and fix it to an automatic rotating table;

[0054] Step 3.2, manually control the mechanical hand spray gun outlet to aim at the corresponding spray position of the workpiece, and set the motion trajectory, speed, and the like of the mechanical hand;

[0055] Step 3.3, set the spraying current to 180 A-250 A, the gas flow rate to Ar 20-70 slpm and H2 2-15 slpm, and preheat the workpiece to 80-200℃ after the plasma arc is stabilized;

[0056] Step 3.4, start the powder feeder to deposit the porous abradable seal surface layer; the process parameters are set as follows: powder feeding rate 1-12 g / min, powder feeding angle 60-90°, powder feeding carrier gas rate 5-15 L / min, spraying power 15 kW-40 kW, spraying distance 60-150 mm, and deposition time 10 min-80 min; and a porous abradable seal surface layer with a thickness of 100-1500 μm is prepared;

[0057] Step 3.5, turn off the plasma spray gun to end the spraying; after the workpiece is cooled, perform post-processing operations to polish and clean the non-sprayed surface.

[0058] In some embodiments of the present application, as Figures 2-3As shown, the eccentric spraying mode in step 3 is that the spraying gun position is deviated from the center position of the circular turbine component, the spraying beam is non-orthogonal to the base surface of the turbine component, and the plasma flame is at an angle of 20-80° with the spraying surface of the workpiece. The spraying mode can effectively slow down the flame rebound and turbulence at the junction of the tool and the outer ring, and solve the problem of uneven coating thickness on the upper and lower parts of the outer ring.

[0059] In some embodiments of the application, in the spraying process of step 3, the turbine outer ring rotates on the rotating table at a speed of 30-90 r / min, and the tangent vector of the rotating direction and the flame vector direction is at an angle of <90°.

[0060] The preparation method of the embodiment of the application adopts the scheme of "eccentric spraying + along-flame rotation + low power", solves the problems of flame turbulence, uneven thickness, particle sputtering and the like in the coating spraying process of the integral turbine outer ring, and realizes the high-quality preparation of the integral turbine outer ring sealing coating, and the coating surface is smooth and the thickness is uniform.

[0061] As shown in Figures 4-5 The spraying protection tool for the integral turbine outer ring low-hardness sealing coating also provided by the embodiment of the application is used for shielding and protecting the non-spraying area, so as to avoid the pollution of the non-spraying area such as the blade and the assembly surface. The spraying protection tool comprises an assembly surface protection tool and a blade protection tool. The assembly surface protection tool is in the form of a hollow ring and is fixed to the turbine outer ring, and is used for protecting the non-spraying assembly surface area of the turbine outer ring. The blade protection tool is in the form of a circle and is assembled to the central area of the turbine outer ring, and is used for protecting the blade in the central area of the outer ring. The thickness of the blade protection tool gradually decreases from the central area to the edge.

[0062] The sealing coating protection tool of the embodiment of the application mainly shields and protects the non-spraying area, so as to avoid the pollution of the non-spraying area such as the blade and the assembly surface. The tool structure design needs to be combined with the workpiece size and the thermal spraying angle. On the one hand, the tool needs to fully protect the non-spraying area as much as possible, and on the other hand, the tool cannot shield the spraying area and cannot affect the coating quality of the spraying area.

[0063] In the implementation, the tool structure design needs to be combined with the workpiece size and the thermal spraying angle. On the one hand, the tool needs to fully protect the non-spraying area as much as possible, and on the other hand, the tool cannot shield the spraying area and cannot affect the coating quality of the spraying area. The following formula can be used to preliminarily calculate the rigidity of the circular thin-walled tool:

[0064] D = E * h³ * I / 12

[0065] Where, stiffness (D) is related to material elastic modulus (E), cross-section moment of inertia (I) and thickness (h). In actual engineering, the stiffness performance under complex thermal load boundary conditions and irregular structures needs to be combined with finite element analysis or experimental verification; if there are reinforcing ribs and other structures, their contribution needs to be calculated additionally.

[0066] In specific implementation, the assembly surface protection tooling is in the form of a hollow ring, and the material can be stainless steel, aluminum alloy, heat-resistant steel, etc., with uniform thickness, large stiffness and not easy to deform, and the thickness can be 3-10 mm. The blade protection tooling is in the form of a circle, and the diameter depends on the size of the workpiece, about 100-500 mm, and the material includes but is not limited to stainless steel, aluminum alloy, heat-resistant steel, etc. To avoid blocking the spraying surface, the thickness of the edge part cannot be too large, about 3-5 mm; to ensure that the heat does not cause buckling deformation, the tooling uses reinforcing ribs, variable thickness and other means to improve the stiffness of the blade protection tooling, and at the same time, aluminum alloy materials with small internal stress are preferentially used, or materials such as annealed stress-relieved heat-resistant steel are considered.

[0067] In some embodiments of the present application, the assembly surface protection tooling uses a combination of "screw + 0.1 mm gasket + nut" to precisely adjust the distance between the tooling and the workpiece, which is simple to operate and easy to adjust to the optimal distance.

[0068] Example one: preparation of a 1000℃ abrasion-resistant seal coating for a GH4169 high-temperature alloy integral turbine outer ring, including the following contents:

[0069] (1) Coating material system: according to the target use temperature and performance requirements, this embodiment plans to use the technical route of atmospheric plasma spraying "adhesion layer dense NiCoCrAlY + seal surface layer NiCoCrAlY-based seal surface layer". The target thickness of the adhesion layer is 0.2 mm, and the target thickness of the seal surface layer is 1 mm. At the same time, considering the demand for low hardness and high bonding strength, the coating composition is optimized and selected as follows:

[0070] (2) The adhesion layer dense NiCoCrAlY composition is: 50-60 wt.% of Ni, 10-15 wt.% of Co, 10-15 wt.% of Cr, 5-10 wt.% of Al, and 0.05-2 wt.% of Y, prepared by atmospheric plasma spraying.

[0071] (3) The surface layer of the NiCoCrAlY-based seal coating is composed of NiCoCrAlY+15% wt.% polyphenyl ester, wherein the NiCoCrAlY has a lower Al content and a higher Co and Cr, so as to maintain the high-temperature oxidation resistance of the coating while reducing the content of β hard phase and further reducing the hardness of the coating. The NiCoCrAlY specifically contains 50-60 wt.% of Ni, 15-20 wt.% of Co, 15-20 wt.% of Cr, 3-5 wt.% of Al, and 0.05-2 wt.% of Y.

[0072] (4) The structure of the assembly surface protection tooling is designed, and the assembly surface protection tooling is located around the outer ring of the turbine and is mainly used for protecting the assembly surface area of the outer ring which is not sprayed; the blade baffle is located in the central area of the outer ring of the turbine and is mainly used for protecting the middle blade of the outer ring from being polluted.

[0073] (5) The assembly surface protection tooling is in the form of a hollow ring, and the material thereof is usually stainless steel with an inner diameter of 370 mm, an outer diameter of 400 mm, and a thickness of 5 mm.

[0074] (6) The blade protection tooling is in the form of a circle with a diameter of 370 mm, and the material thereof is aluminum alloy with a thickness of 3 mm at the edge part; in order to ensure that the blade protection tooling does not deform due to heat, the tooling is designed to have a variable thickness structure as shown in the drawing, i.e., the middle part is thick and the edge part is thin, so as to improve the rigidity of the blade protection tooling. Figure 5

[0075] (7) Alcohol and degreasing cotton are used to clean the surface of the workpiece to be sprayed.

[0076] (8) The tooling is installed, the number of stainless steel gaskets is adjusted to adjust the distance between the tooling and the workpiece to 5 mm, and the tooling is fastened by using bolts.

[0077] (9) White corundum is used to pretreat the surface of the spraying area to improve the bonding force between the coating and the substrate, the particle size of the white corundum used is 60 mesh, the sandblasting pressure is 0.2-0.5 MPa, the sandblasting angle is 80°, and the sandblasting time is 30 min, so that the surface roughness of the sprayed state reaches Ra 5.0 μm-Ra 7.0 μm.

[0078] (10) A screw is used to fix the outer ring of the turbine on the rotary table, and the rotary table is continuously rotated at a speed of 60 r / min during the spraying process, so as to ensure that the circumferential coating thickness is uniformly distributed.

[0079] ​(11) Set the spraying path. Since the shielding and protection fixture is very close to the outer ring and the coating thickness is thin due to flame rebound at the root of the outer ring, an eccentric spraying path is required. The spray gun is located at 1 / 4 of the diameter of the turbine outer ring. The plasma flame and the workpiece rotation tangent vector are at an angle of 60°. The spray gun is scanned up and down at a speed of 5 mm / min. One up and down scan is counted as one cycle. The number of cycles is set to 60 according to the coating thickness requirements.

[0080] (12) A dense metal bonding layer NiCoCrAlY ~0.2 mm was prepared on the alloy substrate.

[0081] (13) Select appropriate spraying process parameters and prepare a wearable sealing surface layer by spraying. Spraying power ~25kW, spraying distance ~100 mm, spraying current ~200 A, gas flow rate of Ar ~50 slpm, H2 ~4 slpm, after the plasma arc stabilizes, preheat the workpiece to ~180℃; powder feeding rate ~4 g / min, powder feeding angle 90°, powder carrier gas rate ~5L / min, deposition time ~80 min; a porous wearable sealing surface layer with a thickness of ~1 mm is obtained.

[0082] (14) After the coating is applied, the coating thickness is measured using a micrometer. Measurements are recorded at different locations. The results are shown in Table 1.

[0083] (15) Post-processing: remove the covering tooling and high-temperature tape, etc., and polish the small amount of coating on the assembly surface.

[0084] Table 1 Coating thickness values

[0085]

[0086] As shown in Table 1, it can be seen that the wear-resistant sealing layer is very close to the target thickness of 1mm, and the average thickness of the upper and lower parts is only 0.022mm, which fully meets the requirements.

[0087] Example 2: Design of protective tooling structure

[0088] The steps for designing the protective tooling structure in (4) of Example 1 will be described in detail.

[0089] (1) Determine the protection area and size: Analyze the area to be sprayed and the area to be protected on the workpiece, determine the shape and size of the protective fixture, and determine that the assembly surface protective fixture is a hollow ring with an inner diameter of 370 mm and an outer diameter of 400 mm; the blade protective fixture is circular with a diameter of 370 mm.

[0090] (2) Determine the constraint boundary conditions: the assembly surface protection tool only has an inner diameter constraint of 370 mm, and there is no constraint in the outer diameter and thickness directions. The outer diameter of the blade protection tool is constrained to 370 mm, and a thickness exceeding 3 mm will cause the to-be-sprayed area to be blocked, so the maximum thickness is selected to be 3 mm.

[0091] (3) Preliminary calculation of tool stiffness according to the following formula:

[0092] D = E * h³ * I / 12

[0093] wherein the stiffness (D) is related to the material elastic modulus (E), the cross-sectional moment of inertia (I), and the thickness (h).

[0094] (4) Workpiece stiffness evaluation combined with finite element analysis: The stiffness performance under complex thermal load boundary conditions and irregular structures is verified by combining finite element analysis. It is found through analysis that the assembly surface protection tool stiffness in this scheme is sufficient to resist thermal stress, while the blade protection tool stiffness is insufficient, and the blade protection tool may deform during thermal spraying. On the one hand, it causes the to-be-sprayed area to be blocked, and on the other hand, it may cause the protection of the to-be-protected area to be insufficient, so structural optimization is required.

[0095] (5) Tool structure optimization: The tool design is shown in Figure 5 The variable thickness structure of "thick in the middle and thin at the edges" improves the stiffness of the blade protection tool. Another reinforcing rib structure can be designed as shown in Figure 6 which satisfies the boundary constraint conditions while improving the stiffness of the tool.

[0096] (6) Finite element analysis and experimental verification: The optimized tool structure is first verified by finite element analysis for stiffness performance under complex thermal load boundary conditions and irregular structures; then a simulated spraying experiment is carried out, the workpiece is preheated to a spraying temperature of 200°C, and it is observed that the tool does not deform, which meets the requirements.

[0097] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed in the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a low-hardness sealing coating for an integral turbine outer ring, characterized in that, The main steps include: Step 1: Install the spraying protective fixture and pre-treat the alloy substrate surface of the turbine outer ring; Step 2: Prepare a dense metal bonding layer on the surface of the alloy substrate; the composition of the dense metal bonding layer is NiCoCrAlY, with components of 50-60 wt.% Ni, 10-15 wt.% Co, 10-15 wt.% Cr, 5-10 wt.% Al, and 0.05-2 wt.% Y; Step 3: A porous, wearable sealing layer is prepared on the dense metal bonding layer using atmospheric plasma spraying. The porous, wearable sealing layer is a NiCoCrAlY-based sealing coating, which includes 10-25 wt.% polystyrene. The composition of the NiCoCrAlY-based sealing coating is 30-60 wt.% Ni, 15-30 wt.% Co, 15-30 wt.% Cr, 3-5 wt.% Al, and 0.05-2 wt.% Y. The thickness of the dense metal bonding layer is 0.1~0.5 mm, and the standard deviation of the coating thickness in different parts is less than 20 μm; the thickness of the porous wear-resistant sealing surface layer is 0.2~1.5 mm, and the standard deviation of the coating thickness in different parts is less than 50 μm. In step 3, an eccentric spraying method is adopted. The eccentric spraying method is to offset the position of the spray gun from the center of the circular turbine component, so that the spray beam and the substrate surface of the turbine component form a non-orthogonal incident spraying method.

2. The preparation method according to claim 1, characterized in that, Step 3 includes: Step 3.1: Place the workpiece with the prepared dense metal bonding layer into the fixture and fix it on the automatic rotary table; Step 3.2: Manually control the robot arm's spray gun outlet to align with the corresponding spraying position on the workpiece, and set the robot arm's movement trajectory and speed parameters; Step 3.3: Set the spraying current to 180 A~250 A, the gas flow rate to Ar 20~70 slpm, H2 2~15 slpm, and after the plasma arc stabilizes, preheat the workpiece to 80~200℃. Step 3.4: Start the powder feeder and deposit a porous abrasive sealing layer; the process parameters are set as follows: powder feed rate 1-12 g / min, powder feed angle 60-90°, powder carrier gas rate 5-15 L / min, spraying power 15kW-40kW, spraying distance 60-150 mm, and deposition time 10 min-80 min; a porous abrasive sealing layer is thus formed. Step 3.5: Turn off the plasma spray gun to end the spraying process; after the workpiece has cooled down, perform post-processing operations, such as grinding and cleaning the non-sprayed surfaces.

3. The preparation method according to claim 1, characterized in that, During the spraying process in step 3, the turbine outer ring is rotated on the rotary table at a speed of 30~90 r / min, and the angle between the tangent vector of the rotation direction and the flame vector direction is <90°.

4. A spraying protective fixture for use in the preparation method according to any one of claims 1 to 3, used to shield and protect non-sprayed areas, characterized in that, The spray-coating protective fixture includes: The assembly surface protection fixture and the blade protection fixture are provided. The assembly surface protection fixture is a hollow ring and is fixedly mounted around the outer ring of the turbine to protect the non-painted assembly surface area of ​​the outer ring of the turbine. The blade protection fixture is circular and is mounted in the central area of ​​the outer ring of the turbine to protect the blades in the middle of the outer ring. The thickness of the blade protection fixture gradually decreases from the central area to the edge.

5. The spray coating protective fixture according to claim 4, characterized in that, The thickness of the assembly surface protection fixture is 3~10 mm, and the thickness of the edge part of the blade protection fixture is 3~5 mm.

Images