Method for repairing TW-7 coating of aero-engine duct

Abstract

The invention discloses a repairing method for a TW-7 coating of an aero-engine duct. The repairing method comprises the following specific steps: (1) preparing materials; (2) test work; (3) obtaining a test result and discussing; the method has the advantages that according to the shape structure and the coating performance of the conduit, the coating repairing technology research is developed, and finally, the self-repairing production of the TW-7 coating on the surface of the conduit is realized. According to the method, the size and structural characteristics of the conduit are fully considered, and the coating requirements of the coating are also fully considered, so that the coating repairing method is successfully researched. The method is very practical, guide pipes with TW-7 coatings of various models of aero-engines can be designed for reference, and the method not only can be applied to the field of aero-engines, but also can be widely applied to various industries.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of machinery, in particular to a spraying repair method, more particularly to a spraying repair method for an aero-engine duct. BACKGROUND

[0002] An aero-engine duct is installed in the outer duct of an engine, and the working temperature is about 300 DEG C. The guide pipe on one side needs to be sprayed with TW-7 anticorrosive coating, and the specific position is shown in the figure. In the use process, it is found that cracks appear in the weld, especially when used in the marine environment, the frequency of cracks is higher. In the fault repair process, it is found that the surface coating often falls off, and some even fall off completely, and the scrap rate of the parts caused by the coating falling off is very high. Figure 1 SUMMARY

[0003] To solve the above technical problems, the present application adds TW-7 coating anticorrosion treatment on the surface of the duct to improve the corrosion resistance of the part; the aero-engine duct with TW-7 coating falling off is repaired by recoating TW-7 coating after removing the coating, so as to improve the repair qualification rate of the part, reduce the repair cost, and improve the working quality and efficiency. The specific technical scheme is as follows: A TW-7 coating repair method for an aero-engine duct, and the specific steps of the repair process are as follows: (1) Material preparation; Prepare TW-7 coating, performance test sample and auxiliary supplies, and only test pieces with unqualified coating appearance quality; (2) Test work; (2.1) Process preparation; Prepare the overhaul process card, and the main process flow is: 5 label → 10 fault inspection → 15 fault repair → 20 fluorescent inspection → 25 spraying → 30 J liquid pressure test → 35 cleaning → 40 J final inspection; Prepare the spraying TW-7 process specification, and the coating position of the part and the acceptance technical requirements are clear; the main process flow of the repair is: protect the non-spraying surface → remove the coating → spray the primer → curing → light sanding → spray the sealing layer → inspection; (2.2) Paint spraying process test; (2.2.1) Design protection tooling; The protection tooling includes a pair of nut joints, a clamp and adhesive tape, the pair of nut joints can rotate and fix the nut at the top end of the duct, the clamp fixes the ball head through the clamp, and the adhesive tape wraps and covers the non-spraying surface; (2.2.2) Remove the coating; Remove the original coating by sandblasting; (2.2.3) Spray TW-7 primer and curing;​ (2.2.4) Light sanding; (2.2.5) Spraying of topcoat (sealing layer) and curing; (3) Test results and discussion; (3.1) Appearance quality inspection; (3.2) Adhesion test; (3.3) Thickness test; (3.4) Insulation test; (3.5) Hydraulic pressure test.

[0004] In step (2.2.1), the protective tooling material is TC4 titanium alloy with certain high temperature resistance and relatively soft hardness.

[0005] The specific steps of removing the original coating by sanding are as follows: The sanding process parameters of the coating removal are specified according to the typical process "TW-7 water-based high temperature resistant coating", that is, 120-220 mesh alumina sand is used to sand the coating surface, the pressure is 0.2-0.55 MPa, the distance from the nozzle to the part is 100-200 mm, the surface coating of the part is completely cleaned, then the residual sand and dust are blown off with anhydrous and oil-free compressed air; the time interval from sanding to spraying the primer is strictly controlled to be no more than 6 h; after sanding is completed, the sanding end time and the paint spraying start time are recorded.

[0006] The specific method of step (2.2.3) is as follows: The temperature between paint spraying is strictly controlled to be 15-30°C, and the relative humidity is 35-60%; SATA or similar spray gun is used, the spraying distance is controlled to be 100-200 mm, the spraying pressure is 0.2-0.3 MPa, and the spraying angle is perpendicular to the surface of the part; first, a thin and uniform layer is coated, the air dried to be matt gray, then the second layer is coated, which is light green in wet state and gray after air drying, thus a coating layer of 38-41 µm is obtained; When further coating is required, the above operation is repeated; if a coating layer of 40 µm-75 µm is required, it usually needs to be coated 3-4 times; after the primer spraying is completed, the high temperature protective tape on the surface of the part is removed first, and then the paint layer is cured at 190±5°C for at least 1 h, then the part is heated to 350±5°C for 1 h to make the paint layer completely cured, at this time the paint layer is not conductive.

[0007] The specific method of step (2.2.4) is as follows: In order to make the primer conductive and increase the bonding force between the primer and the sealing surface layer, sandblasting treatment is needed before spraying the sealing surface layer; the sandblasting pressure is controlled between 0.1-0.2 MPa, and other parameters are carried out according to step 2.2.2; the coating color of the coating area is matt gray, and the conductivity is qualified, that is, the resistance value is not more than 15 Ω / 125 mm; the surface of the coating after sandblasting is continuously sprayed with the surface layer, the time interval between sandblasting and spraying the sealing layer is ≤4 h, and if it is greater than 4 h, the sandblasting treatment is re-performed; and the sandblasting end time and the surface coating spraying start time are recorded.

[0008] Step (2.2.5) The specific method of spraying the surface coating sealing layer and curing is: Put the TW-7 high-temperature resistant coating surface coating into the spray gun hopper, adjust the spraying pressure to 0.1-0.2 MPa, the nozzle distance from the part is 100-200 mm, uniformly spray a layer of surface coating material on the surface of the primer coating of the part, the coating thickness is about 3-8 μm, and the color is uniform green; The part should be air-dried at room temperature for 10-30 min, then put into the oven, and uniformly raise the temperature to 80-100℃, keep for 30 min, then take out and remove all high-temperature resistant protection; after finishing, put the finished part into the drying oven, raise the temperature to 350℃±5℃ with the oven, keep for not less than 0.5 h, then open the oven door and air cool.

[0009] Step (3.1) The specific method of appearance quality inspection is: The pipe appearance quality inspection standard requires: visually inspect the two pipes coated with green TW-7 coating, the total area of coating missing is not more than 1.5 cm2, and the number is unlimited; if it exceeds the standard, re-coat or spray TW-7 coating; visually inspect the brazing seam and argon arc welding seam surface, and the coating missing is not allowed; use a 10 times magnifying lens to inspect the brazing seam and argon arc welding seam surface of the two pipes covered with coating, that is, the brazing seam and argon arc welding seam position on the lower half "П" type pipe is not allowed to have cracks; the actual detection result meets the above requirements, the coating is green, the surface is uniform, continuous, complete and has strong adhesion, and has no peeling, blistering and peeling phenomenon; all surfaces of the part have no residues caused by sandblasting, protection and other processing processes.

[0010] Step (3.2) The bonding force detection method is: According to GB / T9286 standard, the bonding force is checked on a steel test piece with a size of 50 mm×100 mm by grid sticking method, the coating in the middle of the grid has no peeling phenomenon, the bonding force reaches level 1, which meets the requirement of not more than level 2 in the standard.

[0011] Step (3.3) The thickness detection method is: The thickness of the coating is checked by using a vortex thickness gauge on a test piece sprayed at the same time as the part, and the test result is in the range of 40 µm to 75 µm; The insulation detection method of step (3.4) is: One of the two probes of the multimeter is placed on the exposed metal surface, and the other is placed on the coating, and the distance between the two probes is not more than 125 mm; if the above requirement cannot be met due to some reason, the two probes are allowed to be placed on the coating, and the distance between the two probes is not less than 25 mm, the data is read and recorded, and then the two probes are moved to other positions for continuous measurement; The liquid pressure test detection method of step (3.5) is: According to the design drawing and repair file, the sealing of the conduit is checked by using a conduit liquid pressure tester; the working liquid pressure in the test system is 6.5 MPa, and the sealing of the conduit, each weld and the main body is checked for 5 minutes, and the pressure is not allowed to decrease and the working liquid is not allowed to seep out at the connection part; if the weld and the main body have leakage, the part is scrapped.

[0012] The advantages of the present application are as follows: on an aero-engine, the pipeline system is mainly used for conveying fuel oil, lubricating oil and air medium, and is an important component of the engine. The conduit cannot be repaired deeply because it originally does not have coating repair capability. In the case of no spare parts and string resources, the engine repair progress will be seriously affected, and the repair cost will increase and the qualified rate will decrease due to replacement of new products. Therefore, according to the shape structure and coating performance of the conduit, coating repair technology research is carried out, and finally the self-repair production of TW-7 coating on the surface of the conduit is realized. Due to the special and complex structure of the aero-engine conduit, the problem of coating surface protection needs to be solved, and a protection clamp is specially designed. It is verified that this method is stable in quality, and effectively solves the on-site problem.

[0013] The present method not only fully considers the size and structural characteristics of the conduit, but also fully considers the coating requirements of the coating, so that the coating repair method is successfully researched. This method is very practical, and the TW-7 coated conduits of various types of aero-engines can be designed for reference, which can not only be used in the field of aero-engines, but also can be widely applied in various industries. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a schematic diagram of the coating position of TW-7 coating; Figure 2 It is a schematic diagram of the position of the stringable nut and the ball head; Figure 3-1 It is a schematic diagram of the fixed stringable nut and nut joint; Figure 3-2 It is a schematic diagram of the fixed clamp and ball head; Figure 4 It is a photograph of the state of the conduit after spraying. Detailed Implementation

[0015] The present invention will be described in detail below with reference to the accompanying drawings. The specific steps of the coating repair process are as follows: 1. Material preparation Prepare TW-7 coating, performance test specimens, and auxiliary materials for testing. Also provide test pieces that, after disassembly and inspection, only show defects in the coating's appearance quality.

[0016] 2. Experimental work 2.1 Process Preparation The main process flow for compiling the overhaul process card is as follows: 5. Labeling → 10. Fault inspection → 15. Fault repair → 20. Fluorescent inspection → 25. Spraying → 30. Hydraulic test → 35. Cleaning → 40. Final inspection.

[0017] A TW-7 spray coating process specification was developed, clarifying the coating locations and acceptance technical requirements for the parts. The main repair process flow is as follows: protect non-sprayed surfaces → remove coating layer → spray primer → cure → light sandblasting → spray sealing layer → inspection.

[0018] 2.2 Spray Painting Process Test 2.2.1 Design protective tooling One end of the conduit has two movable nuts. During the spraying operation and handling, the movement of these nuts can affect the surface quality of the TW-7 coating. In addition, the other end of the conduit is connected to a ball head, which rotates freely and cannot be fixed during the painting operation, easily leading to over-blowing or over-spraying of parts.

[0019] In summary, considering the requirements of the part's material, structure, and curing process, TC4 titanium alloy, which has certain high-temperature resistance and relatively soft hardness, was selected. A movable nut fixing and protective fixture was designed and manufactured to ensure that the movable nut does not damage the coating during sandblasting, spraying, and curing. Simultaneously, to prevent the ball joint on the part from rotating and affecting the painting operation, a small clamp was used to fix one end of the ball joint, ensuring that the part does not rotate during the painting process.

[0020] After the moving parts on the conduit are fixed, use 2975-R (Saint-Gobain brand) high-temperature resistant protective tape to protect them and prevent over-blowing or over-spraying of the non-coated surfaces of the parts.

[0021] 2.2.2 Removal of coating When the parts are repaired, it is found that the coating is seriously aged, has different degrees of peeling, the peeling area exceeds the standard requirement, and some even completely peel off. Therefore, before spraying the TW-7 coating, the original coating needs to be thoroughly cleaned. The shape of the part is complex, with holes, grooves, gaps and internal cavities and other structures. If chemical method is used to remove the coating, the solution is easy to enter the inside of the part, which is difficult to clean thoroughly, and there is no suitable detection means. Therefore, the sandblasting method is used to remove the original coating of the guide pipe part.

[0022] According to the sandblasting method coating removal process parameters of the typical process “TW-7 water-based high-temperature resistant coating”, that is, using 120-220 mesh alumina sand to sandblast the coating surface, the pressure is (0.2-0.55) MPa, the distance from the nozzle to the part is (100-200) mm, and the coating on the surface of the part is completely removed. Then use anhydrous and oil-free compressed air to blow off the residual sand and dust. The time interval between sandblasting and spraying the primer should be strictly controlled to be no more than 6 h. If the time interval is too long, the sandblasted surface will be oxidized or contaminated, thereby affecting the adhesion and durability of the coating. Therefore, if the time interval between sandblasting and painting exceeds 6 h, the sandblasting process needs to be performed again. After sandblasting is completed, record the sandblasting end time and the painting start time.

[0023] 2.2.3 Spray TW-7 primer and curing Primer coating is an important part of the painting process, which can improve the adhesion and corrosion resistance of the coating. TW-7 primer is a water-based paint, so the temperature and humidity of the painting environment need to be strictly controlled to (15-30) °C and (35-60) %, respectively, to avoid quality problems such as “wet back” and “virtual smoke” of the coating.

[0024] Use SATA or similar spray gun, control the spraying distance to be (100-200) mm, the spraying pressure to be (0.2-0.3) MPa, and the spraying angle to be perpendicular to the surface of the part as much as possible. First, evenly coat a thin layer, and then air dry to a matte gray color. Then, coat a second layer, which is light green in wet state and gray in air dry state. In this way, a coating of about 40 µm can be obtained.

[0025] When further coating is required, repeat the above operation. If a coating of 40 µm to 75 µm is required, usually 3-4 coats are needed. If there are surface defects before curing, use clean water to remove the coating, and then re-coat. For surfaces that cannot be protected, allow the paint layer to be sprayed first, and then use a lint-free cotton cloth to remove most of the paint layer on the non-coated surface with water.

[0026] After the primer is sprayed, first cure at 190±5 °C for at least 1 h, then remove the high-temperature protective tape on the surface of the part, continue to heat to 350±5 °C for 1 h, and make the paint layer completely cured. At this time, the paint layer is not conductive.

[0027] 2.2.4 Light sanding In order to make the primer conductive and increase the adhesion between the primer and the sealing surface, sanding treatment is required before spraying the sealing surface. The sanding pressure is strictly controlled between (0.1-0.2) MPa, and other parameters are carried out according to Clause No. 2.2.2. Sand the coating area for the shortest time, and the coating color is matte gray, and the conductivity is qualified, that is, the resistance value does not exceed 15 Ω / 125 mm. After sanding, blow the surface clean of sand particles with clean compressed air, and pay attention to cleaning sand particles in holes, grooves and gaps. The surface of the coating after sanding continues to be sprayed with the topcoat, and the time interval between sanding and spraying the sealing layer is ≤4 h, and if it is greater than 4 h, the sanding treatment is re-performed. Record the end time of sanding and the start time of topcoat spraying.

[0028] 2.2.5 Spraying topcoat (sealing layer) and curing Place the TW-7 high-temperature resistant coating topcoat in the spray gun hopper, adjust the spraying pressure to 0.1-0.2 MPa, and spray the primer coating surface of the part with a uniform layer of topcoat material with the nozzle distance from the part being 100-200 mm, and the coating thickness is about 3-8 µm, presenting a uniform green color.

[0029] The part should be air-dried at room temperature for 10-30 min, then placed in an oven, and the temperature uniformly raised to 80-100 °C, and kept for 30 min, then removed from the oven and all non-high-temperature resistant protection materials such as paper tape, rubber plugs, pressure-sensitive tape, etc. are removed. Trim the coating surface and all non-sprayed surfaces, and thoroughly clean up any excess material. After trimming, place the trimmed part in the drying oven, and raise the temperature to 350 °C ± 5 °C, and keep for not less than 0.5 h, then open the oven door and air cool. The post-spraying surface condition is shown in Figure 4 .

[0030] 3. Test results and discussion 3.1 Appearance quality inspection Inspection standard: Visually inspect the two pipes coated with green TW-7 coating, and the total area of coating missing is not more than 1.5 cm2, and the number is unlimited. If the standard is exceeded, re-coat or spray TW-7 coating. Visually inspect the brazing and argon arc welding surfaces, and no coating missing is allowed. Use a 10x magnifying lens to inspect the brazing and argon arc welding surfaces of the two pipes covered by the coating, that is, the brazing and argon arc welding positions on the lower half “П”-shaped pipe are not allowed to have cracks. The actual test results meet the above requirements, the coating is green, the surface is uniform, continuous, complete and has strong adhesion, and there is no peeling, blistering or peeling phenomenon. There are no residues on all surfaces of the part caused by the sanding and protection processes.

[0031] 3.2 Adhesion According to GB / T9286 standard, the bonding force of the coating on the steel test piece with a size of 50mmx100mm was checked by grid sticking method. The coating in the middle of the grid did not peel off, and the bonding force reached level 1, meeting the requirement of not more than level 2 in the standard.

[0032] 3.3 Thickness The thickness of the coating on the test piece sprayed at the same time as the part was checked by eddy current thickness gauge, and the test results were all within the range of 40μm to 75μm.

[0033] 3.4 Insulation One probe of the multimeter was placed on the bare metal surface, and the other was placed on the coating. The distance between the two probes was not more than 125mm. If the above requirement could not be met for some reason, the two probes were allowed to be placed on the coating, and the distance between the two probes was not less than 25mm. The data was read and recorded, and then the two probes were moved to other positions for continuous measurement. In the on state, the power indicator light was on. The surface coating of the part was measured to be in an insulating state, and the resistance was infinite.

[0034] 3.5 Hydraulic pressure test According to the design drawings and repair documents, the sealing of the three pipes was checked by a pipe hydraulic pressure tester. The working fluid pressure in the test system was 6.5MPa, maintained for 5min, and the sealing of the pipes and each weld and the main body was checked. The pressure was not allowed to decrease, and the working fluid was not allowed to seep out at the connection parts. If the weld and the main body leaked, the part was scrapped. The three engine parts passed the inspection at one time, and no leakage occurred.

[0035] 4. Summary of verification test According to the test, the process technical documents were determined, and the production verification test of the paint layer repair of the three engine pipes was completed. After the parts were painted, they were uniformly green, and the paint layer was uniform, continuous, smooth and defect-free, with a thickness of (40-75)μm. The coating position, appearance, thickness, conductivity and insulation and other indicators met the requirements of the typical process acceptance provisions of "TW-7 water-based high temperature resistant coating".

[0036] After the three aero-engine pipes passed through the whole process verification test, the detection results of the paint layer surface state, fluorescence inspection and pressure test were equivalent to the quality of the original factory spare parts, meeting the requirements of the relevant process technical documents, and the test conclusion was qualified.

[0037] The TW-7 water-based high-temperature-resistant paint in the application is prepared by dispersing a phosphate aqueous solution as a resin with pigments, fillers and additives. The matching of the cured coating film with the metal substrate is good, and the coating film has outstanding properties such as high-temperature resistance, synthetic seawater spray resistance, heat resistance (450±5 DEG C) / synthetic seawater spray resistance, synthetic seawater spray resistance / heat resistance (450±5 DEG C) / high humidity resistance, etc. The coating film is used for high-temperature corrosion protection of important components such as blades, discs and spacers of high-pressure compressors and superchargers of engines. Commercially available products such as those of Zhonghao Beifang Coating Industry Research and Design Institute Co., Ltd. can be used.

[0038] The beneficial effects brought by the scheme of the application The conduit is an important part of an engine. The coating repair method has stable effect when implemented on site, meets the conduit repair requirements, and has remarkable application effect. The work quality and efficiency are obviously improved, and the production cost is reduced. The repair method is improved, the work quality and efficiency are improved, and a good foundation is laid for subsequent repair work.

[0039] The method is very practical, and the conduits of various types of aero-engines with TW-7 coating can be designed for reference. The method can be used not only in the field of aero-engines, but also in various industries and can be widely applied.

Claims

1. A method for repairing the TW-7 coating on an aircraft engine duct, characterized in that... The specific steps of the repair process are as follows: (1) Material preparation; Prepare TW-7 coating, performance test specimens and auxiliary supplies, and test pieces with only unqualified coating appearance quality; (2). Experimental work; (2.1). Process preparation; Compile the overhaul process card. The main process flow is:

5. Labeling → 10. Fault inspection → 15. Fault repair → 20. Fluorescent inspection → 25. Spraying → 30J hydraulic test → 35. Cleaning → 40J final inspection. The TW-7 spraying process specification was developed, which clarified the coating location and acceptance technical requirements of the parts; the main repair process is as follows: protect the non-sprayed surface → remove the coating layer → spray primer → cure → light sandblasting → spray sealing layer → inspection. (2.2). Spray painting process test; (2.2.1) Design protective tooling; The protective fixture includes a pair of nut connectors, a clamp, and tape. The pair of nut connectors rotatably fixes the movable nut to the top of the conduit. The clamp fixes the ball head. The tape wraps around and covers the non-coated surface. (2.2.2). Remove coating; The original coating was removed using a sandblasting method; (2.2.3). Spraying and curing TW-7 primer; (2.2.4). Lightly blow sand; (2.2.5) Spraying topcoat (sealing layer) and curing; (3). Experimental results and discussion; (3.1) Appearance quality inspection; (3.2). Bonding strength test; (3.3) Thickness inspection; (3.4) Insulation testing; (3.5). Hydraulic testing.

2. The method for repairing the TW-7 coating on aero-engine ducts according to claim 1, characterized in that: In step (2.2.1), the protective tooling material is TC4 titanium alloy, which has certain high temperature resistance and relatively soft hardness.

3. The method for repairing the TW-7 coating on aero-engine ducts according to claim 1, characterized in that... The specific steps for removing the original coating using the sandblasting method are as follows: According to the typical process "TW-7 Water-based High-Temperature Resistant Coating", the coating removal process parameters are as follows: use 120-220 mesh alumina sand to sand the coating surface, with a pressure of 0.2-0.55 MPa and a nozzle distance of 100-200 mm to thoroughly remove the coating from the part surface. Then, use waterless and oil-free compressed air to blow away the residual sand particles and dust. Strictly control the time interval between sanding and spraying the undercoat to not exceed 6 hours. After sanding is completed, record the sanding end time and the painting start time.

4. The method for repairing the TW-7 coating on aero-engine ducts according to claim 1, characterized in that... Step (2.2.3). The specific method for spraying and curing the TW-7 primer is as follows: Strictly control the temperature in the spray painting room to 15–30℃ and the relative humidity to 35–60%; Using a SATA or similar spray gun, control the spraying distance to 100-200mm, the spraying pressure to 0.2-0.3MPa, and the spraying angle perpendicular to the part surface; first apply a thin and uniform layer, air dry to a matte gray, then apply a second layer, which is light green when wet, and air dry to gray, thus obtaining a coating of 38-41µm. When further coating is required, repeat the above operation; to obtain a coating of 40µm to 75µm, it is usually necessary to apply 3 to 4 coats; after the primer is applied, first cure at 190±5℃ for at least 1 hour, then remove the high-temperature protective tape on the surface of the part, and continue heating to 350±5℃ and keep at that temperature for 1 hour to allow the paint layer to cure completely. At this time, the paint layer is non-conductive.

5. The method for repairing the TW-7 coating on aero-engine ducts according to claim 1, characterized in that... The specific method for lightly blowing sand in step (2.2.4) is as follows: To ensure the primer is conductive and to increase the adhesion between the primer and the sealing layer, sandblasting is required before spraying the sealing layer. The sandblasting pressure should be controlled between 0.1 and 0.2 MPa, and other parameters should be performed according to step 2.2.

2. The coated area should be sandblasted until the coating is matte gray and the conductivity is satisfactory, i.e., the resistance value does not exceed 15Ω / 125mm. After sandblasting, the surface of the coating should be sprayed with the topcoat. The time interval between sandblasting and spraying the sealing layer should be ≤4 hours. If it is greater than 4 hours, the sandblasting process should be repeated. The sandblasting end time and the topcoat spraying start time should be recorded.

6. The method for repairing the TW-7 coating on aero-engine ducts according to claim 1, characterized in that... The specific method for step (2.2.5) of spraying and curing the topcoat sealing layer is as follows: Place the TW-7 high-temperature resistant coating topcoat into the spray gun hopper, adjust the spraying pressure to 0.1MPa~0.2MPa, and keep the nozzle 100mm~200mm away from the part. Spray a layer of topcoat paint evenly onto the surface of the primer coating of the part. The coating thickness is about 3µm~8µm and it is a uniform green color. The parts should be air-dried at room temperature for 10 to 30 minutes, then placed in an oven and the temperature should be raised evenly to 80℃ to 100℃ and held for 30 minutes. Then remove them and remove all heat-sensitive protective materials. After the repair is completed, place the repaired parts in a drying oven and raise the temperature to 350℃±5℃. Hold for at least 0.5 hours, then open the oven door and air-cool.

7. The method for repairing the TW-7 coating on an aero-engine duct according to claim 1, characterized in that... The specific method for the appearance quality inspection in step (3.1) is as follows: The standard for conduit inspection requires: visually inspect two conduits with green TW-7 coating. The total area of ​​coating loss is allowed to be no more than 1.5 cm2, and there is no limit to the number of defects. If the loss exceeds the standard, the TW-7 coating must be reapplied or sprayed. Visual inspection of the brazed and argon arc weld surfaces must show no missing coating. Using a 10x magnifying glass, inspect the brazed and argon arc weld surfaces on both pipes covered by the coating; specifically, ensure no cracks are present at the brazed and argon arc weld locations on the lower half of the "П"-shaped pipe. Actual test results must meet these requirements: the coating is green, uniform, continuous, complete, and has strong adhesion, with no peeling, blistering, or flaking. All surfaces of the parts must be free of residues caused by sandblasting, protective processes, or other defects.

8. The method for repairing the TW-7 coating on an aero-engine duct according to claim 1, characterized in that... Step (3.2) The bonding strength testing method is as follows: According to GB / T9286 standard, the bonding strength was checked by cross-cut adhesion method on a steel test piece with a specification of 50mm×100mm. The coating in the middle of the cross-cut did not peel off, and the bonding strength reached level 1, which meets the requirement of level 2 or above specified in the standard.

9. The method for repairing the TW-7 coating on an aero-engine duct according to claim 1, characterized in that... The thickness detection method in step (3.3) is as follows: The thickness was checked on the test piece that was sprayed at the same time as the part using an eddy current thickness gauge, and the test results were all within the range of 40µm to 75µm.

10. The method for repairing the TW-7 coating on an aero-engine duct according to claim 1, characterized in that... The insulation testing method in step (3.4) is as follows: Place one of the two probes of the multimeter on the bare metal surface and the other on the coating, with the distance between the two probes not exceeding 125mm. If the above requirement cannot be met for some reason, it is permissible to place both probes on the coating, with the distance between the probes not less than 25mm, read and record the data, and then move the two probes to other positions to continue the measurement. The hydraulic test method for step (3.5) is as follows: According to the design drawings and repair documents, use a conduit hydraulic tester to check the sealing of the conduit; test the working fluid pressure in the system at 6.5MPa, maintain it for 5 minutes, and check the sealing of the conduit, each weld and the main body. Pressure drop and working fluid leakage at the connection points are not allowed. If there is leakage at the weld and the main body, the part shall be scrapped.

Images