A method for repairing localized damage to the surface of a connecting rod in an aircraft cabin door opening mechanism.

Abstract

This invention relates to the field of aircraft door opening mechanism repair technology, specifically a method for repairing localized damage to the surface of a connecting rod in an aircraft door opening mechanism. The specific steps are as follows: removing the original chrome plating layer and the damaged areas from the connecting rod surface; magnetizing the connecting rod using the center conductor method, and using an external magnetic field method to detect whether the localized damage on the connecting rod has been completely removed; preparing a 316L stainless steel coating on the damaged areas of the connecting rod using supersonic flame spraying; and preparing a tungsten carbide cobalt-chromium coating on the connecting rod using supersonic flame spraying. This invention eliminates the heat-affected zone, eliminates the need for overall trimming of the outer surface of the part before repair, minimizes the impact on the mechanical properties of the part, and solves the problems of large heat-affected zones and easy weld penetration associated with traditional welding and laser cladding repair methods. It repairs localized damage to the connecting rod of the door opening mechanism while maintaining the original mechanical properties of the part to the greatest extent possible.

Description

Technical Field

[0001] This invention relates to the field of aircraft door opening mechanism repair technology, specifically a method for repairing localized damage to the surface of the connecting rod of an aircraft door opening mechanism. Background Technology

[0002] The aircraft door opening mechanism is an important component of an aircraft, mainly composed of an outer cylinder, connector, cap, connecting rod, plunger, and spring. When the door lock is released, the working spring in this mechanism extends and opens the door, while the rotational inertial energy of the door opening is absorbed by a buffer spring. Both the working spring and the buffer spring are installed on the outer surface of the connecting rod with specific assembly clearances, such as... Figure 1 As shown, although the connecting rod surface is electroplated with chromium and coated with grease to reduce some wear, after prolonged use, localized areas will still experience excessive wear and scratches, causing spring wobbling and malfunctioning of the door opening mechanism, affecting flight safety. The wall thickness of this connecting rod is generally between 1.8 and 2.5 mm. To facilitate repair of damaged areas, the edges of the damaged areas are ground smooth, such as... Figure 2 As shown, this forms a groove with a depth of approximately (0.1–0.3) mm, as... Figure 3 As shown.

[0003] Traditional welding or laser cladding repair methods produce excessively large heat-affected zones, posing a risk of burn-through, and are therefore unsuitable for repairing this part. Conventional supersonic flame spraying of tungsten carbide coatings requires overall trimming of the part's outer surface before repair to ensure the part's dimensional stability after coating. However, this method reduces the part's rigidity, making it difficult to guarantee its mechanical properties and impacting flight safety. Summary of the Invention

[0004] To address the technical problem of localized damage to connecting rods in existing aircraft door opening mechanisms, which is difficult to repair using traditional methods, this invention proposes a method for repairing localized damage to the surface of connecting rods in aircraft door opening mechanisms. By using a supersonic flame spraying method to apply a composite coating, a 316L stainless steel coating is first prepared at the locally damaged area to repair the part's dimensions. Then, a tungsten carbide cobalt-chromium coating is sprayed to replace the original electroplated chromium layer, thereby better preventing wear on the working surface of the connecting rod.

[0005] The technical problem to be solved by this invention is achieved by the following technical solution:

[0006] A method for repairing localized damage to the surface of a connecting rod in an aircraft cabin door opening mechanism, comprising the following specific steps:

[0007] Step (1) Remove the original chrome plating layer and any damaged areas from the surface of the connecting rod;

[0008] Step (2) Magnetize the connecting rod using the central conductor method, and use the external magnetic field method to check whether the local damage on the connecting rod has been completely removed;

[0009] Step (3) Clean the connecting rod after flaw detection with gasoline;

[0010] Step (iv) Use supersonic flame spraying to prepare a 316L stainless steel coating on the locally damaged areas of the connecting rod;

[0011] The specific process is as follows:

[0012] (a) Thoroughly clean the outer surface of the connecting rod with acetone solution;

[0013] (b) Install clamping fixture No. 1 and clamping fixture No. 2 at both ends of the connecting rod, and then install it on the turntable, so that the local damaged part on the connecting rod is facing the supersonic flame spray gun.

[0014] (c) Use manual sandblasting to roughen the locally damaged areas of the connecting rod;

[0015] (d) Place a shielding fixture between the connecting rod and the supersonic flame spray gun;

[0016] (e) Set the turntable according to the size of the local damage on the connecting rod and rotate it alternately in the forward and reverse directions within a certain angle range at a fixed speed. The supersonic flame spray gun moves back and forth at a fixed speed to spray.

[0017] Step (5) involves grinding and post-processing the prepared 316L stainless steel coating;

[0018] Step (vi) Use supersonic flame spraying to spray the connecting rod to prepare a tungsten carbide cobalt chromium coating;

[0019] The specific process is as follows:

[0020] (A) Thoroughly clean the outer surface of the connecting rod with acetone solution;

[0021] (B) Use pure copper pins to seal the grooves on the surface of the connecting rod that do not require spraying. Install clamping fixture No. 1 and clamping fixture No. 2 at both ends of the connecting rod, and then install it on the turntable.

[0022] (C) The outer surface of the connecting rod is roughened by segmented sandblasting;

[0023] (D) A segmented spraying method is used to prepare a tungsten carbide cobalt chromium coating on the outer surface of the connecting rod. During the spraying process, a masking fixture is placed between the area that does not need to be sprayed and the supersonic flame spray gun.

[0024] Step (vii) involves grinding and post-processing the prepared tungsten carbide cobalt chromium coating;

[0025] Step (8) Use fluorescent flaw detection to check the quality of the tungsten carbide cobalt chromium coating on the connecting rod, and use magnetic particle flaw detection to check the quality of the remaining areas of the connecting rod.

[0026] Step (ix) Prepare furnace-fed test pieces of 316L stainless steel-tungsten carbide cobalt chromium composite coating and 316L stainless steel-tungsten carbide cobalt chromium composite coating using the same process parameters, and evaluate the performance of the test pieces in terms of metallography, bonding strength, bending performance and wear resistance.

[0027] Step (10) Assemble the repaired connecting rod onto the aircraft door opening mechanism and conduct a ground test to check the repair quality.

[0028] Preferably, in step (i), an electric grinding head is used to grind the locally damaged parts of the connecting rod into a U-shaped bevel, and the edges of the locally damaged parts are rounded.

[0029] Preferably, the process parameters for manual sandblasting in step (iv)(c) are: sandblasting pressure of 0.2MPa to 0.4MPa; and the use of 60-80 mesh corundum sand.

[0030] Preferably, in step (iv)(e), the linear velocity of the supersonic flame spray gun is 800 mm / s to 1200 mm / s; the gun movement step is 4 mm to 6 mm; the spraying process parameters are: oxygen flow rate 1800 scfh to 1900 scfh; kerosene flow rate 6.5 gph to 7.0 gph; powder feed rate 40 g / min to 50 g / min; and spraying distance 340 mm to 360 mm.

[0031] Preferably, in step (iv)(e) and step (vi)(D), an infrared thermometer is used to monitor the surface temperature of the connecting rod in real time, and the temperature is required to be no higher than 177°C.

[0032] Preferably, the grinding and post-processing of the 316L stainless steel coating in step (v) is as follows: using an external cylindrical grinding machine to remove excess 316L stainless steel coating and restore the original external dimensions of the part; heat treatment at 190℃±10℃ to remove grinding stress.

[0033] Preferably, in step (vi) (C), the linear velocity of the supersonic flame spray gun is 200mm / s to 400mm / s; the gun movement step is 4mm to 6mm; and the process parameters of the segmented sandblasting method are: sandblasting abrasive particles of 60 mesh to 80 mesh; sandblasting pressure of 0.2MPa to 0.4MPa; and sandblasting distance of 300mm to 400mm.

[0034] Preferably, in step (vi) (D), the linear velocity of the supersonic flame spray gun is 800 mm / s to 1200 mm / s; the spray gun movement step is 4 mm to 6 mm; the process parameters for segmented spraying are: oxygen flow rate 1900 scfh to 2000 scfh; kerosene flow rate 6.3 gph to 6.7 gph; powder feeding rate 60 g / min to 75 g / min; and spraying distance 340 mm to 360 mm.

[0035] Preferably, the grinding and post-processing of the tungsten carbide cobalt chromium coating in step (vii) is as follows: using an external cylindrical grinder and a diamond grinding wheel, the outer surface of the tungsten carbide cobalt chromium coating is ground according to the final size requirements of the connecting rod. After grinding, the surface roughness of the tungsten carbide cobalt chromium coating should be lower than Ra0.8μm; heat treatment is performed at 190℃±10℃ to remove grinding stress.

[0036] Preferably, the ground test process in step (x) is as follows: a load test is performed on the connecting rod with the maximum stroke tension 100 times, the hatch opening mechanism is disassembled, and the coating surface quality is checked by visual inspection and fluorescent flaw detection methods.

[0037] The beneficial effects of this invention are:

[0038] Compared with existing technologies, this invention has no heat-affected zone, eliminates the need for overall reshaping of the outer surface of the part before repair, minimizes the impact on the mechanical properties of the part, and solves the problems of large heat-affected zones and easy weld penetration of parts in traditional welding and laser cladding repair methods. While maintaining the original mechanical properties of the part to the greatest extent, it repairs the local damage to the connecting rod of the hatch opening mechanism, solving the problem of batch wear and scrapping of the connecting rod of the hatch opening mechanism and high replacement costs. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0040] Figure 1 This is a front view structural diagram of the connecting rod;

[0041] Figure 2 A schematic diagram showing the removal of damaged parts from the connecting rod;

[0042] Figure 3 Remove the screenshot of the damaged area of ​​the connecting rod;

[0043] Figure 4 This is a flowchart illustrating the repair process of the present invention;

[0044] Figure 5 This is a schematic diagram showing the partial spray coating masking of the connecting rod of the present invention;

[0045] Figure 6 This is a diagram showing the repair effect after partially spraying a 316L stainless steel coating onto the connecting rod of the present invention.

[0046] Figure 7 This is a schematic diagram of the segmented spraying of the connecting rod of the present invention (arrows point to the spraying positions);

[0047] Figure 8 This is a metallographic schematic diagram of the 316L stainless steel-tungsten carbide cobalt chromium composite coating on the connecting rod of the present invention;

[0048] Figure 9 This is a metallographic schematic diagram of the tungsten carbide cobalt chromium coating on the connecting rod of the present invention;

[0049] Figure 10 This is a schematic diagram illustrating the bending performance of the connecting rod of the present invention, made of 316L stainless steel with a tungsten carbide cobalt chromium composite coating.

[0050] Figure 11 This is a schematic diagram illustrating the bending performance of the tungsten carbide cobalt chromium coating on the connecting rod of the present invention.

[0051] Figure 12 This is a schematic diagram illustrating the wear resistance of the 316L stainless steel-tungsten carbide cobalt chromium composite coating on the connecting rod of the present invention.

[0052] In the diagram: 1. Buffer spring mounting surface; 2. Working spring mounting surface; 3. No. 1 clamping fixture; 4. Connecting rod; 5. No. 2 clamping fixture; 6. Shielding fixture. Detailed Implementation

[0053] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0054] like Figure 4 As shown, a method for repairing localized damage to the surface of a connecting rod in an aircraft cabin door opening mechanism includes the following specific steps:

[0055] Step (1) Coating and Damage Removal:

[0056] Specifically, before repair, the original chrome plating on the surface of connecting rod 4 needs to be removed, and the damaged area needs to be repaired with an electric grinder to make a U-shaped bevel, ensuring that the edge of the damaged area is smoothly transitioned.

[0057] Step (II) Magnetic particle inspection:

[0058] Specifically, the connecting rod 4 was magnetized using the center conductor method, and then an external magnetic field method was used to confirm that the surface damage of the connecting rod 4 had been completely removed.

[0059] Step (3) Cleaning:

[0060] Specifically, after cleaning the connecting rod 4 with gasoline for flaw detection, all grease, oil stains, and flaw detection marks inside and outside the connecting rod 4 must be completely removed to avoid affecting the coating adhesion performance.

[0061] Step (IV) Preparation of 316L stainless steel coating by localized supersonic flame spraying:

[0062] Specifically, step a: thoroughly clean the outer surface of connecting rod 4 with acetone solution.

[0063] Step b: Install clamping fixture 3 and clamping fixture 5 at both ends of the connecting rod 4, then install them on the turntable and position the damaged part facing the supersonic flame spray gun.

[0064] Step c: Use manual sandblasting at a pressure of 0.2MPa to 0.4MPa and use 60-80 mesh corundum sand to roughen the locally damaged areas of the connecting rod 4. The surface should be rough and uniform, without metallic luster or dark spots.

[0065] Step d: Place the masking fixture 6 between the connecting rod 4 and the supersonic flame spray gun, such as... Figure 5 As shown, this prevents unintended deposition of the coating.

[0066] Step e: Set the turntable program according to the size of the damaged area, so that the turntable rotates at a fixed speed, alternating between forward and reverse rotation within a certain angle range. The spray gun moves back and forth at a fixed speed to ensure that the coating is deposited only on the damaged area and surrounding area, achieving the repair effect as shown. Figure 6 As shown.

[0067] The supersonic flame spraying gun has a linear speed of 800 mm / s to 1200 mm / s and a step size of 4 mm to 6 mm. Spraying parameters include an oxygen flow rate of 1800 scfh to 1900 scfh, a kerosene flow rate of 6.5 gph to 7.0 gph, a powder feed rate of 40 g / min to 50 g / min, and a spraying distance of 340 mm to 360 mm. During the process, an infrared thermometer is used to monitor the surface temperature of the parts in real time, ensuring it does not exceed 177℃.

[0068] Step (5) Coating Grinding and Post-treatment:

[0069] Specifically, an external cylindrical grinding machine was used to remove excess 316L stainless steel coating and restore the original dimensions of connecting rod 4. After grinding, it was heat-treated at 190±10℃ to relieve grinding stress.

[0070] Step (VI) Preparation of tungsten carbide cobalt-chromium coating by supersonic flame spraying:

[0071] Specifically, step A: Thoroughly clean the outer surface of connecting rod 4 with acetone solution.

[0072] Step B: Use pure copper pins with an interference fit to seal the grooves on the surface of the connecting rod that do not require painting. Install clamping fixtures at both ends of the part, and then install it onto the turntable.

[0073] Step C: Due to the different diameters of the working surfaces, a segmented sandblasting and spraying method is used to prepare the tungsten carbide cobalt chromium coating sequentially. For areas where spraying is not required, a masking fixture 6 is placed between the connecting rod 4 and the supersonic flame spray gun. Figure 7 As shown.

[0074] During sandblasting, the linear velocity of the supersonic flame spray gun is 200mm / s to 400mm / s; the gun movement step is 4mm to 6mm. Sandblasting parameters are: abrasive particle size of 60-80 mesh, sandblasting pressure of 0.2MPa to 0.4MPa, and sandblasting distance of 300mm to 400mm. During coating, the linear velocity of the supersonic flame spray gun is 800mm / s to 1200mm / s; the gun movement step is 4mm to 6mm. Coating parameters are: oxygen flow rate of 1900 scfh to 2000 scfh, kerosene flow rate of 6.3gph to 6.7gph, powder feed rate of 60g / min to 75g / min, and coating distance of 340mm to 360mm. During the process, an infrared thermometer is used to monitor the surface temperature of the parts in real time, and it should not exceed 177℃.

[0075] (7) Coating grinding and post-treatment:

[0076] Specifically, using an external cylindrical grinder and diamond grinding wheels, the outer surface of the coating is ground according to the final dimensional requirements of the part. After grinding, the surface roughness of the coating should be lower than Ra0.8μm. Subsequently, heat treatment is performed at 190±10℃ to remove grinding stress.

[0077] (8) Component flaw detection:

[0078] Specifically, fluorescent testing is used to apply ZY22 penetrant to the coating surface and inspect the coating quality. Magnetic particle testing is used to inspect the quality of uncoated areas of the parts.

[0079] (9) Coating performance evaluation:

[0080] Specifically, 316L stainless steel-tungsten carbide cobalt chromium composite coating and tungsten carbide cobalt chromium coating furnace test pieces were prepared using the same process parameters, and their metallographic properties, bonding strength, bending properties and wear resistance were evaluated.

[0081] Performance tests show that, regardless of the location of the 316L stainless steel-tungsten carbide cobalt chromium composite coating, or the specific location of the tungsten carbide cobalt chromium coating, the porosity of the 316L stainless steel coating is less than 1%. Figure 8 As shown; the porosity of the tungsten carbide cobalt chromium coating is less than 0.5%, such as... Figure 9As shown, the coating has high density; the bonding strength of the 316L stainless steel-tungsten carbide cobalt chromium composite coating is higher than 70 MPa, and the bonding strength of the tungsten carbide cobalt chromium coating is higher than 79 MPa. Both exhibit better bonding performance than the original electroplated chromium layer. When the bent specimen was bent 90 degrees around a Ф12.7 mm cylinder and observed under a stereomicroscope, no peeling was observed on the surfaces of the 316L stainless steel-tungsten carbide cobalt chromium composite coating and the tungsten carbide cobalt chromium coating, and there was no separation between the coating and the substrate. The bonding performance between the coating and the substrate is excellent. Figure 10 , Figure 11 As shown. In the wear resistance test, the coefficient of friction of the composite coating was comparable to that of the original chromium plating layer, while the weight loss was significantly lower than that of the original chromium plating layer, such as... Figure 12 As shown, it has better wear resistance and can effectively prevent secondary wear of the connecting rod of the hatch opening mechanism.

[0082] (10) Component ground testing:

[0083] Specifically, the repaired connecting rod is assembled into the hatch opening mechanism, and a load test is conducted according to the ground test requirements for the hatch opening mechanism, stretching the connecting rod 100 times at maximum stroke. Then, the hatch opening mechanism is disassembled for visual inspection and fluorescent flaw detection of the coating surface quality.

[0084] Compared with existing technologies, this invention has no heat-affected zone, eliminates the need for overall reshaping of the outer surface of the part before repair, minimizes the impact on the mechanical properties of the part, and solves the problems of large heat-affected zones and easy weld penetration of parts in traditional welding and laser cladding repair methods. While maintaining the original mechanical properties of the part to the greatest extent, it repairs the local damage to the connecting rod of the hatch opening mechanism, solving the problem of batch wear and scrapping of the connecting rod of the hatch opening mechanism and high replacement costs.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for repairing localized damage to the surface of a connecting rod in an aircraft cabin door opening mechanism, characterized in that: The specific steps are as follows: Step (1) Remove the original chrome plating layer and any damaged areas from the surface of the connecting rod (4); Step (2) Magnetize the connecting rod (4) using the central conductor method, and use the external magnetic field method to detect whether the local damage on the connecting rod (4) has been completely removed; Step (3) Clean the connecting rod (4) after flaw detection with gasoline; Step (iv) Use supersonic flame spraying to prepare a 316L stainless steel coating on the locally damaged parts of the connecting rod (4); The specific process is as follows: (a) Thoroughly clean the outer surface of the connecting rod (4) with acetone solution; (b) Install clamping fixture (3) and clamping fixture (5) at both ends of the connecting rod (4), and then install them on the turntable, so that the local damaged part on the connecting rod (4) faces the supersonic flame spray gun. (c) The damaged parts of the connecting rod (4) are roughened by manual sandblasting; The process parameters for manual sandblasting in step (iv)(c) are: sandblasting pressure of 0.2MPa to 0.4MPa; and the use of 60-80 mesh corundum sand. (d) Place a shielding fixture (6) between the connecting rod (4) and the supersonic flame spray gun; (e) Set the turntable according to the size of the local damage on the connecting rod (4) and rotate it alternately in the forward and reverse directions within a certain angle range at a fixed speed. The supersonic flame spray gun moves back and forth at a fixed speed to spray. In step (iv)(e), the linear velocity of the supersonic flame spray gun is 800 mm / s to 1200 mm / s; the step size of the supersonic flame spray gun is 4 mm to 6 mm; the spraying process parameters are: oxygen flow rate 1800 scfh to 1900 scfh; kerosene flow rate 6.5 gph to 7.0 gph; powder feed rate 40 g / min to 50 g / min; spraying distance 340 mm to 360 mm. Step (5) involves grinding and post-processing the prepared 316L stainless steel coating; Step (vi) Use supersonic flame spraying to spray the connecting rod to prepare a tungsten carbide cobalt chromium coating; The specific process is as follows: (A) Thoroughly clean the outer surface of the connecting rod (4) with acetone solution; (B) Use pure copper pins to seal the grooves on the surface of the connecting rod (4) that do not need to be sprayed. Install clamping fixture (3) and clamping fixture (5) at both ends of the connecting rod (4) and then install it on the turntable. (C) The outer surface of the connecting rod (4) is roughened by segmented sandblasting; (D) The tungsten carbide cobalt chromium coating is prepared on the outer surface of the connecting rod (4) by segmented spraying. During the spraying process, a shielding fixture (6) is placed between the position where spraying is not required and the supersonic flame spraying gun. Step (vii) involves grinding and post-processing the prepared tungsten carbide cobalt chromium coating; Step (8) Use fluorescent flaw detection to check the quality of the tungsten carbide cobalt chromium coating on the connecting rod, and use magnetic particle flaw detection to check the quality of the remaining areas of the connecting rod. Step (ix) Prepare furnace-fed test pieces of 316L stainless steel-tungsten carbide cobalt chromium composite coating and 316L stainless steel-tungsten carbide cobalt chromium composite coating using the same process parameters, and evaluate the performance of the test pieces in terms of metallography, bonding strength, bending performance and wear resistance. Step (10) Assemble the repaired connecting rod (4) onto the aircraft door opening mechanism and conduct a ground test to check the repair quality; In step (iv)(e) and step (vi)(D), an infrared thermometer is used to monitor the surface temperature of the connecting rod (4) in real time, and it is required to be no higher than 177℃; in step (vi)(C), the moving linear speed of the supersonic flame spray gun is 200mm / s~400mm / s; the moving step of the supersonic flame spray gun is 4mm~6mm; the process parameters of the segmented sandblasting method are: sandblasting abrasive particles are 60 mesh~80 mesh; sandblasting pressure is 0.2MPa~0.4MPa; sandblasting distance is 300mm~400mm.

2. The method for repairing localized damage to the surface of the connecting rod of an aircraft cabin door opening mechanism according to claim 1, characterized in that: In step (1), an electric grinding head is used to grind the damaged parts of the connecting rod (4) into a U-shaped bevel, and the edges of the damaged parts are rounded.

3. The method for repairing localized damage to the surface of the connecting rod of an aircraft cabin door opening mechanism according to claim 1, characterized in that: The grinding and post-processing of the 316L stainless steel coating in step (5) are as follows: use an external cylindrical grinder to remove excess 316L stainless steel coating and restore the original shape and size of the part; heat treat at 190℃±10℃ to remove grinding stress.

4. The method for repairing localized damage to the surface of the connecting rod of an aircraft cabin door opening mechanism according to claim 1, characterized in that: In step (VI) (D), the linear velocity of the supersonic flame spray gun is 800 mm / s to 1200 mm / s; the step size of the supersonic flame spray gun is 4 mm to 6 mm; and the process parameters for segmented spraying are: oxygen flow rate 1900 scfh to 2000 scfh; kerosene flow rate 6.3 gph to 6.7 gph; powder feed rate 60 g / min to 75 g / min; and spraying distance 340 mm to 360 mm.

5. The method for repairing localized damage to the surface of the connecting rod of an aircraft cabin door opening mechanism according to claim 1, characterized in that: The grinding and post-processing of the tungsten carbide cobalt chromium coating in step (seven) are as follows: using an external cylindrical grinder and diamond grinding wheel, the outer surface of the tungsten carbide cobalt chromium coating is ground according to the final size requirements of the connecting rod (4). After grinding, the surface roughness of the tungsten carbide cobalt chromium coating should be lower than Ra0.8μm. Heat treatment is carried out at 190℃±10℃ to remove grinding stress.

6. The method for repairing localized damage to the surface of the connecting rod of an aircraft cabin door opening mechanism according to claim 1, characterized in that: The ground test process in step (10) is as follows: the load test is carried out by stretching the connecting rod 100 times with the maximum stroke, the hatch opening mechanism is disassembled, and the surface quality of the coating is checked by visual inspection and fluorescent flaw detection methods.

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