A spraying method for chromium oxide wear-resistant coating on surface of a transmission shaft part

Abstract

The application provides a spraying method for a chromium oxide wear-resistant coating on a surface of a transmission shaft part, and comprises the following steps: the transmission shaft spraying part is designed as a concave structure, and a right side preset chamfer is arranged; a protection tool is installed to protect a non-spraying sandblasting part of the part, and the spraying sandblasting part of the part is exposed from the protection tool; compressed air is used to cool the part from a side rear part; a robot is used to automatically spray a point, a spraying gun moving speed and a part rotating speed are set; the spraying gun is used to preheat the spraying part; a chromium oxide coating is sprayed according to a specified spraying parameter, and a powder appearance is spherical; compressed air is used to cool a part base from a side rear part during the spraying process; meanwhile, the spraying is stopped every 2 cycles, 2 minutes are waited, and then the spraying is continued; an infrared temperature detector is used to detect a part temperature of a spraying part in real time, so that the part temperature in the spraying process is ensured to be less than 150 DEG C; the clamp is disassembled, the part is cleaned, and the coating is ground by using a diamond grinding wheel.

Description

Technical Field

[0001] This application belongs to the field of thermal spraying technology, and in particular relates to a method for spraying a chromium oxide wear-resistant coating on the surface of transmission shaft parts. Background Technology

[0002] Drive shafts in aerospace transmission systems are crucial for power transmission, bearing enormous torque and complex alternating loads. When rotating at high speeds of up to 6000 r / min, they experience intense friction with mating cup seals. To improve the power, reliability, sealing performance, and lifespan of transmission systems, high-hardness chromium oxide coatings are receiving increasing attention in the design and development of moving parts in aerospace transmission systems.

[0003] Currently, the surfaces of moving parts in existing aircraft transmission systems are generally coated with chrome or tungsten carbide. However, these processes have led to problems in practical applications, such as damage or oil leakage of the matching diaphragm cups, and insufficient service life. To avoid these drawbacks, thermal spraying technology for preparing chromium oxide coatings has been developed in recent years. Summary of the Invention

[0004] The objective of this invention is to provide a process for plasma-spraying a high-purity chromium oxide coating onto the surface of a drive shaft, which can control the porosity of the chromium oxide coating to below 5%, achieve a uniform microstructure free of unmelted particles, and a coating hardness of HV. 0.2 1100~1600. A chromium oxide coating with a surface roughness Ra≤0.2μm and a relative bearing ratio Rmr (1.2um) of ≥90% can be obtained after grinding with a diamond wheel. Through a reasonable spraying structure design, a coating flush with the substrate can be obtained, better guiding the assembly of the diaphragm seal mating parts without damage. Effective sealing is achieved between the diaphragm seal mating parts and the drive shaft components under high-speed rotation.

[0005] This application provides a method for spraying a chromium oxide wear-resistant coating on the surface of transmission shaft parts, the method comprising: The spraying area of ​​the drive shaft is designed with a concave structure and a pre-set chamfer on the right side; Install protective fixtures to protect the non-sprayed / sandblasted parts of the parts, while the sprayed / sandblasted parts of the parts are exposed to the protective fixtures. Compressed air is used to cool the parts from the side and rear. The robot's automatic spraying points, spray gun movement speed, and part rotation speed are set. Preheat the area to be sprayed using a spray gun; The chromium oxide coating is sprayed according to the specified spraying parameters, and the powder morphology is spherical. During the spraying process, compressed air is used to cool the part substrate from the side and rear. At the same time, after every two spraying cycles, the spraying is stopped, waited for 2 minutes, and then resumed. An infrared thermometer is used to monitor the part temperature in real time during the spraying process to ensure that the part temperature does not exceed 150℃. Disassemble the fixture and clean the parts; The coating is ground using a diamond grinding wheel.

[0006] Preferably, the preset chamfer is 20° to 30°.

[0007] Preferably, the structure of the sprayed part of the drive shaft is designed as a concave structure, and after a pre-set chamfer on the right side, it includes: Use acetone organic solvent to clean the surface of the part to be sprayed and the adjacent surfaces until there is no visible oil or dirt, and then air dry.

[0008] Preferably, the installation protective fixture protects the non-sprayed / sandblasted parts of the part, and after the sprayed / sandblasted parts of the part are exposed to the protective fixture, it further includes: The surface of the sprayed / sandblasted area shall be sandblasted. After sandblasting, the sprayed surface of the part shall be a uniform rough surface without metallic luster. The surface roughness requirement for sandblasted surface is Ra≥4μm.

[0009] Preferably, the powder composition is Cr2O3 ≥ 99.5%, TiO2 ≤ 0.1%, Al2O3 ≤ 0.2%, Fe2O3 ≤ 0.4%, and SiO2 ≤ 0.45%.

[0010] Preferably, the preheating temperature is 50℃~120℃.

[0011] Preferably, the spraying parameters include: The plasma spraying equipment is: Metco 9M; Nozzle type: 732 or GH; Powder delivery rate: 25%; Argon pressure: 75Psi±5Psi; Argon flow rate: 80 SCFH ± 5 SCFH; Hydrogen pressure: 50±5 Psi; Hydrogen flow rate: 22 SCFH~29 SCFH; Powder delivery air pressure: 3.5 bar ± 0.2 bar; Powder delivery airflow rate: 8±0.5; Current: 630A±5A; Voltage: 75V±2V; Spraying distance: 65 mm ± 10 mm, spraying angle: 80°~90°, coating thickness: 0.25 mm~0.35 mm.

[0012] Preferably, the setting of the robot's automatic spraying points, spray gun movement speed, and part rotation speed includes: Set the automatic spraying points for the robot, the spray gun movement speed to 10mm / s, and the part rotation speed to 130r / min~150r / min.

[0013] The beneficial technical effects of this application are as follows: The advantages of this invention are its rationally designed spraying structure. Under the protection of effective spraying protective fixtures, through plasma spraying technology, reasonable spraying parameters, and process control, the substrate temperature can be kept below 150°C, the coating porosity below 5%, the microstructure uniform and free of unmelted particles, and the coating hardness HV. 0.2 1100~1600. Using diamond grinding wheels for rough and fine grinding, a chromium oxide coating with a surface roughness Ra≤0.2μm and a surface relative support ratio Rmr(1.2um) of ≥90% can be obtained. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structural design of the part to be coated in this invention; Figure 2 This is a schematic diagram of the sandblasting and spraying protective fixture provided by the present invention; Figure 3 This is a schematic diagram of the morphology of chromium oxide powder; Figure 4 This is a schematic diagram of the metallographic structure of a chromium oxide sample. Figure 5 This is a schematic diagram of the state of a chromium oxide sample after grinding. Figure 6 This is a schematic diagram of the clutch inner shaft after spraying. Figure 7 This is a schematic diagram of the clutch inner shaft after grinding; Among them, 1 is a hexagonal head bolt, 2 is a base plate, 3 is a protective sleeve, 4 is a high-strength hose clamp, 5 is a high-strength hose clamp, 6 is a protective cover, 7 is a washer, and 8 is a cap nut. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0018] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0020] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] The following is a description of the embodiments and appendices. Figure 1 - Appendix Figure 7 The present invention will be described in further detail, but the embodiments of the present invention are not limited thereto.

[0022] This invention provides a process design method for plasma-spraying a chromium oxide wear-resistant coating onto a drive shaft, comprising: Step 1: Structural design of the area to be coated on the drive shaft (see...) Figure 1 ); Step 2: Clean the sprayed surface to remove grease and dirt; Step 3: Install sandblasting protective fixtures (see...) Figure 2 Surface sandblasting, the surface roughness Ra ≥ 4μm is required after sandblasting; Step 4: Install the spray protection fixture (same as above) Figure 2 Clamp the parts and cool them with compressed air from the side and rear. Set the robot's automatic spraying points, spray gun movement speed, and part rotation speed; Step 5: Apply the chromium oxide coating according to the specified spraying parameters; Step 6: Disassemble the clamps; Step 7: Grind the coating with a diamond grinding wheel.

[0023] The spraying area is designed with a recessed structure on the substrate, with a chamfer of 20° to 30° on the right side. This angle range ensures a smoother coating transition and prevents gaps from forming between the coating and the substrate when the angle is too large. After processing, the coating is flush with the substrate, which provides some protection for the coating. At the same time, it makes the assembly of matching accessories (such as leather cups) smoother and less likely to damage the leather cups.

[0024] During spraying, first install the base plate 2 on the left side of the part, then connect it to the part with hexagonal head bolts 1, and at the same time install the protective cover 6 and washer 7 and lock them with cap nuts 8. Finally, install the protective sleeve 3 and secure it with strong hose clamps 4 and 5.

[0025] Among them, hexagonal head bolts, washers and cap nuts mainly serve to connect and lock, base plates, protective covers and protective sleeves serve to protect, and strong hose clamps serve to tighten.

[0026] In other embodiments of this application, the technical solutions provided by the present invention include: Step 1: The structure of the part of the drive shaft to be sprayed is designed as a concave structure; Step 2: Clean the surface of the part to be sprayed and the adjacent surfaces with organic solvents such as acetone until there is no visible oil or dirt on the surface, and then air dry it in the air; Step 3: Install the sandblasting protective fixture and sandblast the coating surface. After sandblasting, the coating surface of the part should be a uniform rough surface without metallic luster. The surface roughness requirement for sandblasting is Ra≥4μm. Step 4: Change the spray protection fixture, clamp the part, and cool it from the side and rear with compressed air. Set the robot's automatic spraying points, and the spray gun's moving speed to 10mm / s. The part's rotation speed should be 130r / min~150r / min. Step 5: Preheat the area to be sprayed to 50℃~120℃. Preheating can be done directly using the spray gun. The chromium oxide coating should have a spherical powder morphology. Figure 3 As shown, the powder composition is Cr2O3 ≥ 99.5%, TiO2 ≤ 0.1%, Al2O3 ≤ 0.2%, Fe2O3 ≤ 0.4%, and SiO2 ≤ 0.45%; the plasma spraying equipment is a Metco 9M; the nozzle model is 732 or GH; the powder feed rate is 25%; the argon pressure is 75Psi ± 5Psi; the argon flow rate is 80SCFH ± 5SCFH; the hydrogen pressure is 50 ± 5 Psi; the hydrogen flow rate is 22SCFH~29SCFH; the powder feed gas pressure is 3.5bar ± 0.2 bar; the powder feed gas flow rate is 8 ± 0.5; the current is 630A ± 5A; the voltage is 75V ± 2V; the spraying distance is 65 mm ± 10 mm; the spraying angle is 80°~90°; and the coating thickness is 0.25 mm~0.35 mm. During the spraying process, compressed air is used to cool the part substrate from the side and rear. At the same time, after every two spraying cycles, the spraying is stopped, waited for 2 minutes, and then resumed. An infrared thermometer is used to monitor the part temperature in real time during the spraying process to ensure that the part temperature does not exceed 150℃.

[0027] Among them, the powder is spherical, which has better flowability. The powder composition contains Cr2O3 ≥ 99.5%, which is the main component of the coating and its core phase. Its high purity determines the high hardness and excellent wear resistance of the coating. Strictly controlling its content reduces impurities that cause performance degradation. TiO2 ≤ 0.1%, TiO2 is a modifying additive phase. TiO2 and Cr2O3 form a low-melting-point solid solution, which can reduce the difficulty of powder melting, improve the powder melting rate during plasma spraying, reduce unmelted particles in the coating, and refine the coating grains, increasing density. However, excessive TiO2 can easily cause coating sagging and reduced density. Al2O3 ≤ 0.2%, Al2O3 is a modifying additive phase. Al2O3 and Cr2O3 form a composite wear-resistant layer. Al2O3 can improve the overall hardness and resistance to particle erosion and sliding wear of the coating, but too much Al2O3 will increase the brittleness of the coating and reduce its impact resistance; Fe2O3 ≤ 0.4% is a modified additive phase. Fe2O3 acts as a flux phase to encapsulate Cr2O3 particles, promoting their full melting and improving the hardness and density of the coating, but too much Fe2O3 will reduce the hardness and density of the coating; SiO2 ≤ 0.45% is a modified additive phase. SiO2 forms a glassy phase at high temperatures in plasma spraying, filling the pores and microcracks between molten droplets in the coating, which can improve the density and corrosion resistance of the coating, but too much SiO2 and too much glassy phase will cause the coating to soften easily at high temperatures and reduce its wear resistance.

[0028] Step 6: Disassemble the fixture and clean the parts.

[0029] Step 7: Coating grinding.

[0030] This process effectively controls the heating state and flight speed of the powder, thus controlling the porosity, unmelted particles, and hardness of the coating. External cooling during spraying effectively prevents overheating and cracking. The design of the spraying protection fixture better protects non-sprayed areas, preventing coating from affecting part use. Rough and fine grinding with diamond wheels effectively ensures a surface roughness Ra ≤ 0.2 μm and a surface support ratio Rmr (1.2 μm) ≥ 90%. The recessed substrate design ensures the coating is flush with the substrate after grinding, facilitating cup assembly without damage, and the substrate provides some protection for the coating within the recess. The metallographic structure of the coating sample prepared by this invention is shown in the figure. Figure 4 The surface condition of the coating after grinding is shown in the figure. Figure 5 .

[0031] For example, the inner shaft of an aircraft transmission system clutch requires a plasma-sprayed chromium oxide wear-resistant coating on its working surface.

[0032] Implementation process (1) Structure of the sprayed area, as shown above. Figure 1 As shown, the spraying area has a recessed structure on its outer diameter surface, with a depth of 0.1mm to 0.15mm, which is the final coating thickness.

[0033] (2) Use calipers to measure the outer diameter of the spraying area. It should meet the process requirements. Use organic solvents such as acetone to clean the surface of the clutch inner shaft to be sprayed and the adjacent surface until there is no visible oil or dirt on the surface, and then let it air dry.

[0034] (3) Install sandblasting protective fixtures to protect the non-sandblasted parts of the parts. Sandblast the surface of the parts to be coated. After sandblasting, the parts should have a uniform rough surface without metallic luster. The surface roughness requirement for sandblasting is Ra≥4μm.

[0035] (4) Replace the spraying protection fixture, clamp the parts, and place the compressed air cooling pipe from the side and rear of the parts; set the automatic spraying points of the robot: according to the axial length of the inner shaft surface of the clutch, set the automatic spraying points of the robot at two boundaries, and name the spraying points A and B. The spray gun is at 90° with the surface, the spray gun moving speed is 10mm / s, and the spray gun moves in a cycle along the path A→B→A; set the rotation speed of the parts to 130r / min~150r / min.

[0036] (5) Preheat the area to be sprayed at a temperature of 50℃~120℃. The spray gun can be used for direct preheating. Spray a chromium oxide coating with powder composition of Cr2O3≥99.5%, TiO2≤0.1%, Al2O3≤0.2%, Fe2O3≤0.4%, and SiO2≤0.45%. The plasma spraying equipment is: Metco 9M; nozzle model: GH; powder feed rate: 25%; argon pressure: 75Psi±5Psi; argon flow rate: 80SCFH±5SCFH; hydrogen pressure: 50±5 Psi; hydrogen flow rate: 22SCFH~29SCFH; powder feed gas pressure: 3.5bar±0.2 bar; powder feed gas flow rate: 8±0.5; current: 630A; voltage: 75V; spraying distance: 65 mm±10 mm; spraying angle: 90°; and coating thickness: 0.25 mm~0.35 mm. During the spraying process, compressed air is used to cool the part substrate from the side and rear. At the same time, after every two spraying cycles, the spraying is stopped, waited for 2 minutes, and then resumed. An infrared thermometer is used to monitor the part temperature in real time during the spraying process to ensure that the part temperature does not exceed 150℃.

[0037] (6) Disassemble the spraying protective fixture, clean the parts, check the appearance of the sprayed coating, and measure the outer diameter of the sprayed area with calipers. It should meet the process specifications. After spraying, if... Figure 6 As shown.

[0038] The parts are clamped, and the coating is ground using a 320-grit diamond grinding wheel. The rough grinding wheel speed is 1400 rpm with a feed rate of 0.005 mm to 0.010 mm, and the finish grinding wheel speed is 1400 rpm with a feed rate of 0.002 mm to 0.005 mm. The coating after grinding is as follows: Figure 7 As shown.

[0039] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for spraying a chromium oxide wear-resistant coating onto the surface of a transmission shaft part, characterized in that, The method includes: The spraying area of ​​the drive shaft is designed with a concave structure and a pre-set chamfer on the right side; Install protective fixtures to protect the non-sprayed / sandblasted parts of the parts, while the sprayed / sandblasted parts of the parts are exposed to the protective fixtures. Compressed air is used to cool the parts from the side and rear. The robot's automatic spraying points, spray gun movement speed, and part rotation speed are set. Preheat the area to be sprayed using a spray gun; The chromium oxide coating is sprayed according to the specified spraying parameters, and the powder morphology is spherical. During the spraying process, compressed air is used to cool the part substrate from the side and rear. At the same time, after every two spraying cycles, the spraying is stopped, waited for 2 minutes, and then resumed. An infrared thermometer is used to monitor the part temperature in real time during the spraying process to ensure that the part temperature does not exceed 150℃. Disassemble the fixture and clean the parts; The coating is ground using a diamond grinding wheel.

2. The method according to claim 1, characterized in that, The preset chamfer is 20° to 30°.

3. The method according to claim 1, characterized in that, The spraying area of ​​the drive shaft is designed as a concave structure, with a pre-set chamfer on the right side, including: Use acetone organic solvent to clean the surface of the part to be sprayed and the adjacent surfaces until there is no visible oil or dirt, and then air dry.

4. The method according to claim 3, characterized in that, The installation protective fixture protects the non-sprayed / sandblasted parts of the part. After the sprayed / sandblasted parts of the part are exposed from the protective fixture, it also includes: The surface of the sprayed / sandblasted area shall be sandblasted. After sandblasting, the sprayed surface of the part shall be a uniform rough surface without metallic luster. The surface roughness requirement for sandblasted surface is Ra≥4μm.

5. The method according to claim 1, characterized in that, The powder composition is Cr2O3 ≥ 99.5%, TiO2 ≤ 0.1%, Al2O3 ≤ 0.2%, Fe2O3 ≤ 0.4%, and SiO2 ≤ 0.45%.

6. The method according to claim 1, characterized in that, The preheating temperature is 50℃~120℃.

7. The method according to claim 1, characterized in that, The spraying parameters include: The plasma spraying equipment is: Metco 9M; Nozzle type: 732 or GH; Powder delivery rate: 25%; Argon pressure: 75Psi±5Psi; Argon flow rate: 80 SCFH ± 5 SCFH; Hydrogen pressure: 50±5 Psi; Hydrogen flow rate: 22 SCFH~29 SCFH; Powder delivery air pressure: 3.5 bar ± 0.2 bar; Powder delivery airflow rate: 8±0.5; Current: 630A±5A; Voltage: 75V±2V; Spraying distance: 65 mm ± 10 mm, spraying angle: 80°~90°, coating thickness: 0.25 mm~0.35 mm.

8. The method according to claim 1, characterized in that, The setting of the robot's automatic spraying points, spray gun movement speed, and part rotation speed includes: Set the automatic spraying points for the robot, the spray gun movement speed to 10mm / s, and the part rotation speed to 130r / min~150r / min.

Images