Plasma spraying method for preparing coating on inner wall of part with diameter of 60 mm and part

Abstract

The invention provides a plasma spraying method for preparing a coating on the inner wall of a component with the diameter being 60 mm and the component, spraying is conducted depending on an atmosphere long laminar flow plasma system, a spray gun of the system can generate long laminar flow plasma jet flow not smaller than 700 mm, and the method comprises the steps that the long and thin component and spraying powder are selected, the relative position and angle between the slender component and the spray gun are set, and a proper spraying distance range is selected within the long jet length; the powder feeding unit is used for feeding powder into the spray gun for spraying according to the set spraying parameters; and through self rotation of the slender part and vertical translation movement of the spray gun, the molten particle flow uniformly covers the inner wall of the slender part in the spraying length within a proper spraying distance range, so that at least one thermal barrier coating corresponding to at least one spraying powder is prepared on the inner wall of the slender part. According to the method provided by the invention, the problems that the thermal barrier coating of the thin and long component with the diameter of 40mm-60mm is difficult to spray and the spraying quality is poor are solved.

Description

Technical Field

[0001] The present application relates to the technical field of inner hole plasma spraying, and in particular to a plasma spraying method and component for preparing a coating on the inner wall of a component with a diameter of 60 mm. Background Art

[0002] Plasma spraying is a thermal spraying method commonly used for surface enhancement and the preparation of functional coatings. It is widely used in aerospace, energy, and machinery manufacturing. In practice, compared to external surface spraying, plasma spraying the inner surface (i.e., inner bore) of a component presents higher technical challenges and equipment requirements. This is particularly true for slender tubular inner bore fittings, which present significant technical bottlenecks.

[0003] In the internal hole plasma spraying process, spraying distance is one of the key parameters affecting coating quality. Spraying distances that are too close or too far will increase the coating porosity, affecting the coating's density and bonding strength. If the spraying distance is too close, the powder will not have enough time to heat up, and the impact deformation will not be sufficient. At the same time, the workpiece will be rapidly heated by the high-temperature plasma flame ejected from the spray gun, resulting in excessive temperature rise, severe oxidation, and even coating shedding. Conversely, if the spraying distance is too far, the powder, which has been heated to a molten state, will cool down by the time it reaches the substrate surface, slowing its flight speed and reducing the coating quality.

[0004] Especially for parts with a hole diameter less than 80 mm, a large depth or a complex structural shape, the traditional internal hole plasma spraying equipment has limited spray gun length and flexibility, the length of the plasma jet generated by the spray gun is short, and the spray gun has difficulty entering small or complex internal holes, resulting in the spray gun being unable to spray the internal holes of slender parts within the appropriate spraying distance range, making the spraying operation more difficult. Summary of the Invention

[0005] To address the above-mentioned issues, one objective of the present invention is to provide a plasma spraying method for applying a thermal barrier coating to the inner wall of a slender component with a diameter of 60 mm. This method addresses the difficulty and poor quality of spraying thermal barrier coatings on slender components with diameters between 40 mm and 60 mm. A second objective of the present invention is to provide a slender component with a thermal barrier coating.

[0006] To achieve one of the objectives, in a first aspect, the present invention provides a plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm, the technical solution of which is as follows: A plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm, relying on an atmospheric long laminar flow plasma system for spraying. The spray gun in the atmospheric long laminar flow plasma system is used to directly generate a plasma jet under atmospheric conditions. The plasma jet has a jet length of not less than 700 mm and is in a laminar flow state. The method comprises the following steps: S1. Prepare a substrate to be sprayed, wherein the substrate comprises an elongated component with an inner hole diameter of 40 mm to 60 mm; S2. selecting at least one spray powder for preparing at least one layer of thermal barrier coating; S3. Setting the relative position and angle between the slender component and the spray gun to adjust the spray distance range of the spray gun during the reciprocating motion; wherein the spray distance range is within the jet length, and the limit difference of the spray distance range is adapted to the required spray length of the slender component; S4. adjusting the spraying parameters of the atmospheric laminar flow plasma system according to the thickness of the elongated component to be sprayed and the type of the corresponding spraying powder; S5. Based on the spraying parameters, using a powder feeding unit in the atmospheric laminar flow plasma system to feed powder into the spray gun, controlling the spray gun to spray a molten particle flow carrying any one of the spray powders, so that the molten particle flow penetrates into the inner wall of the elongated component; S6. Control the slender member to rotate about its own central axis, and at the same time control the spray gun to move in a direction inclined to the central axis, so that the molten particle flow uniformly covers the inner wall of the slender member along the spraying length within the spraying distance range, thereby preparing at least one layer of thermal barrier coating corresponding to at least one of the spraying powders on the inner wall of the slender member.

[0007] As one of the preferred solutions, step S3 includes: S31, rotating and fixing the slender member on a chuck fixture, setting a first preset angle between the central axis of the slender member and a horizontal plane; S32, fixing the spray gun on the robotic arm, and controlling the spray gun to be parallel to a horizontal plane, so that the plasma jet ejected by the spray gun is parallel to the horizontal plane and has the first preset angle with the elongated member; S33, controlling the robotic arm to move until the spray gun and the end of the slender component away from the chuck fixture have a first preset distance; the first preset distance represents the upper limit of the spraying distance range.

[0008] As one of the preferred solutions, step S6 includes: S61, using the chuck fixture to drive the elongated member to rotate around a central axis that is at a first preset angle to the horizontal plane; S62. Use the robotic arm to drive the spray gun to move back and forth in a direction perpendicular to the horizontal plane, so that the molten particle flow ejected from the spray gun is circulated and sprayed between one end of the slender tube away from the chuck fixture and the other end close to the chuck fixture; wherein, the end of the slender part close to the chuck fixture has a second preset distance from the spray gun, and the second preset distance represents the lower limit of the spraying distance range.

[0009] As one of the preferred solutions, the first preset distance is the distance between the front end of the slender member and the spray gun, and the second preset distance is the distance between the rear end of the slender member and the spray gun.

[0010] As one of the preferred solutions, the spraying powder selected in step S2 includes at least one of YSZ powder, NiCrAlY powder, NiCoCrAlY powder and NiCrAlYHfSi powder.

[0011] As one of the preferred solutions, step S2 includes: S21. Select two spray powders for preparing a composite thermal barrier coating, wherein the first spray powder is YSZ powder, and the second spray powder is any one of NiCrAlY powder, NiCoCrAlY powder, and NiCrAlYHfSi powder; The step S5 comprises: S51, using the powder feeding unit in the atmospheric laminar flow plasma system, first feeding the second spray powder into the plasma jet zone in the spray gun, so as to prepare a metal bonding layer on the inner wall of the slender component by using the step S6; S52. Utilize the powder feeding unit in the atmospheric laminar flow plasma system to feed the YSZ powder into the plasma jet zone in the spray gun, so as to prepare a ceramic layer on the metal bonding layer by utilizing the step S6, thereby spraying a composite thermal barrier coating on the inner wall of the slender component.

[0012] As one of the preferred solutions, step S4 includes: S41, setting the number of spray cycles of the spray gun according to the inner hole diameter of the elongated component and the thickness to be sprayed; S42. Adjust the spraying parameters of the atmospheric long laminar flow plasma system according to the thickness to be sprayed and the type of the spraying powder.

[0013] As one of the preferred solutions, the step S1 includes: S11, performing sandblasting on the inner wall surface of the elongated component.

[0014] As one of the preferred solutions, the step S4 includes: S43, preheating the elongated component by using the plasma jet ejected from the spray gun.

[0015] To achieve the second objective, in a second aspect, the present invention provides a slender component with a thermal barrier coating, wherein the inner diameter of the slender component is 40 mm to 60 mm, and at least one layer of thermal barrier coating is sprayed on the inner wall of the slender component, and the thermal barrier coating is sprayed by relying on the plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm provided in the first aspect of the present invention.

[0016] Compared with the prior art, this application has the following advantages: The plasma spraying method provided in the embodiment of the present application utilizes long laminar plasma spraying technology to generate a laminar plasma jet with a length of not less than 700 mm. The 700 mm jet length supports the coverage of a magnetic field inner hole with a deeper depth and a smaller inner diameter under the condition of an external spray gun. Even in the case of narrow and slender inner hole components, the spray gun is moved externally, and a long laminar plasma jet is generated outside the inner hole. The spray gun only needs to be aimed at the inner hole mouth. The plasma jet can pass through the nozzle and act on the target inner wall. It can penetrate the inner hole within a suitable spraying distance for effective spraying, solving the problem that traditional spray guns cannot penetrate into small apertures due to size limitations. Therefore, relying on the atmospheric long laminar plasma system for spraying, a uniform and dense thermal barrier coating can be successfully prepared on the inner wall of a slender component with a diameter of 40mm-60mm, while reducing the difficulty of operation and maintenance costs, and improving the flexibility, scalability and adaptability of the emerging spraying process.

[0017] The advantages of the elongated member and the above method over the prior art are the same and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the description of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 This is a schematic diagram of the spraying principle of a plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm provided in one embodiment of the present application; Figure 2 This is a flow chart of the steps of a plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm, provided in one embodiment of the present application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0021] In order to understand the present invention more clearly, the method of performing inner hole spraying using traditional plasma spraying equipment is briefly described first. The plasma jet generated by the DC non-transferred arc plasma generator used in the plasma spraying equipment has a relatively short jet length, and the jet state of the plasma jet is usually irregular vortex motion turbulence. In the process of inner hole spraying, the spray gun usually needs to penetrate into the inner hole of the coated substrate for spraying. Therefore, for slender parts with small diameter and large length, due to the narrow spraying space and the complex structure, large volume and limited length of the spray gun, the spray gun is inconvenient to operate in the inner hole or cannot enter the inner hole, resulting in difficulty or even inability to spray. For example, the maximum length of some inner hole spray guns is limited. Even if a robotic arm is installed, it is easy to cause uneven coating due to shaking.

[0022] If you attempt to coat the inner hole using external spraying, the plasma jet produced by the plasma spray gun has a short jet length, which not only prevents it from covering the longer inner hole, but also prevents you from completing the inner hole spraying. Furthermore, the short jet length limits the adjustment range of the spray distance, making it impossible to select the appropriate spray distance for the inner hole. Spraying distances that are too close or too far will seriously affect the coating quality.

[0023] In addition, the irregular short turbulent plasma jet generated by traditional internal hole plasma spraying equipment is not only severely limited by the internal hole size or shape of the coated substrate, but also has the following problems: 1) Coating quality issues: During the plasma spraying process, due to the varying speeds and temperatures of the molten droplets, pores and cracks are prone to appear inside and on the surface of the coating. These defects reduce the density of the coating, thereby affecting its wear resistance, corrosion resistance, and bonding strength.

[0024] 2) Limited coating bond strength: The bond strength between the coating and the substrate is affected by various factors, such as pores, cracks, and residual stress within the coating. Residual stress is primarily caused by quenching stress generated during powder solidification shrinkage and the mismatch in thermal expansion coefficients between the substrate and coating.

[0025] 3) Operation and process limitations: Equipment costs are high. Plasma spraying equipment is usually expensive and requires professional operators to maintain and operate.

[0026] 4) Low spraying efficiency: Plasma spraying technology cannot be used to spray coatings on large areas, and requires a high level of technical skills from the operators, which limits the spraying efficiency.

[0027] 5) Low material utilization: During the spraying process, some materials cannot be effectively deposited on the substrate surface due to incomplete melting or oxidation, resulting in large material loss.

[0028] 5) Environmental and safety issues: During the spraying process, high-temperature, high-energy plasma arcs will be generated, which may produce harmful gases and dust, causing certain pollution to the environment.

[0029] 6) Harsh operating environment: Plasma spraying needs to be carried out in a high-temperature, high-energy environment. Operators need to take strict protective measures and the working environment is relatively harsh.

[0030] 7) Limited application scope: Due to the limitation of substrate materials, not all materials are suitable for plasma spraying. Some heat-sensitive materials or materials with low melting points may be damaged during high-temperature spraying.

[0031] As can be seen, to ensure coating quality, parameters such as spray distance and jet length need to be repeatedly optimized. However, existing internal bore plasma spraying equipment cannot support the spray gun to cover slender components with small diameters and deep bores without extending into the bore, hindering the difficulty of process development and implementation. In particular, the current diameter limit for internal bore spraying is only 80mm. Therefore, spraying thermal barrier coatings on the inner surface of parts with bores less than 80mm in diameter remains a major challenge for existing spraying processes. Therefore, the development of new internal bore ceramic coating spraying methods is crucial.

[0032] In view of this, the present invention provides a plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm. This method relies on an atmospheric long laminar flow plasma spraying system for spraying. The spray gun in the atmospheric long laminar flow plasma system is used to directly generate a plasma jet under atmospheric conditions. The jet length of the plasma jet is not less than 700 mm, and the jet state is laminar.

[0033] In this embodiment, a long laminar plasma jet is generated by a spray gun in an atmospheric long laminar plasma spray system. The long laminar plasma jet can be up to 700 mm long, with a single deposition width of approximately 6 mm. The long laminar plasma jet can penetrate deep into the inner wall of a slender component, and under atmospheric conditions, the flow characteristics of the plasma jet are laminar or quasi-laminar, which is completely different from the irregular short turbulent jet presented by a conventional DC non-transferred arc plasma jet, which is difficult to achieve with current conventional plasma spray equipment.

[0034] The use of atmospheric long laminar plasma spraying technology can achieve a high deposition rate, high production efficiency, and is suitable for large-scale production. This technology can complete the preparation of the coating in a short time and can produce a dense coating with low porosity and uniform coating. Due to the high temperature and high speed characteristics of the atmospheric long laminar plasma jet, the bonding strength between the coating and the substrate is high. By adjusting the spraying parameters, the microstructure and composition of the coating can be precisely controlled. It has strong material adaptability and can melt high-melting-point materials such as metals, alloys, carbides, ceramics and other powder raw materials. It is suitable for the preparation of a variety of high-performance coatings such as wear-resistant, corrosion-resistant, and heat-insulating coatings on a variety of substrates. It can achieve excellent coating thickness control, and the coating thickness can be precisely adjusted according to needs.

[0035] At present, atmospheric laminar plasma spraying technology is mainly used for spraying the outer surface of the substrate, and there is no optimized process method for spraying thermal barrier coatings on the inner surface of parts with inner holes less than 80 mm in diameter. Figure 2 As shown, Figure 2 A flow chart showing the steps of a plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm is shown. The method of spraying the inner hole of a slender component using a long laminar plasma jet in this embodiment includes the following steps: S1. Prepare a substrate to be sprayed, the substrate comprising a slender component with an inner hole diameter of 40 mm to 60 mm; Slender cylindrical components with an inner hole diameter of 40mm-60mm are selected as substrates to be sprayed, such as small-diameter high-temperature heat exchange tubes, turbine blade cooling hole sleeves, gas turbine nozzle inner tubes, etc., breaking through the current diameter limit (80mm) of inner hole spraying. The diameter limit of the applicable components for spraying using steps S2-S6 can be reduced to 40mm-60mm, so as to achieve uniform preparation of thermal barrier coatings on the inner walls of slender components with a minimum diameter of 40mm-60mm, filling the gap that current plasma spray equipment is difficult or impossible to perform inner hole spraying on slender components with small size or complex shape.

[0036] In this embodiment, the substrate may be cleaned and pre-treated before spraying. For example, after the slender component to be sprayed is prepared, step S11 is performed to perform sandblasting on the inner wall surface of the slender component to improve the coating adhesion.

[0037] S2. selecting at least one spray powder for preparing at least one layer of thermal barrier coating; The appropriate thermal barrier coating material is selected based on the application environment to provide functional protection in extreme high-temperature environments, achieving thermal insulation, oxidation resistance, and corrosion resistance. For example, the spray powder includes at least one of YSZ powder, NiCrAlY powder, NiCoCrAlY powder, and NiCrAlYHfSi powder. Using the spraying technology provided by the present invention, any one of these spray powders can deposit a single layer of thermal barrier coating on the inner wall of the tube. In this embodiment, a single spray powder can be used to form a single-layer thermal expansion coating on the inner wall of a slender component; alternatively, multiple powders can be sequentially sprayed onto the inner wall of the slender component to form a multi-layer composite thermal barrier coating.

[0038] S3. Setting the relative position and angle between the slender component and the spray gun to adjust the spray distance range of the spray gun during the reciprocating motion; wherein the spray distance range is within the jet length, and the limit difference of the spray distance range is adapted to the required spray length of the slender component; The relative position of the spray gun and the slender component is set, that is, the spray gun is located outside the slender component, and at the same time, the spray gun and the slender component form a certain inclination angle, so that the spray gun sprays the plasma jet toward the inner wall of the tube at a preset spray angle. The spray distance is the straight-line distance from the nozzle end face of the spray gun to the end face of the slender component. During the spraying process, the spray gun of this embodiment does not extend into the inner hole of the slender component, but is at a certain distance from the slender component. There are multiple distances along the length of the slender component, and these distances are the spray distances. The multiple distances constitute the spray distance range. It can be seen that it takes a while for the spray powder to be heated and accelerated in the plasma jet, so there should be a suitable spray distance range. If the spray distance is too far or too close, there will be many problems existing in the background technology.

[0039] In this embodiment, an appropriate spraying distance range can be selected based on the desired spraying length of the slender component to ensure coating uniformity and quality. For example, if the desired spraying length of the slender component is 150m, the difference between the spraying distance of the spray gun from the front end of the inner hole of the slender component (the shortest spraying distance) and the spraying distance from the rear end of the inner hole of the slender component (the longest spraying distance) is 150mm. Within this spraying distance range, the plasma jet emitted by the spray gun sprays along the distance from the front end to the rear end of the inner hole of the slender component, thereby achieving spraying along the desired spraying length of the slender component.

[0040] In a specific embodiment, depending on the actual application, the desired spraying length is preferably approximately equal to the overall length of the elongated component. The nozzle end face of the spray gun is spaced a first preset distance (e.g., 150 mm) from the frontmost face of the elongated component. This first preset distance is set as the shortest spraying distance, i.e., the upper limit of the spraying distance range. Similarly, the spray gun is also spaced a certain distance from the rearmost face of the elongated component. Therefore, the nozzle end face of the spray gun is spaced a second preset distance (e.g., 300 mm) from the rearmost face of the elongated component. This second preset distance is the longest spraying distance, i.e., the lower limit of the spraying distance range. Therefore, the difference between the limits of the spraying distance range (150 mm) is approximately equal to the total length of the elongated component, thereby better enabling spraying of the entire inner bore area of ​​the elongated component within the selected spraying distance range.

[0041] In some embodiments, the desired spraying length is set based on the selected slender component, thereby selecting a suitable spraying distance range. The jet length of the plasma jet directly affects the selection of the spraying distance. If the plasma jet length is shorter than the required spraying distance (for example, the jet length is only 140 mm and the spraying distance range requires 150 mm), the process window of the plasma jet is exceeded, and the spraying of the required spraying length cannot be completed. The atmospheric long laminar plasma system of this embodiment generates a laminar plasma jet of up to 700 mm. The long laminar jet can cover a suitable spraying distance and support the selection of a larger spraying distance range. The spraying distance can be within the length of the core area of ​​the plasma jet. Therefore, longer pipes can be sprayed at a suitable spraying distance, for example, a 200 mm long ceramic layer can be sprayed in a 250 mm long pipe.

[0042] Therefore, for slender components with diameters less than 80mm, the plasma jet ejected from this technology's spray gun can penetrate deep into the inner bore for spraying, extending the diameter limit of the inner bore to 40mm-60mm, overcoming the difficulty of traditional spray guns in entering small-diameter inner bores. Furthermore, the plasma jet sprays the inner bore within a suitable spraying distance, and the particles experience an exceptionally long heating and acceleration time in the plasma jet, maintaining a molten or semi-molten state, meeting the melting requirements of metal and ceramic coatings.

[0043] S4. Adjust the spraying parameters of the atmospheric laminar plasma system according to the thickness of the slender component to be sprayed and the type of corresponding spray powder; In order to ensure the stability of the spraying process and the quality of the coating, the spraying parameters of the atmospheric laminar plasma system are adjusted according to the thickness of the slender parts to be sprayed and the type of spray powder, such as arc power, movement speed of the spray gun and rotation speed of the slender parts, powder supply speed, position and speed, gas flow rate and temperature of the slender parts, to ensure that the powder can be fully melted and deposited without allowing the substrate temperature to be too high during the spraying process.

[0044] S5. Based on the spraying parameters, the powder feeding unit in the atmospheric laminar plasma system is used to feed powder into the spray gun, and the spray gun is controlled to spray a molten particle flow carrying any type of spray powder, so that the molten particle flow penetrates into the inner wall of the slender component; Under the set parameters, the spray gun generates a long laminar plasma jet, and the powder is fed into the spray gun by the powder feeding unit. The plasma jet heats and melts the spray powder to form a molten particle flow. The molten particle flow maintains a high-speed and high-temperature state in the laminar jet, can pass through the nozzle directly to the inner wall, impact and deposit on the inner wall to form a coating.

[0045] For spraying a single-layer thermal barrier coating, one type of spray powder is selected and fed, causing the corresponding molten particle flow to impact the inner wall to form a single-layer thermal barrier coating. For spraying a multi-layer thermal barrier coating, two or more types of spray powders are selected and fed sequentially. After the first molten particle flow impacts the inner wall to form the thermal barrier coating, another type of powder is fed, causing the second molten particle flow to impact the previous thermal barrier coating to form a composite thermal barrier coating.

[0046] S6. Control the slender component to rotate about its own central axis, and at the same time control the spray gun to move in a direction inclined to the central axis, so that the molten particle flow uniformly covers the inner wall of the slender component along the spraying length within the spraying distance range, thereby preparing at least one layer of thermal barrier coating corresponding to at least one spray powder on the inner wall of the slender component.

[0047] like Figure 1 As shown, Figure 1 This diagram illustrates the plasma spraying principle for applying a thermal barrier coating to the inner wall of a 60mm diameter slender component in this example. The diagram shows the coating process of a substrate from three different gun positions. The diagram also illustrates the uniform rotation direction, with the central axis perpendicularly passing through the center of the component and inclined relative to the horizontal plane. The reciprocating motion of the gun is also illustrated. The gun is horizontal but reciprocates perpendicularly to the horizontal plane. The horizontal plasma jet from the gun forms an angle with the tangent of the tube wall, which is the same angle as the inclination of the central axis. The vertical motion also forms an angle with the inclined central axis. In this step, the slender component is controlled to rotate at a constant speed along its own central axis, and the spray gun is controlled to move back and forth at an angle with the moving direction of the slender component. The plasma jet will not be ejected parallel to the inside of the slender component, causing the plasma jet to penetrate the inner hole, nor will the plasma jet be ejected outside the inner hole of the slender component during the movement. Through the rotation of the slender component and the translational movement of the spray gun, the molten particle flow can cover the inner wall in an all-round and uniform manner, forming a uniform thermal barrier coating.

[0048] The spray gun's travel speed is systematically matched to the component's rotational speed, ensuring uniform heating and consistent coating thickness along the component's inner wall area along the desired spray length. If multiple coats are required, steps S3-S6 can be repeated after the first coat of thermal barrier coating, using different powders and corresponding spray parameters to create a multi-layer composite thermal expansion coating.

[0049] In summary, the long laminar plasma spraying technology is used to generate a laminar plasma jet with a length of not less than 700mm. The 700mm jet length supports the coverage of magnetic field inner holes with a deeper depth and a smaller inner diameter under the condition of an external spray gun. Even in the case of narrow and slender inner hole components, the spray gun is moved externally, and a long laminar plasma jet is generated on the outside of the inner hole. The spray gun only needs to be aimed at the inner hole mouth. The plasma jet can pass through the nozzle and act on the target inner wall. It can penetrate the inner hole within the appropriate spraying distance for effective spraying, solving the problem that traditional spray guns cannot penetrate into small apertures due to size limitations. Therefore, relying on the atmospheric long laminar plasma system for spraying, a uniform and dense thermal barrier coating was successfully prepared on the inner wall of slender components with a diameter of 40mm-60mm. At the same time, the operation difficulty and maintenance cost were reduced, and the flexibility, scalability and adaptability of the emerging spraying process were improved.

[0050] As a further illustration of this embodiment, step S3 includes: S31, rotating and fixing the slender component on the chuck fixture, setting a first preset angle between the central axis of the slender component and the horizontal plane; S32, fixing the spray gun on the robotic arm, and controlling the spray gun to be parallel to the horizontal plane so that the plasma jet ejected by the spray gun is parallel to the horizontal plane and has a first preset angle with the slender component; S33, controlling the robotic arm to move until the spray gun and the end of the slender component away from the chuck fixture have a first preset distance; the first preset distance represents the upper limit of the spraying distance range.

[0051] Correspondingly, step S6 includes: S61, using a chuck fixture to drive the elongated component to rotate around a central axis that is at a first preset angle to the horizontal plane; S62. Use a robotic arm to drive the spray gun to move back and forth in a direction perpendicular to the horizontal plane, so that the molten particle flow ejected from the spray gun is circulated and sprayed between the end of the slender tube away from the chuck fixture and the end close to the chuck fixture; wherein, the end of the slender part close to the chuck fixture has a second preset distance from the spray gun, and the second preset distance represents the lower limit of the spraying distance range.

[0052] Please refer again Figure 1In this embodiment, the angle between the spray gun and the slender component is adjusted to ensure that the plasma jet can contact the desired spraying position of the slender component while maximizing the angle between the jet and the substrate to maximize the coating deposition quality. The slender component is fixed using a CNC chuck fixture, and the slender component is tilted so that the central axis of the slender component forms a first preset angle with the horizontal plane, such as 20°. The spray gun is mounted on an industrial six-axis robot arm so that the spray gun is parallel to the horizontal plane so that the jet axis is parallel to the horizontal plane. Therefore, the tilted slender component cooperates with the horizontally set spray gun, so that the molten particles can pass through the nozzle and penetrate into the inner hole to be sprayed onto the inner wall of the pipe on the vertical translation trajectory of the spray gun, avoiding the pipe inlet blocking the jet or the jet passing through the inner hole in parallel. By setting the angle between the slender component and the horizontal plane, the incident angle of the plasma jet is adjusted, and the vertical translation of the horizontally set spray gun can easily control the direction of the plasma jet, reducing the difficulty of operation.

[0053] The spray gun is positioned relative to the elongated member, with the spray gun positioned outside the elongated member, with a first preset distance between the two. This allows the molten particle flow to be deposited on the tube wall over the first preset distance, thereby initiating spraying at an appropriate spraying distance. The first preset distance can be set to determine the upper limit of the spraying distance range, that is, to prevent the spray gun from being too close to the inner hole at the shortest spraying distance, ensuring that the molten particle flow remains within the appropriate spraying distance range during the spraying process, thereby achieving optimal coating quality and uniformity.

[0054] Similarly, a second preset distance is set based on the desired spray length to control the lower limit of the spray distance range. This prevents the spray gun from being too far away from the inner hole at the longest spray distance, ensuring that the molten particle flow remains within the appropriate spray distance range during the spraying process. Therefore, the robotic arm is controlled to drive the spray gun in a reciprocating translation perpendicular to the horizontal plane, causing the molten particle flow to circulate from the far end of the pipe (the second preset distance) to the near end (the first preset distance), achieving complete coverage along the length of the inner hole, improving uniformity and density, and spraying to the desired spray thickness through the number of cycles.

[0055] Preferably, the first preset distance is the distance between the front end of the slender component and the spray gun, and the second preset distance is the distance between the rear end of the slender component and the spray gun. Therefore, the spraying start and end points are located at the front and rear ends of the slender component, and the entire inner wall can be sprayed on the outside.

[0056] It will be appreciated that in actual spraying, the rear end of the elongated component is used to clip into the chuck fixture. Therefore, the second predetermined distance is more specifically the distance between the near-rear end of the elongated component and the spray gun. For example, a ceramic layer up to 200 mm long can be sprayed in a 250 mm long pipe at one time, extending from the front end to the rear end of the pipe.

[0057] Preferably, step S2 includes: S21. Select two spray powders for preparing a composite thermal barrier coating, wherein the first spray powder is YSZ powder, and the second spray powder is any one of NiCrAlY powder, NiCoCrAlY powder, and NiCrAlYHfSi powder; Correspondingly, step S5 includes: S51, using the powder feeding unit in the atmospheric long laminar flow plasma system, first feeding the second spray powder into the plasma jet zone in the spray gun, so as to form a metal bonding layer on the inner wall of the slender component according to step S6; S52. Using the powder feeding unit in the atmospheric long laminar flow plasma system, the YSZ powder is fed into the plasma jet zone in the spray gun to prepare a ceramic layer on the metal bonding layer using step S6, thereby spraying a composite thermal barrier coating on the inner wall of the slender component.

[0058] After selecting the spray powder to be sprayed, the coating can be sprayed in sections in sequence through steps S3 to S6. Through steps S51 and S52, a YSZ+NiCrAlY coating, a YSZ+NiCoCrAlY coating or a YSZ+NiCrAlYHfSi coating can be obtained.

[0059] YSZ+NiCrAlY, YSZ+NiCoCrAlY, or YSZ+NiCrAlYHfSi coatings are widely used to protect components in high-temperature environments, such as aircraft engine blades and gas turbines. NiCrAlY / NiCoCrAlY / NiCrAlYHfSi serve as a bonding layer, primarily to resist high-temperature oxidation. At high temperatures, the aluminum in NiCrAlY / NiCoCrAlY / NiCrAlYHfSi is preferentially oxidized, forming a dense α-Al2O3 layer that effectively blocks oxygen diffusion. The introduction of YSZ reduces the coating's porosity, further slowing the growth of the aluminum oxide layer and improving the coating's oxidation resistance. Consequently, the composite thermal expansion coating can withstand over 600 thermal cycles at 1100°C for 10 minutes and then 5 minutes of cooling.

[0060] Specifically, NiCrAlY powder, NiCoCrAlY powder or NiCrAlYHfSi powder is firstly plasma sprayed using a coaxial carrier gas powder feeding device to a spray thickness of 100 μm. Then, YSZ powder is plasma sprayed using a coaxial carrier gas powder feeding device to a spray thickness of 200 μm-300 μm.

[0061] Furthermore, step S4 includes: S41, setting the number of spray cycles of the spray gun according to the inner hole diameter of the slender component and the thickness to be sprayed; S42. Adjust the spraying parameters of the atmospheric long laminar flow plasma system according to the thickness to be sprayed and the type of spraying powder.

[0062] Furthermore, step S4 includes: S43. After calculating the number of spraying cycles and setting the spraying parameters, the slender component is preheated by the plasma jet ejected from the spray gun before powder spraying.

[0063] This embodiment can calculate the thickness deposited by each spraying and the number of spraying cycles required, in combination with the inner hole diameter and thickness requirements. In each cycle, the spray gun is controlled to move vertically and horizontally once, gradually reaching the designed spraying thickness. The spraying thickness is also related to the type of spraying powder and the spraying parameters. The spraying parameters of the atmospheric long laminar flow plasma equipment are adjusted according to different spraying powders to ensure that the powder can be fully melted and deposited, while preventing the substrate temperature from being too high during the spraying process. By setting the spraying parameters of the plasma spraying system to adapt to different coating thickness requirements and spraying powder characteristics, the best spraying quality at the required spraying thickness can be obtained.

[0064] The following provides specific examples to illustrate the present invention in detail.

[0065] A spraying method for preparing a YSZ+NiCrAlYHfSi composite thermal barrier coating on the inner wall of a cylinder with an inner diameter of 40 mm and a length of 250 mm comprises the following steps: Step 1: Prepare the cylinder to be coated and sandblast the inner surface of the cylinder to enhance the coating deposition quality. The dimensions of the cylinder are: inner diameter 40 mm; length 300 mm; wall thickness 5 mm.

[0066] Step 2: Secure the cylinder with a rotary chuck fixture, keeping it at a 20° angle to the horizontal. The spray gun is fixed horizontally on the robotic arm, approximately 150 mm from the front end of the cylinder.

[0067] Step 3: Calculate the number of spraying cycles based on the inner diameter of the cylinder and the required coating thickness.

[0068] According to the selected YSZ powder, set the current to 158A, voltage to 140V, and spray gun movement speed to 200mm·s -1 The rotation speed of the chuck is 0.4 r·min -1 , the working gas is N2 / Ar, N2 / Ar is 7:3, the total gas flow is 8.5splm, the maximum spraying distance is 300mm, and the powder feeding rate is 6gmin -1 , spraying thickness is 200μm.

[0069] According to the selected NiCrAlYHfSi powder, the current is set to 110A, the voltage is 120V, and the spray gun movement speed is 400mm·s -1 The rotation speed of the chuck is 0.8 r·min -1 , the working gas is N2 / Ar, N2 / Ar is 5:5, the total gas flow is 8.5splm, the maximum spraying distance is 300mm, and the powder feeding rate is 6gmin -1 , spraying thickness is 100μm.

[0070] Step 4: Turn on the power, circulating water and gas of the long laminar plasma spray system.

[0071] Step 5: Turn on the plasma spray gun and preheat the cylinder first.

[0072] In step 6, the plasma spray powder feeding unit is turned on and spraying is started according to the spraying parameters set for the NiCrAlYHfSi powder. Through the translational motion of the jet and the rotational motion of the cylinder, a coating is successfully prepared on the inner surface of the slender component.

[0073] Step 7: Prepare and spray the NiCrAlYHfSi coating of required thickness according to the set number of cycles.

[0074] In step 8, the plasma spray powder feeding unit is turned on and spraying is started according to the spraying parameters set for the YSZ powder. Through the translational motion of the jet and the rotational motion of the cylinder, a coating is successfully prepared on the inner surface of the slender component.

[0075] Step 9: Prepare and spray the YSZ coating of required thickness according to the set number of cycles to form a YSZ+NiCrAlYHfSi composite thermal barrier coating.

[0076] Step 10: Turn off the plasma spray equipment and powder feeding unit.

[0077] Step 11. Check the coating appearance.

[0078] Step 12: Perform subsequent tests such as high-temperature thermal cycling on the coating.

[0079] Therefore, this method can be used to uniformly prepare metal coatings and ceramic coatings on the inner wall of slender components with a minimum diameter of 40mm-60mm. The maximum length of the component can reach 200mm, and the coating deposition efficiency is greater than 40μm / min.

[0080] In summary, the long laminar plasma spraying technology is used to generate a laminar plasma jet with a length of not less than 700mm. The 700mm jet length supports the coverage of magnetic field inner holes with a deeper depth and a smaller inner diameter under the condition of an external spray gun. Even in the case of narrow and slender inner hole components, the spray gun is moved externally, and a long laminar plasma jet is generated on the outside of the inner hole. The spray gun only needs to be aimed at the inner hole mouth. The plasma jet can pass through the nozzle and act on the target inner wall. It can penetrate the inner hole within the appropriate spraying distance for effective spraying, solving the problem that traditional spray guns cannot penetrate into small apertures due to size limitations. Therefore, relying on the atmospheric long laminar plasma system for spraying, a uniform and dense thermal barrier coating was successfully prepared on the inner wall of slender components with a diameter of 40mm-60mm. At the same time, the operation difficulty and maintenance cost were reduced, and the flexibility, scalability and adaptability of the emerging spraying process were improved.

[0081] It should be noted that, for the method embodiments, the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously.

[0082] Correspondingly, in the second aspect, the present invention also provides a slender component with a thermal barrier coating, the inner diameter of the slender component is 40mm-60mm, and at least one layer of thermal barrier coating is sprayed on the inner wall of the slender component, and the thermal barrier coating is sprayed by relying on the plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60mm provided in the first aspect of the present invention.

[0083] As for the above-mentioned product embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can continue to refer to the partial description of the system embodiment.

[0084] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0085] It should also be noted that, in this article, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or terminal device.

[0086] The above describes in detail the plasma spraying method and components for preparing a coating on the inner wall of a component with a diameter of 60 mm provided by this application. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above embodiments is only intended to help understand this application, and the content of this specification should not be construed as limiting this application. At the same time, for those skilled in the art, according to this application, there will be various changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all implementation methods here, and obvious changes or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm, characterized in that: The method relies on an atmospheric long laminar flow plasma system for spraying, wherein the spray gun in the atmospheric long laminar flow plasma system is used to generate a plasma jet directly under atmospheric conditions, the jet length of the plasma jet is not less than 700 mm, and the jet state is a laminar flow state; the method comprises the following steps: S1. Prepare a substrate to be sprayed, wherein the substrate comprises an elongated component with an inner hole diameter of 40 mm to 60 mm; S2. selecting at least one spray powder for preparing at least one layer of thermal barrier coating; S3. Setting the relative position and angle between the slender component and the spray gun to adjust the spray distance range of the spray gun during the reciprocating motion; wherein the spray distance range is within the jet length, and the limit difference of the spray distance range is adapted to the required spray length of the slender component; S4. adjusting the spraying parameters of the atmospheric laminar flow plasma system according to the thickness of the elongated component to be sprayed and the type of the corresponding spraying powder; S5. Based on the spraying parameters, using a powder feeding unit in the atmospheric laminar flow plasma system to feed powder into the spray gun, controlling the spray gun to spray a molten particle flow carrying any one of the spray powders, so that the molten particle flow penetrates into the inner wall of the elongated component; S6. Control the slender member to rotate about its own central axis, and at the same time control the spray gun to move in a direction inclined to the central axis, so that the molten particle flow uniformly covers the inner wall of the slender member along the spraying length within the spraying distance range, thereby preparing at least one layer of thermal barrier coating corresponding to at least one of the spraying powders on the inner wall of the slender member.

2. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 1, characterized in that: The step S3 comprises: S31, rotating and fixing the slender member on a chuck fixture, setting a first preset angle between the central axis of the slender member and a horizontal plane; S32, fixing the spray gun on the robotic arm, and controlling the spray gun to be parallel to a horizontal plane, so that the plasma jet ejected by the spray gun is parallel to the horizontal plane and has the first preset angle with the elongated member; S33, controlling the robotic arm to move until the spray gun and the end of the slender component away from the chuck fixture have a first preset distance; the first preset distance represents the upper limit of the spraying distance range.

3. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 2, characterized in that: The step S6 comprises: S61, using the chuck fixture to drive the elongated member to rotate around a central axis that is at a first preset angle to the horizontal plane; S62. Use the robotic arm to drive the spray gun to move back and forth in a direction perpendicular to the horizontal plane, so that the molten particle flow ejected from the spray gun is circulated and sprayed between one end of the slender tube away from the chuck fixture and the other end close to the chuck fixture; wherein, the end of the slender part close to the chuck fixture has a second preset distance from the spray gun, and the second preset distance represents the lower limit of the spraying distance range.

4. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 3, characterized in that: The first preset distance is the distance between the front end of the slender member and the spray gun, and the second preset distance is the distance between the rear end of the slender member and the spray gun.

5. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 1, characterized in that: The spraying powder selected in step S2 includes at least one of YSZ powder, NiCrAlY powder, NiCoCrAlY powder and NiCrAlYHfSi powder.

6. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 5, characterized in that: The step S2 comprises: S21. Select two spray powders for preparing a composite thermal barrier coating, wherein the first spray powder is YSZ powder, and the second spray powder is any one of NiCrAlY powder, NiCoCrAlY powder, and NiCrAlYHfSi powder; The step S5 comprises: S51, using the powder feeding unit in the atmospheric laminar flow plasma system, first feeding the second spray powder into the plasma jet zone in the spray gun, so as to prepare a metal bonding layer on the inner wall of the slender component by using the step S6; S52. Utilize the powder feeding unit in the atmospheric laminar flow plasma system to feed the YSZ powder into the plasma jet zone in the spray gun, so as to prepare a ceramic layer on the metal bonding layer by utilizing the step S6, thereby spraying a composite thermal barrier coating on the inner wall of the slender component.

7. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 3, characterized in that: The step S4 comprises: S41, setting the number of spray cycles of the spray gun according to the inner hole diameter of the elongated component and the thickness to be sprayed; S42. Adjust the spraying parameters of the atmospheric long laminar flow plasma system according to the thickness to be sprayed and the type of the spraying powder.

8. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 7, characterized in that: The step S4 then includes: S43, preheating the elongated component by using the plasma jet ejected from the spray gun.

9. The plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm according to claim 3, characterized in that: The step S1 then includes: S11, performing sandblasting on the inner wall surface of the elongated component.

10. An elongated component having a thermal barrier coating, characterized in that The inner diameter of the slender component is 40 mm-60 mm, and at least one layer of thermal barrier coating is sprayed on the inner wall of the slender component, and the thermal barrier coating is sprayed by relying on the plasma spraying method for preparing a thermal barrier coating on the inner wall of a slender component with a diameter of 60 mm as described in any one of claims 1 to 9.

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