A hydraulic support cylinder and a method for spraying a high-corrosion-resistant ceramic composite coating on the surface thereof

Abstract

The application provides a hydraulic support cylinder and a method for spraying a high-corrosion-resistance ceramic composite coating on the surface of the hydraulic support cylinder, which comprises the following steps: laser cladding an austenitic stainless steel layer on the outer circle of the cylinder by using Fe-Ni alloy powder as raw material; after laser texturing treatment of the austenitic stainless steel layer, spraying an outer WC layer on the surface of the austenitic stainless steel layer by using tungsten carbide-based thermal spraying powder as raw material for the first time; carrying out copper plating treatment on the inner hole of the cylinder to form a copper plating layer; spraying an inner WC layer on the surface of the copper plating layer by using tungsten carbide-based thermal spraying powder as raw material for the second time; and causing the copper plating layer to be slightly melted, and then causing metallurgical combination to occur between the copper plating layer and the bonding surface of the inner WC layer. The method for spraying a high-corrosion-resistance ceramic composite coating on the surface of the hydraulic support cylinder can improve the corrosion resistance and wear resistance of the hydraulic support cylinder with water as the hydraulic medium, improve the bonding force between different corrosion-resistant layers, reduce the porosity of the sprayed layer, and simplify the processing technology.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection for hydraulic supports, and more specifically, to a method for spraying a highly corrosion-resistant ceramic composite coating onto the cylinder of a hydraulic support. Background Technology

[0002] Currently, hydraulic support cylinders using industrial pure water or even simply filtered mine water as the hydraulic medium require higher corrosion resistance. Existing cylinder surface treatment processes mainly include copper plating, chromium plating, arc cladding of copper alloys, laser cladding of stainless steel, and supersonic spraying of wear-resistant layers. However, electroplating is a physical bonding process with poor adhesion and a thin coating. Arc cladding of copper alloys results in low hardness and poor wear resistance. Laser cladding of stainless steel is difficult to balance with corrosion resistance and hardness. Existing supersonic spraying of WC ceramics suffers from poor adhesion and brittleness, easily peeling off from the substrate upon impact, thus losing its protective effect. Therefore, a single anti-corrosion method cannot meet the corrosion resistance requirements of hydraulic support cylinders using water as the hydraulic medium. Combining two or more anti-corrosion methods can lead to weak adhesion between different anti-corrosion layers or mutual interference in their performance.

[0003] Patent application CN115747800A discloses an ultra-high corrosion and wear-resistant composite coating for piston rod surfaces and its preparation method. The composite coating includes an alloy cladding layer and a sprayed layer. The cladding layer is fused onto the piston rod surface, and the sprayed layer is sprayed onto the cladding layer. A sealing agent is used to fill the pores of the sprayed layer. The preparation method involves using laser cladding to prepare the Fe-Ni alloy cladding layer and using thermal spraying to prepare the WC-based material sprayed layer, sealing the microscopic surface pores of the sprayed layer. The cladding layer and sprayed layer prepared by this ultra-high corrosion and wear-resistant composite coating for piston rod surfaces can provide long-term corrosion protection for piston rods, enabling them to withstand the highly corrosive marine environment. However, this method is only suitable for piston rod surfaces with a large operating space. When directly applied to the corrosion protection of the inner wall of a hydraulic cylinder in a semi-enclosed environment with a small operating space, interference may prevent spraying. Meanwhile, this method also employs sandblasting and sealing agent coating, which leads to poor adhesion between the cladding layer and the sprayed layer, as well as porosity in the sprayed layer during use. Therefore, this method still cannot meet the requirements for corrosion resistance and wear resistance of hydraulic support cylinder barrels that use water as the hydraulic medium. Summary of the Invention

[0004] To meet the requirements for corrosion resistance and wear resistance of hydraulic support cylinder barrels using water as the hydraulic medium, and to improve the bonding force between different anti-corrosion layers, reduce the porosity of the sprayed coating, and simplify the processing technology, this invention mainly involves two aspects. First, laser cladding of high corrosion-resistant austenitic stainless steel is applied to the outer circumference of the cylinder barrel. After laser roughening, an outer WC layer is then applied using supersonic spraying. This forms two coating layers on the cylinder barrel surface: the first layer provides high corrosion resistance, and the second layer provides high hardness and high wear resistance. Second, after electroplating copper into the inner bore of the cylinder barrel, a supersonic spraying process is used to apply an inner WC layer. By shortening the distance between the spray gun and the workpiece surface, and increasing the spraying flame temperature and velocity, micro-melting of the copper plating layer in the inner bore is achieved. This ensures metallurgical bonding between the inner WC layer and the copper plating layer, reducing the porosity of the inner WC layer. This solves the problems of poor corrosion resistance and unavoidable porosity in the inner WC layer, improving the corrosion resistance of the inner bore and enhancing the impact resistance of the inner bore coating.

[0005] Specifically, the technical solution adopted in this invention is: a method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder, comprising the following steps: Step 1: Using Fe-Ni alloy powder as raw material, an austenitic stainless steel layer is laser-clad onto the outer circumference of the cylinder. Step 2: The austenitic stainless steel layer is subjected to laser texturing treatment to make the surface roughness of the austenitic stainless steel layer greater than or equal to Ra3.2μm. For the first time, tungsten carbide-based thermal spray powder is used as raw material to spray an outer WC layer on the surface of the laser-textured austenitic stainless steel layer with supersonic flame. Step 3: Copper plating is performed on the inner bore of the cylinder to form a copper plating layer with a thickness of 0.015~0.030mm; Step 4: Using the tungsten carbide-based thermal spray powder as raw material again, spray the inner WC layer onto the surface of the copper plating layer with a supersonic flame; during the spraying process, by shortening the distance between the spray gun and the copper plating layer, the temperature and speed of the spraying flame are increased, causing the copper plating layer to undergo micro-melting, and then metallurgically bonded to the bonding surface of the inner WC layer.

[0006] Based on the above, in step four, the tungsten carbide-based thermal spray powder is 86WC-10Co-4Ni thermal spray powder, WC-10Co-4Cr thermal spray powder, or WC-12Co thermal spray powder. During the spraying of the inner WC layer, the distance between the supersonic flame spray gun nozzle and the copper plating layer surface is controlled at 270mm~290mm, the particle size of the tungsten carbide-based thermal spray powder is controlled to be less than 10μm, propane is used as the heat source, the workpiece rotation speed is 280~320RPM, the propane consumption is controlled at 8~10L / h, and the compressed air flow rate is controlled at 2000~2200m³ / h. 3The powder feeding rate is controlled at 2~5g / min, the spray gun moves at a speed of 1~3m / min along the cylinder axial direction, the powder speed is 1000~1200m / s, the thickness of a single spray coating is 1~3μm, and the total thickness of the inner WC layer is controlled at 30~50μm.

[0007] Based on the above, step four also includes providing a supersonic spray gun for internal holes, using the supersonic spray gun for internal holes to spray the inner WC layer onto the copper plating layer surface again with the tungsten carbide-based thermal spray powder as raw material using a supersonic flame. The supersonic spray gun for internal bores includes a right-angled housing, a combustion chamber inside the housing, a Laval nozzle located at the lower end of the combustion chamber, a spark plug located inside the combustion chamber, a compressed air passage, a propane passage, a compressed oxygen passage, a powder delivery passage connected to the combustion chamber via the same gas mixing nozzle at the inner end, and a water inlet and outlet located on the housing. The Laval nozzle includes a Laval nozzle converging section, a Laval nozzle throat, and a Laval nozzle expanding section. The ratio of the width 'a' at the outlet of the Laval nozzle converging section to the width 'b' at the inlet of the Laval nozzle expanding section is less than or equal to 0.5.

[0008] By designing the housing with a right-angle structure, the spray gun is ensured not to interfere with the cylinder, allowing it to penetrate deep into the cylinder for spraying the inner bore. Simultaneously, by increasing the oxygen ratio in the air-fuel mixture, the combustion chamber pressure and flame temperature are increased, resulting in micro-melting of the copper plating layer. This allows the copper plating layer in the inner bore to form a metallurgical bond with the sprayed inner WC coating, reducing the porosity of the inner WC coating and making it less prone to peeling off after impact.

[0009] Based on the above, in step two, when laser texturing the austenitic stainless steel layer, the laser output power is controlled to be 800~1500W, the pulse frequency is 20~40KHz, the scanning speed is 1000~3000mm / s, the line spacing is 0.08~0.15mm, the laser is positively focused, and the defocusing amount is 0.8~1.5mm.

[0010] By controlling the parameters during laser roughening, sharp edges caused by turning can be melted to avoid stress concentration; at the same time, the cutting fluid remaining on the surface due to the turning process is also removed by the laser to avoid affecting the bonding strength of the coating layer; ultimately, the roughness of the austenitic stainless steel layer can reach or exceed Ra3.2μm, achieving the level of sandblasting.

[0011] Based on the above, in step two, the tungsten carbide-based thermal spray powder is 86WC-10Co-4Ni thermal spray powder, WC-10Co-4Cr thermal spray powder, or WC-12Co thermal spray powder. When laser texturing the austenitic stainless steel layer, the laser output power is controlled to be 800~1500W, the pulse frequency is 20~40KHz, the scanning speed is 1000~3000mm / s, the line spacing is 0.08~0.15mm, the laser is positively focused, and the defocusing amount is 0.8~1.5mm. For the first time, tungsten carbide-based thermal spray powder was used as raw material to apply an outer WC layer to the surface of the laser-textured austenitic stainless steel layer using supersonic flame spraying. The temperature of the austenitic stainless steel layer was controlled to be less than 200°C, the particle size of the tungsten carbide-based thermal spray powder was 15-45 μm, kerosene was used as the heat source, the workpiece rotation speed was 280-320 RPM, propane consumption was controlled at 6-8 L / h, and compressed air flow rate was controlled at 1800-2000 m³ / h. 3 The powder feeding rate is controlled at 3~6g / min, the spray gun moves at a speed of 1~3m / min along the cylinder axis, the powder speed is 1100~1300m / s, the thickness of a single spray coating is 2~4μm, and the total thickness of the outer WC layer is controlled at 80~100μm.

[0012] By controlling the particle size of tungsten carbide-based thermal spray powder and various thermal spraying process parameters, it is possible to ensure that the tungsten carbide-based thermal spray powder melts sufficiently, and to ensure that the outer WC layer and the inner austenitic stainless steel layer are tightly bonded. This improves the bonding force between the outer WC layer and the austenitic stainless steel layer, thereby achieving the goal of using the austenitic stainless steel layer to provide high corrosion resistance and the outer WC layer to provide high hardness and high wear resistance.

[0013] Based on the above, in step three, when performing copper plating on the inner bore of the cylinder, the current density during copper plating is controlled to be 8~10A / dm. 2 The temperature of the immersion tank is 55~65℃, the electroplating time is 80~100min, and the roughness of the copper plating layer is Ra1.5~1.8μm.

[0014] By controlling the process parameters during copper plating, it is possible to ensure that the copper plating layer can firmly adhere to the surface of the inner hole, and also to ensure that the copper plating layer has a suitable plating thickness so that it can fully melt during the subsequent spraying of the inner WC layer, thereby improving the bonding force with the inner WC layer.

[0015] Based on the above, in step one, when laser cladding an austenitic stainless steel layer on the outer circle of the cylinder, the particle size of the Fe-Ni alloy powder is controlled to be 20μm~50μm, the laser power is 4000W~6000W, the powder feeding speed is 120g / min, the cladding speed is 600mm / min, the cladding layer thickness is 1000~1200μm, and the temperature after cladding is controlled at 150℃~200℃.

[0016] In other words, by controlling the parameters during laser cladding, it is possible to avoid excessive melting of the substrate due to high power and low powder feeding speed, which would dilute the alloying elements in the coating and reduce the corrosion resistance of the coating; and it is also possible to avoid the situation where the laser only melts the powder and not the substrate due to low laser power and high powder feeding speed, resulting in the coating and the substrate not forming a metallurgical bond.

[0017] Based on the above, the Fe-Ni alloy powder comprises the following elements by mass percentage: Mn 1.5%~1.8%, Cr 17%~18%, Ni 12%~13%, Mo 2%~2.5%, Cu 1.5%~2%, Nb 0.05%~0.15%, Ti 0.1%~0.15%, Zr 0.05%~0.1%, with the remainder being Fe.

[0018] By rationally controlling the composition of Fe-Ni alloy powder, an austenitic stainless steel layer can be obtained after laser cladding. At the same time, the resistance to pitting corrosion can be improved by increasing the Mo content, the strength after laser cladding can be improved by adding Cu and Nb, the ability to resist interlayer corrosion can be ensured by adding trace amounts of Ti, and the ability to resist interlayer corrosion can be ensured by adding trace amounts of Zr. The content of N and S in the cladding layer can be reduced, the number and size of inclusions can be reduced, and corrosion resistance can be further improved.

[0019] Based on the above, before step one, a processing production line is also provided. The processing production line includes a first guide rail and multiple second guide rails connected to the first guide rail, and several fixtures for clamping the cylinder and capable of moving along the first and second guide rails. The multiple second guide rails are respectively connected to the laser cladding station, the precision turning station, the supersonic flame spraying station, and the polishing station.

[0020] This ensures that the workpiece only needs to be clamped once in the laser cladding, precision turning, laser texturing, and thermal spraying processes, with a unified positioning reference, reducing errors and improving processing efficiency; no preheating is required before thermal spraying, and the residual heat from the laser texturing process can be used to reach the pretreatment temperature of 70~100℃ required for thermal spraying.

[0021] Based on the above, step one further includes precision turning of the austenitic stainless steel layer. During precision turning, the cutting speed is 90~100m / min, the depth of cut is 0.2~0.4mm, the feed rate is 0.15~0.2mm / r, the thickness of the austenitic stainless steel layer after precision turning is 750~950μm, and the surface roughness is 1.6~3.2μm.

[0022] In other words, by precision machining the austenitic stainless steel layer, defects on the surface of the austenitic stainless steel layer can be removed, ensuring the bonding between the austenitic stainless steel layer and the subsequent replacement of the outer WC layer.

[0023] The present invention also provides a hydraulic support cylinder barrel made by the above method, comprising a cylinder barrel body, an austenitic stainless steel layer fused to the outer surface of the cylinder barrel body, an outer WC layer sprayed on the surface of the austenitic stainless steel layer, a copper plating layer electroplated on the inner bore surface of the cylinder barrel body, and an inner WC layer sprayed on the surface of the copper plating layer.

[0024] This invention has outstanding substantive features and significant progress compared to the prior art. Specifically, the invention provides a method for spraying a high corrosion-resistant ceramic composite coating on the surface of a hydraulic support cylinder. On the one hand, by using laser cladding of high corrosion-resistant austenitic stainless steel on the outer circle of the cylinder, followed by laser roughening and then supersonic spraying of the outer WC layer, two layers with strong adhesion can be formed on the cylinder surface: the first layer provides high corrosion resistance, and the second layer provides high hardness and high wear resistance. At the same time, laser roughening can eliminate the existing sandblasting step and increase the surface roughness, thereby significantly improving the adhesion between the sprayed layer and the laser cladding layer.

[0025] On the other hand, this invention employs electroplating copper on the inner bore of the cylinder before applying a supersonic spray coating of the inner WC layer. Simultaneously, during the supersonic spray coating of the inner WC layer, a specialized supersonic spray gun and ultrafine powder are used, which shortens the distance between the spray gun and the workpiece surface, increases the spray flame temperature and velocity, and enables successful coating of the inner WC layer onto the surface of the hydraulic support cylinder bore within a relatively small working area. More importantly, the higher spray flame temperature and velocity allow for micro-melting of the copper plating layer in the inner bore, promoting the penetration of the micro-melted copper plating layer into the pores of the inner WC layer, thus minimizing the porosity of the inner WC layer and eliminating the need for the existing sealing agent application step. Furthermore, since the inner WC layer and the copper plating layer are metallurgically bonded, the corrosion resistance of the inner bore is improved, as is the impact resistance of the coating, ultimately meeting the requirements for corrosion resistance and wear resistance of the hydraulic support cylinder bore using water as the hydraulic medium.

[0026] Furthermore, when applying WC to the inner bore of the cylinder using supersonic spraying, by optimizing the spray gun structure, it can be ensured that the spray gun does not interfere with the cylinder. The spray gun can penetrate deep into the cylinder to spray the inner bore, which can increase the oxygen ratio in the air-fuel mixture, increase the combustion chamber pressure, and make the flame temperature higher than that of HVOF which uses pure oxygen for combustion. The WC powder velocity is also higher than that of HVAF, resulting in higher heat and pressure after the air-fuel mixture is ignited. In addition, the application of ultrafine powder improves the adhesion between the copper plating layer and the sprayed WC coating in the inner bore, reduces the porosity to below 0.5%, and makes it less likely to fall off after impact.

[0027] Furthermore, by designing a processing production line, the sequence of processing steps and equipment layout can be optimized, breaking down the barriers between laser cladding and supersonic spraying equipment. This allows for a single clamping operation to complete four processes: external cylindrical laser cladding, precision turning, supersonic spraying, and polishing. This avoids the impact of clamping errors and the time wasted due to repeated clamping. In other words, the workpiece only needs to be clamped once for the laser cladding, precision turning, laser texturing, and thermal spraying processes, ensuring a unified positioning benchmark, reducing errors, and improving processing efficiency. No preheating is required before thermal spraying; the residual heat from the laser texturing process is sufficient to achieve the required pretreatment temperature of 70-100°C for thermal spraying.

[0028] Furthermore, when preparing an austenitic stainless steel layer on the outer circumference using Fe-Ni alloy powder, this invention optimizes the chemical element composition of the laser cladding powder. On the one hand, it increases the Mo content to improve pitting corrosion resistance; on the other hand, it adds Cu and Nb to improve the strength after laser cladding; on the other hand, it adds trace amounts of Ti to ensure that the powder still has the ability to resist interlayer corrosion after high-temperature laser cladding; and on the other hand, it adds trace amounts of Zr to reduce the N and S content in the cladding layer and reduce the number and size of inclusions, thereby further improving corrosion resistance.

[0029] Furthermore, this invention also addresses the problems of poor corrosion resistance and unavoidable porosity of the inner WC layer by rationally controlling the process parameters during copper plating of the cylinder bore, utilizing copper's excellent ductility and low melting point. On the other hand, it ensures that the copper plating layer has a suitable thickness range, allowing for sufficient micro-melting of the copper layer during spraying and filling the pores within the inner WC layer, thereby ensuring a high density of the sprayed WC layer and eliminating the need for a sealing agent coating step.

[0030] Therefore, the present invention can improve the corrosion resistance and wear resistance of hydraulic support cylinder barrels that use water as the hydraulic medium, improve the bonding force between different anti-corrosion layers, reduce the porosity of the sprayed coating, and simplify the processing technology. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a hydraulic support cylinder structure provided by the present invention.

[0032] Figure 2 This is a schematic diagram of the machining process of the outer diameter of a hydraulic support cylinder provided by the present invention.

[0033] Figure 3 This is a schematic diagram of a supersonic spray gun structure for the inner bore of a hydraulic support cylinder provided by the present invention.

[0034] Figure 4 This is a microscope image of a falling ball impact test of a hydraulic support cylinder bore with only WC layer sprayed on.

[0035] Figure 5 This is a microscope image of a falling ball impact test of a hydraulic support cylinder bore coated with copper and then sprayed with an inner WC layer, provided by the present invention.

[0036] Figure 6 This is a graph showing the hardness test results of the composite coating on the outer circle of a hydraulic support cylinder provided by this invention.

[0037] Figure 7 This is a salt spray test result diagram of a hydraulic support cylinder with only an outer WC layer sprayed on its outer circumference, provided by the present invention.

[0038] Figure 8 This is a salt spray test result diagram of a composite coating sprayed on the outer circle of a hydraulic support cylinder provided by the present invention.

[0039] In the diagram: 1. Cylinder body; 2. Copper plating layer; 3. Inner WC layer; 4. Outer WC layer; 5. Austenitic stainless steel layer; 6. First guide rail; 7. Fixture; 8. Machining line; 9. Second guide rail; 10. Housing; 11. Combustion chamber; 12. Spark plug; 13. Gas mixing nozzle; 14. Compressed air passage; 15. Propane passage; 16. Water outlet; 17. Compressed oxygen passage; 18. Powder delivery passage; 19. Water inlet; 20. Laval nozzle converging section; 21. Laval nozzle throat; 22. Laval nozzle diverging section. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below through specific embodiments. Example 1

[0041] This embodiment provides a method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder, such as... Figure 1 , Figure 2 , Figure 3 As shown, the specific steps include: Design a processing production line 8: such as Figure 2 As shown, the processing line 8 includes a first guide rail 6 and multiple second guide rails 9 connected to the first guide rail 6, and several fixtures 7 for clamping the cylinder and moving along the first guide rail 6 and the second guide rails 9. That is, laser cladding, turning, and supersonic spraying use the same set of spindle box and tailstock. A single clamping operation can complete four processes: laser cladding, turning the outer diameter, laser roughening, supersonic spraying, and polishing. The clamping process is optimized from four times to one, avoiding positioning errors and time waste caused by multiple clamping operations, greatly improving processing efficiency. Simultaneously, the system controls the workpiece's moving speed and waiting time to set the cycle time between each process, ensuring that the workpiece surface temperature is 200℃ after laser cladding and 100℃ after turning the outer diameter, thus achieving workpiece preheating without an external heat source throughout the entire process.

[0042] Cylinder preparation: Select medium carbon alloy structural thick-walled seamless steel pipes of materials such as 27SiMn, 30CrMnSi or 30CrMo. After quenching and high-temperature tempering heat treatment, the surface hardness is 280-320HB. The inner hole is processed by rough turning, finish turning and scraping, etc., and the surface roughness is controlled to be ≤Ra0.4μm. The inner hole size is the final drawing size + (0.06~0.10)mm. The outer circle is processed by rough turning and finish turning, and the surface roughness is controlled to be ≤Ra6.3μm. The outer circle size is the final drawing size - (0.90~1.00)mm.

[0043] A laser-clad austenitic stainless steel layer was prepared on the outer circumference of the cylinder: the powder used was a high corrosion-resistant Fe-Ni alloy powder system, with Mn content controlled at 1.5%, Cr content controlled at 17%, Ni content controlled at 12%, Mo content controlled at 2%, Cu content controlled at 1.5%, Nb content controlled at 0.05%, Ti content controlled at 0.1%, Zr content controlled at 0.05%, powder particle size at 20μm, laser power at 4000W, powder feeding speed at 120g / min, cladding speed at 600mm / min, cladding layer thickness at 1000μm, and the workpiece surface temperature after cladding controlled at 150℃, forming an austenitic stainless steel layer on the outer circumference of the cylinder.

[0044] Turning the outer diameter: A small allowance is made for the laser-clad austenitic stainless steel layer. The cutting parameters selected are a cutting speed Vc of 100m / min, a depth of cut ap of 0.4mm, a feed rate f of 0.2mm / r, retaining 950μm of laser-clad coating, and controlling the surface roughness at Ra3.2μm.

[0045] Laser texturing: A nanosecond-level laser is used to texturize the austenitic stainless steel layer after machining the outer diameter. The laser output power is 800 kW, the pulse frequency is 20 kHz, the scanning speed is 1000 mm / s, the line spacing is 0.08 mm, the laser is in focus, and the defocusing amount is 0.8 mm. Laser texturing melts the sharp edges caused by machining, preventing stress concentration; residual cutting fluid from the machining process is also removed by the laser, preventing any impact on the bonding strength of the coating layer; the roughness of the cladding layer can reach Ra 3.2 μm, achieving the level of sandblasting.

[0046] Preparation of the outer WC layer by supersonic flame spraying: The outer WC layer was sprayed onto the surface of a laser-textured austenitic stainless steel layer using the HVAF process. During the spraying process, a thermal spraying powder with a chemical composition of 86WC-10Co-4Ni and a particle size of 45μm was used. Kerosene was used as the heat source, the workpiece rotation speed was 320RPM, the propane consumption was controlled at 8L / h, and the compressed air flow rate was controlled at 2000m³ / h. 3The powder feeding rate is controlled at 6 g / min, the spray gun moves at a speed of 3 m / min along the cylinder axis, the powder speed is 1300 m / s, the thickness of a single spray coating is 4 μm, and the total thickness is controlled at 80 μm.

[0047] Cylinder bore copper plating: The inner bore is copper plated, with the current density maintained at 10A / dm² during the plating process. 2 The temperature of the immersion tank was maintained at 65℃, the electroplating time was 100min, the copper plating layer thickness was 0.030mm, and the roughness of the copper plating layer was controlled at Ra1.8μm.

[0048] Preparation of the inner WC layer by supersonic flame spraying in cylinder bores: A dedicated supersonic spray gun for the inner bores was designed, and the inner bores were sprayed using this specialized supersonic flame spray gun. During the spraying process, the workpiece spraying temperature was controlled at 200℃, using thermal spraying powder with a chemical composition of 86WC-10Co-4Ni and a particle size of less than 10μm, the spray distance was controlled at 280mm, propane was used as the heat source, the workpiece rotation speed was 320RPM, the propane consumption was controlled at 10L / h, and the compressed air flow rate was controlled at 2200m³ / h. 3 The powder feeding rate is controlled at 5 g / min, the spray gun moves at a speed of 3 m / min along the cylinder axis, the powder speed reaches 1200 m / s, the thickness of a single spray coating is 3 μm, and the total thickness is controlled at 50 μm.

[0049] Specifically, such as Figure 3 As shown, the system includes a right-angled housing 10, a combustion chamber 11 inside the housing 10, a Laval nozzle located at the lower end of the combustion chamber 11, a spark plug 12 located within the combustion chamber 11, a compressed air passage 14, a propane passage 15, a compressed oxygen passage 17, a pulverized coal delivery passage 18 connected to the Laval nozzle, and a water inlet 19 and an outlet 16 located on the housing 10. The Laval nozzle includes a converging section 20, a throat 21, and an expanding section 22. The ratio of the width 'a' at the outlet of the converging section 20 to the width 'b' at the inlet of the expanding section 22 is less than or equal to 0.5. In other words, this optimized supersonic spray gun can use two types of combustion-supporting gases: compressed air as the primary combustion-supporting gas and compressed oxygen as the secondary combustion-supporting gas. Increasing the oxygen content in the mixture generates higher heat and pressure upon ignition, thereby increasing the flame speed and achieving micro-melting of the copper plating layer. Simultaneously, by setting the nozzle direction perpendicular to the air inlet and the flame radially parallel to the cylinder, the spray gun does not interfere with the cylinder, allowing it to penetrate deep into the cylinder for internal coating.

[0050] Polishing: After the coating of the cylinder outer circle and cylinder inner hole is completed, polishing is performed uniformly. The cylinder inner hole is polished using diamond paste and a flexible polishing wheel, while the cylinder outer circle is polished using diamond abrasive belt. Example 2

[0051] This embodiment provides a method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder. The main difference from Embodiment 1 is that in this embodiment, during the laser cladding of the austenitic stainless steel layer on the outer circumference of the cylinder: the Fe-Ni alloy powder system's highly corrosion-resistant material contains 1.8% Mn, 18% Cr, 13% Ni, 2.5% Mo, 2% Cu, 0.15% Nb, 0.15% Ti, and 0.1% Zr; the powder particle size is 50 μm; the laser power is 6000 W; the powder feeding speed is 120 g / min; the cladding speed is 600 mm / min; the cladding layer thickness is 1200 μm; and the workpiece surface temperature is controlled at 200℃ after cladding. An austenitic stainless steel layer is thus formed on the outer circumference of the cylinder. Example 3

[0052] This embodiment provides a method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder. The main difference from Embodiment 1 is that in this embodiment: When preparing the inner WC layer by supersonic flame spraying in the cylinder bore, the distance between the supersonic flame spraying nozzle and the copper plating surface is controlled at 270 mm. The particle size of the 86WC-10Co-4Ni thermal spraying powder is controlled to be less than 10 μm. Propane is used as the heat source, the workpiece rotation speed is 280 RPM, the propane consumption is controlled at 8 L / h, and the compressed air flow rate is controlled at 2000 m³ / h. 3 The powder feeding rate is controlled at 2g / min, the spray gun moves at a speed of 1m / min along the cylinder axial direction, the powder speed is 1000m / s, the thickness of a single spray coating is 1μm, and the total thickness is controlled at 50μm, so that the copper plating layer and the inner WC layer are fused and metallurgically bonded at the interface. Example 4

[0053] This embodiment provides a method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder. The main difference from Embodiment 1 is that in this embodiment: The laser texturing process includes: using a nanosecond-level laser to texturize the austenitic stainless steel layer after machining the outer diameter. The laser output power is 1500W, the pulse frequency is 40kHz, the scanning speed is 3000mm / s, the line spacing is 0.15mm, the laser is in focus, and the defocusing amount is 1.5mm. WC-10Co-4Cr thermal spray powder is selected. Example 5

[0054] This embodiment 5 provides a hydraulic support cylinder barrel manufactured using the method described in embodiment 1, such as... Figure 1 The cylinder body 1 includes an austenitic stainless steel layer 5 fused to the outer surface of the cylinder body 1, an outer WC layer 4 sprayed on the surface of the austenitic stainless steel layer 5, a copper plating layer 2 electroplated on the inner surface of the cylinder body 1, and an inner WC layer 3 sprayed on the surface of the copper plating layer 2.

[0055] To compare with the embodiments of this case, the following sets of comparative examples were designed to prove that this case is not a simple combination of two processing methods, but requires special processing. Comparative Example 1: Increasing the nozzle distance of the supersonic flame spraying gun reduces the spraying temperature.

[0056] The difference between this comparative example and Example 1 is that when preparing the inner WC layer by supersonic flame spraying in the cylinder bore, the distance between the nozzle of the supersonic flame spraying gun and the surface of the copper plating layer is 600mm, so that the spraying temperature is lower than that of Example 1. Comparative Example 2 omits the laser texturing step.

[0057] The difference between this comparative example and Example 1 is that the laser texturing step was omitted when preparing the outer WC layer by supersonic flame spraying. Comparative Example 3 simultaneously omits the laser texturing step and reduces the spraying temperature.

[0058] The difference between this comparative example and Example 1 is that the laser texturing step is omitted when preparing the outer WC layer by supersonic flame spraying. When preparing the inner WC layer by supersonic flame spraying in the cylinder bore, the distance between the supersonic flame spraying nozzle and the copper plating surface is 600 mm, and the spraying temperature is lower than that of Example 1. Comparative Example 4: Only the outer circle is laser-clad with austenitic stainless steel and the inner hole is copper-plated.

[0059] The difference between this comparative example and Example 1 is that the outer circumference of the cylinder is only laser-clad with an austenitic stainless steel layer, and the outer WC layer is not applied using supersonic flame spraying. The inner bore of the cylinder is only copper-plated, and the outer WC layer is not applied using supersonic flame spraying. Comparative Example 5: Only the outer circle is laser-clad with martensitic stainless steel and the inner hole is copper-plated.

[0060] The difference between this comparative example and Example 1 is that martensitic stainless steel powder is used instead of Fe-Ni alloy powder. Only a martensitic stainless steel layer is laser-clad on the outer circumference of the cylinder, and the outer WC layer is not applied using supersonic flame spraying. The inner bore of the cylinder is only copper-plated, and the outer WC layer is not applied using supersonic flame spraying.

[0061] In Comparative Example 5, the composition of Fe-Ni alloy powder was changed to transform the laser cladding powder into martensitic stainless steel laser cladding powder, and a martensitic stainless steel coating was finally prepared on the outer circle to demonstrate the influence of the type of stainless steel coating on the corrosion resistance. Comparative Example 6: Laser cladding of austenitic stainless steel layer on the outer circle and arc fusion of copper-tin alloy on the inner hole only.

[0062] The difference between this comparative example and Example 1 is that the outer circumference of the cylinder is only laser-clad with an austenitic stainless steel layer, and no longer undergoes supersonic flame spraying of the outer WC layer. The inner bore of the cylinder is only treated with arc melting of copper-tin alloy, and no longer undergoes supersonic flame spraying of the outer WC layer. Comparative Example 7: WC was applied only to the outer circumference and the inner hole, without a base layer.

[0063] The difference between this comparative example and Example 1 is that the outer circumference of the cylinder is not laser-clad with an austenitic stainless steel layer; instead, the outer WC layer is directly sprayed onto the outer circumference of the cylinder using a supersonic flame. The inner bore of the cylinder is not copper-plated; instead, the outer WC layer is directly sprayed onto the inner bore using a supersonic flame.

[0064] Detection

[0065] The outer diameter and inner bore of the cylinder prepared in Example 1 and Comparative Examples 1 to 7 of this invention were subjected to hardness, copper-accelerated acetic acid salt spray test, and 2000-cycle type test scratch test results. The specific test results are shown in Table 1 below.

[0066] Table 1. Detection results of each embodiment Example 1 Cylinder bore HV1200-1400 ＞720 No scratches Example 1 cylinder outer circle HV1200-1400 ＞720 No scratches Example 2 Cylinder bore HV1200-1400 ＞720 No scratches Example 2 cylinder outer circle HV1200-1400 ＞720 No scratches Example 3 Cylinder bore HV1200-1400 ＞720 No scratches Example 3 cylinder outer circle HV1200-1400 ＞720 No scratches Example 4 Cylinder bore HV1200-1400 ＞720 No scratches Example 4 cylinder outer circle HV1200-1400 ＞720 No scratches Comparative Example 1 Cylinder bore HV1100-1300 360 No scratches Comparative Example 1 cylinder outer circle HV1200-1400 ＞720 Coating peeling off in chunks Comparative Example 2 Cylinder bore HV1200-1400 ＞720 Coating peeling off in chunks Comparative Example 2 cylinder outer circle HV1200-1400 ＞720 No scratches Comparative Example 3 Cylinder bore HV1200-1400 360 Coating peeling off in chunks Comparative Example 3 cylinder outer circle HV1100-1300 ＞720 Coating peeling off in chunks Comparative Example 4 Cylinder bore HV180-200 72 Numerous scratches Comparative Example 4 cylinder outer circle HV200-250 ＞720 Numerous scratches Comparative Example 5 Cylinder bore HV180-200 72 Numerous scratches Comparative Example 5 cylinder outer circle HV500-570 240 Minor or slight scratches Comparative Example 6 Cylinder bore HV200-250 240 Numerous scratches Comparative Example 6 cylinder outer circle HV200-250 ＞720 Numerous scratches Comparative Example 7 Cylinder bore HV1200-1400 240 No scratches Comparative Example 7 cylinder outer circle HV1200-1400 240 No scratches In Table 1, the result of the copper-accelerated acetic acid salt spray test is greater than 720 hours, which means that after the test sample was sprayed continuously for 720 hours (30 days) in accordance with the national standard GB / T10125, no corrosion phenomenon appeared on the sample surface.

[0067] From Table 1 and Figure 6 , Figure 7 and Figure 8 As can be seen, the hydraulic support cylinder prepared by this invention exhibits high hardness, good wear resistance, and strong corrosion resistance in both its inner bore and outer circumference. Furthermore, it can be observed that the method of laser cladding of highly corrosion-resistant austenitic stainless steel followed by supersonic spraying of an outer WC layer on the outer circumference of the cylinder utilizes the high corrosion resistance provided by the austenitic stainless steel and the high hardness and wear resistance provided by the outer WC coating. Conversely, the method of electroplating copper followed by supersonic spraying of an inner WC layer in the inner bore achieves micro-melting of the copper plating layer, reducing the porosity of the supersonic sprayed coating, improving corrosion resistance, and enhancing the coating's impact resistance.

[0068] However, if the texturing process is omitted, the spraying temperature is lowered, or different materials are used, problems such as insufficient hardness, poor corrosion resistance, and poor wear resistance will occur.

[0069] Meanwhile, a falling ball impact test was conducted on the cylinder bore prepared in Example 1 and Comparative Example 7. In the falling ball test, a 40mm diameter steel ball was dropped from a height of 970mm to impact the surface of the cylinder bore. The test results are as follows: Figure 4 and Figure 5 As shown in the figure, it can be seen that the cylinder bore prepared in Comparative Example 7 developed obvious cracks after the ball impact test, and the crack width was relatively large. In contrast, the cylinder bore prepared in Example 1 of this invention showed smaller cracks.

[0070] In summary, the methods employed in this case—laser cladding of highly corrosion-resistant austenitic stainless steel on the outer circumference of the cylinder followed by supersonic spraying of the outer WC layer, electroplating of copper on the inner bore of the cylinder followed by supersonic spraying of the inner WC layer, and the use of a specially designed supersonic flame spraying—have a synergistic effect. Only by combining these methods can the requirements for corrosion resistance and wear resistance of the cylinder barrel of a hydraulic support system using water as the hydraulic medium be met. This approach also aims to improve the bonding strength between different anti-corrosion layers, reduce the porosity of the sprayed coating, and simplify the processing technology.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for spraying a highly corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder, characterized in that: Includes the following steps: Step 1: Using Fe-Ni alloy powder as raw material, an austenitic stainless steel layer is laser-clad onto the outer circumference of the cylinder. Step 2: The austenitic stainless steel layer is subjected to laser texturing treatment to make the surface roughness of the austenitic stainless steel layer greater than or equal to Ra3.2μm. For the first time, tungsten carbide-based thermal spray powder is used as raw material to spray an outer WC layer on the surface of the laser-textured austenitic stainless steel layer with supersonic flame. Step 3: Copper plating is performed on the inner bore of the cylinder to form a copper plating layer with a thickness of 0.015~0.030mm; Step 4: Using the tungsten carbide-based thermal spray powder as raw material again, spray the inner WC layer onto the surface of the copper plating layer with a supersonic flame; during the spraying process, by shortening the distance between the spray gun and the copper plating layer, the temperature and speed of the spraying flame are increased, causing the copper plating layer to undergo micro-melting, and then metallurgically bonded to the bonding surface of the inner WC layer.

2. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 1, characterized in that: In step four, the tungsten carbide-based thermal spray powder is 86WC-10Co-4Ni thermal spray powder, WC-10Co-4Cr thermal spray powder, or WC-12Co thermal spray powder. During the spraying of the inner WC layer, the distance between the supersonic flame spray gun nozzle and the copper plating layer surface is controlled at 270mm~290mm, the particle size of the tungsten carbide-based thermal spray powder is controlled to be less than 10μm, propane is used as the heat source, the workpiece rotation speed is 280~320RPM, the propane consumption is controlled at 8~10L / h, and the compressed air flow rate is controlled at 2000~2200m³ / h. 3 The powder feeding rate is controlled at 2~5g / min, the spray gun moves at a speed of 1~3m / min along the cylinder axial direction, the powder speed is 1000~1200m / s, the thickness of a single spray coating is 1~3μm, and the total thickness of the inner WC layer is controlled at 30~50μm.

3. A method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 1 or 2, characterized in that: Step four also includes providing a supersonic spray gun for internal holes, using the supersonic spray gun for internal holes to spray the inner WC layer onto the copper plating layer surface with supersonic flame again using the tungsten carbide-based thermal spray powder as raw material. The supersonic spray gun with an inner bore includes a right-angled housing (10), a combustion chamber (11) inside the housing (10), a Laval nozzle located at the lower end of the combustion chamber (11), a spark plug (12) located in the combustion chamber (11), a compressed air passage (14), a propane passage (15), a compressed oxygen passage (17), a powder delivery passage (18) connected to the Laval nozzle, and a water inlet (19) and a water outlet (16) located on the housing (10). The Laval nozzle includes a Laval nozzle converging section (20), a Laval nozzle throat (21), and a Laval nozzle expanding section (22). The ratio of the width a at the outlet of the Laval nozzle converging section (20) to the width b at the inlet of the Laval nozzle expanding section (22) is less than or equal to 0.

5.

4. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 1, characterized in that: In step two, the tungsten carbide-based thermal spray powder is 86WC-10Co-4Ni thermal spray powder, WC-10Co-4Cr thermal spray powder, or WC-12Co thermal spray powder. When laser texturing the austenitic stainless steel layer, the laser output power is controlled to be 800~1500W, the pulse frequency is 20~40KHz, the scanning speed is 1000~3000mm / s, the line spacing is 0.08~0.15mm, the laser is positively focused, and the defocusing amount is 0.8~1.5mm. For the first time, tungsten carbide-based thermal spray powder was used as raw material to apply an outer WC layer to the surface of the laser-textured austenitic stainless steel layer using supersonic flame spraying. The temperature of the austenitic stainless steel layer was controlled to be less than 200°C, the particle size of the tungsten carbide-based thermal spray powder was 15-45 μm, kerosene was used as the heat source, the workpiece rotation speed was 280-320 RPM, propane consumption was controlled at 6-8 L / h, and compressed air flow rate was controlled at 1800-2000 m³ / h. 3 The powder feeding rate is controlled at 3~6g / min, the spray gun moves at a speed of 1~3m / min along the cylinder axis, the powder speed is 1100~1300m / s, the thickness of a single spray coating is 2~4μm, and the total thickness of the outer WC layer is controlled at 80~100μm.

5. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 4, characterized in that: In step three, when copper plating the inner bore of the cylinder, the current density during copper plating is controlled to be 8~10A / dm. 2 The temperature of the immersion tank is 55~65℃, the electroplating time is 80~100min, and the roughness of the copper plating layer is Ra1.5~1.8μm.

6. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 5, characterized in that: In step one, when laser cladding an austenitic stainless steel layer on the outer circumference of the cylinder, the Fe-Ni alloy powder particle size is controlled to be 20μm~50μm, the laser power is 4000W~6000W, the powder feeding speed is 120g / min, the cladding speed is 600mm / min, the cladding layer thickness is 1000~1200μm, and the temperature after cladding is controlled to be 150℃~200℃.

7. A method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 6, characterized in that: The Fe-Ni alloy powder comprises the following elements by mass percentage: Mn 1.5%~1.8%, Cr 17%~18%, Ni 12%~13%, Mo 2%~2.5%, Cu 1.5%~2%, Nb 0.05%~0.15%, Ti 0.1%~0.15%, Zr 0.05%~0.1%, with the remainder being Fe.

8. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 7, characterized in that: Before step one, a processing line (8) is provided. The processing line (8) includes a first guide rail (6) and a plurality of second guide rails (6) connected to the first guide rail (6), and a plurality of clamps (7) for holding the cylinder and capable of moving along the first guide rail (6) and the second guide rail (9). The plurality of second guide rails (6) are respectively connected to the laser cladding station, the precision turning station, the supersonic flame spraying station and the polishing station.

9. The method for spraying a high corrosion-resistant ceramic composite coating onto the surface of a hydraulic support cylinder according to claim 8, characterized in that: Step one further includes precision turning the austenitic stainless steel layer. During precision turning, the cutting speed is 90~100m / min, the depth of cut is 0.2~0.4mm, the feed rate is 0.15~0.2mm / r, the thickness of the austenitic stainless steel layer after precision turning is 750~950μm, and the surface roughness is 1.6~3.2μm.

10. A hydraulic support cylinder barrel manufactured using the method described in any one of claims 1 to 9, characterized in that: It includes a cylinder body (1), an austenitic stainless steel layer (5) fused to the outer surface of the cylinder body (1), an outer WC layer (4) sprayed on the surface of the austenitic stainless steel layer (5), a copper plating layer (2) electroplated on the inner surface of the cylinder body (1), and an inner WC layer (3) sprayed on the surface of the copper plating layer (2).

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