A new type of thermal spraying water seal bushing and application thereof

Abstract

The application provides a thermal spraying water seal bush, which comprises a special multi-thread on the surface and a composite layer sprayed on the surface of the water seal bush. The raw material of the composite layer comprises 9-11% of cobalt, 3.5-4.5% of chromium, 0.01-0.5% of iron and the balance of carbon-containing tungsten, wherein the mass percentage of carbon in the carbon-containing tungsten is 5-10%. The water seal bush coated with the composite layer has high Vickers hardness, which can effectively improve the corrosion resistance, impact resistance and service life of the slurry pump and ensure the normal operation of the slurry pump water sealing system.

Description

Technical Field

[0001] This invention relates to the field of metal surface coatings, particularly to the field of CO3C17 / 40, and more specifically to a novel thermal spray water seal bushing. Background Technology

[0002] The primary function of a mud pump sealing system is to protect the mud pump assembly. A certain amount of seawater is injected into the pump shaft seal to ensure that the pressure at the seal is higher than the pump's operating pressure. This allows only seawater to enter the pump, preventing mud slurry from entering the seal. If mud slurry enters the pump shaft seal, it will cause rapid wear on both the seal and the pump shaft, leading to leakage and malfunction. The sealing system ensures the normal operation of the mud pump, balances the pressure inside the pump chamber, and affects the efficiency and output of the dredging vessel as a whole. The system also typically provides water lubrication and flushing to the pump shaft seal. The water seal bushing, a core component of the system, rotates at high speed with the pump shaft during operation. Traditional high-chromium cast iron bushings wear quickly, corrode rapidly, and lose surface smoothness, leading to frequent replacements of the sealing rubber rings and bushings, significantly impacting the continuity and efficiency of dredging operations.

[0003] Existing technology CN109898046A discloses a wear-resistant coating for submerged roller bushings, its preparation method, and its application. This wear-resistant coating mainly comprises titanium dioxide powder, carbon, nickel, tungsten, and graphite oxide. The preparation method includes uniformly mixing the above raw materials to obtain TiC-Fe ceramic powder, rough machining, thermal spraying, vacuum sintering, and fine machining. This wear-resistant coating reduces zinc liquid permeability, improves resistance to zinc liquid penetration corrosion and adhesive corrosion, and has high microhardness, thus improving the wear resistance of the bushing. Existing technology CN115700291N discloses a method for preparing a highly corrosion-resistant and wear-resistant composite coating for zinc pot roller bushings. This composite coating comprises a cobalt-based alloy, which includes elements such as nickel, chromium, tungsten, cobalt, and silicon. It is processed using plasma cladding or thermal spraying technology. The preparation method provided by this invention can further improve the productivity and product quality of hot-drying product production lines. However, the aforementioned bushing coating cannot be applied to mud pump water seal bushings. Water seal bushings are generally required to be able to work underwater for extended periods to ensure the normal operation of the mud pump sealing system. Furthermore, if the Vickers hardness of the bushing is not up to standard or the surface finish of the bushing is insufficient, it is prone to oxidation and corrosion underwater, requiring frequent bushing replacements. This will have a significant impact on the normal operation of the ship and pose a considerable safety hazard. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a thermally sprayed water seal bushing, which includes a specially designed multi-threaded design and has a composite layer sprayed onto its surface.

[0005] Preferably, the base material of the water seal bushing includes one of Q355B steel, Q355C steel, and Q355D steel.

[0006] Preferably, the raw materials for preparing the composite layer include carbon-containing tungsten, cobalt, chromium, and iron.

[0007] More preferably, the raw materials for preparing the composite layer include, by mass percentage, 1-15% cobalt, 1.0-10% chromium, 0.01-5% iron, and the balance being carbon-containing tungsten, wherein the carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5-10%.

[0008] More preferably, the raw materials for preparing the composite layer include, by mass percentage, 9-11% cobalt, 3.5-4.5% chromium, 0.01-0.5% iron, and the balance being carbon-containing tungsten, wherein the carbon-containing tungsten contains 6-9% carbon by mass.

[0009] Preferably, the multi-threaded structure includes at least one or more of five-threaded, six-threaded, seven-threaded, eight-threaded, and ten-threaded types.

[0010] Preferably, the six-thread thread has a thread pitch of 10-40mm, a lead of 60-240mm, and a thread depth of 0.1-3mm.

[0011] More preferably, the six-thread thread has a thread pitch of 20-25mm, a lead of 120-150mm, and a thread depth of 0.8-1.5mm.

[0012] Preferably, the water seal bushing needs to be finely ground after the composite layer is sprayed, and the surface finish of the fine grinding is above 0.4μm.

[0013] Preferably, the spraying of the water seal bushing includes at least the following steps:

[0014] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7-0.8MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0015] S2. Within 2 hours after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF (High-Speed ​​Fire) spray gun. The preheating temperature is 110-150℃ and the preheating time is 10-60 minutes.

[0016] S3. Allow the workpiece obtained in step S2 to cool naturally to 40-80℃. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface should be 300-400mm. The oxygen flow rate should be 30-50 liters / hour, and the fuel flow rate should be 20-40 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed should be 60-100 grams / minute, and the thickness of the base material spraying should be 0.1-0.3mm.

[0017] S4. Allow the workpiece obtained in step S3 to cool naturally to 40-80℃. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the gun head and the workpiece surface is 300-400mm. The oxygen flow rate is 30-50 liters / hour, and the fuel flow rate is 20-40 liters / hour. The powder feeder completes the powder feeding of the composite layer material at a speed of 80-120 grams / minute. The coating thickness of the composite layer material is 0.4-0.7mm. During the spraying process, the workpiece temperature is controlled below 165℃. After the spraying is completed, allow it to cool naturally to room temperature.

[0018] Preferably, the sandblasting material is 16# white corundum powder.

[0019] Preferably, the underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0020] Preferably, the sum of the thickness of the composite layer coating and the thickness of the underlying material coating is 0.7-1.0 mm.

[0021] Preferably, the fine grinding includes at least the following steps:

[0022] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0-0.02mm.

[0023] L2. The surface coating of the workpiece treated by step L1 is ground with 400-mesh diamond, and the surface finish is above 0.4μm.

[0024] This invention uses specific alloy materials to prepare the composite layer of the water seal bushing, including tungsten carbide, cobalt, chromium, and iron, which can effectively improve the corrosion resistance and wear resistance of the bushing. The most abundant substance in the composite layer of this invention is tungsten carbide, and it is combined with several other metals. The mass percentage of carbon in the tungsten carbide is limited, which can further enhance the physical and mechanical strength of the composite layer and give the bushing a high Vickers hardness. In the composite layer, cobalt enables the bushing to possess a series of excellent properties such as high strength, high hardness, and high wear resistance. However, as the cobalt content exceeds a certain amount, the composite layer's hardness decreases, wear resistance decreases, bending strength increases, compressive strength decreases, thermal expansion coefficient increases, thermal conductivity decreases, elastic modulus and rigidity modulus decrease, and fatigue strength limit increases. The bending strength of tungsten steel increases with increasing cobalt content, but when the cobalt content is greater than 15%, the bending strength no longer increases with increasing cobalt content, but instead decreases slightly. Chromium not only improves the metal's corrosion resistance and hardness, but also improves its oxidation resistance. However, in actual research, the inventors found that if the chromium content in the water seal bushing composite layer is too high, although it can improve the hardness of the composite layer, it will damage the toughness of the composite layer. During the preparation process or in actual use, the composite layer will crack and break under certain external forces, seriously affecting its service life and causing great impact on the safety of the ship. This invention employs a specially designed multi-threaded design on the bushing surface, with specific limitations on the thread pitch, depth, and lead. These limitations ensure that the pressure inside and outside the pump remains constant during water intake and discharge, further extending the bushing's service life. Without the multi-threaded design, the pressure difference between the inside and outside of the pump during intake and discharge can damage the bushing if the pressure difference reaches a critical value. This invention also limits the thickness of the composite layer and the base material. When the combined thickness of the composite layer and the base material is less than 0.7 mm, it is too thin to effectively protect the water seal bushing, leading to cracking of the composite layer during prolonged continuous operation. While a combined thickness greater than 1.0 mm effectively protects the bushing, the bushing rotates at high speed with the pump shaft during actual ship operation. Excessive thickness can cause occasional jamming or a significant reduction in rotation speed. Furthermore, excessive thickness can result in more uneven particle size distribution. Additionally, thicker composite and base layers increase production costs and extend the coating cycle. In addition, the specific supersonic flame spraying method used in this invention can tightly bond the bottom sandblasting, the bottom material, and the composite layer material in sequence, making the surface of the water seal bushing more robust and more corrosion resistant.

[0025] Beneficial effects

[0026] (1) In this invention, the composite layer comprises 1-15% cobalt, 1.0-10% chromium, and 0.01-5% iron by mass percentage, with the balance being carbon-containing tungsten, wherein the carbon content in the carbon-containing tungsten is 5-10% by mass. The composite layer can be effectively bonded to the surface of the substrate after sandblasting and spraying of the base material, has high Vickers hardness, can effectively improve the corrosion resistance and impact resistance of the mud pump, ensure the normal operation of the mud pump sealing system, and has a long service life.

[0027] (2) In this invention, by setting a special multi-threaded surface on the substrate, the pressure difference during the water inlet and outlet process can be avoided when the mud pump is working normally, so that the pressure inside and outside the pump is balanced, effectively protecting the normal operation of the mud pump.

[0028] (3) By limiting the sum of the thickness of the composite layer material spray coating and the thickness of the bottom layer material spray coating, the present invention can not only effectively protect the bushing, but also avoid the problem of the mud pump sealing system not running smoothly due to the excessive thickness of the composite layer material spray coating and the bottom layer material spray coating, and can further reduce the spraying production cost.

[0029] (4) The present invention uses a specific supersonic flame spraying method to tightly bond the sandblasting, the base material and the composite layer material to the surface of the substrate in sequence, making the surface of the water seal bushing more solid, more corrosion resistant and longer service life.

[0030] (5) After the composite layer material is sprayed, the composite layer is also finely ground to make the surface finish of the composite layer above 0.4μm, which can effectively ensure that the water seal bushing operates normally in actual work and has a longer service life. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a six-threaded screw thread. Detailed Implementation

[0032] Example 1

[0033] The first aspect of this embodiment provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0034] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 10% cobalt, 4% chromium, 0.4% iron, and 85.6% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The thread pitch of the six-thread is 26mm, the lead of the six-thread is 156mm, and the thread depth of the six-thread is 1mm. The composite layer needs to be further finely ground, and the surface finish of the fine grinding is 0.5μm.

[0035] The spraying of the water seal bushing includes at least the following steps:

[0036] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0037] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 120°C for 30 minutes.

[0038] S3. Allow the workpiece obtained in step S2 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour and the fuel flow rate is 32 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed is 80 grams / minute and the thickness of the base material is 0.15mm.

[0039] S4. Allow the workpiece obtained in step S3 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the gun head and the workpiece surface is 380mm. The oxygen flow rate is 32 liters / hour, the fuel flow rate is 30 liters / hour, and the powder feeder completes the powder feeding of the composite layer material at a feeding speed of 100 grams / minute. The composite layer thickness is 0.6mm. During the spraying process, the workpiece temperature is controlled at 160°C. After the spraying is completed, allow it to cool naturally to room temperature of 25°C.

[0040] The blasting material is 16# white fused alumina powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0041] The underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0042] The carbon-containing tungsten was purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0043] The fine grinding includes the following steps:

[0044] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0.01mm.

[0045] L2. The surface coating of the workpiece treated in step L1 is ground with 400-mesh diamond, and the surface finish is 0.5μm.

[0046] The second aspect of this embodiment provides an application of a thermally sprayed water seal bushing, which is used in the mud pump sealing system of a ship to protect the mud pump device.

[0047] The six-thread structure described above is as follows: Figure 1 As shown.

[0048] Example 2

[0049] The first aspect of this embodiment provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0050] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 9% cobalt, 3.5% chromium, 0.25% iron, and 87.25% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The thread pitch of the six-thread is 26mm, the lead of the six-thread is 156mm, and the thread depth of the six-thread is 1mm. The composite layer needs to be further finely ground, and the surface finish of the fine grinding is 0.5μm.

[0051] The spraying of the water seal bushing includes at least the following steps:

[0052] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0053] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 120°C for 30 minutes.

[0054] S3. Allow the workpiece obtained in step S2 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour and the fuel flow rate is 32 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed is 80 grams / minute and the thickness of the base material is 0.2mm.

[0055] S4. Allow the workpiece obtained in step S3 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour, the fuel flow rate is 32 liters / hour, and the powder feeder completes the powder feeding of the composite layer material at a speed of 100 grams / minute. The composite layer thickness is 0.6mm, and the workpiece temperature is controlled at 160°C. After spraying, allow it to cool naturally to room temperature of 25°C.

[0056] The blasting material is 16# white fused alumina powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0057] The underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0058] The carbon-containing tungsten was purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0059] The fine grinding includes the following steps:

[0060] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0.01mm.

[0061] L2. The surface coating of the workpiece treated in step L1 is ground with 400-mesh diamond, and the surface finish is 0.6μm.

[0062] Example 3

[0063] The first aspect of this embodiment provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0064] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 11% cobalt, 4.5% chromium, 0.3% iron, and 84.2% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The thickness of the composite layer is 0.80 mm. The thread pitch of the six-thread is 26 mm, the lead of the six-thread is 156 mm, and the thread depth of the six-thread is 1 mm. The composite layer needs to be further finely ground, and the surface finish of the fine grinding is 0.5 μm.

[0065] The spraying of the water seal bushing includes at least the following steps:

[0066] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0067] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 120°C for 30 minutes.

[0068] S3. Allow the workpiece obtained in step S2 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour and the fuel flow rate is 32 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed is 80 grams / minute and the thickness of the base material is 0.15mm.

[0069] S4. Allow the workpiece obtained in step S3 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the spray gun and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour, the fuel flow rate is 32 liters / hour, and the powder feeder completes the powder feeding of the composite layer material at a speed of 100 grams / minute. The composite layer thickness is 0.55mm, and the workpiece temperature is controlled at 160°C. After spraying, allow it to cool naturally to room temperature of 25°C.

[0070] The blasting material is 16# white fused alumina powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0071] The underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0072] The carbon-containing tungsten was purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0073] The fine grinding includes the following steps:

[0074] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0.01mm.

[0075] L2. The surface coating of the workpiece treated in step L1 is ground with 400-mesh diamond, and the surface finish is 0.6μm.

[0076] Comparative Example 1

[0077] The first aspect of this comparative example provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0078] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 20% cobalt, 12% chromium, 0.6% iron, and 67.4% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The thread pitch of the six-thread is 26mm, the lead of the six-thread is 156mm, and the thread depth of the six-thread is 1mm. The composite layer needs to be further finely ground, and the surface finish of the fine grinding is 0.5μm.

[0079] The spraying of the water seal bushing includes at least the following steps:

[0080] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0081] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 120°C for 30 minutes.

[0082] S3. Allow the workpiece obtained in step S2 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour and the fuel flow rate is 32 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed is 80 grams / minute and the thickness of the base material is 0.2mm.

[0083] S4. Allow the workpiece obtained in step S3 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour, the fuel flow rate is 32 liters / hour, and the powder feeder completes the powder feeding of the composite layer material at a feeding speed of 100 grams / minute. The composite layer thickness is 0.5mm, and the workpiece temperature is controlled at 160°C. After spraying, allow it to cool naturally to room temperature of 25°C.

[0084] The blasting material is 16# white fused alumina powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0085] The underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0086] The carbon-containing tungsten was purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0087] The fine grinding includes the following steps:

[0088] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0.01mm.

[0089] L2. The surface coating of the workpiece treated in step L1 is ground with 400-mesh diamond, and the surface finish is 0.5μm.

[0090] Comparative Example 2

[0091] The first aspect of this comparative example provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0092] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 10% cobalt, 4% chromium, 0.45% iron, and 85.5% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The thickness of the composite layer is 0.50 mm. The thread pitch of the six-thread is 26 mm, the lead of the six-thread is 156 mm, and the thread depth of the six-thread is 1 mm. The composite layer needs to be further finely ground, and the surface finish of the fine grinding is 0.5 μm.

[0093] The spraying of the water seal bushing includes at least the following steps:

[0094] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0095] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 120°C for 30 minutes.

[0096] S3. Allow the workpiece obtained in step S2 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the spray gun head and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour and the fuel flow rate is 32 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed is 80 grams / minute and the thickness of the base material is 0.1mm.

[0097] S4. Allow the workpiece obtained in step S3 to cool naturally to 60°C. Use a 4-inch HVOF spray gun to spray the composite layer material onto the surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the spray gun and the workpiece surface is 380mm. The oxygen flow rate is 40 liters / hour, the fuel flow rate is 32 liters / hour, and the powder feeder completes the powder feeding of the composite layer material at a speed of 100 grams / minute. The composite layer thickness is 0.4mm, and the workpiece temperature is controlled at 160°C. After spraying, allow it to cool naturally to room temperature of 25°C.

[0098] The blasting material is 16# white fused alumina powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0099] The underlying material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0100] The carbon-containing tungsten was purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0101] The fine grinding includes the following steps:

[0102] L1. The surface of the sprayed water seal bushing is ground with a 120-mesh diamond grinding wheel, and the coating dimensional tolerance is controlled within 0.01mm.

[0103] L2. The surface coating of the workpiece treated by step L1 is ground with 400-mesh diamond, and the surface finish is above 0.5μm.

[0104] Comparative Example 3

[0105] The first aspect of this comparative example provides a thermally sprayed water seal bushing with a six-threaded design and a composite layer covering its surface.

[0106] The base material of the water seal bushing is Q355B steel. The raw materials for preparing the composite layer include, by mass percentage: 10% cobalt, 4% chromium, 0.4% iron, and 85.6% carbon-containing tungsten. The carbon-containing tungsten contains a certain amount of carbon, and the mass percentage of carbon in the carbon-containing tungsten is 5.96%. The six-thread thread has a thread pitch of 26mm, a lead of 156mm, and a thread depth of 1mm. The composite layer is not precision ground.

[0107] The spraying of the water seal bushing includes at least the following steps:

[0108] S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air.

[0109] S2. One hour after sandblasting, place the workpiece processed in step S1 into the spraying operation room and preheat it using an HVOF spray gun. The preheating temperature is 120°C and the preheating time is 30 min.

[0110] S3. Naturally cool the workpiece obtained in step S2 to 60°C, and use an HVOF spray gun with a 4-inch nozzle to spray the base material onto the surface of the workpiece. The distance between the nozzle of the spray gun and the surface of the workpiece is 380 mm, the oxygen flow rate is 40 L / hour, the fuel flow rate is 32 L / hour. Use a powder feeder to complete the powder feeding and spraying of the base material, with a powder feeding speed of 80 g / minute, and the thickness of the base material is 0.2 mm.

[0111] S4. Naturally cool the workpiece obtained in step S3 to 60°C, and use an HVOF spray gun with a 4-inch nozzle to spray the composite layer material onto the surface. The composite layer is a powder made by mixing tungsten carbide, cobalt, chromium, and iron. The distance between the nozzle and the surface of the workpiece is 380 mm, the oxygen flow rate is 40 L / hour, the fuel flow rate is 32 L / hour. Use a powder feeder to complete the powder feeding of the composite layer material, with a powder feeding speed of 100 g / minute, and the thickness of the composite layer is 0.55 mm. Control the temperature of the workpiece at 160°C, and after spraying, naturally cool it to the normal temperature of 25°C.

[0112] The sandblasting material is 16# white corundum powder, purchased from Zhengzhou Haixu Abrasive Co., Ltd.

[0113] The base material is 625 alloy, purchased from Shanghai Osaka Metal Materials Group Co., Ltd.

[0114] The tungsten carbide is purchased from Xingtai Jiuqiao Welding Materials Co., Ltd.

[0115] Performance Test

[0116] I. Vickers Hardness Test

[0117] Test object: The thermal spraying water seal shaft sleeves obtained from Examples 1-3 and Comparative Examples 1-3

[0118] Test standard: The hardness value obtained after maintaining a test force of 0.3 kg for 15 s (qualified if greater than 1150 Hv)

[0119] Test method: Refer to GB / T 4340.1-2009

[0120] II. Service Life Test

[0121] Install the water seal shaft sleeves after the cladding composite layer operation of Examples 1-3 and Comparative Examples 1-3 onto the mud pump for normal use. Observe whether there are any damages or cracks on the water seal shaft sleeves every week, and fill in the time when damages or cracks occur in Table 1.

[0122] Table 1

[0123] Vickers hardness (Hv) Service life Example 1 1200 6 months Example 2 1250 6.5 months Example 3 1220 6 months Comparative Example 1 1110 4.5 months Comparative Example 2 1045 3 months Comparative Example 3 1180 5 months

Claims

1. A thermally sprayed water seal bushing, characterized in that, The water seal bushing has a specially designed six-threaded thread, and the surface of the water seal bushing is coated with a composite layer. The six-threaded thread has a thread pitch of 10-40mm, a lead of 60-240mm, and a thread depth of 0.1-3mm. The composite layer comprises, by mass percentage, 1-15% cobalt, 1.0-10% chromium, 0.01-5% iron, with the balance being carbon-containing tungsten, wherein the carbon content of the carbon-containing tungsten is 5-10% by mass. The composite layer on the surface of the water seal bushing needs further fine grinding; The spraying of the water seal bushing includes at least the following steps: S1. Wipe the surface of the water seal bushing substrate with alcohol until it is clean and free of oil stains. After the alcohol on the substrate surface is dry, perform sandblasting. The air pressure during the sandblasting process is 0.7-0.8MPa. Use a hard plastic brush to brush off the particles remaining after sandblasting on the surface, and blow away the particles remaining on the surface with compressed air. S2. Within 2 hours after sandblasting, place the workpiece processed in step S1 into the spraying room and preheat it with an HVOF spray gun at a temperature of 110-150℃ for 10-60 minutes. S3. Allow the workpiece obtained in step S2 to cool naturally to 40-80℃. Use a 4-inch HVOF spray gun to spray the base material onto the workpiece surface. The distance between the gun head and the workpiece surface should be 300-400mm. The oxygen flow rate should be 30-50 liters / hour, and the fuel flow rate should be 20-40 liters / hour. Use a powder feeder to complete the powder feeding and spraying of the base material. The powder feeding speed should be 60-100 grams / minute, and the thickness of the base material coating should be 0.1-0.15mm. S4. Allow the workpiece obtained in step S3 to cool naturally to 40-80℃. Use a 4-inch HVOF spray gun to spray the composite layer material onto the workpiece surface. The composite layer is a powder made of tungsten carbide, cobalt, chromium, and iron. The distance between the gun head and the workpiece surface is 300-400mm. The oxygen flow rate is 30-50 liters / hour, and the fuel flow rate is 20-40 liters / hour. The powder feeder completes the powder feeding of the composite layer material at a speed of 80-120 grams / minute. The thickness of the composite layer coating is 0.4-0.6mm. During the spraying process, the workpiece temperature is controlled below 165℃. After the spraying is completed, allow it to cool naturally to room temperature. The sum of the thickness of the composite layer coating and the thickness of the underlying material coating is 0.7-1.0 mm.

2. The thermally sprayed water seal bushing according to claim 1, characterized in that, The surface finish of the fine grinding is greater than 0.4 μm.

3. An application of the thermally sprayed water seal bushing according to any one of claims 1-2, characterized in that, Thermally sprayed water seal bushings are used in the mud pump sealing system of ships.

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