Surface coating of shaft sleeve suitable for marine environment and preparation method and application thereof

Abstract

The invention discloses a surface coating suitable for a shaft sleeve in a marine environment, which is a composite coating, and the composite coating comprises a bonding layer, a working layer and a hole sealing layer from inside to outside; the bonding layer is a NiCr alloy layer, and the thickness of the bonding layer is 60-100 microns; the working layer is a ceramic coating, and the thickness of the working layer is 100-300 microns; and the hole sealing layer is a resin hole sealing agent. Meanwhile, the invention also discloses a preparation method of the surface coating, which comprises the following steps of: (1) degreasing and texturing the shaft sleeve base body; (2) preparing a bonding layer by adopting a high velocity oxy-fuel (HVOF) technology; (3) preparing a working layer by adopting an atmospheric plasma spraying (APS) technology; and (4) carrying out hole sealing treatment on the coating. The wear resistance and corrosion resistance of the surface coating are greatly improved, and the service life of the shaft sleeve is prolonged.

Description

Technical Field

[0001] The invention relates to a surface coating for prolonging the service life of a shaft sleeve in a marine environment and a preparation method thereof. Background Art

[0002] The shaft sleeve of nuclear power seawater pump is an important part of the nuclear power plant water system. Its function is to provide cooling water for the nuclear power plant under various operating conditions of the unit. In order to save costs, seawater is often used as the cooling water medium. - The corrosion effect will cause serious corrosion of the shaft sleeve of the nuclear power seawater pump during service, greatly shortening the service life of the sleeve, and it needs to be replaced frequently to ensure the safe operation of the nuclear power seawater pump.

[0003] At present, the material of the shaft sleeve used in the marine environment is generally UNS S32760 duplex stainless steel. This material has good seawater corrosion resistance, but its wear resistance is poor. Under the combined effects of corrosion and wear, the service life is short, and the shaft sleeve needs to be replaced regularly. The shaft sleeve cannot be repaired and reused, so the cost of using traditional shaft sleeves is high.

[0004] At present, there are two main surface treatment methods for improving the corrosion and wear resistance of shaft sleeves: (1) electroplating technology: the process is simple and low-cost, but the coating is physically bonded to the substrate, and the bonding force is poor. Under long-term friction and corrosion working conditions, the coating is prone to breakage and peeling. In addition, among the currently available electroplating materials, seawater corrosion-resistant coating materials are rare, and the corrosion resistance is not higher than that of UNS S32760 duplex stainless steel. (2) laser cladding technology: the coating and the substrate are metallurgically bonded, avoiding the generation of pore cracks, thereby completely blocking the contact between the corrosive medium and the substrate. However, since the shaft sleeve is a thin-walled part, the heat input of the laser cladding process is high, and the alternating hot and cold processes will cause the shaft sleeve to deform. In addition, the coating is rough after cladding, and mechanical processing such as turning is required to ensure the dimensional accuracy of the components, so the production efficiency is low. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a surface coating for a shaft sleeve in a marine environment, which greatly improves the wear and corrosion resistance and prolongs the service life of the shaft sleeve. At the same time, the present invention also provides a method for preparing the coating, which not only ensures the bonding force between the coating and the substrate, but also prevents the deformation of the shaft sleeve. In addition, the present invention also provides an application of the surface coating.

[0006] The invention discloses a surface coating suitable for a shaft sleeve in a marine environment. The composite coating comprises a bonding layer, a working layer and a sealing layer from the inside to the outside. The bonding layer is a NiCr alloy layer with a thickness of 60 to 100 μm. The working layer is a ceramic coating with a thickness of 100 to 300 μm. The sealing layer is a resin sealing agent.

[0007] The material of the ceramic coating is Al2O3 or Al2O3+13%TiO2.

[0008] The preparation method of the surface coating of the present invention comprises the following steps: 1. degreasing and roughening the sleeve substrate; 2. preparing the bonding layer by using the supersonic flame spraying technology (HVOF), wherein the powder component is NiCr alloy powder, and the powder particle size is 15 to 60 μm; 3. preparing the working layer by using the atmospheric plasma spraying technology (APS), wherein the powder component is Al2O3 or Al2O3+13%TiO2, and the powder particle size is 10 to 60 μm; 4. sealing the coating.

[0009] The preparation method of the surface coating of the present invention: Step ②: The thermal spraying process is: the oxygen flow rate is 850-950 L / min, the kerosene flow rate is 20-25 L / h, the powder feeding rate is 60-80 g / min, the barrel length is 100-150 mm, the spraying distance is 300-380 mm, the step distance is 5-8 mm, the scanning speed is 400-800 mm / s, and the bonding layer thickness is 60-100 μm.

[0010] The preparation method of the surface coating of the present invention: Step ③: When the powder component of the working layer is Al2O3, the thermal spraying process is: the current is 650-750A, the power is 42-48kW, the main gas flow rate is 35-40L / min, the auxiliary gas flow rate is 4-8L / min, the powder feeding rate is 15-30g / min, the powder feeding gas flow rate is 3-5L / min, the spraying distance is 100-150mm, the step distance is 5-8mm, the scanning speed is 400-700mm / s, and the working layer thickness is 100-300μm.

[0011] The preparation method of the surface coating of the present invention: Step ③: When the powder composition of the working layer is Al2O3+13%TiO2, the thermal spraying process is: the current is 600-700A, the power is 40-45kW, the main gas flow rate is 30-40L / min, the auxiliary gas flow rate is 5-8L / min, the powder feeding rate is 15-30g / min, the powder feeding gas flow rate is 3-5L / min, the spraying distance is 100-150mm, the step distance is 5-8mm, the scanning speed is 400-700mm / s, and the working layer thickness is 100-300μm.

[0012] The preparation method of the surface coating of the present invention: step ④ is specifically as follows: Ⅰ, preheating the shaft sleeve to 60-80°C; Ⅱ, using a resin sealer, stirring it evenly before use, and placing it in a negative pressure box to discharge bubbles in the sealer; Ⅲ, applying the sealer to the coating surface by brushing, keeping the surface wet for 5-15 minutes, and then performing room temperature curing treatment for 20-30 hours; Ⅳ, polishing to remove the residual sealer on the surface of the shaft sleeve coating after curing, and making the roughness meet the design requirements.

[0013] The advantages of the surface coating and preparation method of the shaft sleeve of the present invention are: 1. The coating is a composite coating: 1. The bonding layer makes the bonding strength of the composite coating ≥50MPa (from Figure 2 It can be seen that the use conditions are fully met; 2. The working layer ensures the wear resistance of the composite coating, and different materials are selected for different working conditions; 3. The sealing layer isolates the penetration of seawater into the substrate and strengthens the corrosion resistance of the sleeve substrate; 2. Preparation method of spraying + sealing method: 1. The bonding layer is an alloy coating, and its thermal expansion coefficient is between the substrate and the working layer. It is mainly used to improve the bonding strength of the coating. Since the alloy melting point is low, supersonic flame spraying can meet the powder spraying requirements; 2. The working layer is a ceramic coating with a high melting point, so the coating is prepared by atmospheric plasma spraying with a higher flame flow temperature; 3. Supersonic flame spraying and atmospheric plasma spraying technologies are sprayed through their respective specific process parameters to obtain the best thermal spraying parameters for metallographic structure, coating hardness, wear resistance and corrosion resistance; 4. During the thermal spraying process, the surface temperature of the sleeve does not exceed 100°C; Therefore, for sleeves that are thin-walled parts, thermal spraying is more suitable for preparing a surface strengthening layer to prevent the sleeve from deformation.

[0014] Therefore, the wear and corrosion resistance of the surface coating of the shaft sleeve of the present invention is greatly improved, thereby extending the service life of the shaft sleeve. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of the surface coating of the present invention;

[0016] Figure 2 It is a tensile curve diagram of the surface coating obtained in Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the embodiments.

[0018] Example 1

[0019] The composite coating is prepared on the surface of UNS S32760 duplex stainless steel sleeve by thermal spraying. The composite coating structure is bonding layer + working layer 1 (Al2O3):

[0020] Step ①: The bonding layer is prepared by supersonic flame spraying technology (HVOF), the powder composition is NiCr alloy powder, the powder particle size is 15-60 μm, the thermal spraying process is: oxygen flow rate is 850-950 L / min, kerosene flow rate is 20-25 L / h, powder feeding rate is 60-80 g / min, barrel length is 100-150 mm, spraying distance is 300-380 mm, step distance is 5-8 mm, scanning speed is 400-800 mm / s, and bonding layer thickness is 60-100 μm;

[0021] Step ②: The working layer is prepared by atmospheric plasma spraying technology (APS), the powder composition is Al2O3, the powder particle size is 10-60μm, the thermal spraying process is: the current is 650-750A, the power is 42-48kW, the main gas flow rate is 35-40L / min, the auxiliary gas flow rate is 4-8L / min, the powder feeding rate is 15-30g / min, the powder feeding gas flow rate is 3-5L / min, the spraying distance is 100-150mm, the step distance is 5-8mm, the scanning speed is 400-700mm / s, and the working layer thickness is 100-300μm;

[0022] Step ③: Ⅰ. Preheat the sleeve to 60-80℃; Ⅱ. Use a resin sealer, stir it evenly before use, and place it in a negative pressure box to expel bubbles in the sealer; Ⅲ. Apply the sealer to the coating surface by brushing, keep the surface moist for 5-15 minutes, and then cure it at room temperature for 20-30 hours; Ⅳ. After curing, polish to remove the residual sealer on the surface of the sleeve coating and make the roughness meet the design requirements.

[0023] This working layer has high hardness and wear resistance, and can be used for surface strengthening of sleeves under high speed and high wear conditions.

[0024] Example 2

[0025] The composite coating is prepared on the surface of UNS S32760 duplex stainless steel sleeve by thermal spraying. The composite coating structure is bonding layer + working layer 2 (Al2O3 + 13% TiO2):

[0026] Step ①: The preparation method of the adhesive layer is the same as that of Example 1;

[0027] Step ②: The working layer is prepared by atmospheric plasma spraying technology (APS), the powder composition is Al2O3+13%TiO2, the current is 600-700A, the power is 40-45kW, the main gas flow rate is 30-40L / min, the auxiliary gas flow rate is 5-8L / min, the powder feeding rate is 15-30g / min, the powder feeding gas flow rate is 3-5L / min, the spraying distance is 100-150mm, the step distance is 5-8mm, the scanning speed is 400-700mm / s, and the working layer thickness is 100-300μm;

[0028] Step ③: The preparation method of sealing is the same as that of Example 1.

[0029] This working layer is doped with 13% TiO2 (mass fraction), which improves the toughness of the coating and slightly reduces the wear resistance. It can be used to strengthen the surface of the sleeve under conditions of high speed and vibration during use.

[0030] The advantages of the surface coating and preparation method of the shaft sleeve of the present invention are: 1. The coating is a composite coating: 1. The bonding layer makes the bonding strength of the composite coating ≥50MPa (from Figure 2 It can be seen that since the sleeve of the present invention is not subjected to impact during service and only wear occurs, the bonding strength of ≥50MP fully meets the use conditions, ensuring that the coating is not prone to breakage and peeling even under long-term friction and corrosion working conditions; 2. The working layer ensures the wear resistance of the composite coating, and different materials are selected for different working conditions; 3. The sealing layer isolates the penetration of seawater into the substrate and strengthens the corrosion resistance of the sleeve substrate; therefore, the wear resistance and corrosion resistance of the surface composite coating of the sleeve of the present invention are greatly improved, extending the service life of the sleeve; 2. Preparation method of spraying + sealing method: 1. The bonding layer is an alloy coating, The thermal expansion coefficient is between that of the substrate and the working layer, and is mainly used to improve the bonding strength of the coating. Since the alloy has a low melting point, supersonic flame spraying can meet the requirements of powder spraying; 2. The working layer is a ceramic coating with a high melting point, so the coating is prepared by atmospheric plasma spraying with a higher flame flow temperature; 3. Supersonic flame spraying and atmospheric plasma spraying technologies are sprayed through their respective specific process parameters to obtain thermal spraying parameters with the best metallographic structure, coating hardness, wear resistance and corrosion resistance; 4. During the thermal spraying process, the surface temperature of the sleeve does not exceed 100°C; therefore, for sleeves that are thin-walled parts, thermal spraying is more suitable for preparing surface strengthening layers.

[0031] In summary, the composite coating of the sleeve obtained by thermal spraying + sealing treatment in the present invention ensures that the penetration of seawater into the substrate is isolated, the corrosion resistance of the sleeve substrate is enhanced, and the wear performance of the sleeve is greatly improved, thereby extending the service life of the sleeve; and after the sleeve has been used for a cycle, the coating can be removed and re-prepared, thereby increasing the number of recycling times of the sleeve and reducing the cost of use.

Claims

1. A surface coating for a sleeve suitable for use in a marine environment, characterized by: It is a composite coating, which includes a bonding layer, a working layer and a sealing layer from the inside to the outside; the bonding layer is a NiCr alloy layer with a thickness of 60 to 100 μm; the working layer is a ceramic coating with a thickness of 100 to 300 μm; and the sealing layer is a resin sealing agent.

2. The surface coating according to claim 1, characterized in that: The material of the ceramic coating is Al2O3 or Al2O3+13%TiO2.

3. A method for preparing a surface coating of a shaft sleeve suitable for use in a marine environment as described in claims 1-2, comprising the following steps: ① The sleeve substrate is degreased and roughened; ② The bonding layer is prepared by using the supersonic flame spraying technology (HVOF), the powder composition is NiCr alloy powder, and the powder particle size is 15 to 60 μm; ③ The working layer is prepared by using the atmospheric plasma spraying technology (APS), the powder composition is Al2O3 or Al2O3+13%TiO2, and the powder particle size is 10 to 60 μm; ④ The coating is sealed.

4. The preparation method according to claim 3 is characterized in that: step ②: the thermal spraying process is: oxygen flow rate is 850-950L / min, kerosene flow rate is 20-25L / h, powder feeding rate is 60-80g / min, barrel length is 100-150mm, spraying distance is 300-380mm, step distance is 5-8mm, scanning speed is 400-800mm / s, and bonding layer thickness is 60-100μm.

5. The preparation method according to claim 3 is characterized in that: step ③: when the powder component of the working layer is Al2O3, the thermal spraying process is: current is 650-750A, power is 42-48kW, main gas flow rate is 35-40L / min, auxiliary gas flow rate is 4-8L / min, powder feeding rate is 15-30g / min, powder feeding gas flow rate is 3-5L / min, spraying distance is 100-150mm, step distance is 5-8mm, scanning speed is 400-700mm / s, and working layer thickness is 100-300μm.

6. The preparation method according to claim 3 is characterized in that: Step ③: when the powder composition of the working layer is Al2O3+13%TiO2, the thermal spraying process is: the current is 600-700A, the power is 40-45kW, the main gas flow rate is 30-40L / min, the auxiliary gas flow rate is 5-8L / min, the powder feeding rate is 15-30g / min, the powder feeding gas flow rate is 3-5L / min, the spraying distance is 100-150mm, the step distance is 5-8mm, the scanning speed is 400-700mm / s, and the working layer thickness is 100-300μm.

7. The preparation method according to claim 3, characterized in that: Step ④ is specifically as follows: Ⅰ. Preheat the shaft sleeve to 60-80℃; Ⅱ. Use a resin sealer, stir it evenly before use, and place it in a negative pressure box to expel bubbles in the sealer; Ⅲ. Apply the sealer to the coating surface by brushing, keep the surface moist for 5-15 minutes, and then cure it at room temperature for 20-30 hours; Ⅳ. After curing, polish to remove the residual sealer on the surface of the shaft sleeve coating and make the roughness meet the design requirements.

8. Use of the surface coating according to claims 1-2 on a shaft sleeve suitable for use in a marine environment.

Images