A method for manufacturing a plasma-sprayed metal casing and a centrifugal pump

Abstract

The application discloses a preparation method of a plasma sprayed metal shell, which comprises the following steps: silane pretreatment is performed on the metal shell to form a silane film with a three-dimensional network structure on the surface of the metal shell; plasma plating treatment is performed on the metal shell after the silane pretreatment to deposit a coating on the surface of the metal shell; alloy vacuum air-atomized powder NiCoCrAlYHfSi is used for plasma powder spraying, the content of Ni is 50-60%, the content of Co is 15-25%, the content of Cr is 15-25%, the content of Al is 5-8%, the content of Y is 0.1-1%, the content of Hf is 0.5-1%, and the content of Si is 0.2-0.4%; and annealing treatment is performed on the coating after the plasma treatment to modify the coating. The silane pretreatment is used to form a condensed oligomer network silane film, then plasma spraying is used to obtain a corrosion-resistant coating with strong adhesion, and finally annealing treatment is used to make the double-layer film more compact.

Description

Technical Field

[0001] This invention relates to the technical field of metal casing surface treatment, and in particular to a method for preparing a plasma-sprayed metal casing and a centrifugal pump. Background Technology

[0002] Centrifugal pumps operating in open environments are typically exposed to variable weather conditions, including rain, snow, and humid climates. High humidity increases the chances of pump components coming into contact with moisture, thus accelerating the corrosion process. On the other hand, airborne pollutants, such as chemical gases, dust, and particulate matter, can adhere to the pump's surface, leading to corrosion. These pollutants can react with water or moisture to form corrosive substances. Centrifugal pump components are usually made of metal, and different types of metal have varying degrees of resistance to corrosion. If the chosen metal does not provide sufficient resistance to corrosive factors in the environment, the pump components are susceptible to corrosion. High humidity and high salinity environments exacerbate the erosion of centrifugal pumps, especially cast pump casings. Therefore, in atmospheric environments, centrifugal pumps require additional protective measures to safeguard them from external environmental damage.

[0003] Existing patents, such as CN202210640938.4 (a surface anti-corrosion method for fasteners of centrifugal pumps in important nuclear power plants), involve coating the surface of studs with cadmium. Cadmium, a highly toxic heavy metal, not only causes environmental pollution upon its release but also causes irreversible damage to the kidneys and respiratory system. Therefore, the anti-corrosion method provided by this patent is environmentally unfriendly. Furthermore, this patent mainly applies to fasteners such as studs and bolts in centrifugal pumps used in nuclear power plants, primarily during pump installation and maintenance. Therefore, it cannot protect centrifugal pumps operating for extended periods in high-humidity, high-salt environments. Patent CN202110902567.8 (a corrosion-resistant and wear-resistant centrifugal pump) primarily achieves anti-corrosion by providing a compact, short, double-end mechanical seal. However, this technology requires the mechanical seal to be compatible with the existing power centrifugal pump structure and dimensions, limiting its application scope. Moreover, the development and design of the end-face structure requires mold making, resulting in high costs. Therefore, current centrifugal pump anti-corrosion technologies have limited applicability, high process costs, and poor environmental performance. Summary of the Invention

[0004] Purpose of the invention: The first purpose of this invention is to provide a method for preparing a plasma-sprayed metal shell. This invention forms a condensed and aggregated network silane film on the surface of the metal shell through silane pretreatment, followed by plasma spraying technology to obtain a corrosion-resistant coating with strong adhesion. Finally, annealing treatment is used to make the double-layer film denser and at the same time eliminate the oxygen content in the coating to prevent the metal shell from being oxidized and corroded.

[0005] The second objective of this invention is to provide a centrifugal pump that has strong corrosion resistance and can be used stably in outdoor environments for extended periods, thus solving problems such as the centrifugal pump casing being susceptible to corrosion in outdoor environments and the long time required for material preparation.

[0006] Technical solution: To achieve the above objectives, this invention discloses a method for preparing a plasma-sprayed metal shell, comprising the following steps:

[0007] (1) The metal shell is pretreated with silane, and the silane pretreatment forms a silane film with a three-dimensional network structure on the surface of the metal shell.

[0008] (2) Plasma plating is performed on the metal shell after silane pretreatment to deposit a coating on the surface of the metal shell; the plasma powder spraying uses alloy vacuum atomized powder NiCoCrAlYHfSi, with Ni content of 50-60%, Co content of 15-25%, Cr content of 15-25%, Al content of 5-8%, Y content of 0.1-1%, Hf content of 0.5-1%, and Si content of 0.2-0.4%;

[0009] (3) The plasma-treated coating is modified by annealing.

[0010] In step (1), the silane treatment solution contains 95-98 wt% trichloromethylsilane as the solute, 1-2 wt% zirconium tetrabutyrate as the coupling agent, 0.2-0.3 wt% allyl alcohol polyether as the surfactant, and ethanol as the solvent.

[0011] Preferably, the hydrolysis temperature in the silane treatment of step (1) is 25-35°C and the dipping time is 5-8 min.

[0012] Furthermore, before plasma plating in step (2), 10-15 wt% ammonium citrate is used as a cleaning solution to chemically clean the surface of the metal shell. After chemical cleaning, the surface of the metal shell is roughened by sandblasting. After sandblasting, the metal shell is heated to 400-700℃ at a heating rate of 5-20℃ / min.

[0013] Furthermore, in step (2) during the plasma plating process, the ratio of the metal shell temperature T1 to the melting point temperature of the plasma powder spraying T2 is maintained within the range of: 0.3≤T1 / T2≤0.5.

[0014] Preferably, in step (2), the plasma discharge treatment time is no more than 5 min, the plasma working voltage is 20 kV to 45 kV, the plasma working frequency is 10 kHz to 20 kHz, the plasma vacuum degree is controlled at 500 to 1500 Pa, the spraying power is 50 to 60 kW, and the protective gas flow rate is set to 50 to 60 L / min.

[0015] Furthermore, in step (2), during ion plating, the coating thickness h is controlled according to the following formula:

[0016] h=γρt / d

[0017] In the formula, γ is the material coefficient, which is related to the material of the metal shell, and ρ is the plasma density, ranging from 500 to 1000 cm⁻¹. -3 ; t is the plasma treatment time; d is the distance between the plasma nozzle outlet and the metal casing.

[0018] Furthermore, in step (2), the particle size of the plasma sprayed powder is 32–42 μm.

[0019] Preferably, during the modification annealing process in step (3), the pressure inside the vacuum sintering furnace is controlled below 0.1 MPa. First, the temperature of the vacuum furnace is raised to 650-800°C at a certain heating rate and held for 1-1.5 hours. Then, the temperature is raised to 950-1100°C at the same heating rate and held for 30-40 minutes before annealing begins. Then, the temperature is annealed at a uniform rate of 5-10°C / min for 80-120 minutes to 200-300°C. Finally, the metal shell is allowed to cool naturally to room temperature with the furnace.

[0020] This invention discloses a centrifugal pump, which is processed using the above-mentioned plasma spraying metal shell preparation method to form a coating on the surface.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) In the silane treatment process of the present invention, by adding a reasonable amount of zirconium tetrabutyrate coupling agent and allyl alcohol polyether surfactant, the polarization resistance and adhesion of the coating are improved, thereby enhancing the uniformity, corrosion resistance and service life of the coating.

[0023] (2) In the plasma plating process of the present invention, the centrifugal pump shell temperature T1 and the plasma powder spraying melting point temperature T2 are controlled within a reasonable range, and the resulting coating has a finer microstructure and smaller structural unit size, exhibiting good adhesion, uniformity and density.

[0024] (3) By setting reasonable heating and cooling rates during the annealing process of the present invention, the crystal structure and grain boundaries are more regular during the coating generation and plating process, thereby improving the uniformity of the coating; at the same time, excessive residual stress and thermal shock are avoided, reducing the risk of deformation and cracking of the coating during the process.

[0025] (4) In this invention, the centrifugal pump housing after plasma spraying is modified by annealing. By combining the two, the structure of the sprayed coating can be changed from layered mechanical bonding to metallurgical bonding, making the coating on the surface of the housing more dense, improving the adhesion between the coating and the centrifugal pump housing, and reducing the oxygen content in the coating, which significantly improves the corrosion resistance and oxidation resistance of the centrifugal pump housing and reduces the damage caused by acidic substances in rainwater to the centrifugal pump housing.

[0026] (5) The present invention uses a combination of silane treatment, plasma plating and annealing modification to prepare a composite coating with a smoother morphology, finer grains and a denser structure. The composite coating has better wear resistance, corrosion resistance and adhesion and a longer service life. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process of the present invention;

[0028] Figure 2 This is a scanning electron microscope image of the film surface generated after silane treatment in this invention;

[0029] Figure 3 This is a scanning electron microscope image of the double-layer film structure on the surface of the outer shell after ion spraying in this invention;

[0030] Figure 4(a) shows the microstructure of the coating surface before annealing treatment according to the present invention;

[0031] Figure 4(b) shows the microstructure of the coating surface after annealing treatment according to the present invention;

[0032] Figure 5(a) is a scanning electron microscope image of the interface between the coating and the centrifugal pump housing before annealing treatment according to the present invention;

[0033] Figure 5(b) is a scanning electron microscope image of the interface between the coating and the centrifugal pump housing after annealing treatment according to the present invention;

[0034] Figure 6 This is a schematic diagram of the impedance Bode test performed when allyl alcohol polyether is used as a surfactant in this invention. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0036] like Figure 1 As shown, this invention discloses a method for preparing a plasma-sprayed metal shell, comprising the following steps:

[0037] (1) The centrifugal pump casing undergoes silane pretreatment, which forms a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing, such as... Figure 2As shown, the silane film is uniform and durable. In the silane treatment solution, the solute component is 95–98 wt% trichloromethylsilane, the coupling agent is 1–2 wt% zirconium tetrabutyrate, and 0.2–0.3 wt% allyl alcohol polyether is added as a surfactant. The solvent is ethanol. The hydrolysis temperature in the silane treatment is 25–35 °C, and the immersion time is 5–8 min. The coupling agent zirconium tetrabutyrate can catalyze the transcoating reaction, reacting with the carboxylic acid functional groups in the silane to form new bonds and enhance the adhesion of the coating. The surfactant allyl alcohol polyether reduces the surface tension between the silane and the centrifugal pump housing, promoting… The invention promotes uniform distribution of silane and enhances the adhesion of the silane coating to the surface. In the silane pretreatment process, a silane film with a concentration of 95-98 wt% is used to form on the surface of the centrifugal pump casing, improving the pump's corrosion resistance and chemical resistance. Especially in extremely corrosive environments, it reduces corrosion of the casing by acidic substances in rainwater, avoiding the use of traditional fluorosilanes and reducing potential environmental damage. The use of organosilanes allows for the formation of a silane film with a three-dimensional network structure on the centrifugal pump casing surface, further enhancing its corrosion resistance.

[0038] (2) Before plasma plating, 10-15 wt% ammonium citrate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing. The organic acid ammonium salt can effectively remove the ions, oxides and other contaminants accumulated on the housing surface. After chemical cleaning, the surface of the centrifugal pump housing is roughened by sandblasting to improve the bonding force between the silane film and the housing. After sandblasting, the centrifugal pump housing is heated to 400-700℃ at a heating rate of 5-20℃ / min. In this invention, ammonium citrate or sodium metasilicate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing after silane pretreatment. The Fe ions in the rust on the housing surface are encapsulated in the chelating agent and become stable compounds with larger molecular weights, which can more effectively remove the ions, oxides and other contaminants accumulated on the surface.

[0039] like Figure 3As shown, the centrifugal pump casing, after silane pretreatment, is subjected to plasma plating to deposit a coating on its surface. The plasma powder is an alloy vacuum atomized powder, NiCoCrAlYHfSi, with a particle size of 32–42 μm, Ni content of 50–60%, Co content of 15–25%, Cr content of 15–25%, Al content of 5–8%, Y content of 0.1–1%, Hf content of 0.5–1%, and Si content of 0.2–0.4%. During the plasma plating process, the ratio of the centrifugal pump casing temperature T1 to the melting point temperature of the plasma powder T2 is maintained within the range of 0.3 ≤ T1 / T2 ≤ 0.5. Plasma plating is performed within this range, allowing for controlled surface diffusion deposition. This results in a relatively dense columnar crystalline coating and a closely packed fibrous structure forming on the centrifugal pump casing surface. The plasma powder material exhibits excellent oxidation and corrosion resistance, as well as good adhesion.

[0040] The plasma source employs arc discharge technology to generate high-energy electrons and ions, enabling plasma powder coating of the surface. Argon is used as the protective gas. The plasma discharge treatment time is no more than 5 minutes, the plasma operating voltage is 20kV~45kV, the plasma operating frequency is 10kHz~20kHz, the plasma vacuum degree is controlled at 500~1500pa, the spraying power is 50~60kW, and the protective gas flow rate is set to 50~60L / min. In the plasma coating process of this invention, argon is used as the protective gas to dilute and control the plasma, which can avoid gas contamination. On the other hand, argon, as an ionizing gas, provides protection for the easily oxidized centrifugal pump casing. The plasma coating technology used in this invention has low process cost, high deposition efficiency, and relatively dense coating, making it suitable for industrial-scale production.

[0041] In plasma plating, the coating thickness h is controlled according to the following formula:

[0042] h=γρt / d

[0043] In the formula, γ is the material coefficient, which is related to the material of the centrifugal pump casing, and ρ is the plasma density, ranging from 500 to 1000 cm⁻¹. -3 ; t is the plasma treatment time; d is the distance between the plasma nozzle outlet and the centrifugal pump casing;

[0044] (3) The plasma-treated coating is modified by annealing. During the modification annealing process, the pressure inside the vacuum sintering furnace is controlled below 0.1 MPa. First, the temperature of the vacuum furnace is raised to 650-800℃ at a certain heating rate and held for 1-1.5 hours. Then, the temperature is raised to 950-1100℃ at the same heating rate and held for 30-40 minutes before annealing begins. The temperature is then uniformly annealed at a cooling rate of 5-10℃ / min for 80-120 minutes to 200-300℃. Finally, the centrifugal pump casing is allowed to cool naturally to room temperature with the furnace. During the modification annealing process, external hydrogen gas is introduced into the furnace to ensure that the furnace is filled with flowing hydrogen gas. In this invention, the centrifugal pump housing after plasma spraying is modified by annealing, which changes the structure of the sprayed coating from a layered mechanical bond to a metallurgical bond, improving the adhesion between the coating and the centrifugal pump housing, and reducing the oxygen content in the coating, thus significantly improving the corrosion resistance and oxidation resistance of the pump housing. Annealing the surface of the plasma sprayed coating makes the coating on the housing surface denser and reduces the oxygen content in the coating, thereby reducing the risk of oxidation of the centrifugal pump housing, which is an iron and aluminum casting, as shown in Figures 4(a), 4(b), 5(a), and 5(b).

[0045] The present invention discloses a centrifugal pump, which is processed by the above-mentioned plasma spraying metal shell preparation method to form a coating on the surface.

[0046] Example 1

[0047] Example 1 discloses a method for preparing a plasma-sprayed metal shell, comprising the following steps:

[0048] (1) The centrifugal pump casing is pretreated with silane. The silane pretreatment forms a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing. This silane film is uniform and durable. In the silane treatment solution, the solute component is 95 wt% trichloromethylsilane, the coupling agent is 1 wt% zirconium tetrabutyrate, and 0.2 wt% allyl alcohol polyether is added as a surfactant. The solvent is ethanol. The hydrolysis temperature in the silane treatment is 25℃, and the immersion time is 5 min. The coupling agent zirconium tetrabutyrate can catalyze the transcoating reaction and react with the carboxylic acid functional groups in the silane to form new bonds and enhance the adhesion of the coating. The surfactant allyl alcohol polyether reduces the silica content of the silane. The surface tension between the silane and the centrifugal pump casing promotes uniform distribution of the silane and enhances the adhesion of the silane coating to the surface. In the silane pretreatment process, this invention uses 95wt% trichloromethylsilane, which can form a silane film on the surface of the centrifugal pump casing, improving the corrosion resistance and chemical resistance of the centrifugal pump. Especially in extremely corrosive environments, it reduces the corrosion of the casing by acidic substances in rainwater, avoids the use of traditional fluorosilanes, and reduces potential environmental damage. The use of organosilanes can form a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing, which can improve the corrosion resistance of the centrifugal pump casing.

[0049] (2) Before plasma coating, 10wt% ammonium citrate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing. The organic acid ammonium salt can effectively remove the ions, oxides and other contaminants accumulated on the housing surface. After chemical cleaning, the surface of the centrifugal pump housing is roughened by sandblasting to improve the bonding force between the silane film and the housing. After sandblasting, the centrifugal pump housing is heated to 400°C at a heating rate of 5°C / min. In this invention, ammonium citrate or sodium metasilicate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing after silane pretreatment. The Fe ions in the rust on the housing surface are encapsulated in the chelating agent and become stable compounds with larger molecular weights, which can more effectively remove the ions, oxides and other contaminants accumulated on the surface.

[0050] The centrifugal pump casing, after silane pretreatment, undergoes plasma plating to deposit a coating on its surface. The plasma powder coating uses an alloy vacuum atomized powder, NiCoCrAlYHfSi, with a particle size of 32 μm, containing 50% Ni, 19% Co, 25% Cr, 5% Al, 0.3% Y, 0.5% Hf, and 0.2% Si. During the plasma plating process, the ratio of the centrifugal pump casing temperature T1 to the melting point temperature of the plasma powder T2 is maintained at T1 / T2 = 0.3. Within this range, surface diffusion-controlled deposition is achieved, easily forming a dense columnar crystalline coating and a closely packed fibrous structure on the centrifugal pump casing surface. The plasma powder material exhibits excellent oxidation and corrosion resistance, as well as good adhesion.

[0051] The plasma source employs arc discharge technology to generate high-energy electrons and ions, enabling plasma powder coating of the surface. Argon is used as the protective gas. The plasma discharge treatment time is no more than 5 minutes, the plasma operating voltage is 20 kV, the plasma operating frequency is 10 kHz, the plasma vacuum degree is controlled at 500 Pa, the spraying power is 50 kW, and the protective gas flow rate is set to 50 L / min. In the plasma coating process of this invention, argon is used as the protective gas to dilute and control the plasma, thus avoiding gas contamination. On the other hand, argon, as an ionizing gas, provides protection for the easily oxidized centrifugal pump casing. The plasma coating technology used in this invention has low process cost, high deposition efficiency, and produces a relatively dense coating, making it suitable for industrial-scale production.

[0052] (3) The plasma-treated coating is modified by annealing. During the modification annealing process, the pressure inside the vacuum sintering furnace is controlled below 0.1 MPa. First, the vacuum furnace temperature is raised to 650°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 950°C at a heating rate of 5°C / min and held for 30 minutes before annealing begins. The temperature is then uniformly annealed to 200°C at a cooling rate of 5°C / min for 80 minutes. Finally, the centrifugal pump casing is allowed to cool naturally to room temperature with the furnace. During the modification annealing process, external hydrogen gas is introduced into the furnace to ensure that the furnace is filled with flowing hydrogen gas. In this invention, the centrifugal pump housing after plasma spraying is modified by annealing, which changes the structure of the sprayed coating from a layered mechanical bond to a metallurgical bond, improving the adhesion between the coating and the centrifugal pump housing, and reducing the oxygen content in the coating, thus significantly improving the corrosion resistance and oxidation resistance of the pump housing. Annealing the surface of the plasma sprayed coating makes the coating on the housing surface denser and reduces the oxygen content in the coating, thereby reducing the risk of oxidation of the centrifugal pump housing, which is an iron and aluminum casting.

[0053] This invention discloses a centrifugal pump. The centrifugal pump is treated using the plasma-sprayed metal casing preparation method of Example 1 to form a coating on its surface. Characterization tests on the prepared coating showed a BET result indicating a porosity of 3.5%, with the pores primarily composed of micropores ranging in size from 10 nm to 500 nm. The adhesion between the coating and the centrifugal pump casing was tested using an adhesion tester, and the results showed an adhesion strength close to 120 N / cm². 2 The target is to achieve 600 hours of salt spray testing and a corrosion resistance level of C4.

[0054] Example 2

[0055] Example 2 discloses a method for preparing a plasma-sprayed metal shell, comprising the following steps:

[0056] (1) The centrifugal pump casing is pretreated with silane. The silane pretreatment forms a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing. This silane film is uniform and durable. In the silane treatment solution, the solute component is 97 wt% trichloromethylsilane, the coupling agent is 1 wt% zirconium tetrabutyrate, and 0.2 wt% allyl alcohol polyether is added as a surfactant. The solvent is ethanol. The hydrolysis temperature in the silane treatment is 30℃, and the immersion time is 6 min. The coupling agent zirconium tetrabutyrate can catalyze the transcoating reaction and react with the carboxylic acid functional groups in the silane to form new bonds and enhance the adhesion of the coating. The surfactant allyl alcohol polyether reduces the silica content of the silane. The surface tension between the silane and the centrifugal pump casing promotes uniform distribution of the silane and enhances the adhesion of the silane coating to the surface. In the silane pretreatment process, this invention uses trichloromethylsilane with a concentration of 97 wt%, which can form a silane film on the surface of the centrifugal pump casing, improving the corrosion resistance and chemical resistance of the centrifugal pump. Especially in extremely corrosive environments, it reduces the corrosion of the casing by acidic substances in rainwater, avoids the use of traditional fluorosilanes, and reduces potential environmental damage. The use of organosilanes can form a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing, which can improve the corrosion resistance of the centrifugal pump casing.

[0057] (2) Before plasma coating, 12wt% ammonium citrate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing. The organic acid ammonium salt can effectively remove the ions, oxides and other contaminants accumulated on the housing surface. After chemical cleaning, the surface of the centrifugal pump housing is roughened by sandblasting to improve the bonding force between the silane film and the housing. After sandblasting, the centrifugal pump housing is heated to 600℃ at a heating rate of 10℃ / min. In this invention, ammonium citrate or sodium metasilicate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing after silane pretreatment. The Fe ions in the rust on the housing surface are encapsulated in the chelating agent and become stable compounds with larger molecular weights, which can more effectively remove the ions, oxides and other contaminants accumulated on the surface.

[0058] The centrifugal pump casing, after silane pretreatment, undergoes plasma plating to deposit a coating on its surface. The plasma powder coating uses an alloy vacuum atomized powder, NiCoCrAlYHfSi, with a particle size of 32 μm, containing 55% Ni, 18% Co, 20% Cr, 6% Al, 0.2% Y, 0.5% Hf, and 0.3% Si. During the plasma plating process, the ratio of the centrifugal pump casing temperature T1 to the melting point temperature of the plasma powder T2 is maintained at T1 / T2 = 0.4. Within this range, surface diffusion-controlled deposition is achieved, easily forming a dense columnar crystalline coating and a closely packed fibrous structure on the centrifugal pump casing surface. The plasma powder material exhibits excellent oxidation and corrosion resistance, as well as good adhesion.

[0059] The plasma source employs arc discharge technology to generate high-energy electrons and ions, enabling plasma powder coating of the surface. Argon is used as the protective gas. The plasma discharge treatment time is no more than 5 minutes, the plasma operating voltage is 30 kV, the plasma operating frequency is 15 kHz, the plasma vacuum degree is controlled at 1000 Pa, the spraying power is 55 kW, and the protective gas flow rate is set to 55 L / min. In the plasma coating process of this invention, argon is used as the protective gas to dilute and control the plasma, thus avoiding gas contamination. On the other hand, argon, as an ionizing gas, provides protection for the easily oxidized centrifugal pump casing. The plasma coating technology used in this invention has low process cost, high deposition efficiency, and produces a relatively dense coating, making it suitable for industrial-scale production.

[0060] (3) The plasma-treated coating is modified by annealing. During the modification annealing process, the pressure inside the vacuum sintering furnace is controlled below 0.1 MPa. First, the temperature of the vacuum furnace is raised to 700℃ at a heating rate of 5℃ / min and held for 1.2h. Then, the temperature is raised to 1000℃ at a heating rate of 5℃ / min and held for 35min before annealing begins. The temperature is then uniformly annealed to 250℃ at a cooling rate of 5℃ / min for 100min. Finally, the centrifugal pump casing is allowed to cool naturally to room temperature with the furnace. During the modification annealing process, external hydrogen gas is introduced into the furnace to ensure that the furnace is filled with flowing hydrogen gas. In this invention, the centrifugal pump housing after plasma spraying is modified by annealing, which changes the structure of the sprayed coating from a layered mechanical bond to a metallurgical bond, improving the adhesion between the coating and the centrifugal pump housing, and reducing the oxygen content in the coating, thus significantly improving the corrosion resistance and oxidation resistance of the pump housing. Annealing the surface of the plasma sprayed coating makes the coating on the housing surface denser and reduces the oxygen content in the coating, thereby reducing the risk of oxidation of the centrifugal pump housing, which is an iron and aluminum casting.

[0061] This invention discloses a centrifugal pump. The centrifugal pump is treated using the plasma-sprayed metal casing preparation method of Example 2 to form a coating on its surface. Characterization tests on the prepared coating showed a BET result indicating a porosity of 3.5%, with the pores primarily composed of micropores ranging in size from 10 nm to 500 nm. The adhesion between the coating and the centrifugal pump casing was tested using an adhesion tester, and the results showed an adhesion strength close to 120 N / cm². 2 The target is to achieve 600 hours of salt spray testing and a corrosion resistance level of C4.

[0062] Example 3

[0063] Example 3 discloses a method for preparing a plasma-sprayed metal shell, comprising the following steps:

[0064] (1) The centrifugal pump casing is pretreated with silane. The silane pretreatment forms a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing. This silane film is uniform and durable. In the silane treatment solution, the solute component is 98 wt% trichloromethylsilane, the coupling agent is 2 wt% zirconium tetrabutyrate, and 0.3 wt% allyl alcohol polyether is added as a surfactant. The solvent is ethanol. The hydrolysis temperature in the silane treatment is 35℃, and the immersion time is 8 min. The coupling agent zirconium tetrabutyrate can catalyze the transcoating reaction and react with the carboxylic acid functional groups in the silane to form new bonds and enhance the adhesion of the coating. The surfactant allyl alcohol polyether reduces the silica content of the silane. The surface tension between the silane and the centrifugal pump casing promotes uniform distribution of the silane and enhances the adhesion of the silane coating to the surface. In the silane pretreatment process, this invention uses trichloromethylsilane with a concentration of 98 wt%, which can form a silane film on the surface of the centrifugal pump casing, improving the corrosion resistance and chemical resistance of the centrifugal pump. Especially in extremely corrosive environments, it reduces the corrosion of the casing by acidic substances in rainwater, avoids the use of traditional fluorosilanes, and reduces potential environmental damage. The use of organosilanes can form a silane film with a three-dimensional network structure on the surface of the centrifugal pump casing, which can improve the corrosion resistance of the centrifugal pump casing.

[0065] (2) Before plasma coating, 15wt% ammonium citrate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing. The organic acid ammonium salt can effectively remove the ions, oxides and other contaminants accumulated on the housing surface. After chemical cleaning, the surface of the centrifugal pump housing is roughened by sandblasting to improve the bonding force between the silane film and the housing. After sandblasting, the centrifugal pump housing is heated to 700℃ at a heating rate of 20℃ / min. In this invention, ammonium citrate or sodium metasilicate is used as a cleaning solution to chemically clean the surface of the centrifugal pump housing after silane pretreatment. The Fe ions in the rust on the housing surface are encapsulated in the chelating agent and become stable compounds with larger molecular weights, which can more effectively remove the ions, oxides and other contaminants accumulated on the surface.

[0066] The centrifugal pump casing, after silane pretreatment, undergoes plasma plating to deposit a coating on its surface. The plasma powder coating uses an alloy vacuum atomized powder, NiCoCrAlYHfSi, with a particle size of 42 μm, containing 60% Ni, 15% Co, 15% Cr, 8% Al, 0.6% Y, 1% Hf, and 0.4% Si. During the plasma plating process, the ratio of the centrifugal pump casing temperature T1 to the melting point temperature of the plasma powder T2 is maintained at T1 / T2 = 0.5. Within this range, surface diffusion-controlled deposition is achieved, easily forming a dense columnar crystalline coating and a closely packed fibrous structure on the centrifugal pump casing surface. The plasma powder material exhibits excellent oxidation and corrosion resistance, as well as good adhesion.

[0067] The plasma source employs arc discharge technology to generate high-energy electrons and ions, enabling plasma powder coating of the surface. Argon is used as the protective gas. The plasma discharge treatment time is no more than 5 minutes, the plasma operating voltage is 45kV, the plasma operating frequency is 20kHz, the plasma vacuum degree is controlled at 1500pa, the spraying power is 60kW, and the protective gas flow rate is set to 60L / min. In the plasma coating process of this invention, argon is used as the protective gas to dilute and control the plasma, thus avoiding gas contamination. On the other hand, argon, as an ionizing gas, provides protection for the easily oxidized centrifugal pump casing. The plasma coating technology used in this invention has low process cost, high deposition efficiency, and produces a relatively dense coating, making it suitable for industrial-scale production.

[0068] (3) The plasma-treated coating is modified by annealing. During the modification annealing process, the pressure inside the vacuum sintering furnace is controlled below 0.1 MPa. First, the temperature of the vacuum furnace is raised to 800℃ at a heating rate of 5℃ / min and held for 1.5h. Then, the temperature is raised to 1100℃ at a heating rate of 5℃ / min and held for 40min before annealing begins. The temperature is then uniformly annealed to 300℃ at a cooling rate of 10℃ / min for 120min. Finally, the centrifugal pump casing is allowed to cool naturally to room temperature with the furnace. During the modification annealing process, external hydrogen gas is introduced into the furnace to ensure that the furnace is filled with flowing hydrogen gas. In this invention, the centrifugal pump housing after plasma spraying is modified by annealing, which changes the structure of the sprayed coating from a layered mechanical bond to a metallurgical bond, improving the adhesion between the coating and the centrifugal pump housing, and reducing the oxygen content in the coating, thus significantly improving the corrosion resistance and oxidation resistance of the pump housing. Annealing the surface of the plasma sprayed coating makes the coating on the housing surface denser and reduces the oxygen content in the coating, thereby reducing the risk of oxidation of the centrifugal pump housing, which is an iron and aluminum casting.

[0069] This invention discloses a centrifugal pump. The centrifugal pump is treated using the plasma-sprayed metal casing preparation method described in Example 3 to form a coating on its surface. Characterization tests on the prepared coating showed a BET result indicating a porosity of 3.5%, with the pores primarily composed of micropores ranging in size from 10 nm to 500 nm. The adhesion between the coating and the centrifugal pump casing was tested using an adhesion tester, and the results showed an adhesion strength close to 120 N / cm². 2 The target is to achieve 600 hours of salt spray testing and a corrosion resistance level of C4.

[0070] Example 4

[0071] Example 4 is the same as Example 1, except for the different zirconium tetrabutyrate content. During the silane pretreatment process, the adhesion of coatings prepared with different zirconium tetrabutyrate contents as coupling agents was tested. As shown in Table 1, the results show that adding zirconium tetrabutyrate as a coupling agent can improve the adhesion of the coating, but when the content reaches 3 wt%, the performance is not significantly improved. Therefore, the content range of allyl alcohol polyether in this invention is 1–2 wt%.

[0072] Table 1. Effect of adding zirconium tetrabutyrate as a coupling agent on coating adhesion: Results of comparative experiments.

[0073] 0 33 1 41 2 41 3 42 4 41

[0074] Example 5

[0075] Example 5 is the same as Example 1, except that the allyl alcohol polyether content is different. During the silane pretreatment process, the adhesion and coating properties of the coatings prepared with different allyl alcohol polyether contents were first tested, as shown in Table 2. The results show that adding allyl alcohol polyether can significantly improve the adhesion and coating properties, while when the content reaches 0.4 wt%, there is no significant improvement in performance. Therefore, the allyl alcohol polyether content range is 0.2–0.3 wt%.

[0076] Table 2. Effects of adding allyl alcohol polyether as a surfactant on coating adhesion and uniformity (coating strength). Comparative experimental results.

[0077] 0 41 83 0.1 52 88 0.2 56 95 0.3 56 94 0.4 56 94

[0078] Subsequently, the performance of the coating prepared by adding 0.3 wt% allyl alcohol polyether as a surfactant to the silane pretreatment was tested, such as... Figure 6 As shown in the impedance Bode plot, the |Z| of the coating with the addition of surfactant is significantly greater than that of the coating without surfactant. This indicates that the addition of allyl alcohol polyether surfactant can modify the silane solution, increasing the polarization resistance R of the film and enhancing its corrosion resistance.

[0079] Example 6

[0080] Example 6 is the same as Example 1, except that the Hf element content of plasma spraying is different. Under standard conditions, NiCoCrAlYHfSi alloys with different Hf contents were tested to obtain the experimental results of the effect of plasma spraying Hf element content on the anti-oxidation performance of the coating, as shown in Table 3.

[0081] Table 3. Experimental results showing the effect of Hf element content on the antioxidant properties of plasma powder coating.

[0082] 0 72 79 360 0.5 87 97 420 1.0 87 99 420 1.5 87 97 420

[0083] Table 3 presents the experimental results of NiCoCrAlYHfSi alloys with different Hf contents under standard conditions. The results show that the addition of Hf to the alloy can improve the adhesion, oxidation resistance, and corrosion resistance of the coating after plasma spraying. Compared with the absence of Hf, the adhesion is improved by 21%, the oxidation time is extended by 15%, and the salt spray time is improved by 17%. When the Hf content is further increased to 1.5%, the performance of the coating does not change significantly. Therefore, the Hf addition range in this invention is 0.5–1.0 wt%.

[0084] Example 7

[0085] Example 7 is the same as Example 1, except that the ratio of the centrifugal pump housing temperature T1 to the plasma powder spraying melting point temperature T2 is different. The coating performance under different temperature ratios was tested, and Tables 4 and 5 were obtained.

[0086] Table 4. Effect of the ratio of centrifugal pump casing temperature T1 to plasma powder coating melting point temperature T2 on coating performance.

[0087] 0.1 55 92 0.2 74 94 0.3 87 95 0.4 86 95 0.5 86 94 0.6 86 83

[0088] Table 4 presents the experimental results of coating performance under different ratios of centrifugal pump casing temperature T1 to plasma powder spraying melting point temperature T2. The results show that when T1 / T2 increases from 0.1 to 0.3, the coating adhesion significantly improves, and the coverage remains stable at around 95%. However, when the T1 / T2 temperature is further increased to 0.6, the coating coverage decreases significantly. Therefore, the reasonable temperature range for T1 / T2 in this invention is 0.3–0.5.

[0089] Table 5. Test results of coating density and uniformity under different centrifugal pump casing temperatures (T1) and plasma spraying melting point temperatures (T2).

[0090] 0.2 29 31 8.50％ 0.3 12 10 4.57％ 0.4 13 10 4.63％ 0.5 12 11 4.49％ 0.6 41 37 9.42％

[0091] The structures of coatings prepared under different centrifugal pump housing temperatures T1 and plasma powder spraying melting point temperatures T2 were characterized. The results are shown in Table 5. It can be seen that the minimum size of the structural unit and the center distance between adjacent units of the coating prepared with a T1 / T2 ratio of 0.3 to 0.5 are significantly smaller than those of coatings prepared with other T1 / T2 ratios, and the porosity is also significantly lower. At this time, the uniformity and density of the coating are better. Therefore, the temperature range of T1 / T2 of 0.3 to 0.5 is better in this invention.

[0092] Example 8

[0093] Example 8 is the same as Example 1, except that the annealing method is different. The coating properties before and after annealing were tested, as shown in Table 6. The results show that after annealing modification of the coating after silane treatment and plasma spraying, the oxygen content of the annealed coating was reduced by 77.2%, the time for the first oxidation spot to appear was extended by 25.8%, the coverage was slightly improved, and the adhesion was increased by 35.6%. This indicates that annealing modification can significantly improve the adhesion between the coating and the centrifugal pump housing, and reduce the oxygen content in the coating, thus significantly improving the corrosion resistance and oxidation resistance of the pump housing.

[0094] Table 6 shows the effect of annealing on coating oxygen content, coverage, and adhesion.

[0095]

[0096] Example 9

[0097] Example 9 is the same as Example 1, except that different annealing heating rates are used during the annealing process, and the coating structures prepared under different annealing heating rates are tested. Table 7 shows the test results of the coating structures under different annealing methods.

[0098] Table 7. Test results of coating structure under different annealing methods

[0099] none 13 10 4.63％ 5 9 7 3.12％ 10 12 10 4.30％ 15 12 9 4.21％

[0100] The coatings prepared at different heating rates for annealing treatment were characterized structurally, and the results are shown in Table 7. It can be seen that after annealing, the minimum size of the coating structural units, the center distance between adjacent units, and the porosity all decreased. When the heating rate was 5℃ / min, the coating structural units and porosity were optimal, and the density and uniformity of the coating surface were best at this point. Therefore, the heating rate in step (3) of this invention is set to 5℃ / min during the annealing treatment.

[0101] Example 10

[0102] Example 10 is the same as Example 1, except that different annealing cooling rates are used during the annealing process, and the coating structures prepared under different annealing cooling rates are tested. Table 8 shows the test results of the coating structure under different cooling rates during the annealing process.

[0103] Table 8. Test results of coating structure under different cooling rates during annealing.

[0104] Natural cooling 15 16 4.58％ 5 9 7 3.12％ 10 9 9 3.39％ 15 17 15 4.77％

[0105] During the annealing process, the heating rate was fixed at 5℃ / min, and the microstructure of coatings prepared at different cooling rates was characterized. The specific results are shown in Table 8. It can be seen that when the cooling method is changed from natural cooling to fixed-rate cooling, and the cooling rate is in the range of 5 to 10℃ / min, the microstructure of the coating is compact and dense, and the surface porosity is low. When the cooling rate is further increased to 15℃ / min, the minimum size of the microstructure unit and the center distance between adjacent units of the coating become larger, the unit structure becomes loose, the surface pores increase, and the coating performance decreases. Therefore, the heating rate in step (3) of this invention is taken as 5 to 10℃ / min during the annealing treatment.

[0106] The preferred embodiments of the present invention have been described in detail above, but the design concept of the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solution of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for preparing a plasma-sprayed metal shell, characterized in that, Includes the following steps: (1) The metal shell is pretreated with silane, and the silane pretreatment forms a silane film with a three-dimensional network structure on the surface of the metal shell; In the silane-treated solution, the solute component is The trichloromethylsilane, with the coupling agent being... Zirconium tetrabutyrate, added Allyl alcohol polyether is used as a surfactant, and ethanol is used as the solvent; the hydrolysis temperature in silane treatment is... The dipping time is ; (2) Plasma plating is performed on the metal shell after silane pretreatment to deposit a coating on the surface of the metal shell, forming a columnar crystalline coating and a densely packed fibrous structure; the plasma powder spraying uses alloy vacuum atomized powder. Ni content is Co is The Cr content is Al content is The Y content is Hf content is The Si content is ; (3) The plasma-treated coating is modified by annealing to change the structure of the sprayed coating from a layered mechanical bond to a metallurgical bond; during the modification annealing process in step (3), the pressure inside the vacuum sintering furnace is controlled at... The vacuum furnace temperature is first raised to a certain level at a certain heating rate. Insulation Then continue heating at the same rate until... ,Keep Then begin annealing; The cooling rate begins to anneal at a uniform rate. to Finally, the metal outer shell naturally cools to room temperature along with the furnace.

2. The method for preparing a plasma-sprayed metal shell according to claim 1, characterized in that: Before plasma coating in step (2), first use Ammonium citrate was used as a cleaning solution to chemically clean the surface of the metal casing. After chemical cleaning, the surface of the metal casing was roughened by sandblasting. After sandblasting, the metal casing was heated to a certain temperature. The heating rate is .

3. The method for preparing a plasma-sprayed metal shell according to claim 1, characterized in that: During the plasma plating process in step (2), the temperature of the metal casing is maintained. With plasma powder coating The range of melting point temperatures is: .

4. The method for preparing a plasma-sprayed metal shell according to claim 1, characterized in that: The plasma discharge treatment time in step (2) shall not exceed [a certain value]. The plasma operating voltage is The plasma operating frequency is Plasma vacuum level controlled at Spraying power is The protective gas flow rate is set to .

5. The method for preparing a plasma-sprayed metal shell according to claim 1, characterized in that: In step (2), the particle size of the plasma sprayed powder is... .

6. A centrifugal pump, characterized in that, The metal casing of a centrifugal pump is processed using the plasma-sprayed metal casing preparation method according to any one of claims 1 to 5 to form a coating on the surface.

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