An anti-cavitation surface structure and a method of making the same

Abstract

The application discloses a novel anti-cavitation surface structure and a preparation method thereof. The anti-cavitation surface structure can change the wetting degree of a material surface, reduce gas nuclei near a liquid-solid contact surface, inhibit cavitation and cavitation erosion processes, and also reduce the damage of micro-jets to the material in the cavitation erosion process. The anti-cavitation surface structure layer is composed of a surface construction layer and a substrate. The working mechanism is as follows: firstly, the construction can change the wetting degree of the material surface, so that the gas nuclei near the liquid-solid contact surface are reduced, thereby slowing down the cavitation and cavitation erosion processes; secondly, the incident kinetic energy of the micro-jets in the effective construction area is consumed in the form of friction, thereby reducing the damage of the micro-jets to the material substrate. The application can effectively slow down the cavitation erosion process, weaken the influence of the micro-jets on the material substrate in the cavitation erosion process, and effectively resist the damage of the cavitation erosion to the material surface.

Description

Technical Field

[0001] This invention relates to industrial fields such as shipbuilding, water conservancy, and micro-machining, and specifically to an anti-cavitation surface structure layer and its preparation method. Background Technology

[0002] In today's era of industrial modernization, marine exploration is a crucial means of obtaining oil and natural gas, thus placing high demands on the performance and service life of marine vessels such as oil tankers and liquefied gas carriers. At high-speed liquid-solid contact surfaces, the influence of temperature and pressure causes the liquid near the contact surface to vaporize, generating bubbles. As these bubbles grow and collapse, they eventually disintegrate, producing microjet streams. These microjet streams continuously impact the material surface, ultimately causing damage and leading to the failure of components—this is cavitation erosion damage. Cavitation erosion damage frequently occurs in flow-through components such as propellers and impellers, severely impairing the service life of marine vessels and hydroelectric equipment, and jeopardizing navigational safety. The prevention and research of cavitation erosion damage has always been a key research area for scholars both domestically and internationally. my country invests hundreds of millions of yuan annually in the prevention and research of cavitation erosion damage, demonstrating its importance. This not only relates to my country's industrial modernization process but also showcases the technological level of my country's marine military equipment. Summary of the Invention

[0003] This invention addresses the cavitation erosion problem in flow-through components of marine vehicles. To improve the cavitation resistance of components such as propellers and impellers, an anti-cavitation surface structure is proposed. This structure alters the surface wettability of the material, reduces gas nuclei near the liquid-solid interface, suppresses cavitation and cavitation erosion processes, and reduces the damage caused by microjets during cavitation erosion. The anti-cavitation surface structure consists of a surface building layer and a substrate. Its mechanism of action is as follows: First, the structure alters the surface wettability of the material, reducing gas nuclei near the liquid-solid interface, thereby slowing down cavitation and cavitation erosion processes. Second, in the effective building region, the incident kinetic energy of the microjets is dissipated through friction, thus reducing the damage of the microjets to the material substrate. This invention effectively slows down the cavitation erosion process and weakens the impact of microjets on the material substrate during cavitation erosion, thereby effectively resisting the damage of cavitation erosion to the material surface.

[0004] At high-speed liquid-solid contact surfaces, the liquid near the contact surface vaporizes due to the influence of temperature and pressure, generating bubbles. As these bubbles grow and collapse, they eventually burst, producing microjets. These microjets continuously impact the material surface, ultimately causing damage and leading to the failure of components. Therefore, slowing down the cavitation erosion process and reducing the damage caused by microjets are effective means to prevent cavitation erosion damage.

[0005] The aforementioned surface structure layer is a micron-level surface construction, therefore any size component can serve as a substrate, resulting in a large effective construction area. Furthermore, research indicates that the microjets are several micrometers in size; thus, each surface microstructure can provide an effective frictional loss distance for the microjets, fully dissipating their kinetic energy and reducing the damage caused by the microjets to the materials.

[0006] The surface structure layer can significantly change the wettability of the material surface, increase the hydrophilicity of the material, reduce the number of gas nuclei near the liquid-solid interface, slow down the cavitation and cavitation erosion process, and thus enhance the material's resistance to cavitation erosion.

[0007] To achieve the aforementioned anti-cavitation process, the technical solution adopted by the anti-cavitation surface structure of this invention is as follows:

[0008] (1) The cavitation-resistant surface structure comprises two parts: a surface building layer and a substrate;

[0009] (2) The surface building layer in the anti-cavitation surface structure can change the surface wettability of the material, thereby reducing the number of gas nuclei near the liquid-solid interface.

[0010] (3) The effective construction area in the anti-cavitation surface structure can consume the incident kinetic energy of the microjets in the form of friction, thereby reducing the damage of the microjets to the material substrate.

[0011] (4) The anti-cavitation surface structure is arranged on the flow-through components that are easily damaged by cavitation;

[0012] (5) The periodic spacing S of the surface micro-structure units of the anti-cavitation surface structure is 40 μm;

[0013] (6) The surface micro-building unit of the anti-cavitation surface structure is a sector with a central angle α of 45°, which is deflected downward by 45° with the center as the deflection point, wherein the radius R of the sector is 15μm.

[0014] The aforementioned anti-cavitation surface structure layer is placed in areas of flow-through components such as propellers and impellers that are susceptible to cavitation damage.

[0015] The substrate refers to important flow-through components in marine vehicles or related water conservancy and hydropower equipment that are susceptible to cavitation damage, such as propellers, valve cores, and impellers.

[0016] This invention also proposes a method for preparing the above-mentioned novel cavitation erosion resistant surface structure, comprising the following steps:

[0017] S1 pre-treats the material; the material of the flow-through components to be processed is annealed to eliminate the stress introduced by cutting, rolling and other processes during machining. The annealed material is then ground, polished, and cleaned, awaiting further processing. For example, for the QAL-10-5-5 nickel-aluminum bronze alloy commonly used in the marine field, annealing is performed at 800℃ for 2 hours, followed by furnace cooling to room temperature. The surface is then ground with 300-1800 grit sandpaper, polished with W2-grit diamond polishing compound, and then ultrasonically cleaned with a 99.5% alcohol solution. After completion, it is dried and stored for later use.

[0018] S2 Fix the workpiece; The material to be used is installed on the robotic arm. By writing the robotic arm control program, the robotic arm that fixes the material can be adjusted to realize the machining of complex curved surfaces.

[0019] S3 adjusts the laser parameters; the material to be processed is placed in the laser action area, and the laser impact parameters are adjusted to generate a high-repetition-rate, high-energy, short-pulse laser pulse. The shape of the laser processing can be controlled by adjusting parameters such as laser power, scanning speed, and spot size. For nickel-aluminum bronze alloy, the laser impact parameters are: picosecond laser energy density 2.01 J / cm². 2 The scanning speed is 200 mm / s, the laser wavelength is 1064 nm, the laser pulse width is 13 ps, the laser spot diameter is 20 μm, the motion platform resolution is 0.01 mm, and the repetition frequency is adjustable between 0.4 and 10 MHz. Finally, the surface processing of the material is achieved by operating the rotation and translation of the robotic arm.

[0020] S4 laser loading: The laser shock equipment is activated, and the laser emitted by the laser is focused onto the workpiece through an optical system composed of mirrors, focusing mirrors, etc. By utilizing the nonlinear interaction between ultrashort pulse lasers and materials, resolution exceeding the diffraction limit can be achieved, and various complex shapes can be processed from materials through computer scanning and design.

[0021] The beneficial effects of this invention are:

[0022] 1. It has good economic benefits; the current mainstream anti-cavitation methods mainly include the preparation of new high-performance materials and the use of coating technology, all of which require a lot of time and money, and the economic benefits are not significant.

[0023] 2. It will not introduce other unknown factors that may damage the material; for example, coating technology, although coatings can resist cavitation damage, some studies have pointed out that coatings may introduce additional electrochemical corrosion, which will exacerbate the damage to the material.

[0024] 3. By constructing surfaces on areas prone to cavitation damage, the cavitation and cavitation erosion processes can be effectively slowed down, reducing the damage to the material from microjets and thus improving the material's resistance to cavitation erosion.

[0025] 4. This invention uses an anti-cavitation surface structure, which can effectively protect the substrate material and improve the service life of important flow components. Attached Figure Description

[0026] Figure 1 This is a top view of the anti-cavitation texture structure on the surface of the component.

[0027] Figure 2 This is a schematic cross-sectional view of the anti-cavitation texture structure on the surface of the component.

[0028] Figure 3 This is a schematic diagram of the impeller structure in an embodiment of the present invention.

[0029] 1. Leaf;

[0030] Figure 4 This is a schematic diagram of the volute structure according to an embodiment of the present invention.

[0031] The components include: 1. outer wall of the volute; 2. bottom ring; 3. seat ring; 4. inner wall of the volute. Detailed Implementation

[0032] The invention will now be further described with reference to the accompanying drawings.

[0033] like Figure 1-2 The diagram shows a top view and a cross-sectional view of an anti-cavitation erosion surface structure. The anti-cavitation erosion surface structure comprises a surface building layer and a substrate. Micro-building units are disposed on the surface building layer, with a periodic spacing S of 40 μm. Each micro-building unit on the surface of the surface building layer is formed by a sector with a central angle α of 90°, deflected downwards by an angle θ of 45° (the center of the sector is the deflection point), where the radius R of the sector is 15 μm. This building unit can alter the wettability of the material surface, reducing gas nuclei near the liquid-solid interface, thereby slowing down cavitation and erosion processes. Furthermore, within the effective building region, the incident kinetic energy of the microjets is dissipated through friction, thus reducing the damage to the material substrate caused by the microjets.

[0034] The embodiments of the present invention also include a method for preparing the above-mentioned novel cavitation erosion resistant surface structure, comprising the following steps:

[0035] S1 pre-treats the material; the material of the flow-through components to be processed is annealed to eliminate the stress introduced by cutting, rolling and other processes during machining. The annealed material is then ground, polished, and cleaned, awaiting further processing. For example, for the QAL-10-5-5 nickel-aluminum bronze alloy commonly used in the marine field, annealing is performed at 800℃ for 2 hours, followed by furnace cooling to room temperature. The surface is then ground with 300-1800 grit sandpaper, polished with W2-grit diamond polishing compound, and then ultrasonically cleaned with a 99.5% alcohol solution. After completion, it is dried and stored for later use.

[0036] S2 Fix the workpiece; The material to be used is installed on the robotic arm. By writing the robotic arm control program, the robotic arm that fixes the material can be adjusted to realize the machining of complex curved surfaces.

[0037] S3 adjusts the laser parameters; the material to be processed is placed in the laser action area, and the laser impact parameters are adjusted to generate a high-repetition-rate, high-energy, short-pulse laser pulse. The shape of the laser processing can be controlled by adjusting parameters such as laser power, scanning speed, and spot size. For nickel-aluminum bronze alloy, the laser impact parameters are: picosecond laser energy density 2.01 J / cm². 2 The scanning speed is 200 mm / s, the laser wavelength is 1064 nm, the laser pulse width is 13 ps, the laser spot diameter is 20 μm, the motion platform resolution is 0.01 mm, and the repetition frequency is adjustable between 0.4 and 10 MHz. Finally, the surface processing of the material is achieved by operating the rotation and translation of the robotic arm.

[0038] S4 laser loading: The laser shock equipment is activated, and the laser emitted by the laser is focused onto the workpiece through an optical system composed of mirrors, focusing mirrors, etc. By utilizing the nonlinear interaction between ultrashort pulse lasers and materials, resolution exceeding the diffraction limit can be achieved, and complex structural shapes can be processed through computer scanning and design.

[0039] Example 1:

[0040] like Figure 1 and Figure 3 As shown, the cavitation erosion-resistant surface structure consists of two parts: a surface building layer and a substrate. Substrate 1 represents the impeller blades (shaded area), and this surface building layer is applied to the surface of the blades, which are susceptible to cavitation erosion damage. During implementation, water was impacted and passed through the impeller; tests yielded the following results:

[0041] (1) The building block can change the wettability of the material surface and slow down the cavitation and erosion process.

[0042] (2) The cavitation damage conditions of the constructed surface and the unconstructed surface are different, and the constructed surface shows obvious resistance to cavitation erosion.

[0043] (3) Comparison between the constructed sample and the reference sample revealed that the constructed sample could significantly resist the impact of microjets, and the predicted resistance to cavitation erosion was improved by 11.14%.

[0044] Example 2:

[0045] like Figure 1 and Figure 4 As shown, the surface structure consists of two parts: a surface building layer and a substrate. 1 represents the outer shell of the volute, 2 is the bottom ring, 3 is the seat ring, and 4 is the shaded area representing the inner wall of the volute. This surface building layer is applied to the surface of the inner wall of the volute, which is susceptible to cavitation damage. During implementation, water was impacted and passed through the volute; tests showed that:

[0046] (1) The structure can change the wettability of the material surface and slow down the cavitation and erosion process.

[0047] (2) The damage to the inner wall of the volute after surface construction is significantly improved compared to before construction. The cavitation suppression rate of the surface structure reaches 9.09%, and the ability to resist frontal jet impact is improved by 38.57%.

[0048] As can be seen from this embodiment, the present invention can change the wettability of the material surface, reducing the number of gas nuclei near the liquid-solid interface, thereby slowing down the cavitation and cavitation erosion process; in addition, within the effective construction region, the incident kinetic energy of the microjets is consumed in the form of friction, thereby reducing the damage of the microjets to the material substrate. The present invention can significantly improve the cavitation erosion resistance of flow components.

[0049] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent methods or modifications that do not depart from the technology of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cavitation-resistant surface structure, characterized in that, It includes a surface building layer and a substrate; the surface building layer is located on the substrate; the surface building layer is formed by arranging a plurality of micro-building units, and the micro-building units are fan-shaped pits; The horizontal surface of the micro-structure unit fan-shaped pit is fan-shaped, and the cavity of the micro-structure unit fan-shaped pit is formed by deflecting downward with the center of the fan shape as the deflection point.

2. The cavitation-resistant surface structure according to claim 1, characterized in that, The central angle α of the sector is 45° and the radius R is 15μm.

3. The cavitation-resistant surface structure according to claim 1, characterized in that, The downward deflection angle is 45°.

4. The cavitation-resistant surface structure according to claim 1, characterized in that, The downward deflection is a downward deflection perpendicular to the base.

5. The cavitation-resistant surface structure according to any one of claims 1-4, characterized in that, The micro-building units are arranged periodically.

6. The cavitation-resistant surface structure according to claim 5, characterized in that, The periodic spacing S of the arrangement is 40 μm.

7. The cavitation-resistant surface structure according to claim 1, characterized in that, The substrate includes flow-through components in marine vehicles or hydroelectric equipment that are susceptible to cavitation damage.

8. A method for preparing the cavitation-resistant surface structure as described in claim 1, characterized in that, Includes the following steps: S1 pre-treats the material; annealing the material of the flow-through components to be processed to eliminate the stress introduced by cutting and rolling processes during machining; then grinding, polishing and cleaning the annealed material, waiting for subsequent processing; S2 Fix the workpiece; Install the material to be used in the flow component onto the robotic arm, and adjust the robotic arm that fixes the material by writing the robotic arm control program to realize the machining of complex curved surfaces; S3 adjusts the laser parameters; the material to be used is placed in the laser action area, the laser impact parameters are adjusted to generate a high repetition frequency, high energy, short pulse laser pulse, the laser processing shape can be controlled by adjusting the laser power, scanning speed, and spot size parameters, and the surface processing of the material can be achieved by operating the rotation and translation of the robotic arm; S4 laser loading; the laser shock equipment is started, and the laser emitted by the laser is focused on the workpiece of the flow component through the optical system. The nonlinear interaction between the ultrashort pulse laser and the material is used to realize the processing and preparation of the anti-cavitation surface structure.

9. The method for preparing an anti-cavitation surface structure according to claim 8, characterized in that, In S1, the flow-through component is a nickel-aluminum bronze alloy, which needs to be annealed at 800 ℃ for 2 h, and then cooled to room temperature in the furnace; the surface is ground with 300 to 1800 grit sandpaper, then polished with W2 grit diamond polishing agent, and then ultrasonically cleaned with 99.5% alcohol solution. After completion, it is dried and stored for later use. In S3, the current-carrying component is made of nickel-aluminum bronze alloy, and the laser shock parameters need to be set to: picosecond laser energy density 2.01 J / cm². 2 The scanning speed is 200 mm / s, the laser wavelength is 1064 nm, the laser pulse width is 13 ps, the laser spot diameter is 20 μm, the motion platform resolution is 0.01 mm, and the repetition frequency is adjustable between 0.4-10 MHz.

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