Submerged water jet surface strengthening process for improving erosion resistance of metal surface

Abstract

The invention discloses a submerged water jet surface strengthening process for improving the erosion resistance of a metal surface, which comprises the following steps: carrying out heat treatment on a metal matrix, designing and processing flat plate, cylinder and blade type structure samples for erosion and static load erosion, carrying out stress relief annealing treatment, eliminating residual stress in the sample processing process, and carrying out water jet surface strengthening. A clamp and a four-jaw chuck are designed according to sample structure size parameters, a bench vice is combined to install the sample, workpiece strengthening parameters are regulated and controlled, metal abrasive particles and high-pressure water jet flow are mixed and then act on the metal surface, surface strengthening of the sample to be strengthened is achieved, a plastic deformation layer is introduced to the surface of the workpiece, and strengthening is completed. According to the method, the samples of various structures such as flat plates, cylinders and blades can be strengthened, the erosion resistance of the metal matrix component is remarkably improved, meanwhile, the surface quality is improved, the fatigue resistance is improved, the service life of the metal matrix component is prolonged, meanwhile, the time and economic cost is reduced, and the method has wide industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of material surface strengthening, and in particular relates to a submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces. Background Art

[0002] In real-world dusty environments, high-speed airflow during aircraft flight carries large amounts of sand and dust. Consequently, aircraft engine compressor blades are subject to erosion by these dust particles, causing surface damage that reduces equipment efficiency, shortens service life, and increases operating costs. Most aircraft engine blades are constructed of titanium alloy, which has poor erosion resistance. Previously, methods such as applying protective coatings and replacing the base material could be used to improve component erosion resistance, but these methods were time-consuming and costly.

[0003] Studies have shown that surface strengthening is widely used in the field of metal surface modification as an effective process. After surface strengthening, plastic deformation can be generated on the surface of metal components, compressive residual stress can be introduced, and grain refinement can be achieved, thereby inhibiting the occurrence of fatigue cracks and improving the service life of the components. There are many ways to strengthen the surface, such as shot peening, laser strengthening, pure water jet strengthening, and abrasive water jet strengthening. Compared with coating and replacement of the base material, water jet strengthening has the advantages of high surface quality of the strengthened components, low noise, environmental protection, and the ability to process components with complex geometric structures.

[0004] Therefore, it is necessary to propose a strengthening process that reduces time and economic costs and can improve the erosion resistance of titanium alloy blades. Summary of the Invention

[0005] The purpose of the present invention is to provide a submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces, thereby solving the problems of high time and economic costs in the prior art metal surface strengthening processes.

[0006] In order to solve the above problems, the present invention adopts the following technical solutions: According to a first aspect of the present invention, a submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces is provided, comprising the following steps: 1) heat treating a metal substrate at a temperature of 960±40°C, holding for 250±30min, and then air cooling, wherein the treated sample is composed of α phase and β phase; 2) processing the heat-treated metal substrate into a sample to be strengthened according to structural and dimensional requirements and polishing the sample to remove surface burrs, and making the surface roughness of the sample Ra=0.4±0.1μm after polishing; 3) performing stress relief annealing on the sample to be strengthened, heating the sample to 560°C in a furnace for 120±30min, holding the temperature for 120±30min, and then cooling the sample in the furnace for 18±2h; 4) ultrasonically cleaning the sample with anhydrous ethanol, fixing the sample to be strengthened with a clamp or a bench vise after cleaning, and moving the robotic arm so that the nozzle and the sample ensure a certain target 5) Pressurize the atmospheric water through a booster pump. Adjust the jet pressure by changing the operating power of the booster pump. Use an electronic sand control valve to control the abrasive flow entering the nozzle. Control the traverse speed of the robotic arm and the interval between adjacent tracks through a program so that the metal abrasive particles mix with the high-pressure water jet and act on the metal surface, thereby strengthening the surface of the specimen to be strengthened and introducing a plastic deformation layer on the workpiece surface. 6) After removing the robotic arm, remove the specimen from the fixture or bench vise.

[0007] Preferably, in step 4), the robotic arm is moved so that the target distance is 5-20 mm.

[0008] Preferably, in step 5), the metal abrasive particles used are 340 stainless steel spherical particles with an average particle size of 135±35 μm.

[0009] Preferably, in step 5), the jet pressure is 100-160 MPa, the abrasive flow rate is 5-25%, the traverse speed is 2-11 mm / s, and the track interval is 0.05-0.2 mm.

[0010] Preferably, the sample to be strengthened includes: a flat plate structure, a cylindrical structure and a blade structure.

[0011] Furthermore, in the step 1), the heat treatment temperature is 960° C., and the mixture is kept at this temperature for 250 minutes and then air-cooled.

[0012] Furthermore, in step 2), the surface roughness of the sample after processing is Ra=0.4±0.1 μm.

[0013] Furthermore, in step 3), the temperature is raised to 560° C. in the furnace for 120 minutes, then kept at that temperature for 120 minutes, and finally cooled in the furnace for 18 hours.

[0014] Preferably, in step 4), for the flat-plate structure specimen, a bench vise is used to clamp it. After strengthening one side, the specimen is removed and turned over, and the other side is facing upward and fixed, thereby achieving double-sided strengthening; for the cylindrical structure specimen, a fixture is used to clamp it. After clamping, the fixture is fixed with a four-jaw chuck. The rotation of the four-jaw chuck is combined with the movement of the robotic arm to achieve the strengthening of the outer surface of the entire cylindrical structure specimen; for the blade structure specimen, a fixture is used to clamp it so that a certain blade edge surface faces upward. After clamping, the fixture is fixed with a bench vise. After completing the strengthening of the blade edge surface, the strengthening of the remaining blade edge surfaces is achieved by reversing the direction of the fixture.

[0015] Preferably, the metal matrix is a titanium alloy. However, it should be understood that the present invention is not limited to titanium alloy surface strengthening.

[0016] The submerged water jet surface strengthening process is carried out using a submerged abrasive water jet strengthening device, which includes: an automatic feeding system, a stainless steel water tank, a water outlet, a filter, a robotic arm, a nozzle, a marble bottom plate, a booster pump, a jet control system, and a robotic arm control system; the sample to be strengthened is clamped by a bench vise or a clamp, the bench vise is clamped in the gap of the marble floor, and the clamp is clamped by a four-jaw chuck; after the sample is clamped, the valve of the water inlet pipe is opened to allow water to be introduced into the stainless steel water tank until the sample is submerged; dried stainless steel abrasive particles can be added to the automatic feeding system, and the automatic feeding system is connected to the abrasive inlet of the nozzle via a pipeline, and an air compressor provides the conveying power for it; the booster pump is connected to the high-pressure water inlet of the nozzle via a pipeline, and the high-pressure jet and abrasive particles are mixed inside the nozzle, sprayed out through a tungsten steel sand pipe, and act on the sample surface underwater.

[0017] Preferably, a water outlet is provided on the side of the stainless steel water tank and connected to the water outlet pipeline, and a filter is provided on the water outlet side. After strengthening is completed, the water outlet valve is opened and the abrasive particles automatically sink to the bottom. The abrasive particles that sink to the bottom can be recovered and dried and reused.

[0018] It should be known that in the previous shot peening or water jet strengthening processes, most of the samples were fixed with a bench vise used in machining, but this fixing method is only suitable for samples or components with relatively regular geometric structures, such as flat plates. However, actual components often have complex geometric structures, such as rotating cylinders, complex blade surfaces, etc. Therefore, the present invention introduces a four-jaw chuck, drives the rotation of the four-jaw chuck by a motor, uses the chuck to clamp the fixture, and uses the fixture to clamp the rotating cylinder. By writing a robot arm trajectory program code, the strengthening processing of the entire outer surface of the cylinder is achieved. However, blade-like structure samples require strengthening on all four sides, so another type of fixture is designed to clamp the sample, thereby ensuring that the nozzle is perpendicular to the blade edge surface. The robot arm trajectory program code for flat plate strengthening can be used, thereby avoiding the writing of a large amount of complex code, simplifying the strengthening process, and improving the efficiency of strengthening.

[0019] Furthermore, a six-degree-of-freedom robotic arm is provided above the rear of the water tank, and the straight nozzle is fixed to the robotic arm by bolts.

[0020] Furthermore, the submerged abrasive water jet strengthening equipment also includes a bench vise for fixing the erosion and static load erosion flat plate specimens.

[0021] Furthermore, the submerged abrasive water jet strengthening equipment also includes a four-jaw chuck and fixture for securing eroded and statically eroded cylindrical specimens. The four-jaw chuck holds the fixture, which is divided into two parts and connected by bolts. The cylindrical specimen to be strengthened is placed in the fixture and locked. The fixture cooperates with the chuck and turntable to achieve rotational strengthening of the cylindrical specimen.

[0022] Furthermore, the submerged abrasive waterjet strengthening equipment also includes a bench vise and fixture for securing eroded and static eroded blade specimens. The four-jaw chuck holds the fixture, which is divided into two parts and connected by bolts. The blade specimen to be strengthened is placed in the fixture and locked. The fixture, in conjunction with the bench vise, performs strengthening processing on one side of the blade specimen.

[0023] Furthermore, the step 5) includes: Step S51: Fix the sample to be strengthened using a fixture with a chuck and a bench vise, turn on the water inlet switch and wait for 30-60 minutes to fully immerse the sample in water, and control the water temperature at 25°C; Step S52: Fix the straight nozzle on the robotic arm, and control the distance between the nozzle and the workpiece surface to be 5-20 mm by moving the robotic arm up and down, so that the straight nozzle is immersed in water and perpendicular to the workpiece surface; Step S53: using a booster pump to deliver normal pressure water to the straight nozzle mixing cavity, and adjusting the booster pump to control the jet pressure to be 100-160 MPa; Step S54: Using the jet control system to adjust the electronic sand control valve to control the abrasive flow rate at 5-25%; Step S55: Using the teaching pendant of the robot arm to change different lateral movement speeds, the lateral movement speed of the robot arm is controlled to be 2-11 m / s; Step S56: Generate corresponding reinforcement tracks using the Matlab program, and control the interval between adjacent tracks to be 0.05-0.20 mm; Furthermore, a drain outlet is provided at the bottom of the water tank, and the water flow at the outlet is regulated by a valve. A water inlet is provided at the top of the water tank.

[0024] Furthermore, a drain outlet and a filter screen are provided at the bottom of the water tank to reduce the outflow of abrasive particles.

[0025] According to the second aspect of the present invention, a metal surface erosion-resistant water jet strengthening layer prepared by the above-mentioned submerged water jet surface strengthening process is provided, the thickness of the plastic deformation layer on the surface of the metal substrate reaches 20-35μm, and the erosion resistance is greatly improved.

[0026] It should be known that water jet technology is most commonly used in cutting, cleaning and other fields. In recent years, it has gradually been used in metal strengthening processing to improve its fatigue life. The materials of aircraft engine compressor blades, such as titanium alloys, not only bear alternating loads, but also need to withstand the impact of dust or particles when the blades rotate, resulting in erosion problems. At present, the main solution to the erosion problem is coating technology. Coating technology itself has certain problems, such as brittle coating, weak bonding force, which may cause peeling and high cost. Secondly, water jet technology is generally divided into non-submerged and submerged types. The former is easy to implement, but there are problems such as jet splashing and noise. Submerged water jets were subsequently developed, but this method will generate a large number of cavitation bubbles underwater, which will cause the material surface to withstand cavitation collapse pressure and peeling. It can be seen that, to date, there are still various problems with the application of water jet technology in metal strengthening processing.

[0027] It should also be known that the current field of metal anti-erosion and wear technology mainly uses coating technology. On the one hand, the anti-erosion effect of the coating when the solid particles are between 60° and 90° is close to that of the metal matrix. On the other hand, the compressor blades in aircraft engines are often subjected to alternating loads and lead to fatigue failure. The coating technology only changes the anti-erosion and wear performance, and has no direct improvement on the fatigue performance of the metal matrix.

[0028] In order to solve the various problems existing in the above-mentioned prior art, the inventors of the present invention were inspired by shot peening technology and tried for the first time to introduce tiny metal abrasive particles, mix them with high-pressure jets and act on the metal surface. On the one hand, the metal abrasive particles will play a role similar to shot peening strengthening, and on the other hand, they will consume the energy of the high-pressure jets to reduce the generation of cavitation bubbles. Since they are submerged in water, the noise generated is very small. Accordingly, the present invention proposes for the first time a submerged abrasive water jet strengthening method. By regulating the process parameters and combining the erosion test results, a set of process methods is formed, which is applied to metal substrates not limited to titanium alloys, and can effectively improve their erosion resistance. The present invention can reach several hundred MPa by introducing compressive residual stress into the surface layer of the metal material. Existing studies have shown that compressive residual stress can significantly inhibit crack initiation and expansion, thereby increasing the fatigue life of the metal material. At the same time, the surface hardness is increased, so that the overall performance is improved.

[0029] Based on this, the present invention proposes a submerged abrasive water jet strengthening process method for the erosion resistance of titanium alloy specimens, which includes: 1) firstly heat treating the raw materials; 2) processing the heat-treated raw materials according to size and polishing the processed specimens; 3) then performing stress relief annealing treatment; 4) then determining the fixture and chuck structure dimensions based on the specimen structural dimension parameters to ensure that the specimen is completely submerged in water; 5) finally performing submerged abrasive water jet strengthening on the processed specimens.

[0030] It should be understood that the key inventive aspects of the present invention lie primarily in steps 4) and 5). These two steps significantly enhance the hardness and compressive residual stress on the surface and interior of the specimens. Furthermore, because the submerged abrasive water jet strengthening process involves abrasive particle impact, high-pressure jet impact on the metal surface, and cavitation bubble collapse, the coupled effects of these three phases can induce plastic deformation on the metal surface, refine the grain size of the metal surface, and thus form a plastic deformation layer. The inventors first strengthened titanium alloy flat specimens by adjusting 17 different submerged abrasive water jet strengthening process parameters. The primary parameters controlled were jet pressure, abrasive flow rate, track spacing, traverse speed, and target distance. Surface integrity analysis was then performed to measure the surface hardness, roughness, surface residual stress, and depth of the plastic deformation layer of the 17 strengthened flat specimens and the unstrengthened flat specimens. Three optimized process solutions with the best overall performance were selected for subsequent erosion resistance testing, ultimately resulting in the present invention's optimal strengthening process solution for erosion resistance.

[0031] Chinese invention patent application CN202411282288.6 discloses a metal surface water jet-strengthened layer, its preparation method, and a composite erosion-resistant layer. This method combines a metal surface water jet-strengthened layer with a composite erosion-resistant coating to produce a composite erosion-resistant layer, resulting in excellent erosion resistance. However, this method has the following disadvantages: 1) The composite erosion-resistant layer contains a coating layer, and its preparation requires the addition of additional materials, such as ceramics or other alloys. During the coating preparation process, the weak adhesion between the coating and the metal substrate surface can lead to coating flaking; 2) the stability and economic cost are high, and the coating can prematurely fail due to external environmental factors, such as corrosive media, rendering it ineffective in protecting the metal substrate; 3) the coating material and process costs are also high; 4) there are environmental concerns, as waste gas and waste liquid are generated during the coating preparation process. High-temperature spray coatings can also cause deformation of the metal substrate.

[0032] However, according to the submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces provided by the present invention, on the one hand, the use of submerged abrasive water jet strengthening will not introduce other materials, and by directly generating plastic deformation inside the original material, the risk of coating peeling is avoided, while the cost brought by coating materials and processes is reduced; on the other hand, the submerged abrasive water jet strengthening process in the present invention is not only suitable for specimens with conventional flat structures, but is also particularly suitable for specimens with complex geometric structures. The strengthening area can be adjusted by a multi-axis robotic arm to process tiny structures that are difficult to cover with the coating, such as deep holes; on the other hand, the abrasive particles used in the present invention can be recycled and reused, which can effectively avoid environmental pollution problems.

[0033] The present invention has the following significant improvements over the prior art: 1) The present invention improves the erosion resistance of the sample by adjusting different strengthening process parameters, thereby obtaining a strengthening process scheme with good erosion resistance performance; 2) The present invention adopts different fixtures and strengthening procedures to achieve strengthening processing of metal matrices with different structures and dimensional parameters; 3) The present invention is simple to operate and easy to implement; 4) By generating plastic deformation directly inside the original material, the risk of coating peeling is avoided; 5) The abrasive particles used can be recycled and reused, which can effectively avoid environmental pollution problems.

[0034] In summary, the present invention discloses a submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces, belonging to the technical field of metal material surface strengthening. According to the method of the present invention, plastic deformation can be generated on the metal surface, the grains of the metal surface layer can be refined, and a plastic deformation layer can be formed. According to the method of the present invention, various structural specimens such as flat plates, cylinders, and blades can be strengthened. While significantly improving the erosion resistance of metal matrix components, the surface quality and fatigue resistance can be improved, and their service life can be extended. The method has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 This is a schematic diagram of the overall structure of the submerged abrasive water jet strengthening process device of the present invention; Figure 2 It is a schematic diagram of submerged abrasive water jet strengthening of a flat specimen; Figure 3 is a schematic diagram of submerged abrasive water jet strengthening of cylindrical specimens; Figure 4 This is a schematic diagram of submerged abrasive water jet strengthening of blade-like structure specimens; Figure 5A-5B These are the three-dimensional morphologies of the titanium alloy surface before and after submerged abrasive water jet strengthening process; Figure 6 This is a scanning electron micrograph of the titanium alloy surface after submerged abrasive water jet strengthening process; Figure 7 This is a comparison chart of the erosion rate of a pure erosion plate treated with a submerged abrasive water jet strengthening process and a pure erosion plate not treated with a submerged abrasive water jet strengthening at different erosion angles; Figure 8 This is a comparison chart of the erosion rates of pure eroded cylinders and blade-like structures treated with the optimal submerged abrasive water jet strengthening process and pure eroded cylinders and blade-like structures not treated with submerged abrasive water jet strengthening at the same angle (90°); The meanings of the reference numerals are as follows: 1. Automatic feeding system; 2. Stainless steel water tank; 3. Water outlet; 4. Filter; 5. Robotic arm; 6. Straight nozzle; 61. High-pressure water jet inlet; 62. Abrasive inlet; 63. Mixing chamber; 64. Tungsten steel sand pipe; 7. Marble base plate; 8. Booster pump; 9. Jet control system; 10. Robotic arm control system; 100. Flat specimen; 200. Cylindrical specimen; 300. Blade-type structure specimen. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific examples. It should be understood that the following examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. Unless otherwise specified, the techniques used in the examples are conventional in the art, or according to the experimental methods recommended by the instrument and equipment manufacturers. The reagents and materials used in the examples are commercially available unless otherwise specified.

[0038] According to the present invention, a submerged abrasive water jet strengthening process for metal surface erosion resistance is provided, wherein a plastic deformation layer is introduced on the surface of the workpiece after strengthening, thereby effectively improving its erosion resistance.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1The figure shows a submerged abrasive water jet strengthening device according to the present invention, comprising: an automatic feeding system 1, a water tank 2, a water outlet 3, a filter screen 4, a robotic arm 5, a straight nozzle 6, a marble base plate 7, a booster pump 8, a jet control system 9, and a robotic arm control system 10. After the sample to be strengthened is cleaned, it is fixed with a clamp or a bench vise and submerged in the water tank 2. The outlet end of the straight nozzle 6 is perpendicular to the surface of the sample to be strengthened. By moving the robotic arm 5, a certain target distance between the straight nozzle 6 and the sample can be maintained. The inlet end of the straight nozzle 6 includes an abrasive inlet 62 and a high-pressure water jet inlet 61, and the outlet end includes a mixing chamber 63 and a tungsten steel sand pipe 64 connected in sequence (see Figure 2 ), the abrasive inlet 62 is connected to the automatic feeding system 1 via a pipeline, and the high-pressure water jet inlet 61 is connected to the booster pump 8 via a pipeline. The booster pump 8 absorbs tap water, pressurizes it, and delivers it to the high-pressure water jet inlet 61 of the straight nozzle 6. The automatic feeding system 1 adds abrasive and delivers it to the abrasive inlet 62 of the straight nozzle 6. A filter 4 is also installed at the water outlet 3 at the bottom of the water tank 2 to reduce the outflow of abrasive particles.

[0041] The high-pressure water jet and the metal abrasive particles are mixed in the mixing chamber 63 of the straight nozzle 6 and then rushed out through the tungsten steel sand tube 64 to form a submerged abrasive water jet underwater. The stainless steel particles, high-pressure water jet, and cavitation bubbles act together on the surface of the sample to be strengthened, so that the grains on the sample surface are refined, thereby improving the erosion resistance.

[0042] Tablet Example 1: Step S1: heat treating the original titanium alloy material.

[0043] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0044] Step S2: processing the heat-treated titanium alloy plate.

[0045] According to the structural dimension parameters of the titanium alloy flat plate specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plate is processed, and the processed flat plate specimen 100 needs to be polished to a specified roughness of Ra=0.4±0.1μm.

[0046] Step S3: performing stress relief annealing treatment on the processed flat plate sample 100 .

[0047] The flat plate sample 100 to be strengthened is placed in a muffle furnace for stress relief annealing to reduce the residual stress inside the workpiece. The sample is heated in the furnace for 120 minutes to 560°C and held at that temperature for 120 minutes. The sample is then cooled in the furnace for 18 hours before being removed.

[0048] Step S4: Before strengthening, the sample is ultrasonically cleaned with anhydrous ethanol for 3 minutes.

[0049] like Figure 2 As shown, first, use a bench vise to secure both sides of a flat specimen 100 to ensure the specimen surface is level. Then, secure the straight nozzle to a robotic arm and use a controller to move the arm so that the nozzle is perpendicular to the specimen surface and maintains a specific target distance. The target distance used is 15 mm.

[0050] Step S5: Generate the trajectory file required for strengthening using Matlab, upload the trajectory file to the robotic arm controller, and achieve strengthening with different interval distances by editing the trajectory file. The interval distance used is 0.05 mm.

[0051] By adjusting the robot arm controller to change different traverse speeds, using the jet control system to change different abrasive flow rates, and adjusting the booster pump to change different jet pressures, the adopted traverse speed is 5mm / s, the abrasive flow rate is 20%, and the jet pressure is 100Mpa.

[0052] Press the start button on the fluidics control system, turn on the abrasive switch first, then the fluidics switch. Once the fluidics are stable, press the start button on the robotic arm controller to begin strengthening the specimen. After the robotic arm has completed all its trajectories, press the pause button to switch to manual operation mode. Use the robotic arm controller to move the robotic arm and remove the flat specimen from the bench vise. This completes the strengthening of the flat specimen.

[0053] Tablet Example 2: Step S1: heat treating the original titanium alloy material.

[0054] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0055] Step S2: processing the heat-treated titanium alloy plate.

[0056] According to the structural dimension parameters of the titanium alloy flat plate specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plate is processed, and the processed flat plate specimen 100 needs to be polished to a specified roughness of Ra=0.4±0.1μm.

[0057] Step S3: performing stress relief annealing treatment on the processed flat plate sample 100 .

[0058] The flat plate sample 100 to be strengthened is placed in a muffle furnace for stress relief annealing to reduce residual stress inside the workpiece. The flat plate sample 100 is heated in the furnace for 120 minutes to 560°C and then held at that temperature for 120 minutes. The sample is then removed from the furnace after cooling for 18 hours.

[0059] Step S4: Before strengthening, the flat sample 100 is ultrasonically cleaned with anhydrous ethanol for 3 minutes.

[0060] like Figure 2 As shown, first, use a bench vise to secure both sides of a flat specimen 100 to ensure the specimen surface is level. Then, secure the straight nozzle to a robotic arm and use a controller to move the arm so that the nozzle is perpendicular to the specimen surface and maintains a specific target distance. The target distance used is 15 mm.

[0061] Step S5: Generate the trajectory file required for strengthening using Matlab, upload the trajectory file to the robotic arm controller, and achieve strengthening with different interval distances by editing the trajectory file. The interval distance used is 0.1 mm.

[0062] By adjusting the robot arm controller to change different traverse speeds, using the jet control system to change different abrasive flow rates, and adjusting the booster pump to change different jet pressures, the adopted traverse speed is 5mm / s, the abrasive flow rate is 20%, and the jet pressure is 100Mpa.

[0063] Press the start button on the jet control system, turn on the abrasive switch first and then the jet switch. After stabilization, press the start button on the robotic arm controller to start strengthening the sample.

[0064] After the robotic arm has completed all the tracks, press the pause button to switch to manual operation mode. Use the robotic arm controller to move the robotic arm and remove the flat specimen from the bench vise to complete the strengthening of the flat specimen.

[0065] The difference between Example 2 and Example 1 is that different process parameters are used for strengthening, which requires rewriting the robot arm trajectory code and adjusting other process parameters.

[0066] Tablet Example 3: Step S1: heat treating the original titanium alloy material.

[0067] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0068] Step S2: processing the heat-treated titanium alloy plate.

[0069] According to the structural dimension parameters of titanium alloy flat plate specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plates are processed, and the processed specimens are polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0070] Step S3: performing stress relief annealing treatment on the processed flat plate sample 100 .

[0071] The titanium alloy workpiece to be strengthened is placed in a muffle furnace for stress relief annealing to reduce residual stress within the workpiece. The sample is heated in the furnace for 120 minutes to 560°C, held at that temperature for 120 minutes, and then cooled in the furnace for 18 hours before being removed.

[0072] Step S4: Before strengthening, the flat sample 100 is ultrasonically cleaned with anhydrous ethanol for 3 minutes.

[0073] like Figure 2 As shown, first, use a bench vise to secure both sides of a flat specimen 100 to ensure the specimen surface is level. Then, secure the straight nozzle to a robotic arm and use a controller to move the arm so that the nozzle is perpendicular to the specimen surface and maintains a specific target distance. The target distance used is 15 mm.

[0074] Step S5: Generate the trajectory file required for strengthening using Matlab, upload the trajectory file to the robotic arm controller, and achieve strengthening with different interval distances by editing the trajectory file. The interval distance used is 0.1 mm.

[0075] By adjusting the robot arm controller to change different traverse speeds, using the jet control system to change different abrasive flow rates, and adjusting the booster pump to change different jet pressures, the adopted traverse speed is 5mm / s, the abrasive flow rate is 25%, and the jet pressure is 160Mpa.

[0076] Press the start button on the jet control system, turn on the abrasive switch first and then the jet switch. After stabilization, press the start button on the robotic arm controller to start strengthening the sample.

[0077] After the robotic arm has completed all the tracks, press the pause button to switch to the manual operation mode, use the robotic arm controller to move the robotic arm, and remove the flat sample 100 from the bench vise, thus completing the strengthening of the flat sample.

[0078] This embodiment differs from embodiments 1 and 2 in that the process parameters are different. Cylindrical and blade-like structure embodiments and comparative examples are added later. On the one hand, the structures of these two specimens are different from those of flat specimens. On the other hand, the technical difficulty lies in that in order to achieve the same strengthening process as that of flat specimens, the program of the robot arm's operation trajectory needs to be rewritten for these two specimens. In addition, a four-jaw chuck and a separate fixture are introduced and designed.

[0079] Flat plate comparative example 1: Step S1: heat treating the original titanium alloy material.

[0080] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0081] Step S2: processing the heat-treated titanium alloy plate.

[0082] According to the structural dimension parameters of titanium alloy flat plate specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plates are processed, and the processed specimens are polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0083] Step S3: performing stress relief annealing treatment on the processed flat plate sample.

[0084] The flat sample was placed in a muffle furnace for stress relief annealing to reduce the residual stress inside the workpiece. The sample was heated in the furnace for 120 minutes to 560°C, kept at this temperature for 120 minutes, and then cooled in the furnace for 18 hours before being removed from the furnace.

[0085] The samples were ultrasonically cleaned with anhydrous ethanol for 3 min.

[0086] The comparative flat sample did not need to be strengthened. After cleaning and drying, the erosion test was carried out under the same conditions to compare the anti-erosion effects before and after strengthening.

[0087] Cylindrical Example 1: Step S1: heat treating the original titanium alloy material.

[0088] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0089] Step S2: processing the heat-treated titanium alloy rod.

[0090] According to the structural dimension parameters of the titanium alloy cylindrical specimens subjected to erosion and static load erosion, the heat-treated titanium alloy rod is processed. The processed cylindrical specimen 200 needs to be polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0091] Step S3: performing stress relief annealing treatment on the processed cylindrical specimen 200 .

[0092] The cylindrical specimen 200 to be strengthened is placed in a muffle furnace for stress relief annealing to reduce residual stress within the workpiece. The specimen is heated in the furnace for 120 minutes to 560°C, held at that temperature for 120 minutes, and then cooled in the furnace for 18 hours before being removed.

[0093] Step S4: Before strengthening, the sample is ultrasonically cleaned with anhydrous ethanol for 3 minutes.

[0094] like Figure 4 As shown, first, the cylindrical sample 200 is loaded into the fixture, and the fixture is fixed with a four-jaw chuck. Then, the straight nozzle 6 is fixed on the robot arm 5, and the robot arm 5 is moved by the controller so that the straight nozzle 6 is perpendicular to the sample surface and maintains a certain target distance. The target distance used is 15 mm.

[0095] Step S5: Use MATLAB to generate the trajectory required for strengthening, upload the trajectory file to the robotic arm controller, and edit the trajectory file to achieve strengthening with different interval distances. The interval distance used is 0.05 mm.

[0096] By adjusting the robot arm controller to change different traverse speeds, using the jet control system to change different abrasive flow rates, and adjusting the booster pump to change different jet pressures, the adopted traverse speed is 5mm / s, the abrasive flow rate is 20%, and the jet pressure is 100Mpa.

[0097] Press the start button on the jet control system, turn on the abrasive switch first and then the jet switch. After stabilization, press the start button on the robotic arm controller to start strengthening the sample.

[0098] After the robotic arm has completed all the tracks, press the pause button to switch to manual operation mode. Use the robotic arm controller to move the robotic arm, remove the cylindrical erosion and static load erosion fixtures from the four-jaw chuck, and finally remove the cylindrical specimen 200 from the fixture, that is, strengthen the surface of the cylindrical specimen.

[0099] Cylindrical comparison example 1: Step S1: heat treating the original titanium alloy material.

[0100] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0101] Step S2: processing the heat-treated titanium alloy rod.

[0102] According to the structural dimensional parameters of the titanium alloy cylindrical specimens subjected to erosion and static load erosion, the heat-treated titanium alloy bars are processed, and the processed specimens are polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0103] Step S3: performing stress relief annealing treatment on the processed cylindrical specimen.

[0104] The cylindrical specimen to be strengthened is placed in a muffle furnace for stress relief annealing to reduce the residual stress inside the workpiece. The specimen is heated in the furnace for 120 minutes to 560°C, held at that temperature for 120 minutes, and then cooled in the furnace for 18 hours before being removed.

[0105] The samples were ultrasonically cleaned with anhydrous ethanol for 3 min.

[0106] The cylindrical sample control group does not need to be strengthened. After cleaning and drying, the erosion test is carried out under the same conditions to compare the anti-erosion effect before and after strengthening.

[0107] Blade structure embodiment 1: Step S1: heat treating the original titanium alloy material.

[0108] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0109] Step S2: processing the heat-treated titanium alloy block.

[0110] According to the structural dimension parameters of blade-type structural specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plates are processed. The processed specimens need to be polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0111] Step S3: performing stress relief annealing treatment on the processed blade structure sample.

[0112] The blade-like structure specimen to be strengthened was placed in a muffle furnace for stress relief annealing to reduce residual stress within the workpiece. The specimen was heated in the furnace for 120 minutes to 560°C, held at that temperature for 120 minutes, and then cooled in the furnace for 18 hours before being removed.

[0113] Step S4: Before strengthening, the sample is ultrasonically cleaned with anhydrous ethanol for 3 minutes.

[0114] like Figure 3 As shown, a bench vise is used to secure the blade specimen 300 to both sides of the fixture, ensuring the specimen's blade edge is level. A straight nozzle 6 is then secured to a robotic arm 5. The controller moves the robotic arm so that the nozzle is perpendicular to the specimen's blade edge and maintains a target distance of 15 mm.

[0115] Step S5: Use MATLAB to generate the trajectory required for strengthening, upload the trajectory file to the robotic arm controller, and edit the trajectory file to achieve strengthening with different interval distances. The interval distance used is 0.05 mm.

[0116] By adjusting the robot arm controller to change different traverse speeds, using the jet control system to change different abrasive flow rates, and adjusting the booster pump to change different jet pressures, the adopted traverse speed is 5mm / s, the abrasive flow rate is 20%, and the jet pressure is 100Mpa.

[0117] Press the start button on the jet control system, turn on the abrasive switch first and then the jet switch. After stabilization, press the start button on the robotic arm controller to start strengthening the sample.

[0118] After the robotic arm has completed all trajectories, press the pause button to switch to manual operation mode. Use the robotic arm controller to move the robotic arm and remove the blade structure erosion and static load erosion fixtures from the bench vise. This completes the strengthening of a certain blade edge surface of the blade structure specimen. The strengthening of the remaining blade edge surfaces can be achieved by reversing the fixture direction and repeating the above steps.

[0119] Comparative Example 1 of Blade Structure: Step S1: heat treating the original titanium alloy material.

[0120] The original titanium alloy was placed in a muffle furnace for heat treatment at 960°C for 250 minutes and then air-cooled. After heat treatment, the titanium alloy transformed from an acicular structure to an equiaxed duplex structure consisting of equiaxed α and reticular β.

[0121] Step S2: processing the heat-treated titanium alloy block.

[0122] According to the structural dimension parameters of blade-type structural specimens subjected to erosion and static load erosion, the heat-treated titanium alloy plates are processed. The processed specimens need to be polished to a specified roughness of Ra = 0.4 ± 0.1 μm.

[0123] Step S3: performing stress relief annealing treatment on the processed blade structure sample.

[0124] The blade-like structure specimens were placed in a muffle furnace for stress relief annealing to reduce residual stress within the workpiece. The specimens were heated to 560°C for 120 minutes, held at that temperature for 120 minutes, and then cooled for 18 hours before being removed from the furnace.

[0125] The samples were ultrasonically cleaned with anhydrous ethanol for 3 min.

[0126] The comparative samples of blade structures do not need to be strengthened. After cleaning and drying, erosion tests are carried out under the same conditions to compare the anti-erosion effects before and after strengthening.

[0127] Figure 5A-5B The three-dimensional surface morphology of the titanium alloy flat plate specimen of the present invention before and after strengthening by submerged abrasive water jet (flat plate Example 1) is shown. As can be seen from the figure, before strengthening, there are processing marks on the surface of the specimen, showing linear grooves. After strengthening, due to the combined effects of abrasive particle impact, cavitation bubble collapse, and high-pressure jet impact, the previous surface processing marks are eliminated, and the surface roughness is slightly improved.

[0128] Figure 6 The scanning electron micrograph of the titanium alloy surface after the titanium alloy is strengthened by submerged abrasive water jet in the present invention (flat plate Example 1) is shown. As can be seen from the figure, due to the high-speed impact of the abrasive particles, broken abrasive particles will remain on the surface of the titanium alloy.

[0129] Figure 7 The graph shows how the erosion rate changes with the erosion angle after adopting three different abrasive water jet strengthening process schemes (flat plate embodiment 1, flat plate embodiment 2, flat plate embodiment 3) of the present invention. It can be seen from the figure that after strengthening with the three different process schemes, the erosion rate at each angle is lower than that of the unstrengthened titanium alloy.

[0130] Figure 8 The graph shows the erosion rates of the cylindrical specimens and blade-like structure specimens of the present invention at the same erosion angles (15°, 40°, 65°, 90°) after being strengthened using the optimal process solutions (cylindrical embodiment 1, blade-like structure embodiment 1). It can be seen from the graph that the erosion resistance of the blade-like structure specimens is improved by nearly 50%.

[0131] According to the present invention, a submerged water jet strengthening process for improving the erosion resistance of metal surfaces includes the following steps: preliminary heat treatment of the metal substrate; design and processing of flat plate, cylindrical, and blade-like structural specimens for erosion and static load erosion; stress relief annealing to eliminate residual stress during specimen processing; design of a specific fixture and four-jaw chuck based on the specimen structure and dimensional parameters; mounting the specimen in conjunction with a bench vise; and control of the workpiece strengthening parameters, with the main controllable process parameters being jet pressure, target distance, track spacing, abrasive flow rate, and abrasive flow rate. The surface roughness of the specimen after strengthening according to this strengthening process is slightly improved, and a 20-35μm plastic deformation layer is formed on the metal substrate surface. Due to the combined action of abrasive particles, cavitation bubbles, and the submerged high-pressure jet, compressive residual stress of 600Mpa or more is generated on the surface. Therefore, this process can significantly improve the erosion resistance of the surface of a metal substrate (such as a titanium alloy substrate) and extend its service life.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. Any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention is conventional technology.

Claims

1. A submerged water jet surface strengthening process for improving the erosion resistance of metal surfaces, characterized in that: The following steps are involved: 1) Heat treatment of the metal matrix at a temperature of 960±40°C, holding time of 250±30 min, followed by air cooling. The treated sample is composed of α phase and β phase; 2) The heat-treated metal substrate is processed into a sample to be strengthened according to the structural and dimensional requirements and polished to remove surface burrs. After polishing, the surface roughness of the sample is Ra = 0.4 ± 0.1 μm; 3) Perform stress relief annealing on the specimen to be strengthened. Heat the furnace to 560°C for 120±30min, keep the temperature for 120±30min, and then cool the furnace for 18±2h. 4) Use anhydrous ethanol to ultrasonically clean the sample to be strengthened. After cleaning, fix the sample to be strengthened with a clamp or bench vise. Move the robotic arm to ensure a certain target distance between the nozzle and the sample to be strengthened. Open the water valve and let tap water at 25-28℃ flow into the water pool to ensure that the sample to be strengthened is completely submerged in water. 5) Use a booster pump to pressurize the atmospheric water. By changing the operating power of the booster pump, the jet pressure is regulated. The abrasive flow entering the nozzle is controlled by an electronic sand control valve. The traverse speed of the robotic arm and the interval between adjacent tracks are controlled by a program. The metal abrasive particles are mixed with the high-pressure water jet and then act on the metal surface to achieve surface strengthening of the sample to be strengthened, introducing a plastic deformation layer on the workpiece surface. 6) After removing the robotic arm, remove the specimen from the fixture or vise.

2. The submerged water jet surface strengthening process according to claim 1, characterized in that: In step 4), the robotic arm is moved so that the target distance is maintained between 5 and 20 mm.

3. The submerged water jet surface strengthening process according to claim 1, characterized in that: In the step 5), the metal abrasive particles used are 340 stainless steel spherical particles with an average particle size of 135±35 μm.

4. The submerged water jet surface strengthening process according to claim 1, characterized in that: In step 5), the jet pressure is 100-160 MPa, the abrasive flow rate is 5-25%, the traverse speed is 2-11 mm / s, and the track interval is 0.05-0.2 mm.

5. The submerged water jet surface strengthening process according to claim 1, characterized in that: The samples to be strengthened include: flat plate structures, cylindrical structures and blade-like structures.

6. The submerged water jet surface strengthening process according to claim 5, characterized in that: In step 4), for the flat structure specimen, a bench vise is used to clamp it. After strengthening one side, the specimen is removed and turned over, and the other side is facing upward and fixed, thereby achieving double-sided strengthening. For the cylindrical structure specimen, a fixture is used to clamp it. After clamping, the fixture is fixed with a four-jaw chuck. The rotation of the four-jaw chuck is combined with the movement of the robotic arm to achieve the strengthening of the outer surface of the entire cylindrical structure specimen. For the blade structure specimen, a fixture is used to clamp it so that a certain blade edge surface faces upward. After clamping, the fixture is fixed with a bench vise. After completing the strengthening of the blade edge surface, the strengthening of the remaining blade edge surfaces is achieved by reversing the direction of the fixture.

7. The submerged water jet surface strengthening process according to claim 1, characterized in that: The metal matrix is titanium alloy.

8. The submerged water jet surface strengthening process according to claim 1, characterized in that: The submerged water jet surface strengthening process is carried out using a submerged abrasive water jet strengthening device, which includes: an automatic feeding system, a stainless steel water tank, a water outlet, a filter, a robotic arm, a nozzle, a marble bottom plate, a booster pump, a jet control system, and a robotic arm control system. The sample to be strengthened is clamped by a bench vise or a clamp, which is clamped in the gap of the marble floor, and the clamp is clamped by a four-jaw chuck. After the sample is clamped, the valve of the water inlet pipe is opened to allow water to be introduced into the stainless steel water tank until the sample is submerged. Dried metal abrasive particles can be added to the automatic feeding system, which is connected to the abrasive inlet of the nozzle via a pipeline, and an air compressor provides conveying power for it. The booster pump is connected to the high-pressure water inlet of the nozzle via a pipeline. The high-pressure water jet and the metal abrasive particles are mixed inside the nozzle, sprayed out through a tungsten steel sand pipe, and act on the sample surface underwater.

9. The submerged water jet surface strengthening process according to claim 8, characterized in that: The side of the stainless steel water tank is provided with a water outlet and connected to the water outlet pipeline. A filter is provided on the water outlet side. After the strengthening is completed, the water outlet valve is opened and the abrasive particles automatically sink to the bottom. The abrasive particles that sink to the bottom can be recycled and dried for reuse.

10. A metal surface erosion-resistant water jet strengthening layer prepared by the submerged water jet surface strengthening process according to any one of claims 1 to 9, characterized in that: The plastic deformation layer on the surface of the metal substrate reaches 20-35μm, and the erosion resistance is greatly improved.

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