Method for improving performance of Ni-based high-temperature alloy surface coating

Abstract

The invention discloses a method for improving the performance of a Ni-based high-temperature alloy surface coating, and relates to the technical field of coating preparation, in particular to the method for improving the performance of the Ni-based high-temperature alloy surface coating. The invention aims to solve the technical problems of low bonding strength and non-compactness of the cold-sprayed coating on the surface of the Ni-based high-temperature alloy at present. According to the method, the super-hydrophilic surface appearance of the Ni-based high-temperature alloy is designed through the laser microstructuring technology, textured patterns are promoted to be formed on the surface, the spreading and stacking infiltration capacity of spraying powder is controlled, a five-element high-entropy alloy coating is prepared on the Ni-based high-temperature alloy laser textured surface through cold spraying, and then a mechanical locking structure is formed. The prepared coating has the wear resistance, corrosion resistance and high temperature resistance of a high-entropy alloy, the bonding strength is high, the structure is compact, the preparation method of the coating is simple, and industrial production is easy.

Description

Technical Field

[0001] The invention relates to the technical field of coating preparation, and in particular to a method for improving the performance of a coating on the surface of a Ni-based high-temperature alloy. Background Art

[0002] Ni-based high-temperature alloy surface coatings are used in key components of aircraft engines, turbine blades of gas turbines and other applications. It is often necessary to maintain the integrity of the coating under extremely high temperatures, which poses a great challenge to the bonding strength of the coating, especially how to ensure that the coating of these components does not delaminate or fall off under long-term high-temperature working conditions, which is related to the safe operation and service life of the equipment. Under the long-term high-temperature cyclic service conditions in the actual application field, bonding strength is also an important indicator for evaluating material aging and performance degradation, and is crucial to the long-term reliability of the material. The cold spraying process of forming the coating produces almost no thermal effect, and it is difficult to form a metallurgical bond with the substrate. In addition, due to the difficulty of plastic deformation of the Ni-based material itself, the bonding strength and porosity of the cold-sprayed Ni-based high-temperature alloy coating are extremely prominent. Summary of the invention

[0003] The present invention aims to solve the current technical problems of low bonding strength and high porosity of cold sprayed coatings on the surface of Ni-based high-temperature alloys, and to provide a method for improving the performance of Ni-based high-temperature alloy surface coatings.

[0004] The method for improving the performance of the Ni-based high-temperature alloy surface coating of the present invention is carried out according to the following steps:

[0005] S1. Surface treatment is performed on the surface of the Ni-based high-temperature alloy plate to be sprayed;

[0006] S2, placing the Ni-based high-temperature alloy plate that has been surface treated in S1 on a laser processing platform, and forming a textured pattern on the surface to be sprayed by laser microstructuring;

[0007] S3. The Ni-based high-temperature alloy plate treated with laser microstructuring in S2 is transferred to a cold spraying workbench, the vacuum-dried spray powder is loaded into a powder feeder of a cold spraying device, and a cold spraying gun is connected to a working gas. The spray powder is accelerated by the working gas in the spray gun to form a supersonic particle flow, which is ejected from the nozzle and collides with and deposits on the surface of the Ni-based high-temperature alloy to be sprayed after laser microstructuring to form a spray coating; the spray powder is a five-element high-entropy alloy powder.

[0008] Design principle of the invention:

[0009] 1. In S2, the laser beam precisely creates microscopic geometric structures or patterns on the surface of the Ni-based superalloy. These structures can be ordered textures, pits, grooves, grids or other complex patterns. Different laser surface patterns form highly controllable hydrophilic and hydrophobic features without changing the material phase structure, thereby enhancing the mechanical interlocking behavior between the substrate and the sprayed powder (in S3), thereby changing the droplet spreading state on the substrate surface, reducing the droplet wetting angle, and making it easier for the sprayed particles to infiltrate the substrate surface.

[0010] Second, after laser microstructured surface treatment, the spreading process of cold spray droplets is greatly improved, and subsequent laminated particles are more easily stacked on the textured surface, thereby significantly reducing the internal porosity of the coating and improving the density of the coating;

[0011] 3. The spraying powder in S3 is a five-element high-entropy coating. Due to the diversity of its material system, it is highly sensitive to processing temperature and is prone to form a variety of impurity phases, thus losing some key performance. Cold spraying is mainly based on low working temperature and fast particle flight speed. The sprayed powder particles are mostly dominated by plastic deformation process, thus forming a solid-state deposited surface coating, which has good adaptability to high-entropy alloy powder.

[0012] The present invention utilizes a combination of laser microstructuring technology and cold spraying technology. The Ni-based high-temperature alloy is subjected to laser microstructuring treatment to form an ordered textured pattern on the surface, and then five-element high-entropy powder spraying is performed. This allows the surface of the Ni-based high-temperature alloy to have the advantages of wear resistance, corrosion resistance and high temperature resistance of the high-entropy alloy, while significantly improving the bonding strength and density of the coating.

[0013] The beneficial effects of the present invention are:

[0014] 1. The micro laser texturing technology used in the present invention can be used to process laser patterns on flat plates and special-shaped structural parts, and has a wide range of applications;

[0015] 2. The present invention first treats the Ni-based high-temperature alloy to form a textured pattern surface on its surface, which can improve the bonding strength between the cold-sprayed spray particles and the substrate and reduce the porosity;

[0016] 3. The laser microstructuring surface patterns used in the present invention are diverse, the patterning of the sprayed particle surface can be controlled, and both hydrophilic and hydrophobic structures can be quickly processed;

[0017] 4. The laser technology used in the present invention can achieve zero-pollution processing, no waste gas release, and has a disinfection function, which not only protects the environment but also ensures health and safety;

[0018] 5. The method of the present invention is simple and effective to operate, and the obtained sprayed film has excellent performance, high bonding strength and low porosity, and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the process flow chart of Experiment 1;

[0020] Figure 2 This is a diagram of the device used in S2 and S3 in Experiment 1;

[0021] Figure 3 Schematic diagram of the laser scanning method in S2 of Experiment 1;

[0022] Figure 4 This is a SEM scanning image of a laser texturing pattern formed on the surface to be sprayed by laser microstructuring in S2 of Experiment 1;

[0023] Figure 5 The bonding strength curves of the Ni-based superalloy with surface groove pattern treated by laser microstructure in test 1 and the Ni-based superalloy without laser microstructure treatment in the comparative test;

[0024] Figure 6 This is a porosity result diagram of the pore statistics of a Ni-based high-temperature alloy with a surface groove pattern that was treated with laser microstructure in an experiment using a cross-sectional SEM capture method and a Ni-based high-temperature alloy that was not treated with laser microstructure in a comparative experiment. DETAILED DESCRIPTION

[0025] Specific implementation method 1: This implementation method is a method for improving the performance of Ni-based high-temperature alloy surface coating, which is specifically carried out in the following steps:

[0026] S1. Surface treatment is performed on the surface of the Ni-based high-temperature alloy plate to be sprayed;

[0027] S2, placing the Ni-based high-temperature alloy plate that has been surface treated in S1 on a laser processing platform, and forming a laser texturing pattern on the surface to be sprayed by laser microstructuring;

[0028] S3. The Ni-based high-temperature alloy plate treated with laser microstructuring in S2 is transferred to a cold spraying workbench, the vacuum-dried spray powder is loaded into a powder feeder of a cold spraying device, and a cold spraying gun is connected to a working gas. The spray powder is accelerated by the working gas in the spray gun to form a supersonic particle flow, which is ejected from the nozzle and collides with and deposits on the surface of the Ni-based high-temperature alloy to be sprayed after laser microstructuring to form a spray coating; the spray powder is a five-element high-entropy alloy powder.

[0029] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the thickness of the Ni-based high-temperature alloy plate described in S1 is 3 mm to 60 mm. The rest is the same as the specific implementation method 1.

[0030] Specific implementation method 3: This implementation method is different from specific implementation methods 1 or 2 in that the surface treatment steps in S1 are as follows:

[0031] 1. Use sandpaper to repeatedly polish the surface, sides and edges of the Ni-based high-temperature alloy plate to be sprayed to make the alloy surface bright and clean, and achieve the effect of removing burrs, oxide scale and rust;

[0032] 2. Use anhydrous ethanol to ultrasonically clean the Ni-based high-temperature alloy plate to remove surface stains;

[0033] 3. The cleaned substrate is placed in a drying oven for drying at a temperature of 70° C. to 80° C. for a drying time of 2 min to 5 min. The rest is the same as in the first or second embodiment.

[0034] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the laser texturing pattern described in S2 includes circular, triangular, grooved, star-shaped, regular hexagonal, square convex, interlaced grid grooves and spherical dimple shapes. Others are the same as specific embodiments 1 to 3.

[0035] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the laser power in S2 is 40W-150W, the scanning speed is 6mm / s-8mm / s, and the scanning interval is 200μm-1600μm. The rest is the same as specific embodiment 4.

[0036] Specific embodiment 6: This embodiment is different from specific embodiment 5 in that: the moving speed of the cold spray gun in S3 is 30mm / s-80mm / s, the powder feeding flow rate is adjusted to 30g / min-60g / min, the distance between the spray gun nozzle and the surface of the sprayed substrate is 15mm-30mm; the working gas is nitrogen, the pressure is 3MPa-3.5MPa, the gas preheating temperature is 450°-580°, and the preheating time is 5min. Others are the same as specific embodiment 5.

[0037] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that the five-element high entropy alloy powder described in S3 is CoCrFeNiAl alloy or CoCrFeNiTi alloy. The rest is the same as specific embodiment 6.

[0038] The present invention is verified by the following tests:

[0039] Test 1: This test is a method to improve the performance of Ni-based high-temperature alloy surface coating, such as Figure 1 As shown, the specific steps are as follows:

[0040] S1. Surface treatment is performed on the surface of the Ni-based high-temperature alloy plate to be sprayed;

[0041] The thickness of the Ni-based superalloy sheet is 10 mm, and the grade is GH4099;

[0042] The steps of surface treatment are as follows:

[0043] I. Repeatedly polish the surface to be sprayed, the side and the edges and corners of the Ni-based superalloy sheet with sandpaper to make the alloy surface bright and clean, achieving the effect of removing burrs, oxide scales and rust;

[0044] II. Ultrasonically clean the Ni-based superalloy sheet with anhydrous ethanol to remove the stains on the surface;

[0045] III. Place the cleaned substrate in a drying oven for drying, the drying temperature is 75 °C, and the drying time is 5 min;

[0046] S2. Place the Ni-based superalloy sheet with surface treatment in S1 on the laser processing platform, and form a laser texturing pattern on the surface to be sprayed through laser microstructural treatment. Specifically, it is a groove type, the laser power is 50 W, and the scanning mode is the "丨丨丨" type (as Figure 3 shown), the scanning mode is from top to bottom, from left to right. When the first vertical column pattern is scanned, the second vertical column is scanned, and so on; the scanning speed is 8 mm / s, and the scanning spacing is 450 μm;

[0047] S3. Transfer the Ni-based superalloy sheet with laser microstructural treatment in S2 to the cold spraying workbench, load the vacuum-dried spraying powder into the powder feeder of the cold spraying device, connect the cold spraying gun to the working gas, and the spraying powder is accelerated by the working gas in the gun to form a supersonic particle stream, which impacts and deposits on the surface to be sprayed of the Ni-based superalloy with laser microstructural treatment to form a spraying coating; the spraying powder is a five-element high-entropy alloy powder;

[0048] The moving speed of the cold spraying gun is 35 mm / s, adjust the powder feeding flow rate to 60 g / min, and the distance between the gun nozzle and the surface of the sprayed substrate is 21 mm; the working gas is nitrogen, the pressure is 3.2 MPa, the gas preheating temperature is 510 °, and the preheating time is 5 min;

[0049] The five-element high-entropy alloy powder described in S3 is CoCrFeNiTi alloy, and the five elements are in equimolar ratio.

[0050] Figure 2 Fig. is the device diagram used in S2 and S3 in Experiment 1 (the left figure corresponds to S2, and the right figure corresponds to S3), where 1 is the Ni-based superalloy sheet, 2 is the laser, 3 is the N2 gas cylinder, 4 is the powder feeder, 5 is the gas heating device, 6 is the mixing bin, and 7 is the discharge port.

[0051] Figure 4 This is a SEM scanning image of the laser texturing pattern formed on the surface to be sprayed by laser microstructuring treatment in S2 of experiment 1. It can be seen that the surface of the Ni-based high-temperature alloy is grooved after laser microstructuring treatment.

[0052] Comparative test: This test is different from the first test in that the alloy substrate is not laser microstructured, that is, there is no S2. The rest is the same as the first test.

[0053] The bonding strength test of the above samples was carried out by static tensile method. The sprayed samples were fixed on the test device, and then tensile force was gradually applied until the coating separated from the substrate or internal damage occurred. The ratio of the force at separation to the force-bearing area was the bonding strength.

[0054] Figure 5 Figure 3 is the bonding strength curve of the Ni-based superalloy with surface groove pattern treated with laser microstructure in test 1 and the Ni-based superalloy without laser microstructure treatment in the comparison test (both are samples after cold spraying). The solid line corresponds to the comparison test, and the dotted line corresponds to test 1. It can be clearly seen that the Ni-based superalloy without laser microstructure treatment in the comparison test has the highest bonding strength at 50.9s, with a bonding force of 24.2092MPa, while the Ni-based superalloy with surface groove pattern treated with laser microstructure in test 1 has the highest bonding strength at 276.0561s, with a bonding force of 55.7462MPa. It can be concluded that the Ni-based superalloy with surface groove pattern treated with laser microstructure has the advantage of higher bonding strength than the Ni-based superalloy without laser microstructure treatment.

[0055] Figure 6 This is a porosity result diagram of the Ni-based high-temperature alloy with a surface groove pattern that has been treated with laser microstructure in an experiment captured using a cross-sectional SEM, and the porosity statistics of the Ni-based high-temperature alloy that has not been treated with laser microstructure in a comparative experiment. It can be seen from the figure that the porosity of the coating obtained using the above process parameters has dropped from 1.56% to 1.31%, and the porosity has been significantly reduced.

[0056] The present invention adopts the above-mentioned preparation process method for improving the performance of Ni-based high-temperature alloy surface coating, combines the advantages of laser microstructuring technology and cold spraying, and can effectively obtain an excellent coating with high bonding strength and low porosity.

Claims

1. A method for improving the performance of Ni-based high-temperature alloy surface coating, characterized in that The method for improving the performance of Ni-based high-temperature alloy surface coating is carried out according to the following steps: S1. Surface treatment is performed on the surface of the Ni-based high-temperature alloy plate to be sprayed; S2, placing the Ni-based high-temperature alloy plate that has been surface treated in S1 on a laser processing platform, and forming a laser texturing pattern on the surface to be sprayed by laser microstructuring; S3. The Ni-based high-temperature alloy plate treated with laser microstructuring in S2 is transferred to a cold spraying workbench, the vacuum-dried spray powder is loaded into a powder feeder of a cold spraying device, and a cold spraying gun is connected to a working gas. The spray powder is accelerated by the working gas in the spray gun to form a supersonic particle flow, which is ejected from the nozzle and collides with and deposits on the surface of the Ni-based high-temperature alloy to be sprayed after laser microstructuring to form a spray coating; the spray powder is a five-element high-entropy alloy powder.

2. A method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that The thickness of the Ni-based high-temperature alloy plate described in S1 is 3 mm to 60 mm.

3. A method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that The steps of surface treatment in S1 are as follows:

1. Use sandpaper to repeatedly polish the surface, sides and corners of the Ni-based high-temperature alloy plate to be sprayed to make the alloy surface bright and clean, and achieve the effect of removing burrs, oxide scale and rust; 2. Use anhydrous ethanol to ultrasonically clean the Ni-based high-temperature alloy plate to remove surface stains; 3. Place the cleaned substrate in a drying oven for drying at a temperature of 70°C to 80°C for 2 minutes to 5 minutes.

4. A method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that the laser texturing pattern described in S2 includes a circle, a triangle, a groove, a star, a regular hexagon, a square convex shape, an interlaced grid groove and a spherical dimple shape.

5. A method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that The laser power in S2 is 40W to 150W, the scanning speed is 6mm / s to 8mm / s, and the scanning spacing is 200μm to 1600μm.

6. A method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that In S3, the moving speed of the cold spray gun is 30mm / s~80mm / s, the powder feeding flow rate is adjusted to 30g / min~60g / min, and the distance between the spray gun nozzle and the surface of the sprayed substrate is 15mm~30mm; the working gas is nitrogen, the pressure is 3MPa~3.5MPa, the gas preheating temperature is 450°~580°, and the preheating time is 5min.

7. The method for improving the performance of Ni-based high-temperature alloy surface coating according to claim 1, characterized in that The five-element high entropy alloy powder described in S3 is CoCrFeNiAl alloy or CoCrFeNiTi alloy.

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