A method for improving the high-temperature oxidation resistance of (γ’+γ) NiAlX protective coatings

Abstract

The present invention belongs to the technical field of metal protective coatings, and relates to a method for improving the high-temperature oxidation resistance of a (γ’ + γ)NiAlX protective coating. First, a coating is prepared on a nickel-based superalloy substrate by means of electron beam physical vapor deposition; then, the coating is subjected to shock strengthening using a nanosecond laser; finally, the shocked coating is subjected to vacuum heat treatment. The high-pressure shock wave induced by the laser realizes the proliferation of dislocation density, grain refinement and fine and dispersed distribution of active elements on the coating surface layer. At the same time, the vacuum heat treatment can eliminate the residual stress inside the coating. The (γ’ + γ)NiAlX protective coating prepared by the present invention rapidly forms a dense alumina film on the surface after oxidation, the oxidation rate is significantly reduced, the thickness of the oxide film is more uniform, and the thickness of the interdiffusion zone below the coating / substrate interface is significantly reduced, significantly improving the oxidation resistance of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal protective coatings and surface modification, and relates to a method for improving the high-temperature oxidation resistance of a (γ'+γ)NiAlX protective coating. Background Art

[0002] Thermal barrier coatings are one of the key technologies for improving the temperature-bearing capacity of turbine blades in advanced aero-engines. As a crucial part of the thermal barrier coating system, the metallic bond coat directly determines the service life of the entire coating system. Currently, the applied metallic bond coats MCrAlY (M: Ni, Co, etc.) and β-NiPtAl, although having excellent oxidation resistance, exhibit interfacial element interdiffusion with the single-crystal alloy of the blade at high temperatures, seriously affecting the mechanical properties of the alloy matrix and making it difficult to meet the application requirements of advanced aero-engines. Therefore, it is urgent to develop new metallic bond coat materials that are compatible and matched with the single-crystal alloy interface.

[0003] (γ'+γ) duplex Ni-Al alloy is a very promising candidate material for a new metallic bond coat. However, on the one hand, traditional (γ'+γ) coatings are prepared by electroplating platinum and vacuum heat treatment, and their oxidation resistance is greatly affected by the alloy composition, making them unable to be used as a general bond coat material. On the other hand, the low Al content in the (γ'+γ)NiAl system will inevitably affect its high-temperature oxidation resistance. Therefore, it is necessary to study the (γ'+γ) duplex Ni-Al system from aspects such as preparation methods and post-treatment processes. Summary of the Invention

[0004] The object of the present invention is: aiming at the problem that the service life of the existing (γ'+γ)NiAlX protective coating is significantly reduced at 1100°C, the present invention provides a method for improving the high-temperature oxidation resistance of the (γ'+γ)NiAlX protective coating.

[0005] To solve this technical problem, the technical solution of the present invention is:

[0006] Provide a method for improving the high-temperature oxidation resistance of a (γ'+γ)NiAlX protective coating, the method comprising the following steps:

[0007] First step, pretreatment of the superalloy matrix sample:

[0008] Grind the matrix sample with SiC sandpaper, then perform sandblasting treatment, ultrasonically clean the sandblasted sample, and dry it.

[0009] Second step, prepare a (γ'+γ)NiAlX protective coating by electron beam physical vapor deposition method:

[0010] The atomic content percentage of the (γ’+γ)NiAlX protective coating composition is as follows: 10-30% Al, 0.05-2% X, and the rest is Ni, where X is one or more of Hf, Zr, and Y;

[0011] 2.1. Prepare evaporation targets:

[0012] Weigh high-purity raw materials according to the composition measurement, clean and dry them, and then perform vacuum induction melting under the conditions of a vacuum degree of 1×10 -3 Pa to 5×10 -2 Pa and a current of 650-950A to prepare (γ’+γ)NiAlX ingots;

[0013] Subsequently, perform homogenization annealing on the ingots at a temperature of 1200±50°C for 20-24h and a vacuum degree of 1×10 -3 Pa to 5×10 -2 Pa;

[0014] Cut the annealed ingots into targets of the required size;

[0015] 2.2. Deposit the (γ’+γ)NiAlX coating:

[0016] Install the superalloy substrate pretreated in the first step on the rotating fixture in the electron beam physical vapor deposition equipment. The current for heating the substrate is 0.15-0.25A, the current for evaporating the target is 1.1-1.5A, the substrate temperature is controlled between 800-900°C, the voltage is 15-18KV, the fixture rotation speed is 10-15r / min, and the vacuum degree is 1×10 -3 Pa to 9×10 -3 Pa, and the deposition time is 30-60min;

[0017] Step 3. Perform laser shock processing on the coating after vacuum heat treatment. The specific steps are as follows:

[0018] 3.1. Laser pretreatment: Coat an absorption layer and a constraint layer on the surface of the (γ’+γ)NiAlX protective coating;

[0019] 3.2. The specific process parameters for laser shock processing are as follows: Select a nanosecond laser with a wavelength of 1064nm, a pulse width of 20ns, a pulse energy of 2-6J, a spot diameter of 3mm, and an overlap rate of 30%, 50%, or 75%;

[0020] The overlap rate of the present invention can make the laser energy distribution more uniform; and the overlap can increase the shock wave generated by the laser, and the action effect (such as the increase in dislocation density and grain refinement) is more obvious.

[0021] Step 4. Put the obtained coating into a vacuum heat treatment furnace for vacuum heat treatment:

[0022] The vacuum heat treatment parameters are as follows: temperature 600 - 800 °C, time 2 - 4 h, and vacuum degree 1×10 -3 Pa to 9×10 -3 Pa.

[0023] The superalloys mentioned above can be nickel - based superalloy K3, directionally solidified superalloy DZ125, or single - crystal superalloy N5, DD6.

[0024] In the first step, the specimens are polished successively with 400# and 800# SiC sandpapers, sandblasted with a liquid sandblaster, and ultrasonically cleaned with acetone for 10 - 20 min.

[0025] The specific operations of cleaning and drying in step 2.1 are as follows: the high - purity raw materials are ultrasonically cleaned in alcohol for 20 - 30 min first, and then dried in an oven for 20 - 30 min. The oven temperature is 100 - 120 °C; the purity of the high - purity raw materials is 99.9 wt.%.

[0026] The sandblasting sand grains in the first step are quartz sand with 100 - 200 mesh, the sandblasting pressure is 2 - 3 bar, and the sandblasting time is 10 - 15 s.

[0027] The thickness of the (γ’ + γ)NiAlX protective coating in the second step is 80 - 120 μm, and the deviation of the actual content of each element in the coating from the designed content is less than 2 wt.%.

[0028] In the laser shock peening in the third step, the circular light spot is fabricated layer by layer from top to bottom in the horizontal direction, and the light spot scanning mode is serpentine scanning.

[0029] In step 3.1, the absorbing layer material is black tape with a thickness of 0.1 mm, and the constraining layer material is flowing water with a thickness of 1.5 mm.

[0030] Preferably, in step 2.1, the ingot is cut by wire - cutting.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) Through the laser shock peening process of the present invention, a (γ’ + γ)NiAlX protective coating with dislocation density proliferation, grain refinement, and dispersed distribution of active elements can be obtained.

[0033] Through the vacuum heat treatment system of the present invention, the residual stress generated during the coating preparation process and the laser shock peening process can be eliminated, while retaining the characteristics of grain refinement and dislocation proliferation.

[0034] (2) The method of the present invention postpones the heat treatment process that is conventionally carried out before laser shock peening. Through analysis and experimental verification, a vacuum heat treatment regime suitable for the (γ’+γ)NiAlX protective coating of the present invention is obtained.

[0035] The multiplication of dislocation density and grain refinement in the coating provide additional channels for the outward diffusion of aluminum elements, reduce the critical aluminum content required for the formation of alumina, and thus can improve the oxidation resistance of the coating. The internal residual compressive stress in the coating increases the oxidation rate of the coating and reduces the adhesion of the oxide film, thereby reducing the oxidation resistance of the coating.

[0036] If the heat treatment temperature is too high (such as 1000-1100 °C), it will cause grain growth and a decrease in dislocation density, offsetting the beneficial effect of laser shock peening in improving the oxidation performance of the coating. The vacuum heat treatment regime of the present invention sets the temperature in the range of 600-800 °C, which can not only eliminate residual stress, but also maintain grain refinement and a relatively high dislocation density inside the coating; placing the vacuum heat treatment as the last step can also completely eliminate the internal residual compressive stress during the coating preparation process and after laser shock peening.

[0037] (3) The (γ’+γ)NiAlX coating obtained by the process treatment of the present invention can rapidly form a protective alumina film at 1100 °C, with a significantly reduced oxidation rate and excellent oxidation resistance; when oxidized at 1100 °C for 100 hours, the thickness of the interdiffusion zone with the substrate is less than 30 μm.

[0038] (4) For the (γ’+γ)NiAlX protective coating prepared by the method of the present invention, its oxidation resistance is not affected by the composition of the superalloy substrate, while the coating prepared by the traditional preparation method is greatly affected by the alloy composition. Description of the Drawings

[0039] Figure 1 is a schematic diagram of the laser shock peening process;

[0040] Figure 2 is the surface morphology of the (γ’+γ)NiAlX coating before and after laser shock peening;

[0041] Figure 3 is the cross-sectional morphology of the (γ’+γ)NiAlX coating after isothermal oxidation for 100 h;

[0042] Figure 4 is the coating / substrate interface morphology of the (γ’+γ)NiAlX coating after isothermal oxidation for 100 h.

[0043] Figure 5 is the surface morphology of the oxide film at the initial stage of oxidation of the (γ’+γ)NiAlX coating. Detailed Description of the Invention

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0045] The features of various aspects of the embodiments of the present invention will be described in detail below. In the following detailed description, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those of ordinary skill in the art that the present invention can also be implemented without these specific details. The following description of the embodiments is only for a better understanding of the present invention by showing examples of the present invention. The present invention is not limited to any specific settings and methods provided below, but covers all product structures, any improvements and replacements of methods, etc. without departing from the spirit of the present invention. In the various drawings and the following description, well-known structures and technologies are not shown to avoid unnecessarily obscuring the present invention.

[0046] Example 1

[0047] Step 1: Substrate pretreatment

[0048] The substrate alloy used is N5 single-crystal superalloy. The substrate is cut into specimens with a specification of by wire electrical discharge machining. Holes with a size of are cut at both ends of the specimens to facilitate hanging the specimens on the bracket during coating deposition. The specimens are polished successively with 400# and 800# SiC sandpapers, and then sandblasted with a liquid sandblaster to increase the bonding strength at the coating / substrate interface. The sand grains are 200-mesh quartz sand, the sandblasting pressure is 2 bar, and the sandblasting time is 10 s. The sandblasted specimens are ultrasonically cleaned with acetone for 10 min, dried, and reserved for use.

[0049] Step 2: Preparation of (γ’+γ)NiAlX protective coating by electron beam physical vapor deposition

[0050] (1) Target preparation

[0051] Ni with a purity of 99.9wt.%, Al with a purity of 99.9wt.%, and Hf with a purity of 99.9wt.% are used as raw materials, and the ingredients are prepared according to the composition of Al: 25at.%, Hf: 1at.%, and Ni: Balance, with a total weight of 2000g. The weighed raw materials are ultrasonically cleaned in alcohol for 30 minutes, and then placed in an oven for drying for 30 minutes at a temperature of 120°C; the cleaned raw materials are placed in a vacuum induction melting furnace and heated to 3×10 -2 Pa, current 700A, (γ'+γ)NiAlHf ingot was obtained; then the ingot was heated at 1200℃ for 20h and vacuum degree 5×10 -3 The heat-treated ingot is cut into pieces of size by wire cutting. Target material.

[0052] (2) Deposition of (γ'+γ)NiAlX coating

[0053] The high-temperature alloy sample after the first step of pretreatment is mounted on the rotating fixture in the electron beam physical vapor deposition equipment. The current of heating the substrate is 0.2A, and the target material is evaporated.

[0054] The current is 1.3A, the substrate temperature is between 850℃, the voltage is 16KV, the fixture speed is 12r / min, and the vacuum degree is 5×10 -3 Pa, deposition time 45 min.

[0055] The third step is to perform laser shock strengthening on the heat-treated coating.

[0056] A 0.1 mm black tape was coated on the surface of the (γ'+γ)NiAlX protective coating as an absorption layer, and a 1.5 mm thick flowing water was used as a protective layer. A nanosecond laser was used for laser shock treatment, and the spot scanning mode was a serpentine scanning from top to bottom in the horizontal direction. The pulse width was selected to be 20 ns, the pulse energy was 4 J, the spot diameter was 3 mm, and the overlap rate was 50%.

[0057] The fourth step is to place the deposited coating into a vacuum heat treatment furnace for vacuum heat treatment;

[0058] The vacuum heat treatment parameters are: temperature 750°C, time 4h, vacuum degree 5×10 -3 Pa.

[0059] like Figure 2 As shown in a, the surface of the coating prepared by electron beam physical vapor deposition presents a typical columnar crystal head morphology, and the average grain size is about 20μm. After laser shock, the columnar crystal morphology of some parts of the coating surface is destroyed, and micro-pits and grooves appear locally ( Figure 2b). After 100 h of oxidation, the oxide film of the unimpacted specimen consists of an outer spinel layer and an inner alumina layer, and there is an obvious phenomenon of inconsistent thickness ( Figure 3 a); The oxide film on the surface of the specimen treated by laser is flat and dense, consisting of single alumina ( Figure 3 b), indicating that the laser shock peening process can significantly improve the oxidation resistance of the (γ’ + γ)NiAlX coating.

[0060] Example 2

[0061] The first step: Substrate pretreatment

[0062] The substrate alloy used is the DD6 single crystal superalloy. The substrate is cut into specimens with a specification of by wire electrical discharge machining. Holes of are cut at both ends of the specimen to facilitate hanging the specimen on the bracket during coating deposition. The specimen is polished successively with 400# and 800# SiC sandpapers, and then sandblasted with a liquid sandblaster to increase the bonding strength at the coating / substrate interface. The sand grains are 100-mesh quartz sand, the sandblasting pressure is 2 bar, and the sandblasting time is 15 s. The sandblasted specimen is ultrasonically cleaned with acetone for 15 min, dried, and reserved.

[0063] The second step: Preparation of the (γ’ + γ)NiAlX protective coating by electron beam physical vapor deposition

[0064] Ingredients are proportioned according to Al: 20 at.%, Zr: 0.5 at.%, Y: 0.5 at.%, Ni: Balance, with a total weight of 2000 g. The weighed raw materials are ultrasonically cleaned in alcohol for 20 min, and then dried in an oven at 120 °C for 20 min; The cleaned raw materials are put into a vacuum induction melting furnace, and under the conditions of a vacuum degree of 3×10 -2 Pa and a current of 800 A, a (γ’ + γ)NiAlX ingot is obtained; Subsequently, the ingot is subjected to homogenization annealing treatment at a temperature of 1300 °C for 20 h and a vacuum degree of 5×10 -3 Pa. The heat-treated ingot is cut into targets with a size of by wire electrical discharge machining.

[0065] (2) Deposition of the (γ’ + γ)NiAlX coating

[0066] The high-temperature alloy specimen pretreated in the first step is installed on the rotating fixture of the electron beam physical vapor deposition equipment. The current for heating the substrate is 0.2 A, the current for evaporating the target is 1.5 A, the substrate temperature is between 900 °C, the voltage is 16 kV, the fixture rotation speed is 12 r / min, the vacuum degree is 5×10 -3 Pa, and the deposition time is 60 min.

[0067] Step 3: Laser shock peening is carried out on the heat-treated coating.

[0068] A 0.1 mm thick black tape is coated on the surface of the (γ’+γ)NiAlX protective coating as an absorption layer, and 1.5 mm thick flowing water is used as a protective layer. A nanosecond laser is used for laser shock treatment, and the spot scanning mode is serpentine scanning from top to bottom in the horizontal direction. The pulse width is selected to be 20 ns, the pulse energy is 5 J, the spot diameter is 3 mm, and the overlap rate is 75%.

[0069] Step 4: The deposited coating is put into a vacuum heat treatment furnace for vacuum heat treatment;

[0070] The vacuum heat treatment parameters are: temperature 800 °C, time 4 h, and vacuum degree 5×10 -3 Pa.

[0071] The coating prepared by electron beam physical vapor deposition has a thickness of 100 μm. After oxidation at 1100 °C for 100 h, the thickness of the interdiffusion zone below the coating / substrate interface is about 24 μm, indicating that the (γ’+γ)NiAlX coating and the single crystal alloy interface have good interfacial compatibility.

[0072] Example 3

[0073] Step 1: Substrate pretreatment

[0074] The substrate alloy used is DZ125 directionally solidified superalloy. The substrate is cut into specimens with a specification of specimens, and holes are cut at both ends of the specimens so as to hang the specimens on the bracket when depositing the coating. The specimens are polished successively with 400# and 800# SiC sandpapers, and the polished specimens are sandblasted with a liquid sandblaster to increase the bonding strength of the coating / substrate interface. The sand grains are 100-mesh quartz sand, the sandblasting pressure is 2 bar, and the sandblasting time is 10 s. The sandblasted specimens are ultrasonically cleaned with acetone for 20 min, dried, and reserved.

[0075] Step 2: Prepare (γ’+γ)NiAlX protective coating by electron beam physical vapor deposition

[0076] According to the composition of Al: 30 at.%, Zr: 0.5 at.%, Y: 0.5 at.%, Ni: Balance, the total weight is 2000 g. The weighed raw materials are ultrasonically cleaned in alcohol for 20 min, and then dried in an oven for 20 min. The oven temperature is 100 °C; the cleaned raw materials are put into a vacuum induction melting furnace, and the vacuum degree is 3×10 -2Under the condition of Pa and a current of 800 A, an (γ’+γ)NiAlX ingot was obtained; subsequently, the ingot was subjected to homogenization annealing at a temperature of 1300 °C for 20 h and a vacuum degree of 5×10 -3 Pa. The heat-treated ingot was cut into a target with a size of by wire cutting.

[0077] (2) Depositing an (γ’+γ)NiAlX coating

[0078] The superalloy specimen pretreated in the first step was installed on the rotating fixture of the electron beam physical vapor deposition equipment. The current for heating the substrate was 0.2 A, the current for evaporating the target was 1.3 A, the substrate temperature was between 900 °C, the voltage was 16 KV, the fixture rotation speed was 12 r / min, and the vacuum degree was 5×10 -3 Pa, and the deposition time was 45 min.

[0079] In the third step, the heat-treated coating was subjected to laser shock peening.

[0080] A 0.1-mm-thick black tape was coated on the surface of the (γ’+γ)NiAlX protective coating as an absorption layer, and 1.5-mm-thick flowing water was used as a protective layer. A nanosecond laser was used for laser shock treatment. The spot scanning mode was serpentine scanning from top to bottom in the horizontal direction. The pulse width was selected to be 20 ns, the pulse energy was 4 J, the spot diameter was 3 mm, and the overlap rate was 75%.

[0081] In the fourth step, the deposited coating was put into a vacuum heat treatment furnace for vacuum heat treatment;

[0082] The vacuum heat treatment parameters were: temperature 800 °C, time 4 h, and vacuum degree 5×10 -3 Pa.

[0083] Coating specimens obtained through the first three steps of Example 3 were selected. Among them, specimens 1, 2, and 3 were subjected to vacuum heat treatment in the fourth step, and specimens 4, 5, and 6 were not subjected to vacuum heat treatment. Table 1 below is a comparison table of the internal residual stress data of the (γ’+γ)NiAlX coating:

[0084] Table 1 Internal residual stress of the (γ’+γ)NiAlX coating

[0085] Specimen Residual stress (MPa) Specimen 1 10 Specimen 2 7 Specimen 3 25 Specimen 4 -604 Specimen 5 -561 Specimen 6 -687

[0086] As shown in Table 1, the internal stress of the coating after vacuum heat treatment is at a relatively low level, with an average value of 14 MPa, showing tensile stress; while for the coating without vacuum heat treatment, the internal stress of the coating is at a relatively high level, with an average value of -586 Mpa, and the surface is compressive stress.

[0087] In the initial stage of oxidation, the residual stress inside the coating is rapidly released, resulting in severe plastic deformation. The surface of the coating fluctuates severely, and the oxide film cannot deform synergistically, leading to poor adhesion of the oxide film, as Figure 5 shown.

[0088] In addition, we also obtained coating specimens according to the process of Example 3 (1 to 6 in Table 2), and compared the properties and microstructures of specimens 1 to 3 after conventional heat treatment process (system: 1050 °C, 4 h) with those of specimens 4 to 6 after the heat treatment process of the present invention (system: 700 °C, 4 h). As shown in Table 2 below, Table 2 shows the comparison of the surface residual stress and average grain size of the (γ’+γ)NiAlX coating after different heat treatment processes:

[0089] Table 2 Residual stress and average grain size of the (γ’+γ)NiAlX coating under different heat treatment processes

[0090] Specimen Residual stress (MPa) Average grain size (μm) Specimen 1 10 2.3 Specimen 2 7 1.8 Specimen 3 25 3.1 Specimen 4 21 11 Specimen 5 12 16 Specimen 6 15 15

[0091] As shown in Table 2, both heat treatment processes can eliminate the internal residual compressive stress during the coating preparation process and after laser shock. However, when using the heat treatment process of the present invention, the average grain size inside the coating is 2.4 μm, while when using the conventional heat treatment process, the average grain size inside the coating is 14 μm. The smaller the grain size, the more grain boundaries there are. Grain boundaries provide a fast diffusion channel for aluminum ions, which is conducive to the rapid formation of a dense and continuous protective alumina film on the coating surface, thereby improving the oxidation resistance of the coating.

Claims

1. A method for improving the high-temperature oxidation resistance of a (γ’ + γ) NiAlX protective coating, characterized in that The method includes the following steps: Step 1. Pretreatment of superalloy matrix specimens: The matrix specimens are polished with SiC sandpaper and then subjected to sandblasting. After sandblasting, the specimens are ultrasonically cleaned and dried. The superalloy matrix is nickel-based superalloy K3, directionally solidified superalloy DZ125, single crystal superalloy N5, or DD6. Step 2. Preparation of (γ’+γ)NiAlX protective coating by electron beam physical vapor deposition method: The atomic content percentage of the components of the (γ’+γ)NiAlX protective coating is: 10-25% Al, 0.05-2% X, and the rest is Ni. X is one or several of Zr and Y. 2.

1. Prepare evaporation targets: Weigh and prepare high-purity raw materials according to the composition measurement. After cleaning and drying, conduct vacuum induction melting under the conditions of a vacuum degree of 1×10 -3 Pa to 5×10 -2 Pa and a current of 650 - 950 A to prepare (γ’+γ)NiAlX ingots; Subsequently, the ingot was subjected to homogenization annealing at a temperature of 1200 ± 50 °C for 20 - 24 h and a vacuum degree of 1×10 -3 Pa to 5×10 -2 Pa; The annealed ingot is cut into targets with required dimensions. 2.

2. Deposit (γ’+γ)NiAlX coating: Install the superalloy substrate after the first-step pretreatment on the rotating fixture inside the electron beam physical vapor deposition equipment. The current for heating the substrate is 0.15 - 0.25 A, the current for evaporating the target is 1.1 - 1.5 A, the substrate temperature is controlled between 800 - 900 °C, the voltage is 15 - 18 KV, the rotational speed of the fixture is 10 - 15 r / min, the vacuum degree is 1×10 -3 Pa to 9×10 -3 Pa, and the deposition time is 30 - 60 min; Step 3. Perform laser shock treatment on the coating after vacuum heat treatment. The specific steps are as follows: 3.

1. Laser pretreatment: A layer of absorption layer and constraint layer is coated on the surface of the (γ’+γ)NiAlX protective coating. 3.

2. The specific process parameters of laser shock treatment are: a nanosecond laser is selected, with a wavelength of 1064 nm, a pulse width of 20 ns, a pulse energy of 2-6 J, a spot diameter of 3 mm, and a lap rate of 30%, 50%, or 75%. Step 4. Put the obtained coating into a vacuum heat treatment furnace for vacuum heat treatment: The vacuum heat treatment parameters are: temperature 600 - 800 °C, time 2 - 4 h, vacuum degree 1×10 -3 Pa to 9×10 -3 Pa.

2. The method according to claim 1, characterized in that, In Step 1, the specimens are polished with 400# and 800# SiC sandpaper in sequence, subjected to sandblasting with a liquid sandblaster, and ultrasonically cleaned with acetone for 10-20 min.

3. The method according to claim 1, characterized in that, The specific operation of cleaning and drying in Step 2.1: The high-purity raw materials are ultrasonically cleaned in alcohol for 20-30 min, and then put into an oven to be dried for 20-30 min. The oven temperature is 100-120 °C.

4. The method according to claim 1, wherein The purity of the high-purity raw materials in Step 2.1 is 99.9 wt.%.

5. The method according to claim 1, wherein The sand grains for sandblasting in Step 1 are 100-200 mesh quartz sand, the sandblasting pressure is 2-3 bar, and the sandblasting time is 10-15 s.

6. The method according to claim 1, wherein The thickness of the (γ’+γ)NiAlX protective coating in Step 2 is 80-120 μm, and the deviation between the actual content and the designed content of each element in the coating is less than 2 wt.%.

7. The method according to claim 1, wherein In the laser shock strengthening in Step 3, the circular spot scans in a snake shape along the horizontal direction.

8. The method according to claim 1, characterized in that, In Step 3.1, the material of the absorption layer is black tape with a thickness of 0.1 mm, and the material of the constraint layer is flowing water with a thickness of 1.5 mm.

9. The method according to claim 1, wherein In Step 2.1, the ingot is cut by wire cutting.

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