A composite structure rare earth modified tungsten coating and its preparation method

Abstract

The present invention relates to a composite structure rare earth modified tungsten coating and a preparation method thereof. The method uses a chemical vapor deposition process with Gd particles, Sm particles, WF6 gas and related process gases as raw materials to prepare an antioxidant coating with a composite structure of Gd2C3 / W / Sm2O3 on the surface of a cobalt-based superalloy. By controlling factors such as the heating temperature of the vacuum chamber of the chemical vapor deposition equipment, the vacuum degree, the temperature of the external reaction generator, the flow rate of the process gas, and the deposition time, a composite structure antioxidant coating with a Gd2C3 interface layer, a W main phase coating, and a Sm2O3 blocking layer is prepared on the surface of the superalloy. This antioxidant coating has low oxygen vacancies, good compactness, a high coefficient of thermal expansion, stable high-temperature phases, and good interfacial chemical compatibility with the superalloy substrate. It is suitable for use in high-temperature oxidation corrosion environments above 1150 °C, can increase the working service temperature of turbine blade materials, and ensure that the substrate maintains good mechanical properties.

Description

Technical Field

[0001] The present invention relates to a composite structure rare earth modified tungsten coating and a preparation method thereof, belonging to the manufacturing technology of high temperature protective coatings. Background Art

[0002] High temperature protective coatings can provide effective anti-oxidation and anti-corrosion protection for metal materials used at high temperatures, and have been widely applied in the fields of aerospace, energy, petrochemical industry, etc. A representative application is in various gas turbine engines used in aircraft, ships and ground power generation. The development of high temperature protective coatings has mainly gone through three stages: the first generation of thermal diffusion coatings, the second generation of MCrAlYX cladding coatings; the third generation of thermal barrier coatings. In order to further improve the working efficiency of turbine engines and achieve the purpose of energy conservation and emission reduction, it is necessary to increase the inlet temperature of the engines. Therefore, scientific researchers have been constantly committed to developing more advanced materials, coating systems and preparation technologies. For example, the temperature-bearing capacity of the developed fourth-generation nickel-based single crystal superalloy has reached 1180°C. Correspondingly, higher requirements are also put forward for high temperature protective coatings, and a variety of new high temperature protective coatings with unique design concepts have emerged. The MCrAlYX cladding coating is the most widely used high temperature oxidation-resistant coating in the current period, and the long-term working temperature of this coating system is not higher than 1150°C. Since the content of Al element in the coating system is small and Al depletion is likely to occur under high temperature, the use of this coating system under higher service temperature conditions is restricted. The W coating has excellent properties such as high melting point, phase stability, wear resistance, etc., and is regarded as a potential high temperature oxidation-resistant coating material.

[0003] The main preparation methods of W coatings studied at home and abroad mainly include processes such as magnetron sputtering, supersonic flame spraying and chemical vapor deposition. Although the W coating prepared by magnetron sputtering has a relatively high density and a certain degree of columnar crystal structure in the microstructure, the physical vapor deposition rate of this process is very low and is not suitable for growing coatings of dozens of microns; the disadvantage of the supersonic flame spraying process is that it is difficult to meet the requirements of the interface bonding strength and columnar crystal microstructure of the oxidation-resistant coating under high temperature conditions, and the coating prepared by this process has many pores and obvious defect morphologies. Chemical vapor deposition is regarded as the best process method for preparing high-purity W coatings. The W coatings prepared by this process technology have been applied in the electronics and weapon industries. However, so far, there has been no report on the related research of W coatings as high temperature oxidation-resistant coatings on turbine blades, and there is a thermal expansion mismatch between the single W coating and the cobalt-based superalloy. The inherent pores in the W coating will accelerate the internal oxidation of the coating in a high temperature oxidation and corrosion environment, causing premature high temperature degradation and failure of the coating. Therefore, it is necessary to design a composite structure coating system for the existing chemical vapor deposition W coating process method, and through the regulation of coating preparation process parameters, to achieve the purpose of the high temperature oxidation and corrosion resistance of the composite coating. Summary of the Invention

[0004] The present invention is precisely designed and provided with a preparation method of a composite - structure rare - earth - modified tungsten coating in view of the above - mentioned existing technical situation. Its purpose is to make this kind of composite - structure rare - earth - modified tungsten coating have low oxygen vacancies, good compactness, high thermal expansion coefficient, stable high - temperature phase, and matching interfacial chemical compatibility with the superalloy matrix, be suitable for use in high - temperature oxidation and corrosion environments above 1150 °C, and can improve the working service temperature of turbine blade materials and ensure that the base material maintains good mechanical properties.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The composite - structure rare - earth - modified tungsten coating described in the present invention is applicable to the surface of cobalt - based superalloys and has a three - layer structure. From the surface of the cobalt - based superalloy upwards, they are Gd2C3 interface layer, W coating, and Sm2O3 blocking layer in sequence.

[0007] The preparation method of the composite - structure rare - earth - modified tungsten coating described in the present invention adopts the chemical vapor deposition process. The solid materials used in this preparation method are Gd particles and Sm particles, and the weight percentage contents of Gd element and Sm element are both greater than 99%; the process gases used in this preparation method are: H2 gas, Ar gas, HCl gas, CH4 gas, CO gas, CO2 gas, and WF6 gas; the steps of this preparation method include:

[0008] Step 1: Prepare a Gd2C3 interface layer on the surface of the cobalt - based superalloy. Its process parameters are: H2 gas flow rate 20 L / min - 28 L / min, Ar gas flow rate 10 L / min - 18 L / min, HCl gas flow rate 3.8 L / min - 4.4 L / min, CH4 gas flow rate 12 L / min - 22 L / min, temperature of the external GdCl3 reaction generator 630 °C - 670 °C, vacuum degree of the vacuum chamber 380 mbar - 420 mbar, heating temperature of the vacuum chamber 880 °C - 910 °C, deposition time 60 min - 90 min;

[0009] Step 2: Prepare a W coating on the Gd2C3 interface layer. Its process parameters are: H2 gas flow rate 32 L / min - 40 L / min, Ar gas flow rate 22 L / min - 30 L / min, WF6 gas flow rate 6.1 L / min - 6.7 L / min, vacuum degree of the vacuum chamber 150 mbar - 190 mbar, heating temperature of the vacuum chamber 1030 °C - 1070 °C, deposition time 300 min - 330 min;

[0010] Step 3: Prepare a Sm2O3 sealing layer on the W coating. The process parameters are as follows: H2 gas flow rate of 26 L / min to 34 L / min, HCl gas flow rate of 4.2 L / min to 4.8 L / min, CO gas flow rate of 15 L / min to 19 L / min, CO2 gas flow rate of 26 L / min to 34 L / min, temperature of the external SmCl3 reaction generator of 470 °C to 510 °C, vacuum degree of the vacuum chamber of 80 mbar to 120 mbar, heating temperature of the vacuum chamber of 1100 °C to 1140 °C, and deposition time of 60 min to 90 min.

[0011] During implementation, the sizes of both the Gd particles and the Sm particles are Φ10 mm × 4 mm.

[0012] During implementation, in this preparation method, after the Sm2O3 sealing layer is prepared, isothermal heat treatment is carried out in the same vacuum chamber. The process parameters are as follows: H2 gas flow rate of 45 L / min, Ar gas flow rate of 15 L / min, vacuum degree of the vacuum chamber of 60 mbar, heating temperature of the vacuum chamber of 1160 °C, and isothermal time of 180 min.

[0013] During implementation, the process parameters of the three steps of this preparation method are as follows:

[0014] Step 1: The process parameters for preparing a Gd2C3 interface layer on the cobalt-based superalloy surface are as follows: H2 gas flow rate of 20 L / min, Ar gas flow rate of 18 L / min, HCl gas flow rate of 4.4 L / min, CH4 gas flow rate of 12 L / min, temperature of the external GdCl3 reaction generator of 670 °C, vacuum degree of the vacuum chamber of 420 mbar, heating temperature of the vacuum chamber of 880 °C, and deposition time of 60 min;

[0015] Step 2: The process parameters for preparing a W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate of 40 L / min, Ar gas flow rate of 22 L / min, WF6 gas flow rate of 6.7 L / min, vacuum degree of the vacuum chamber of 150 mbar, heating temperature of the vacuum chamber of 1030 °C, and deposition time of 330 min;

[0016] Step 3: The process parameters for preparing a Sm2O3 sealing layer on the W coating are as follows: H2 gas flow rate of 26 L / min, HCl gas flow rate of 4.2 L / min, CO gas flow rate of 19 L / min, CO2 gas flow rate of 26 L / min, temperature of the external SmCl3 reaction generator of 510 °C, vacuum degree of the vacuum chamber of 120 mbar, heating temperature of the vacuum chamber of 1140 °C, and deposition time of 60 min.

[0017] During implementation, the process parameters of the three steps of this preparation method are as follows:

[0018] Step 1. The process parameters for preparing the Gd2C3 interface layer on the cobalt-based superalloy are as follows: H2 gas flow rate of 28 L / min, Ar gas flow rate of 10 L / min, HCl gas flow rate of 3.8 L / min, CH4 gas flow rate of 22 L / min, temperature of the external GdCl3 reaction generator of 630 °C, vacuum degree of the vacuum chamber of 380 mbar, heating temperature of the vacuum chamber of 910 °C, and deposition time of 90 min;

[0019] Step 2. The process parameters for preparing the W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate of 32 L / min, Ar gas flow rate of 30 L / min, WF6 gas flow rate of 6.1 L / min, vacuum degree of the vacuum chamber of 190 mbar, heating temperature of the vacuum chamber of 1070 °C, and deposition time of 300 min;

[0020] Step 3. The process parameters for preparing the Sm2O3 blocking layer on the W coating are as follows: H2 gas flow rate of 34 L / min, HCl gas flow rate of 4.8 L / min, CO gas flow rate of 15 L / min, CO2 gas flow rate of 34 L / min, temperature of the external SmCl3 reaction generator of 470 °C, vacuum degree of the vacuum chamber of 80 mbar, heating temperature of the vacuum chamber of 1100 °C, and deposition time of 90 min.

[0021] During implementation, the process parameters for the three steps of this preparation method are respectively:

[0022] Step 1. The process parameters for preparing the Gd2C3 interface layer on the cobalt-based superalloy are as follows: H2 gas flow rate of 24 L / min, Ar gas flow rate of 14 L / min, HCl gas flow rate of 4.1 L / min, CH4 gas flow rate of 17 L / min, temperature of the external GdCl3 reaction generator of 650 °C, vacuum degree of the vacuum chamber of 400 mbar, heating temperature of the vacuum chamber of 895 °C, and deposition time of 75 min;

[0023] Step 2. The process parameters for preparing the W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate of 36 L / min, Ar gas flow rate of 26 L / min, WF6 gas flow rate of 6.4 L / min, vacuum degree of the vacuum chamber of 170 mbar, heating temperature of the vacuum chamber of 1050 °C, and deposition time of 315 min;

[0024] Step 3. The process parameters for preparing the Sm2O3 blocking layer on the W coating are as follows: H2 gas flow rate of 30 L / min, HCl gas flow rate of 4.5 L / min, CO gas flow rate of 17 L / min, CO2 gas flow rate of 30 L / min, temperature of the external SmCl3 reaction generator of 490 °C, vacuum degree of the vacuum chamber of 100 mbar, heating temperature of the vacuum chamber of 1120 °C, and deposition time of 75 min.

[0025] During implementation, the purity of the process gas is greater than 99.99%.

[0026] The technical solution of the present invention has the following characteristics and beneficial effects:

[0027] 1. A three-layer composite structure coating system is designed, with Gd2C3 as the interface layer, which can not only alleviate the thermal expansion mismatch between the cobalt-based superalloy and the W coating, but also act as an element interdiffusion barrier layer to avoid the outward diffusion of cobalt-based superalloy elements caused by the concentration gradient difference between components under high-temperature action and reduce the phase structure stability of the W coating. Using Sm2O3 as the sealing layer can prevent the inward diffusion of high-temperature oxidation corrosion atmosphere into the pores of the W coating and reduce the high-temperature oxidation corrosion rate of the W coating;

[0028] 2. When preparing the W main-phase coating, based on H2 as the reducing gas, Ar gas with a flow rate of not less than 22 L / min is introduced. This can not only increase the carrier diffusion rate of WF6 gas, enable the reaction source gas to fully undergo a displacement reaction on the surface of the cobalt-based superalloy and deposit the W coating, but also ensure the reduction of the oxygen atmosphere concentration in the vacuum chamber to avoid the oxidation reaction of the pores in the W coating under the action of a high temperature of 1030 °C, thereby reducing the high-temperature oxidation resistance of the W coating. Setting the flow rate of H2 gas to be greater than 32 L / min can effectively promote the full reduction of WF6 gas and dilute the concentration ratio of the reaction product HF to avoid the formation of pitting pits on the surface of the W coating;

[0029] 3. When preparing the Sm2O3 sealing layer, H2 gas and CO2 gas are selected to react under high-temperature vacuum to form an H2O atmosphere, and then an appropriate amount of CO gas is introduced. This can ensure that above 1100 °C, the SmCl3 precursor reacts with the sufficient gaseous H2O atmosphere to form the Sm2O3 sealing layer. At this time, setting the reaction vacuum degree to be lower than 120 mbar can reduce the nucleation and growth rate of Sm2O3, thereby avoiding the generation of coarse and loose Sm2O3 powdered particles due to too fast reaction rate, and inhibiting the formation of a dense sealing layer of Sm2O3 due to the excessive accumulation of large powdered particles in the initial stage of the reaction. Specific Embodiments

[0030] The technical solution of the present invention will be further described in detail below in conjunction with embodiments:

[0031] In the following embodiments, the equipment for preparing the composite structure rare earth modified tungsten coating is a chemical vapor deposition equipment.

[0032] Example 1:

[0033] The steps for preparing the composite structure rare earth modified tungsten coating according to the technical solution of the present invention are as follows:

[0034] Step 1. Pretreatment of the cobalt-based superalloy:

[0035] Pre-grind with 800-mesh sandpaper to remove residues on the surface of the superalloy; before cleaning, perform water blasting treatment with a water blasting machine to remove the scale on the surface of the superalloy. The sand grains are below 125 μm and the working pressure is 0.4 MPa; after water blasting, rinse with tap water, soak in deionized water, dehydrate with alcohol, and dry.

[0036] Step 2: Prepare a composite structure rare earth-modified tungsten coating:

[0037] Load the cobalt-based superalloy into the fixture, insert the fixture into the air outlet of the gas duct tooling, evacuate and perform equipment pressure holding test. In the same reaction vacuum chamber of the chemical vapor deposition equipment, first prepare a Gd2C3 interface layer, then prepare a W coating, and finally prepare a Sm2O3 blocking layer; the deposition process parameters for preparing the composite structure Gd2C3 / W / Sm2O3 antioxidant coating are as follows:

[0038] The preparation parameters for the Gd2C3 interface layer are: H2 gas flow rate 20 L / min, Ar gas flow rate 18 L / min, HCl gas flow rate 4.4 L / min, CH4 gas flow rate 12 L / min, temperature of the external GdCl3 reaction generator 670 °C, vacuum degree of the vacuum chamber 420 mbar, heating temperature of the vacuum chamber 880 °C, deposition time 60 min;

[0039] The preparation parameters for the W coating are: H2 gas flow rate 40 L / min, Ar gas flow rate 22 L / min, WF6 gas flow rate 6.7 L / min, vacuum degree of the vacuum chamber 150 mbar, heating temperature of the vacuum chamber 1030 °C, deposition time 330 min;

[0040] The preparation parameters for the Sm2O3 blocking layer are: H2 gas flow rate 26 L / min, HCl gas flow rate 4.2 L / min, CO gas flow rate 19 L / min, CO2 gas flow rate 26 L / min, temperature of the external SmCl3 reaction generator 510 °C, vacuum degree of the vacuum chamber 120 mbar, heating temperature of the vacuum chamber 1140 °C, deposition time 60 min;

[0041] Step 3: Coating constant temperature treatment:

[0042] When the Sm2O3 blocking layer is prepared, stop introducing HCl, CO, and CO2 gases, and only retain the introduction of H2 and Ar gases. Reset the heating temperature and vacuum degree of the vacuum chamber. The process parameters for coating constant temperature heat treatment in the same vacuum chamber are: H2 gas flow rate 45 L / min, Ar gas flow rate 15 L / min, vacuum degree of the vacuum chamber 60 mbar, heating temperature of the vacuum chamber 1160 °C, constant temperature time 180 min.

[0043] Example 2:

[0044] The steps for preparing the composite structure rare earth modified tungsten coating according to the technical solution of the present invention are as follows:

[0045] Step 1. Pretreatment of cobalt-based superalloy:

[0046] Use 800-mesh sandpaper to pre-grind to remove the residues on the surface of the superalloy; before cleaning, use a water blasting machine to perform water blasting treatment to remove the oxide scale on the surface of the superalloy, with sand grains below 125 μm and a working pressure of 0.4 MPa; after water blasting, rinse with tap water, soak in deionized water, dehydrate with alcohol, and dry.

[0047] Step 2. Preparation of the composite structure rare earth modified tungsten coating:

[0048] Load the cobalt-based superalloy into the fixture and insert the fixture into the air outlet of the gas pipe tooling, evacuate and perform equipment pressure holding test. In the same reaction vacuum chamber of the chemical vapor deposition equipment, first prepare a Gd2C3 interface layer, then prepare a W coating, and finally prepare a Sm2O3 sealing layer; the deposition process parameters for preparing the composite structure Gd2C3 / W / Sm2O3 antioxidant coating are as follows:

[0049] The preparation parameters for the Gd2C3 interface layer are: H2 gas flow rate 28 L / min, Ar gas flow rate 10 L / min, HCl gas flow rate 3.8 L / min, CH4 gas flow rate 22 L / min, temperature of the external GdCl3 reaction generator 630 °C, vacuum degree of the vacuum chamber 380 mbar, heating temperature of the vacuum chamber 910 °C, deposition time 90 min;

[0050] The preparation parameters for the W coating are: H2 gas flow rate 32 L / min, Ar gas flow rate 30 L / min, WF6 gas flow rate 6.1 L / min, vacuum degree of the vacuum chamber 190 mbar, heating temperature of the vacuum chamber 1070 °C, deposition time 300 min;

[0051] The preparation parameters for the Sm2O3 sealing layer are: H2 gas flow rate 34 L / min, HCl gas flow rate 4.8 L / min, CO gas flow rate 15 L / min, CO2 gas flow rate 34 L / min, temperature of the external SmCl3 reaction generator 470 °C, vacuum degree of the vacuum chamber 80 mbar, heating temperature of the vacuum chamber 1100 °C, deposition time 90 min;

[0052] Step 3. Coating constant temperature treatment:

[0053] After the preparation of the Sm2O3 blocking layer is completed, the feeding of HCl, CO, and CO2 gases is stopped, and only the feeding of H2 and Ar gases is retained. Then, the heating temperature and vacuum degree of the vacuum chamber are reset. The process parameters for the isothermal heat treatment of the coating in the same vacuum chamber are as follows: the flow rate of H2 gas is 45 L / min, the flow rate of Ar gas is 15 L / min, the vacuum degree of the vacuum chamber is 60 mbar, the heating temperature of the vacuum chamber is 1160 °C, and the isothermal time is 180 min.

[0054] Example 3:

[0055] The steps for preparing the composite structure rare earth modified tungsten coating according to the technical solution of the present invention are as follows:

[0056] Step 1. Pretreatment of cobalt-based superalloy:

[0057] Use 800-mesh sandpaper to pre-grind and remove the residues on the surface of the superalloy; before cleaning, use a water blasting machine to perform water blasting treatment to remove the oxide scale on the surface of the superalloy. The sand grains are below 125 μm, and the working pressure is 0.4 MPa; after water blasting, rinse with tap water, soak in deionized water, dehydrate with alcohol, and dry.

[0058] Step 2. Preparation of the composite structure rare earth modified tungsten coating:

[0059] Load the cobalt-based superalloy into the fixture and insert the fixture into the air outlet of the gas pipe tooling, then evacuate and perform a pressure holding test on the equipment. In the same reaction vacuum chamber of the chemical vapor deposition equipment, first prepare a Gd2C3 interface layer, then prepare a W coating, and finally prepare a Sm2O3 blocking layer; the deposition process parameters for preparing the composite structure Gd2C3 / W / Sm2O3 antioxidant coating are as follows:

[0060] The preparation parameters for the Gd2C3 interface layer are: the flow rate of H2 gas is 24 L / min, the flow rate of Ar gas is 14 L / min, the flow rate of HCl gas is 4.1 L / min, the flow rate of CH4 gas is 17 L / min, the temperature of the external GdCl3 reaction generator is 650 °C, the vacuum degree of the vacuum chamber is 400 mbar, the heating temperature of the vacuum chamber is 895 °C, and the deposition time is 75 min;

[0061] The preparation parameters for the W coating are: the flow rate of H2 gas is 36 L / min, the flow rate of Ar gas is 26 L / min, the flow rate of WF6 gas is 6.4 L / min, the vacuum degree of the vacuum chamber is 170 mbar, the heating temperature of the vacuum chamber is 1050 °C, and the deposition time is 315 min;

[0062] The preparation parameters of the Sm2O3 blocking layer are as follows: the flow rate of H2 gas is 30 L / min, the flow rate of HCl gas is 4.5 L / min, the flow rate of CO gas is 17 L / min, the flow rate of CO2 gas is 30 L / min, the temperature of the external SmCl3 reaction generator is 490 °C, the vacuum degree of the vacuum chamber is 100 mbar, the heating temperature of the vacuum chamber is 1120 °C, and the deposition time is 75 min;

[0063] Step 3. Coating constant temperature treatment:

[0064] After the Sm2O3 blocking layer is prepared, stop introducing HCl, CO, and CO2 gases, and only retain the introduction of H2 and Ar gases. Reset the heating temperature and vacuum degree of the vacuum chamber. The process parameters for the coating constant temperature heat treatment in the same vacuum chamber are as follows: the flow rate of H2 gas is 45 L / min, the flow rate of Ar gas is 15 L / min, the vacuum degree of the vacuum chamber is 60 mbar, the heating temperature of the vacuum chamber is 1160 °C, and the constant temperature time is 180 min.

[0065] Compared with the prior art, the technical solution of the present invention designs a three-layer composite structure coating system. By reasonably controlling the generation rate of the GdCl3 and SmCl3 reaction precursors, with Gd2C3 as the interface layer, W as the main phase coating, and Sm2O3 as the blocking layer, a composite structure Gd2C3 / W / Sm2O3 anti-oxidation coating can be prepared on the surface of a cobalt-based superalloy in the same vacuum chamber. Moreover, the interfacial matching of the coating layers is good, the density is high, and the phase structure stability is excellent, which can improve the high-temperature oxidation and corrosion resistance of the blade material and avoid the decline of the mechanical properties of the alloy material.

Claims

1. A preparation method of a rare earth modified tungsten coating with a composite structure, characterized in that: The tungsten coating is applicable to the surface of cobalt-based superalloys and has a three-layer structure. From the surface of the cobalt-based superalloy upwards, there are a Gd2C3 interface layer, a W coating, and a Sm2O3 sealing layer in sequence. The preparation method uses a chemical vapor deposition process. The solid materials used in this preparation method are Gd particles and Sm particles, where the weight percentage contents of Gd element and Sm element are both greater than 99%; the process gases used in this preparation method are: H2 gas, Ar gas, HCl gas, CH4 gas, CO gas, CO2 gas, and WF6 gas; the steps of this preparation method include: Step 1: Prepare a Gd2C3 interface layer on the surface of the cobalt-based superalloy. The process parameters are: H2 gas flow rate 20 L / min - 28 L / min, Ar gas flow rate 10 L / min - 18 L / min, HCl gas flow rate 3.8 L / min - 4.4 L / min, CH4 gas flow rate 12 L / min - 22 L / min, temperature of the external GdCl3 reaction generator 630 °C - 670 °C, vacuum degree of the vacuum chamber 380 mbar - 420 mbar, heating temperature of the vacuum chamber 880 °C - 910 °C, deposition time 60 min - 90 min; Step 2: Prepare a W coating on the Gd2C3 interface layer. The process parameters are: H2 gas flow rate 32 L / min - 40 L / min, Ar gas flow rate 22 L / min - 30 L / min, WF6 gas flow rate 6.1 L / min - 6.7 L / min, vacuum degree of the vacuum chamber 150 mbar - 190 mbar, heating temperature of the vacuum chamber 1030 °C - 1070 °C, deposition time 300 min - 330 min; Step 3: Prepare a Sm2O3 sealing layer on the W coating. The process parameters are: H2 gas flow rate 26 L / min - 34 L / min, HCl gas flow rate 4.2 L / min - 4.8 L / min, CO gas flow rate 15 L / min - 19 L / min, CO2 gas flow rate 26 L / min - 34 L / min, temperature of the external SmCl3 reaction generator 470 °C - 510 °C, vacuum degree of the vacuum chamber 80 mbar - 120 mbar, heating temperature of the vacuum chamber 1100 °C - 1140 °C, deposition time 60 min - 90 min.

2. The preparation method of the composite structure rare earth modified tungsten coating according to claim 1, characterized in that: In this preparation method, after the Sm2O3 sealing layer is prepared, a constant-temperature heat treatment is carried out in the same vacuum chamber. The process parameters are H2 gas flow rate 45 L / min, Ar gas flow rate 15 L / min, vacuum degree of the vacuum chamber 60 mbar, heating temperature of the vacuum chamber 1160 °C, and constant-temperature time 180 min.

3. The preparation method of the composite structure rare earth modified tungsten coating according to claim 1, characterized in that: The process parameters of the three steps of this preparation method are respectively: Step 1. The process parameters for preparing the Gd2C3 interface layer on the surface of the cobalt-based superalloy are as follows: H2 gas flow rate 20 L / min, Ar gas flow rate 18 L / min, HCl gas flow rate 4.4 L / min, CH4 gas flow rate 12 L / min, temperature of the external GdCl3 reaction generator 670 °C, vacuum degree of the vacuum chamber 420 mbar, heating temperature of the vacuum chamber 880 °C, deposition time 60 min; Step 2. The process parameters for preparing the W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate 40 L / min, Ar gas flow rate 22 L / min, WF6 gas flow rate 6.7 L / min, vacuum degree of the vacuum chamber 150 mbar, heating temperature of the vacuum chamber 1030 °C, deposition time 330 min; Step 3. The process parameters for preparing the Sm2O3 sealing layer on the W coating are as follows: H2 gas flow rate 26 L / min, HCl gas flow rate 4.2 L / min, CO gas flow rate 19 L / min, CO2 gas flow rate 26 L / min, temperature of the external SmCl3 reaction generator 510 °C, vacuum degree of the vacuum chamber 120 mbar, heating temperature of the vacuum chamber 1140 °C, deposition time 60 min.

4. The preparation method of the composite structure rare earth modified tungsten coating according to claim 1, characterized in that: The process parameters for the three steps of this preparation method are as follows: Step 1. The process parameters for preparing the Gd2C3 interface layer on the surface of the cobalt-based superalloy are as follows: H2 gas flow rate 28 L / min, Ar gas flow rate 10 L / min, HCl gas flow rate 3.8 L / min, CH4 gas flow rate 22 L / min, temperature of the external GdCl3 reaction generator 630 °C, vacuum degree of the vacuum chamber 380 mbar, heating temperature of the vacuum chamber 910 °C, deposition time 90 min; Step 2. The process parameters for preparing the W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate 32 L / min, Ar gas flow rate 30 L / min, WF6 gas flow rate 6.1 L / min, vacuum degree of the vacuum chamber 190 mbar, heating temperature of the vacuum chamber 1070 °C, deposition time 300 min; Step 3. The process parameters for preparing the Sm2O3 sealing layer on the W coating are as follows: H2 gas flow rate 34 L / min, HCl gas flow rate 4.8 L / min, CO gas flow rate 15 L / min, CO2 gas flow rate 34 L / min, temperature of the external SmCl3 reaction generator 470 °C, vacuum degree of the vacuum chamber 80 mbar, heating temperature of the vacuum chamber 1100 °C, deposition time 90 min.

5. The preparation method of the composite structure rare earth modified tungsten coating according to claim 1, characterized in that: The process parameters for the three steps of this preparation method are as follows: Step 1. The process parameters for preparing the Gd2C3 interface layer on the surface of the cobalt-based superalloy are as follows: H2 gas flow rate 24 L / min, Ar gas flow rate 14 L / min, HCl gas flow rate 4.1 L / min, CH4 gas flow rate 17 L / min, temperature of the external GdCl3 reaction generator 650 °C, vacuum degree of the vacuum chamber 400 mbar, heating temperature of the vacuum chamber 895 °C, deposition time 75 min; Step 2: The process parameters for preparing the W coating on the Gd2C3 interface layer are as follows: H2 gas flow rate of 36 L / min, Ar gas flow rate of 26 L / min, WF6 gas flow rate of 6.4 L / min, vacuum degree of the vacuum chamber of 170 mbar, heating temperature of the vacuum chamber of 1050 °C, and deposition time of 315 min; Step 3: The process parameters for preparing the Sm2O3 blocking layer on the W coating are as follows: H2 gas flow rate of 30 L / min, HCl gas flow rate of 4.5 L / min, CO gas flow rate of 17 L / min, CO2 gas flow rate of 30 L / min, temperature of the external SmCl3 reaction generator of 490 °C, vacuum degree of the vacuum chamber of 100 mbar, heating temperature of the vacuum chamber of 1120 °C, and deposition time of 75 min.

6. The preparation method of the composite structure rare earth modified tungsten coating according to claim 1, characterized in that: The purity of the process gases is greater than 99.99%.