Cold cathode EB-PVD double-layer composite functional homogeneous ceramic coating and preparation method thereof

Abstract

The invention belongs to the technical field of thermal barrier coatings, and particularly discloses a cold cathode EB-PVD double-layer composite functional homogeneous ceramic coating and a preparation method thereof. The coating is of a double-layer structure formed by homogeneous ceramics, the inner layer is a compact ceramic coating, and the outer layer is a traditional columnar ceramic coating. According to the preparation method, a cold cathode electron gun EB-PVD technology is adopted, and the coating is prepared and obtained. According to the preparation method, the limitation that a compact coating is difficult to prepare through traditional hot cathode EB-PVD is broken through, and the prepared coating has excellent corrosion resistance and thermal comprehensive performance and is particularly suitable for aero-engine hot end components in the marine environment.

Description

Technical Field

[0001] This invention relates to the field of thermal barrier coating technology, specifically to a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating and its preparation method. Background Technology

[0002] Hot-end components such as turbine blades in advanced aero-engines need to operate under high-temperature conditions. Their surfaces typically require a thermal barrier coating composed of a ceramic coating and a metal bonding layer. The ceramic coating, as the outer layer, directly faces the high-temperature environment, providing high-temperature protection. The metal bonding layer, as the inner layer, contacts the high-temperature alloy substrate, mitigating the mismatch in thermal expansion coefficients between the ceramic coating and the substrate, and also providing high-temperature oxidation resistance. Ceramic coatings on turbine blade surfaces are usually prepared using techniques such as electron beam physical vapor deposition (EB-PVD), while metal bonding layers are typically prepared using techniques such as arc ion plating (AIP).

[0003] In recent years, with the surge in demand for advanced aero-engines in harsh environments such as the ocean, the corrosion problem of metal bonding layers has become increasingly prominent. Traditional EB-PVD ceramic coatings have a columnar structure with penetrating intergranular gaps. These gaps can achieve high strain tolerance through opening and closing during thermal cycling, thus endowing the coating with excellent overall thermodynamic properties. However, these intergranular gaps also constitute "short-circuit" diffusion channels for corrosive media to penetrate inward, resulting in insufficient corrosion resistance of the coating.

[0004] In existing technologies, traditional EB-PVD equipment uses a hot cathode secondary electron gun, which requires 10 -2 Operating in a vacuum environment on the order of Pa, excessively high vacuum chamber pressure will cause beam interruption. Due to this vacuum limitation, it is difficult to eliminate penetrating columnar intergranular gaps in the coating. Therefore, dense ceramic coatings are typically prepared using liquid-phase deposition methods such as spraying. For example, atmospheric plasma spraying (APS) is used to prepare layered coatings on the surface of EB-PVD columnar coatings; plasma spraying-physical vapor deposition (PS-PVD) is also used to prepare layered coatings. However, unlike the pure vapor-phase deposition mechanism of EB-PVD, the layered coatings formed by spraying are mainly based on liquid-phase deposition. The interfaces between coatings rely on mechanical bonding and cannot form strong chemical bonds, resulting in insufficient interfacial bonding strength. Therefore, the above technologies are currently insufficient to meet the requirements for preparing thermal barrier coatings on turbine blade surfaces. Summary of the Invention

[0005] The purpose of this invention is to provide a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating and a method for preparing the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] In a first aspect, the present invention provides a method for preparing a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating, the preparation steps of which include: Step 1: Evacuate the EB-PVD equipment equipped with a cold cathode electron gun until the pressure in the vacuum chamber is ≤1×10⁻⁶. -2 Pa; Step 2: Introduce high-voltage discharge reaction gas into the cold cathode evaporation gun and the cold cathode heating gun to make the pressure in the EB-PVD vacuum chamber 3×10⁻⁶. -1 ~5×10 -1 Pa; Step 3: Start the cold cathode heating gun to preheat the surface of the part to be treated to 600~700 ℃; Step 4: Start the cold cathode evaporation gun to vaporize the ceramic rod and deposit a dense ceramic coating on the surface of the preheated part to be treated, thereby obtaining a workpiece with a dense ceramic coating. Step 5: Turn off the cold cathode evaporation gun, increase the power of the cold cathode heating gun, and preheat the workpiece with the dense ceramic coating to 900~1000 ℃; Step 6: Restart the cold cathode evaporation gun to deposit a columnar ceramic coating in situ on the workpiece with a dense ceramic coating, thereby obtaining a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating.

[0008] In one embodiment of the present invention, in step two, the high-voltage discharge reaction gas introduced into the cold cathode evaporation gun is He gas and O2 gas, with a He flow rate of 180~270 mL / min and an O2 flow rate of 1.8~2.7 mL / min.

[0009] In one embodiment of the present invention, in step two, the high-voltage discharge reaction gas introduced into the cold cathode heating gun is He gas and O2 gas, with a He flow rate of 70~80 mL / min and an O2 flow rate of 1.4~1.6 mL / min.

[0010] In one embodiment of the present invention, in step three, the power of the electron beam output by the cold cathode heating gun is 9~11 kW, and the preheating time is controlled to be 5~15 min.

[0011] In one embodiment of the present invention, in step four, the power of the electron beam output by the cold cathode evaporation gun is 35~40 kW, and the deposition time is 10~15 min.

[0012] In one embodiment of the present invention, in step four, the pressure of the vacuum chamber is 1~5 Pa when depositing the dense ceramic coating.

[0013] In one embodiment of the present invention, in step five, the power of the electron beam output by the cold cathode heating gun is increased to 14~16 kW, and the preheating time is controlled to be 5~15 min.

[0014] In one embodiment of the present invention, in step six, the power of the electron beam output by the cold cathode evaporation gun is 35~40 kW, and the deposition time is 10~15 min.

[0015] In one embodiment of the present invention, in step six, the pressure of the vacuum chamber is 1~5 Pa when depositing the columnar ceramic coating.

[0016] In this invention, the same ceramic rods are used for both the deposition of dense ceramic coatings and the deposition of columnar ceramic coatings, forming a homogeneous ceramic coating. The ceramic rods used in this invention are the same as those used in the preparation of conventional EB-PVD ceramic coatings on turbine blade surfaces.

[0017] Secondly, the present invention provides a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating, comprising an inner layer and an outer layer, wherein the inner layer is a dense ceramic coating in contact with the surface of the part to be treated, and the outer layer is a columnar ceramic coating deposited on the dense ceramic coating.

[0018] As one embodiment of the present invention, the total thickness of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating is 120~180 μm, wherein the thickness of the dense ceramic coating is 60~90 μm, and the thickness of the columnar ceramic coating is 60~90 μm.

[0019] Thirdly, the present invention provides a component having the aforementioned cold cathode EB-PVD dual-layer composite functional homogeneous ceramic coating.

[0020] Fourthly, the present invention provides an application of a component having the aforementioned cold cathode EB-PVD dual-layer composite functional homogeneous ceramic coating in an aero-engine.

[0021] The present invention has the following beneficial effects: 1. The bilayer composite functional homogeneous ceramic coating prepared in this invention has an outer layer of traditional columnar ceramic coating with penetrating columnar intergranular spaces, which mainly undertakes high-temperature insulation and strain release functions, ensuring excellent comprehensive thermal performance of the coating; the inner layer is a dense ceramic coating, which can prevent marine corrosive media from penetrating into the deeper metal bonding layer and protect the lower metal bonding layer from corrosion, thus meeting the complex application requirements of thermo-mechanical coupling in marine environments; the inner and outer layers are homogeneous ceramic materials, which fundamentally avoids the problem of thermal stress at the interface due to the mismatch of thermal expansion coefficients of different materials. At the same time, the interface formed by in-situ vapor deposition is a strong chemical bond, which makes the bilayer structure form an extremely high interface bonding strength; 2. Traditional hot cathode EB-PVD technology is limited by vacuum level (~10). -2 It is difficult to prepare dense coatings under high pressure (1~5 Pa). This invention utilizes the characteristic that the cold cathode electron gun can work stably under high pressure (1~5 Pa) and combines it with a low substrate preheating temperature (600~700 ℃) to eliminate through-penetrating columnar interstices and realize the controllable preparation of dense ceramic coatings by pure vapor deposition. 3. The novel EB-PVD preparation technology based on a cold cathode electron gun expands the capability for preparing dense ceramic coatings. Compared to traditional EB-PVD equipment equipped with a hot cathode electron gun, the cold cathode electron gun allows the vacuum chamber pressure to be increased by more than 100 times. Under this vacuum condition, by appropriately reducing the substrate preheating temperature, the penetrating columnar interstices in the coating can be eliminated, achieving the preparation of dense ceramic coatings. Then, traditional columnar ceramic coatings can be prepared in situ. The interface is a chemical bond formed by pure vapor deposition, and the interlayer interface is a diffusion and chemical bond at the atomic scale. Its interfacial bonding strength is much higher than that of layered coatings prepared by spraying technology that rely on mechanical bonding. This directly translates into a longer lifespan and higher reliability of the coating under thermal cycling service conditions, meeting the needs of engineering applications. 4. Experiments showed that the coating prepared by this invention remained intact after 192 hours of acidic salt spray corrosion testing. This fully demonstrates that the dense inner layer structure of the double-layer ceramic coating effectively blocks the penetration path of corrosive media, solving the problem of "corrosion resistance deficiency" caused by the existence of penetrating columnar interstices in traditional EB-PVD coatings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the microstructure of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared in Example 1 of the present invention. Figure 2 The image shows the surface morphology of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared in Example 1 of this invention after being etched by acidic salt spray for 192 h. Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below through specific embodiments. These embodiments are intended to further illustrate the content of the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0024] Unless otherwise specified, the materials or reagents used in the following embodiments or comparative examples of the present invention are all commercially available.

[0025] Example 1 This embodiment provides a method for preparing a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating, including the following steps: Step 1: Evacuate the EB-PVD equipment equipped with a cold cathode electron gun. Specifically, start the mechanical pump, Roots pump, and diffusion pump; open the connecting valve between the main vacuum chamber and the pre-vacuum chamber; and bring the pressure in the vacuum chamber to 1×10⁻⁶. -2 Pa; Step 2: Introduce the high-voltage discharge reaction gases He and O2 into the cold cathode evaporator at a flow rate of 180 mL / min and 1.8 mL / min, respectively; introduce the high-voltage discharge reaction gases He and O2 into the cold cathode heating gun at a flow rate of 70 mL / min and 1.4 mL / min, respectively; after introducing the gases, the vacuum chamber pressure is increased to 3 × 10⁻⁶. -1 Pa; Step 3: Start the cold cathode heating gun, adjust the power of the output electron beam to 9 kW, and use the horizontal sample feeding shaft to push the part to be treated to the preheating area in the main vacuum chamber. Preheat the surface of the part to be treated for 5 minutes and preheat to 600 ℃. Step 4: Start the cold cathode evaporation gun, adjust the power of the output electron beam to 35 kW, set the rising rate of the ceramic rod to 1 mm / min, vaporize the ceramic rod, and deposit a dense ceramic coating on the surface of the preheated part to be treated. After the ceramic vapor is generated, the pressure in the vacuum chamber reaches 1 Pa, the deposition time is 10 min, and a workpiece with a dense ceramic coating is obtained. Step 5: Turn off the cold cathode evaporation gun, increase the output electron beam power of the cold cathode heating gun to 14 kW, and preheat the workpiece with dense ceramic coating obtained in step 4 for 5 min, until the temperature reaches 900 ℃. Step 6: Restart the cold cathode evaporation gun, adjust the output electron beam power to 35 kW, set the rising rate of the ceramic rod to 1 mm / min, vaporize the ceramic rod, and after the ceramic vapor is generated, the vacuum chamber pressure reaches 1 Pa, and deposit a columnar ceramic coating in situ on the workpiece with a dense ceramic coating for 10 min to prepare a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating.

[0026] The total thickness of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared in this embodiment is 120 μm, of which the thickness of the dense ceramic coating is 60 μm and the thickness of the columnar ceramic coating is 60 μm.

[0027] A schematic diagram of the microstructure of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared in this embodiment is shown below. Figure 1 As shown, it includes dense ceramic coatings and conventional columnar ceramic coatings.

[0028] To verify the corrosion resistance of the bilayer composite functional homogeneous ceramic coating provided by this invention, the coating sample prepared in Example 1 was subjected to an acidic salt spray corrosion test for 192 hours. After the test, the surface morphology of the coating is shown in the photographs below. Figure 2 As shown. From Figure 2 As can be clearly observed, after 192 hours of rigorous corrosion testing, the coating surface remained intact, without any visible corrosion spots, discoloration, blistering, or peeling. This indicates that the coating prepared by this invention effectively blocks the penetration of corrosive media with its inner dense ceramic coating, while the outer columnar ceramic coating maintains good stability, jointly ensuring the coating system's excellent long-term protective capability. This result fully demonstrates the significant effect of this invention in improving the corrosion resistance of thermal barrier coatings, and is particularly suitable for hot-end components of aero-engines operating in highly corrosive environments such as the ocean.

[0029] Example 2 This embodiment provides a method for preparing a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating, including the following steps: Step 1: Evacuate the EB-PVD equipment equipped with a cold cathode electron gun. Specifically, start the mechanical pump, Roots pump, and diffusion pump; open the connecting valve between the main vacuum chamber and the pre-vacuum chamber; and bring the pressure in the vacuum chamber to 1×10⁻⁶. -2 Pa; Step 2: Introduce the high-voltage discharge reaction gases He and O2 into the cold cathode evaporator at a flow rate of 270 mL / min and 2.7 mL / min, respectively; introduce the high-voltage discharge reaction gases He and O2 into the cold cathode heating gun at a flow rate of 80 mL / min and 1.6 mL / min, respectively; after introducing the gases, the vacuum chamber pressure is increased to 5 × 10⁻⁶. -1 Pa; Step 3: Start the cold cathode heating gun, adjust the power of the output electron beam to 11 kW, and push the part to the preheating area in the main vacuum chamber with the horizontal sample feeding shaft. Preheat the surface of the part to be treated for 15 minutes and preheat to 700℃. Step 4: Start the cold cathode evaporation gun, adjust the power of the output electron beam to 40 kW, set the rising rate of the ceramic rod to 1 mm / min, vaporize the ceramic rod, and deposit a dense ceramic coating on the surface of the preheated part to be treated. After the ceramic vapor is generated, the pressure in the vacuum chamber reaches 5 Pa, the deposition time is 15 min, and a workpiece with a dense ceramic coating is obtained. Step 5: Turn off the cold cathode evaporation gun, increase the output electron beam power of the cold cathode heating gun to 16 kW, and preheat the workpiece with dense ceramic coating obtained in step 4 for 15 min, and the preheating temperature reaches 1000 ℃. Step 6: Restart the cold cathode evaporation gun, adjust the output electron beam power to 40 kW, set the rising rate of the ceramic rod to 1 mm / min, vaporize the ceramic rod, and after the ceramic vapor is generated, the vacuum chamber pressure reaches 5 Pa, and in situ deposit a columnar ceramic coating on the workpiece with a dense ceramic coating. The deposition time is 15 min, and a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating is obtained.

[0030] The total thickness of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared in this embodiment is 180 μm, of which the thickness of the dense ceramic coating is 90 μm and the thickness of the columnar ceramic coating is 90 μm.

[0031] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating, characterized in that, The preparation steps include: Step 1: Evacuate the EB-PVD equipment equipped with a cold cathode electron gun until the pressure in the vacuum chamber is ≤1×10⁻⁶. -2 Pa; Step 2: Introduce high-voltage discharge reaction gas into the cold cathode evaporation gun and the cold cathode heating gun to make the pressure in the EB-PVD vacuum chamber 3×10⁻⁶. -1 ~5×10 -1 Pa; Step 3: Start the cold cathode heating gun to preheat the surface of the part to be treated to 600~700 ℃; Step 4: Start the cold cathode evaporation gun to vaporize the ceramic rod and deposit a dense ceramic coating on the surface of the preheated part to be treated, thereby obtaining a workpiece with a dense ceramic coating. Step 5: Turn off the cold cathode evaporation gun, increase the power of the cold cathode heating gun, and preheat the workpiece with the dense ceramic coating to 900~1000 ℃; Step 6: Restart the cold cathode evaporation gun to deposit a columnar ceramic coating in situ on the workpiece with a dense ceramic coating, thereby obtaining a cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating.

2. The preparation method according to claim 1, characterized in that, In step two, the high-voltage discharge reaction gases introduced into the cold cathode evaporation gun are He and O2, with a He flow rate of 180~270 mL / min and an O2 flow rate of 1.8~2.7 mL / min; and / or, The high-voltage discharge reaction gases introduced into the cold cathode heating gun are He gas and O2 gas, with a He flow rate of 70~80 mL / min and an O2 flow rate of 1.4~1.6 mL / min.

3. The preparation method according to claim 1, characterized in that, In step three, the power of the electron beam output by the cold cathode heating gun is 9~11 kW, and the preheating time is controlled to be 5~15 min.

4. The preparation method according to claim 1, characterized in that, In step four, the power of the electron beam output by the cold cathode evaporation gun is 35~40 kW, and the deposition time is 10~15 min; and / or, When depositing a dense ceramic coating, the pressure in the vacuum chamber is 1~5 Pa.

5. The preparation method according to claim 1, characterized in that, In step five, the power of the electron beam output by the cold cathode heating gun is increased to 14~16 kW, and the preheating time is controlled to be 5~15 min.

6. The preparation method according to claim 1, characterized in that, In step six, the power of the electron beam output by the cold cathode evaporation gun is 35~40 kW, and the deposition time is 10~15 min; and / or, When depositing columnar ceramic coatings, the pressure in the vacuum chamber is 1~5 Pa.

7. A cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating prepared by any one of claims 1-6, characterized in that, It includes an inner layer and an outer layer, wherein the inner layer is a dense ceramic coating that contacts the surface of the part to be treated, and the outer layer is a columnar ceramic coating deposited on the dense ceramic coating.

8. The coating according to claim 7, characterized in that, The total thickness of the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating is 120~180 μm, wherein the thickness of the dense ceramic coating is 60~90 μm, and the thickness of the columnar ceramic coating is 60~90 μm.

9. A component having the cold cathode EB-PVD bilayer composite functional homogeneous ceramic coating as described in claim 7 or 8.

10. The application of the component according to claim 9 in an aircraft engine.

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