A CVD device and method for preparing inner hole surface coating of parts

Abstract

The present invention relates to a CVD device and method for preparing a coating on the inner hole surface of a component. The CVD device is an existing device that adds a controller and a flow control valve located at the top outlet of a deposition reaction chamber. The controller controls the flow control valve to achieve pulsed alternation of the reaction gas pressure and flow during chemical vapor deposition, thereby achieving uniformity control of the airflow on the surface of the confined space cavity, and preparing a continuous and uniform CVD coating on the inner cavity surface of a component with an elongated hole. By utilizing the pulsed alternating transport of the reaction airflow to ensure the uniformity of the overall coating deposition / diffusion growth process on the inner cavity surface of the component, this method effectively solves the problem of uneven coating deposition on the inner cavity surface of an elongated hole caused by traditional chemical deposition.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing coatings by chemical vapor deposition (CVD), and specifically relates to a CVD device and preparation method for preparing coatings on the inner hole surfaces of components. CVD coatings can be prepared on the inner surfaces of components with elongated holes. Background Art

[0002] Chemical vapor deposition (CVD) technology is a new material surface enhancement technology developed in recent decades. It utilizes gaseous precursors at very high temperatures to decompose certain components of the gaseous precursor through atomic and molecular chemical reactions, resulting in the formation of a solid thin film on a substrate. It is primarily used to prepare binary or multinary intermetallic compound coatings (oxides, nitrides, carbides, aluminides, etc.) from groups III-V, II-IV, and IV-VI, thereby imparting specific properties to the workpiece surface. CVD coatings offer high purity, good uniformity, excellent density, low residual stress, and strong adhesion to the substrate. They can produce high-purity, fully crystallized polycrystalline or single-crystal films, and are not only used in the preparation of ferroelectric, insulating, magnetic, and optoelectronic thin-film materials for large-scale integrated circuits, but are also indispensable for high-temperature protective coatings.

[0003] Compared with physical and chemical vapor deposition (PVD) technology, CVD reactive coating has better diffraction and good step coverage, and can be used for coating the surfaces of different components or curved surfaces of workpieces. However, for parts with complex shapes, deep holes or slender holes, the precursor in the traditional CVD deposition reaction process is easily affected by the spatial size and flow channel structure, making it difficult to achieve uniform distribution, resulting in uneven chemical vapor deposition film formation. Taking the hollow blades of aircraft engines and gas turbines as an example, due to the limited space inside the slender holes of the hollow blades, the precursor locally forms turbulence, eddies and other surface adsorption behaviors in the confined space of the slender inner hole, resulting in uneven concentration distribution of the precursor on the inner hole surface, and then leading to uneven diffusion growth of the coating. The uneven coating will have a fatal impact on its thermal protection effect. Individual thin areas or leaks will cause premature failure of the thermal protection layer due to the short board effect, which will restrict the overall service performance of the CVD thermal protection coating. Therefore, there is an urgent need to improve traditional CVD technology, enhance the uniformity of CVD technology coating on the inner holes of components, achieve the overall protective effect of the coating on key components, and thereby improve the overall service performance of the equipment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a CVD device and method for preparing a coating on the inner hole surface of a component. The preparation method is used to prepare a continuous and uniform CVD coating on the inner cavity surface of a slender hole component.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] The present invention provides a CVD device for preparing a coating on the inner hole surface of a component, comprising a raw gas supply system, a deposition reaction chamber, a vacuum pump and an exhaust gas treatment system connected in sequence;

[0007] The raw gas supply system is connected to the bottom inlet of the deposition reaction chamber for supplying the raw gas required for the reaction. The vacuum pump is connected to the top outlet of the deposition reaction chamber for evacuating the chamber and controlling the reaction pressure.

[0008] The exhaust gas treatment system is connected to the outlet of the vacuum pump and is used to collect and treat the exhaust gas;

[0009] The deposition reaction chamber is provided with a heating system and an air distribution plate for placing parts and distributing airflow;

[0010] It is characterized in that it also includes a controller and a flow regulating valve, the flow regulating valve is arranged between the exhaust gas treatment system and the top outlet of the deposition reaction chamber, and the controller controls the opening of the flow regulating valve to generate an alternating reaction pressure field in the deposition reaction chamber.

[0011] Furthermore, the raw gas supply system includes a plurality of gas supply pipes and a gas mixing tank connected to the plurality of gas supply pipes, and the outlet of the gas mixing tank is connected to the bottom inlet of the deposition reaction chamber through an air inlet pipe.

[0012] Furthermore, one end of the multiple gas supply pipes is connected to a gas mixing tank, and the other end is connected to a corresponding gas cylinder; a plurality of parallel external generators are provided between the outlet of the gas mixing tank and the bottom inlet of the deposition reaction chamber.

[0013] Furthermore, the air distribution plate is provided with air distribution holes distributed in a circular array.

[0014] Furthermore, the controller is a PLC controller with a built-in PID regulator.

[0015] The present invention adopts a PLC controller containing a PID regulator to control the flow control valve, which is used to control the continuous transportation of the reaction gas in a pulse alternating mode on the surface of the confined space during the chemical vapor deposition process. The new pulse alternating CVD technology is used to achieve the uniformity control of the airflow on the surface of the inner cavity of the confined space, thereby realizing the preparation of a continuous and uniform CVD coating on the inner surface of the confined space.

[0016] The present invention also protects a method for preparing a coating on the surface of an inner hole of a component, using the above-mentioned CVD device, comprising the following steps:

[0017] Step 1. Place the sample: Fix the cleaned part to be deposited above the air distribution plate in the deposition reaction chamber with a fixture, and adjust the position of the part to be coated so that the inner hole flow channel is directly above the air distribution hole;

[0018] Step 2: vacuuming: vacuuming the deposition reaction chamber by a vacuum pump;

[0019] Step 3: Introduce gas and adjust pressure: Introduce process gas into the deposition reaction chamber through the raw gas supply system. The process gas flow is controlled by a gas flow meter to ensure that the inlet of the deposition reaction chamber is maintained at a high pressure state. At the same time, the vacuum pump is turned on to evacuate the gas. The flow control valve opening is controlled by a controller to adjust the deposition pressure to the pressure pulse wave required by the deposition process, so that the process gas forms a rapid pressure differential flow in the inner hole of the component.

[0020] Step 4, Deposition: Set the heating temperature through the heating system to heat the parts and the deposition chamber. When the temperature reaches the set temperature, start deposition. After the deposition is completed, turn off the process gas in sequence, stop the heating system, evacuate, and wait for the deposition reaction chamber to cool to room temperature before taking out the deposited parts.

[0021] Furthermore, in step 2 and step 4, the vacuum is drawn to a pressure below 100 Pa.

[0022] Furthermore, in step 3, the deposition pressure is controlled within a range of 3-50 KPa, and the pressure variation range is plus or minus 10-50%.

[0023] Furthermore, in step 3, the waveform of the pressure pulse wave is any one of a rectangular wave, a sawtooth wave, a triangle wave, a spike wave, a step wave, and a deformed wave of a rectangular wave.

[0024] Furthermore, in step 3, the frequency of the pressure pulse wave is 1-30 times / min.

[0025] Furthermore, the waveform of the pressure pulse wave is a deformed wave of a rectangular wave, specifically, a smooth transition is adopted at the rising vertex and falling corner of the rectangular wave, such as Figure 5 As shown in A.

[0026] The principle of the present invention is to realize the pulse alternating mode transport of the precursor by adopting a flow control valve of a PLC controller containing a PID regulator. The valve opening and closing size can be adjusted by PLC to control the working pressure in the deposition reaction chamber, and a pulse alternating pressure (periodically changing pressure) is applied. The disturbance degree of the reactor is increased by pressure changes of a certain frequency, so that the precursor (reaction gas) forms a rapid pressure difference flow in the inner hole space of the component, thereby preventing the reaction gas from having poor contact with the inner hole or too slow flow rate, local stable vortex, etc. under constant pressure difference conditions, which leads to uneven deposition reaction, thereby obtaining continuous and uniform airflow transport on the inner cavity surface of the component, and realizing the preparation of continuous and uniform CVD coating on the inner surface of narrow and elongated holes.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention adopts a precursor pulse alternating process during the CVD deposition process to solve the problem of adaptability of the reaction gas in the confined space of the inner cavity of the slender hole parts, realizes the rapid high-concentration enrichment and uniform adsorption of the precursor on the inner hole surface of the part, ensures the uniformity of the coating deposition / diffusion growth process on the entire inner cavity surface of the part, and supports solving the problem of adaptability of the slender inner hole confined space of oversized parts.

[0029] 2. The CVD coating obtained according to the preparation method of the present invention has uniform thickness and high deposition rate, which can solve the problem of uneven film deposition in slender holes caused by traditional chemical deposition, and prevent the occurrence of the barrel effect caused by the uneven film generated by the traditional deposition method, which causes the components to fail prematurely in a complex service environment. This invention is not only used for aluminide coatings in the inner cavity of hollow blades, but is also applicable to various coatings prepared by CVD method on different components. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the CVD device for preparing the inner hole surface coating of the component according to Example 1 of the present invention.

[0031] Figure 2 This is a cross-sectional morphology of the coating prepared on nickel tubes with different pore sizes using the CVD pulse alternating process in Example 2, wherein Figure 2 (a) and Figure 2 (b) are cross-sectional morphologies of a 1.6 mm diameter nickel tube at 1 / 3 and 2 / 3 cross sections, respectively. Figure 2 (c) and Figure 2 (d) The cross-sectional morphology of the nickel tube with a diameter of 2.6 mm at the 1 / 3 and 2 / 3 cross sections respectively; Figure 2 (e) and Figure 2 (f) Longitudinal cross-sections of a 2.6 mm diameter nickel tube at different positions.

[0032] Figure 3 This is a cross-sectional morphology diagram of the coating prepared on the inner surface of a hollow blade using a CVD pulse alternating process in Example 3, wherein Figure 3 (a) is the inner hole surface coating, Figure 3 Middle (b) is the outer pore surface coating.

[0033] Figure 4 This is a cross-sectional morphology diagram of the coating prepared on the inner surface of a hollow blade using CVD constant pressure and constant flow gas transport in comparative example 1. Figure 4 (a) is the outer surface diagram of the 1 / 3 cross section, Figure 4 (b) is the outer surface diagram of the 2 / 3 cross section, Figure 4 (c) is the inner surface diagram of the 1 / 3 cross section, Figure 4 (d) is the inner surface diagram of the 2 / 3 cross section.

[0034] Figure 5 It is a waveform diagram of the pressure pulse wave in the method for preparing the inner hole surface coating of the component of the present invention. Figure 5 A is a schematic diagram of a deformed rectangular wave. Figure 5 B is a schematic diagram of a rectangular wave. Figure 5 C in the middle is a triangle wave diagram.

[0035] Attachment Figure 1 Label: 1-gas mixing tank, 2-external generator I, 3-external generator II, 4-deposition reaction chamber, 5-gas distribution plate, 6-hollow blade, 7-flow regulating valve, 8-controller, 9-vacuum pump, 10-exhaust gas treatment system, 11-bottom inlet, 12-top outlet, 13-gas flow meter. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following embodiments of the present invention are further described in detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0037] Example 1: Figure 1 As shown, the present invention provides a CVD device for preparing a surface coating on the inner hole of a component, comprising a raw gas supply system, a deposition reaction chamber 4, a vacuum pump 9, an exhaust gas treatment system 10, a controller 8 and a flow control valve 7 connected in sequence;

[0038] The raw gas supply system is connected to the bottom inlet 11 of the deposition reaction chamber 4 for supplying the raw gas required for the reaction. The vacuum pump 9 is connected to the top outlet 12 of the deposition reaction chamber 4 for evacuating the vacuum and controlling the reaction pressure.

[0039] The exhaust gas treatment system 10 is connected to the outlet of the vacuum pump 9 and is used to collect and treat the exhaust gas;

[0040] The deposition reaction chamber 4 is provided with a heating system (not shown in the figure, it is a conventional structure) and an air distribution plate 5 for placing parts and distributing air flow;

[0041] The flow regulating valve 7 is provided between the exhaust gas treatment system and the top outlet 12 of the deposition reaction chamber 4 . The controller generates an alternating reaction pressure field in the deposition reaction chamber by controlling the opening of the flow regulating valve.

[0042] As a preferred embodiment, the raw gas supply system includes multiple gas supply pipes and a gas mixing tank 1 connected to the multiple gas supply pipes, and the outlet of the gas mixing tank 1 is connected to the bottom inlet 11 of the deposition reaction chamber through an air inlet pipe.

[0043] As a preferred embodiment, one end of the multiple gas supply pipes is connected to the gas mixing tank 1, and the other end is connected to the corresponding gas cylinder through the gas flow meter 13 (each supply pipe is connected to a gas cylinder, such as an HCl gas cylinder, an H2 gas cylinder, etc.); a plurality of parallel external generators are provided between the outlet of the gas mixing tank 1 and the bottom inlet 11 of the deposition reaction chamber 4, which in this embodiment may be external generator I 2 and external generator II 3; the raw materials required for vapor deposition modification, such as polydimethylsiloxane, etc., can be placed in the external generator. When the process gas passes through the external generator, the polydimethylsiloxane is vaporized and carried into the deposition reaction chamber to participate in the deposition reaction.

[0044] As a preferred embodiment, each gas cylinder outlet is provided with a gas flow meter 13 for adjusting the supply flow of the process gas.

[0045] As a preferred embodiment, the gas distribution plate 5 is provided with gas distribution holes distributed in a circular array, which can improve the uniformity of gas distribution.

[0046] As a preferred embodiment, the controller 8 is a PLC controller with a built-in PID regulator, which facilitates the design of pulse waveforms to improve deposition quality.

[0047] It should be noted that the present invention does not make any improvements to the waste gas treatment system, and the waste gas treatment system commonly used in the CVD process can be used.

[0048] Example 2: This example takes nickel tube inner hole deposition as an example to provide a method for preparing a surface coating on the inner hole of a component, using the equipment in Example 1, specifically as follows:

[0049] The cleaning method of the parts to be coated in the embodiment of the present invention is as follows: the parts are ultrasonically cleaned in deionized water for 10 minutes, then ultrasonically cleaned in alcohol for 15 minutes, then cleaned in a mixture of HF:H2O=1:80 (volume ratio) for 1 minute, and finally rinsed with deionized water to obtain a clean substrate.

[0050] In this embodiment, nickel tubes with different pore diameters (length 50 mm, diameter 1.6 mm and diameter 2.6 mm) were used as substrates, and aluminide coatings were prepared on the inner flow channels of the nickel tubes with different pore diameters using a CVD pulse alternating deposition process.

[0051] To prepare a uniform aluminide coating on the inner cavity of the nickel tube, the following steps are taken:

[0052] 1) Lofting: Secure the cleaned nickel tube to the gas distribution plate with a fixture. Adjust the nickel tube to be coated and the fixture so that the inner channel is directly above the gas distribution hole. Place the aluminum pellets in the external generator I and set the temperature to 350°C.

[0053] 2) Vacuuming: evacuating the chemical vapor deposition chamber to below 100 Pa.

[0054] 3) Gas pressure adjustment: Process gas (15% AlCl3 gas + 15% HCl gas + 50% Ar + 30% H2) is introduced, and the process gas flow rate is controlled by a gas flow meter to ensure that the reaction gas A inlet of the deposition reaction chamber is maintained at a high pressure state. The flow rate of AlCl3 gas is 1slm, the flow rate of HCl gas is 1slm, the flow rate of Ar gas is 5slm, and the flow rate of H2 gas is 3slm. At the same time, the vacuum pump (9) is turned on, and the PID regulator of the gas B outlet of the deposition reaction chamber is set by the PLC controller of the console. The pulse waveform of the deposition pressure is controlled to be trapezoidal. The deposition pressure alternates between 10KPa and 50KPa. The pressure alternates 10 cycles per minute, so that the reaction gas forms a rapid pressure difference flow in the inner pore space, and is stabilized for 10 minutes to obtain continuous and uniform airflow transport.

[0055] 4) Deposition: Set the heating program through the temperature control system, heat the deposition reaction chamber to the set temperature of 900°C, keep it warm for 30 minutes, and heat the substrate and deposition chamber at a heating rate not exceeding 10°C / min. After the temperature reaches the set temperature of 900°C, set the deposition time to 60 minutes and start deposition.

[0056] 5) Deposition is completed: first turn off HCl and AlCl3, then turn off H2 and Ar, stop the heating process, evacuate the deposition reaction chamber to below 100 Pa, and wait for the deposition reaction chamber to cool to room temperature before sampling. A uniform aluminide coating is prepared on the inner cavity surface of different diameter tubes. The cross-sectional morphology of the coating is as follows: Figure 2 As shown: Figure 2 (a) and (b) are cross-sectional morphologies of a 1.6 mm diameter nickel tube at 1 / 3 and 2 / 3 cross sections, respectively. Figure 2 (c) and (d) are the cross-sectional morphologies of a 2.6 mm diameter nickel tube at 1 / 3 and 2 / 3 of the cross section, respectively. Figure 2(e) and (f) are longitudinal cross-sectional views of a 2.6mm diameter nickel tube at different locations. As can be seen from the figures above, the coating on the inner surface of the nickel tubes with different pore diameters is uniform and of consistent thickness, with no missing coating.

[0057] Example 3:

[0058] This embodiment uses an aircraft engine hollow blade as a substrate. The aircraft hollow blade has an inner cavity flow channel, and a CVD pulse alternating deposition process is used to prepare an aluminide coating on the inner cavity flow channel of the hollow blade.

[0059] To achieve a uniform aluminide coating on the inner hole of a hollow blade, the following steps are taken:

[0060] 1) Lofting: Secure the cleaned hollow aviation blade to the air distribution plate with a fixture. Adjust the position of the hollow blade to be coated and the fixture so that the inner cavity flow channel is directly above the air distribution hole. Place aluminum pellets in the external generator I and set the temperature to 350°C.

[0061] 2) Vacuuming: evacuating the chemical vapor deposition chamber to below 100 Pa.

[0062] 3) Introducing gas pressure adjustment: Introducing process gas (10% AlCl3 gas + 10% HCl gas + 50% Ar + 30% H2), controlling the process gas flow rate through a gas flow meter to ensure that the inlet of the reaction gas A of the deposition reaction chamber is maintained at a high pressure state, the flow rate of AlCl3 gas is 1slm, the flow rate of HCl gas is 1slm, the flow rate of Ar gas is 5slm, and the flow rate of H2 gas is 3slm, and at the same time, the vacuum pump (9) is turned on, and the PID regulator of the gas B outlet of the deposition reaction chamber is set through the PLC controller of the console, and the pulse waveform of the deposition pressure is controlled to change to a triangular variation, and the deposition pressure alternates between 15KPa and 45KPa, and the pressure alternates 5 cycles per minute, so that the reaction gas forms a rapid pressure difference flow in the inner pore space, and is stabilized for 10 minutes to obtain continuous and uniform airflow transport.

[0063] 4) Deposition: Set the heating program through the temperature control system, heat the deposition reaction chamber to the set temperature of 1000°C, keep it warm for 30 minutes, and heat the substrate and deposition chamber at a heating rate not exceeding 10°C / min. After the temperature reaches the set temperature of 1000°C, set the deposition time to 60 minutes and start deposition.

[0064] 5) End of deposition: First turn off HCl and AlCl3, then turn off H2 and Ar, stop the heating process, evacuate the deposition reaction chamber to below 100 Pa, and wait for the deposition reaction chamber to cool to room temperature before sampling. A uniform aluminide coating was prepared in the inner cavity of an aviation hollow blade. The cross-sectional morphology of the coating is as follows: Figure 3As shown: After cutting and inlaying the 1 / 2 of the inner hole of the hollow blade, the cross section is characterized. It can be seen that the inner hole surface and outer surface of the hollow blade are evenly coated with consistent coating thickness.

[0065] Comparative Example 1:

[0066] This embodiment uses a hollow blade as a substrate and adopts a precursor constant pressure and constant current CVD process to prepare an aluminide coating in the inner cavity of the hollow blade. This is in contrast to the embodiment 2 which adopts a CVD pulse alternating deposition process to deposit an aluminide coating in the inner cavity of the hollow blade. The constant pressure and constant current CVD preparation process is as follows:

[0067] 1) Lofting: Secure the cleaned hollow blade to the air distribution plate with a fixture. Adjust the position of the hollow blade to be coated and the fixture so that the inner cavity flow channel is directly above the air distribution hole. Place aluminum pellets in the external generator I and set the temperature to 350°C.

[0068] 2) Vacuuming: evacuating the chemical vapor deposition chamber to below 100 Pa.

[0069] 3) According to the preparation process set in Example 2, the gas pressure was adjusted, and the PID regulator of the gas B outlet of the deposition reaction chamber was set by the PLC controller of the console to control the deposition pressure to be constant at 5 kPa. The precursor was transported at a constant pressure and constant flow in the CVD deposition chamber for 30 minutes.

[0070] 4) Set the temperature deposition process flow according to Implementation Example 3 and start deposition.

[0071] 5) After the deposition is completed, samples are taken to characterize the coating at different locations within the hollow blade cavity, such as Figure 4 As shown in , by characterizing the coating sections at different locations (cross sections at 1 / 3 and 2 / 3) of the hollow blade cavity, it was found that the coating can be observed on the outer surface of the hollow blade at different locations, and the thickness is uneven, as shown in Figure 4 As shown in (a) and (b), no coating was observed on the inner hole surface of the hollow blade at different positions, such as Figure 4 By comparing with Examples 1 and 2, it is shown that the CVD pulse alternating deposition process of the present invention has a significant effect on uniform coating of the inner hole surface of the component.

[0072] The above embodiments are intended to illustrate the present invention only and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications, or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and should be encompassed by the scope of the claims of the present invention.

Claims

1. A method for preparing a coating on the inner surface of a component, using a CVD apparatus comprising a feed gas supply system, a deposition reaction chamber, a vacuum pump, an exhaust gas treatment system, a controller, and a flow control valve connected in sequence; The raw gas supply system is connected to the bottom inlet of the deposition reaction chamber for supplying the raw gas required for the reaction. The vacuum pump is connected to the top outlet of the deposition reaction chamber for evacuating the chamber and controlling the reaction pressure. The exhaust gas treatment system is connected to the outlet of the vacuum pump and is used to collect and treat the exhaust gas; The deposition reaction chamber is provided with a heating system and an air distribution plate for placing parts and distributing airflow; The flow regulating valve is arranged between the exhaust gas treatment system and the top outlet of the deposition reaction chamber, and the controller generates an alternating reaction pressure field in the deposition reaction chamber by controlling the opening of the flow regulating valve; the invention is characterized in that: The method comprises the following steps: Step 1. Place the sample: Fix the cleaned part to be deposited above the air distribution plate in the deposition reaction chamber with a fixture, and adjust the position of the part to be coated so that the inner hole flow channel is directly above the air distribution hole; Step 2: vacuuming: vacuuming the deposition reaction chamber by a vacuum pump; Step 3: Introduce gas and adjust pressure: Introduce process gas into the deposition reaction chamber through the raw gas supply system. The process gas flow is controlled by a gas flow meter to ensure that the inlet of the deposition reaction chamber is maintained at a high pressure state. At the same time, the vacuum pump is turned on to evacuate the gas. The flow control valve opening is controlled by a controller to adjust the deposition pressure to the pressure pulse wave required by the deposition process, so that the process gas forms a rapid pressure differential flow in the inner hole of the component. Step 4, Deposition: The heating system sets the heating temperature to heat the components and the deposition chamber. When the temperature reaches the set temperature, deposition begins. After deposition is completed, the process gases are turned off, the heating system is stopped, and the chamber is evacuated. The deposited components are removed after the deposition chamber cools to room temperature. In step 3, the deposition pressure is controlled in the range of 3-50 KPa, and the pressure variation range is plus or minus 10-50%.

2. The method for preparing a coating on the inner hole surface of a component according to claim 1, characterized in that: The raw material gas supply system includes a plurality of gas supply pipes and a gas mixing tank connected to the plurality of gas supply pipes. The outlet of the gas mixing tank is connected to the bottom inlet of the deposition reaction chamber through an air inlet pipe.

3. The method for preparing a coating on the inner hole surface of a component according to claim 2, characterized in that: One end of the multiple gas supply pipes is connected to a gas mixing tank, and the other end is connected to a corresponding gas cylinder; a plurality of parallel external generators are provided between the outlet of the gas mixing tank and the bottom inlet of the deposition reaction chamber.

4. The method for preparing a coating on the inner hole surface of a component according to claim 1, characterized in that: The air distribution plate is provided with air distribution holes distributed in a circular array.

5. The method for preparing a coating on the inner hole surface of a component according to claim 1, characterized in that: The controller is a PLC controller with a built-in PID regulator.

6. The method for preparing a coating on the inner hole surface of a component according to claim 1, characterized in that: In steps 2 and 4, the vacuum is drawn to a pressure below 100 Pa.

7. The method for preparing a coating on the inner hole surface of a component according to claim 1, characterized in that: In step 3, the waveform of the pressure pulse wave is a pulse wave, specifically any one of a rectangular wave, a sawtooth wave, a triangle wave, a spike wave, a step wave and a deformed wave of a rectangular wave, and the deformed wave of the rectangular wave is obtained by smooth transition at the rising vertex and the falling corner point of the rectangular wave.

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