A device and method for testing the hydrogen barrier performance of the surface coating of a closed-end special-shaped part

Abstract

The present invention relates to a device for testing the hydrogen barrier performance of the surface coating of a closed-port special-shaped part and a method for using the device. The device includes a special-shaped part inner tube, a special-shaped part outer tube, a temperature control system, and a deuterium current signal monitoring module. The special-shaped part outer tube is arranged on the periphery of the special-shaped part inner tube, and the inner cavity of the special-shaped part inner tube is the pipe inner chamber. The special-shaped part inner tube and the special-shaped part outer tube form a pipe outer chamber. The upper opening of the special-shaped part outer tube and the outer wall of the special-shaped part inner tube are connected and sealed by an annular cylinder to form a closed space. The inner wall of the special-shaped part inner tube or the inner wall and outer wall of the special-shaped part inner tube are coated with a hydrogen barrier coating. The pipe outer chamber is connected to the deuterium current signal monitoring module via an outer chamber tooling module. The device of the present invention has a reasonable design and a simple structure. The surface coating of the device is convenient and efficient to prepare. It can accurately evaluate the density, effective coating, and hydrogen barrier performance of the surface coating of the closed-port special-shaped part. It has high practical value, low cost, and is easy to use.

Description

Technical Field

[0001] The invention belongs to the field of hydrogen permeability testing of protective coatings, and in particular relates to a device for testing the hydrogen resistance performance of a ceramic coating on the surface of a closed-port special-shaped part and a method for using the device. Background Art

[0002] Hydrogen and its isotopes, such as tritium and deuterium, easily penetrate into metallic structural materials through atomic diffusion, degrading their performance, shortening their service life, and compromising their safety. Hydrogen-related components such as fusion reactor blanket modules, solar thermal power generation tubes, oil pump barrels, and oil pipelines all face serious hydrogen and isotope permeation problems. Currently, the most effective solution to hydrogen permeation is to deposit one or more ceramic films with high hydrogen permeation resistance on the surface of metallic structural materials. However, most metallic structural materials or components are shaped like tubular components, making the preparation of surface coatings on these shaped components much more challenging than for flat substrates. The hydrogen resistance of coatings on shaped components is limited by several factors, including coating integrity, the presence of cracks or holes at corners, and the potential for damage to the coating during welding of external pipes. Consequently, a test device for the hydrogen resistance of coatings on closed-end shaped components has yet to be developed and implemented, and literature reporting on the hydrogen resistance of coatings on shaped components is extremely scarce. However, the engineering application of structural materials requires precise testing of the hydrogen barrier properties of the surface coating of special-shaped parts, and it is crucial to ascertain the hydrogen permeability of the surface coating of special-shaped parts under high temperature conditions.

[0003] At present, there are the following patent documents in the field of hydrogen permeability testing. CN114813452A discloses a hydrogen permeability test device and method for non-metallic pipes, CN112763381A discloses a hydrogen permeability test device and test method, and CN113252529A discloses a high-temperature gas-driven permeation test system and test method for metal pipes. The invention patent of CN114813452A is a hydrogen transportation pipeline made of non-metallic materials (such as high-density polyethylene in the implementation case) used in the field of hydrogen transportation. There are problems such as the inability to test hydrogen permeability at high temperatures; the invention patent of CN112763381A is also used for oil pipelines in traditional low-temperature environments. It tests by detecting changes in the negative pressure of the permeated hydrogen, and its measurement accuracy of the hydrogen permeability of the hydrogen barrier coating at high temperatures cannot meet the requirements. Although the invention patent CN113252529A discloses a high-temperature gas-driven permeation test system, it tests the hydrogen permeation changes of metal pipes and cannot comprehensively and accurately evaluate the density and coverage integrity of the pipe surface coating, nor can it test the hydrogen resistance performance of the surface coating of special-shaped parts with one end closed.

[0004] In summary, there is currently a lack of a testing device and method for measuring the hydrogen barrier performance of the surface coating of a special-shaped component with a closed port at high temperature with high precision. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a device and method for testing the hydrogen resistance performance of the surface coating of a closed-port special-shaped part; the device can test the hydrogen permeability of the closed-port special-shaped part substrate and the substrate coated with different ceramic coatings with high precision, and further calculate the hydrogen permeation reduction factor (PRF) of the different coatings on the surface of the closed-port special-shaped part, which can accurately evaluate the hydrogen permeation resistance performance of the surface coating of the special-shaped part; the device design is reasonable and simple, and the test operation process is clear, safe and convenient.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions.

[0007] A device for testing the hydrogen barrier performance of the surface coating of a closed-port special-shaped part, comprising a special-shaped part inner tube, a special-shaped part outer tube, a temperature control system, and a deuterium current signal monitoring module; the special-shaped part inner tube is a closed cavity with one end open, the special-shaped part outer tube is arranged on the periphery of the special-shaped part inner tube, the inner cavity of the special-shaped part inner tube is a pipe inner chamber, and a pipe outer chamber is formed between the special-shaped part inner tube and the special-shaped part outer tube, and the inner wall of the special-shaped part inner tube or the inner wall and outer wall of the special-shaped part inner tube are coated with a hydrogen barrier coating; The upper opening of the inner tube of the special-shaped part is connected to the gas input pipeline through the air inlet end tooling module, which is used to connect deuterium gas to the inner chamber of the pipe; the temperature control system is used to heat the entire component consisting of the inner chamber of the pipe and the outer chamber of the pipe; the outer chamber of the pipe is connected to the deuterium current signal monitoring module through the outer chamber tooling module, and the deuterium current signal monitoring module is used to collect deuterium atoms that penetrate through the hydrogen barrier coating and the inner tube of the special-shaped part and display them as current signals in the deuterium current signal monitoring module.

[0008] Furthermore, the upper opening of the outer tube of the special-shaped part and the outer wall of the inner tube of the special-shaped part are connected and sealed by an inner tube attachment ring.

[0009] Furthermore, the inner pipe attachment ring is an annular cylinder formed by turning at a position 10-20 mm away from the top outlet of the special-shaped part.

[0010] Furthermore, the inner pipe attachment ring is an annular cylinder formed by turning at a position 10-20 mm away from the top outlet of the special-shaped part.

[0011] Furthermore, the temperature control system is a flip-top heating furnace, the temperature is controlled by a program, the inner tube and outer tube of the special-shaped part are both in the furnace of the heating furnace, and the gas input pipeline and the deuterium current signal monitoring module are respectively located at the front and rear ends of the heating furnace.

[0012] A method for using the device for testing the hydrogen barrier performance of the surface coating of a closed-end special-shaped part as described in any one of the above items, the method comprising the following steps:

[0013] S1. After coating the inner and outer walls and bottom of the inner tube of the special-shaped part, weld the outer tube of the special-shaped part to form the outer cavity of the pipe fitting, and perform a helium leak test to check its air tightness;

[0014] S2. Connecting the test piece consisting of the inner tube of the special-shaped part and the outer tube of the special-shaped part to the gas input pipeline through the air inlet end tooling module, and connecting the outer chamber of the tube to the deuterium current signal monitoring module through the outer chamber tooling module;

[0015] S3. Turn on the upstream and downstream forepumps to extract the gas in the chamber. After the pressure in the chamber is lower than 10 Pa, turn on the molecular pump to accelerate the formation of a high vacuum environment in the chamber.

[0016] S4. After the gas pressure in the chamber reaches 1×10-5Pa or above, the temperature control system is turned on to heat the inner and outer chambers. The predetermined temperature is 300-700°C, and the heating rate is 5-15°C / min.

[0017] S5. When the pressure in the preset chamber reaches the required value, the deuterium current signal monitoring module 10 connected to the outer chamber of the pipe is turned on to collect the permeated deuterium ion current signal value of the downstream outer chamber;

[0018] S6. Close the upstream molecular pump and forepump system valves, open the deuterium gas valve, input deuterium gas into the inner chamber of the pipe through the gas input pipeline, control the deuterium gas input pressure value through the needle valve on the gas line, set the deuterium gas pressure value to 20-100kPa and then close the deuterium gas flow input. Combined with the hydrogen pressure of the pressure sensor, the steady-state current signal value output by the deuterium current signal monitoring module, and the temperature data of the deuterium current signal monitoring module, the permeability of the surface coating of the closed-port special-shaped part at a specified temperature is calculated.

[0019] The beneficial effects of the present invention are:

[0020] 1. Compared to existing solutions, the present invention aims to provide, for the first time, a device and method for testing the hydrogen barrier properties of surface coatings on closed-end shaped parts under high-temperature conditions with high precision. The inner tube of the closed-end shaped part is straight and smooth, with no protrusions or depressions at the connection with the bottom port, which facilitates smooth coating of the coating on the inner tube wall and the inner wall of the bottom end. Because the entire inner tube wall and the inner wall of the bottom end are exposed to the deuterium gas in the chamber during testing, the hydrogen barrier test results of uncoated stainless steel closed-end shaped parts and coated stainless steel closed-end shaped parts after deuterium charging can accurately reflect whether the coating is effectively applied to the surface and corners of the shaped part material, thereby determining the coating's hydrogen permeation resistance.

[0021] 2. The present invention provides a device for testing the hydrogen resistance performance of the surface coating of a closed-end special-shaped part. The device has a reasonable design and ingenious structure. An annular "ear" structure is designed at the outlet of the closed-end special-shaped part. The device can weld an outer pipe to the "ear" structure to construct an outer chamber to detect the deuterium ion current signal that penetrates through the inner pipe and the coating. It can also effectively avoid the adverse effects of high-temperature welding of the outer pipe on the prepared coating. Moreover, this "ear" structure does not affect the successful preparation of the coating by commonly used processes such as immersion and pulling, sol-gel or electrodeposition.

[0022] 3. The hydrogen barrier performance testing device and usage method of the surface coating of closed-port special-shaped parts provided by the present invention have clear procedures and convenient operation, and are highly universal for testing different types of coatings on the surface of closed-port special-shaped parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic structural diagram of a device for testing the hydrogen barrier performance of a surface coating on a closed-end special-shaped part according to Example 1 of the present invention;

[0024] Figure 2 This is a light microscope image of the coating effect of the inner pipe fitting of the closed-end special-shaped part of Example 1 of the present invention;

[0025] Figure 3 1 is a deuterium ion current test result and a deuterium permeability comparison chart of Example 1 of the present invention;

[0026] Figure 4 This is a light microscope image of the coating effect of the inner pipe coating of the closed-end special-shaped part of Example 2 of the present invention.

[0027] In the figure: 1-inner tube of special-shaped part; 2-outer tube of special-shaped part; 3-attachment ring of inner tube; 4-inner chamber of tube; 5-outer chamber of tube; 6-hydrogen barrier coating; 7-inlet end tooling module; 8-outer chamber tooling module; 9-temperature control system; 10-deuterium current signal monitoring module. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0029] Example 1

[0030] This embodiment provides a device for testing the hydrogen permeability of a closed-end special-shaped part coated with an AlPO4 / α-Al2O3 coating and a specific hydrogen resistance testing method.

[0031] like Figure 1 As shown, a device for testing the hydrogen barrier performance of the surface coating of a closed-port special-shaped part includes a special-shaped part inner tube 1, a special-shaped part outer tube 2, a temperature control system 9, and a deuterium current signal monitoring module 10. The special-shaped part inner tube 1 is a closed cavity with one end open, and the special-shaped part outer tube 2 is arranged on the periphery of the special-shaped part inner tube 1. The inner cavity of the special-shaped part inner tube 1 is a pipe inner chamber 4, and a pipe outer chamber 5 is formed between the special-shaped part inner tube 1 and the special-shaped part outer tube 2. The inner wall of the special-shaped part inner tube 1 or the inner wall and outer wall of the special-shaped part inner tube 1 are coated with a hydrogen barrier coating 6.

[0032] The upper opening of the shaped component's outer tube 2 is sealed against the outer wall of the shaped component's inner tube 1 by an inner tube attachment ring 3. This inner tube attachment ring 3 is a circular cylinder with a width of 5-15 mm and a height of 3-5 mm, formed by lathing 10-20 mm from the top outlet of the shaped component. Its inner diameter matches the outer diameter of the inner tube, forming an annular "ear" structure at the top to prevent the impact of the device's outer tube welding on the shaped component's internal and external surface coatings. The "ear" structure is located 10-20 mm from the top outlet of the shaped component to facilitate welding of the outer tube to form an internal and external sealed chamber. The design of the annular cylinder not only forms a closed downstream space with the device's outer tube, but also greatly minimizes damage to the internal shaped component's surface coating caused by welding the outer tube.

[0033] The upper opening of the shaped inner tube 1 is connected to a gas input line via an air inlet fixture module 7, which is used to introduce deuterium gas into the inner chamber 4 of the tube. The outer chamber 5 of the tube is connected to a deuterium current signal monitoring module 10 via an outer chamber fixture module 8. The deuterium current signal monitoring module 10 is used to collect deuterium atoms that penetrate through the hydrogen barrier coating 6 and the shaped inner tube 1 and display them as a current signal in the deuterium current signal monitoring module 10. The more deuterium atoms that penetrate, the stronger the current signal value.

[0034] The temperature control system 7 is a flip-top heating furnace, the temperature of which is controlled by a program. The inner tube 1 of the special-shaped part and the outer tube 2 of the special-shaped part are both in the furnace of the heating furnace. The gas input pipeline and the deuterium current signal monitoring module 10 are respectively located at the front and rear ends of the heating furnace, and are far away from each other. The temperature control system 7 is used to heat the entire component consisting of the inner chamber 4 and the outer chamber 5 of the pipe.

[0035] The material of the special-shaped component inner tube 1 is one or more of 321 and 316L austenitic stainless steels, low-alloy steels, precipitation-strengthened austenitic alloys, and the like. The inner tube sidewalls and bottom wall of the special-shaped component inner tube 1 are coated with an AlPO4 / α-Al2O3 coating (i.e., a hydrogen barrier coating 6). In practice, the surface of the closed-end special-shaped component is ground and polished before coating, achieving a surface roughness of less than Ra = 0.8.

[0036] The upstream of the special-shaped inner tube 1 is connected to the gas input pipeline, and the gas pipeline is segmented with 6 gas valves for controlling the input of deuterium gas in the gas circuit; the outer chamber 5 of the downstream part of the special-shaped inner tube 1 is connected to the deuterium current signal monitoring module 10.

[0037] The air inlet end tooling module 7 and the outer chamber tooling module 8 are used for disassembly and packaging of pipe fittings and upstream and downstream pipelines. The entire test device can be reused by replacing the silver-plated nickel gasket.

[0038] When welding the outer tube and the gas path tooling module, argon arc welding or laser welding is used. After each welding, a helium leak test is required to check the air tightness of the device.

[0039] The specific test method steps of this embodiment are as follows:

[0040] S1. After the inner and outer walls and bottom of the inner tube 1 of the special-shaped part are coated with an (Al-Zn)PO4 / α-Al2O3 coating (hydrogen barrier coating 6) through a pulling process, the outer tube 2 of the special-shaped part is welded to form a sealed outer chamber 5 of the pipe, and a helium leak test is performed to detect the airtightness of the outer chamber 5 of the pipe.

[0041] S2. Install the test piece to be tested (i.e., the integral component of the inner tube 1 of the inner special-shaped part coated with the hydrogen barrier coating 6 and the welded outer tube 2 of the special-shaped part) on the test tooling module, and seal the tooling module with a silver-plated nickel gasket to form a closed space including the upstream of the inner chamber and the downstream of the outer chamber separated by the pipe fitting. The upstream of the inner chamber is the inner chamber 4 of the pipe fitting formed by the inner tube wall and the bottom end, and the downstream of the outer chamber is the outer chamber 5 of the pipe fitting formed by the ear ring structure and the outer pipe fitting welded at the back.

[0042] S3. Turn on the upstream and downstream foreline pumps to extract the gas from the inner and outer chambers. After the pressure in the chamber is lower than 8 Pa, turn on the molecular pump to accelerate the formation of a high vacuum environment in the chamber. This process lasts for 2 hours.

[0043] The gas pressure in the inner and outer chambers of S4 and S3 is lower than 1×10 -5 Pa, turn on the temperature control system 9, heat the entire component consisting of the inner chamber 4 and the outer chamber 5 of the pipe fitting, and further improve the vacuum degree of the chamber. The predetermined test temperature is 500-400℃, and the temperature is stabilized for 1 hour at intervals of 50℃. First, heat it to 500℃ for 50 minutes and then keep it at that temperature for 1 hour. Then, cool it to 450℃ for 5 minutes, keep it at that temperature for 1 hour, and then cool it to 400℃. After keeping it at that temperature for 1 hour, cool it with the furnace. The heating and cooling rate is 10℃ / min. During this process, the pressure of the inner and outer chambers is further reduced to 1×10 -5 Below Pa.

[0044] S5. When the gas pressure in the downstream chamber preset in S4 reaches the requirement, the four-stage mass spectrometer connected to the downstream outer chamber is turned on to collect the permeated deuterium ion current signal value of the downstream chamber.

[0045] S6. Turn off the upstream molecular pump, close the gas valve connected to the molecule, open the deuterium gas cylinder valve, and input deuterium gas into the upstream high vacuum chamber in stages through the gas input gas line. The deuterium gas input pressure value is controlled in real time through the needle valve on the gas line. After the deuterium gas pressure value is set to 40kPa, the deuterium gas flow input is turned off.

[0046] Figure 2 Light microscopy of (Al-Zn)PO4 / α-Al2O3 coating prepared on the inner and outer surfaces of special-shaped parts. Figure 2 (a) is a light microscope image of the special-shaped part without coating. It can be observed that the surface of the substrate is smooth and free of inclusions, with obvious metallic luster. Figure 2 (b) is a light microscope image of the (Al-Zn)PO4 / α-Al2O3 coating applied on the bottom of the pipe. It can be seen that the coating is completely applied on the bottom and side. Figure 2 Middle (c) is a comparison of the effects of coating and not coating the external coating of the pipe component. It can be seen that the coating is dark gray after heat treatment and is evenly distributed along the annular surface of the pipe. There is no coating shedding and incomplete coating. It can also be found that the "ear" area structure on the upper edge of the pipe component does not affect the preparation of the internal and external coatings of the special-shaped parts.

[0047] Figure 3 The deuterium ion permeation current diagram of the (Al-Zn)PO4 / α-Al2O3 coating prepared on the special-shaped parts after being encapsulated in an outer tube and the comparison diagram between the deuterium ion permeation current and the substrate permeability are compared. Figure 3 In (a), we can see that after the (Al-Zn)PO4 / α-Al2O3 composite coating was prepared on the surface of the irregular part, the deuterium ion current signal decreased by nearly three orders of magnitude. The deuterium ion penetration signal value was converted into the permeability by calculation. Figure 3 As shown in (b), it can be seen that the permeation reduction factor (PRF) of the coating reaches 1350 and 2020 at 400℃ and 450℃, indicating that the (Al-Zn)PO4 / α-Al2O3 composite coating effectively improves the hydrogen barrier performance of closed-port special-shaped parts.

[0048] Example 2

[0049] In this embodiment, the surface of the special-shaped part is coated with Cr / Cr x Test method for hydrogen barrier performance of N coating.

[0050] The specific steps for using this implementation case are as follows:

[0051] S1, the inner and outer walls and bottom of the inner tube 1 of the special-shaped part are coated with Cr / Cr by electroplating metal Cr and then nitriding heat treatment process. x After the N coating, the outer tube 2 of the special-shaped part is welded to form a sealed outer chamber 5 of the pipe, and a helium leak test is performed to check its airtightness.

[0052] S2. Install the test piece to be tested on the test fixture module, and seal the fixture module with a silver-plated nickel gasket to form an upstream and downstream closed space separated by pipes.

[0053] S3. Turn on the upstream and downstream foreline pumps to extract the gas from the inner and outer chambers. After the pressure in the chamber is lower than 8 Pa, turn on the molecular pump to accelerate the formation of a high vacuum environment in the chamber. This process lasts for 2 hours.

[0054] The gas pressure in the chambers described in S4 and S3 is lower than 1×10 -5 Pa, turn on the temperature control system, heat the inner and outer chambers to further improve the chamber vacuum. The predetermined test temperature is 550-400℃, and the temperature is stabilized for 1 hour at intervals of 50℃. The temperature is first raised to 500℃ for 53 minutes and then kept at this temperature for 1 hour. The temperature is then lowered to 450℃ for 5 minutes, kept at this temperature for 1 hour, and then lowered to 400℃. After keeping this temperature for 1 hour, the temperature is cooled with the furnace. The heating and cooling rate is 10℃ / min. During this process, the pressure of the inner and outer chambers is further reduced to 1×10 -5 Below Pa.

[0055] S5. After the pressure in the S3 chamber reaches the requirement, turn on the four-stage mass spectrometer connected to the downstream to collect the deuterium permeation deuterium ion current signal value of the outer chamber.

[0056] S6. Close the valves of the upstream molecular pump and the forepump system, open the deuterium gas valve, and input deuterium gas into the upstream high vacuum chamber in stages through the gas input line. The deuterium gas input pressure value is controlled in real time by the needle valve on the gas line. After the deuterium gas pressure value in the upstream chamber is set to 40 kPa, the deuterium gas flow input is closed.

[0057] Figure 4 To prepare Cr / Cr on special-shaped parts by electroplating nitriding x The optical microscope image of the N coating shows that the chromium nitride coating produced by the nitriding heat treatment of the electroplated Cr layer on the shaped part is effective. The "ear" area structure on the upper edge of the shaped part also does not affect the coating preparation. Figure 4 (a) shows that the coating on the inner surface of the special-shaped part is completely and evenly covered. Figure 4 (b) shows that Cr is also generated on the outer surface of the special-shaped part. x N coating is the advantage of this process in forming and preparing pipe fittings. The coating of the inner and outer surfaces of special-shaped parts can effectively improve their hydrogen permeation resistance.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A device for testing the hydrogen barrier performance of the surface coating of a closed-end special-shaped part, characterized in that: The special-shaped inner tube comprises a special-shaped outer tube, a temperature control system, and a deuterium current signal monitoring module; the special-shaped inner tube is a closed cavity with an opening at one end, the special-shaped outer tube is arranged on the periphery of the special-shaped inner tube, the inner cavity of the special-shaped inner tube is an inner cavity of the tube, and an outer cavity of the tube is formed between the special-shaped inner tube and the special-shaped outer tube, and the inner wall of the special-shaped inner tube or the inner wall and the outer wall of the special-shaped inner tube are coated with a hydrogen barrier coating; the upper opening of the special-shaped inner tube is connected to the gas input pipeline through the air inlet end tooling module, which is used to connect deuterium gas to the inner cavity of the tube; the temperature control system is used to heat the entire component consisting of the inner cavity of the tube and the outer cavity of the tube; the outer cavity of the tube is connected to the deuterium current signal monitoring module through the outer cavity tooling module, and the deuterium current signal monitoring module is used to collect deuterium atoms that penetrate through the hydrogen barrier coating and the special-shaped inner tube and display them as current signals in the deuterium current signal monitoring module; The upper opening of the outer tube of the special-shaped part and the outer wall of the inner tube of the special-shaped part are connected and sealed by the inner tube attachment ring; The inner pipe attachment ring is an annular cylinder formed by turning at a distance of 10-20 mm from the top outlet of the special-shaped part; The width of the annular cylinder is 5-15 mm and the height is 3-5 mm. The annular cylinder is welded to the outer tube of the special-shaped part to form inner and outer closed chambers.

2. The hydrogen barrier performance testing device for the surface coating of a closed-end special-shaped part according to claim 1, characterized in that: The temperature control system is a flip-top heating furnace, the temperature of which is controlled by a program. The inner tube and outer tube of the special-shaped part are both in the furnace chamber of the heating furnace, and the gas input pipeline and the deuterium current signal monitoring module are respectively located at the front and rear ends of the heating furnace.

3. A method for using the device for testing the hydrogen barrier performance of the surface coating of a closed-end special-shaped part according to any one of claims 1 to 2, characterized in that: The method of use comprises the following steps: S1. After coating the inner and outer walls and bottom of the inner tube of the special-shaped part, weld the outer tube of the special-shaped part to form the outer cavity of the pipe fitting, and perform helium leak detection to test its air tightness; S2. Connecting the test piece consisting of the inner tube of the special-shaped part and the outer tube of the special-shaped part to the gas input pipeline through the air inlet end tooling module, and connecting the outer chamber of the tube to the deuterium current signal monitoring module through the outer chamber tooling module; S3. Turn on the upstream and downstream forepumps to extract the gas in the chamber. After the pressure in the chamber is lower than 10 Pa, turn on the molecular pump to accelerate the formation of a high vacuum environment in the chamber. S4, wait until the gas in the chamber reaches 1×10 -5 After the pressure reaches Pa, the temperature control system is turned on to heat the inner and outer chambers. The preset temperature is 300-700 °C, and the heating rate is 5-15 °C / min. S5. When the pressure in the preset chamber reaches the required value, the deuterium current signal monitoring module 10 connected to the outer chamber of the pipe is turned on to collect the permeated deuterium ion current signal value of the downstream outer chamber; S6. Close the upstream molecular pump and forepump system valves, open the deuterium gas valve, and input deuterium gas into the inner chamber of the pipe through the gas input pipeline. Control the deuterium gas input pressure value through the needle valve on the gas line. After setting the deuterium gas pressure value to 20-100 kPa, close the deuterium gas flow input. Combined with the hydrogen pressure of the pressure sensor, the steady-state current signal value output by the deuterium current signal monitoring module, and the temperature data of the deuterium current signal monitoring module, the permeability of the surface coating of the closed-port special-shaped part at a specified temperature is calculated.

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