A hydrogen barrier coating, method of making and use thereof

Abstract

The present application belongs to the technical field of hydrogen barrier coating, and particularly relates to a hydrogen barrier coating, a preparation method and application thereof. The hydrogen barrier coating comprises an alpha-Al-based solid solution layer above a substrate, Al2O3 micro-nano particles and SiO2 micro-nano particles dispersedly distributed in the alpha-Al-based solid solution layer, and an Al2O3 film layer covering the surface of the alpha-Al-based solid solution layer. The dense structure of the alpha-Al-based solid solution itself can block hydrogen atom penetration, enhance the interface between the phase particles and the substrate, prolong the diffusion path of hydrogen atoms in the material, increase the diffusion barrier, act as a hydrogen trapping trap, and the composite coating has the dual effects of hydrogen trapping and hydrogen blocking, thereby further reducing the hydrogen permeation rate. When the coating is slightly damaged, the surface after the damage is re-oxidized to form Al2O3, and has self-repairing capability. The composite coating is prepared by a brazing coating method, and has the advantages of simple preparation method, low cost, and industrialized batch production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydrogen barrier coating, and particularly relates to a hydrogen barrier coating and a preparation method and application thereof. BACKGROUND

[0002] In the process of global energy structure transformation to low carbonization, hydrogen energy has become a key energy carrier for promoting energy system decarbonization and addressing climate change due to its clean, efficient and recyclable characteristics, and has broad application prospects in the fields of transportation, energy storage and industry. However, the large-scale application of hydrogen energy is highly dependent on efficient, safe and low-cost transportation and storage technologies, and the safety hazards caused by the interaction between hydrogen and metal materials have become one of the core bottlenecks restricting the development of hydrogen energy industry.

[0003] Hydrogen molecules have extremely small atomic radius and extremely strong penetration ability. During the service process of hydrogen transportation and storage equipment, hydrogen can quickly penetrate into the metal matrix such as steel and aluminum alloy, causing the phenomenon of "hydrogen embrittlement" - hydrogen atoms accumulate at the defects of the metal lattice, resulting in a significant decrease in material plasticity and a sharp deterioration in toughness, and ultimately causing brittle fracture without obvious plastic deformation, which seriously threatens the structural integrity and service life of key equipment such as hydrogen transportation pipelines and hydrogen storage containers. In addition, hydrogen leakage not only causes waste of valuable hydrogen resources, but also easily causes explosion, fire and other major safety accidents due to the characteristics of wide explosion limit (4%~75% volume fraction) and high combustion rate of hydrogen, further increasing the safety risks of hydrogen transportation and storage. Therefore, developing protection technology that can effectively inhibit hydrogen penetration and improve the hydrogen embrittlement resistance of metal materials is an urgent need to ensure the safe use of hydrogen energy.

[0004] To solve the above problems, it has been proved that preparing a hydrogen barrier coating on the surface of metal materials is an effective means to block the hydrogen penetration path and improve the hydrogen embrittlement resistance of materials. At present, the hydrogen barrier coatings studied by the academic and industrial circles mainly fall into three categories: the first is oxide coatings; the second is non-oxide coatings; and the third is intermetallic compound coatings. However, the existing hydrogen barrier coatings and preparation technologies still have many technical defects to be solved: on the one hand, the thermal expansion coefficients of non-metallic hydrogen barrier coatings (such as oxide and non-oxide coatings) and metal matrix are significantly different, resulting in low interfacial bonding strength between the coating and the matrix, and defects such as micro-cracks and pores are easily generated in the coating, and the coating is prone to peeling off during service, which greatly reduces the hydrogen barrier effect; on the other hand, the existing coating preparation methods such as plasma spraying, aluminizing, and sol-gel method generally have problems such as low coating density, large number of defects, uneven particle size distribution, etc., which directly limit the hydrogen barrier performance of the coating.

[0005] Even for the relatively more excellent composite hydrogen barrier coating (such as SiO2 / α-Al2O3 composite coating), its mainstream preparation process (such as radio frequency magnetron sputtering, vapor deposition, etc.) still has problems such as complicated process flow, difficult precise control of coating thickness, high equipment cost, low production efficiency, etc., which is difficult to meet the large-scale industrialized preparation demand of large complex components such as hydrogen conveying pipeline and hydrogen storage container.

[0006] For example, the Chinese patent with publication number CN120231001A proposes a SiO2 and Al2O3 composite hydrogen barrier coating preparation method for hydrogen conveying pipeline based on radio frequency magnetron sputtering, which can realize the preparation of composite coating, but the radio frequency magnetron sputtering process needs to be carried out in a high vacuum environment, which has high requirements for equipment, and it is difficult to coat complex shape workpieces such as long conveying pipeline and special-shaped components, which is difficult to be applied on a large scale; the Chinese patent with publication number CN120193231A further optimizes the structure of SiO2 / α-Al2O3 composite hydrogen barrier coating (adopts a sandwich structure of substrate-SiO2-α-Al2O3), and improves the coating density and interface bonding force (the film-base bonding force reaches 8.5N) by controlling the magnetron sputtering parameters, but its core preparation process still relies on radio frequency magnetron sputtering, which also faces the limitations of high cost, low efficiency and narrow range of applicable workpieces in industrial application.

[0007] In summary, there is an urgent need in the field of hydrogen barrier coating to develop a new type of hydrogen barrier coating and its preparation method which has excellent hydrogen barrier performance, high interface bonding strength, simple preparation process and can be applied on a large scale, in order to break through the bottleneck of existing technology and meet the urgent needs of hydrogen energy industry for efficient, safe and low-cost hydrogen barrier protection technology. SUMMARY

[0008] In view of the above problems, in a first aspect, the present application provides a hydrogen barrier coating, which comprises an α-Al-based solid solution layer above a substrate and an Al2O3 thin film covering the surface of the α-Al-based solid solution layer.

[0009] The α-Al-based solid solution layer has Al2O3 micro-nano particles and SiO2 micro-nano particles dispersedly distributed therein.

[0010] In a second aspect, the present application provides a preparation method of a hydrogen barrier coating, which comprises the following steps:

[0011] Covering an Al-Si-based solder foil on the surface of the substrate to obtain a workpiece to be soldered and coated;

[0012] Placing the workpiece to be soldered and coated in a soldering and coating device into which a protective gas containing a certain amount of oxygen is introduced, and setting a soldering and coating heating curve to perform soldering and coating, the soldering and coating heating curve comprising a preheating stage, a heating stage, a soldering and coating holding stage and a cooling stage;

[0013] When the temperature of the heating stage is raised to the brazing temperature, the workpiece to be brazed is subjected to ultrasonic vibration, the ultrasonic vibration is stopped when the brazing holding stage ends and the temperature is reduced to 550℃ or lower, and the protection gas is stopped after the workpiece to be brazed is cooled to room temperature with the brazing device to obtain a hydrogen-blocking coating.

[0014] Further, the method further comprises polishing and sandblasting the surface of the substrate.

[0015] Further, the thickness of the Al-Si-based brazing filler foil strip is 0.05-0.2mm.

[0016] The mass percentage of Si is 5-12%, and the balance is Al, or the balance is Al and other trace alloying elements; the other trace alloying elements include one or more of 0.5-2% Cu, 0-0.5% Mg, and 0-0.8% Fe in any combination.

[0017] Further, the protection gas contains 0.1-0.5% oxygen by volume.

[0018] The protection gas is selected from one or more combinations of inert gases, specifically including one or more of argon, nitrogen, and helium, for example, it can be argon.

[0019] Further, the brazing heating curve is as follows:

[0020] In the preheating stage, the temperature is raised to 200-300℃ at a rate of 3-5℃ / min and held for 20-30min;

[0021] In the heating stage, the temperature is raised to 500-550℃ at a rate of 5-10℃ / min and held for 10-15min;

[0022] In the brazing holding stage, the temperature is raised to 600-650℃ at a rate of 5-10℃ / min and held for 10-20min;

[0023] In the cooling stage, the temperature is reduced to 500-550℃ at a rate of 3-5℃ / min and cooled with the brazing device.

[0024] Further, the brazing device is a box furnace equipped with an ultrasonic vibration assembly; wherein the ultrasonic vibration assembly includes an ultrasonic generator, a transducer, an amplitude transformer, and a vibration tool head.

[0025] When the temperature of the heating stage is raised to the brazing temperature, the ultrasonic generator is started to emit a high-frequency electric signal, the high-frequency electric signal is converted into mechanical vibration by the transducer, the vibration amplitude is amplified by the amplitude transformer and the energy is transmitted to the vibration tool head, and the vibration direction of the vibration tool head provides an ultrasonic vibration environment for the surface of the workpiece to be brazed in the box furnace for ultrasonic assisted brazing.

[0026] Further, the brazing temperature is 600-650 DEG C.

[0027] Further, the high frequency electric signal is 40-60 kHz.

[0028] In a third aspect, the application provides the use of the hydrogen barrier coating or the hydrogen barrier coating prepared by the preparation method of the hydrogen barrier coating in hydrogen barrier protection of pipeline steel for oil and gas transportation.

[0029] The beneficial effects of the application are as follows:

[0030] The hydrogen barrier coating of the application comprises an alpha-Al-based solid solution layer on the substrate, Al2O3 and SiO2 microparticles and nanoparticles dispersed in the alpha-Al-based solid solution layer coating, and an Al2O3 thin film layer on the surface. The alpha-Al-based solid solution is in contact with the substrate, the SiO2 and Al2O3 particles in the alpha-Al-based solid solution are the enhanced phase, and the Al2O3 thin film layer is on the surface. The dense structure of the alpha-Al-based solid solution coating can block the penetration of hydrogen atoms, the interface between the enhanced phase particles and the substrate can prolong the diffusion path of hydrogen atoms in the material, increase the diffusion barrier, and act as a hydrogen trapping trap, the composite coating has the dual effects of hydrogen trapping and hydrogen blocking, and the hydrogen permeation rate is further reduced. Even if the coating is slightly damaged, the damaged surface will be re-oxidized to form Al2O3, and the coating has self-repairing ability.

[0031] The hydrogen barrier coating is prepared by brazing coating technology (brazing coating technology), and trace oxygen is introduced into the protective gas during preparation; secondly, in terms of ultrasonic vibration, if the generated oxide film is not dispersed, it will hinder the connection between the substrate and the coating, resulting in poor bonding strength, and continuous thickening will increase the brittleness of the coating. In the brazing process, ultrasonic vibration is added to disperse the generated oxides, so that they do not affect the connection performance and become the enhanced phase. The hydrogen barrier coating has the advantages of high bonding strength between the coating and the substrate, dense coating without pores or microcracks, uniform and stable composition, strong process controllability, easy adjustment of coating thickness, wide application range of substrate, and uniform coating on complex shape surfaces. It provides a new idea for solving the technical problems of existing hydrogen barrier coatings.

[0032] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the application. The objects and other advantages of the present application can be achieved and obtained by the structures indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and the other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0034] Figure 1 The structural schematic diagram of the hydrogen barrier coating proposed in the embodiments of the present application is shown.

[0035] Figure 2 The structural schematic diagram of the ultrasonic vibration system added to the box furnace in the embodiments of the present application is shown.

[0036] Figure 3 The brazing and heating curve of the hydrogen barrier coating proposed in the embodiments of the present application is shown.

[0037] Figure 4 The internal microstructure diagram of the composite coating is shown.

[0038] Figure 2 In the embodiments, 1, box furnace; 2, storage plate; 3, workpiece to be brazed and coated; 4, amplitude bar; 5, sealing flange; 6, vibration tool head; 7, transducer; 8, ultrasonic generator; 9, connecting rod; 10, transmission line. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the protection scope of the present application.

[0040] The present application proposes a hydrogen barrier coating, as shown in the drawings, the hydrogen barrier coating comprises an α-Al-based solid solution layer above a substrate and an Al2O3 film covering the surface of the α-Al-based solid solution layer. Figure 1

[0041] The α-Al-based solid solution layer dispersively contains Al2O3 micro-nano particles and SiO2 micro-nano particles as reinforcing phases.

[0042] The present application proposes a preparation method of the hydrogen barrier coating, the method comprises the following steps:

[0043] S1: polishing the surface of the substrate to be prepared into a coating, and performing sand blasting treatment on the polished surface;

[0044] ​S2: uniformly cover the Al-Si-based filler foil on the surface of the coating substrate to obtain a workpiece to be brazed and coated;

[0045] S3: placing the workpiece to be brazed and coated in a brazing and coating device into which a protective gas containing a certain amount of oxygen is introduced, setting a brazing and coating heating curve, and brazing and coating the workpiece to be brazed and coated according to the brazing and coating heating curve, the brazing and coating heating curve including a preheating stage, a heating-up stage, a brazing and coating holding stage, and a cooling stage;

[0046] S4: when the temperature of the heating-up stage rises to the brazing and coating temperature, ultrasonic vibration is applied to the workpiece to be brazed and coated, the vibration is stopped when the brazing and coating holding time ends and the temperature drops to below 550℃, and the workpiece to be brazed and coated is cooled to room temperature with the brazing and coating device, and the protective gas is stopped to obtain a hydrogen barrier coating.

[0047] In step S2, the thickness of the Al-Si-based filler foil is 0.05-0.2mm, the mass percentage of Si is 5%-12%, and the balance is Al, or the balance is Al and other trace alloying elements;

[0048] The other trace alloying elements include one or more of 0.5%-2% Cu, 0%-0.5% Mg, and 0-0.8% Fe in any combination, and the melting point of the Al-Si-based filler foil is 577-610℃.

[0049] In step S3, the protective gas contains 0.1%-0.5% oxygen by volume; and the protective gas is one or more of inert gases, specifically including one or more of argon, nitrogen, and helium.

[0050] The brazing and coating heating curve is as follows:

[0051] In the preheating stage, the temperature is heated at a rate of 3-5℃ / min to 200-300℃ for 20-30min;

[0052] In the heating-up stage, the temperature is heated at a rate of 5-10℃ / min to 500-550℃ for 10-15min;

[0053] In the brazing and coating holding stage, the temperature is heated at a rate of 5-10℃ / min to 600-650℃ for 10-20min;

[0054] In the cooling stage, the temperature is cooled at a rate of 3-5℃ / min to 500-550℃, and the workpiece to be brazed and coated is cooled with the brazing and coating device.

[0055] Based on the above method, the present application proposes a brazing and coating device suitable for the preparation method, the structure of the brazing and coating device is as follows: Figure 2As shown, the brazing coating device is a box furnace 1 equipped with an ultrasonic vibration assembly, which includes an ultrasonic generator 8, a transducer 7, a variable amplitude rod 4 and a vibration tool head 6; when the temperature rises to the brazing coating temperature in the heating stage, the ultrasonic generator 8 is started to emit a high-frequency electric signal, which is converted into mechanical vibration by the transducer 7, and the vibration amplitude is amplified by the variable amplitude rod 4 and the energy is transmitted to the vibration tool head 6, and the vibration direction of the vibration tool head 6 provides an ultrasonic vibration environment for the surface of the workpiece 3 in the ultrasonic vibration environment 3 in the box furnace 1.

[0056] In one embodiment of the present application, as shown in Figure 2 As shown, the brazing coating device includes a box furnace 1, and a placing plate 2 is arranged inside the box furnace 1, and the workpiece 3 to be brazed is placed on the placing plate 2. The variable amplitude rod 4 penetrates through the inner wall of the box furnace 1 and is fixed and sealed by a sealing flange 5, the furnace end is connected with the vibration tool head 6 and is auxiliary fixed by a connecting rod 9, and the outer end is connected with the transducer 7, the transducer 7 is connected with the external ultrasonic generator 8 through a transmission line 10, and finally the vibration tool head 6 is vibrated to provide an ultrasonic vibration environment for the workpiece to be brazed in the box furnace 1. The variable amplitude rod 4 is connected with the outside through the sealing flange 5, and the vibration tool head 6 is installed in the furnace by means of the connecting rod 9. In the figure, the inner part of the box furnace 1 is defined as the core working cavity by the dashed box, and the placing plate 2 is fixedly arranged in the cavity; the workpiece 3 to be brazed is placed on the upper surface of the placing plate 2 in a detachable manner, forming a stable bearing positioning of the workpiece, and ensuring that the workpiece 3 to be brazed is in the preset heating and vibration action area inside the box furnace 1.

[0057] In one embodiment of the present application, the variable amplitude rod 4 is a through structure, one end of which extends into the box furnace 1, and the other end extends out of the box furnace 1; the variable amplitude rod 4 is fixedly connected and sealed with the inner wall of the box furnace 1 at the penetration position, one end of the sealing flange 5 is welded or bolted with the inner wall of the box furnace 1, and the other end is matched with the variable amplitude rod 4 through a sealing element (not marked in the figure, which is a conventional sealing structure), to prevent the temperature field and the protective gas in the box furnace 1 from leaking.

[0058] In one embodiment of the present application, the vibration tool head 6 is fixedly installed on the end of the variable amplitude rod 4 located inside the box furnace 1 in a threaded connection or welding manner; at the same time, the vibration tool head 6 is auxiliary fixed with the variable amplitude rod 4 through the connecting rod 9, the two ends of the connecting rod 9 are bolted with the rod body of the variable amplitude rod 4 and the side wall of the vibration tool head 6 respectively, to ensure the structural stability of the vibration tool head 6 in the ultrasonic vibration process, and the lower end surface of the vibration tool head 6 is kept at a preset gap or in contact with the upper surface of the workpiece 3 to be brazed (which is set according to the brazing process requirement).

[0059] In an embodiment of the present application, the transducer 7 is fixedly installed on the end of the horn 4 protruding out of the box furnace 1 in a flange connection or threaded connection manner, and the vibration output end of the transducer 7 is coaxially connected with the input end of the horn 4, thereby ensuring efficient transmission of ultrasonic vibration energy.

[0060] In an embodiment of the present application, the ultrasonic generator 8 is arranged in a non-high-temperature area outside the box furnace 1, and the output end thereof is electrically connected with the input end of the transducer 7 through the transmission line 10. The two ends of the transmission line 10 are detachably connected (such as plug and socket cooperation) with the terminal of the ultrasonic generator 8 and the terminal of the transducer 7, thereby forming an electrical signal transmission path for ultrasonic driving. The high-frequency electrical signal generated by the ultrasonic generator 8 is transmitted to the transducer 7 through the transmission line 10, the transducer 7 converts the high-frequency electrical signal into mechanical vibration energy and transmits it to the horn 4, the horn 4 amplifies the vibration amplitude and then transmits the vibration energy to the workpiece 3 to be brazed in the box furnace 1 through the vibration tool head 6 fixed by the connecting rod 9, and finally provides the workpiece 3 to be brazed with an ultrasonic vibration environment required by the brazing process.

[0061] The preparation process of the hydrogen-blocking coating is exemplarily described below in combination with an embodiment.

[0062] Embodiment 1

[0063] The present embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen-blocking coating, and the specific steps are as follows:

[0064] Step one, select an X65 pipeline steel plate as the substrate of the coating, and the size of the substrate is selected to be 100mm×100mm×10mm. The surface of the substrate is polished and sanded, and the surface after polishing is sandblasted;

[0065] Step two, select 0.1mm-thick Al-8Si foil strip (i.e., the mass percentage of Si is 8% and the mass percentage of Al is 92%) as the brazing filler material for the coating, uniformly cover the Al-8Si filler foil strip on the surface of the substrate, and place 3 layers to obtain the workpiece 3 to be brazed;

[0066] Step three, place the workpiece 3 to be brazed assembled in step two on the placement plate 2 in the box furnace 1, and introduce ordinary industrial-grade argon gas with a purity of 99.9% into the box furnace 1 for protection, but a trace amount of oxygen gas accounting for 0.5% of the total gas volume is reserved;

[0067] Step four, set the brazing heating curve, and start heating the box furnace 1. The brazing heating curve includes the following stages:

[0068] (1) preheating stage: heat at a rate of 5℃ / min to 250℃ and keep for 30min;

[0069] (2) heating stage: heating to 550℃ at a rate of 10℃ / min and maintaining for 15min;

[0070] (3) brazing and holding stage: heating to 650℃ at a rate of 10℃ / min and maintaining for 15min;

[0071] (4) cooling stage: cooling to 550℃ at a rate of 5℃ / min and cooling with the brazing device.

[0072] Step five, when the temperature is raised to the brazing temperature of 650℃, start the ultrasonic generator 8 to apply 50kHz high frequency ultrasonic vibration to the opposing plate 2; when the brazing and holding stage is over and the temperature is lowered to below 550℃, turn off the ultrasonic generator 8.

[0073] Step six, after the brazed workpiece 3 is cooled to room temperature with the box furnace 1, stop the protection gas and take out the finished product.

[0074] Finally, an in-situ reinforced Al-based hydrogen barrier coating with a thickness of about 0.3mm is obtained.

[0075] Example 2

[0076] This example provides a method for preparing an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0077] Step one, select X65 pipeline steel plate as the substrate of the coating, and the size of the substrate is selected to be 100mm×100mm×10mm. The surface of the substrate is polished and sandblasted after polishing;

[0078] Step two, select 0.1mm thick Al-10Si (i.e. the mass percentage of Si is 10% and the mass percentage of Al is 90%) foil brazing filler metal as the brazing layer raw material, uniformly cover the Al-10Si brazing filler metal foil on the surface of the substrate, and place 3 layers to obtain the brazed workpiece 3;

[0079] Step three, place the brazed workpiece 3 assembled in step two on the opposing plate 2 in the box furnace 1, and introduce ordinary industrial grade argon gas with a purity of 99.9% into the box furnace 1, but retain 0.5% of trace oxygen;

[0080] Step four, set the brazing heating curve, and start the box furnace 1 heating. The brazing heating curve includes the following stages:

[0081] (1) preheating stage: heating to 250℃ at a rate of 5℃ / min and maintaining for 30min;

[0082] (2) heating stage: heating to 550℃ at a rate of 10℃ / min and maintaining for 15min;

[0083] (3) Brazing coating holding stage: heating to 630℃ at a rate of 10℃ / min and holding for 15 min;

[0084] (4) Cooling stage: cooling to 550℃ at a rate of 5℃ / min and cooling with the brazing device.

[0085] Step five, when the temperature rises to the brazing temperature of 630℃, start the ultrasonic generator 8 to apply 50kHz high-frequency ultrasonic vibration to the opposing plate 2; when the heating time ends and the temperature drops below 550℃, turn off the ultrasonic generator 8.

[0086] Step six, after the brazing workpiece 3 cools to room temperature with the box furnace 1, stop the argon flow and take out the finished product.

[0087] Finally, an in-situ reinforced Al-based hydrogen barrier coating with a thickness of about 0.3mm is obtained, and the internal microstructure is shown in Figure 4 As can be seen from the figure, the α-Al solid solution is the matrix part of the coating, providing basic structural support for the coating. The dispersed distribution of Al2O3 and SiO2 microparticles as reinforcing phases can hinder hydrogen permeation and also help improve the mechanical properties of the coating. This dispersed distribution of reinforcing phases is conducive to fully exerting their improvement effect on the performance of the coating.

[0088] Example 3

[0089] The embodiment provides a preparation method of an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0090] Step one, select X65 pipeline steel plate as the matrix of the coating, and select the size of the matrix as 100mm×100mm×10mm. Polish the surface of the matrix, and perform sandblasting treatment on the polished surface;

[0091] Step two, select 0.1mm thick Al-12Si (i.e. the mass percentage of Si is 12% and the mass percentage of Al is 88%) foil brazing filler metal as the brazing coating raw material, uniformly cover the Al-12Si brazing filler metal foil on the surface of the matrix, and place 3 layers to obtain a brazing workpiece 3;

[0092] Step three, place the brazing workpiece 3 assembled in step two on the plate 2 in the box furnace 1, and introduce ordinary industrial-grade argon gas with a purity of 99.9% into the box furnace 1 for protection, but retain 0.5% of trace oxygen.

[0093] Step four, set the brazing heating curve, and start heating the box furnace 1. The brazing heating curve includes the following stages:

[0094] (1) Preheating stage: heating to 250℃ at a rate of 5℃ / min and holding for 30 min;

[0095] (2) heating stage: heating to 550℃ at a heating rate of 10℃ / min and holding for 15min;

[0096] (3) brazing and holding stage: heating to 610℃ at a heating rate of 10℃ / min and holding for 15min;

[0097] (4) cooling stage: cooling to 550℃ at a cooling rate of 5℃ / min, and cooling with the brazing device.

[0098] Step five, when the temperature is raised to the brazing temperature of 610℃, start the ultrasonic generator 8 to apply 50kHz high frequency ultrasonic vibration to the opposing plate 2; when the brazing and holding stage ends and the temperature drops to below 550℃, turn off the ultrasonic generator 8.

[0099] Step six, after the brazed workpiece 3 is cooled to room temperature with the box furnace 1, stop the argon flow and take out the finished product.

[0100] Finally, an in-situ reinforced Al-based hydrogen barrier composite coating with a thickness of about 0.3mm is obtained.

[0101] Comparative Example 1

[0102] X65 pipeline steel plate is selected as the comparative example.

[0103] Comparative Example 2

[0104] The present embodiment provides a preparation method of an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0105] Step one, select X65 pipeline steel plate as the substrate of the coating, and the size of the substrate is selected to be 100mm×100mm×10mm. The surface of the substrate is polished and sandblasted after polishing;

[0106] Step two, select 0.1mm thick Al-10Si foil brazing filler metal as the raw material of the brazing layer, uniformly cover the Al-10Si brazing filler metal foil on the surface of the substrate, and place 3 layers to obtain the brazed workpiece 3;

[0107] Step three, place the assembled brazed workpiece 3 in step two on the plate 2 in the box furnace 1, and introduce ordinary industrial grade argon gas with a purity of 99.9% into the box furnace 1 for protection, but retain 0.5% of trace oxygen;

[0108] Step four, set the brazing heating curve, and start heating the box furnace 1. The brazing heating curve includes the following stages:

[0109] (1) preheating stage: heating to 250℃ at a heating rate of 5℃ / min and holding for 30min;

[0110] (2) heating stage: heating to 550℃ at a heating rate of 10℃ / min and keeping for 15min;

[0111] (3) brazing and holding stage: heating to 630℃ at a heating rate of 10℃ / min and keeping for 15min;

[0112] (4) cooling stage: cooling to 550℃ at a cooling rate of 5℃ / min and cooling with the brazing device.

[0113] Step five, after the brazing workpiece 3 is cooled to room temperature with the box furnace 1, stop the argon gas, and take out the finished product.

[0114] Finally, because the protective gas contains oxygen, an oxide film is formed during the melting of the filler metal, which hinders the combination of the liquid filler metal and the steel substrate, and an intact Al-based coating is not obtained.

[0115] Comparative Example 3

[0116] The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0117] Step one, select X65 pipeline steel plate as the substrate, the size of the substrate is 100mmx100mmx10mm, polish the surface of the substrate to be prepared, and perform sand blasting treatment on the polished surface;

[0118] Step two, select 0.1mm thick Al-10Si foil brazing filler metal as the brazing coating raw material, uniformly cover the Al-10Si filler metal foil on the surface of the substrate, and place 3 layers to obtain a brazing workpiece 3;

[0119] Step three, place the brazing workpiece 3 assembled in step two on the placement plate 2 in the box furnace 1, and introduce high-purity argon gas with a purity of 99.999% into the box furnace 1 for protection;

[0120] Step four, set the brazing heating curve, and start the box furnace 1, the brazing heating curve includes the following stages:

[0121] (1) preheating stage: heating to 250℃ at a heating rate of 5℃ / min and keeping for 30min;

[0122] (2) heating stage: heating to 550℃ at a heating rate of 10℃ / min and keeping for 15min;

[0123] (3) brazing and holding stage: heating to 630℃ at a heating rate of 10℃ / min and keeping for 15min;

[0124] (4) cooling stage: cooling to 550℃ at a cooling rate of 5℃ / min and cooling with the brazing device.

[0125] Step five, after the brazing coated workpiece 3 cools with the box furnace 1 to room temperature, stop the argon gas, take out the finished product.

[0126] Finally, an Al-based hydrogen barrier coating with a thickness of about 0.3 mm is obtained.

[0127] Comparative Example 4

[0128] The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0129] Step one, select X65 pipeline steel plate as the substrate, and the size of the substrate is 100mm*100mm*10mm. The surface of the substrate is polished and sandblasted.

[0130] Step two, select 0.1mm thick Al-20Si foil as the brazing filler material, uniformly cover the Al-20Si filler foil on the surface of the substrate, and place 3 layers to obtain the brazing coated workpiece 3.

[0131] Step three, place the brazing coated workpiece 3 assembled in step two on the placement plate 2 in the box furnace 1, and introduce ordinary industrial argon gas with a purity of 99.9% into the box furnace 1 for protection, but 0.5% of trace oxygen is reserved.

[0132] Step four, set the brazing heating curve, and start the box furnace 1 to heat. The brazing heating curve includes the following stages:

[0133] (1) preheating stage: heat to 250℃ at a heating rate of 5℃ / min and keep for 30min;

[0134] (2) heating stage: heat to 550℃ at a heating rate of 10℃ / min and keep for 15min;

[0135] (3) brazing holding stage: heat to 700℃ at a heating rate of 10℃ / min and keep for 15min;

[0136] (4) cooling stage: cool to 550℃ at a cooling rate of 5℃ / min, and cool the brazing device.

[0137] Step five, when the temperature rises to the brazing temperature 700℃, start the ultrasonic generator 8 to apply 50kHz high-frequency ultrasonic vibration to the placement plate 2; when the heating time ends and the temperature drops to below 550℃, stop the ultrasonic generator 8.

[0138] Step six, after the brazing coated workpiece 3 cools with the box furnace 1 to room temperature, stop the argon gas, take out the finished product.

[0139] The in-situ reinforced Al-based hydrogen barrier composite coating with a thickness of about 0.3 mm is finally obtained, and due to the excessive Si content in the filler, coarse granular Si elements exist in the alloy matrix after solidification, microcracks exist in the coating, and the bonding strength with the substrate is low.

[0140] Comparative Example 5

[0141] The embodiment provides a preparation method of an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows:

[0142] Step one, an X65 pipeline steel plate is selected as a substrate, the size of the substrate is 100 mm*100 mm*10 mm, the surface of the substrate to be prepared into a coating is polished, and sand blasting treatment is performed on the polished surface;

[0143] Step two, 0.1 mm thick pure Al foil is selected as a filler for the brazing coating, the pure Al foil is uniformly covered on the surface of the substrate, and three layers of the pure Al foil are placed to obtain a workpiece to be brazed 3;

[0144] Step three, the workpiece to be brazed 3 assembled in step two is fixed on the placement plate 2 in the box furnace 1, and ordinary industrial argon with a purity of 99.9% is introduced into the box furnace 1 for protection, but a trace amount of oxygen with a volume fraction of 0.5% is reserved;

[0145] Step four, a brazing and coating heating curve is set, and the box furnace 1 is started to heat, and the brazing and coating heating curve comprises the following stages:

[0146] (1) preheating stage: heating at 5 ℃ / min to 250 ℃ and keeping for 30 min;

[0147] (2) heating stage: heating at 10 ℃ / min to 550 ℃ and keeping for 15 min;

[0148] (3) brazing and coating keeping stage: heating at 10 ℃ / min to 700 ℃ and keeping for 15 min;

[0149] (4) cooling stage: cooling at 5 ℃ / min to 550 ℃, and cooling with the furnace.

[0150] Step five, when the temperature rises to the brazing and coating temperature 700 ℃, the ultrasonic generator 8 is started to apply 50 kHz high-frequency ultrasonic vibration to the placement plate 2; when the heating time ends and the temperature drops to below 550 ℃, the ultrasonic generator 8 is turned off.

[0151] Step six, after the workpiece to be brazed 3 cools to room temperature with the box furnace 1, the argon gas is stopped, and the finished product is taken out.

[0152] The Al-based coating with a thickness of about 0.3 mm is finally obtained, and due to the pure Al filler, the amount of Al2O3 generated in the composite coating after solidification is small, and the hydrogen barrier effect of the coating is poor.

[0153] Test Example 1

[0154] The bonding strength of the coating and the substrate was measured by a compression shear test. An axial force was applied to the punch from a 180° position to separate the coating from the substrate in the radial direction. The bonding strength was calculated by the maximum thrust force and the contact area (unit: MPa). The hydrogen permeation reduction factor of the hydrogen barrier coating was detected by a hydrogen permeation method. The test results of the hydrogen barrier coating in Examples 1-3 and Comparative Examples in the substrate bonding strength and the hydrogen permeation reduction factor are shown in Table 1:

[0155] Table 1

[0156]

[0157] In the table, " / " means that this test was not performed. As can be seen from Table 1, Comparative Example 1 is an original X65 pipeline steel (without coating), and the hydrogen permeation reduction factor PRF = 1 (indicating no hydrogen barrier effect), which directly proves that the Al-based hydrogen barrier coating is the core of the hydrogen barrier property of the substrate, and the coating prepared by optimizing the process (Examples 1-3) can improve the hydrogen barrier ability by 7200-7500 times.

[0158] Examples 1-3, Comparative Examples 2 / 4 / 5 all have a trace amount of 0.5% oxygen in the protective gas, and after ultrasonic vibration, sufficient Al2O3 and SiO2 micro-nano particles (hydrogen barrier enhancement phase) can be generated in situ in the coating, and the PRF is all above 280 (Examples are more than 7000); Comparative Example 3 uses 99.999% high-purity argon gas (without trace oxygen), although the bonding strength reaches 86.54 MPa (close to Example 3), but due to the lack of oxygen to participate in the reaction, the amount of enhancement phase generated is very small, and the PRF is only 870 (less than 12% of Example 2), and the hydrogen barrier effect is significantly reduced. This further illustrates that trace oxygen can promote the reaction of Al and Si with oxygen to generate Al2O3 and SiO2 micro-nano particles, and these micro-nano particles can effectively hinder hydrogen permeation, which is an important factor for improving PRF (ultrasonic vibration is required to break the oxide film to avoid its influence on the bonding).

[0159] Examples 1-3 all apply 50 kHz ultrasonic vibration during the brazing coating stage (610-650°C), and the final coating bonding strength reaches more than 86.98 MPa; Comparative Example 2 has almost the same process as Example 2 (same Al-10Si filler, same protective gas, same 630°C brazing coating temperature), only lacking the ultrasonic vibration step, and the result is that the oxide film is formed when the filler is melted, which hinders the bonding with the substrate, and an intact coating cannot be obtained (no bonding strength and PRF data). This can illustrate that ultrasonic vibration can effectively break the oxide film at the interface between the filler and the substrate, ensuring the wetting and bonding of the liquid filler with the substrate, which is the core guarantee for the formation of the coating.

[0160] As can be seen from Comparative Examples 4 and 5 and Example 2, when the brazing filler metal is pure Al, although the bonding strength reaches 89.43 MPa (close to that of the example), the amount of Al2O3 generated after solidification is extremely small (the hydrogen barrier core phase is insufficient), resulting in a PRF of only 280, and the hydrogen barrier effect is greatly deteriorated. When the Si content is increased to 20% (Comparative Example 4), although a complete coating can be prepared, coarse Si elemental particles appear in the alloy matrix after solidification, causing microcracks in the coating, the bonding strength drops sharply to 53.67 MPa (only 56.8% of that of Example 2), the PRF is only 350 (only 5% of that of Example 2), and the structural integrity and performance are both impaired.

[0161] Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A hydrogen-barrier coating, characterized in that, The hydrogen barrier coating includes an α-Al-based solid solution layer above the substrate and an Al2O3 film covering the surface of the α-Al-based solid solution layer. The α-Al-based solid solution layer contains dispersed Al2O3 micro / nano particles and SiO2 micro / nano particles.

2. A method for preparing a hydrogen-barrier coating, characterized in that, The preparation of the hydrogen-barrier coating according to claim 1 includes the following steps: An Al-Si based solder foil is applied to the surface of a substrate to obtain a workpiece to be soldered; the mass percentage of Si in the Al-Si based solder foil is 5% to 12%. The workpiece to be brazed is placed in a brazing apparatus purged with a protective gas containing a fixed amount of oxygen. A brazing heating curve is set for brazing, which includes a preheating stage, a heating stage, a brazing holding stage, and a cooling stage. The brazing heating curve is as follows: Preheating stage: heating to 200-300℃ at a heating rate of 3-5℃ / min and holding for 20-30 min; Heating stage: heating to 500-550℃ at a heating rate of 5-10℃ / min and holding for 10-15 min; Brazing holding stage: heating to 600-650℃ at a cooling rate of 5-10℃ / min and holding for 10-20 min; Cooling stage: cooling to 500-550℃ at a cooling rate of 3-5℃ / min, and cooling with the brazing apparatus. When the temperature rises to the brazing temperature during the heating stage, the workpiece to be brazed is subjected to ultrasonic vibration. When the brazing and heat preservation stage ends and the temperature drops below 550°C, the ultrasonic vibration is stopped. After the workpiece is cooled to room temperature by the brazing device, the protective gas is stopped to obtain the hydrogen-barrier coating.

3. The method for preparing the hydrogen-barrier coating according to claim 2, characterized in that, The method also includes grinding and polishing the surface of the coating substrate, as well as sandblasting.

4. The method for preparing the hydrogen-barrier coating according to claim 3, characterized in that, The thickness of the Al-Si based solder foil is 0.05~0.2mm; The Al-Si based solder foil has Al as the balance element, or Al and other trace alloying elements as the balance element. The other trace alloying elements include one or more combinations of Cu, Mg, and Fe, with a mass percentage of 0.5% to 2% and 0% to 0.5% respectively.

5. The method for preparing the hydrogen-barrier coating according to claim 2, characterized in that, The protective gas contains 0.1% to 0.5% oxygen by volume; The protective gas is selected from one or more combinations of inert gases.

6. The method for preparing the hydrogen-barrier coating according to claim 2, characterized in that, The brazing device is a box furnace equipped with an ultrasonic vibration assembly; wherein, the ultrasonic vibration assembly includes an ultrasonic generator, a transducer, an amplitude transformer, and a vibration tool head; When the temperature rises to the soldering temperature during the heating stage, the ultrasonic generator is activated to emit a high-frequency electrical signal. The high-frequency electrical signal is converted into mechanical vibration by the transducer, and the vibration amplitude is amplified by the amplitude transformer and the energy is transmitted to the vibrating tool head. The vibration direction of the vibrating tool head provides an ultrasonic vibration environment for the surface of the workpiece to be soldered in the oven for ultrasonic-assisted soldering.

7. The method for preparing the hydrogen-barrier coating according to claim 3, characterized in that, The soldering temperature is 600~650℃.

8. The method for preparing the hydrogen-barrier coating according to claim 6, characterized in that, The high-frequency electrical signal is 40~60kHz.

9. The application of the hydrogen barrier coating according to claim 1 or the hydrogen barrier coating prepared by the preparation method of any one of claims 2-8 in hydrogen barrier protection of pipeline steel for oil and gas transportation.

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