Hydrogen-resistant coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of hydrogen-resistant coatings, and particularly relates to a hydrogen-resistant coating as well as a preparation method and application thereof. The hydrogen-resistant coating comprises an alpha-Al-based solid solution layer on the substrate, Al2O3 micro-nano particles and SiO2 micro-nano particles which are dispersed and distributed in the alpha-Al-based solid solution layer, and an Al2O3 thin film layer covering the surface of the alpha-Al-based solid solution layer. The compact structure of the alpha-Al-based solid solution can block the permeation of hydrogen atoms, enhance the interface between phase particles and a matrix, prolong the diffusion path of the hydrogen atoms in the material, increase the diffusion barrier and serve as a trap for capturing hydrogen, and the composite coating has the dual effects of capturing and blocking hydrogen, so that the hydrogen permeability is further reduced. When the coating is slightly damaged, the damaged surface can be oxidized again to form Al2O3, and the self-repairing capacity is achieved. The composite coating is prepared by adopting a braze coating method, and has the advantages of simple preparation method, low cost, capability of realizing industrial batch production and the like.

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 pipe 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 pipe 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 pipe 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. The α-Al-based solid solution layer has dispersedly distributed Al2O3 micro-nano particles and SiO2 micro-nano particles.

[0009] In a second aspect, the present application provides a preparation method of a hydrogen barrier coating, comprising the following steps: An Al-Si-based solder foil is covered on the surface of the substrate to obtain a workpiece to be soldered and coated; The workpiece to be soldered and coated is placed in a soldering and coating device into which a protective gas containing a certain amount of oxygen is introduced, and a soldering and coating heating curve is set 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; 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.

[0010] Further, the method further comprises polishing and sandblasting the surface of the substrate.

[0011] Further, the thickness of the Al-Si-based brazing 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; 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.

[0012] Further, the protection gas contains 0.1-0.5% oxygen by volume. 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.

[0013] Further, the brazing heating curve is as follows: In the preheating stage, the temperature is raised to 200-300℃ at a rate of 3-5℃ / min and held for 20-30min; In the heating stage, the temperature is raised to 500-550℃ at a rate of 5-10℃ / min and held for 10-15min; In the brazing holding stage, the temperature is raised to 600-650℃ at a rate of 5-10℃ / min and held for 10-20min; In the cooling stage, the temperature is reduced to 500-550℃ at a rate of 3-5℃ / min and cooled with the brazing device.

[0014] 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. 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.

[0015] Further, the brazing temperature is 600-650℃.

[0016] Further, the high-frequency electrical signal is 40-60 kHz.

[0017] 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.

[0018] The application has the following beneficial effects: The hydrogen barrier coating of the application comprises an alpha-Al-based solid solution layer on the substrate, Al2O3 micro-nano particles and SiO2 micro-nano particles 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 easily formed 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, so that 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 surface after the damage will be re-oxidized to form Al2O3, and the coating has self-repairing ability.

[0019] The application adopts the brazing coating technology (brazing coating technology) to prepare the hydrogen barrier coating, and passes the protective gas containing trace oxygen during the preparation process; secondly, in the aspect 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 the continuous thickening will increase the brittleness of the coating. In the brazing process, the 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 micro-cracks, uniform and stable composition, strong process controllability, easy adjustment of coating thickness, wide application range of substrate, and uniform coating on complex shape surfaces, etc. It provides a new idea for solving the technical pain points of the existing hydrogen barrier coating.

[0020] 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 present application. The objects and other advantages of the present application can be realized and obtained by the structure indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 A structural schematic diagram of the hydrogen barrier coating proposed in the embodiment of the present application is shown. Figure 2 A structural schematic diagram of the ultrasonic vibration system added to the box furnace proposed in the embodiment of the present application is shown. Figure 3 A brazing heating curve of the hydrogen barrier coating proposed in the embodiment of the present application is shown. Figure 4 An internal microstructure diagram of the composite coating is shown. Figure 2 In the embodiment, 1, box furnace; 2, storage plate; 3, workpiece to be brazed; 4, amplitude bar; 5, sealing flange; 6, vibration tool head; 7, transducer; 8, ultrasonic generator; 9, connecting rod; 10, transmission line. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] The present application proposes a hydrogen barrier coating, as shown in the figure. Figure 1 The hydrogen barrier coating includes 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. Al2O3 micro-nano particles and SiO2 micro-nano particles are dispersedly distributed in the α-Al-based solid solution layer as reinforcing phases.

[0025] The present application proposes a preparation method of the hydrogen barrier coating, and the method includes the following steps. S1: polishing the surface of a substrate to be prepared into a coating, and performing sand blasting treatment on the polished surface; S2: uniformly covering Al-Si-based brazing filler metal foils on the surface of the coating substrate to obtain a workpiece to be brazed; S3: placing the workpiece to be brazed in a brazing device into which a protective gas containing a certain amount of oxygen is introduced, setting a brazing heating curve, and brazing the workpiece to be brazed according to the brazing heating curve, wherein the brazing heating curve includes a preheating stage, a heating stage, a brazing holding stage and a cooling stage; S4: when the temperature of the heating stage is raised to the brazing temperature, the workpiece to be brazed is vibrated ultrasonically, the vibration is stopped when the holding time of the brazing ends and the temperature drops to below 550℃, 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.

[0026] In step S2, the thickness of the Al-Si-based filler foil strip is 0.05-0.2mm, wherein 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, and the melting point of the Al-Si-based filler foil strip is 577-610℃.

[0027] In step S3, the protection gas contains 0.1%-0.5% oxygen by volume; and the protection gas is one or more of inert gases, specifically including one or more of argon, nitrogen, and helium.

[0028] The brazing heating curve is as follows: In the preheating stage, the temperature is raised to 200-300℃ at a rate of 3-5℃ / min and held for 20-30min; In the heating stage, the temperature is raised to 500-550℃ at a rate of 5-10℃ / min and held for 10-15min; In the brazing holding stage, the temperature is raised to 600-650℃ at a rate of 5-10℃ / min and held for 10-20min; In the cooling stage, the temperature is lowered to 500-550℃ at a rate of 3-5℃ / min and cooled with the brazing device.

[0029] Based on the above method, the present application proposes a brazing device suitable for the preparation method, and the structure of the brazing device is as shown in Figure 2 The brazing 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 of the heating stage is raised to the brazing temperature, the ultrasonic generator 8 is started to emit a high-frequency electric signal, the high-frequency electric signal is converted into mechanical vibration by the transducer 7, 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 to be brazed 3 in the box furnace 1 to perform ultrasonic-assisted brazing.

[0030] In one embodiment of the present application, as Figure 2As shown, the brazing coating device comprises a box furnace 1, a placing plate 2 is arranged in the box furnace 1, and a workpiece 3 to be brazing coated is placed on the placing plate 2. An amplitude rod 4 penetrates through the inner wall of the box furnace 1 and is fixed and sealed through a sealing flange 5, the inner end of the amplitude rod 4 is connected with a vibrating tool head 6 and is fixed through an auxiliary connecting rod 9, the outer end of the amplitude rod 4 is connected with a transducer 7, the transducer 7 is connected with an external ultrasonic generator 8 through a transmission line 10, and finally the vibrating tool head 6 is vibrated to provide an ultrasonic vibration environment for the workpiece to be brazing coated in the box furnace 1. The amplitude rod 4 is connected with the outside through the sealing flange 5, and the vibrating tool head 6 is installed in the furnace through the connecting rod 9. In the figure, the inner part of the box furnace 1 is defined as a core working cavity by a dashed box, the placing plate 2 is fixedly arranged in the cavity, the workpiece to be brazing coated 3 is horizontally placed on the upper surface of the placing plate 2 in a detachable manner, the stable bearing and positioning of the workpiece are formed, and it is ensured that the workpiece to be brazing coated 3 is in a preset heating and vibration action area in the inner part of the box furnace 1.

[0031] In an embodiment of the present application, the amplitude rod 4 is a through structure, one end of the amplitude rod 4 extends into the inner part of the box furnace 1, and the other end of the amplitude rod 4 extends out of the box furnace 1; the through part of the amplitude rod 4 and the inner wall of the box furnace 1 is fixedly connected and sealed through the sealing flange 5, one end of the sealing flange 5 is welded or bolted with the inner wall of the box furnace 1, and the other end of the sealing flange 5 is matched with the amplitude rod 4 through a sealing element (not marked in the figure, which is a conventional sealing structure) to prevent the temperature field in the inner part of the box furnace 1 and the leakage of the protective gas.

[0032] In an embodiment of the present application, the vibrating tool head 6 is fixedly installed at the end of the amplitude rod 4 located in the inner part of the box furnace 1 in a threaded connection or welding manner; at the same time, the vibrating tool head 6 is fixedly connected with the amplitude rod 4 through the connecting rod 9, the two ends of the connecting rod 9 are bolted with the rod body of the amplitude rod 4 and the side wall of the vibrating tool head 6 respectively, the structural stability of the vibrating tool head 6 in the ultrasonic vibration process is ensured, and the lower end surface of the vibrating tool head 6 and the upper surface of the workpiece to be brazing coated 3 keep a preset gap or contact (which is set according to the brazing process requirement).

[0033] In an embodiment of the present application, the transducer 7 is fixedly installed at the end of the amplitude rod 4 extending out of the box furnace 1 in a flange connection or threaded connection manner, the vibration output end of the transducer 7 is coaxially connected with the input end of the amplitude rod 4, and the efficient transmission of ultrasonic vibration energy is ensured.

[0034] In one 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 to the input end of the transducer 7 through a transmission line 10, the two ends of the transmission line 10 being detachably connected (such as plug and socket cooperation) to the terminal of the ultrasonic generator 8 and the terminal of the transducer 7, 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 amplitude lever 4, the amplitude lever 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, finally providing the workpiece 3 to be brazed with the ultrasonic vibration environment required for the brazing process.

[0035] The preparation process of the hydrogen-blocking coating is exemplarily described below in combination with the embodiments.

[0036] Embodiment 1 The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen-blocking coating, and the specific steps are as follows: Step one, select an X65 pipeline steel plate as the substrate of the coating, and the size of the substrate is selected to be 100mmx100mmx10mm, polish the surface of the substrate, and perform sand blasting treatment on the polished surface; 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 material foil strip on the surface of the substrate, and place three layers to obtain the workpiece 3 to be brazed; 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; Step four, set a brazing heating curve, and start heating the box furnace 1, the brazing heating curve includes the following stages: (1) preheating stage: heat at a temperature increasing rate of 5℃ / min to 250℃ and keep for 30min; (2) heating stage: heat at a temperature increasing rate of 10℃ / min to 550℃ and keep for 15min; (3) brazing holding stage: heat at a temperature increasing rate of 10℃ / min to 650℃ and keep for 15min; (4) cooling stage: cool at a temperature decreasing rate of 5℃ / min to 550℃, and cool the brazing device.

[0037] Step five, when the temperature rises to the brazing temperature of 650℃, start the ultrasonic generator 8 to apply 50 kHz high-frequency ultrasonic vibration to the placement plate 2; when the brazing holding stage ends and the temperature drops to below 550℃, turn off the ultrasonic generator 8.

[0038] Step six, after the brazing workpiece 3 cools to room temperature with the box furnace 1, stop the argon gas, and take out the finished product.

[0039] Finally, an in-situ reinforced Al-based hydrogen barrier coating with a thickness of about 0.3 mm is obtained.

[0040] Example 2 The embodiment provides a preparation method of an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows: Step one, select an X65 pipeline steel plate as the substrate of the coating, and the size of the substrate is selected to be 100 mm x 100 mm x 10 mm; polish the surface of the substrate, and perform sand blasting treatment on the polished surface; Step two, select 0.1 mm 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 a brazing workpiece 3; Step three, place the brazing 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, but a trace amount of oxygen with a volume fraction of 0.5% is reserved; Step four, set the brazing heating curve, and start heating the box furnace 1, and the brazing heating curve includes the following stages: (1) preheating stage: heat to 250℃ at a heating rate of 5℃ / min and hold for 30 min; (2) heating stage: heat to 550℃ at a heating rate of 10℃ / min and hold for 15 min; (3) brazing holding stage: heat to 630℃ at a heating rate of 10℃ / min and hold for 15 min; (4) cooling stage: cool to 550℃ at a cooling rate of 5℃ / min, and cool the brazing device.

[0041] Step five, when the temperature rises to the brazing temperature of 630℃, start the ultrasonic generator 8 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℃, turn off the ultrasonic generator 8.

[0042] Step six, after the brazing workpiece 3 cools to room temperature with the box furnace 1, stop the argon gas, and take out the finished product.

[0043] Finally, an in-situ enhanced Al-based hydrogen barrier coating with a thickness of about 0.3 mm was obtained, and its internal microstructure is shown in the figure below. Figure 4 As shown in the figure, the α-Al solid solution forms the matrix of the coating, providing essential structural support. Dispersed Al2O3 and SiO2 micro-nanoparticles act as reinforcement phases, hindering hydrogen permeation while also improving the mechanical properties of the coating. This dispersed reinforcement phase effectively enhances its performance.

[0044] Example 3 This embodiment provides a method for preparing an in-situ enhanced Al-based hydrogen barrier coating, the specific steps of which are as follows: Step 1: Select X65 pipeline steel plate as the substrate for coating. The size of the substrate is 100mm×100mm×10mm. Grind and polish the surface of the substrate, and then sandblast the polished surface. Step 2: Select 0.1 mm thick Al-12Si (i.e., Si accounts for 12% by mass and Al accounts for 88% by mass) foil brazing material as the brazing coating raw material, and evenly cover the substrate surface with the Al-12Si brazing material foil in three layers to obtain a workpiece 3 to be brazed; Step 3: Place the workpiece 3 to be brazed and coated assembled in step 2 on the placement plate 2 in the box furnace 1 and fix it. Then, introduce ordinary industrial grade argon gas with a purity of 99.9% into the box furnace 1 for protection, but retain a trace amount of oxygen of 0.5% by volume. Step 4: Set the brazing coating heating curve and start heating the box furnace 1. The brazing coating heating curve includes the following stages: (1) Preheating stage: heating to 250°C at a heating rate of 5°C / min and keeping warm for 30 min; (2) Heating stage: heating to 550°C at a heating rate of 10°C / min and holding for 15 min; (3) Brazing and holding stage: heating to 610°C at a heating rate of 10°C / min and holding for 15 min; (4) Cooling stage: Cool down to 550℃ at a cooling rate of 5℃ / min and cool along with the brazing coating device.

[0045] Step 5: When the temperature rises to the brazing temperature of 610°C, start the ultrasonic generator 8 to apply 50kHz high-frequency ultrasonic vibration to the storage plate 2; when the brazing insulation stage ends and the temperature drops below 550°C, turn off the ultrasonic generator 8.

[0046] Step 6: After the brazing-coated workpiece 3 is cooled to room temperature along with the box furnace 1, the argon gas flow is stopped and the finished workpiece is taken out.

[0047] Finally, an in-situ enhanced Al-based hydrogen barrier composite coating with a thickness of about 0.3 mm was obtained.

[0048] Comparative Example 1 The X65 pipeline steel plate was selected as the comparative example.

[0049] Comparative Example 2 The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen barrier coating, and the specific steps are as follows: Step one, select the X65 pipeline steel plate as the coating matrix, the size of the matrix is selected to be 100mm*100mm*10mm, polish the surface of the matrix, and perform sand blasting treatment on the polished surface; Step two, select 0.1mm-thick Al-10Si foil strip filler as the filler coating raw material, uniformly cover the Al-10Si filler foil strip on the surface of the matrix, and place 3 layers to obtain a filler coating workpiece 3; Step three, place the assembled filler coating workpiece 3 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 with a volume fraction of 0.5% is reserved; Step four, set a filler coating heating curve, and start heating the box furnace 1, the filler coating heating curve comprises the following stages: (1) preheating stage: heating at a temperature increasing rate of 5°C / min to 250°C and keeping for 30min; (2) temperature increasing stage: heating at a temperature increasing rate of 10°C / min to 550°C and keeping for 15min; (3) filler coating keeping stage: heating at a temperature increasing rate of 10°C / min to 630°C and keeping for 15min; (4) cooling stage: cooling at a temperature decreasing rate of 5°C / min to 550°C, and cooling the filler coating device.

[0050] Step five, after the filler coating workpiece 3 is cooled to room temperature along with the box furnace 1, stop the argon gas, and take out the finished product.

[0051] Finally, because the protective gas introduced contains oxygen, an oxygen film is formed during the melting of the filler, which hinders the combination of the liquid filler and the steel matrix, and an integrated Al-based coating is not obtained.

[0052] Comparative Example 3 The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen barrier coating, and the specific steps are as follows: Step one, select the X65 pipeline steel plate as the coating matrix, the size of the matrix is selected to be 100mm*100mm*10mm, polish the surface of the matrix, and perform sand blasting treatment on the polished surface; Step two, select 0.1 mm thick Al-10Si foil strip filler as the brazing coating raw material, evenly cover Al-10Si filler foil on the surface of the substrate, place 3 layers, get the brazing coating workpiece 3; Step three, fix the assembled brazing coating workpiece 3 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; Step four, set the brazing coating heating curve, start heating the box furnace 1, and the brazing coating heating curve includes the following stages: (1) preheating stage: heating at a rate of 5℃ / min to 250℃ for 30min; (2) heating stage: heating at a rate of 10℃ / min to 550℃ for 15min; (3) brazing coating holding stage: heating at a rate of 10℃ / min to 630℃ for 15min; (4) cooling stage: cooling at a rate of 5℃ / min to 550℃, and cooling the brazing coating device.

[0053] Step five, after the brazing coating workpiece 3 cools to room temperature with the box furnace 1, stop the argon gas, and take out the finished product.

[0054] Finally, an Al-based hydrogen-blocking coating with a thickness of about 0.3mm is obtained.

[0055] Comparative example 4 The embodiment provides a preparation method of an in-situ enhanced Al-based hydrogen-blocking coating, and the specific steps are as follows: Step one, select X65 pipeline steel plate as the substrate, and the size of the substrate is selected to be 100mmx100mmx10mm, polish the surface of the substrate, and perform sand blasting treatment on the polished surface; Step two, select 0.1 mm thick Al-20Si foil strip filler as the brazing coating raw material, evenly cover Al-20Si filler foil on the surface of the substrate, place 3 layers, get the brazing coating workpiece 3; Step three, fix the assembled brazing coating workpiece 3 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 retain 0.5% of trace oxygen; Step four, set the brazing coating heating curve, start heating the box furnace 1, and the brazing coating heating curve includes the following stages: (1) preheating stage: heating at a rate of 5℃ / min to 250℃ for 30min; (2) heating stage: heating at a rate of 10℃ / min to 550℃ for 15min; (3) brazing and holding stage: heating at a rate of 10 ℃ / min to 700 ℃ and holding for 15 min; (4) cooling stage: cooling at a rate of 5 ℃ / min to 550 ℃ and cooling with the brazing device.

[0056] Step five, when the temperature rises to the brazing temperature 700 ℃, start the ultrasonic generator 8 to apply 50 kHz 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.

[0057] 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.

[0058] Finally, an in-situ reinforced Al-based hydrogen barrier composite coating with a thickness of about 0.3 mm is obtained. Due to the excessive Si content in the brazing filler metal, there are coarse granular Si elements in the solidified alloy matrix, and microcracks exist in the coating, resulting in low bonding strength with the matrix.

[0059] Comparative Example 5 The embodiment provides a preparation method of an in-situ reinforced Al-based hydrogen barrier coating, and the specific steps are as follows: Step one, select an X65 pipeline steel plate as the matrix, and the size of the matrix is selected to be 100 mm×100 mm×10 mm. The surface of the matrix to be prepared with the coating is polished and sandblasted; Step two, select a 0.1 mm thick pure Al foil as the brazing filler metal, uniformly cover the pure Al foil on the surface of the matrix, and place 3 layers to obtain a brazing workpiece 3; Step three, place the brazing 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 for protection, but a trace amount of oxygen gas with a volume fraction of 0.5% is reserved; Step four, set a brazing heating curve, and start heating the box furnace 1. The brazing heating curve comprises the following stages: (1) preheating stage: heating at a rate of 5 ℃ / min to 250 ℃ and holding for 30 min; (2) heating stage: heating at a rate of 10 ℃ / min to 550 ℃ and holding for 15 min; (3) brazing and holding stage: heating at a rate of 10 ℃ / min to 700 ℃ and holding for 15 min; (4) cooling stage: cooling at a rate of 5 ℃ / min to 550 ℃ and cooling with the furnace.

[0060] Step five, when the temperature rises to the brazing temperature 700 ℃, start the ultrasonic generator 8 to apply 50 kHz 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.

[0061] Step six, after the brazing coating workpiece 3 with the box body furnace 1 cooled to room temperature, stop the argon, take out the finished piece.

[0062] The final Al-based coating has a thickness of about 0.3 mm. Since the brazing filler metal is pure Al, the amount of Al2O3 generated in the solidified composite coating is small, and the hydrogen barrier effect of the coating is not good.

[0063] Test Example 1 The bonding strength between the coating and the substrate was tested 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 based on the maximum thrust force and the contact area (unit: MPa). The hydrogen permeation reduction factor of the hydrogen barrier coating was tested by a hydrogen permeation method. The test results of the hydrogen barrier coating bonding strength and the hydrogen permeation reduction factor in Examples 1-3 and Comparative Examples are shown in Table 1: Table 1

[0064] In the table, " / " means that this test was not performed. As can be seen from Table 1, Comparative Example 1 is the original X65 pipeline steel (without coating), and its 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.

[0065] Examples 1-3, Comparative Examples 2 / 4 / 5 all retain 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 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), 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. 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 bonding).

[0066] Example 1-3 all applied 50 kHz ultrasonic vibration in the brazing coating stage (610-650℃), and the final coating bonding strength reached above 86.98 MPa; Comparative Example 2 and Example 2 were almost identical in process (same Al-10Si filler metal, same protective gas, same 630℃ brazing coating temperature), only lacking the ultrasonic vibration step, and the result failed to obtain a complete coating (no bonding strength and PRF data) due to the formation of an oxide film when the filler metal melted, which hindered the bonding with the substrate. This can show that ultrasonic vibration can effectively break the oxide film at the interface between the filler metal and the substrate, ensuring the infiltration bonding of the liquid filler metal and the substrate, which is the core guarantee for coating formation.

[0067] As can be seen from Comparative Examples 4 and 5 and Example 2, when the filler metal is pure Al, although the bonding strength reaches 89.43 MPa (close to the example), the amount of Al2O3 generated after solidification is extremely small (the core phase for hydrogen blocking is insufficient), resulting in PRF of only 280, and the hydrogen blocking 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, and the bonding strength drops sharply to 53.67 MPa (only 56.8% of Example 2), and the PRF is only 350 (only 5% of Example 2), and the structural integrity and performance are both damaged.

[0068] 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 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 by, The hydrogen barrier coating comprises 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 is dispersed with Al2O3 micro-nano particles and SiO2 micro-nano particles.

2. A method for producing a hydrogen barrier coating, characterized by, The method for preparing the hydrogen barrier coating of claim 1 comprises the following steps: covering the Al-Si-based filler metal foil on the surface of the substrate to obtain a workpiece to be brazed; placing the workpiece to be brazed in a brazing device with a protective gas containing a certain amount of oxygen, setting a brazing heating curve to perform brazing, the brazing heating curve comprising a preheating stage, a temperature rising stage, a brazing holding stage and a cooling stage; when the temperature of the temperature rising stage rises to the brazing temperature, ultrasonic vibration is applied to the workpiece to be brazed, the ultrasonic vibration is stopped when the brazing holding stage ends and the temperature drops to below 550℃, and the brazing device is cooled to room temperature after the workpiece to be brazed is cooled, and the protective gas is stopped to obtain the hydrogen barrier coating.

3. The method of claim 2, wherein the hydrogen barrier coating is prepared by a method comprising: The method further comprises polishing and sandblasting the surface of the coating substrate.

4. The method of claim 3, wherein the hydrogen barrier coating is prepared by a method comprising: The thickness of the Al-Si-based filler metal foil is 0.05-0.2mm; wherein 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 Cu 0.5%-2%, Mg 0%-0.5% and Fe 0-0.8% in any combination.

5. The method of claim 2, wherein the hydrogen barrier coating is prepared by a method comprising: The protective gas contains 0.1%-0.5% oxygen by volume; The protective gas is selected from one or more of inert gases in any combination.

6. The method of claim 2, wherein the hydrogen barrier coating is prepared by a method comprising: The brazing heating curve is as follows: in the preheating stage, heating at a temperature rising rate of 3-5℃ / min to 200-300℃ for 20-30min; in the temperature rising stage, heating at a temperature rising rate of 5-10℃ / min to 500-550℃ for 10-15min; in the brazing holding stage, heating at a temperature rising rate of 5-10℃ / min to 600-650℃ for 10-20min; in the cooling stage, cooling at a temperature rising rate of 3-5℃ / min to 500-550℃, and cooling with the brazing device.

7. The method of claim 2, wherein the hydrogen barrier coating is prepared by a method comprising: The brazing device is a box furnace with an ultrasonic vibration assembly; wherein the ultrasonic vibration assembly comprises an ultrasonic generator, a transducer, an amplitude transformer and a vibration tool head. When the temperature of the temperature rising stage rises 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 to perform ultrasonic assisted brazing.

8. The method of claim 3, wherein the hydrogen barrier coating is prepared by a method comprising: The brazing temperature is 600-650℃.

9. The method of claim 7, wherein the hydrogen barrier coating is prepared by a method comprising: The high-frequency electric signal is 40-60kHz.

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

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