TiCN gradient structure hydrogen barrier coating and preparation method thereof

Abstract

The application discloses a TiCN gradient structure hydrogen barrier coating and a preparation method thereof. After a substrate is pretreated, the substrate is placed in a vacuum reaction chamber, mixed gas of hydrogen and argon is introduced, the substrate and the reaction chamber cavity are heated to a deposition temperature and then are kept warm; a carbon source, a nitrogen source, a titanium source and an auxiliary gas are introduced to perform chemical vapor deposition on the surface of the substrate, the deposition process is divided into two stages, the flow of the auxiliary gas carrying the titanium source is constant, the flow of the carbon source is greater than that of the nitrogen source in the first deposition stage, and the flow of the nitrogen source is greater than that of the carbon source in the second deposition stage, so that a deposition coating with a gradient structure is obtained; the introduction of the carbon source, the titanium source and the auxiliary gas is stopped, the deposition coating is cooled, the introduction of the nitrogen source is stopped during the cooling process, and then the cooling is performed to room temperature, so that the TiCN gradient structure hydrogen barrier coating is obtained. The coating component change and the grain size can be effectively controlled, the coating has high density and reduced defects, the bonding force between the coating and the metal substrate is strong, and therefore the hydrogen barrier performance of the substrate is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen barrier coatings, and relates to a TiCN gradient structure hydrogen barrier coating and its preparation method. Background Technology

[0002] Hydrogen energy boasts advantages such as being pollution-free, widely available, having a high calorific value, and being renewable and recyclable, making it the safest, cleanest, and highest-calorific-value gaseous fuel of the future. Metallic materials are currently the primary materials for hydrogen storage and transportation systems, with high-pressure hydrogen storage and transportation being the main methods. However, high-pressure hydrogen environments easily lead to a series of hydrogen embrittlement problems in metallic materials, including reduced plasticity, accelerated fatigue crack propagation, and even failure. Effectively preventing hydrogen penetration into the surface and interior of metallic materials is a significant challenge currently facing the safety of high-pressure hydrogen systems.

[0003] Hydrogen-barrier coatings are an effective way to solve the hydrogen embrittlement problem in metal hydrogen storage systems. By preparing hydrogen-barrier coatings on the surface of metal materials, hydrogen permeation into the material can be prevented or delayed, thereby preventing and reducing hydrogen embrittlement. Studies have shown that coatings with hydrogen-barrier / hydrogen-storage functions have good hydrogen-barrier performance; however, their performance is often limited by factors such as coating grain size, density, number of defects, and adhesion between the coating and the metal substrate. Existing methods for preparing hydrogen-barrier coatings, such as plasma spraying, embedding aluminizing, and sol-gel methods, suffer from a series of problems, including low coating density, numerous defects, and uneven particle size distribution, which significantly limit the hydrogen-barrier performance of the prepared coatings.

[0004] Therefore, in response to the hydrogen embrittlement problem faced by current high-pressure metal hydrogen storage systems, there is an urgent need in this field to develop a coating with high density, few defects, and good hydrogen barrier properties, so as to overcome the shortcomings of existing hydrogen barrier coatings such as low density, many defects, and weak hydrogen barrier properties, and improve the safety of high-pressure metal hydrogen storage systems. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the prior art by providing a TiCN gradient structure hydrogen barrier coating and its preparation method, which solves the problems of low density, many defects, and weak hydrogen barrier performance of existing hydrogen barrier coatings.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a TiCN gradient structure hydrogen barrier coating includes:

[0008] After pretreatment of the substrate, it is placed in a vacuum reaction chamber, and a mixture of hydrogen and argon gas is introduced to heat the substrate and the reaction chamber to the deposition temperature and then keep it warm.

[0009] Carbon source, nitrogen source, titanium source and auxiliary gas are introduced to perform chemical vapor deposition on the substrate surface. The deposition process is divided into two stages. The flow rate of the auxiliary gas carrying the titanium source is constant. In the first deposition stage, the flow rate of the carbon source is greater than that of the nitrogen source. In the second deposition stage, the flow rate of the nitrogen source is greater than that of the carbon source, resulting in a gradient structure deposition coating.

[0010] The carbon source, titanium source, and auxiliary gas were stopped, and the deposited coating was cooled. During the cooling process, the nitrogen source was stopped, and then the coating was cooled to room temperature to obtain the TiCN gradient structure hydrogen barrier coating.

[0011] Furthermore, during the chemical vapor deposition process, the vacuum degree of the vacuum reaction chamber is 0.02–0.05 MPa, and the flow rate of the mixed hydrogen and argon gas is 200–500 sccm.

[0012] Furthermore, the heating process is as follows: heating to 500°C at a rate of 3-5°C / min, holding at 500°C for 1 hour, and then heating to the deposition temperature at a rate of 8-10°C / min, wherein the deposition temperature is 650-850°C.

[0013] Furthermore, in the chemical vapor deposition process, the deposition time is 150–360 min, the flow rate of the carbon source is 200–400 sccm, the flow rate of the nitrogen source is 100–500 sccm, and the flow rate of the auxiliary gas is 200–500 sccm.

[0014] Furthermore, the substrate is one or more of carbon steel, heat-resistant steel, hard alloy, and corrosion-resistant alloy;

[0015] The titanium source is one or more of the following: titanium tetrachloride, titanium trichloride, titanium dichloride, titanium chloride, and titanium powder;

[0016] The auxiliary gas is one or more of argon, nitrogen, helium, and hydrogen;

[0017] The carbon source is one or more of methane, ethane, butane, and propylene;

[0018] The nitrogen source is one or more of nitric oxide, nitrogen dioxide, nitrogen, and ammonia.

[0019] Furthermore, the cooling process is as follows: the nitrogen source flow rate is reduced to 100-150 sccm, and the temperature is reduced to 400-500℃;

[0020] When the temperature drops to 400-500℃, the nitrogen source flow rate is reduced to 50-100 sccm, and the temperature continues to drop.

[0021] When the temperature drops to 50–150°C, stop the nitrogen source supply and then cool to room temperature.

[0022] A TiCN gradient structure hydrogen barrier coating prepared by the aforementioned method, wherein the content of Ti, C, and N elements in the coating structure varies in a gradient from the surface to the interior, the inner layer of the coating is a TiC-rich phase, and the outer layer of the coating is a TiN-rich phase.

[0023] Furthermore, the coating has a thickness of 2–8 μm, the TiC-rich phase layer has a thickness of 0.3–2 μm and accounts for 60–80%, and the TiN-rich phase layer has a thickness of 1–5 μm and accounts for 60–85%.

[0024] Furthermore, the coating contains TiCN grains, which have a blocky structure, are interlocked, and have a grain size of 1–3 μm.

[0025] Furthermore, the hydrogen permeation reduction factor of the coating at 300°C is 500–800.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides a TiCN gradient structure hydrogen barrier coating. A carbon, nitrogen, and titanium source are deposited on the substrate surface using chemical vapor deposition (CVD). Through two stages of CVD, the Ti, C, and N element content in the resulting coating structure varies gradient from the surface to the interior, forming a gradient structure composed of an outer TiN-rich phase and an inner TiC-rich phase. This gradient structure blocks hydrogen atom penetration and captures and stores a small number of hydrogen atoms that diffuse through the coating surface into the coating interior, thus achieving hydrogen barrier function. The outer surface TiN-rich phase primarily blocks hydrogen penetration, while the inner TiC-rich phase further captures the small number of hydrogen atoms that diffuse through the surface TiN-rich phase into the coating interior, creating a dual effect of blocking and capturing, thereby significantly enhancing the coating's hydrogen barrier capability. Furthermore, the TiCN gradient structure hydrogen barrier coating prepared by this invention can effectively control the coating composition and grain size, allowing for continuous design of the coating composition. The coating has high density and reduces defects, and exhibits strong adhesion between the coating and the metal substrate, thereby significantly improving the hydrogen barrier performance of the substrate.

[0028] This invention provides a method for preparing a TiCN gradient structure hydrogen barrier coating, which features low production cost, simple process, and strong controllability, making it suitable for industrial production. Furthermore, it has minimal impact on the dimensional accuracy of the substrate and offers good adaptability to substrate shape, enabling its application in new energy, nuclear power, hydrogen storage and transportation, and other fields. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the hydrogen barrier coating with a TiCN gradient structure on a 316L metal surface prepared according to Example 1 of the present invention.

[0031] Figure 2 The image shows the XRD pattern of the hydrogen barrier coating with a TiCN gradient structure on the surface of a 316L metal prepared according to Example 1 of the present invention.

[0032] Figure 3 SEM image of the hydrogen barrier coating with TiCN gradient structure on the surface of 316L metal prepared in Example 1 of the present invention.

[0033] Figure 4 The image shows a cross-sectional SEM image of the hydrogen barrier coating with a TiCN gradient structure on a 316L metal surface prepared according to Example 1 of the present invention.

[0034] Figure 5 The image shows a cross-sectional EDS test pattern of the hydrogen barrier coating with a TiCN gradient structure on a 316L metal surface prepared according to Example 1 of the present invention. Detailed Implementation

[0035] This invention provides a method for preparing a TiCN gradient structure hydrogen barrier coating, comprising the following steps:

[0036] After pretreatment of the substrate, it is placed in a reaction chamber with a vacuum of 0.02 to 0.05 MPa, and a mixed gas of hydrogen and argon is introduced at 200 to 500 sccm. The substrate and the reaction chamber are heated to the deposition temperature of 650 to 850°C and then kept at that temperature.

[0037] Carbon source, nitrogen source, titanium source and auxiliary gas are introduced to perform chemical vapor deposition on the substrate surface. The deposition process is divided into two stages. The flow rate of the auxiliary gas carrying the titanium source is constant. In the first deposition stage, the flow rate of the carbon source is greater than that of the nitrogen source. In the second deposition stage, the flow rate of the nitrogen source is greater than that of the carbon source, resulting in a gradient structure deposition coating.

[0038] Stop the supply of carbon source, titanium source and auxiliary gas, and cool the deposited coating. During the cooling process, the nitrogen source flow rate is reduced to 100-150 sccm and the temperature is reduced to 400-500℃.

[0039] When the temperature drops to 400-500℃, the nitrogen source flow rate is reduced to 50-100 sccm, and the temperature continues to drop.

[0040] When the temperature drops to 50–150°C, the nitrogen source is stopped, and then the temperature is cooled to room temperature to obtain the TiCN gradient structure hydrogen barrier coating.

[0041] Furthermore, the base material is one or more of carbon steel, heat-resistant steel, hard alloy, and corrosion-resistant alloy.

[0042] The titanium source is one or more of titanium tetrachloride, titanium trichloride, titanium dichloride, titanium chloride, and titanium powder, and the titanium source is introduced by means of an auxiliary gas.

[0043] The auxiliary gas is one or more of argon, nitrogen, helium and hydrogen, the flow rate of the auxiliary gas is 200-500 sccm, and the purity of the auxiliary gas is 99.99%.

[0044] The carbon source is one or more of methane, ethane, butane, and propylene, and the carbon source is a gas source with a flow rate of 200–400 sccm.

[0045] The nitrogen source is one or more of nitric oxide, nitrogen dioxide, nitrogen gas, and ammonia gas, and the nitrogen source is a gas source with a flow rate of 100 to 500 sccm.

[0046] Furthermore, the heating process is as follows: heat to 500°C at a rate of 3-5°C / min, hold at 500°C for 1 hour, and then heat to the deposition temperature of 650-850°C at a rate of 8-10°C / min.

[0047] Furthermore, the deposition time is 150–360 min, preferably 200–330 min, and even more preferably 220–240 min.

[0048] The TiCN gradient structure hydrogen barrier coating prepared by the above method has a gradient of Ti, C and N element content from the surface to the interior. The inner layer of the coating is a TiC-rich phase and the outer layer is a TiN-rich phase.

[0049] The coating has a thickness of 2–8 μm, preferably 4–6 μm; the TiC-rich phase layer has a thickness of 0.3–2 μm, preferably 0.5–1.2 μm, and accounts for 60–80% of the total thickness; and the TiN-rich phase layer has a thickness of 1–5 μm, preferably 2–3 μm, and accounts for 60–85% of the total thickness.

[0050] The coating contains TiCN grains, which have a blocky structure and are interlocked.

[0051] The TiCN grains have a grain size of 1–3 μm, preferably 1–1.3 μm.

[0052] The coating has a hydrogen permeation reduction factor of 500-800 at 300°C, preferably 600-650.

[0053] The present invention also discloses an article comprising the TiCN gradient structure hydrogen barrier coating described above, or the article being composed of the TiCN gradient structure hydrogen barrier coating described above, or the article comprising a substrate and a TiCN gradient structure hydrogen barrier coating as described above, composited on the surface of the substrate.

[0054] The coating is chemically bonded to the substrate.

[0055] The present invention will be further described in detail below with reference to specific embodiments:

[0056] Example 1:

[0057] The 316L metal substrate with dimensions of 100mm*20mm*5mm was polished to remove impurities, sandblasted with white corundum sand, polished, and then ultrasonically cleaned with alcohol. After cleaning, the substrate was placed in an oven and dried at 95℃ for 6 hours before being placed in a CVD device.

[0058] A two-stage vacuum pump group was used to pre-evacuate the CVD unit to 1000 volts. -1 Pa, simultaneously introducing hydrogen and argon gas, with a hydrogen flow rate of 200 sccm and an argon flow rate of 100 sccm. The furnace heating program is started, with the heating rate set to 5℃ / min and the deposition temperature set to 820℃.

[0059] TiCN gradient structure coatings were prepared by chemical vapor deposition (CVD). The specific steps were as follows: the CVD heating apparatus was used to heat the material to 500℃ at a rate of 5℃ / min and hold for 1 hour, then heated to 820℃ at a rate of 10℃ / min. Following this, the coating deposition process commenced, introducing titanium tetrachloride, methane, nitrogen, and argon gases. The deposition time was 240 minutes. The deposition process was divided into two stages: from 0 to 60 minutes, the flow rates of argon carrying titanium tetrachloride were 300 sccm, nitrogen 200 sccm, and methane 400 sccm; from 60 to 240 minutes, the flow rates of argon carrying titanium tetrachloride were 300 sccm, nitrogen 400 sccm, and methane 200 sccm. The total vacuum pressure during the CVD reaction was 0.04 MPa.

[0060] After deposition, the CVD unit entered cooling mode, stopping the flow of titanium tetrachloride, methane, and argon. The nitrogen flow rate was reduced to 100 sccm, and the cooling rate was 10 °C / min. The temperature was reduced to 400 °C, and then the nitrogen flow rate was reduced to 50 sccm. When the temperature dropped to 50 °C, the nitrogen flow was stopped, and then the unit was cooled to room temperature to obtain a TiCN gradient structure hydrogen barrier coating composited on the 316L metal surface.

[0061] Example 2:

[0062] The method is the same as in Example 1, except that the coating deposition temperature is 800°C.

[0063] Example 3:

[0064] The method is the same as in Example 1, except that during the chemical vapor deposition process, the nitrogen flow rate is 150 sccm from 0 to 60 min and 350 sccm from 60 to 240 min.

[0065] Example 4:

[0066] The method is the same as in Example 1, except that the carbon source is propylene.

[0067] Example 5:

[0068] The method is the same as in Example 1, except that the titanium source is titanium trichloride.

[0069] Example 6:

[0070] The method is the same as in Example 1, except that: the CVD device is first pre-evacuated to 0.05 Pa, and hydrogen and argon are introduced at the same time. The flow rate of hydrogen is 150 sccm and the flow rate of argon is 300 sccm. The total vacuum pressure during the chemical vapor deposition reaction is 0.02 MPa.

[0071] Example 7:

[0072] The method is the same as in Example 1, except that: during the chemical vapor deposition process, the deposition temperature is 660℃, the deposition time is 180 min, and a carbon source of tetrabutyl titanate, hydrogen, ammonia, and ethane and propylene is introduced. From 0 to 40 min, the flow rate of hydrogen carrying tetrabutyl titanate is 400 sccm, the flow rate of ammonia is 100 sccm, and the flow rate of the mixed gas of ethane and propylene is 300 sccm; from 40 to 180 min, the flow rate of hydrogen carrying tetrabutyl titanate is 400 sccm, the flow rate of ammonia is 500 sccm, and the flow rate of the mixed gas of ethane and propylene is 200 sccm.

[0073] Example 8:

[0074] The method is the same as in Example 1, except that: during the chemical vapor deposition process, the deposition temperature is 740℃, the deposition time is 340 min, and titanium powder, helium, nitric oxide and butene are introduced. From 0 to 150 min, the flow rate of helium carrying titanium powder is 500 sccm, the flow rate of nitric oxide is 150 sccm, and the flow rate of the mixed gas carrying butene is 400 sccm; from 150 to 340 min, the flow rate of helium carrying titanium powder is 500 sccm, the flow rate of nitric oxide is 450 sccm, and the flow rate of the mixed gas carrying butene is 250 sccm.

[0075] Example 9:

[0076] The method is the same as in Example 1, except that during the heating process, the CVD heating device heats the temperature to 500°C at 4°C / min and holds it for 1 hour, then heats it to 790°C at 8°C / min.

[0077] Example 10:

[0078] The method is the same as in Example 1, except that after deposition, the CVD device enters the cooling mode, stops the supply of titanium tetrachloride, methane and argon, reduces the nitrogen flow rate to 140 sccm, and cools at a rate of 10 °C / min until it reaches 460 °C. Then the nitrogen flow rate is reduced to 70 sccm. When the temperature drops to 100 °C, the nitrogen supply is stopped, and then the device is cooled to room temperature to obtain a TiCN gradient structure hydrogen barrier coating composited on the 316L metal surface.

[0079] The hydrogen-barrier coatings with a TiCN gradient structure composite on the 316L metal surface obtained in Examples 1-5 were tested by XRD, SEM, and EDS. The test results are as follows: Figures 1-5 As shown.

[0080] High-temperature hydrogen permeation tests were conducted on the TiCN gradient structure hydrogen barrier coatings obtained in Examples 1-5 on the 316L metal surface. Before the tests, leak detectors were used to check the welded samples to ensure the accuracy of the test results. A two-stage vacuum pump group was used to evacuate the test pipeline, high-pressure chamber, and low-pressure chamber to ensure that the vacuum degree of the low-pressure chamber was 10. -6 The sample was degassed for 12 hours. Resistance heating was used to heat the sample to 300℃ and maintain this temperature, followed by the introduction of high-purity deuterium gas at a pressure of 100 kPa. The change in deuterium ion flow permeating the coating over time was detected using a quadruple mass spectrometer, thus obtaining the deuterium permeability at different times. Combined with the deuterium permeability of the test sample at the same temperature, the PRF value of the composite hydrogen barrier coating at different temperatures could be obtained.

[0081] The test results are as follows:

[0082] like Figure 1As shown, the TiCN gradient structure hydrogen barrier coating prepared in Example 1 of the present invention consists of an outer TiN-rich layer and an inner TiC-rich layer.

[0083] like Figure 2 As shown, the TiCN gradient structure hydrogen barrier coating prepared in Example 1 of the present invention is composed of TiN, TiC and a small amount of Fe phase, and the crystal structure is face-centered cubic. The preferred orientation of the TiCN gradient structure hydrogen barrier coating grain growth is (111) plane.

[0084] like Figure 3 As shown, the TiCN gradient structure hydrogen barrier coating obtained in Example 1 of the present invention has a dense and uniform surface. The coating is composed of TiCN grains with a blocky shape, which overlap each other and have a grain size of 1 to 1.3 μm.

[0085] like Figure 4 As shown, the TiCN gradient structure hydrogen barrier coating prepared in Example 1 of the present invention is tightly bonded to the substrate surface, without defects such as microcracks and micropores, and the coating thickness is 4 to 5.5 μm.

[0086] like Figure 5 As shown, in the TiCN gradient structure hydrogen barrier coating prepared in Example 1 of this invention, the Ti, C, and N elements exhibit a gradient change from the outer surface to the interior. The EDS test direction was from the coating-substrate interface to the outer surface of the coating, and the EDS test coating thickness was approximately 4.9 μm. The thickness of the TiC-rich phase was approximately 1 μm, while the remaining thickness of the coating was composed of the TiN-rich phase.

[0087] The PRF value of the TiCN gradient structure hydrogen barrier coating prepared in Example 1 is 636.

[0088] The TiCN gradient structure hydrogen barrier coating prepared in Example 2 has a dense and uniform surface, and the coating grains are micron-sized and blocky; the particle size of the blocky grains is 1.0 to 1.1 μm; the PRF value of the coating is 585.

[0089] The TiCN gradient structure hydrogen barrier coating prepared in Example 3 has a dense and uniform surface, and the coating grains are micron-sized and blocky; the particle size of the blocky grains is 0.9-1.1 μm; the PRF value of the coating is 577.

[0090] The TiCN gradient structure hydrogen barrier coating prepared in Example 4 has a dense and uniform surface, and the coating grains are micron-sized and blocky; the particle size of the blocky grains is 1.0 to 1.1 μm; the PRF value of the coating is 583.

[0091] The TiCN gradient structure hydrogen barrier coating prepared in Example 5 has a dense and uniform surface, and the coating grains show a micron-sized and bulk structure; the particle size of the bulk grains is 1.0 to 1.1 μm; the PRF value of the coating is 582.

[0092] Comparative Examples 1-4:

[0093] The TiCN crystal coatings described in Comparative Examples 1 to 4 were prepared according to the method of Example 1, except that the parameters in the coating preparation process were changed as shown in Table 2. The grain morphology and grain size of the coatings were characterized, and the hydrogen barrier performance of the coatings was measured according to the same high-temperature hydrogen permeation performance test method as in Example 1.

[0094] Table 2. Characterization and performance testing of TiCN crystal coatings on 316L metal surfaces prepared in Comparative Examples 1–4.

[0095]

[0096]

[0097] The grain morphology, grain size, and hydrogen barrier performance of the coatings prepared in Examples 1-5 and Comparative Examples 1-4 were compared. Table 2 shows that the grain size of the TiCN gradient structure hydrogen barrier coatings prepared in Examples 1-5 on the 316L metal surface is significantly larger than that of the TiCN crystal coatings prepared in Comparative Examples 1-4. Furthermore, the PRF values ​​of the TiCN gradient structure hydrogen barrier coatings prepared in Examples 1-5 on the 316L metal surface are significantly higher than those of the TiCN crystal coatings prepared in Comparative Examples 1-4. Therefore, compared with Comparative Examples 1-4, the TiCN gradient structure hydrogen barrier coating prepared in this invention on the 316L metal surface exhibits superior hydrogen barrier performance.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a TiCN gradient structure hydrogen-barrier coating, characterized in that, include: After pretreatment, the substrate is placed in a vacuum reaction chamber, and a mixture of hydrogen and argon gas is introduced to heat the substrate and the reaction chamber to the deposition temperature and then keep it warm. Carbon source, nitrogen source, titanium source and auxiliary gas are introduced to perform chemical vapor deposition on the substrate surface. The deposition process is divided into two stages. The flow rate of the auxiliary gas carrying the titanium source is constant. In the first deposition stage, the flow rate of the carbon source is greater than that of the nitrogen source. In the second deposition stage, the flow rate of the nitrogen source is greater than that of the carbon source, resulting in a gradient structure deposition coating. The carbon source, titanium source and auxiliary gas were stopped, and the deposited coating was cooled. During the cooling process, the nitrogen source was stopped, and then the coating was cooled to room temperature to obtain the TiCN gradient structure hydrogen barrier coating. In the chemical vapor deposition process, the deposition time is 150~360 min, the flow rate of the carbon source is 200~400 sccm, the flow rate of the nitrogen source is 100~500 sccm, and the flow rate of the auxiliary gas is 200~500 sccm. The cooling process is as follows: the nitrogen source flow rate is reduced to 100~150 sccm, and the temperature is reduced to 400~500℃; When the temperature drops to 400~500℃, the nitrogen source flow rate is reduced to 50~100 sccm, and the temperature continues to drop; When the temperature drops to 50~150℃, stop the nitrogen source and then cool to room temperature.

2. The method for preparing a TiCN gradient structure hydrogen barrier coating according to claim 1, characterized in that, During the chemical vapor deposition process, the vacuum degree of the vacuum reaction chamber is 0.02~0.05MPa, and the flow rate of the mixed hydrogen and argon gas is 200~500sccm.

3. The method for preparing a TiCN gradient structure hydrogen barrier coating according to claim 1, characterized in that, The heating process is as follows: heating to 500°C at a rate of 3~5°C / min, holding at 500°C for 1 hour, and then heating to the deposition temperature at a rate of 8~10°C / min, wherein the deposition temperature is 650~850°C.

4. The method for preparing a TiCN gradient structure hydrogen barrier coating according to claim 1, characterized in that, The substrate is one or more of carbon steel, heat-resistant steel, hard alloy, and corrosion-resistant alloy; The titanium source is one or more of the following: titanium tetrachloride, titanium trichloride, titanium dichloride, titanium chloride, and titanium powder; The auxiliary gas is one or more of argon, nitrogen, helium, and hydrogen; The carbon source is one or more of methane, ethane, butane, and propylene; The nitrogen source is one or more of nitric oxide, nitrogen dioxide, nitrogen, and ammonia.

5. A TiCN gradient structure hydrogen-barrier coating prepared by the preparation method according to any one of claims 1 to 4, characterized in that, The content of Ti, C, and N elements in the coating structure varies in a gradient from the surface to the interior. The inner layer of the coating is a TiC-rich phase, and the outer layer of the coating is a TiN-rich phase.

6. The TiCN gradient structure hydrogen barrier coating according to claim 5, characterized in that, The coating has a thickness of 2-8µm, the TiC-rich phase layer has a thickness of 0.3-2µm and accounts for 60-80%, and the TiN-rich phase layer has a thickness of 1-5µm and accounts for 60-85%.

7. The TiCN gradient structure hydrogen barrier coating according to claim 5, characterized in that, The coating contains TiCN grains, which have a blocky structure and are interlocked. The grain size of the TiCN grains is 1~3µm.

8. The TiCN gradient structure hydrogen barrier coating according to claim 5, characterized in that, The coating has a hydrogen permeation reduction factor of 500~800 at 300°C.

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