Multistage coating oxygen-mediated annealing preparation method based on RAFM steel / titanium nitride

Abstract

The invention discloses a multistage coating oxygen-mediated annealing preparation method based on RAFM steel / titanium nitride, and belongs to the technical field of coating preparation. The method comprises the steps that a TiN coating is deposited on the surface of a low-activation ferrite / martensitic steel matrix through magnetron sputtering, a pure titanium target material is used, the nitrogen-argon flow ratio is 1: 13-1: 18, the background vacuum degree is 4-6 * 10 <-5 > Pa, the deposition time is 60-90 min, and extra active heating is not applied to the matrix in the deposition process; placing the deposition coating sample in a quartz tube for packaging, wherein the gas pressure in the tube provides a trace oxygen atmosphere; and then annealing treatment is conducted at the temperature of 800-1000 DEG C, and heat preservation is conducted for 90-120 Through oxygen-mediated element diffusion and reaction, a multi-stage composite structure sequentially comprising an inner oxide layer, an Fe inner enrichment layer, a TiN layer, an Fe outer enrichment layer and an outer oxide layer from a matrix to the outside is formed in the TiN coating in situ. The method is simple in process, a transition layer does not need to be additionally deposited, and the prepared multi-stage coating is well combined with a matrix interface, has excellent thermal shock resistance and can bear more than 30 times of thermal shock cycles.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, specifically relating to a method for preparing multi-level coatings based on RAFM steel / titanium nitride through oxygen-mediated annealing. Background Technology

[0002] Low-activation ferritic / martensitic steel (RAFM steel) is an important material used in the field of high-temperature structural materials due to its excellent low-activation characteristics, mechanical properties, and radiation resistance. To improve its performance in harsh environments, a protective coating needs to be prepared on the surface of RAFM steel. TiN ceramic coatings have become a candidate material due to their high hardness, high melting point, corrosion resistance, and relatively close coefficient of thermal expansion to that of RAFM steel.

[0003] The difference in thermal expansion coefficients between ceramic coatings and metal substrates makes the coatings prone to interfacial stress in high-temperature service environments, leading to coating peeling. The interfacial bonding mechanisms between the coating and the substrate include chemical bonding, physical adsorption, and mechanical locking, with chemical bonding providing the highest interfacial bonding strength.

[0004] Currently, common methods for improving the bonding strength between ceramic coatings and substrates include high-temperature diffusion treatment and the introduction of intermediate transition layers. High-temperature diffusion treatment promotes metallurgical bonding by facilitating elemental interdiffusion between the coating and the substrate, but often requires complex high-temperature processing. Introducing intermediate transition layers involves multi-layer deposition processes, which are relatively cumbersome.

[0005] Annealing can promote interdiffusion of elements between the coating and the substrate, forming an interface region with a gradual change in composition. This method has been used to optimize the interfacial bonding performance between ceramic coatings and metal substrates. Introducing trace amounts of oxygen during annealing can affect the diffusion behavior of elements such as Fe and Cr in the substrate, thereby forming a multilayer structure in the coating.

[0006] Therefore, how to provide a relatively simple process that can improve the interfacial bonding performance between TiN coating and RAFM steel substrate is a key research direction for those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a novel in-situ preparation method for multi-level coatings based on RAFM steel / titanium nitride using oxygen-mediated annealing.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for in-situ preparation of a multi-level coating based on RAFM steel / titanium nitride is disclosed. This method utilizes physical vapor deposition (PVD) to deposit a TiN coating on a low-activation ferrite / martensitic steel substrate. The deposited sample is then subjected to oxygen-mediated annealing. This process creates a composite coating on the substrate, consisting of an inner oxide layer, an inner Fe enrichment layer, a TiN layer, an optional outer Fe enrichment layer, and an outer oxide layer, arranged in situ from the substrate outwards. The method includes the following steps: Step (1): A TiN coating was prepared on the surface of a low-activation ferrite / martensitic steel substrate by physical vapor deposition using magnetron sputtering. A pure titanium target was used, and the nitrogen-argon gas flow ratio was N2:Ar = 1:10-1:20. The base vacuum was 4-8×10⁻⁶. - 5 Pa, the partial pressure of nitrogen and argon gas flow during deposition is 0.4-0.8 Pa, the deposition time is 40-90 min, no additional active heating is applied to the substrate during the deposition process, and the substrate temperature is always maintained in the room temperature range of 20℃-40℃; Step (2): The sample with the deposited TiN coating is placed in a controlled micro-oxygen atmosphere, which is an argon-oxygen mixture with an oxygen volume fraction of 0.1%-0.5%, provided through vacuum sealing of a quartz tube. The final total pressure after vacuum sealing is set to 4-8 × 10⁻⁶. -3 Pa; Step (3): Place the product in a box furnace for annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120min, the heating rate is 5-15℃ / min, and the product is cooled with the furnace. Through oxygen-mediated element diffusion and reaction, a multilayer alternating structure containing at least one TiN layer, at least one oxide layer and at least one metal enrichment layer is formed in situ in the TiN coating.

[0009] Furthermore, the low-activation ferritic / martensitic steel is CLF-1 steel, and its chemical composition by mass percentage is: Cr 8.2-8.8%, W 1.3-1.7%, Ta 0.05-0.15%, Mn 0.3-0.7%, V 0.2-0.4%, C 0.09-0.14%, N 0.02-0.04%, with the balance being Fe.

[0010] Furthermore, the main components of the outer oxide layer and the inner oxide layer are CrTi2O5.

[0011] Furthermore, in step (1), a titanium target with a purity of 99.99% is used, and the nitrogen-argon gas flow ratio is N2:Ar = 1:13-1:16, with a background vacuum of 4-6×10⁻⁶. -5 Pa, the partial pressure of nitrogen and argon gas flow during deposition is 0.3-0.6 Pa, and the deposition time is 60-90 min.

[0012] Furthermore, in step (2), the controllable trace oxygen atmosphere is achieved by setting the oxygen volume fraction inside the quartz tube to 0.2%-0.4% and the total gas pressure inside the tube to 6-8×10⁻⁶. -3 Pa provides.

[0013] Further, in step (3), an inner oxide layer with a thickness of 0.2-0.3 μm is formed in situ between the TiN coating and the low-activation ferrite / martensitic steel substrate by annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

[0014] Furthermore, in step (3), an Fe enrichment layer with a thickness of less than 0.2 μm is formed in situ between the TiN coating and the low-activation ferrite / martensitic steel matrix by annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

[0015] Furthermore, in step (3), an Fe enrichment layer with a thickness of less than 0.3 μm is formed in situ on the side of the TiN coating near the outer surface by annealing. The annealing temperature is 1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

[0016] Further, in step (3), an outer oxide layer with a thickness of less than 0.3 μm is formed in situ on the outer surface of the TiN coating by annealing. The annealing temperature is 800℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

[0017] Furthermore, the total thickness of the TiN coating deposited in step (1) is 1.2μm-1.8μm, and the overall thickness of the coating fluctuates by no more than ±10% during the annealing process. The thickness of the inner and outer oxide layers formed in annealing in step (3) is 0.2-0.3μm, the thickness of the Fe inner enrichment layer formed in annealing in situ is less than 0.2μm, and the thickness of the Fe outer enrichment layer formed in annealing in situ is less than 0.3μm.

[0018] Beneficial effects of this invention: (1) In this invention, a multi-level composite structure is formed in situ between the RAFM steel substrate and the TiN coating by annealing in a controlled micro-oxygen atmosphere, which consists of an inner oxide layer, an inner Fe enrichment layer, a TiN layer, an outer Fe enrichment layer, and an outer oxide layer. This multi-level structure creates a compositional gradient transition between the coating and the substrate, which helps to alleviate the interfacial stress caused by the difference in thermal expansion coefficients.

[0019] (2) This invention achieves the diffusion and redistribution of matrix elements into the coating through the controlled oxygen-mediated effect during the annealing process. The presence of the Fe inner enrichment layer and the Fe outer enrichment layer forms a structure in which the metal layer and the ceramic layer are alternately arranged, which is beneficial to improving the mechanical compatibility of the coating system.

[0020] (3) The method of the present invention only requires a single controlled oxygen annealing treatment after physical vapor deposition to form a multi-level structure in situ inside the coating. Compared with the process of pre-depositing multiple transition layers, the process flow of the present invention is relatively simplified.

[0021] (4) By adjusting the annealing temperature and the oxygen pressure inside the quartz tube, the present invention can control the number of layers and the thickness of each layer of the multi-level coating. Experiments show that annealing at 900℃ can form a 4-layer structure, annealing at 1000℃ can form a 5-layer structure, the thickness of the inner and outer oxide layers can be controlled at 0.2-0.3μm, and the thickness of the Fe enriched layer can be controlled at 0.1-0.3μm.

[0022] (5) The multi-level coating prepared by the method of the present invention can withstand more than 30 thermal shock cycles without peeling after standard thermal shock test verification, and the interface bonding state is relatively stable. Attached Figure Description

[0023] Figure 1 This is a microstructure diagram of the 4-layer TiN composite coating prepared in Example 1 of the present invention.

[0024] Figure 2 This is a microstructure diagram of the 5-layer TiN composite coating prepared in Example 2 of the present invention.

[0025] Figure 3 This is a microstructure diagram of the 4-layer TiN composite coating prepared in Example 3 of the present invention.

[0026] Figure 4 This is a microstructure diagram of the 5-layer TiN composite coating prepared in Example 4 of the present invention.

[0027] Figure 5 This is a microstructure diagram of the monolayer TiN coating prepared in Comparative Example 1 of the present invention.

[0028] Figure 6 This is a diagram of the failure microstructure of the TiN coating prepared in Comparative Example 2 of this invention.

[0029] Figure 7 This is a microstructure diagram of the three-layer TiN composite coating prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the following description is intended to illustrate, and not limit, the scope of protection claimed by this invention.

[0031] Example 1 This embodiment provides a method for preparing a multi-level coating based on RAFM steel / titanium nitride using oxygen-mediated annealing, the steps of which are as follows: (1) Pretreatment of the substrate: The RAFM steel substrate was polished with 150#, 400#, 800#, 1200# and 2000# sandpaper in sequence, ultrasonically cleaned in deionized water and acetone for 5 minutes each, dried and placed in the magnetron sputtering reaction chamber.

[0032] (2) TiN coating deposition: A TiN coating was prepared on the substrate surface using magnetron sputtering. A titanium target with a purity of 99.99% was used, and the base vacuum was evacuated to 6 × 10⁻⁶. -5 Pa. Nitrogen and argon gases were introduced at a flow rate ratio of N2:Ar = 1:15, and the working pressure was controlled at 0.4 Pa during deposition. The deposition power was 200 W, the bias voltage was -200 V, and the deposition time was 60 min. No external heating was applied to the substrate during the deposition process, and the substrate temperature was maintained at 25℃ ± 3℃.

[0033] (3) Encapsulation: The sample with the deposited TiN coating was placed in a quartz tube, and an argon-oxygen mixture with an oxygen volume fraction of 0.3% was introduced into the tube. The quartz tube was then vacuum-sealed, and the internal pressure was set to 6 × 10⁻⁶. -3 Pa, so that the sample is in a trace oxygen atmosphere.

[0034] (4) Annealing treatment: The packaged sample is placed in a box furnace for annealing treatment. The annealing temperature is 900℃, the holding time is 90min, and the heating rate is 10℃ / min. After the holding time is completed, the sample is cooled to room temperature in the furnace.

[0035] The composite coating structure prepared in this embodiment is as follows: Figure 1 As shown. From Figure 1 As can be seen, the total coating thickness is approximately 1.5 μm. EDS analysis reveals a four-layer structure extending outwards from the RAFM steel substrate: an inner oxide layer (level 1), an inner Fe enrichment layer (level 2), a TiN layer (level 3), and an outer oxide layer (level 4). The inner oxide layer is approximately 0.22 μm thick, the outer oxide layer is approximately 0.25 μm thick, and the inner Fe enrichment layer is approximately 0.08 μm thick. Combined EDS, XRD, and TEM analysis shows that the main component of both the inner and outer oxide layers is CrTi2O5.

[0036] The samples prepared in this embodiment were subjected to standard thermal shock tests. The results showed that the coating could withstand 30 thermal shock cycles before local peeling occurred, which did not meet the failure criteria.

[0037] Example 2 This embodiment provides a method for preparing a multi-level coating based on RAFM steel / titanium nitride using oxygen-mediated annealing, the steps of which are as follows: (1) Matrix pretreatment: Same as in Example 1.

[0038] (2) TiN coating deposition: Same as in Example 1.

[0039] (3) Packaging process: Same as in Example 1.

[0040] (4) Annealing treatment: The annealing temperature is 1000℃, the holding time is 90min, and the heating rate is 10℃ / min. After the holding time is completed, the furnace is cooled to room temperature.

[0041] The composite coating structure prepared in this embodiment is as follows: Figure 2 As shown. From Figure 2 As can be seen, the total coating thickness is approximately 1.5 μm. EDS analysis reveals a five-layer structure extending outwards from the RAFM steel substrate: an inner oxide layer (level 1), an inner Fe enrichment layer (level 2), a TiN layer (level 3), an outer Fe enrichment layer (level 4), and an outer oxide layer (level 5). The inner oxide layer is approximately 0.2 μm thick, the outer oxide layer is approximately 0.13 μm thick, the inner Fe enrichment layer is approximately 0.08 μm thick, and the outer Fe enrichment layer is approximately 0.15 μm thick. Combined EDS, XRD, and TEM analysis indicates that the main component of both the inner and outer oxide layers is CrTi₂O₅.

[0042] The sample prepared in this embodiment was subjected to a standard thermal shock test. The results showed that the coating could withstand 35 thermal shock cycles without local peeling, thus meeting the core performance requirements of the present invention.

[0043] Example 3 The difference between this embodiment and Embodiment 1 is that the annealing and heat preservation time in step (4) is different.

[0044] (1) Matrix pretreatment: Same as in Example 1.

[0045] (2) TiN coating deposition: Same as in Example 1.

[0046] (3) Packaging process: Same as in Example 1.

[0047] (4) Annealing treatment: heat preservation time 120 min, other parameters are the same as in Example 1.

[0048] The composite coating structure prepared in this embodiment is as follows: Figure 3As shown. The composite coating prepared in this embodiment also forms a four-layer structure with more complete element diffusion. The total thickness of the composite coating is approximately 1.4 μm, and it forms a stable four-layer structure from the substrate outward: an inner oxide layer (level 1), an inner Fe enrichment layer (level 2), a TiN host layer (level 3), and an outer oxide layer (level 4). The thickness of the inner oxide layer is approximately 0.2 μm, the thickness of the outer oxide layer is approximately 0.25 μm, and the thickness of the inner Fe enrichment layer is approximately 0.12 μm.

[0049] The sample prepared in this embodiment was subjected to a standard thermal shock test. The results showed that the coating could withstand 35 thermal shock cycles without local micro-peeling, thus meeting the core performance requirements of the present invention.

[0050] Example 4 The difference between this embodiment and Embodiment 2 is that the annealing and heat preservation time in step (2) is different.

[0051] (1) Matrix pretreatment: Same as in Example 1.

[0052] (2) TiN coating deposition: Same as in Example 1.

[0053] (3) Packaging process: Same as in Example 1.

[0054] (4) Annealing treatment: heat preservation time 120 min, other parameters are the same as in Example 2.

[0055] The composite coating structure prepared in this embodiment is as follows: Figure 4 As shown. The composite coating prepared in this embodiment also forms a 5-layer structure, but the coating porosity is increased, from Figure 4 As can be seen, the total thickness of the composite coating is approximately 1.6 μm, forming a stable five-layer structure from the substrate outwards: an inner oxide layer (level 1), an inner Fe enrichment layer (level 2), a TiN main layer (level 3), an outer Fe enrichment layer (level 4), and an outer oxide layer (level 5). The inner oxide layer has a thickness of approximately 0.25 μm, the outer oxide layer approximately 0.1 μm, the inner Fe enrichment layer approximately 0.07 μm, and the outer Fe enrichment layer approximately 0.18 μm.

[0056] The sample prepared in this embodiment was subjected to a standard thermal shock test. The results showed that the coating could withstand 32 thermal shock cycles before local micro-peeling occurred, which did not meet the failure criteria.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is that no annealing treatment is performed.

[0058] (1) Matrix pretreatment: Same as in Example 1.

[0059] (2) TiN coating deposition: Same as in Example 1.

[0060] (3) Post-processing: The deposited sample is not encapsulated or annealed.

[0061] The coating structure prepared in this comparative example is as follows: Figure 5 As shown. From Figure 5 It can be seen that the sample prepared in this comparative example is a single-layer TiN coating with a thickness of about 1.4 μm, without a gradient multi-level structure, and the interface between the coating and the substrate is a clear physical adsorption interface.

[0062] The samples prepared in this comparative example were subjected to standard thermal shock tests. The results showed that the coating peeled off over a large area after 8 cycles, reaching the failure standard.

[0063] Comparative Example 2 The difference between this comparative example and Example 1 is that no encapsulation oxygen control is performed during the annealing process.

[0064] (1) Matrix pretreatment: Same as in Example 1.

[0065] (2) TiN coating deposition: Same as in Example 1.

[0066] (3) Annealing treatment: The deposited sample was placed directly into a box furnace and annealed in an air atmosphere. The annealing temperature was 900℃, the holding time was 90min, and the heating rate was 10℃ / min.

[0067] The coating structure prepared in this comparative example is as follows: Figure 6 As shown. From Figure 6 It can be seen that the sample prepared in this comparative example exhibits obvious failure behavior. SEM observation shows cracks at the interface between the coating and the substrate. This sample system cannot meet the core performance requirements of this invention.

[0068] Comparative Example 3 The difference between this comparative example and Example 1 is that the annealing temperature is different in step (4).

[0069] (1) Matrix pretreatment: Same as in Example 1.

[0070] (2) TiN coating deposition: Same as in Example 1.

[0071] (3) Packaging process: Same as in Example 1.

[0072] (4) Annealing treatment: The annealing temperature is 800℃, the holding time is 120min, the heating rate is 10℃ / min, and other parameters are the same as in Example 1.

[0073] The microstructure of the composite coating prepared in this comparative example is as follows: Figure 7 As shown. The sample prepared in this comparative example did not form a clear multi-level gradient structure; the coating was still mainly a monolayer of TiN, with only a small amount of elemental diffusion and no continuous Fe-enriched layer formed. From Figure 7It can be seen that the total thickness of the composite coating is approximately 1.3 μm, forming a three-layer gradient structure from the substrate outwards: an inner Fe diffusion layer (level 1), a TiN main layer (level 2), and an outer oxide layer (level 3). The thickness of the inner Fe diffusion layer is approximately 0.15 μm, and the thickness of the outer oxide layer is approximately 0.2 μm. Analysis using EDS, XRD, and TEM shows that the main component of the outer oxide layer is CrTi2O5.

[0074] The samples prepared in this comparative example were subjected to standard thermal shock tests. The results showed that the coating could withstand 30 thermal shock cycles before local microcracks appeared, and the failure criteria were not met.

[0075] The scope of protection of this invention is not limited to the disclosed embodiments. Any non-substantial modifications made by those skilled in the art under the concept of this invention should fall within the scope of protection of this invention.

Claims

1. A method for preparing a multi-level coating based on RAFM steel / titanium nitride using oxygen-mediated annealing, characterized in that, A TiN coating was deposited on a low-activation ferrite / martensitic steel substrate using physical vapor deposition (PVD). The deposited sample was then annealed to prepare a composite coating in situ on the substrate, consisting of an inner oxide layer, an inner Fe enrichment layer, a TiN layer, an optional outer Fe enrichment layer, and an outer oxide layer, arranged sequentially from the substrate outwards. This method includes the following steps: Step (1): A TiN coating was prepared on the surface of a low-activation ferrite / martensitic steel substrate by physical vapor deposition using magnetron sputtering. A pure titanium target was used, and the nitrogen-argon gas flow ratio was N2:Ar = 1:10-1:

20. The base vacuum was 4-8×10⁻⁶. -5 Pa, the partial pressure of nitrogen and argon gas flow during deposition is 0.4-0.8 Pa, the deposition time is 40-90 min, no additional active heating is applied to the substrate during the deposition process, and the substrate temperature is always maintained in the room temperature range of 20℃-40℃; Step (2): The sample with the deposited TiN coating is placed in a controlled micro-oxygen atmosphere, which is an argon-oxygen mixture with an oxygen volume fraction of 0.1%-0.5%, provided through vacuum sealing of a quartz tube. The final total pressure after vacuum sealing is set to 4-8 × 10⁻⁶. -3 Pa; Step (3): Place the product in a box furnace for annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120min, the heating rate is 5-15℃ / min, and the product is cooled with the furnace. Through oxygen-mediated element diffusion and reaction, a multilayer alternating structure containing at least one TiN layer, at least one oxide layer and at least one metal enrichment layer is formed in situ in the TiN coating.

2. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, The low-activation ferritic / martensitic steel is CLF-1 steel, and its chemical composition by mass percentage is: Cr 8.2-8.8%, W 1.3-1.7%, Ta 0.05-0.15%, Mn 0.3-0.7%, V 0.2-0.4%, C 0.09-0.14%, N 0.02-0.04%, with the balance being Fe.

3. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, The main components of the outer oxide layer and the inner oxide layer are CrTi2O5.

4. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (1), a titanium target with a purity of 99.99% is used, and the nitrogen-argon gas flow ratio is N2:Ar = 1:13-1:16, with a background vacuum of 4-6×10⁻⁶. -5 Pa, the partial pressure of nitrogen and argon gas flow during deposition is 0.3-0.6 Pa, and the deposition time is 60-90 min.

5. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (2), the controllable trace oxygen atmosphere is achieved by setting the oxygen volume fraction inside the quartz tube to 0.2%-0.4% and the total gas pressure inside the tube to 6-8×10⁻⁶. -3 Pa provides.

6. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (3), an inner oxide layer with a thickness of 0.2-0.3 μm is formed in situ between the TiN coating and the low-activation ferrite / martensitic steel substrate by annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

7. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (3), an Fe enrichment layer with a thickness of less than 0.2 μm is formed in situ between the TiN coating and the low-activation ferrite / martensitic steel matrix by annealing. The annealing temperature is 900℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

8. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (3), an Fe enrichment layer with a thickness of less than 0.3 μm is formed in situ on the side of the TiN coating near the outer surface by annealing. The annealing temperature is 1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

9. The method for preparing a multi-stage coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, In step (3), an outer oxide layer with a thickness of less than 0.3 μm is formed in situ on the outer surface of the TiN coating by annealing. The annealing temperature is 800℃-1000℃, the holding time is 90-120 min, the heating rate is 10-15℃ / min, and the furnace is cooled.

10. The method for preparing a multi-level coating based on RAFM steel / titanium nitride using oxygen-mediated annealing according to claim 1, characterized in that, The total thickness of the TiN coating deposited in step (1) is 1.2μm-1.8μm. The overall thickness of the coating fluctuates by no more than ±10% during the annealing process. The thickness of the inner and outer oxide layers formed in annealing in step (3) is 0.2-0.3μm. The thickness of the Fe inner enrichment layer formed in annealing in situ is less than 0.2μm. The thickness of the Fe outer enrichment layer formed in annealing in situ is less than 0.3μm.

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