A composite coating based on medium temperature alpha-alumina and a method for its production

Abstract

The application relates to the technical field of composite coating preparation, and discloses a composite coating based on medium temperature and a preparation method thereof, which comprises the following steps: adopting a hot-wall chemical vapor deposition method to sequentially deposit a TiN layer, a TiCN layer, a bonding layer and a layer on the surface of a substrate at a temperature of 700-900 DEG C; the bonding layer comprises a TiCNO layer, a TiAlCNO layer and an oxidation treatment layer which are sequentially formed; the layer is deposited by using a mixed gas containing H2, HCl, CH4 and Ar, and the volume fractions of the gases are as follows: 5-10 vol% of H2, 0-3 vol% of HCl, 0.3-2.5 vol% of CH4 and 0.5-1 vol% of Ar, and the rest is Ar; all the layers in the deposition process are carried out in the temperature range, and the temperature is kept constant. The TiCN+ substrate-based composite coating prepared at the medium temperature of 700-900 DEG C has excellent bonding force, and has a wide application range.

Description

Technical Field

[0001] This invention relates to the field of composite coating preparation technology, specifically to a method based on medium temperature... Composite coatings and their preparation methods. Background Technology

[0002] TiCN+ prepared by hot-wall chemical vapor deposition (CVD) Composite coatings, possessing excellent wear resistance and high-temperature resistance, have been widely used in the field of cemented carbide CNC cutting tools. However, The coating preparation temperature is relatively high, typically between 900-1050 degrees Celsius (the high-temperature reaction zone). However, at this temperature, heat-sensitive materials such as molybdenum and special alloy steel will undergo annealing, leading to a decrease in workpiece hardness and deformation of thin-sheet products. This severely affects workpiece performance and precision, limiting the application of TiCN+ coatings. Composite coatings are used in a wider range of fields. This temperature bottleneck prevents the advantages of hot-wall CVD technology, such as large furnace loading, good coating uniformity, and applicability to complex shapes and large aspect ratio pipes, from being fully utilized in a wider range of industrial scenarios. It also hinders the application and promotion of this coating technology in high-end fields such as aerospace, energy, and precision molds.

[0003] Domestic and international research on TiCN+ Most research on composite coatings focuses on the field of cemented carbide cutting tools, mainly because WC-based cemented carbide has relatively low temperature sensitivity. At 1000℃, even if the deposition time exceeds 24 hours, the WC alloy will not anneal or deform, thus not affecting the final CNC tool performance. , , , The reaction gases can react efficiently and completely, and by adjusting the gas ratio, high-quality products with different structures can be prepared. Coatings. For example, patent CN118880276A describes the preparation of (001) textured coatings within a temperature range of 950-1050 degrees Celsius by adjusting the gas ratio. Composite coating; patent publication number CN105506580A, by adding Gas, Zr modified with (300) texture prepared in the range of 980-1020 degrees. Coating; Patent CN104085142B describes the preparation of textured fine particles within a temperature range of 900-1020 degrees Celsius by adjusting the gas ratio. Coating; US Patent US11471951B2, fine particles with a (001) texture were prepared at 1000 degrees Celsius by step-controlled HCl flow rate. Coating; US Patent US2018 / 0002817A1, prepared at 1000 degrees Celsius by atmosphere control. Composite coatings; European patent EP2902528B1 prepared coatings with different textures (110), (012), and (001) by adjusting the gas ratio within a temperature range of 930-1030°C. Composite coating. Among them, (001), (110), (012), etc. are crystal plane indices, used to identify the orientation of different atomic planes in the crystal.

[0004] However, if the deposition temperature is lowered to the medium temperature range, such as 850°C, and the gas ratio and process parameters used at high temperatures are still applied, problems such as a significant decrease in coating bonding strength, incomplete gas reaction, excessively low deposition rate, and easy nozzle blockage will occur. These problems will seriously affect the stability of the process and the usability of the coating, fail to meet the requirements of industrial use, and pose great risks to product quality and fixture maintenance.

[0005] For deposition in the mid-temperature range (700–900℃) Some research has been conducted abroad on coatings, for example, US Patent 6689450B2, which prepared coatings in the range of 750-850. and Composite coatings; Larsson and Ruppi (Microstructure and properties of CVD) The study, published in the International Journal of Refractory Metals and Hard Materials, 19(2001), 515-522, investigated coatings prepared at 800 degrees Celsius. The coating performance was assessed, but the results generally showed poor coating adhesion.

[0006] In these foreign studies, the preparation was carried out under mesophilic conditions. The coating has two main problems: firstly, the coating prepared under medium-temperature conditions... The coating adhesion is not ideal, making it difficult to meet the requirements of industrial applications; secondly, and Both are metastable phases, and when the operating temperature exceeds 600 degrees Celsius, they will irreversibly transform into... At the same time, the volume change causes the coating to wear out rapidly during use.

[0007] Currently, domestic research focuses on the preparation of materials using hot-wall CVD technology in the intermediate temperature range. Research on coatings is still in its infancy, but in fields such as molybdenum parts and high-temperature alloy steel parts, there is a market demand for coatings that combine high bonding strength and high-temperature stability. The demand for coatings is becoming increasingly urgent and has become a real need. Therefore, the development of high-adhesion, stable α-phase hot-wall CVD coatings under intermediate temperature conditions is crucial. Composite coatings and their preparation methods are of great significance. Summary of the Invention

[0008] This invention aims to provide a medium-temperature-based The composite coating and its preparation method can prepare TiCN+ with excellent adhesion under medium temperature conditions of 700-900 degrees Celsius. Base composite coating; with a wide range of applications.

[0009] To achieve the above objectives, the present invention provides the following basic solution.

[0010] Option 1

[0011] A medium temperature-based The method for preparing the composite coating includes the following steps:

[0012] A hot-wall chemical vapor deposition method was used to sequentially deposit TiN, TiCN, and a bonding layer on the substrate surface at a temperature of 700–900℃. layer;

[0013] The bonding layer comprises a TiCNO layer, a TiAlCNO layer, and an oxidation treatment layer formed sequentially;

[0014] The Layers use contain HCl , and The mixture of gases was deposited, with each gas having a volume fraction of 5–10 vol%. ,0–3 vol%HCl, 0.3–2.5 vol% 0.5-1 vol% The margin is ;

[0015] All layers are deposited within the temperature range during the deposition process, and the temperature remains constant.

[0016] Option 2

[0017] A medium temperature-based The composite coating, deposited on a substrate, comprises, from the inside out: a TiN layer bonded to the substrate; a TiCN layer deposited on the TiN layer; a bonding layer deposited on the TiCN layer; and a [missing information - likely a coating material] deposited on the bonding layer. layer;

[0018] The bonding layer is a composite structure of TiCNO, TiAlCNO, and an oxide-treated layer formed by CVD; The layer is pure The phase structure, and the composite coating is prepared by hot-wall chemical vapor deposition in a temperature range of 700°C to 900°C.

[0019] The working principle and advantages of this invention are as follows:

[0020] This invention provides a method based on medium temperature The composite coating and its preparation method can prepare TiCN+ with excellent adhesion under medium temperature conditions of 700-900 degrees Celsius. Base composite coating; wide range of applications. Key points:

[0021] This solution significantly reduces the deposition temperature by optimizing the gas combination and ratio, and designing a multi-layer transition structure. This avoids the hardness reduction and deformation problems caused by high-temperature annealing of the substrate, while maintaining a high bonding force between the coating and the substrate. This not only helps to broaden the application range of this type of coating, but also helps to give full play to the advantages of hot-wall CVD technology in handling complex-shaped workpieces and large furnace loading capacity, providing a feasible surface strengthening solution for high-precision, thin-walled parts.

[0022] Notably, this scheme achieves pure [propagation] under mesophilic conditions. Mutually Stable preparation of coatings, effectively avoiding metastable phases (such as...) phase or The formation of the phase. Specifically, in known existing technologies, deposition in the intermediate temperature range yields... The coatings are mostly metastable phases, which will undergo changes in orientation under high-temperature service conditions. Phase transformation, accompanied by volume shrinkage and internal stress release, leads to coating cracking and peeling. This solution addresses this by addressing the bonding layer, oxide layer, and... Precise control during the layer deposition stage , CO , The proportion of reacting gases such as HCl promotes Phase nucleation and growth were inhibited, suppressing the formation of metastable phases. Furthermore, a specially designed TiCNO / TiAlCNO composite structure served as a transition layer, gradually harmonizing the formation of TiCN and... The differences in lattice structure and thermal expansion between the layers further ensure the overall stability and bonding strength of the coating system.

[0023] Furthermore, from the perspective of process efficiency and engineering applications, by adjusting... The reaction gas ratio of the layer can also be guaranteed under medium temperature conditions. The growth rate is no less than 0.6 μm / h, overcoming the technical bottlenecks commonly encountered in medium-temperature CVD processes, such as slow growth, incomplete reaction, and easy clogging, thus meeting the requirements of rapid industrial production. Simultaneously, the entire coating deposition process can be completed at the same temperature, eliminating the need for temperature adjustments at different coating stages. This not only simplifies equipment control and process flow, improves process stability, but also helps reduce energy consumption. It is not only suitable for traditional cemented carbide tools but can also be extended to high-temperature sensitive materials such as molybdenum and special alloy steels. Attached Figure Description

[0024] Figure 1 This invention provides a method based on medium temperature. A schematic diagram of the coating structure in an embodiment of the composite coating and its preparation method;

[0025] Figure 2 This is a schematic diagram of the surface scratch morphology of WC cemented carbide in application example 1 of the present invention;

[0026] Figure 3 The scratch sound signal and friction coefficient curve are shown in Application Example 1 of the present invention;

[0027] Figure 4 This is a schematic diagram of the surface scratch morphology of WC cemented carbide in application example 2 of the present invention;

[0028] Figure 5 This is a schematic diagram of the appearance of the special alloy steel sheet in application example 1 of the present invention;

[0029] Figure 6 This is an appearance drawing of the furnace-mounted carbide cutting tool and fixture, which is an application example 2 of the present invention.

[0030] Figure 7 This is a SEM image of the coating fracture morphology in application example 1 of the present invention;

[0031] Figure 8 This is a SEM image of the coating fracture morphology in application example 2 of the present invention;

[0032] Figure 9 The coating XRD pattern is shown in Application Example 1 of the present invention.

[0033] Figure 10 The coating XRD pattern is shown in application example 2 of the present invention.

[0034] The markings in the accompanying drawings include: 1-composite coating, 00-substrate, 11-TiN, 12-TiCN, 13-bonding layer, 14- 131-TiCNO, 132-TiAlCNO, 133-Oxidation treatment layer. Detailed Implementation

[0035] The following detailed explanation illustrates the specific implementation methods:

[0036] The basic implementation examples are as follows: Figure 1 As shown: A method based on medium temperature The method for preparing the composite coating includes the following steps:

[0037] A hot-wall chemical vapor deposition method was used to sequentially deposit TiN, TiCN, and a bonding layer on the substrate surface at a temperature of 700–900℃. layer; The outermost layer is the first layer. All layers are deposited within the stated temperature range, and the temperature remains constant.

[0038] Optionally, the deposition temperature is preferably 800–900°C.

[0039] The substrate is hard alloy or special alloy steel.

[0040] The TiN layer is used to ensure the adhesion between the coating and the substrate, and the coating thickness is 0.3-1.5 μm; its deposition pressure is 100-500 mbar, and it uses a solution containing 0.5-3 vol%. 25–40 vol% The margin is A mixture of gases is used for vapor phase deposition.

[0041] The TiCN layer serves as a wear-resistant layer, with a coating thickness of 1-10 μm; its deposition pressure is 100–300 mbar, and it uses materials containing 2–3.5 vol%. 1–2 vol% 30–40 vol% The margin is A mixture of gases is used for vapor phase deposition.

[0042] In TiCN layer deposition, compared to conventional TiCN deposition processes, the deposition pressure is typically limited to a lower range of 50-100 mbar to reduce coating grain size. However, at temperatures below 800 degrees Celsius, the gas reaction rate decreases. To improve deposition efficiency and economy, the deposition pressure needs to be increased, ideally exceeding 200 mbar. This approach, by increasing the reaction pressure, effectively promotes the mixing and mass transfer of reactant gases. While ensuring refined coating grain size, it also considers deposition efficiency and process economy, achieving a better balance between coating performance and preparation cost.

[0043] The bonding layer is used to ensure that TiCN and To ensure effective bonding, given the different structures of the two materials, the bonding layer was designed using a three-step process: "TiCNO + TiAlCNO + oxidation treatment," allowing TiCN to gradually transition to its final form. This ensures adhesion, and the coating thickness is 0.3-1μm.

[0044] Specifically, the bonding layer comprises a TiCNO layer, a TiAlCNO layer, and an oxidation treatment layer formed sequentially.

[0045] The TiCNO layer was deposited at a pressure of 300–500 mbar, using a solution containing 2–4 vol%. 7–13 vol% 7–13 vol% 2–4 vol% CO, balance: A mixture of gases is used for vapor phase deposition.

[0046] The TiAlCNO layer was deposited at a pressure of 100–300 mbar, using a solution containing 2–5 vol%. 5–10 vol% 5–10 vol% , 2–5.5 vol%CO, 0.5-1.5 vol% The margin is A mixture of gases is used for vapor phase deposition.

[0047] By employing the unique TiCN+TiCNO+TiAlCNO multi-process progressive mode and implementing precise synergistic control of gas ratios (especially CO) and deposition pressure, it helps to solve the problem of simultaneously ensuring the required parameters under intermediate-temperature chemical vapor deposition conditions. The core challenges of heteroepitaxial growth and excellent interfacial bonding.

[0048] Specifically, relevant studies have demonstrated that this formation can only occur on oxidized TiN, TiC, or TiCN surfaces. To ensure good adhesion, the bonding layer is designed as a multi-process mode of TiCN+TiCNO+TiAlCNO. The proportion of oxygen is crucial; after oxidation, a layer of Ti oxide forms on the surface of TiN, TiC, or TiCN. Epitaxial growth on it, insufficient or excessive oxygen may cause Unable to form Phase or other factors can affect the bonding strength. Under intermediate temperature conditions, the reactivity of reactive gases decreases, especially the oxidizing ability of oxidizing gases. Therefore, under intermediate temperature conditions, in order to obtain good bonding strength, the proportion of various gases in the bonding layer needs to be precisely controlled, especially the proportion of CO, to ensure sufficient oxidation of TiCN. At the same time, in order to improve the deposition rate under intermediate temperature conditions, the deposition pressure design also needs to be higher than that of conventional high temperature processes.

[0049] This method, through precise control of the proportions of gases such as CO, ensures that the TiCN substrate receives sufficient and appropriate oxidation, thus providing... The epitaxial growth creates an ideal chemical interface; at the same time, by appropriately increasing the deposition pressure, the reaction kinetic limitations under the medium temperature environment are effectively compensated, ensuring processing efficiency.

[0050] The oxide layer was deposited at a pressure of 50–150 mbar, using a solution containing 1–5 vol%. 0.5–3 vol% CO, 1–3 vol% HCl, balance: A mixture of gases is used for vapor phase deposition.

[0051] The The outermost layer possesses excellent high-temperature resistance and wear resistance, and is pure... Phase. The aforementioned Layers use contain HCl , and The mixture of gases was deposited, with each gas having a volume fraction of 5–10 vol%. ,0-3vol%HCl,0.3-2.5vol% 0.5-1 vol% The margin is Furthermore, the deposition pressure is 100–300 mbar, and the growth rate is... .

[0052] Under intermediate temperature conditions, the reactivity of gases decreases; if conventional high-temperature conditions are followed... The process involves coating deposition, even when using a large proportion of catalyst. It is still possible to cause and Incomplete reaction resulted in the formation of white, lumpy substances that blocked the vent. Therefore, to ensure a complete reaction, this scheme is carried out under mesophilic conditions. During the deposition process, a large-scale reduction was adopted. In this way, during the process / Typically greater than 5, far exceeding the 1.5-3 level under high-temperature conditions, while maintaining a high catalyst strength. The usage amount and deposition pressure should be higher than 100 mbar, preferably higher than 200 mbar, and also higher than the 60-80 mbar level under high temperature conditions. Through the synergistic effect of these methods, both the deposition pressure and the deposition pressure are guaranteed. The growth process does not cause stomatal blockage and can also ensure growth rate The level.

[0053] This embodiment also provides a method based on medium temperature. A composite coating is deposited on the substrate using a method based on medium temperature as described above. The composite coating is prepared by a method comprising, from the inside out: a TiN layer bonded to the substrate; a TiCN layer deposited on the TiN layer; a bonding layer deposited on the TiCN layer; and a [missing information - likely a specific coating material] deposited on the bonding layer. layer;

[0054] The bonding layer is a composite structure of TiCNO, TiAlCNO, and an oxide-treated layer formed by CVD; The layer is pure The phase structure, and the composite coating is prepared by hot-wall chemical vapor deposition in a temperature range of 700°C to 900°C.

[0055] To verify the effectiveness and superiority of this solution, the following explanation is based on specific application examples and supplemented by multiple test comparisons.

[0056] WC-8% cemented carbide and special alloy steel (sheets, 30mm*70mm*0.7mm) were selected as the substrates. The cemented carbide cutting edge was passivated with a passivation value of 35μm. Both substrates were sandblasted and cleaned before coating to ensure the cleanliness of the substrate surface, and then placed in the furnace for coating at the same time.

[0057] The SCT-600TH hot-wall CVD coating oven was selected for coating.

[0058] Overall coating structure: From the substrate outwards, the coating composition along the coating growth direction is as follows: TiN layer → TiCN layer → bonding layer (TiCNO → TiAlCNO → oxidation treatment) → layer.

[0059] Application Example 1

[0060] This embodiment provides a method based on medium temperature. The method for preparing the composite coating is described, and the coating process is carried out. Specific parameters such as coating temperature, pressure, gas type and ratio are shown in Table 1. The deposition temperature is maintained at a constant 850℃ throughout the process.

[0061] Table 1. Coating growth process parameters for Application Example 1

[0062]

[0063] Application Example 2

[0064] This embodiment provides a method based on medium temperature. The method for preparing the composite coating is described, and the coating process is carried out. Specific parameters such as coating temperature, pressure, gas type and ratio are shown in Table 2. The deposition temperature is maintained at a constant 780℃ throughout the process.

[0065] Table 2 Coating growth process parameters for Application Example 2

[0066]

[0067] Coating performance results:

[0068] Adhesion: The coating adhesion was tested on the surface of WC cemented carbide by scratch testing with a load of 100N. Figure 2 The morphology of the scratch in Application Example 1 is shown under a stereomicroscope. Figure 3 For the acoustic signal and friction coefficient curve of the scratching process in Application Example 1, combined with Figure 2 and Figure 3 The acoustic signal indicates that the coating adhesion is 94N, reaching a high temperature. Equal level of binding force.

[0069] Figure 4 The image shows the morphology of the scratches in Application Example 2 under a stereomicroscope. The coating did not crack during the scratching process, and the adhesion strength reached 100N, achieving high temperature resistance. Equal level of binding force.

[0070] Reaction sufficiency: Visual inspection is performed. In application example 1, a special alloy steel sheet with dimensions of 30mm*70mm*0.7mm, such as... Figure 5 As shown, the appearance and color are uniform, similar to the black material prepared under high temperature conditions. Similar colors, no cause and The white powdery substance formed from incomplete reaction proves that the reaction process was complete at 850℃.

[0071] In application example 2, the cemented carbide cutting tools tested in the furnace, such as Figure 6 As shown, the fixture and blade did not produce any white powdery substance due to insufficient gas reaction, proving that the reaction process was complete at 780℃. The appearance and color were uniform overall, but the color was brownish.

[0072] Deposition rate: The fracture morphology of the coatings in Application Examples 1 and 2 was observed by scanning electron microscopy, the coating thickness was measured, and the deposition rate was calculated. The growth rate, as can be seen from the SEM images, is as follows: In application example 1, for example... Figure 7 As shown, With a thickness of approximately 5.1 μm and a growth rate of approximately 0.85 μm / h (greater than 0.6 μm / h), it meets the requirements for rapid industrial production.

[0073] In application example 2, such as Figure 8 As shown, With a thickness of approximately 5.2 μm and a growth rate of approximately 0.74 μm / h (greater than 0.6 μm / h), it also meets the requirements for rapid industrial production.

[0074] Phase structure analysis: Determined by XRD patterns Structure, through data comparison, XRD patterns show the coating's structure. Diffraction peaks and The standard cards (PDF-46-1212) form a corresponding relationship, such as Figure 9 and Figure 10 As shown, it is demonstrated that pure [material] was obtained under both 850°C and 780°C conditions. Phase structure.

[0075] This embodiment provides a method based on medium temperature. The composite coating and its preparation method can prepare TiCN+ with excellent adhesion under medium temperature conditions of 700-900 degrees Celsius. Base composite coating; with a wide range of applications.

[0076] Specifically, this scheme first designs a multi-layer transition structure including TiN, TiCN, and a composite bonding layer composed of TiCNO, TiAlCNO, and an oxide-treated layer. This structure is not a simple stacking, but rather each layer has a clear functional orientation: the TiN layer ensures initial bonding with the matrix; the TiCN layer acts as a supporting structure, providing hardness and toughness; and the composite bonding layer cleverly mitigates the bonding between TiCN and the matrix through a gradient change in its composition (gradually introducing Al and O elements while reducing C and N elements). The interfacial stress caused by the huge difference in lattice constant and thermal expansion coefficient between the layers results in stress on the top layer. The deposition provides a chemically and structurally more compatible substrate, supporting the achievement of high bonding strength at medium temperatures.

[0077] Secondly, this plan addresses... The reaction gas system of the layer was uniquely constructed. This specific combination of gases ( , HCl , The concentration window and its conclusions were drawn through extensive experimental exploration, not from existing high-temperature or medium-temperature processes. It can be easily obtained in phase processing through simple extrapolation or proportional scaling.

[0078] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for the production of a composite coating based on medium temperature The method comprises the following steps: ​ Deposition of TiN layer, TiCN layer, bonding layer and layer; The bonding layer comprises a TiCNO layer, a TiAlCNO layer and an oxidation treatment layer formed in sequence; The layer is deposited using a mixture gas comprising , HCl, , and with each gas volume fraction: 5 - 10 vol% , 0 - 3 vol% HCl, 0.3 - 2.5 vol% , 0.5 - 1 vol% , with the balance being ; The TiCNO layer is deposited using a mixture gas containing 2 - 4 vol% , 7 - 13 vol% , 7 - 13 vol% , 2 - 4 vol% CO, the balance being The TiAlCNO layer is deposited using a mixture gas containing 2 - 5 vol% , 5 - 10 vol% , 5 - 10 vol% , 2 - 5.5 vol% CO, 0.5 - 1.5 vol% , the balance being The oxidation treatment layer is deposited using a mixture gas containing 1 - 5 vol% , 0.5 - 3 vol% CO, 1 - 3 vol% HCI, the balance being ​ All layers are deposited in the temperature range, and the temperature is kept constant.

2. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that, The deposition pressure of the TiN layer is 100 - 500 mbar using a mixed gas containing 0.5 - 3 vol% , 25 - 40 vol% , the balance being H2. ​ 3. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that, The deposition pressure of the TiCN layer is 100 - 300 mbar using a mixed gas comprising 2 - 3.5 vol% , 1 - 2 vol% , 30 - 40 vol% , the balance being H2. ​ 4. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that, The deposition pressure of the TiCNO layer is 300-500 mbar. ​ 5. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that, The deposition pressure of the TiAlCNO layer is 100-300 mbar. ​ 6. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that The deposition pressure of the oxidation treatment layer is 50-150 mbar.

7. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that The The deposition pressure of the layer is 100 - 300 mbar, the growth speed .

8. A method of preparing a composite coating based on medium temperature The deposition temperature is 800-900℃. ​ 9. A method of preparing a composite coating based on medium temperature superconductors according to claim 1, characterized in that The substrate is cemented carbide or special alloy steel.

10. A composite coating based on medium temperature deposited on a substrate, characterized in that Using a method based on medium temperature as described in any one of claims 1-9 The composite coating was prepared by a method comprising, from the inside out: a TiN layer bonded to the substrate; a TiCN layer deposited on the TiN layer; a bonding layer deposited on the TiCN layer; and a [missing information - likely a specific coating material] deposited on the bonding layer. layer; The bonding layer is a composite structure of TiCNO, TiAlCNO and an oxidation treatment layer formed by a CVD method. The bonding layer is a pure phase structure, and the composite coating is prepared by a hot-wall chemical vapor deposition at a temperature range of 700-900°C.

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