A TiAlN / MAX phase multilayer composite coating, its preparation method and application

Abstract

This invention provides a TiAlN / MAX phase multilayer composite coating, its preparation method, and its application, belonging to the field of functional coating materials technology. The coating employs a nano-alternating multilayer structure of TiAlN and MAX phase layers, overcoming the bottleneck of traditional coatings' difficulty in simultaneously achieving hardness and toughness, significantly improving the coating's comprehensive mechanical properties and failure resistance. Under high-temperature conditions, highly reactive Al in the MAX phase in-situ generates a continuous, dense, and structurally stable Al2O3 protective film, achieving dynamic self-repair and anti-melting functions, greatly extending the service life of components. The coating also exhibits excellent thermal conductivity and stress relaxation ability, with outstanding thermal shock resistance and high-temperature stability. Its preparation method allows for precise control of the structural parameters and interfacial bonding state of each layer, with a stable process suitable for industrial production. This coating is applicable to metal components such as aluminum / magnesium alloy die-casting molds, demonstrating strong practicality and broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of functional coating materials technology, specifically to a TiAlN / MAX phase multilayer composite coating, its preparation method, and its application. Background Technology

[0002] Die-casting molds are core process equipment in the automotive, aerospace, and other industrial sectors for manufacturing complex parts. During service, their cavity surfaces must continuously withstand multiple stresses, including severe thermal shock from molten aluminum, interfacial chemical corrosion, liquid metal adhesion, and abrasive wear. The operating conditions are extremely harsh. Currently, H13 hot-work die steel is the mainstream base material for die-casting molds. These molds are prone to two typical failure modes during long-term use: First, the mold cavity surface undergoes a melting reaction with the molten aluminum, generating a brittle Fe-Al intermetallic compound layer. This causes irreversible erosion of the cavity and leads to difficulties in demolding. Second, under repeated cyclic thermal stress, thermal fatigue microcracks easily develop on the mold surface, which further develop into crazing. This not only seriously affects the forming quality of the casting but also significantly shortens the overall service life of the mold.

[0003] To improve the wear resistance and protective properties of mold surfaces, existing technologies mainly employ physical vapor deposition (PVD) to prepare hard ceramic coatings such as TiAlN and CrN on the mold surface. While these coatings possess high hardness and a certain degree of wear resistance, their typical columnar crystal growth structure and intrinsic brittleness make them highly susceptible to inducing penetrating microcracks under thermal shock conditions. Furthermore, these coatings have limited ability to block the diffusion of aluminum atoms along grain boundaries, making it difficult to effectively suppress the continuous occurrence of melting reactions. More critically, once existing hard coatings develop localized damage such as microcracks and melting pits during service, they lack an active repair mechanism. The damaged area will continuously expand with thermal cycling, eventually leading to coating peeling and failure.

[0004] In summary, existing surface protection technologies for die-casting molds, such as TiAlN and CrN hard ceramic coatings, cannot simultaneously achieve high hardness, high elasticity, resistance to melting and thermal fatigue, and lack in-situ self-repair capabilities for micro-damage during service. Therefore, they cannot meet the long-term protection requirements of die-casting molds under harsh operating conditions. Thus, developing a mold surface protective coating that can solve these technical problems has become a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a TiAlN / MAX phase multilayer composite coating, its preparation method, and its application. The TiAlN / MAX phase multilayer composite coating not only simultaneously exhibits high hardness, high elasticity, resistance to melting and thermal fatigue, but also possesses in-situ self-healing capabilities.

[0006] The specific technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a TiAlN / MAX phase multilayer composite coating, which is deposited on a metal substrate and is composed of a hard, wear-resistant TiAlN layer and a self-healing MAX phase layer that resists melting and repairs itself, periodically and alternately stacked along the coating thickness direction. The bottom and top layers are both TiAlN layers, and the total number of alternating stacked TiAlN and MAX phase layers is ≥5.

[0008] The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure, and its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane.

[0009] The MAX phase layer is composed of ternary aluminum-containing MAX phase ceramics, and its crystal structure is hexagonal crystal system and layered equiaxed crystal structure.

[0010] In one possible implementation, the grain size of the TiAlN layer is 20~100 nm.

[0011] In one possible implementation, the grain size of the MAX phase layer is 20~200 nm.

[0012] In one possible implementation, the thickness of the TiAlN layer is 0.5–3 μm.

[0013] In one possible implementation, the thickness of the MAX phase layer is 0.5–2 μm.

[0014] In one possible implementation, the total thickness of the TiAlN / MAX phase multilayer composite coating is 2–20 μm.

[0015] In one possible implementation, the total number of layers is 5 to 21.

[0016] In one possible implementation, the composition of the ternary aluminum-containing MAX phase ceramic is selected from any one of Ti2AlC, Ti4AlC3, and Ti3AlC2.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned TiAlN / MAX phase multilayer composite coating, comprising the following steps:

[0018] S1. Pretreatment: After cleaning, the metal substrate is cleaned to obtain a clean substrate;

[0019] S2, Deposit TiAlN layer: Deposit columnar nanocrystalline TiAlN layer with preferred orientation of (111) crystal plane on the surface of the clean substrate described in step S1 by arc ion plating;

[0020] S3, Deposit MAX phase precursor layer: Deposit MAX phase precursor layer on the surface of TiAlN layer described in step S2 by magnetron sputtering;

[0021] S4. Repeated deposition: Steps S2 and S3 are performed alternately to form a multilayer precursor coating on the clean substrate surface, consisting of alternating stacks of TiAlN layers and MAX phase precursor layers.

[0022] S5. Annealing treatment: The multilayer precursor coating described in step S4 is subjected to vacuum annealing treatment, which causes the MAX phase precursor layer to transform in situ into a MAX phase layer, thereby obtaining a TiAlN / MAX phase multilayer composite coating.

[0023] In one possible implementation, step S1 specifically includes: the metal substrate is sequentially subjected to mechanical polishing, ultrasonic cleaning, and ion cleaning to obtain a clean substrate.

[0024] In one possible implementation, the specific process of arc ion plating in step S2 is as follows: using a TiAl composite target as the cathode arc target, a TiAlN layer is prepared on the surface of the alloy substrate by arc ion plating in a nitrogen atmosphere, wherein the ratio of Ti to Al in the TiAl composite target is (33~73):(27~67), the deposition temperature is 100~300 ℃, the nitrogen flow rate is 550~650 sccm, the substrate bias voltage is -100 to -50 V, and the arc current is 50~70 A.

[0025] In one possible implementation, the specific process of magnetron sputtering in step S3 includes: using a TiAl composite target as the sputtering target, depositing the MAX phase precursor layer on the surface of the TiAlN layer by magnetron sputtering in a mixed gas composed of hydrocarbon reactive gas and inert gas. The elemental ratio of Ti to Al in the TiAl composite target is (30-40):(60-70), the inert gas flow rate is 150-200 sccm, the hydrocarbon reactive gas flow rate is 10-50 sccm, the substrate bias voltage is -200 to -50 V, and the sputtering power is 1.5-3.1 kW.

[0026] In one possible implementation, the vacuum degree of the vacuum annealing process is ≤5×10⁻⁶. -4 Pa, temperature 550~750 ℃, time 1~5 h.

[0027] Thirdly, the present invention provides a metal component, wherein the working surface of the metal component has the TiAlN / MAX phase multilayer composite coating.

[0028] In one possible implementation, the metal component is one of an aluminum / magnesium alloy die-casting mold, a shipborne compressor blade, and a nuclear power plant impeller.

[0029] The positive and progressive effects of this invention are as follows:

[0030] This invention provides a TiAlN / MAX phase multilayer composite coating, its preparation method, and its application. The TiAlN / MAX phase multilayer composite coating, by constructing a multilayer structure formed by alternating TiAlN and MAX phase layers, effectively solves the technical bottleneck of traditional coating systems where hardness and toughness are mutually constrained and cannot be simultaneously achieved, significantly improving the coating's comprehensive mechanical properties and failure resistance. Under high-temperature melt erosion or thermal cycling conditions, the highly reactive Al in the MAX phase preferentially migrates to the coating surface and micro-defects, undergoing in-situ oxidation to generate a continuous, dense, and structurally stable Al2O3 protective film. This process not only effectively resists high-temperature melt erosion but also endows the coating with unique active protection and dynamic self-healing capabilities, thereby extending the service life of critical components in harsh service environments by several times, solving the technical problems of easy failure and short lifespan of existing coatings. (111) The composite structure of a nano-columnar TiAlN layer with preferred crystal plane orientation and a nano-layered MAX phase layer with (000l) basal plane orientation significantly extends the atomic diffusion path. Simultaneously, it fully utilizes the excellent thermal conductivity and stress relaxation advantages of the MAX phase along its layers, effectively improving the coating's thermal shock resistance and high-temperature thermal stability, enabling the coating to adapt to harsh service conditions involving long-term high temperatures and alternating hot and cold temperatures. The preparation method of the TiAlN / MAX phase multilayer composite coating allows for precise control of the structural parameters and interface bonding state of each layer, achieving in-situ transformation of the MAX phase. The process exhibits good repeatability and high stability, facilitating large-scale industrial production. Applying the TiAlN / MAX phase multilayer composite coating to key metal components such as aluminum / magnesium alloy die-casting molds, shipborne compressor blades, and nuclear power plant impellers can significantly extend the service life of components, improve equipment reliability and safety, and demonstrates outstanding industrial practicality and broad application prospects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the multilayer composite coating in the embodiment.

[0032] Figure 2 The image shows the XRD diffraction pattern of the TiAlN / Ti2AlC multilayer composite coating prepared in Example 1.

[0033] Figure 3 This is a cross-sectional morphology diagram of the TiAlN / Ti2AlC multilayer composite coating prepared in Example 1.

[0034] Figure 4This is a TEM characterization image of the Ti2AlC layer prepared in Example 1.

[0035] Figure 5 The image shows a comparison of the nanoindentation mechanical properties of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0036] Figure 6 The graph shows a comparison of the hardness and toughness properties of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0037] Figure 7 This is a comparison chart showing the resistance to aluminum melt loss of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0038] Figure 8 The graph shows a comparison of the anti-melting kinetic properties of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0039] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0040] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0042] The specific technical solution of this invention is as follows:

[0043] In a first aspect, the present invention provides a TiAlN / MAX phase multilayer composite coating, which is deposited on a metal substrate and is composed of a hard, wear-resistant TiAlN layer and a self-healing MAX phase layer that resists melting and repairs itself, periodically and alternately stacked along the coating thickness direction. The bottom and top layers are both TiAlN layers, and the total number of alternating stacked TiAlN and MAX phase layers is ≥5.

[0044] The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure, and its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane.

[0045] The MAX phase layer is composed of ternary aluminum-containing MAX phase ceramics, and its crystal structure is hexagonal crystal system and layered equiaxed crystal structure.

[0046] In the TiAlN / MAX phase multilayer composite coating provided by this invention, the TiAlN layer has a Ti-Al-N ternary face-centered cubic structure, with Al atoms dissolved into the TiN lattice to form a solid solution strengthening effect, giving the coating high hardness. Simultaneously, the grains in the TiAlN layer grow in a columnar nanocrystal morphology with a preferred orientation of the (111) crystal plane. This columnar crystal structure forms a continuous load-bearing skeleton in the thickness direction, effectively resisting the indentation and wear of external loads, providing the coating with core high hardness and wear resistance. The alternating stacked TiAlN layers and MAX phase layers form a "hard-toughened" composite structure. The TiAlN layer provides a high elastic modulus, while the layered structure of the MAX phase layer avoids the brittle fracture common in single hard coatings through interfacial stress relaxation. This structural design allows the coating to maintain high hardness while significantly improving its elastic recovery capability, achieving a synergy between high hardness and high elastic modulus. The MAX phase layer has a hexagonal layered equiaxed crystal structure, in which Al atoms have high chemical activity. In high-temperature molten aluminum or molten metal environments, Al atoms preferentially react with oxygen to form a dense, continuous Al2O3 protective film in situ. This protective film possesses extremely high chemical stability, effectively blocking the diffusion and penetration of molten metal atoms, thereby significantly improving the coating's resistance to melting and damage. When microcracks or erosion pits develop in the coating during service, the highly reactive Al atoms in the MAX phase layer diffuse into the damaged area and react with oxygen in the environment to generate Al2O3. The newly generated Al2O3 fills the microcracks or erosion pits, achieving self-repair of localized damage, preventing crack propagation and further melting and damage, thus extending the coating's service life. The alternating stacking structure of TiAlN and MAX phase layers effectively blocks the continuous transmission of thermal stress within the coating. When the coating undergoes cyclic thermal cycling, the interfaces between the layers can act as stress release points, dispersing and relaxing thermal stress, preventing coating cracking and peeling caused by stress concentration. The layered equiaxed crystal structure of the MAX phase layer has excellent plastic deformation capabilities, enabling it to absorb and relax thermal stress through its own micro-deformation during thermal cycling. Meanwhile, the high stability of the TiAlN layer ensures the structural integrity of the coating at high temperatures, and the two work together to further improve the coating's resistance to thermal fatigue.

[0047] In one possible implementation, the grain size of the TiAlN layer is 20~100 nm. A grain size of 20~100 nm in the TiAlN layer can ensure high hardness of the coating while avoiding increased brittleness caused by excessively large grains, thus improving the coating's toughness and impact resistance.

[0048] In one possible implementation, the grain size of the MAX phase layer is 20~200 nm. A grain size of 20~200 nm allows the MAX phase layer to possess both good plastic deformation capability and structural stability, which is beneficial for crack deflection and stress relaxation, while also ensuring phase purity and self-healing efficiency at high temperatures.

[0049] In one possible implementation, the thickness of the TiAlN layer is 0.5–3 μm. A TiAlN layer thickness of 0.5–3 μm provides sufficient wear resistance and load-bearing capacity. Specifically, the thickness of the TiAlN layer can be any one or a range between 1 μm, 1.5 μm, 2 μm, and 2.5 μm.

[0050] In one possible implementation, the thickness of the MAX phase layer is 0.5–2 μm. A MAX phase layer thickness of 0.5–2 μm provides sufficient Al source for self-healing while ensuring strong interfacial bonding with the TiAlN layer. Specifically, the thickness of the MAX phase layer can be any one or any two of 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, and 1.8 μm.

[0051] In one possible implementation, the total thickness of the TiAlN / MAX phase multilayer composite coating is 2–20 μm. A total coating thickness of 2–20 μm balances protective performance with substrate adhesion, meeting the requirements for wear resistance and melt damage resistance during long-term service.

[0052] In one possible implementation, the total number of layers is 5 to 21. A total number of layers of 5 to 21 can form a sufficient alternating "hard-toughened" structure to effectively prevent crack propagation and thermal stress transfer. Specifically, the total number of layers can be any one of 5, 7, 9, 11, 13, 15, 17, and 19, or a range between any two.

[0053] In one possible implementation, the composition of the ternary aluminum-containing MAX phase ceramic is selected from any one of Ti2AlC, Ti4AlC3, and Ti3AlC2. These MAX phases, Ti2AlC, Ti4AlC3, and Ti3AlC3, all possess highly active Al atoms, enabling the in-situ formation of a dense Al2O3 protective film at high temperatures. This achieves excellent resistance to melting and self-healing properties, and also exhibits good structural compatibility with the TiAlN layer, resulting in stable interfacial bonding.

[0054] In one possible implementation, when the TiAlN / MAX phase multilayer composite coating comes into contact with high-temperature molten aluminum or magnesium, the temperature at which it self-repairs local damage is 500~1000 ℃. This temperature range of 500~1000 ℃ covers typical casting and hot-working conditions of aluminum / magnesium alloys, ensuring that in actual service environments, Al atoms in the MAX phase layer can effectively diffuse and generate Al2O3, achieving in-situ repair of microcracks and erosion pits, and improving the reliability and lifespan of the coating at high temperatures.

[0055] Secondly, the present invention provides a method for preparing the above-mentioned TiAlN / MAX phase multilayer composite coating, comprising the following steps:

[0056] S1. Pretreatment: After cleaning, the metal substrate is cleaned to obtain a clean substrate;

[0057] In step S1, the metal substrate is cleaned to effectively remove oil, impurities and oxide layers from the substrate surface, resulting in a clean and activated substrate surface. This improves the bonding strength between the coating and the substrate, avoids defects such as coating peeling and cracking caused by interface contamination, and provides a stable foundation for the uniform nucleation and growth of the coating in the future.

[0058] S2, Deposit TiAlN layer: Deposit columnar nanocrystalline TiAlN layer with preferred orientation of (111) crystal plane on the surface of the clean substrate described in step S1 by arc ion plating;

[0059] In step S2, an arc ion plating is used to deposit a columnar nanocrystalline TiAlN hard layer with a preferred orientation of (111) crystal plane. Taking advantage of the high ion energy, strong film-substrate bonding force and high coating density of arc ion plating, a TiAlN hard layer with fine grains, obvious preferred orientation and high hardness is obtained, which provides excellent wear resistance, load-bearing capacity and structural stability for the coating. At the same time, it serves as a skeleton layer of the multilayer structure to ensure the overall strength of the coating.

[0060] S3, Deposit MAX phase precursor layer: Deposit MAX phase precursor layer on the surface of TiAlN layer described in step S2 by magnetron sputtering;

[0061] In step S3, a uniformly composed and densely structured MAX phase precursor layer is deposited on the surface of the TiAlN layer, providing the compositional and structural basis for the subsequent in-situ phase transformation to generate the MAX phase. Magnetron sputtering is used to deposit the MAX phase precursor layer, allowing for precise control of its composition, thickness, and microstructure, ensuring uniform distribution of Ti, Al, and C (or N) elements. This provides a compositional guarantee for the subsequent in-situ generation of a high-purity MAX phase under vacuum annealing. Magnetron sputtering also results in low film deposition temperature and minimal damage, forming a smooth, continuous, and well-bonded multilayer interface with the TiAlN layer.

[0062] S4. Repeated deposition: Steps S2 and S3 are performed alternately to form a multilayer precursor coating on the clean substrate surface, consisting of alternating stacks of TiAlN layers and MAX phase precursor layers.

[0063] In step S4, by alternately depositing TiAlN layers and MAX phase precursor layers, a multilayer structure with periodic alternating stacking is constructed, which can introduce a large number of interlayer interfaces, effectively suppress crack propagation, release internal stress, and improve the coating toughness and thermal fatigue resistance; at the same time, the coating has both the high hardness of TiAlN and the high toughness and self-healing potential after the transformation of MAX phase precursor, achieving a strong and tough match.

[0064] S5. Annealing treatment: The multilayer precursor coating described in step S4 is subjected to vacuum annealing treatment, which causes the MAX phase precursor layer to transform in situ into a MAX phase layer, thereby obtaining a TiAlN / MAX phase multilayer composite coating.

[0065] In step S5, annealing is performed in a vacuum environment. On the one hand, this can eliminate the internal stress generated during the deposition process and improve the stability of the coating structure and the interfacial bonding force. On the other hand, it can cause the MAX phase precursor layer to undergo an in-situ solid-state phase transformation at a suitable temperature, transforming it into a hexagonal MAX phase ceramic layer with complete crystal structure and high purity, thus endowing the coating with anti-melting, high temperature resistance and in-situ self-healing function. The vacuum environment can prevent the coating from oxidizing at high temperatures, ensuring phase purity and service performance.

[0066] The method for preparing TiAlN / MAX phase multilayer composite coatings provided by this invention, through the synergistic cooperation of the above steps, can controllably prepare TiAlN / MAX phase multilayer composite coatings with uniform structure, clear interface, and excellent comprehensive performance. The resulting coatings also possess high hardness, high elastic modulus, excellent resistance to melting and damage, resistance to thermal fatigue, and high-temperature in-situ self-healing ability, making them suitable for harsh service environments such as high temperature, corrosion, and wear.

[0067] In one possible implementation, step S1 specifically includes the following process: the metal substrate is sequentially subjected to mechanical polishing, ultrasonic cleaning, and ion cleaning to obtain a clean substrate. The pretreatment process in step S1 employs a progressive approach of mechanical polishing, ultrasonic cleaning, and ion cleaning. Mechanical polishing makes the metal substrate surface smooth and flat, reducing surface roughness and defects, and providing a uniform nucleation substrate for subsequent coating deposition. Ultrasonic cleaning effectively removes organic and inorganic impurities such as oil and dust from the substrate surface, ensuring a clean and uncontaminated interface. Ion cleaning further activates the substrate surface, enhancing the bonding strength between the coating and the substrate, reducing defects such as coating cracking and peeling from the source, and ultimately obtaining a clean substrate that meets the deposition requirements.

[0068] In one possible implementation, the specific process of arc ion plating in step S2 is as follows: using a TiAl composite target as the cathode arc target, a TiAlN layer is prepared on the surface of an alloy substrate by arc ion plating in a nitrogen atmosphere. The ratio of Ti to Al in the TiAl composite target is (33~73):(27~67), the deposition temperature is 100~300 ℃, the nitrogen flow rate is 550~650 sccm, the substrate bias voltage is -100 to -50 V, and the arc current is 50~70 A. The arc ion plating process in step S2, using a TiAl composite target as the cathode arc target and controlling the ratio of Ti to Al to be (33~73):(27~67), ensures the stability of the TiAlN layer and provides a matching elemental basis for the subsequent formation of the MAX phase. Specifically, the elemental ratio of Ti to Al in the TiAl composite target is any one or any two of the following: 33:67, 40:60, 50:50, 60:40, and 73:27. The deposition temperature is 100~300 ℃, the nitrogen flow rate is 550~650 sccm, the substrate bias voltage is -100 to -50 V, and the arc current is 50~70 A. This parameter range allows for precise control of the growth state of the TiAlN layer, ensuring the formation of a dense columnar nanocrystalline structure with preferred orientation of the (111) crystal plane. This structure possesses high hardness, low internal stress, good wear resistance, and high-temperature stability, providing a reliable hard framework support for multilayer coatings.

[0069] In one possible implementation, the specific process of magnetron sputtering in step S3 includes: using a TiAl composite target as the sputtering target, depositing the MAX phase precursor layer on the surface of the TiAlN layer by magnetron sputtering in a mixed gas composed of hydrocarbon reactive gas and inert gas. The elemental ratio of Ti to Al in the TiAl composite target is (30-40):(60-70), the inert gas flow rate is 150-200 sccm, the hydrocarbon reactive gas flow rate is 10-50 sccm, the substrate bias voltage is -200 to -50 V, and the sputtering power is 1.5-3.1 kW. The magnetron sputtering method uses a TiAl composite target with a Ti:Al ratio of (30-40):(60-70) as the sputtering target. A MAX phase precursor layer is deposited in a mixed atmosphere of hydrocarbon reactive gas and inert gas. This method matches the required Ti / Al atomic ratio of the MAX phase, ensuring uniform composition of the precursor layer and providing a reliable compositional basis for subsequent in-situ vacuum annealing to generate a high-purity, structurally stable MAX phase layer. Specifically, the elemental ratio of Ti to Al in the TiAl composite target is any one or any two of the following: 35:65, 40:60, 50:50, and 33:67, preferably 2:1.3. The process parameters for magnetron sputtering are limited to: inert gas flow rate of 150~200 sccm, hydrocarbon reactive gas flow rate of 10~50 sccm, substrate bias voltage of -200 to -0 V, and sputtering power of 1.5~3.1 kW. This parameter range can achieve uniform deposition of the MAX phase precursor layer, ensuring that the Ti, Al, C and other elements in the precursor layer are evenly distributed and have a dense structure, and forming a flat and continuous bonding interface with the underlying TiAlN layer. This provides a solid compositional and structural basis for the in-situ generation of high-purity MAX phase during the subsequent vacuum annealing process.

[0070] Furthermore, the hydrocarbon reaction gas is methane or acetylene, and the inert gas is argon. Specifying methane or acetylene as the hydrocarbon reaction gas and argon as the inert gas provides a carbon source for the MAX phase precursor layer. The gas exhibits good stability and is easily controlled. Argon protects the target and coating from oxidation, ensures stable sputtering, reduces process costs, ensures uniform composition of the precursor layer, and achieves high film quality, thus meeting the requirements for subsequent in-situ MAX phase transformation.

[0071] In one possible implementation, the vacuum degree of the vacuum annealing process is ≤5×10⁻⁶. -4 Pa, temperature 550~750 ℃, time 1~5 h. Vacuum degree ≤5×10 -4The high vacuum environment can effectively prevent the coating from oxidizing during high-temperature annealing, ensuring the purity of the MAX phase and eliminating the formation of impurity phases; the annealing temperature of 550~750 ℃ ​​can promote the in-situ solid-state phase transformation of the MAX phase precursor layer, forming a hexagonal MAX phase layer with complete crystal structure and stable structure; the holding time of 1~5 h can effectively release the internal stress generated during the coating deposition process, further improve the bonding strength between the coating and the substrate and various functional layers, and optimize the grain morphology of the MAX phase, giving the coating excellent toughness, resistance to melting and loss and high-temperature in-situ self-healing function.

[0072] Thirdly, the present invention provides a metal component whose working surface has a multilayer composite coating of the TiAlN / MAX phase. By introducing this composite coating onto the working surface of the metal component, the wear resistance, melting resistance, thermal fatigue resistance, and high-temperature in-situ self-healing ability of the metal component can be significantly improved. This effectively solves the technical problems of traditional metal components being prone to failure and having short service life under harsh service conditions such as high temperature, corrosion, and high wear, greatly extending the service life of the metal component and broadening its application range. It can be widely used in hot work dies, aerospace, metallurgical equipment, and other fields.

[0073] In one possible implementation, the metal component is one of an aluminum / magnesium alloy die-casting mold, a shipborne compressor blade, and a nuclear power plant impeller. Applying a TiAlN / MAX phase multilayer composite coating to critical metal components such as aluminum / magnesium alloy die-casting molds, shipborne compressor blades, and nuclear power plant impellers—which are subjected to long-term high temperatures, wear, corrosion, and alternating loads—can fully leverage the coating's comprehensive advantages of high hardness, resistance to melting and damage, self-healing, and resistance to thermal fatigue. This significantly reduces the risk of component failure, extends service life, and improves the stability and safety of equipment operation, demonstrating significant engineering application value.

[0074] The above-described embodiments can be combined in any way to obtain the embodiments of this application.

[0075] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0076] Example 1

[0077] This embodiment provides a TiAlN / Ti2AlC multilayer composite coating, which is deposited on an H13 hot work die steel substrate. It is composed of a hard and wear-resistant TiAlN layer and a self-healing Ti2AlC layer that resists melting and is stacked alternately along the coating thickness direction. The bottom and top layers are both TiAlN layers. The total number of alternating stacked TiAlN and Ti2AlC layers is 5. The thickness of the TiAlN layer is 1.5 μm. The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure. Its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane. The grain size is 25 nm. The thickness of the Ti2AlC layer is 0.5 μm. The crystal structure of the Ti2AlC layer is a hexagonal crystal system and a layered equiaxed crystal structure. The grain size is 30 μm. The aluminum element in the Ti2AlC layer can be oxidized in situ to generate dense Al2O3.

[0078] The TiAlN / Ti2AlC2 multilayer composite coating in this embodiment is prepared through the following steps:

[0079] S1. Preprocessing:

[0080] S1.1 Mechanical polishing: The surface of the H13 hot work die steel substrate to be deposited is subjected to gradient mechanical polishing treatment. After dry grinding with metallographic sandpaper, it is finely polished with diamond polishing paste until the roughness Ra of the surface of the H13 hot work die steel substrate to be deposited is ≤0.05 μm. After polishing, the surface polishing debris is blown away with a high-pressure air gun.

[0081] S1.2 Ultrasonic cleaning: The H13 hot work die steel substrate that has been mechanically polished in step S1.1 is placed in acetone and ultrasonically cleaned for 15 min to remove organic oil contaminants on the surface; then the substrate is placed in anhydrous ethanol and ultrasonically cleaned for 10 min to replace and remove residual acetone; after cleaning, the substrate is placed in an 80 ℃ vacuum drying oven and dried for 30 min to remove residual solvent on the surface.

[0082] S1.3 Ion Cleaning: The dried H13 hot work die steel substrate from step S1.2 is clamped onto the fixture in the vacuum coating chamber. The chamber is closed and the chamber heating device is activated to raise the substrate temperature to 150 ℃. The chamber is then evacuated to a background vacuum of 3.0 × 10⁻⁶. -3 At step 1, 99.99% pure argon gas is introduced into the chamber at a flow rate of 34 sccm. The linear anodic ion source is turned on and the ion source current is set to 0.2 A. At the same time, a DC negative bias voltage of -200 V is applied to the substrate. The ionized argon ions are used to perform ion etching on the substrate surface to be deposited for 30 min. After etching is completed, the linear anodic ion source and the substrate bias voltage are turned off in sequence, and the argon gas supply is stopped to maintain the vacuum state of the chamber.

[0083] S2. Deposition of TiAlN layer: After ion cleaning is completed and the vacuum coating chamber is kept under vacuum, the arc ion plating deposition system is started; nitrogen gas with a purity ≥99.999% is introduced into the vacuum coating chamber, and the nitrogen gas flow rate is adjusted to 600 sccm; a DC negative bias voltage of -75 V is applied to the H13 steel substrate, using a TiAl (33:67) element composite target as the cathode arc target. The arc current of the cathode arc target is set to 60 A, and the arc discharge is started, causing the TiAl (33:67) element composite target to ionize. The target ions and nitrogen ions undergo a gas phase reaction on the substrate surface and are deposited; the above process parameters are kept stable throughout the process, and deposition continues until a TiAlN layer of the preset thickness is formed on the substrate surface; after deposition is completed, the arc current and substrate bias voltage are turned off in sequence, the introduction of high-purity nitrogen gas is stopped, and the chamber is kept under vacuum.

[0084] S3. Deposition of the MAX phase precursor layer: After completing the TiAlN layer deposition and maintaining a vacuum in the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 25 sccm respectively; apply a -100°C pressure to the H13 steel substrate. With a DC negative bias voltage of V, a TiAl (2:1.3) elemental composite target is used as the sputtering target. The sputtering power of the sputtering target is set to 2.5kW, and magnetron sputtering is turned on. Argon ions bombard the TiAl composite target to generate target ions. The target ions react with methane gas ions in the gas phase on the surface of the TiAlN layer and are deposited to form a Ti-Al-C precursor layer. All the above process parameters are kept stable throughout the process, and sputtering is continued to deposit a Ti-Al-C precursor layer of a preset thickness on the surface of the TiAlN layer. After the deposition is completed, the sputtering power and substrate bias voltage are turned off in sequence, and the introduction of argon and methane is stopped to maintain the vacuum state of the chamber.

[0085] S4. Repeated deposition: After the first TiAlN layer and the first Ti-Al-C precursor layer are deposited sequentially, the vacuum state of the vacuum coating chamber is maintained, and the process steps of depositing the TiAlN layer in step S2 and depositing the MAX phase precursor layer in step S3 are repeated to perform multi-layer alternating deposition. Finally, a deposited TiAlN / Ti-Al-C multi-layer composite coating with 3 TiAlN layers and 2 Ti-Al-C precursor layers stacked alternately is formed on the surface of the H13 steel substrate, and the top layer of the coating is the TiAlN layer.

[0086] S5. Annealing Treatment: The prepared deposited TiAlN / Ti-Al-C multilayer composite coating sample is stably placed in the constant temperature zone of the tube furnace. The furnace door is closed and sealed. The vacuum pumping system of the tube furnace is started to evacuate the furnace until the vacuum level inside the furnace reaches 5×10⁻⁶. -4Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 700 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 700 ℃ and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 2 h to allow the Ti-Al-C precursor layer to undergo a full in-situ phase transformation to generate Ti2AlC. After the holding time was completed, all heating units of the tube furnace were turned off, the vacuum pumping system was stopped, and the furnace was kept sealed to allow the sample to cool naturally to room temperature. After the temperature dropped to room temperature, the furnace door was opened and the sample was taken out to obtain the TiAlN / Ti2AlC multilayer composite coating.

[0087] Example 2

[0088] This embodiment provides a TiAlN / Ti3AlC2 multilayer composite coating, which is deposited on an H13 steel hot work die steel substrate. It is composed of a hard and wear-resistant TiAlN layer and a self-healing Ti3AlC2 layer that resists melting and is stacked alternately along the coating thickness direction. The bottom and top layers are both TiAlN layers. The total number of alternating stacked TiAlN and Ti3AlC2 layers is 5. The thickness of the TiAlN layer is 2 μm. The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure. Its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane. The grain size is 25 nm. The thickness of the Ti3AlC2 layer is 0.8 μm. The crystal structure of the Ti3AlC2 layer is a hexagonal crystal system and a layered equiaxed crystal structure. The grain size is 30 nm. The aluminum element in the Ti3AlC2 layer can be oxidized in situ to generate dense Al2O3.

[0089] The TiAlN / Ti3AlC2 multilayer composite coating in this embodiment is prepared through the following steps:

[0090] S1. Preprocessing:

[0091] S1.1 Mechanical polishing: The surface of the H13 hot work die steel substrate to be deposited is subjected to gradient mechanical polishing treatment. After dry grinding with metallographic sandpaper, it is finely polished with diamond polishing paste until the roughness Ra of the surface of the H13 hot work die steel substrate to be deposited is ≤0.05 μm. After polishing, the surface polishing debris is blown away with a high-pressure air gun.

[0092] S1.2 Ultrasonic cleaning: The H13 hot work die steel substrate that has been mechanically polished in step S1.1 is placed in acetone and ultrasonically cleaned for 15 min to remove organic oil contaminants on the surface; then the substrate is placed in anhydrous ethanol and ultrasonically cleaned for 10 min to replace and remove residual acetone; after cleaning, the substrate is placed in an 80 ℃ vacuum drying oven and dried for 30 min to remove residual solvent on the surface.

[0093] S1.3 Ion Cleaning: The dried H13 hot work die steel substrate from step S1.2 is clamped onto the fixture in the vacuum coating chamber. The chamber is closed and the chamber heating device is activated to heat the substrate to 100 ℃. The chamber is then evacuated to a background vacuum of 3.0 × 10⁻⁶. -3 At step 1, 99.99% pure argon gas is introduced into the chamber at a flow rate of 34 sccm. The linear anodic ion source is turned on and the ion source current is set to 0.2 A. At the same time, a DC negative bias voltage of -200 V is applied to the substrate. The ionized argon ions are used to perform ion etching on the substrate surface to be deposited for 30 min. After etching is completed, the linear anodic ion source and the substrate bias voltage are turned off in sequence, and the argon gas supply is stopped to maintain the vacuum state of the chamber.

[0094] S2. Deposition of TiAlN layer: After ion cleaning is completed and the vacuum coating chamber is kept under vacuum, the arc ion plating deposition system is started; nitrogen gas with a purity ≥99.999% is introduced into the vacuum coating chamber, and the nitrogen gas flow rate is adjusted to 600 sccm; a DC negative bias voltage of -75 V is applied to the H13 steel substrate, using a TiAl (33:67) element composite target as the cathode arc target. The arc current of the cathode arc target is set to 60 A, and the arc discharge is started, causing the TiAl (33:67) element composite target to ionize. The target ions and nitrogen ions undergo a gas phase reaction on the substrate surface and are deposited; the above process parameters are kept stable throughout the process, and deposition continues until a TiAlN layer of the preset thickness is formed on the substrate surface; after deposition is completed, the arc current and substrate bias voltage are turned off in sequence, the introduction of high-purity nitrogen gas is stopped, and the chamber is kept under vacuum.

[0095] S3. Deposition of the MAX phase precursor layer: After completing the TiAlN layer deposition and maintaining the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 7.5 sccm respectively; apply a DC negative bias of -100 V to the H13 steel substrate, using a TiAl (2:1.3) element composite target as the sputtering target; set the sputtering power of the sputtering target to 2.5kW, start magnetron sputtering, so that argon ions bombard the TiAl composite target to generate target ions, and the target ions react with methane gas ions in the gas phase on the TiAlN layer surface and deposit, forming TiAl x -C precursor layer; maintaining all the above process parameters stable throughout the process, continuously sputtering and depositing to form a TiAl layer of the predetermined thickness on the TiAlN surface. x -C precursor layer; after deposition, the sputtering power and substrate bias are turned off in sequence, and the introduction of argon and methane is stopped to maintain the chamber vacuum.

[0096] S4. Repeated deposition: After completing the first TiAlN layer and the first TiAl... x After the sequential deposition of the -C precursor layer, the vacuum coating chamber is kept under vacuum. The process steps of depositing the TiAlN layer in step S2 and the MAX phase precursor layer in step S3 are repeated to perform multi-layer alternating deposition, ultimately forming 3 TiAlN layers and 2 TiAl phases on the surface of the H13 steel substrate. x -C precursor layers alternately stacked in a deposited state of TiAlN / TiAl x -C multilayer composite coating, with the top layer being a TiAlN layer.

[0097] S5. Annealing treatment: The prepared deposited TiAlN / TiAl x The -C multilayer composite coating sample was placed stably in the constant temperature zone of the tube furnace. The furnace door was closed and sealed. The vacuum pumping system of the tube furnace was started to evacuate the furnace until the vacuum level inside the furnace reached 5×10⁻⁶. -4 Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 700 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 700 ℃ and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 2 h to allow TiAl to... x -C precursor layer undergoes full in-situ phase transformation to generate Ti3AlC2MAX phase; after the holding time is completed, all heating units of the tube furnace are turned off, the vacuum pumping system is stopped, the furnace chamber is kept sealed, and the sample is allowed to cool naturally to room temperature with the tube furnace; after the temperature drops to room temperature, the furnace door is opened and the sample is taken out, thus obtaining TiAlN / Ti3AlC2 multilayer composite coating.

[0098] Example 3

[0099] This embodiment provides a TiAlN / Ti2AlC multilayer composite coating, which is deposited on an H13 steel hot work die steel substrate. It is composed of a hard and wear-resistant TiAlN layer and a self-healing Ti2AlC layer that resists melting and repairs itself, which are periodically stacked alternately along the coating thickness direction. The bottom and top layers are both TiAlN layers, and the total number of alternating stacked TiAlN and Ti2AlC layers is 11. The thickness of the TiAlN layer is 1.2 μm, and the crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure. Its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane, and the grain size is 25 nm. The thickness of the Ti2AlC layer is 0.5 μm, and the crystal structure of the Ti2AlC layer is a hexagonal crystal system, a layered equiaxed crystal structure, and the grain size is 30 nm. The aluminum element in the Ti2AlC layer can be oxidized in situ to generate dense Al2O3.

[0100] The TiAlN / Ti2AlC2 multilayer composite coating in this embodiment is prepared through the following steps:

[0101] S1. Preprocessing:

[0102] S1.1 Mechanical polishing: The surface of the H13 hot work die steel substrate to be deposited is subjected to gradient mechanical polishing treatment. After dry grinding with metallographic sandpaper, it is finely polished with diamond polishing paste until the roughness Ra of the surface of the H13 hot work die steel substrate to be deposited is ≤0.05 μm. After polishing, the surface polishing debris is blown away with a high-pressure air gun.

[0103] S1.2 Ultrasonic cleaning: The H13 hot work die steel substrate that has been mechanically polished in step S1.1 is placed in acetone and ultrasonically cleaned for 15 min to remove organic oil contaminants on the surface; then the substrate is placed in anhydrous ethanol and ultrasonically cleaned for 10 min to replace and remove residual acetone; after cleaning, the substrate is placed in an 80 ℃ vacuum drying oven and dried for 30 min to remove residual solvent on the surface.

[0104] S1.3 Ion Cleaning: The dried H13 hot-work die steel substrate (not included in step S1.2) is clamped onto the fixture in the vacuum coating chamber. The chamber is closed, and the chamber heating device is activated to raise the substrate temperature to 100 ℃. The chamber is then evacuated to a background vacuum of 3.0 × 10⁻⁶. -3 At Pa, 99.99% pure argon gas is introduced into the chamber, and the argon gas flow rate is controlled at 34 sccm. The linear anodic ion source is turned on, and the ion source current is set to 0.2 A. At the same time, a DC negative bias voltage of -200 V is applied to the substrate. The ionized argon ions are used to perform ion etching on the substrate surface to be deposited, and the etching time is 40 min. After etching is completed, the linear anodic ion source and the substrate bias voltage are turned off in sequence, the argon gas introduction is stopped, and the chamber is kept in a vacuum state.

[0105] S2. Deposition of TiAlN layer: After ion cleaning is completed and the vacuum coating chamber is kept under vacuum, the arc ion plating deposition system is started; nitrogen gas with a purity ≥99.999% is introduced into the vacuum coating chamber, and the nitrogen gas flow rate is adjusted to 550 sccm; a DC negative bias voltage of -90 V is applied to the H13 steel substrate, and a TiAl (33:67) element composite target is used as the cathode arc target. The arc current of the cathode arc target is set to 60 A, and the arc discharge is started, causing the TiAl (33:67) element composite target to be ionized. The target ions and nitrogen ions react in the gas phase on the substrate surface and are deposited; the above process parameters are kept stable throughout the process, and deposition continues until a TiAlN layer of the preset thickness is formed on the substrate surface; after deposition is completed, the arc current and substrate bias voltage are turned off in sequence, the introduction of high-purity nitrogen gas is stopped, and the chamber is kept under vacuum.

[0106] S3. Deposition of the MAX phase precursor layer: After completing the TiAlN layer deposition and maintaining a vacuum in the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 25 sccm, respectively; apply a -100V DC negative bias to the H13 steel substrate, using a TiAl (2:1.3) element composite target as the sputtering target; set the sputtering power of the sputtering target to 2.5. kW, start magnetron sputtering to bombard the TiAl composite target with argon ions to generate target ions. The target ions react with methane gas ions in the gas phase on the surface of the TiAlN layer and deposit to form a Ti-Al-C precursor layer. Keep all the above process parameters stable throughout the process and continue sputtering to deposit a Ti-Al-C precursor layer of a preset thickness on the surface of the TiAlN layer. After the deposition is completed, turn off the sputtering power and the substrate bias voltage in sequence, stop the introduction of argon and methane, and maintain the chamber vacuum state.

[0107] S4. Repeated deposition: After the first TiAlN layer and the first Ti-Al-C layer are deposited sequentially, the vacuum state of the vacuum coating chamber is maintained, and the process steps of depositing the TiAlN layer in step S2 and depositing the MAX phase precursor layer in step S3 are repeated to perform multi-layer alternating deposition. Finally, a deposited TiAlN / Ti-Al-C multi-layer composite coating with 6 TiAlN layers and 5 Ti-Al-C precursor layers stacked alternately is formed on the surface of the H13 steel substrate, and the top layer of the coating is the TiAlN layer.

[0108] S5. Annealing Treatment: The prepared deposited TiAlN / Ti-Al-C multilayer composite coating sample is stably placed in the constant temperature zone of the tube furnace. The furnace door is closed and sealed. The vacuum pumping system of the tube furnace is started to evacuate the furnace until the vacuum level inside the furnace reaches 5×10⁻⁶. -4 Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 700 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 700 ℃ and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 2 h to allow the Ti-Al-C precursor layer to undergo a full in-situ phase transformation to generate Ti2AlC. After the holding time was completed, all heating units of the tube furnace were turned off, the vacuum pumping system was stopped, and the furnace was kept sealed to allow the sample to cool naturally to room temperature. After the temperature dropped to room temperature, the furnace door was opened and the sample was taken out to obtain the TiAlN / Ti2AlC multilayer composite coating.

[0109] Example 4

[0110] This embodiment provides a TiAlN / Ti2AlC multilayer composite coating, which is deposited on an H13 steel hot work die steel substrate. It is composed of a hard and wear-resistant TiAlN layer and a self-healing Ti2AlC layer that resists melting and is stacked alternately along the coating thickness direction. The bottom and top layers are both TiAlN layers. The total number of alternating stacked TiAlN and Ti2AlC layers is 5. The thickness of the TiAlN layer is 1.5 μm. The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure. Its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane. The grain size is 25 nm. The thickness of the Ti2AlC layer is 0.8 μm. The crystal structure of the Ti2AlC layer is a hexagonal crystal system and a layered equiaxed crystal structure. The grain size is 30 nm. The aluminum element in the Ti2AlC layer can be oxidized in situ to generate dense Al2O3.

[0111] The TiAlN / Ti2AlC2 multilayer composite coating in this embodiment is prepared through the following steps:

[0112] S1. Preprocessing:

[0113] S1.1 Mechanical polishing: The surface of the H13 hot work die steel substrate to be deposited is subjected to gradient mechanical polishing treatment. After dry grinding with metallographic sandpaper, it is finely polished with diamond polishing paste until the roughness Ra of the surface of the H13 hot work die steel substrate to be deposited is ≤0.05 μm. After polishing, the surface polishing debris is blown away with a high-pressure air gun.

[0114] S1.2 Ultrasonic cleaning: The H13 hot work die steel substrate that has been mechanically polished in step S1.1 is placed in acetone and ultrasonically cleaned for 15 min to remove organic oil contaminants on the surface; then the substrate is placed in anhydrous ethanol and ultrasonically cleaned for 10 min to replace and remove residual acetone; after cleaning, the substrate is placed in an 80 ℃ vacuum drying oven and dried for 30 min to remove residual solvent on the surface.

[0115] S1.3 Ion Cleaning: The dried H13 hot work die steel substrate from step S1.2 is clamped onto the fixture in the vacuum coating chamber. The chamber is closed and the chamber heating device is activated to raise the substrate temperature to 150 ℃. The chamber is then evacuated to a background vacuum of 3.0 × 10⁻⁶. -3 At step 1, 99.99% pure argon gas is introduced into the chamber at a flow rate of 34 sccm. The linear anodic ion source is turned on and the ion source current is set to 0.2 A. At the same time, a DC negative bias voltage of -200 V is applied to the substrate. The ionized argon ions are used to perform ion etching on the substrate surface to be deposited for 30 min. After etching is completed, the linear anodic ion source and the substrate bias voltage are turned off in sequence, and the argon gas supply is stopped to maintain the vacuum state of the chamber.

[0116] S2. Deposition of TiAlN layer: After ion cleaning is completed and the vacuum coating chamber is kept under vacuum, the arc ion plating deposition system is started; nitrogen gas with a purity ≥99.999% is introduced into the vacuum coating chamber, and the nitrogen gas flow rate is adjusted to 650 sccm; a DC negative bias voltage of -75 V is applied to the H13 steel substrate, and a TiAl (33:67) element composite target is used as the cathode arc target. The arc current of the cathode arc target is set to 60 A, and the arc discharge is started, causing the TiAl (33:67) element composite target to be ionized. The target ions and nitrogen ions react in the gas phase on the substrate surface and are deposited; the above process parameters are kept stable throughout the process, and deposition continues until a TiAlN layer of the preset thickness is formed on the substrate surface; after deposition is completed, the arc current and substrate bias voltage are turned off in sequence, the introduction of high-purity nitrogen gas is stopped, and the chamber is kept under vacuum.

[0117] S3. Deposition of the MAX phase precursor layer: After completing the TiAlN layer deposition and maintaining the vacuum in the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 25 sccm respectively; apply a substrate bias voltage of -150V to the H13 steel substrate, using a TiAl (2:1.3) element composite target as the sputtering target; set the sputtering power of the sputtering target to 2... kW, start magnetron sputtering to bombard the TiAl composite target with argon ions to generate target ions. The target ions react with methane gas ions in the gas phase on the surface of the TiAlN layer and deposit to form a Ti-Al-C precursor layer. Keep all the above process parameters stable throughout the process and continue sputtering to deposit a Ti-Al-C precursor layer of a preset thickness on the surface of the TiAlN layer. After the deposition is completed, turn off the sputtering power and the substrate bias voltage in sequence, stop the introduction of argon and methane, and maintain the chamber vacuum state.

[0118] S4. Repeated deposition: After the first TiAlN layer and the first Ti-Al-C precursor layer are deposited sequentially, the vacuum state of the vacuum coating chamber is maintained, and the process steps of depositing the TiAlN layer in step S2 and depositing the MAX phase precursor layer in step S3 are repeated to perform multi-layer alternating deposition. Finally, a deposited TiAlN / Ti-Al-C multi-layer composite coating with 3 TiAlN layers and 2 Ti-Al-C precursor layers stacked alternately is formed on the surface of the H13 steel substrate, and the top layer of the coating is the TiAlN layer.

[0119] S5. Annealing Treatment: The prepared deposited TiAlN / Ti-Al-C multilayer composite coating sample is stably placed in the constant temperature zone of the tube furnace. The furnace door is closed and sealed. The vacuum pumping system of the tube furnace is started to evacuate the furnace until the vacuum level inside the furnace reaches 5×10⁻⁶. -4Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 750 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 750 ℃ ​​and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 3 h to allow the Ti-Al-C precursor layer to undergo a full in-situ phase transformation to generate Ti2AlC. After the holding time was completed, all heating units of the tube furnace were turned off, the vacuum pumping system was stopped, and the furnace was kept sealed to allow the sample to cool naturally to room temperature. After the temperature dropped to room temperature, the furnace door was opened and the sample was taken out to obtain the TiAlN / Ti2AlC multilayer composite coating.

[0120] Example 5

[0121] This embodiment provides a TiAlN / Ti4AlC3 multilayer composite coating, which is deposited on an H13 hot work die steel substrate. It is composed of a hard and wear-resistant TiAlN layer and a self-healing Ti4AlC3 layer that resists melting and is stacked alternately along the coating thickness direction. The bottom and top layers are both TiAlN layers. The total number of alternating stacked TiAlN and Ti4AlC3 layers is 5. The thickness of the TiAlN layer is 2 μm. The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure. Its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane. The grain size is about 30 nm. The thickness of the Ti4AlC3 layer is 1.2 μm. The crystal structure of the Ti4AlC3 layer is a hexagonal crystal system and a layered equiaxed crystal structure. The grain size is 35 nm. The aluminum element in the Ti4AlC3 layer can be oxidized in situ to generate dense Al2O3.

[0122] The TiAlN / Ti4AlC3 multilayer composite coating in this embodiment is prepared through the following steps:

[0123] S1. Pretreatment: Same as step S1 in Example 1.

[0124] S2, Deposit TiAlN layer: Same as step S2 in Example 1.

[0125] S3. Deposition of the MAX phase precursor layer: After completing the TiAlN layer deposition and maintaining the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 35 sccm respectively; apply a -100V DC negative bias voltage to the H13 steel substrate, using a TiAl (2:1.3) element composite target as the sputtering target; set the sputtering power of the sputtering target to 2.5 kW, start magnetron sputtering, so that argon ions bombard the TiAl composite target to generate target ions. The target ions and methane gas ions undergo a gas phase reaction on the TiAlN layer surface and are deposited to form TiAl x -C precursor layer; maintaining all the above process parameters stable throughout the process, continuously sputtering and depositing to form a TiAl layer of the predetermined thickness on the TiAlN surface. x -C precursor layer; after deposition, the sputtering power and substrate bias are turned off in sequence, and the introduction of argon and methane is stopped to maintain the chamber vacuum.

[0126] S4. Repeated deposition: After completing the first TiAlN layer and the first TiAl... x After the sequential deposition of the -C precursor layer, the vacuum coating chamber is kept under vacuum. The process steps of depositing the TiAlN layer in step S2 and the MAX phase precursor layer in step S3 are repeated to perform multi-layer alternating deposition, ultimately forming 3 TiAlN layers and 2 TiAl phases on the surface of the H13 steel substrate. x -C precursor layers alternately stacked in a deposited state of TiAlN / TiAl x -C multilayer composite coating, with the top layer being a TiAlN layer.

[0127] S5. Annealing treatment: The prepared deposited TiAlN / TiAl x The -C multilayer composite coating sample was placed stably in the constant temperature zone of the tube furnace. The furnace door was closed and sealed. The vacuum pumping system of the tube furnace was started to evacuate the furnace until the vacuum level inside the furnace reached 5×10⁻⁶. -4 Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 720 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 720 ℃ and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 2.5 h to allow TiAl to... x-C precursor layer undergoes full in-situ phase transformation to generate Ti4AlC3MAX phase; after the holding time is completed, all heating units of the tube furnace are turned off, the vacuum pumping system is stopped, the furnace chamber is kept sealed, and the sample is allowed to cool naturally to room temperature with the tube furnace; after the temperature drops to room temperature, the furnace door is opened and the sample is taken out, thus obtaining TiAlN / Ti4AlC3 multilayer composite coating.

[0128] Comparative Example 1

[0129] This comparative example provides a single-layer MAX phase coating, which is prepared by the following steps:

[0130] D1. Pretreatment: Same as step S1 in Example 1.

[0131] D2. Deposition of the MAX phase precursor layer: After ion cleaning and maintaining a vacuum in the vacuum coating chamber, start the magnetron sputtering deposition system; simultaneously introduce argon gas with a purity ≥99.99% and methane with a purity ≥99.99% into the vacuum coating chamber, adjusting the argon gas flow rate to 200 sccm and the methane flow rate to 25 sccm, respectively; apply a -100V DC negative bias to the H13 steel substrate, using a TiAl (2:1.3) element composite target as the sputtering target; set the sputtering power of the sputtering target to 2.5. kW, start magnetron sputtering to bombard the TiAl composite target with argon ions to generate target ions. The target ions react with methane gas ions in the gas phase on the surface of the TiAlN layer and deposit to form a Ti-Al-C precursor layer. Keep all the above process parameters stable throughout the process and continue sputtering to deposit a Ti-Al-C precursor layer of a preset thickness on the surface of the TiAlN layer. After the deposition is completed, turn off the sputtering power and the substrate bias voltage in sequence, stop the introduction of argon and methane, and maintain the chamber vacuum state.

[0132] D3. Annealing treatment: The prepared Ti-Al-C precursor layer sample is placed stably in the constant temperature zone of the tube furnace. The furnace door is closed and sealed. The vacuum pumping system of the tube furnace is started to evacuate the furnace until the vacuum level inside the furnace reaches 5×10⁻⁶. -4 Below Pa; start the heating program of the tube furnace, setting the heating rate to 10 ℃ / min; when the temperature reaches 700 ℃, stop the heating program and start the constant temperature holding program, maintaining the temperature at 700 ℃ and a vacuum degree ≤5×10 -4 The sample was kept at a temperature of Pa for 2 h to allow the Ti-Al-C precursor layer to undergo a full in-situ phase transformation to generate Ti2AlC. After the holding time was completed, all heating units of the tube furnace were turned off, the vacuum pumping system was stopped, and the furnace was kept sealed to allow the sample to cool naturally to room temperature. After the temperature dropped to room temperature, the furnace door was opened and the sample was taken out to obtain the Ti2AlC MAX phase coating.

[0133] Comparative Example 2

[0134] This comparative example provides a single-layer TiAlN coating, which is prepared through the following steps:

[0135] D1. Pretreatment: Same as step S1 in Example 1.

[0136] D2. Deposition of TiAlN layer: After ion cleaning and maintaining a vacuum in the vacuum coating chamber, start the arc ion plating deposition system; introduce nitrogen gas with a purity ≥99.999% into the vacuum coating chamber, and adjust the nitrogen gas flow rate to 600 sccm; apply a DC negative bias voltage of -75 V to the H13 steel substrate, using a TiAl(33:67) element composite target as the cathode arc target. Set the arc current of the cathode arc target to 60 A, start the arc discharge, and ionize the TiAl(33:67) element composite target. The target ions and nitrogen ions react in the gas phase on the substrate surface and are deposited; keep the above process parameters stable throughout the process, and continue deposition until a TiAlN layer of the preset thickness is formed on the substrate surface; after deposition is completed, sequentially turn off the arc current and substrate bias voltage, stop the introduction of high-purity nitrogen gas, open the chamber door and take out the sample to obtain the TiAlN coating.

[0137] Performance Testing and Result Analysis

[0138] The coatings obtained in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to performance tests, and the test results are analyzed as follows:

[0139] Figure 1 This is a schematic diagram of the structure of the multilayer composite coating in an embodiment of the present invention. Figure 1 As shown, the bottom substrate is a metal matrix such as H13 steel, titanium alloy, or cemented carbide, which serves as the load-bearing base for the coating. The bottom TiAlN layer (TiAlN(Base)) is deposited directly on the substrate surface, providing initial hard and wear-resistant protection. The alternating intermediate layers consist of MAX phase layers and TiAlN layers periodically stacked alternately. Figure 1 The text uses “…” to indicate a multi-layered structure that can be repeatedly stacked as needed, with a total number of layers ranging from 2 to 20, preferably 5. The top TiAlN layer (TiAlN (Top)) is located on the outermost side of the coating and serves as the direct contact layer under service conditions, providing high hardness, wear resistance, and resistance to abrasive wear. The TiAlN layer exhibits a columnar nanocrystalline structure, with grains preferentially growing along the thickness direction, having a preferred orientation of the (111) crystal plane, and a grain size of 20–100 nm. This structure endows the coating with high hardness, high wear resistance, and good high-temperature stability. The MAX phase layer exhibits a layered equiaxed crystal structure with a grain size of 20–200 nm, belonging to the hexagonal crystal system. This structure enables the MAX phase layer to combine the toughness of metals with the high-temperature stability of ceramics, making it the core functional layer for achieving synergistic strength and toughness, resistance to melting, and self-repair in the coating.

[0140] Figure 2 The image shows the XRD diffraction pattern of the TiAlN / Ti2AlC multilayer composite coating prepared in Example 1. Figure 2 It can be seen that, in addition to the matrix diffraction peaks, the coating exhibits obvious diffraction peaks near 2θ = 36.2°, 42.3°, and 61.5°, corresponding to the (111), (200), and (220) crystal planes of the TiAlN face-centered cubic structure, respectively. Among them, the (111) peak has the highest intensity, indicating that the TiAlN layer grows in a columnar crystal structure with a (111) preferred orientation. At the same time, characteristic diffraction peaks belonging to the Ti2AlC MAX phase, such as (100) / (101), (004), and (103), appear near 2θ = 34.5°, 38.2°, and 41.8°, and no impurity phase peaks such as TiC and TiAl are observed, proving that after vacuum annealing, the Ti-Al-C precursor layer has been successfully transformed in situ into a well-crystallized Ti2AlC MAX phase layer. This result proves that the preparation method in Example 1 of this invention successfully obtained a multilayer composite coating system of alternating TiAlN and Ti2AlC.

[0141] Figure 3 This is a cross-sectional morphology image of the TiAlN / Ti2AlC multilayer composite coating prepared in Example 1. Figure 3 As can be seen, the composite coating prepared in Example 1 consists of TiAlN layer → Ti2AlC layer → TiAlN layer → Ti2AlC layer → TiAlN layer from the substrate upwards, forming an alternating stacked structure of 3 TiAlN layers and 2 Ti2AlC layers, with the top layer being a TiAlN layer. The thickness of each layer is uniform, and the interface between the TiAlN layer and the Ti2AlC layer is clear and continuous, without obvious cracks, pores, or peeling, indicating a tight bond between the coating and the substrate, as well as between the functional layers.

[0142] Figure 4 This is a TEM characterization image of the Ti2AlC layer prepared in Example 1. Figure 4The image consists of three parts: the main image on the left is a bright-field TEM image of the Ti2AlC MAX phase, the upper right corner is a magnified high-resolution TEM (HRTEM) image, and the lower right corner is a selected area electron diffraction (SAED) image. The main image on the left shows that the Ti2AlC MAX phase exhibits a typical layered nanocrystalline structure, with the lamellae arranged parallel along a specific direction, uniform interlayer spacing, and lamellae size in the nanometer scale, exhibiting the structural characteristics of hexagonal layered equiaxed crystals. This nanolayered structure is the structural basis for the MAX phase to possess both metallic toughness and ceramic high-temperature stability. The magnified high-resolution TEM (HRTEM) image in the upper right corner is a magnified high-resolution lattice fringe image obtained from the white box area in the main image on the left. The clear lattice fringes in the image indicate that the Ti2AlC MAX phase is a well-crystallized single crystal or polycrystalline structure, without obvious amorphous or impurity phases. The measured interplanar spacing d = 2.58 Å is highly consistent with the standard interplanar spacing of the (101) crystal plane of the Ti2AlC MAX phase, further verifying the phase composition and crystal structure of the MAX phase. The selected area electron diffraction (SAED) pattern in the lower right corner consists of a series of concentric diffraction rings, indicating that the Ti2AlC MAX phase is a polycrystalline structure with randomly distributed grain orientations. The positions of the diffraction rings correspond perfectly to the standard diffraction data ((101), (104), and (110) crystal planes) of the Ti2AlC MAX phase, with no additional impurity phase diffraction rings, proving that the MAX phase has high phase purity and no impurity phases such as TiC and Al4C3 are formed. The uniform intensity distribution of the diffraction rings indicates that the Ti2AlC MAX phase has small and uniform grain size, consistent with the bright-field TEM morphology observation results.

[0143] Figure 5 This is a comparison chart of the nanoindentation mechanical properties of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 5It can be seen that the maximum load of the TiAlN / Ti2AlC multilayer composite coating in Example 1 is approximately 135 mN, which is significantly higher than the maximum load of the single TiAlN layer in Comparative Example 2 (approximately 110 mN) and the maximum load of the single Ti2AlC layer in Comparative Example 1 (approximately 60 mN), indicating that the coating of Example 1 has better hardness and load-bearing capacity. Furthermore, during the unloading stage, the curve slope of Example 1 is steeper, and the residual indentation depth is smaller, indicating stronger elastic recovery and superior toughness. The single Ti2AlC layer in Comparative Example 1 exhibits a clear "step" during the loading stage, indicating significant plastic deformation and weak load-bearing capacity; while the single TiAlN layer in Comparative Example 2 has better load-bearing capacity, its elastic recovery is inferior to that of Example 1; whereas the curve of Example 1 is smooth and continuous, possessing both high hardness and good toughness, demonstrating a synergistic effect of strength and toughness. This indicates that the TiAlN / Ti2AlC multilayer composite coating prepared in Example 1 possesses both higher hardness than the single TiAlN coating and better toughness than the single Ti2AlC coating, solving the bottleneck problem of traditional hard coatings being "hard and brittle". This superior mechanical property stems from the alternating stacked structure of TiAlN hard layer and MAX phase toughening layer. The TiAlN layer provides high hardness and wear resistance, while the MAX phase layer effectively improves the fracture toughness and impact resistance of the coating by inducing crack deflection, branching and passivation.

[0144] Figure 6 This is a comparison chart of the hardness and toughness properties of the coatings obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 6 It can be seen that the hardness of the single-layer Ti2AlC MAX phase coating in Comparative Example 1 is only 13.73 GPa, and the elastic modulus is 382.61 GPa, exhibiting typical characteristics of soft ceramics with MAX phase. The hardness of the single-layer TiAlN coating in Comparative Example 2 reaches 34.47 GPa, and the elastic modulus is 513.27 GPa, consistent with the typical mechanical properties of hard PVD coatings. The hardness of the TiAlN / Ti2AlC multilayer composite coating in Example 1 is 34.61 GPa, comparable to, or even slightly higher than, that of a single-layer TiAlN. Introducing a softer Ti2AlC layer to form a multilayer structure with the TiAlN layer did not reduce the overall hardness of the coating; instead, it achieved a hardness level comparable to that of a single-layer TiAlN. This indicates that the hard TiAlN layer in the multilayer structure bears the main load-bearing function, the insertion of the Ti2AlC layer did not destroy the intrinsic high hardness of the TiAlN layer, and the interface strengthening effect may have a slight effect on improving the hardness.

[0145] Elastic modulus is a material's ability to resist elastic deformation. In coating systems, a higher elastic modulus is generally associated with higher resistance to crack initiation. The TiAlN / Ti2AlC multilayer composite coating prepared in Example 1 has an elastic modulus as high as 601.78 GPa, which is not only higher than that of the single-layer Ti2AlC in Comparative Example 1, but also significantly higher than that of the single-layer TiAlN in Comparative Example 2. In the hard / soft alternating multilayer structure of Example 1, the MAX phase layer is constrained by the hard TiAlN layers on both sides, which changes its elastic deformation behavior and leads to an increase in the overall modulus.

[0146] Figure 7 The figures show a comparison of the anti-aluminum melt loss performance of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2. Specifically, (a) shows a comparison of the surface macroscopic morphology of the TiAlN / Ti2AlC multilayer composite coating in Example 1 after different immersion times in aluminum; (b) shows a comparison of the surface macroscopic morphology of the single-layer TiAlN coating in Comparative Example 2 after different immersion times in aluminum; and (c) shows a comparison of the surface macroscopic morphology of the single-layer Ti2AlC MAX phase coating in Comparative Example 1 after different immersion times in aluminum. The immersion times were 3 h, 6 h, and 10 h, respectively. Figure 7 It can be seen that in Comparative Example 2, the monolayer TiAlN showed obvious cracks and localized peeling after immersion in aluminum for 3 hours, with the aluminum liquid penetrating into the coating; after 6 hours, the peeling area expanded significantly, the coating failed over a large area, and the aluminum liquid came into direct contact with the substrate; after 10 hours, the coating almost completely peeled off, and the substrate was severely corroded, indicating that the monolayer TiAlN could not effectively prevent the penetration and erosion of aluminum liquid. In Comparative Example 1, after immersion in aluminum for 3 hours, a large number of spherical melting points formed by aluminum liquid wetting appeared on the coating surface of the monolayer Ti2AlC, and some areas had been penetrated; after 6 hours, the melting points merged and expanded, the integrity of the coating was destroyed, and the penetration of aluminum liquid intensified; after 10 hours, the melting points merged and expanded, the integrity of the coating was destroyed, and the penetration of aluminum liquid intensified, indicating that the monolayer Ti2AlC MAX phase has a certain resistance to melting loss, but its hardness is low and it is difficult to withstand the erosion of aluminum liquid for a long time. In contrast, the TiAlN / Ti2AlC multilayer composite coating in Example 1 remained intact after immersion in aluminum for 3 and 6 hours, with only a few melting points appearing locally after 10 hours. The main structure of the coating remained continuous, without large-area failure, demonstrating excellent resistance to aluminum melt damage. This result indicates that the present invention, through the periodic alternating stacking design of the TiAlN hard layer and the Ti2AlC MAX phase layer, not only utilizes the high density of the TiAlN layer to block the diffusion of aluminum melt, but also utilizes the high-temperature self-healing properties of the MAX phase layer to generate a dense Al2O3 protective film in situ, effectively blocking aluminum melt penetration while filling microcracks and achieving self-repair. This result directly confirms the excellent resistance to melt damage and self-healing ability of the TiAlN / MAX phase multilayer composite coating provided by the present invention in a high-temperature molten metal environment.

[0147] Figure 8The graph shows a comparison of the anti-melting kinetic properties of the coatings prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 8 The horizontal axis represents the etching time (in hours), and the vertical axis on the left represents the reference scale for the increase in coating mass in Comparative Example 1 and Comparative Example 2 (in g / cm³). 2 The right-hand vertical axis represents the reference scale for the increase in coating mass in Example 1 (unit: g / cm). 2 The value represents the degree of reaction and penetration between the molten aluminum and the coating. In Example 1, the TiAlN / Ti2AlC multilayer composite coating showed a weight gain 1-2 orders of magnitude lower than that of the single-layer TiAlN in Comparative Example 2 and the single-layer Ti2AlC MAX phase layer in Comparative Example 1 during the 3-6 h etching stage. This demonstrates that the multilayer structure of the TiAlN / Ti2AlC multilayer composite coating and the self-healing MAX phase layer in Example 1 provide excellent protection from the initial stage. The high density of the TiAlN layer blocks the physical penetration of the molten aluminum, while the Al2O3 oxide film generated by the MAX phase layer blocks the chemical reaction channels of Al. The two work synergistically to achieve near-zero weight gain. After 10 h of etching, the TiAlN / Ti2AlC multilayer composite coating in Example 1 showed a mass gain of only 0.03209 g / cm². Although it increased slightly over time, it was still much lower than that of the two comparative examples, demonstrating excellent long-term resistance to melting and loss.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A TiAlN / MAX phase multilayer composite coating, deposited on a metal substrate, characterized in that, It is composed of a hard, wear-resistant TiAlN layer and a self-healing MAX phase layer that resists melting and is periodically stacked alternately along the coating thickness direction, with both the bottom and top layers being the TiAlN layer, and the total number of alternating stacked TiAlN layers and MAX phase layers being ≥5; wherein, The crystal structure of the TiAlN layer is a Ti-Al-N ternary face-centered cubic structure, and its grains grow in the form of columnar nanocrystals with preferred orientation of (111) crystal plane. The MAX phase layer is composed of ternary aluminum-containing MAX phase ceramics, which have a hexagonal crystal system and a layered equiaxed crystal structure. The composition of the ternary aluminum-containing MAX phase ceramics is selected from any one of Ti2AlC, Ti4AlC3 and Ti3AlC2.

2. The TiAlN / MAX phase multilayer composite coating according to claim 1, characterized in that, The grain size of the TiAlN layer is 20~100 nm; And / or, the grain size of the MAX phase layer is 20~200 nm; And / or, the thickness of the TiAlN layer is 0.5–3 μm; And / or, the thickness of the MAX phase layer is 0.5–2 μm; And / or, the total thickness of the TiAlN / MAX phase multilayer composite coating is 2 to 20 μm; And / or, the total number of layers is 5 to 21.

3. A method for preparing a TiAlN / MAX phase multilayer composite coating according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Pretreatment: After cleaning, the metal substrate is cleaned to obtain a clean substrate; S2, Deposit TiAlN layer: Deposit columnar nanocrystalline TiAlN layer with preferred orientation of (111) crystal plane on the surface of the clean substrate described in step S1 by arc ion plating; S3, Deposit MAX phase precursor layer: Deposit MAX phase precursor layer on the surface of TiAlN layer described in step S2 by magnetron sputtering; S4. Repeated deposition: Steps S2 and S3 are performed alternately to form a multilayer coating precursor consisting of alternating stacks of TiAlN layers and MAX phase precursor layers on the clean substrate surface. S5. Annealing treatment: The multilayer precursor coating described in step S4 is subjected to vacuum annealing treatment, which causes the MAX phase precursor layer to transform in situ into a MAX phase layer, thereby obtaining a TiAlN / MAX phase multilayer composite coating.

4. The method for preparing the TiAlN / MAX phase multilayer composite coating according to claim 3, characterized in that, The specific process of step S1 includes: the metal substrate is sequentially subjected to mechanical polishing, ultrasonic cleaning and ion cleaning to obtain a clean substrate.

5. The method for preparing the TiAlN / MAX phase multilayer composite coating according to claim 4, characterized in that, The specific process of arc ion plating in step S2 is as follows: using a TiAl composite target as the cathode arc target, a TiAlN layer is prepared on the surface of the alloy substrate by arc ion plating in a nitrogen atmosphere. The ratio of Ti to Al in the TiAl composite target is (33~73):(27~67), the deposition temperature is 100~300 ℃, the nitrogen flow rate is 550~650 sccm, the substrate bias voltage is -100 to -50 V, and the arc current is 50~70 A.

6. The method for preparing the TiAlN / MAX phase multilayer composite coating according to claim 4, characterized in that, The specific process of magnetron sputtering in step S3 includes: using a TiAl composite target as the sputtering target, the MAX phase precursor layer is deposited on the surface of the TiAlN layer by magnetron sputtering in a mixed gas composed of hydrocarbon reactive gas and inert gas. The elemental ratio of Ti to Al in the TiAl composite target is (30-40):(60-70), the inert gas flow rate is 150-200 sccm, the hydrocarbon reactive gas flow rate is 10-50 sccm, the substrate bias voltage is -200 to -50 V, and the sputtering power is 1.5-3.1 kW.

7. The method for preparing the TiAlN / MAX phase multilayer composite coating according to claim 4, characterized in that, The vacuum degree of the vacuum annealing treatment is ≤5×10 -4 Pa, temperature is 550~750 ℃, time is 1~5 h.

8. A metal component, characterized in that, The working surface of the metal component has a TiAlN / MAX phase multilayer composite coating as described in any one of claims 1-4.

9. The metal component according to claim 8, characterized in that, The metal component is one of the following: aluminum / magnesium alloy die-casting mold, shipborne compressor blade, and nuclear power plant impeller.

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