An isomeric high-entropy sandwich gradient coating and a preparation method and application thereof

Abstract

The application relates to a homomeric high-entropy sandwich gradient coating and a preparation method and application thereof. The preparation method comprises the following steps: preparing a high-entropy alloy layer on the surface of a substrate by adopting a laser directional energy deposition technology; then depositing a high-entropy alloy composite material layer with controllable ceramic phase content gradient layer by layer by adding high-entropy alloy mixed powder containing ceramic phase nonmetal components; and constructing a high-entropy ceramic film on the surface of the high-entropy alloy composite material layer by using an embedding process, so as to obtain the homomeric high-entropy sandwich gradient coating. The application drives the directional diffusion of ceramic phase nonmetal elements to the inside of the high-entropy alloy composite material layer by a chemical potential gradient, releases the interface stress concentration, and generates in-situ reaction, so that a ceramic film with high compactness and high thermal stability is generated, and the core protection functions of surface oxidation resistance and wear resistance are realized. The prepared coating can be applied to the fields of aerospace, biomedical treatment, high-end mechanical manufacturing and the like which are faced with heavy load, wear and corrosion.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy alloy coating technology, specifically relating to a homologous heterogeneous high-entropy sandwich gradient coating, its preparation method, and its application. Background Technology

[0002] Coating technology is a key component of materials surface engineering, endowing substrate materials with protective and functional properties. With the development of fields such as high-end equipment manufacturing, the service environment of coatings is becoming increasingly extreme and complex, creating an urgent need for multifunctional integration, long service life, and high environmental adaptability. Traditional coatings follow the "single-function coating" approach, such as glass coatings that only provide heat insulation (see Chinese patent application CN121342343A) and anti-corrosion coatings that only block corrosion (see Chinese patent application CN121450199A), etc. A singular performance dimension cannot cope with multi-factor coupled failure environments. For example, compressor blades not only face high salt spray corrosion but also endure the cyclical alternation of high-temperature thermal corrosion (see Chinese patent application CN117026156A). Aerospace carbon-carbon composite anti-oxidation coatings need to possess both high-temperature oxidation resistance and thermal stress fatigue resistance (see Chinese patent application CN118955182A). Diamond-like carbon (DLC) coatings, due to their excellent tribological properties (see Chinese patent application CN121362951A), were once widely considered to have significant application potential in the field of load-bearing artificial joints. Although this coating exhibits excellent performance in in vitro simulation tests, in the complex physiological environment of vivo, interface failure caused by the silicon-based adhesive layer often leads to large-scale coating peeling. Single coating materials are no longer sufficient to meet practical needs.

[0003] This practical application demand has driven a paradigm shift in coating technology from "single-function coatings" to "multi-function coatings." The core design concept of multi-function coating systems lies in achieving comprehensive performance that is difficult to achieve with a single coating through the functional differentiation and synergistic effect of different material layers. This concept has been applied in many fields, but the problem of synergistic failure at heterogeneous interfaces still exists. For example, in the field of medical devices, HA / titanium gradient coatings prepared by plasma spraying or simultaneously doped with antibacterial elements such as silver and copper can alleviate interfacial stress and achieve dual functions of bone integration and antibacterial properties (see Chinese patent applications CN114164393A, CN119587761A, CN105019004A). However, in simulated body fluid environments, the uncontrollable release of metal ions from the antibacterial layer can easily lead to accelerated degradation of the coating, damage to the dense structure of the corrosion-resistant layer, and thus shorten the protective life of the coating. Thermal barrier coating systems also have similar problems. The porous YSZ ceramic layer is responsible for high-temperature insulation, and the metal anti-oxidation bonding layer (MCrAlY) can selectively oxidize Al and enhance the bonding force with the matrix (see Chinese patent applications CN121517941A, CN121496399A). However, the porous structure will open convenient channels for oxygen permeation, causing the metal bonding layer to fail prematurely. Such heterogeneous coatings with simple composites fail to achieve a continuous gradient transition of interfacial components or structures, resulting in abrupt changes in composition and properties at the interface, which can easily lead to instability of interfacial bonding.

[0004] Unlike the design approach of simply splicing different materials in heterogeneous coatings, current research focuses on constructing homogeneous gradient coatings to overcome the technical bottleneck of interface instability in heterogeneous coatings. This involves continuous gradient changes in composition and structure to further eliminate abrupt changes at the interlayer interface, achieving a smooth transition in composition and properties, thereby effectively reducing the risk of interface failure. For example, in the preparation of high-entropy alloy ceramic gradient coatings, the content of non-metallic components in the ceramic phase is controlled layer by layer to construct a gradient structure coating (see Chinese patent applications CN114150203A and CN116288214A) to achieve continuous gradual changes in the ceramic phase composition between layers and alleviate interface abrupt changes. However, existing homogeneous gradient coatings still limit the control of interface structure to the macroscopic scale, failing to achieve atomic-level structural control and rearrangement. This results in low crystal structure compatibility at the interface, easily inducing structural distortion. The internal stress induced by this distortion accumulates continuously, eventually leading to interface debonding and subsequent failure behaviors such as coating cracking and peeling.

[0005] In summary, existing multifunctional coatings have not fundamentally solved the core technical problem of functional failure caused by interlayer interface instability. This bottleneck not only restricts the large-scale application of multifunctional coatings in key components of high-end equipment, but also remains a core technical challenge that urgently needs to be overcome in the field of surface engineering. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a homologous heterogeneous high-entropy sandwich gradient coating.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned homologous high-entropy sandwich gradient coating.

[0008] Another object of the present invention is to provide the application of the above-mentioned homologous heterogeneous high-entropy sandwich gradient coating.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a homologue heterogeneous high-entropy sandwich gradient coating includes the following steps:

[0011] (1) Preparation of high-entropy alloy layer: Laser directed energy deposition (L-DED) technology is used to induce non-equilibrium rapid solidification of the molten pool by a high-energy laser beam to prepare a high-entropy alloy layer on the substrate surface, forming a strong and tough skeleton structure;

[0012] (2) Preparation of high-entropy alloy composite material layer: Laser directed energy deposition (L-DED) technology is used to prepare a high-entropy alloy composite material layer with controllable ceramic phase content gradient by layering high-entropy alloy mixed powder containing different proportions of ceramic phase non-metallic components on the surface of the high-entropy alloy layer prepared in step (1) in order of increasing ceramic phase non-metallic component content. This layer serves as the key connection layer between the surface high-entropy ceramic film and the high-entropy alloy bottom layer.

[0013] (3) In-situ self-generation preparation of high-density high-entropy ceramic film: Using the thermal diffusion driving mechanism of the embedding infiltration process, a high-entropy ceramic film is constructed on the surface of the high-entropy alloy composite material layer. The non-metallic elements of the ceramic phase are driven to diffuse into the interior of the high-entropy alloy composite material layer through the chemical potential gradient, releasing the interfacial stress concentration and causing in-situ reaction, generating a high-density, high-thermal-stability high-entropy ceramic film, realizing the core protective functions of surface anti-oxidation and wear resistance.

[0014] Preferably, the substrate in step (1) includes, but is not limited to, medical alloys, high-temperature alloys, or steel materials. For example, titanium alloys, CoCrNi alloys, iron-based alloys, etc. The substrate is first cut, polished, cleaned, and dried, and then a high-entropy alloy layer is prepared on its surface. The cleaning can be ultrasonic cleaning, and the drying is preferably done at 100°C for 2 hours.

[0015] Preferably, the mass percentages of each component in the high-entropy alloy layer in step (1) are: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, and Mo 5.16~7.43%. The raw materials for the high-entropy alloy layer are all spherical powders with a particle size of 10~200μm, and more preferably, the particle size range is 45~105μm.

[0016] More preferably, the mass percentage of each component in the high-entropy alloy layer is: Ti 39wt%, Zr 39wt%, Nb 10wt%, Ta 5wt%, Mo 7wt%.

[0017] Preferably, in the laser directional energy deposition process described in step (1), a coaxial powder feeding method is used, with a powder feeding speed of 20g / min; the laser power is 1900~2500W, and the scanning speed is 6~10mm / s.

[0018] Preferably, the thickness of the high-entropy alloy layer in step (1) is controlled at 0.2~1mm.

[0019] Preferably, the high-entropy alloy mixed powder in step (2) includes high-entropy alloy powder and ceramic phase non-metallic components, wherein the ceramic phase non-metallic components are one or more of B, C, Si, and N; more preferably, Si.

[0020] More preferably, the mass ratio of the high-entropy alloy powder to the ceramic phase non-metallic component is 99.5~99.9wt%:0.1~0.5wt%.

[0021] More preferably, the high-entropy alloy powder, by mass percentage, comprises: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, and Mo 5.16~7.43%; the most preferred mass percentage is: Ti 39wt%, Zr 39wt%, Nb 10wt%, Ta 5wt%, and Mo 7wt%. All the high-entropy alloy powders are spherical powders with a particle size of 10~200μm, and more preferably, the particle size range is 45~105μm.

[0022] Preferably, in the laser directional energy deposition process described in step (2): a coaxial powder feeding method is used, the powder feeding speed is 20g / min; the laser power is 1900~2500W, and the scanning speed is 6~10mm / s.

[0023] Preferably, the high-entropy alloy composite material layer in step (2) has ≥3 layers, and the thickness of each layer is controlled between 0.2 and 1 mm.

[0024] Preferably, in step (2), the sample prepared in step (1) is first polished, cleaned and dried, and then a high-entropy alloy composite material layer is prepared on its surface.

[0025] More preferably, the cleaning is ultrasonic cleaning, and the drying is drying at 100°C for 2 hours.

[0026] Preferably, the mass percentage of each component of the infiltrator used in the embedding and infiltration process in step (3) is: Si 20~45%, NaF 5~10%, Y2O3 1~3%, with the balance being ZrO2; wherein the particle size of each component powder of the infiltrator is 100~200μm.

[0027] More preferably, the mass percentage of each component of the penetrant is: Si 25%, NaF 6%, Y2O3 2%, and the balance is ZrO2.

[0028] More preferably, the penetrant is prepared by ball milling, and the process parameters include: a ball-to-material mass ratio of 2 to 4:1, a ball milling time of 2 to 8 hours, and a ball milling speed of 300 to 400 r / min; the most preferred process parameters include: a ball-to-material mass ratio of 3:1, a ball milling time of 4 hours, and a ball milling speed of 400 r / min.

[0029] Preferably, the embedding process in step (3) includes raising the temperature to 1000~1200℃ and holding it for 0.5~2h to promote the directional diffusion of Si elements into the interior of the high-entropy alloy composite material layer and to cause an in-situ reaction, thereby generating a high-entropy ceramic film with high density and high thermal stability.

[0030] Preferably, the embedding and infiltration process in step (3) is carried out under a protective atmosphere, with a heating rate of 5°C / min and a cooling method of in-furnace cooling.

[0031] Preferably, in step (3), the sample prepared in step (2) is first polished, cleaned and dried, and then a high-entropy ceramic membrane is constructed by embedding and infiltration process.

[0032] More preferably, the cleaning is ultrasonic cleaning, and the drying is drying at 60°C for 2 hours.

[0033] The coating prepared by this invention can be applied to fields facing heavy loads, wear, and corrosion, such as aerospace, biomedicine, and high-end machinery manufacturing.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] This invention constructs a multi-layered gradient structure coating with sandwich-like characteristics, consisting of a high-density, wear-resistant, high-entropy ceramic film on the surface, a ductile-brittle transition layer composed of a ceramic phase-high-entropy alloy interpenetrating network in the middle, and a toughened high-entropy alloy load-bearing layer at the bottom. This exhibits a continuous mechanical property gradient of "ultra-hard wear resistance - ductile-brittle transition - tough load-bearing," adapting to complex service environments with multiple coupled factors. Based on the gradient distribution of parameters such as elastic modulus and coefficient of thermal expansion, the coating can effectively smooth abrupt changes in interfacial stress, achieving a smooth performance transition from the wear-resistant surface to the tough substrate. The middle layer acts as a "biomimetic ligament," connecting toughness and hardness; the bottom layer provides structural support and stress transmission; and the surface layer undertakes core wear-resistant protection. This biomimetic gradient design forms a synergistic mechanism of "rigidity and flexibility," effectively inhibiting the initiation and propagation of penetrating cracks, improving the structural stability and service reliability of the coating, and achieving long-term protection of the substrate. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the concept of biomimicry.

[0037] Figure 2 The XRD patterns of the high-entropy alloy layers prepared in step one of Examples 1-3 are shown in the figure. 1900W, 2100W, and 2300W represent Examples 1, 2, and 3, respectively. It can be seen from the figure that the high-entropy alloy bottom layer prepared in step one is a single BCC phase.

[0038] Figure 3 The XRD patterns of the high-entropy alloy composite material layers prepared in step two of Examples 1-3 are shown in the figure. 1900W, 2100W, and 2300W represent Examples 1, 2, and 3, respectively. It can be seen from the figure that the high-entropy alloy composite material layer prepared in step two has a BCC structure and is a mixture of high-entropy alloy matrix phase and ceramic phase.

[0039] Figure 4 The XRD patterns of the high-entropy ceramic films prepared in step three of Examples 1-3 are shown. 1100℃ for 0.5h, 1000℃ for 1h, and 1200℃ for 2h represent Examples 1, 2, and 3, respectively. It can be seen from the figures that different processes have a significant impact on the phase composition of the high-entropy ceramic films.

[0040] Figure 5 The images show the surface morphology of the high-entropy alloy composite material layers prepared in step two of Examples 1-3. 1900W 6mm / s, 2100W 8mm / s, and 2300W 10mm / s represent Examples 1, 2, and 3, respectively. It can be seen from the images that the coating interfaces are well bonded.

[0041] Figure 6The image shows the microhardness at the interface between the high-entropy alloy composite material layer and the matrix prepared in step two of Examples 1-3. 1900W, 2100W, and 2300W represent Examples 1, 2, and 3, respectively. It can be seen from the image that a uniform hard coating is obtained.

[0042] Figure 7 The following are data images of the high-entropy sandwich gradient coating prepared in Example 1, including (a) scratch morphology; (b) magnified view of region 1; (c) magnified view of region 2; (d) magnified view of region 3; (e) elastic modulus curve; and (f) acoustic emission signal as a function of load. It can be seen from the figures that the coating has good adhesion.

[0043] Figure 8 This is a schematic diagram of the structure of the homologous heterogeneous high-entropy sandwich gradient coating of the present invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0045] Inspired by the biomimetic concept of the gradient distribution of fiber tubes in the cross-section of bamboo in nature, such as Figure 1 As shown, this provides a natural biomimetic inspiration for material surface protection: in the cross-sectional structure of bamboo, three layers are distributed sequentially from the outside to the inside: the outer green layer, the inner flesh layer, and the inner yellow layer. The fiber bundles exhibit a gradient distribution characteristic of "dense on the outside and sparse on the inside," with the density decreasing from the epidermis to the pith, achieving a continuous transition in hardness and toughness, thus resisting wear and dissipating stress. Through this continuous hierarchical gradient design, the organic unity of protective function and structural support is achieved, providing a reference for the design of protective coatings on alloy surfaces.

[0046] Bionic Concept: Inspired by the gradient protective structure of bamboo, this invention integrates high-entropy alloy system design, in-situ self-generation technology, and gradient material concepts to propose a "homogeneous yet heterogeneous" high-entropy sandwich structure coating design principle: A single high-entropy alloy system material serves as the common foundation, with the metal element selected as a strong ceramic phase-forming element to prepare a pure high-entropy alloy layer as the bottom layer; subsequently, strong ceramic phase-forming non-metallic elements are introduced to form a high-entropy alloy ceramic composite material intermediate layer dominated by BCC solid solution ceramic phase; finally, through a thermal diffusion mechanism, the ceramic phase non-metallic elements are driven to diffuse into the coating interior, in-situ self-generating a surface high-entropy ceramic film. During this process, no heterogeneous metal components are introduced, and a continuous gradient evolution relationship of non-metallic components is formed between layers, laying the scientific foundation for "homogeneity." Based on this, by controlling the proportion of non-metallic components between layers through chemical potential gradient, the content of ceramic phase and key properties such as coating phase state and elastic modulus are continuously and gradually changed, forming a sandwich layer structure with strong and tough load-bearing bottom layer, tough and brittle transition middle layer and ultra-hard and wear-resistant surface layer, achieving "heterogeneous" functional performance. This fundamentally alleviates the problem of abrupt changes in interface composition and performance of traditional coatings, and successfully constructs an integrated coating system with homologous composition, heterogeneous structure and gradually changing performance gradient, realizing the paradigm shift of functionally graded materials from "heterogeneous composite" to "homogeneous in-situ derivation".

[0047] The specific approach is as follows: (1) High-entropy alloy layer: Drawing on the strong and tough support, tight bonding and uniform load transmission mechanism of bamboo yellow, a TiZrNbTaMo system high-entropy alloy toughening underlayer is designed, and laser directional energy deposition (L-DED) is used to achieve metallurgical bonding with the substrate. As a strong and tough skeleton of the inner layer of the coating, this layer can provide a stable bearing and stress transmission foundation for the intermediate layer of high-entropy alloy composite material and the surface layer of high-entropy ceramic film, uniformly disperse the external load to the substrate, and eliminate residual stress and alternating stress by relying on high toughness, suppress the propagation of penetrating cracks to the substrate, and ensure the overall integrity of the coating. It is the key layer that supports the long-term service of the coating.

[0048] (2) High-entropy alloy composite layer: Based on the mechanism of bamboo flesh gradient transition and tough bridging, an interpenetrating network gradient transition intermediate layer composed of ceramic phase and high-entropy alloy is designed. The high-entropy alloy composite intermediate layer with controllable ceramic phase content gradient is prepared layer by layer using laser-directed energy deposition (L-DED) technology. By mixing different proportions of ceramic phase non-metallic components into the high-entropy alloy powder for layer-by-layer preparation, a continuous gradient distribution of ceramic phase is achieved, so that key parameters such as elastic modulus and thermal expansion coefficient change continuously from the surface high-hardness ceramic film to the bottom tough alloy layer, eliminating abrupt changes in interface properties. The interpenetrating network structure of this layer has both the tough composite and gradient transition characteristics of bamboo flesh, and can act as a "biomimetic ligament" to achieve effective bridging between the surface ultra-hard ceramic film and the bottom alloy layer. While bearing and transmitting external stress, it provides structural support for the surface ceramic film and inhibits its brittle spalling failure.

[0049] (3) High-entropy ceramic film: Drawing on the dense structure and protection mechanism of bamboo, a high-entropy ceramic film with high density is prepared on the material surface through in-situ reaction using a high-temperature thermal diffusion process. This is used to construct a wear-resistant surface protection layer. At the same time, the interface of the high-entropy alloy composite material layer is subjected to atomic-level redistribution tempering treatment. The microstructure is optimized through atomic rearrangement in the interface region, thereby further mitigating the sudden change in performance gradient at the interface.

[0050] This invention is based on the biomimetic design concept of gradient protection for bamboo, and constructs a "homogeneous heterogeneous" high-entropy sandwich structure coating. The specific technical path is as follows:

[0051] (1) Preparation of high-entropy alloy layer: Laser directed energy deposition (L-DED) technology is used to induce non-equilibrium rapid solidification of the molten pool by a high-energy laser beam to prepare a high-entropy alloy layer on the substrate surface, forming a strong and tough skeleton structure;

[0052] (2) Preparation of high-entropy alloy composite material layer: High-entropy alloy mixed powder containing different proportions of ceramic phase non-metallic components was prepared; Laser directed energy deposition (L-DED) technology was used to prepare high-entropy alloy composite material layer with controllable ceramic phase content gradient on the surface of the high-entropy alloy layer prepared in step (1) in order of increasing ceramic phase non-metallic component content, using high-entropy alloy mixed powder containing different proportions of ceramic phase non-metallic components, as the key connection layer between the surface high-entropy ceramic film and the toughened high-entropy alloy bottom layer;

[0053] (3) In-situ self-generation preparation of high-density high-entropy ceramic film: Using the thermal diffusion driving mechanism of the embedding infiltration process, a high-entropy ceramic film is constructed on the surface of the high-entropy alloy composite material layer. The non-metallic elements of the ceramic phase are driven to diffuse into the interior of the high-entropy alloy composite material layer through the chemical potential gradient, releasing the interfacial stress concentration and causing in-situ reaction, generating a high-density, high-thermal-stability high-entropy ceramic film, realizing the core protective functions of surface anti-oxidation and wear resistance.

[0054] The substrate mentioned in step (1) of this invention includes, but is not limited to, medical alloys, high-temperature alloys, and steel materials. For example, titanium alloys, CoCrNi alloys, iron-based alloys, etc. The substrate is first cut, polished (for example, the substrate sample is cut into 50mm×50mm×6mm size using wire electrical discharge machining technology, and then polished with 240~1500# SiC sandpaper to ensure that the surface is flat and without obvious scratches), cleaned, and dried, and then a high-entropy alloy layer is prepared on its surface.

[0055] In one preferred embodiment, the mass percentage of each component in the high-entropy alloy layer in step (1) is: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, Mo 5.16~7.43%.

[0056] In one preferred embodiment, during the laser-directed energy deposition process in step (1), a coaxial powder feeding method is used, with a powder feeding speed of 20 g / min; the laser power is 1900~2500 W, and the scanning speed is 6~10 mm / s. The use of a coaxial powder feeding method, appropriate laser power, and scanning speed ensures good adhesion between the coating and the substrate, eliminates obvious defects, and forms a dense and uniform coating with a thickness controlled between 0.2 and 1 mm.

[0057] In one preferred embodiment, the high-entropy alloy mixed powder in step (2) comprises high-entropy alloy powder and ceramic phase non-metallic components, wherein the ceramic phase non-metallic components are one or more of B, C, Si, and N; more preferably, Si. In a more preferred embodiment, the mass ratio of the high-entropy alloy powder to the ceramic phase non-metallic components is 99.5~99.9wt%:0.1~0.5wt%.

[0058] In one preferred embodiment, the mass percentage of each component in the high-entropy alloy mixed powder in step (2) is: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, Mo 5.16~7.43%.

[0059] In the technical solution described in this invention, in steps (1) and (2), the high-entropy alloy powder raw materials (Ti powder, Zr powder, Nb powder, Ta powder and Mo powder) used are all spherical powders with a particle size of 10~200μm, and more preferably, the particle size range is 45~105μm; the powder mixing method used is preferably 3D powder mixing (using a three-dimensional metal powder mixer to mix the powder).

[0060] In one preferred embodiment, during the laser-directed energy deposition process in step (2), a coaxial powder feeding method is used, with a powder feeding speed of 20 g / min; the laser power is 1900~2500 W, and the scanning speed is 6~10 mm / s. The use of a coaxial powder feeding method, appropriate laser power, and scanning speed ensures good adhesion between the coating and the substrate, eliminates obvious defects, and forms a dense and uniform coating with a thickness controlled between 0.2 and 1 mm.

[0061] In one preferred embodiment, the number of layers of the high-entropy alloy composite material layer in step (2) is ≥3, and the thickness of each layer is controlled between 0.2 and 1 mm.

[0062] In one preferred embodiment, in step (2), the sample prepared in step (1) can be first polished (e.g., polished with 240~1500# SiC sandpaper), cleaned, and dried before a high-entropy alloy composite material layer is prepared on its surface. The cleaning is preferably ultrasonic cleaning, and the drying is preferably done at 100°C for 2 hours.

[0063] In one preferred embodiment, the mass percentage of each component of the infiltrator used in the embedding and infiltration process in step (3) is: Si 20~45%, NaF 5~10%, Y2O3 1~3%, with the balance being ZrO2; wherein the particle size of each component powder of the infiltrator is 100~200μm.

[0064] In a more preferred embodiment, the mass percentages of the components of the penetrant are: Si 25%, NaF 6%, Y2O3 2%, with the balance being ZrO2.

[0065] In a more preferred embodiment, the penetrant is prepared by ball milling, with process parameters including: a ball-to-material mass ratio of 2-4:1, a ball milling time of 2-8 hours, and a ball milling speed of 300-400 r / min. These process parameter ranges ensure a uniform distribution of the penetrant's components. The most preferred process parameters include: a ball-to-material mass ratio of 3:1, a ball milling time of 4 hours, and a ball milling speed of 400 r / min.

[0066] In one preferred embodiment, the embedding process in step (3) includes raising the temperature to 1000~1200℃ and holding it at that temperature for 0.5~2h. Under these temperature and time conditions, Si elements can be directed to diffuse into the interior of the high-entropy alloy composite material layer and undergo in-situ reactions to generate a high-density, high-thermal-stability high-entropy ceramic film.

[0067] In one preferred embodiment, the embedding and infiltration process in step (3) is carried out in an environment with an inert gas, such as argon, as a protective atmosphere, with a heating rate of 5°C / min and a cooling method of furnace cooling.

[0068] In one preferred embodiment, in step (3), the sample prepared in step (2) can be first polished (e.g., polished and chamfered using 240~1500# SiC sandpaper to ensure a smooth surface without sharp protrusions), cleaned, and dried, and then a high-entropy ceramic membrane can be constructed by an embedding process. The cleaning is preferably ultrasonic cleaning, and the drying is preferably done at 60°C for 2 hours.

[0069] Example 1:

[0070] Step 1: In this embodiment, TC4 is selected as the substrate and polished to a smooth surface using 240~1500# SiC sandpaper. Laser-directed energy deposition (L-DED) technology is then used to prepare a high-entropy alloy layer on the substrate surface without obvious pores, cracks, or metallurgical bonding.

[0071] During the preparation of the high-entropy alloy layer, high-entropy alloy powder was weighed according to the following mass percentages: Ti 39wt%, Zr 39wt%, Nb 10wt%, Ta 5wt%, and Mo 7wt%. The particle size of each component of the high-entropy alloy powder was 45~105μm. After being thoroughly mixed using a 3D powder mixing process, it was dried at 60℃ for 2 hours for later use.

[0072] The selected process parameters for the laser-directed energy deposition technology are as follows: laser power of 1900 W, scanning speed of 6 mm / s, spot diameter of 2 mm, coaxial powder feeding method, and powder feeding speed of 20 g / min; coating thickness is controlled between 0.2 and 1 mm.

[0073] Step 2: Prepare a high-entropy alloy composite material layer using laser-directed energy deposition technology:

[0074] The sample obtained in step one was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0075] 99.9 g of high-entropy alloy powder and 0.1 g of high-purity silicon powder were weighed according to a silicon content of 0.1 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0076] 99.8 g of high-entropy alloy powder and 0.2 g of high-purity silicon powder were weighed according to a silicon content of 0.2 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing with 3D powder mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0077] 99.7 g of high-entropy alloy powder and 0.3 g of high-purity silicon powder were weighed according to a silicon content of 0.3 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0078] Using the same L-DED process as in step one, three layers of high-entropy alloy composite material were prepared layer by layer in order of increasing silicon content in the high-entropy alloy mixed powder, ensuring that there were no significant pores or cracks between the layers and achieving metallurgical bonding.

[0079] Step 3, Preparation of high-entropy ceramic membrane:

[0080] The sample obtained in step two was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0081] Preparation of the penetrant: The mass percentage of each component in the penetrant is: Si 25%, NaF 6%, Y2O3 2%, with the balance being ZrO2. The particle size of each component powder is 100~200μm. A uniformly dispersed penetrant was prepared by ball milling at a ball-to-powder mass ratio of 3:1, a ball milling time of 4 hours, and a ball milling speed of 400 r / min. The penetrant was then dried at 60℃ for 2 hours for later use.

[0082] The penetrant powder is loaded into the crucible and compacted until it reaches half the depth of the crucible. Then, the sample obtained in step two after grinding is buried in the penetrant powder. The penetrant powder is added and compacted until it is flush with the crucible opening. Finally, the crucible lid is put on and the crucible is sealed.

[0083] The sealed crucible was placed in the center of the tube furnace to ensure accurate and uniform temperature. A vacuum pump was used to evacuate the furnace and high-purity argon gas was introduced to prevent oxidation during heating and thus avoid cracking. The furnace was heated in an argon atmosphere at a rate of 5°C / min to 1100°C and held for 0.5 hours, then cooled to room temperature in the furnace.

[0084] A high-entropy ceramic film was obtained that forms a diffusion metallurgical bond with the high-entropy alloy composite layer interface without obvious peeling.

[0085] The surface high-entropy ceramic film of the homologous high-entropy sandwich gradient coating prepared in this embodiment has a thickness of 8.6 μm. Scratch tests show that the bonding force between the high-entropy ceramic film and the high-entropy alloy composite material layer is 105 N, indicating good adhesion.

[0086] Example 2:

[0087] Step 1: In this embodiment, TC4 is selected as the substrate and polished to a smooth surface using 240~1500# SiC sandpaper. Laser-directed energy deposition (L-DED) technology is then used to prepare a high-entropy alloy layer on the substrate surface without obvious pores, cracks, or metallurgical bonding.

[0088] During the preparation of the high-entropy alloy layer, high-entropy alloy powder was weighed according to the following mass percentages: Ti 39wt%, Zr 39wt%, Nb 10wt%, Ta 5wt%, and Mo 7wt%. The particle size of the high-entropy alloy powder was 45~105μm. After being thoroughly mixed using a 3D powder mixing process, it was dried at 60℃ for 2 hours for later use.

[0089] The selected process parameters for the laser-directed energy deposition technology are as follows: laser power of 2100 W, scanning speed of 8 mm / s, spot diameter of 2 mm, coaxial powder feeding method, and powder feeding speed of 20 g / min; coating thickness is controlled between 0.2 and 1 mm.

[0090] Step 2: Prepare a high-entropy alloy composite material layer using laser-directed energy deposition technology:

[0091] The sample obtained in step one was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0092] 99.9 g of high-entropy alloy powder and 0.1 g of high-purity silicon powder were weighed according to a silicon content of 0.1 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0093] 99.8 g of high-entropy alloy powder and 0.2 g of high-purity silicon powder were weighed according to a silicon content of 0.2 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing with 3D powder mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0094] 99.7 g of high-entropy alloy powder and 0.3 g of high-purity silicon powder were weighed according to a silicon content of 0.3 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0095] Using the same L-DED process as in step one, three layers of high-entropy alloy composite material were prepared layer by layer in order of increasing silicon content in the high-entropy alloy mixed powder, ensuring that there were no significant pores or cracks between the layers and achieving metallurgical bonding.

[0096] Step 3, Preparation of high-entropy ceramic membrane:

[0097] The sample obtained in step two was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0098] Preparation of the penetrant: The mass percentage of each component in the penetrant is: Si 25%, NaF 6%, Y2O3 2%, with the balance being ZrO2. The particle size of each component powder is 100~200μm. A uniformly dispersed penetrant was prepared by ball milling at a ball-to-powder mass ratio of 3:1, a ball milling time of 4 hours, and a ball milling speed of 400 r / min. The penetrant was then dried at 60℃ for 2 hours for later use.

[0099] The penetrant powder is loaded into the crucible and compacted until it reaches half the depth of the crucible. Then, the sample obtained in step two after grinding is buried in the penetrant powder. The penetrant powder is added and compacted until it is flush with the crucible opening. Finally, the crucible lid is put on and the crucible is sealed.

[0100] The sealed crucible was placed in the center of the tube furnace to ensure accurate and uniform temperature. A vacuum pump was used to evacuate the furnace and high-purity argon gas was introduced to prevent oxidation during heating and thus avoid cracking. The furnace was heated in an argon atmosphere at a rate of 5°C / min to 1000°C and held for 1 hour, then cooled to room temperature in the furnace.

[0101] A high-entropy ceramic film was obtained that forms a diffusion metallurgical bond with the high-entropy alloy composite layer interface without obvious peeling.

[0102] The surface high-entropy ceramic film of the homologous high-entropy sandwich gradient coating prepared in this embodiment has a thickness of 12.5 μm. Scratch tests show that the bonding force between the high-entropy ceramic film and the high-entropy alloy composite layer is 113 N, indicating good adhesion.

[0103] Example 3:

[0104] Step 1: In this embodiment, TC4 is selected as the substrate and polished to a smooth surface using 240~1500# SiC sandpaper. Laser-directed energy deposition (L-DED) technology is then used to prepare a high-entropy alloy layer on the substrate surface without obvious pores, cracks, or metallurgical bonding.

[0105] During the preparation of the high-entropy alloy layer, high-entropy alloy powder was weighed according to the following mass percentages: Ti 39wt%, Zr 39wt%, Nb 10wt%, Ta 5wt%, and Mo 7wt%. The particle size of the high-entropy alloy powder was 45~105μm. After being thoroughly mixed using a 3D powder mixing process, it was dried at 60℃ for 2 hours for later use.

[0106] The selected process parameters for the laser-directed energy deposition technology are as follows: laser power of 2300W, scanning speed of 10 mm / s, spot diameter of 2 mm, coaxial powder feeding method, and powder feeding speed of 20 g / min; coating thickness is controlled between 0.2 and 1 mm.

[0107] Step 2: Prepare a high-entropy alloy composite material layer using laser-directed energy deposition technology:

[0108] The sample obtained in step one was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0109] 99.9 g of high-entropy alloy powder and 0.1 g of high-purity silicon powder were weighed according to a silicon content of 0.1 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0110] 99.8 g of high-entropy alloy powder and 0.2 g of high-purity silicon powder were weighed according to a silicon content of 0.2 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing with 3D powder mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0111] 99.7 g of high-entropy alloy powder and 0.3 g of high-purity silicon powder were weighed according to a silicon content of 0.3 wt% of the total mass of the high-entropy alloy powder mixture. After thorough mixing using 3D mixing, the mixture was dried at 60℃ for 2 hours for later use. The mass percentage of the high-entropy alloy powder was as follows: Ti 39 wt%, Zr 39 wt%, Nb 10 wt%, Ta 5 wt%, Mo 7 wt%.

[0112] Using the same L-DED process as in step one, three layers of high-entropy alloy composite material were prepared layer by layer in order of increasing silicon content in the high-entropy alloy mixed powder, ensuring that there were no significant pores or cracks between the layers and achieving metallurgical bonding.

[0113] Step 3, Preparation of high-entropy ceramic membrane:

[0114] The sample obtained in step two was polished with 240~1500# SiC sandpaper until the surface was flat, then ultrasonically cleaned, and then dried at 100℃ for 2 hours for later use.

[0115] Preparation of the penetrant: The mass percentage of each component in the penetrant is: Si 25%, NaF 6%, Y2O3 2%, with the balance being ZrO2. The particle size of each component powder is 100~200μm. A uniformly dispersed penetrant was prepared by ball milling at a ball-to-powder mass ratio of 3:1, a ball milling time of 4 hours, and a ball milling speed of 400 r / min. The penetrant was then dried at 60℃ for 2 hours for later use.

[0116] The penetrant powder is loaded into the crucible and compacted until it reaches half the depth of the crucible. Then, the sample obtained in step two after grinding is buried in the penetrant powder. The penetrant powder is added and compacted until it is flush with the crucible opening. Finally, the crucible lid is put on and the crucible is sealed.

[0117] The sealed crucible was placed in the center of the tube furnace to ensure accurate and uniform temperature. A vacuum pump was used to evacuate the furnace and high-purity argon gas was introduced to prevent oxidation during heating and thus avoid cracking. The furnace was heated in an argon atmosphere at a rate of 5°C / min to 1200°C and held for 2 hours, then cooled to room temperature in the furnace.

[0118] A high-entropy ceramic film was obtained that forms a diffusion metallurgical bond with the high-entropy alloy composite layer interface without obvious peeling.

[0119] The surface high-entropy ceramic film of the homologous high-entropy sandwich gradient coating prepared in this embodiment has a thickness of 22.4 μm. Scratch tests show that the bonding force between the high-entropy ceramic film and the high-entropy alloy composite material layer is 126 N, indicating good adhesion.

[0120] Comparative Example 1:

[0121] The difference between this comparative example and Example 1 lies in the different L-DED and embedding / infiltration process parameters. In this comparative example: the laser power is 1500 W, the scanning speed is 15 mm / s, the embedding / infiltration temperature is 850℃, and the holding time is 1 h.

[0122] This comparative example yielded a high-entropy ceramic film with obvious porosity and a non-dense structure, with a coating thickness of approximately 6.5 μm. Scratch testing showed that the adhesion between the high-entropy ceramic film and the high-entropy alloy composite layer was 72 N, indicating poor adhesion.

[0123] Comparative Example 2:

[0124] The difference between this comparative example and Example 2 is that the content of each component of the penetrant is different. In this comparative example, the mass percentage of each component of the penetrant is: Si: 10%, NaF: 6%, and the balance is ZrO2.

[0125] In this comparative example, due to insufficient silicon source content in the diffusion agent and the lack of Y₂O₃ catalytic activation, the driving force and rate of silicon atom diffusion into the high-entropy alloy coating were significantly reduced. This resulted in a final high-entropy ceramic film of approximately 10 μm, which was discontinuous and not dense. Scratch tests showed that the bonding force between the high-entropy ceramic film and the high-entropy alloy composite layer was only 65 N, indicating poor adhesion.

[0126] Comparative Example 3:

[0127] The only difference between this comparative example and Example 3 is that step two was not performed to prepare the intermediate high-entropy alloy composite material layer.

[0128] The comparative example lacks an intermediate layer that can achieve a gradient transition of ductile and brittle properties, resulting in through-cracks in the prepared high-entropy ceramic film, which destroys the dense structure of the film and thus causes the coating to lose its functionality.

[0129] As can be seen from the above embodiments and comparative examples, in response to the scientific problem of easy cracking at heterogeneous interfaces, inspired by the "dense on the outside and sparse on the inside" gradient structure characteristics of natural bamboo materials, and based on a high-entropy system with adjustable composition and performance, this invention constructs a coating with a sandwich-like gradient structure of "high-entropy alloy layer - high-entropy composite material layer - high-entropy ceramic film" using in-situ self-generation technology. This realizes the transition and enhancement of functional gradient materials from "heterogeneous composite" to "homogeneous in-situ derivation", achieving the functional gradient transition and enhancement effect of bottom toughness (metallurgical bonding, strengthening and buffering), middle layer biomimetic ligament (bridging toughness), and surface super hardness (wear resistance and corrosion resistance), effectively improving the comprehensive performance of the coating.

[0130] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a homologue heterogeneous high-entropy sandwich gradient coating, characterized in that, Includes the following steps: (1) Preparation of high-entropy alloy layer: A high-entropy alloy layer was prepared on the substrate surface using laser-directed energy deposition technology; (2) Preparation of high-entropy alloy composite material layer: Using laser directional energy deposition technology, on the surface of the high-entropy alloy layer prepared in step (1), according to the order of ceramic phase non-metallic component content from low to high, a high-entropy alloy mixed powder containing different proportions of ceramic phase non-metallic components is used to prepare a high-entropy alloy composite material layer with controllable ceramic phase content gradient layer by layer. (3) In-situ self-generation preparation of high-density high-entropy ceramic film: High-entropy ceramic film is constructed on the surface of high-entropy alloy composite material layer by embedding infiltration process, and finally the homogeneous high-entropy sandwich gradient coating is obtained.

2. The preparation method according to claim 1, characterized in that, The mass percentages of each component in the high-entropy alloy layer in step (1) are: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, and Mo 5.16~7.43%.

3. The preparation method according to claim 1, characterized in that, In step (1), during the laser-directed energy deposition process, the powder feeding rate is 20 g / min; the laser power is 1900~2500 W; and the scanning speed is 6~10 mm / s.

4. The preparation method according to claim 1, characterized in that, The high-entropy alloy mixed powder mentioned in step (2) comprises high-entropy alloy powder and ceramic phase non-metallic components, wherein the ceramic phase non-metallic components are one or more of B, C, Si, and N; the mass ratio of the high-entropy alloy powder to the ceramic phase non-metallic components is 99.5~99.9wt%: 0.1~0.5wt%; and the high-entropy alloy powder, by mass percentage, is: Ti 38.46~41.49%, Zr 38.46~41.49%, Nb 12.28~13.50%, Ta 5.64~6.67%, and Mo 5.16~7.43%.

5. The preparation method according to claim 1, characterized in that, The thickness of the high-entropy alloy layer in step (1) is controlled at 0.2~1mm; the number of layers of the high-entropy alloy composite material layer in step (2) is ≥3, and the thickness of each layer is controlled at 0.2~1mm.

6. The preparation method according to claim 1, characterized in that, In the laser directional energy deposition process described in step (2): a coaxial powder feeding method is selected, the powder feeding speed is 20g / min; the laser power is 1900~2500W, and the scanning speed is 6~10mm / s.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass percentage of each component of the infiltrator used in the embedding and infiltration process is: Si 20~45%, NaF 5~10%, Y2O3 1~3%, and the balance is ZrO2.

8. The preparation method according to claim 1, characterized in that, The embedding and infiltration process described in step (3) includes raising the temperature to 1000~1200℃ and keeping it at that temperature for 0.5~2h.

9. The homophyletic high-entropy sandwich gradient coating prepared by the method of any one of claims 1-8.

10. The application of the homogeneous heterogeneous high-entropy sandwich gradient coating described in claim 9 in the fields of aerospace, biomedicine or high-end machinery manufacturing.

Images