A laser-clad high-entropy alloy carbide ceramic coating and its preparation method

Abstract

This invention discloses a laser-clad high-entropy alloy carbide ceramic coating and its preparation method, belonging to the field of high-entropy alloy coating technology. Utilizing laser cladding technology, a strong metallurgical bond is achieved between the coating and the substrate by in-situ melting of the substrate and high-entropy alloy-phenolic resin composite powder with a high-energy laser beam. The elements at the interface exhibit a gradient transition, resulting in a shear strength exceeding 100 MPa. A single-layer deposition thickness can reach over 500 μm, and multiple layers can be accumulated to the centimeter level, significantly improving coating thickness capability. The prepared coating exhibits high density and a porosity of less than 5%, effectively solving the key technical contradiction of the inability to synergistically optimize thickness and density in traditional thermal spraying. Furthermore, this invention innovatively employs an in-situ carbonization reaction under a methane atmosphere, solving the complex high-temperature synthesis process of traditional high-entropy carbide powders, significantly reducing preparation costs and cycle time, and possessing the significant advantages of high efficiency, low cost, and high performance.

Description

Technical Field

[0001] This invention relates to the field of high-entropy alloy coating technology, and in particular to a laser cladding high-entropy alloy carbide ceramic coating and its preparation method. Background Technology

[0002] High-entropy alloys are alloys with five or more main elements and a mixing entropy higher than 1.5R. Due to their unique structure and multi-element composition, high-entropy alloys exhibit higher strength, wear resistance, and ductility than traditional alloys. High-entropy alloys are a new type of metallic material with excellent physical, magnetic, chemical, and mechanical properties that has been developed in recent years. Therefore, they have enormous application potential in aerospace, electronics, chemical engineering, and nuclear reactors.

[0003] In recent years, with the rapid development of aerospace technology, higher requirements have been placed on the performance of materials. Refractory high-entropy alloys with single-phase BCC structure have attracted increasing attention. They have excellent mechanical properties and characteristics such as high temperature resistance and corrosion resistance. They can be specifically applied to engine parts, structural materials, high-temperature alloys, and functional components. These characteristics make refractory high-entropy alloys with single-phase BCC structure an important direction in aerospace materials research, providing new ideas for the material design of next-generation aircraft and spacecraft.

[0004] Currently, thermal spraying, as the most commonly used technique for preparing high-entropy ceramic coatings, suffers from significant defects in bonding performance and structure. This method relies on the mechanical interlocking between molten particles and the substrate, with the interfacial bonding mechanism primarily based on physical adhesion rather than metallurgical bonding. This leads to the formation of pores and oxide inclusions at the interface, significantly weakening the adhesion between the coating and the substrate. The coating is prone to peeling during actual service, resulting in severely insufficient reliability. Furthermore, limited by weak interlayer adhesion and the cumulative effect of thermal stress, traditional thermal spraying cannot deposit thick coatings in a single pass, with single-layer thickness typically limited to below 200 micrometers. Increasing the total thickness requires multiple sprayings, but this introduces higher porosity and raises the risk of interlayer delamination. This creates an irreconcilable contradiction between coating density and thickness, making it impossible to meet the high-density requirements of thick coatings in high-end applications.

[0005] On the other hand, the preparation process of traditional high-entropy carbide ceramic coatings is complex and costly. It requires the prior synthesis of high-entropy carbide powder, a process typically carried out at ultra-high temperatures exceeding 1600°C in a vacuum or protective atmosphere. This places extremely demanding requirements on equipment, resulting in complex processes, long cycles, and high energy consumption, leading to extremely high powder costs. Furthermore, thermal spraying technology itself suffers from low preparation efficiency. Due to the limited thickness of a single deposition, repeated spraying and processing are necessary, resulting in long production cycles and further increasing overall costs, severely hindering the widespread adoption of high-entropy ceramic coatings in large-scale industrial applications.

[0006] Therefore, a new method is needed to prepare high-entropy alloy carbide ceramic coatings. Summary of the Invention

[0007] The purpose of this invention is to provide a laser-clad high-entropy alloy carbide ceramic coating and its preparation method. Utilizing laser cladding technology, a high-energy laser beam is used to in-situ melt the substrate and high-entropy alloy-phenolic resin composite powder, achieving a strong metallurgical bond between the coating and the substrate. The elements at the interface exhibit a gradient transition, resulting in a shear strength exceeding 100 MPa. A single-layer deposition thickness can reach over 500 μm, and multiple layers can be accumulated to the centimeter level, significantly improving coating thickness capability. The prepared coating exhibits high density and a porosity of less than 5%, effectively solving the key technical contradiction of the inability to synergistically optimize thickness and density in traditional thermal spraying. Furthermore, this invention innovatively employs an in-situ carbonization reaction under a methane atmosphere, solving the complex high-temperature synthesis process of traditional high-entropy carbide powders, significantly reducing preparation costs and time, and possessing the significant advantages of high efficiency, low cost, and high performance.

[0008] To achieve the above objectives, this invention discloses a method for preparing a laser-clad high-entropy alloy carbide ceramic coating. First, a mixed powder of high-entropy alloy and phenolic resin is provided. The mixed powder is then melted and solidified on the surface of a substrate using laser cladding technology to form a coating that is metallurgically bonded to the substrate. Finally, a dense high-entropy alloy carbide ceramic coating is obtained by carbonizing the coating through the synergistic effect of dual carbon sources. The porosity and structural gradient of the coating are controlled by adjusting the ratio of phenolic resin to high-entropy alloy powder.

[0009] The dual carbon sources for carbonization come from the phenolic resin decomposed during laser cladding and the methane atmosphere.

[0010] Preferably, it includes the following steps:

[0011] S1. Surface pretreatment of the substrate: The surface oxide layer of the niobium alloy substrate is removed by grinding with 1000# SiC sandpaper until the surface is exposed with metallic luster. The niobium alloy substrate after grinding is cleaned with anhydrous ethanol as a cleaning agent. After ultrasonic cleaning for 10 minutes, the cleaning agent on the substrate surface is removed by drying to obtain the pretreated niobium alloy substrate.

[0012] S2. Preparation of refractory high-entropy alloy and phenolic resin mixed powder: Weigh the high-entropy alloy powder and phenolic resin powder and pour them into a V-type vacuum mixer. Seal the mixer and evacuate it to 0.08MPa~0.1MPa. Set the speed to 60~80 rpm and the mixing time to 360~480 minutes. Start the mixing process. After the mixing process is completed, release the gas and open the equipment to obtain the mixed powder of refractory high-entropy alloy and phenolic resin.

[0013] S3, Laser cladding: The mixed powder prepared in step 2 above is loaded into the powder feeder, the laser cladding parameters are set, and the dried refractory high entropy alloy powder is deposited on the pretreated substrate surface under Ar2 atmosphere to form a high entropy alloy coating with a certain porosity on the pretreated substrate surface.

[0014] S4, Methane Carbonization: The high-entropy alloy coating prepared in step 3 above is ultrasonically cleaned in ethanol or acetone for 10-15 minutes and dried with nitrogen. Then, the cleaned sample is placed in the constant temperature zone of a tube furnace, the furnace is closed and sealed, the temperature is adjusted by gradient, and the protective gas and methane are switched according to the temperature. Then, the temperature is cooled to room temperature to obtain a dense high-entropy alloy carbide ceramic coating.

[0015] Preferably, in step S2, the high-entropy alloy powder is a mixture of any five or more spherical metal powders selected from Ti, Zr, Hf, Ta, Nb, and Mo, with a particle size of 5 to 50 μm; the phenolic resin powder has a particle size of less than 30 μm, and the mass ratio of the high-entropy alloy powder to the phenolic resin powder is (7:3) to (9:1).

[0016] Preferably, in step S3, synchronous powder feeding is adopted, and the laser cladding parameters are: laser power of 1200~1500W, scanning speed of 8mm / s~20mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min.

[0017] Preferably, in step S3, the thickness of the high-entropy alloy coating is 0.5~0.68mm, and the porosity is 12~30%.

[0018] Preferably, in step S4, the temperature gradient adjustment and the switching between the protective gas and methane include the following stages:

[0019] (1) The room temperature is raised to 1400~1700℃ at a rate of 10℃ / min, during which nitrogen or argon gas with a flow rate of 20~30sccm is introduced as a protective gas;

[0020] (2) After reaching 1400~1700℃, switch to CH4 gas with a flow rate of 50sccm, keep warm for 2 hours, and use a mass spectrometer to monitor the CO and CO2 content in the tail gas in real time, and adjust the gas ratio to make the carbon activity about 1.2.

[0021] (3) After the heat preservation is completed, turn off CH4 and H2 and replace them with nitrogen or argon.

[0022] Preferably, in step S4, the cooling rate is less than 5°C / min, and after cooling to 300°C, the product is taken out and air-cooled to room temperature.

[0023] The present invention also provides a high-entropy alloy carbide ceramic coating prepared by the above preparation method, the coating having a single FCC solid solution structure.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] Compared to traditional methods, this invention improves the purity of high-entropy ceramic powder by carbonizing high-entropy alloy powder in a methane atmosphere, thereby removing impurities such as oxygen from the alloy and preventing the introduction of impurities from the raw materials. Because the raw material is a high-entropy alloy, the elements within it possess atomic-level homogeneity. In-situ carbonization of this alloy yields a microscopically uniform mixture of metal carbides. Further high-temperature solution treatment produces high-entropy ceramic powder with a uniform microstructure and composition. This method overcomes the problems of uneven mixing and uneven carbothermic reduction reactions in high-temperature carbothermic reduction methods, which result in more impurity phases in the prepared powder and make it more difficult to obtain pure target high-entropy ceramic powder. In high-temperature sintering methods, the simple carbides in the raw materials contain many impurities, which are introduced into the target powder. Furthermore, it is difficult to mix the simple carbide particles evenly, resulting in a large atomic migration distance during solid solution sintering. At the same time, ultra-high temperature carbide ceramics have good high-temperature stability and a slow atomic diffusion rate, making sintering difficult. Ultimately, it is difficult to obtain pure target high-entropy ceramic powder, and problems such as simple carbide powder and partially carbide solid solution powder are inevitable.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 SEM image of the mixed powder prepared in Example 1;

[0028] Figure 2 SEM images of the high-entropy alloy coating prepared in Example 1 are shown, where a is a cross-sectional morphology of the high-entropy alloy coating and the substrate metallurgically bonded at low magnification, and b is a magnified view of the local morphology of the high-entropy alloy coating with a certain porosity.

[0029] Figure 3 The image shows the EDS spectrum of the high-entropy alloy coating prepared in Example 1.

[0030] Figure 4 The images are XRD images of the materials obtained in different steps of Example 1, where a is the XRD image of the high-entropy alloy coating prepared in step S3, and b is the XRD image of the dense high-entropy alloy carbide ceramic (TiZrNbHfTa)C coating prepared in step S4.

[0031] Figure 5The image shows a SEM image of the dense high-entropy alloy carbide ceramic (TiZrNbHfTa) C coating obtained in Example 1. In the image, a is a cross-sectional morphology of the metallurgical bonding between the high-entropy carbide ceramic coating and the substrate at low magnification, and b is a magnified view of the local morphology of the dense high-entropy carbide ceramic coating.

[0032] Figure 6 The image shows the EDS spectrum of the dense high-entropy alloy carbide ceramic (TiZrNbHfTa) C coating obtained in Example 1.

[0033] Figure 7 The image shows the coating adhesion and shear strength curves of the dense high-entropy alloy carbide ceramic (TiZrNbHfTa) C coating obtained in Example 1.

[0034] Figure 8 SEM images of thermally sprayed high-entropy carbide ceramic coatings prepared at different magnifications are shown in the comparative examples, where a is 200x, b is 500x, c is 1000x, and d is 3000x. Detailed Implementation

[0035] The technical solution of the present invention will be further described below through examples and embodiments.

[0036] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0037] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0038] Example 1:

[0039] This embodiment provides a method for preparing a high-entropy carbide (TiZrNbHfTa)C dense coating by laser cladding, and the preparation method is as follows:

[0040] S1. Substrate surface pretreatment:

[0041] The surface of the C-103 niobium alloy substrate was polished with 1000# SiC sandpaper until a metallic luster was exposed, indicating that the surface oxide film had been removed. The polished substrate was then cleaned with anhydrous ethanol as a cleaning agent, followed by ultrasonic cleaning for 10 minutes. After drying, the cleaning agent was removed from the substrate surface, yielding the pretreated substrate.

[0042] S2. Preparation of a mixed powder of refractory high-entropy alloy and phenolic resin:

[0043] Commercially available spherical high-entropy alloy powder TiZrNbHfTa with a purity ≥99.9% and a particle size of 50~150μm, mixed in an equimolar ratio, and spherical phenolic resin powder with a purity ≥99.9% and a particle size of 50~150μm, were accurately weighed at a ratio of 7:3 using an electronic balance. The mixture was then poured into a V-type vacuum mixer, sealed, and evacuated to 0.08MPa. The mixing speed was set to 60 rpm and the mixing time to 360 minutes. Mixing was started, and the mixing process was observed and adjusted as needed. After completion, the gas was released, and the equipment was opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin. The SEM image of this mixed powder is shown below. Figure 1 As shown, the spherical shape is TiZrNbHfTa powder, and the irregular shape is phenolic resin powder.

[0044] S3, Laser Cladding:

[0045] The mixed powder prepared in step S2 was loaded into a powder feeder. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 1200W, scanning speed of 8mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min. Under an Ar2 atmosphere, the dried refractory high-entropy alloy powder was deposited on the pretreated substrate surface, forming a high-entropy alloy coating with a certain porosity on the pretreated substrate surface. The SEM image is shown below. Figure 2 As shown, a) is a cross-sectional morphology diagram of the metallurgical bonding between the high-entropy alloy coating and the substrate. As can be seen, the bonding between the substrate and the coating is tight, without defects such as gaps or cracks. b) is a magnified view of a local morphology of the high-entropy alloy coating with a certain porosity of 15.8%. Overall, the distribution of these pores is relatively uniform, without any significant local differences in density or sparseness. Its EDS spectrum is shown below. Figure 3 As shown in the scan results, Ti, Zr, Hf, Ta, and Nb elements exhibit a relatively uniform distribution within the coating area, with no obvious elemental enrichment. Their XRD images are shown below. Figure 4 As shown in figure a, the results indicate that the alloy has a single BCC solid solution phase.

[0046] S4, Methane carbonization:

[0047] The high-entropy alloy coating prepared in step S3 was ultrasonically cleaned in ethanol for 10 minutes and dried with nitrogen. The cleaned sample was then placed in the isothermal zone of a tube furnace, the furnace chamber was closed and sealed, and the gas and exhaust gas lines were connected. The temperature was then increased from room temperature to 1400℃ at a rate of 10℃ / min, with nitrogen or argon gas introduced at a flow rate of 20 sccm as a protective gas. After reaching 1400℃, CH4 gas was switched to a flow rate of 50 sccm, and the temperature was maintained for 2 hours. The CO and CO2 content in the exhaust gas was monitored in real time using a mass spectrometer, and the gas ratio was adjusted to maintain a carbon activity of approximately 1.2. After the holding period, CH4 and H2 were shut off, and nitrogen or argon gas was used instead. The temperature was lowered by furnace cooling at a rate not exceeding 5℃ / min until it reached 300℃, after which the sample was removed and air-cooled to room temperature. The final dense high-entropy alloy carbide ceramic (TiZrNbHfTa) C coating was obtained. Its SEM image is shown below. Figure 5 As shown, a is a cross-sectional morphology of the metallurgical bonding between the high-entropy carbide ceramic coating and the substrate at low magnification, and b is a magnified view of the local morphology of the dense high-entropy carbide ceramic coating. Its EDS spectrum is shown below. Figure 6 As shown, the elemental distribution of the high-entropy carbide ceramic coating is illustrated in its XRD image. Figure 4 As shown in b, the results indicate that the alloy coating transforms from a BCC solid solution phase to a single FCC solid solution phase after carbonization.

[0048] Meanwhile, the coating adhesion and shear strength curves of the dense high-entropy alloy carbide ceramic (TiZrNbHfTa) C coating obtained after carbonization are shown in the figure below. Figure 7 As shown, the coating exhibits high adhesion, indicating that carbonization treatment can effectively enhance the bonding performance between the coating and the substrate.

[0049] Example 2:

[0050] This embodiment provides a method for preparing a high-entropy carbide (TiZrHfTaWo)C dense coating by laser cladding, and the preparation method is as follows:

[0051] S1. Substrate surface pretreatment:

[0052] The surface of the C-103 alloy niobium alloy substrate was polished with 1000# SiC sandpaper until a metallic luster was exposed, indicating that the surface oxide film had been removed. The polished substrate was then cleaned with anhydrous ethanol as a cleaning agent, followed by ultrasonic cleaning for 10 minutes. After drying, the cleaning agent was removed from the substrate surface, yielding the pretreated substrate.

[0053] S2. Preparation of a mixed powder of refractory high-entropy alloy and phenolic resin:

[0054] Commercially available spherical high-entropy alloy powder TiZrHfTaWo with a purity ≥99.9% and a particle size of 50~150μm and spherical phenolic resin powder with a purity ≥99.9% and a particle size of 50~150μm were accurately weighed in an 8:2 ratio using an electronic balance and poured into a V-type vacuum mixer. The mixer was sealed and evacuated to 0.09MPa. The mixing speed was set to 70 rpm and the mixing time to 410 minutes. The mixing process was started, and the mixing was observed and adjusted as needed. After the mixing was completed, the gas was released and the equipment was opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin.

[0055] S3, Laser Cladding:

[0056] The mixed powder prepared in step S2 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1400W, scanning speed of 15mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min. Under Ar2 atmosphere, the dried refractory high-entropy alloy powder is deposited on the pretreated substrate surface to form a high-entropy alloy coating with a certain porosity on the pretreated substrate surface.

[0057] S4, Methane carbonization:

[0058] The high-entropy alloy coating prepared in step S3 was ultrasonically cleaned in acetone for 13 minutes and dried with nitrogen. The cleaned sample was then placed in the isothermal zone of a tube furnace, the furnace chamber was closed and sealed, and the gas and exhaust gas lines were connected. The temperature was then increased from room temperature to 1600℃ at a rate of 10℃ / min, with nitrogen or argon gas flowing through at a flow rate of 25 sccm as a protective gas. Upon reaching 1600℃, CH4 gas was switched to a flow rate of 50 sccm, and the temperature was maintained for 2 hours. The CO and CO2 content in the exhaust gas was monitored in real time using a mass spectrometer, and the gas ratio was adjusted to maintain a carbon activity of approximately 1.2. After the holding period, CH4 and H2 were shut off, and nitrogen or argon gas was used instead. The temperature was lowered by furnace cooling at a rate not exceeding 5℃ / min until it reached 300℃. The sample was then removed and air-cooled to room temperature. The final dense high-entropy alloy carbide ceramic coating was obtained.

[0059] Example 3:

[0060] This embodiment provides a method for preparing a high-entropy carbide (TiZrHfTaNbWo)C dense coating by laser cladding, and the preparation method is as follows:

[0061] Step S1, Substrate surface pretreatment:

[0062] The surface of the C-103 alloy niobium alloy substrate was polished with 1000# SiC sandpaper until a metallic luster was exposed, indicating that the surface oxide film had been removed. The polished substrate was then cleaned with anhydrous ethanol as a cleaning agent, followed by ultrasonic cleaning for 10 minutes. After drying, the cleaning agent was removed from the substrate surface, yielding the pretreated substrate.

[0063] Step S2: Prepare a mixed powder of refractory high-entropy alloy and phenolic resin.

[0064] Commercially available spherical high-entropy alloy powder TiZrHfTaNbWo with a purity ≥99.9% and a particle size of 50~150μm, mixed in an equimolar ratio, and spherical phenolic resin powder with a purity ≥99.9% and a particle size of 50~150μm, were accurately weighed at a ratio of 9:1 using an electronic balance. The mixture was then poured into a V-type vacuum mixer, sealed, and evacuated to 0.1MPa. The mixing speed was set to 80 rpm and the mixing time to 480 minutes. The mixing process was started, and the mixing was observed and adjusted as needed. After the process was completed, the gas was released and the equipment was opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin.

[0065] Step S3, Laser Cladding:

[0066] The mixed powder prepared in step S2 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1500W, scanning speed of 20mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min. Under Ar2 atmosphere, the dried refractory high-entropy alloy powder is deposited on the pretreated substrate surface to form a high-entropy alloy coating with a certain porosity on the pretreated substrate surface.

[0067] Step S4, Methane Carbonization:

[0068] The high-entropy alloy coating prepared in step S3 above was ultrasonically cleaned in ethanol or acetone for 15 minutes and dried with nitrogen. The cleaned sample was then placed in the isothermal zone of a tube furnace, the furnace chamber was closed and sealed, and the gas and exhaust gas lines were connected. The temperature was then increased from room temperature to 1700℃ at a rate of 10℃ / min, with nitrogen or argon gas at a flow rate of 30 sccm as a protective gas. Upon reaching 1700℃, CH4 gas was switched to a flow rate of 50 sccm, and the temperature was maintained for 2 hours. The CO and CO2 content in the exhaust gas was monitored in real time using a mass spectrometer, and the gas ratio was adjusted to maintain a carbon activity of approximately 1.2. After the holding period, CH4 and H2 were shut off, and nitrogen or argon gas was used instead. The temperature was lowered by furnace cooling at a rate not exceeding 5℃ / min until it reached 300℃. The sample was then removed and air-cooled to room temperature. The final dense high-entropy alloy carbide ceramic coating was obtained.

[0069] Comparative example:

[0070] This comparative example uses high-entropy carbide powder as raw material and employs thermal spraying to directly prepare a high-entropy carbide ceramic coating.

[0071] Step 1: Material Preparation

[0072] High-entropy carbide powder (TiZrHfTaNb)C with a purity ≥99.5% and a particle size of 5~45μm was selected, dried, and sealed for storage. The surface of the alloy steel substrate was polished with 1000# SiC sandpaper until a metallic luster was exposed, indicating that the surface oxide film had been removed. The polished substrate was then cleaned with anhydrous ethanol as a cleaning agent, and ultrasonically cleaned for 10 minutes. After drying, the cleaning agent on the substrate surface was removed, yielding the pretreated substrate.

[0073] Step 2: Thermal spraying process

[0074] Debug the atmospheric plasma spraying equipment, ensuring a stable plasma arc is formed with the main gas (argon 30~50L / min) and auxiliary gas (hydrogen 5~10L / min), and a power supply of 20~50kW. Control the spraying distance at 100~150mm, the powder feed rate at 20~50g / min, and the spray gun spraying in a zigzag pattern at a speed of 100~300mm / s, with a single layer thickness of 50~100μm. Allow a 30-second interval between each layer to allow the coating to cool to ≤100℃ before applying additional layers. During the process, monitor the substrate temperature using an infrared thermal imager (fluctuation ≤±20℃), and record parameters such as voltage and gas flow rate every 5 minutes to ensure stable powder feeding (fluctuation ≤±5%). This will yield the desired high-entropy carbide ceramic coating. Its SEM image is shown below. Figure 8 As shown, the coating has obvious pores (such as...). Figure 8 -c), indicating that the coating has high porosity; at the same time, unmelted powder (such as...) can also be observed in the coating. Figure 8 -d), high porosity and unmelted powder weaken the coating adhesion. The results show that the coating has weak adhesion and high porosity. In addition, considering the actual process conditions, the preparation cost of this type of coating is also high.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a laser cladded high entropy alloy carbide ceramic coating, characterized in that, The application provides a mixed powder of a high-entropy alloy and a phenolic resin; the mixed powder is solidified by laser cladding technology on a substrate surface to form a coating layer metallurgically combined with the substrate; and the coating layer is carbonized under the synergistic effect of double carbon sources to obtain a final dense high-entropy alloy carbide ceramic coating layer; the porosity and structure gradient of the coating layer are controlled by adjusting the ratio of the phenolic resin and the high-entropy alloy powder. The double carbon sources are derived from the decomposition of the phenolic resin and a methane atmosphere during the laser cladding process. Specifically, the method comprises the following steps: S1, substrate surface pretreatment: 1000# SiC sandpaper is used to polish the surface of the niobium alloy substrate to remove the surface oxide layer, and the polishing is performed until the surface is exposed to metal luster; anhydrous ethanol is used as a cleaning agent to clean the polished niobium alloy substrate, and the substrate is ultrasonically cleaned for 10 minutes; and then the substrate is dried to remove the cleaning agent on the surface of the substrate, thereby obtaining a pretreated niobium alloy substrate; S2, preparation of mixed powder of refractory high-entropy alloy and phenolic resin: the high-entropy alloy powder and the phenolic resin powder are weighed and then poured into a V-shaped vacuum powder mixer, which is sealed and vacuumized to 0.08 MPa-0.1 MPa; the rotation speed is set to 60-80 revolutions / minute, and the mixing time is set to 360-480 minutes; the powder mixing is started, and after the mixing is completed, the device is opened after being degassed, thereby obtaining the mixed powder of the refractory high-entropy alloy and the phenolic resin; S3, laser cladding: the mixed powder prepared in step 2 is loaded into a powder feeder, and the parameters of the laser cladding are set; the dried refractory high-entropy alloy powder is deposited on the pretreated substrate surface in an Ar2 atmosphere, thereby forming a high-entropy alloy coating layer with a porosity of 12-30% on the pretreated substrate surface; S4, methane carbonization: the high-entropy alloy coating layer prepared in step 3 is ultrasonically cleaned in ethanol or acetone for 10-15 minutes and dried with nitrogen; then the cleaned sample is placed in a tube furnace constant temperature zone, the furnace chamber is closed and sealed, the temperature gradient is adjusted, and the protective gas and methane are switched with the temperature, and then the temperature is lowered to room temperature, thereby obtaining a dense high-entropy alloy carbide ceramic coating layer; In S2, the high-entropy alloy powder is a mixture of spherical metal powders of any five or more than five of Ti, Zr, Hf, Ta, Nb and Mo, and the particle size of the high-entropy alloy powder is 5-50 μm; the particle size of the phenolic resin powder is less than 30 μm, and the mass ratio of the high-entropy alloy powder to the phenolic resin powder is (7:3)-(9:1).

2. The method of claim 1, wherein the high-entropy alloy carbide ceramic coating is prepared by laser cladding. In S3, synchronous powder feeding is used, and the laser cladding parameters are as follows: the laser power is 1200-1500 W, the scanning speed is 8 mm / s-20 mm / s, the cladding overlap rate is 50%, the gas flow of Ar2 is 15 L / min, and the powder feeding speed is 1.6 r / min.

3. The method of claim 1, wherein the high-entropy alloy carbide ceramic coating is prepared by laser cladding. In S3, the thickness of the high-entropy alloy coating layer is 0.5-0.68 mm.

4. The method of claim 1, wherein the high-entropy alloy carbide ceramic coating is prepared by laser cladding. In S4, the temperature gradient adjustment and the switching of the protective gas and the methane include the following stages: (1) the temperature is raised to 1400-1700 ℃ at a rate of 10 ℃ / min from room temperature, and nitrogen or argon with a flow rate of 20-30 sccm is introduced as a protective gas during the temperature rising process. (2) After reaching 1400-1700℃, switch to CH4 gas with a flow rate of 50 sccm, and keep for 2 hours. Monitor the CO and CO2 contents in the tail gas in real time by using a mass spectrometer, and adjust the gas ratio to make the carbon activity 1.2; (3) After the heat preservation is completed, the CH4 and H2 are closed, and nitrogen or argon is replaced.

5. The method of claim 1, wherein the high-entropy alloy carbide ceramic coating is prepared by laser cladding. In step S4, the cooling rate is lower than 5℃ / min, and after being reduced to 300℃, the sample is taken out and air-cooled to room temperature.

6. A laser cladded high entropy alloy carbide ceramic coating, characterized in that, The laser cladding high-entropy alloy carbide ceramic coating is prepared by the preparation method in any one of claims 1-5, and has a single FCC solid solution structure.

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