Preparation method of single-phase high-entropy carbide ultrahigh-temperature ceramic coating

Abstract

This invention discloses a method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating, comprising the following steps: (1) mixing high-purity TiC, ZrC, NbC, HfC and TaC powders in an equimolar ratio, and adding deionized water, polyvinyl alcohol, polyethylene glycol and n-butanol to the mixed powder to form a slurry; (2) performing spray granulation to obtain powder with a particle size of less than or equal to 40 μm; (3) selecting Ta10W as the matrix material, polishing the surface of the matrix to be clad with sandpaper, and performing ultrasonic cleaning; (4) performing high-speed laser cladding, with a laser power of 2.5-3 kW, a scanning speed of 40-100 mm / s, a powder feeding rate of 1.5-2.2 r / min, a defocusing amount of 0-2 mm, and an overlap rate of 70%-85%. This invention realizes a one-step in-situ synthesis from raw material mixed powder to the final high-entropy ultra-high temperature ceramic coating material, obtaining a coating with a functional gradient structure.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy ultra-high temperature ceramic materials, specifically relating to a method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating. Background Technology

[0002] Ultra-high temperature ceramics, due to their high melting point (over 3000℃), strong thermal conductivity, excellent mechanical properties, and good oxidation resistance, are widely used in extreme environment engineering. Based on the "high-entropy" materials design theory, high-entropy ultra-high temperature ceramics have emerged. Compared to single-component ultra-high temperature ceramics, they exhibit a series of novel properties, becoming a research hotspot and key development direction in this field. However, the core challenge in the current research and development of high-entropy ultra-high temperature ceramics lies in the complexity of the solution pretreatment of their precursor powders. This bottleneck is prevalent in the preparation processes of bulk materials and coatings, such as hot pressing sintering, spark plasma sintering, radio frequency inductively coupled plasma spheroidization, and vacuum plasma spraying. Therefore, the preparation of high-entropy ultra-high temperature ceramic materials typically requires a large energy input, long processing time, and complex processes.

[0003] Since 2017, high-speed laser cladding technology has become a revolutionary breakthrough in the field of surface coating. Its core principle lies in the controllable distribution of laser energy, with the vast majority of the energy acting directly on the powder in flight, causing it to melt or partially melt before reaching the substrate. By fully utilizing its "controllable energy distribution" characteristic, most of the laser energy is focused on a mixture of multi-principal ceramic raw material powders in flight. Through the extremely high energy density of the laser beam, a high-temperature molten pool can be instantly formed on the substrate surface. This molten pool can not only completely melt raw material powders composed of five or more components, but also provide a strong energy driving force, promoting atomic-level diffusion and uniform mixing between the components. Summary of the Invention

[0004] The purpose of this invention is to propose a method for preparing single-phase high-entropy carbide ultra-high temperature ceramic coatings, which eliminates the cumbersome multi-step processing steps of traditional high-entropy ultra-high temperature ceramic powders and realizes a "one-step" in-situ synthesis from raw material mixing powder to the final high-entropy ultra-high temperature ceramic coating material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating includes the following steps: (1) Mix high-purity TiC, ZrC, NbC, HfC and TaC powders in an equimolar ratio, and add deionized water, polyvinyl alcohol, polyethylene glycol and n-butanol to the resulting mixed powder to make a slurry; (2) Spray granulation is carried out by centrifugal spray drying. The feed temperature is 190-240℃, the discharge temperature is 130-160℃, the atomizer frequency is 48-50 Hz, and the feed rate is 8-10 r / min to obtain near-spherical granulated agglomerated powder. The obtained powder is sieved to obtain spray granulated powder with a particle size of 10-40μm. (3) Select Ta10W as the substrate material, sand the substrate surface to be clad with sandpaper, and then perform ultrasonic cleaning pretreatment; (4) High-speed laser cladding is performed with a laser power of 2.5-3 kW, a scanning speed of 40-100 mm / s, a powder feeding rate of 1.5-2.2 r / min, a defocusing amount of 0-2 mm, an overlap rate of 70%-85%, a spot diameter of 1-3 mm, and argon as the inert protective gas.

[0006] Preferably, in step (1), the purity of each raw material powder is above 99.99%, and the particle size is 100-500nm.

[0007] Preferably, in step (1), the mixed powder is mixed with deionized water, polyvinyl alcohol, polyethylene glycol and n-butanol in a mass / volume ratio of 100 g : 90-120 mL : 10-15 g : 1-3 g : 1-2 mL.

[0008] Preferably, in step (1), the material is ground at 400-600 rpm for 10-14 h in a cylindrical ball mill to prepare a uniform and stable slurry.

[0009] Preferably, in step (2), the powder is subjected to ultrasonic vibration sieving at a frequency of 30-50 kHz for 5-15 min.

[0010] Preferably, in step (2), the spray-granulated powder is dried at 80-100°C to improve the flowability of the powder.

[0011] Preferably, in step (4), a robotic arm is used in conjunction with a laser cladding head to perform high-speed laser cladding. The laser and powder focus are superimposed and focused on the substrate surface at a distance of 0-2 mm above the substrate surface, and cladding is performed using a "bow-shaped" scanning trajectory.

[0012] The beneficial effects of this invention are: 1. The extremely high energy density of the laser beam can instantly form a high-temperature molten pool on the substrate surface. This molten pool can not only completely melt raw material powders composed of five or more components, but also provide a strong energy driving force to promote atomic-level diffusion and uniform mixing between components. This eliminates the cumbersome multi-step processing steps of traditional high-entropy ultra-high temperature ceramic powders, realizing a "one-step" in-situ synthesis from raw material mixing powder to the final ceramic coating material.

[0013] 2. Formation of single-phase high-entropy ceramic phase: The transformation of five constituent refractory metal carbides (TiC, ZrC, NbC, HfC, TaC) into single-phase high-entropy ceramic solid solution (i.e. (TiZrNbHfTa)C) was successfully achieved, verifying the feasibility of high-entropy design.

[0014] 3. Unique mechanical properties: A coating with a functionally graded structure is obtained, with an outer layer hardness of 2050.54±433.68HV0.5 and an inner layer toughness of 3.36±0.56 MPa·m. 1 / 2 This significantly improves the overall mechanical performance.

[0015] 4. Strong interfacial bonding: Achieves high-quality metallurgical bonding between the coating and the substrate, ensuring excellent coating-substrate adhesion. Attached Figure Description

[0016] Figure 1 The cross-sectional morphology of the coating obtained in Example 1 is shown.

[0017] Figure 2 The image shows the XRD pattern of the coating obtained in Example 1.

[0018] Figure 3 (a) shows the hardness distribution of the coating cross section obtained in Example 1; Figure 3 (b) shows the fracture toughness distribution of the coating section obtained in Example 1.

[0019] Figure 4 The image shows the cross-sectional morphology of the coating obtained in Example 2.

[0020] Figure 5 The image shows the cross-sectional morphology of the coating obtained in Example 3. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below through embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0022] This invention uses five refractory metal carbides—TiC, ZrC, NbC, HfC, and TaC—as raw materials to directly synthesize a (TiZrNbHfTa)C single-phase high-entropy ultra-high temperature ceramic coating on the surface of a Ta10W alloy using high-speed laser cladding technology. This single-phase high-entropy ultra-high temperature ceramic coating is a dense gradient coating that forms a good metallurgical bonding interface with the Ta10W substrate, exhibiting very few defects. The coating possesses a hard outer layer (2050.54±433.68 HV0.5) and a tough inner layer (3.36±0.56 MPa·m). 1 / 2 The structure exhibits excellent mechanical properties. Example 1

[0023] High-purity (99.99%) and finer particle size (100-500 nm) commercial ceramic powders TiC, ZrC, NbC, HfC, and TaC were used as raw material powders due to their high surface energy. The five ultra-high temperature ceramic powders were mixed in an equimolar ratio (1:1:1:1:1) to prepare a slurry. The mixed powder was then combined with deionized water, polyvinyl alcohol, polyethylene glycol, and n-butanol at a mass / volume ratio of 100 g : 108.9 mL : 11.1 g : 2.2 g : 1 mL. The mixture was ground in a ball mill at 500 rpm for 12 hours to prepare a uniform and stable ceramic slurry. Subsequently, the slurry was granulated using a centrifugal spray granulation system with the following process parameters: feed temperature 200℃, discharge temperature 130℃, atomizer frequency 50 Hz, and feed rate 10 r / min, ultimately obtaining near-spherical agglomerated powder. Finally, the obtained powder was ultrasonically vibrated and sieved through a -325 mesh sieve (ultrasonic frequency 41 kHz, time 10 min). The resulting powder had a particle size of less than or equal to 40 μm, which is suitable for high-speed laser cladding.

[0024] The substrate is a Ta10W alloy with dimensions of 40×20×5 mm. High-speed laser cladding is performed using a robotic arm in conjunction with a laser cladding head, with the laser and powder focal points overlapping and located 1 mm above the substrate surface. During high-speed laser cladding, the laser spot size is 2 mm, the working distance is 18 mm, and the scanning trajectory is a "bow-shaped" pattern. The process parameters for this embodiment are: laser power 2.7 kW; scanning speed 60 mm / s; powder feed rate 2 r / min; overlap rate 75%; spot diameter 2 mm; defocusing amount 1 mm; and argon as the protective gas.

[0025] Samples were prepared using diamond wire cutting, and the cross-section of the sample was polished to a high shine. The cross-sectional morphology was then observed using a scanning electron microscope. The results are as follows: Figure 1 As shown. XRD analysis was used to analyze the phase composition within the coating to determine whether a (TiZrNbHfTa)C high-entropy ceramic phase had formed. The results are as follows. Figure 2 As shown.

[0026] from Figure 1 As can be seen, a strong metallurgical bond is formed between the coating and the substrate. The coating thickness is uniform at approximately 340 μm, with only slight microporosity and microcracks observed, indicating excellent metallurgical bonding performance and physicochemical compatibility.

[0027] Figure 2 The image shows the XRD pattern of the coating obtained in Example 1. Figure 2 It can be seen that after high-speed laser cladding, these five independent metal carbide phases are transformed into a (TiZrNbHfTa)C solid solution phase, verifying the feasibility of the high-entropy design. This is because the high driving force of high-speed laser cladding causes the five carbides to be replaced and dissolved. The original powder from spray granulation melts into droplets under the action of a high-energy laser beam, and then diffuses and polymerizes on the substrate surface.

[0028] Figure 3 (a) shows the hardness distribution of the coating cross section obtained in Example 1; Figure 3 (b) shows the fracture toughness distribution of the coating section obtained in Example 1. From Figure 3 The coating exhibits a gradient structure: the outer layer has a hardness of 2050.54±433.68 HV0.5, while the inner layer has a toughness of 3.36±0.56 MPa·m. 1 / 2 . Example 2

[0029] High-purity (99.99%) and finer particle size (100-500 nm) commercial ceramic powders TiC, ZrC, NbC, HfC, and TaC were used as raw material powders due to their high surface energy. The five ultra-high temperature ceramic powders were mixed in an equimolar ratio (1:1:1:1:1) to prepare a slurry. The mixed powder was then combined with deionized water, polyvinyl alcohol, polyethylene glycol, and n-butanol at a mass / volume ratio of 100 g : 108.9 mL : 11.1 g : 2.2 g : 1 mL. The mixture was ground in a ball mill at 500 rpm for 12 hours to prepare a uniform and stable ceramic slurry. Subsequently, the slurry was granulated using a centrifugal spray granulation system with the following process parameters: feed temperature 200℃, discharge temperature 130℃, atomizer frequency 50 Hz, and feed rate 10 r / min, ultimately obtaining near-spherical agglomerated powder. Finally, the obtained powder was ultrasonically vibrated and sieved through a -180 mesh + 325 mesh sieve (ultrasonic frequency 41 kHz, time 10 min). The resulting powder had a particle size of approximately 40-100 μm, which is suitable for high-speed laser cladding.

[0030] The substrate is a Ta10W alloy with dimensions of 40×20×5 mm. High-speed laser cladding is performed using a robotic arm in conjunction with a laser cladding head, with the laser and powder focal points overlapping and located 1 mm above the substrate surface. During high-speed laser cladding, the laser spot size is 2 mm, the working distance is 18 mm, and the scanning trajectory is a "bow-shaped" pattern. The process parameters for this embodiment are: laser power 2.7 kW; scanning speed 60 mm / s; powder feed rate 2 r / min; overlap rate 75%; spot diameter 2 mm; defocusing amount 1 mm; and argon as the protective gas.

[0031] Samples were prepared using diamond wire cutting, and the cross-section of the sample was polished to a high shine. The cross-sectional morphology was then observed using an optical microscope. The results are as follows: Figure 4 As shown. From Figure 4 As can be seen, when the powder particle size is large, the coating exhibits numerous cracks and pores, with a large number of coating fragments peeling off on the surface. This is mainly due to the incomplete melting of large ceramic powder particles. Example 3

[0032] High-purity (99.99%) and finer particle size (100-500 nm) commercial ceramic powders TiC, ZrC, NbC, HfC, and TaC were used as raw material powders due to their high surface energy. The five ultra-high temperature ceramic powders were mixed in an equimolar ratio (1:1:1:1:1) to prepare a slurry. The mixed powder was then combined with deionized water, polyvinyl alcohol, polyethylene glycol, and n-butanol at a mass / volume ratio of 100 g : 108.9 mL : 11.1 g : 2.2 g : 1 mL. The mixture was ground in a ball mill at 500 rpm for 12 hours to prepare a uniform and stable ceramic slurry. Subsequently, the slurry was granulated using a centrifugal spray granulation system with the following process parameters: feed temperature 200℃, discharge temperature 130℃, atomizer frequency 50 Hz, and feed rate 10 r / min, ultimately obtaining near-spherical agglomerated powder. Finally, the obtained powder was ultrasonically vibrated and sieved through a 180-mesh sieve (ultrasonic frequency 41 kHz, time 10 min). The resulting powder had a particle size of approximately 10-40 μm, which is suitable for high-speed laser cladding.

[0033] The substrate is a Ta10W alloy with dimensions of 40×20×5 mm. High-speed laser cladding is performed using a robotic arm in conjunction with a laser cladding head, with the laser and powder focal points overlapping and located 1 mm above the substrate surface. During high-speed laser cladding, the laser spot size is 2 mm, the working distance is 18 mm, and the scanning trajectory is a "bow-shaped" pattern. The process parameters for this embodiment are: laser power 2.7 kW; scanning speed 100 mm / s; powder feed rate 2 r / min; overlap rate 75%; spot diameter 2 mm; defocusing amount 1 mm; and argon as the protective gas.

[0034] Samples were prepared using diamond wire cutting, and the cross-section of the sample was polished to a high shine. The cross-sectional morphology was then observed using an optical microscope. The results are as follows: Figure 5 As shown. From Figure 5 As can be seen, when the scanning speed is too fast, the heat input to the substrate surface decreases, resulting in a large number of defects at the coating-substrate interface. Due to the numerous defects at the coating-substrate interface, a small portion of the coating peels off under internal stress.

Claims

1. A method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating, characterized in that, Includes the following steps: (1) Mix high-purity TiC, ZrC, NbC, HfC and TaC powders in an equimolar ratio, and add deionized water, polyvinyl alcohol, polyethylene glycol and n-butanol to the resulting mixed powder to make a slurry; (2) Spray granulation is carried out by centrifugal spray drying. The feed temperature is 190-240℃, the discharge temperature is 130-160℃, the atomizer frequency is 48-50 Hz, and the feed rate is 8-10 r / min to obtain near-spherical granulated agglomerated powder. The obtained powder is sieved to obtain spray granulated powder with a particle size of less than or equal to 40μm. (3) Select Ta10W as the substrate material, sand the substrate surface to be clad with sandpaper, and then perform ultrasonic cleaning pretreatment; (4) High-speed laser cladding is performed with a laser power of 2.5-3 kW, a scanning speed of 40-100 mm / s, a powder feeding rate of 1.5-2.2 r / min, a defocusing amount of 0-2 mm, an overlap rate of 70%-85%, a spot diameter of 1-3 mm, and argon as the inert protective gas.

2. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1, characterized in that, In step (1), the purity of each raw material powder is above 99.99%, and the particle size is 100-500 nm.

3. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1 or 2, characterized in that, In step (1), the mixed powder is mixed with deionized water, polyvinyl alcohol, polyethylene glycol and n-butanol in a mass / volume ratio of 100 g : 90-120 mL : 10-15 g : 1-3 g : 1-2 mL.

4. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1 or 2, characterized in that, In step (1), a uniform and stable slurry is prepared by grinding at 400-600 rpm for 10-14 h in a cylindrical ball mill.

5. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1 or 2, characterized in that, In step (2), the powder is subjected to ultrasonic vibration sieving at a frequency of 30-50 kHz for 5-15 min.

6. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1 or 2, characterized in that, In step (2), the spray-granulated powder is dried at 80-100°C to improve the flowability of the powder.

7. The method for preparing a single-phase high-entropy carbide ultra-high temperature ceramic coating according to claim 1 or 2, characterized in that, In step (4), a robotic arm is used in conjunction with a laser cladding head to perform high-speed laser cladding. The laser and powder focus are superimposed and focused on the substrate surface at a distance of 0-2 mm above the substrate surface, and cladding is performed using a "bow-shaped" scanning trajectory.

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