Preparation method and application of ceramicized high-entropy alloy powder with hard outer shell and tough inner core

Abstract

The application relates to a preparation method of a ceramicized high-entropy alloy powder with a hard outer shell and a soft inner core and application thereof, and aims to solve the problem of uneven distribution of ceramic strengthening phases in a coating. The preparation method of the ceramicized high-entropy alloy powder with the hard outer shell and the soft inner core comprises the following steps: firstly, high-entropy alloy powder is placed in a cavity of a high-temperature nitriding furnace, first vacuumizing treatment is carried out, nitrogen is introduced after the vacuum degree reaches 0.01 MPa, and second vacuumizing treatment is carried out; secondly, after the second vacuumizing treatment, nitrogen is introduced into the cavity of the high-temperature nitriding furnace, and nitriding treatment is carried out at a temperature of 480-1200 DEG C; and thirdly, after the nitriding treatment, the temperature in the high-temperature nitriding furnace is reduced to room temperature. The high-temperature nitriding process is adopted to prepare the ceramicized high-entropy alloy powder with the hard outer shell and the soft inner core, the uniform distribution of the surface protective coating is realized from the aspect of powder raw material, and the hardness and wear resistance of the coating are improved.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy alloy materials technology, specifically relating to a method for preparing core-shell structured ceramicized high-entropy alloy powder and its application. Background Technology

[0002] High-entropy alloy coatings exhibit excellent wear resistance and high-temperature stability due to their multi-principal element characteristics. While introducing ceramic phases into high-entropy alloys can meet the performance requirements of components under actual working conditions, the poor thermo-physical compatibility between the ceramic phase and the metal powder can easily lead to uneven coating distribution, resulting in defects such as pores and cracks, significantly reducing the service life of the coating. Therefore, maximizing the uniform distribution of ceramic reinforcing phases and minimizing coating defects at the powder material level while ensuring the high performance of high-entropy alloy surface protective coatings is a major challenge that urgently needs to be addressed. Summary of the Invention

[0003] To address the problem of uneven distribution of ceramic reinforcing phases in coatings, this invention provides a method for preparing core-shell structured ceramic high-entropy alloy powder with an external hardness and internal toughness, and its application.

[0004] The preparation method of the core-shell structured ceramicized high-entropy alloy powder with a hard outer layer and tough inner layer of the present invention is carried out according to the following steps:

[0005] First, place the high-entropy alloy powder in the chamber of a high-temperature nitriding furnace and perform a first vacuum treatment. After the vacuum degree reaches 0.01 MPa, introduce nitrogen into the chamber for a second vacuum treatment.

[0006] Second, after the second vacuuming process, nitrogen gas is introduced into the chamber, and the nitrogen pressure in the chamber is controlled at 0.2-1.2 MPa. Nitrification is then carried out at a temperature of 480-1200℃.

[0007] 3. After nitriding treatment, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell.

[0008] The main elements of high-entropy alloys include three or more of the following: Ni, Cr, Ti, Zr, Al, V, W, Mo, Fe, and Co.

[0009] The application of the core-shell structure ceramicized high-entropy alloy powder of the present invention is to use laser cladding, spraying or plasma cladding processes to clad the core-shell structure ceramicized high-entropy alloy powder onto the surface of the matrix material to form a protective cladding layer on the surface of the composite material.

[0010] This invention employs a high-temperature nitriding process, utilizing the high hardness of the infiltrated layer to prepare a core-shell structured high-entropy alloy ceramicized powder with an outer hardness and an inner toughness. This ceramicized high-entropy alloy powder is then applied to technologies such as laser cladding, spraying, and plasma cladding. Under surface modification, the ceramic hard shell separates from the metal core, forming a uniform protective coating on the composite material surface. This achieves uniform distribution of the protective coating at the powder raw material level, while simultaneously improving the coating's hardness, wear resistance, and other properties. This provides new ideas and solutions for the development and design of high-performance high-entropy alloy coatings. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the ceramicization process of high-entropy alloy powder with a hard outer and tough inner core-shell structure according to the present invention.

[0012] Figure 2 The surface morphology and elemental distribution diagram of the core-shell structured, hard-outer-tough-inner-high-entropy alloy ceramic powder obtained in Example 1 are shown.

[0013] Figure 3 The image shows the XRD pattern of the high-entropy alloy ceramic powder with a core-shell structure that is hard on the outside and tough on the inside, obtained in Example 1. Detailed Implementation

[0014] Specific Implementation Method 1: The preparation method of the core-shell structure ceramicized high-entropy alloy powder with hard outer layer and tough inner layer in this implementation method is carried out according to the following steps:

[0015] First, place the high-entropy alloy powder in the chamber of a high-temperature nitriding furnace and perform a first vacuum treatment. After the vacuum degree reaches 0.01 MPa, introduce nitrogen into the chamber for a second vacuum treatment.

[0016] Second, after the second vacuuming process, nitrogen gas is introduced into the chamber, and the nitrogen pressure in the chamber is controlled at 0.2-1.2 MPa. Nitrification is then carried out at a temperature of 480-1200℃.

[0017] 3. After nitriding treatment, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell.

[0018] The main elements of high-entropy alloys include three or more of the following: Ni, Cr, Ti, Zr, Al, V, W, Mo, Fe, and Co.

[0019] The core-shell structured ceramic high-entropy alloy powder prepared in this embodiment contains either a BCC phase or an FCC phase.

[0020] This embodiment provides a method for preparing a core-shell structured high-entropy alloy powder with a hard outer shell and a tough inner shell by ceramicization. A nitride ceramic hard shell is prepared on the surface of the high-entropy alloy powder using a high-temperature nitriding process. Due to the sluggish diffusion effect of the high-entropy alloy at high temperatures, the multi-principal component co-reaction process of the high-entropy alloy is slow. Therefore, the thickness of the multi-element ceramic reinforced shell can be adjusted by controlling the nitriding time to meet different performance requirements, thus overcoming the limitation of uneven ceramic phase distribution and improving the overall performance of the coating.

[0021] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that the particle size of the high-entropy alloy powder in step one is 45-150 μm.

[0022] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the particle size of the high-entropy alloy powder is 80-150 μm.

[0023] The purpose of limiting the powder particle size in this embodiment is to provide a larger surface area and better air permeability, thereby ensuring better nitriding kinetics and achieving a higher nitriding rate.

[0024] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the purity of the nitrogen gas introduced in Step One and Step Two is 99.99%.

[0025] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the flow rate of nitrogen gas introduced in step 1 is controlled to be 400-600 mL / min.

[0026] In this embodiment, the nitrogen flow rate should not be too high, as it may easily disperse the metal powder.

[0027] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that in step two, the temperature is increased to the nitriding treatment temperature at a heating rate of 5 to 10 °C / min.

[0028] The preferred heating rate in this embodiment is 8°C / min.

[0029] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the nitriding treatment time in step two is 2 to 6 hours.

[0030] The preferred nitriding treatment time in this embodiment is 3 to 5 hours.

[0031] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the high-temperature nitriding furnace in step three is cooled to room temperature by air cooling.

[0032] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the nitriding layer thickness of the core-shell structure ceramicized high-entropy alloy powder in step three is 3 to 20 μm.

[0033] In this embodiment, the thickness of the nitrided layer is preferably 5 to 10 μm.

[0034] Example 1: The preparation method of the core-shell structure ceramicized high-entropy alloy powder with hard outer layer and tough inner layer in this example is carried out according to the following steps:

[0035] First, place the AlCrWTiMo high-entropy alloy powder with an atomic ratio of 45-150μm into the chamber of a high-temperature nitriding furnace for the first vacuum treatment. After reaching a vacuum degree of 0.01MPa, introduce nitrogen gas with a purity of 99.99% for 5 minutes for the second vacuum treatment.

[0036] Second, after the second vacuum treatment, nitrogen gas is introduced into the chamber of the high-temperature nitriding furnace at a flow rate of 500 mL / min, and the nitrogen pressure in the chamber is controlled at 0.2 MPa. Nitriding treatment is carried out at 500℃ for 2 hours.

[0037] 3. After nitriding, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell.

[0038] The nitriding furnace in this embodiment includes a controller, a nitrogen atmosphere electric furnace, a circulating water control pump, and a gas cylinder.

[0039] The high-entropy alloy ceramicized powder obtained in this embodiment is a core-shell structure AlCrWTiMo high-entropy alloy ceramicized powder encapsulated by Al, Cr, W, Ti, and Mo nitrides. The thickness of the multi-element ceramic-reinforced outer shell is 3.4–6.2 μm, with a nanoscale hardness of 16.34–20.11 GPa; the diameter of the high-entropy alloy core structure is 31.4–112.8 μm, with a nanoscale hardness of 6.79–9.52 GPa. The elemental distribution of the powder after ceramicization treatment is as follows: Figure 2 As shown, the phase composition of the powder before and after ceramicization treatment is as follows: Figure 3 As shown, combined with Figure 2 , 3 It can be seen that a uniformly distributed multi-element ceramic reinforcing phase was successfully prepared on the surface of high-entropy alloy powder.

[0040] Example 2: The preparation method of the core-shell structure ceramicized high-entropy alloy powder with hard outer layer and tough inner layer in this example is carried out according to the following steps:

[0041] 1. Take FeCoNiMnCr high-entropy alloy blocks, crush and grind them, and transfer them to a high-energy sand mill for crushing and mixing. The solvent used is anhydrous alcohol, and the solid-liquid ratio is 40 wt.%. 1.5 wt.% of polyethylene glycol binder is also added. The slurry prepared by ball milling is spray-granulated to prepare large-particle FeCoNiMnCr high-entropy alloy powder. The high-entropy alloy powder is dried in a vacuum drying oven at 150℃ for 3 hours. The dried FeCoNiMnCr high-entropy alloy powder is sealed and stored for later use.

[0042] 2. Place FeCoNiMnCr high-entropy alloy powder with an atomic ratio of 80-150μm into the chamber of a high-temperature nitriding furnace for the first vacuum treatment. After reaching a vacuum degree of 0.01MPa, introduce nitrogen gas with a purity of 99.99% for 5 minutes for the second vacuum treatment.

[0043] Third, after the second vacuum treatment, nitrogen gas is introduced into the chamber of the high-temperature nitriding furnace at a flow rate of 500 mL / min, and the nitrogen pressure in the chamber is controlled at 0.2 MPa. Nitriding treatment is carried out at 500℃ for 2 hours.

[0044] IV. After nitriding treatment, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell.

[0045] The high-entropy alloy ceramicized powder obtained in this embodiment is a core-shell structure FeCoNiMnCr high-entropy alloy ceramicized powder encapsulated by nitrides of Fe, Co, Ni, Mn, and Cr. The thickness of the multi-element ceramic-reinforced outer shell is 3.2–6.5 μm, and the nano-hardness is 12.33–15.61 GPa. The diameter of the high-entropy alloy core structure is 45.2–122.1 μm, and the nano-hardness is 6.56–8.93 GPa.

[0046] Example 3: The preparation method of the core-shell structure ceramicized high-entropy alloy powder with hard outer layer and tough inner layer in this example is carried out according to the following steps:

[0047] First, place the AlCrWTiMo high-entropy alloy powder with an atomic ratio of 45-150μm into the chamber of a high-temperature nitriding furnace for the first vacuum treatment. After reaching a vacuum degree of 0.01MPa, introduce nitrogen gas with a purity of 99.99% for 5 minutes for the second vacuum treatment.

[0048] Second, after the second vacuum treatment, nitrogen gas is introduced into the chamber of the high-temperature nitriding furnace at a flow rate of 500 mL / min, and the nitrogen pressure in the chamber is controlled at 0.2 MPa. Nitriding treatment is carried out at 500℃ for 4 hours.

[0049] 3. After nitriding, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell.

[0050] The high-entropy alloy ceramicized powder obtained in this embodiment is a core-shell structure AlCrWTiMo high-entropy alloy ceramicized powder encapsulated by Al, Cr, W, Ti, and Mo nitrides. The thickness of the multi-element ceramic reinforced shell is 7.9–9.8 μm, and the nano-hardness is 17.53–20.37 GPa. The diameter of the high-entropy alloy core structure is 23.4–105.7 μm, and the nano-hardness is 6.88–9.89 GPa.

Claims

1. The application of core-shell structure ceramicized high-entropy alloy powder with hard outer layer and tough inner layer, characterized in that... Laser cladding, spraying, or plasma cladding processes are used to clad core-shell structure ceramicized high-entropy alloy powder onto the surface of the base material to form a protective cladding layer on the surface of the composite material. The preparation method of the core-shell structure ceramicized high-entropy alloy powder with a hard outer surface and a tough inner surface is carried out according to the following steps:

1. Place the high-entropy alloy powder in the chamber of the high-temperature nitriding furnace and perform the first vacuum treatment. After the vacuum degree reaches 0.01MPa, introduce nitrogen into the chamber and control the flow rate of nitrogen to be 400~600 mL / min. Then perform the second vacuum treatment. Second, after the second vacuum treatment, nitrogen gas is introduced into the chamber, and the nitrogen pressure in the chamber is controlled at 0.2~1.2MPa. Nitriding treatment is carried out at a temperature of 480~1200℃ for 2~6 hours, and the temperature is increased to the nitriding treatment temperature at a heating rate of 5~10℃ / min.

3. After nitriding treatment, wait for the temperature inside the high-temperature nitriding furnace to drop to room temperature to obtain a core-shell structure ceramic high-entropy alloy powder with a hard outer shell and a tough inner shell. The main elements of high-entropy alloys include three or more of the following: Ni, Cr, Ti, Zr, Al, V, W, Mo, Fe, and Co.

2. The application of the core-shell structured ceramicized high-entropy alloy powder with an outer hard and inner tough structure as described in claim 1, characterized in that... In step one, the particle size of the high-entropy alloy powder is 45~150μm.

3. The application of the core-shell structure ceramicized high-entropy alloy powder with an outer hard and inner tough structure as described in claim 2, characterized in that... The particle size of the high-entropy alloy powder is 80~150μm.

4. The application of the core-shell structured ceramicized high-entropy alloy powder with an outer hard and inner tough structure as described in claim 1, characterized in that... The purity of the nitrogen gas introduced in steps one and two is 99.99%.

5. The application of the core-shell structured ceramicized high-entropy alloy powder with an outer hard and inner tough structure according to claim 1, characterized in that... In step three, the high-temperature nitriding furnace is cooled to room temperature using air cooling.

6. The application of the core-shell structured ceramicized high-entropy alloy powder with an outer hard and inner tough structure according to claim 1, characterized in that... In step three, the nitrided layer thickness of the core-shell structured ceramic high-entropy alloy powder is 3~20μm.

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