An in-situ decomposition-strengthened face-centered Al x Method for cladding CoCr-based high entropy alloy layer

Abstract

The present invention relates to a method for in-situ decomposition strengthening of face-centered AlxCoCr high entropy alloy cladding layer. The method is characterized in that the cladding layer has the following phase composition and mass fraction: Cr2AlC: 0-3%, CrC x : 5‑14.5%, the rest is face-centered cubic structure Al x CrCoFeNi; The mass percentage of the raw material powder of the cladding layer is: Cr2AlC: 5-17.5%, and the rest is Al x CrCoFeNi high entropy powder. Cr2AlC is spherical or irregular in shape with a particle size of 15-60μm; Al x The CrCoFeNi alloy is spherical with a particle size of 45-150 μm. The cladding layer is prepared by placing the raw powders in a three-dimensional rotary mixer and thoroughly mixing them. A steel alloy substrate is used, which is then derusted and preheated. The mixed powder is then dried and placed in the powder feeder of a laser cladding machine, where it is then deposited by laser cladding to form the cladding layer.

Description

Technical field:

[0001] The present invention relates to the field of high entropy alloy cladding layer structure design, specifically an in-situ decomposition strengthening face-centered Al x A method for cladding a CoCr-based high entropy alloy layer. Background technology:

[0002] As a clean, high-quality renewable energy source, hydropower has rich development potential and huge commercial value.

[0003] Turbine blades, runners, and other flow-through components are crucial components of hydroelectric generators. High-speed, high-throughput liquid flow erodes their surfaces, easily leading to cavitation at locations such as blade edges. The resulting cavitation bubbles, when ruptured on the blade surface, cause high-frequency vibrations on the mechanical components, generating noise and impacting the stability of the mechanical system. The massive energy released by the ruptured bubbles impacts the contacting surfaces, further causing cavitation damage such as pinholes and fish-scale peeling, severely impacting their service life. This surface damage also affects the flow around the turbine, significantly impacting the turbine's operating efficiency. Furthermore, the erosion and abrasion of the turbine surface by sediment in the flow further accelerates component failure. Therefore, surface strengthening and extending its service life are key to future hydropower stations with long lifespans, high stability, high head, and large capacity.

[0004] High entropy alloy cladding layers prepared by laser cladding process have been widely researched and applied due to their excellent performance. Due to the synergistic effect of various elements in high entropy alloys, this type of material exhibits strength and toughness superior to traditional alloy materials, while also having excellent properties such as corrosion resistance and cavitation resistance. x CrCoFeNi high entropy alloys have low cost and relatively simple preparation process. They have high strength, high toughness and corrosion resistance, making them ideal raw materials for preparing high entropy alloy cladding layers. Among the elements in this type of high entropy alloy, the Al content mainly affects the phase composition of the high entropy alloy. Only when x < 0.4, Al x CrCoFeNi high entropy alloy will form a high plasticity FCC single phase composition; when x>0.4, a multiphase structure composed of FCC, BCC and B2 phases will appear in the high entropy alloy. The complex phase composition will make it difficult to ensure the uniformity of the cladding layer during the preparation process, and the cladding layer performance will be unstable. In view of this, it is necessary to use ceramic particles to FCC single phase Al x CrCoFeNi high entropy cladding layer is strengthened to improve the hardness and strength of the cladding layer. However, traditional binary ceramics, such as Al2O3, ZnO2, etc., are not as good as Al x The interface bonding strength of CrCoFeNi is weak, which can easily become the source of cracks in actual service, causing Al xCrCoFeNi high entropy cladding layer fails. Therefore, it is necessary to x Based on the face-centered cubic structure of CrCoFeNi, the ceramic reinforcement and Al x CrCoFeNi forms a strong interface bond.

[0005] The new ternary layered MAX phase ceramics are different from traditional binary ceramics. Under the high temperature of laser cladding, the A-site elements in the MAX phase will spontaneously diffuse outward and form a nano-ceramic reinforcement phase in situ. Therefore, this type of ceramic particles can play the role of solid solution strengthening and nano-particle strengthening at the same time. For example: the Al element diffusion and Al in Cr2AlC in the MAX phase under the high temperature of laser cladding x CrCoFeNi forms a strong bonding interface and simultaneously forms nano-CrC x Improve the hardness and strength of the cladding layer. Since the Al content affects the Al x The phase composition of CrCoFeNi is so that an in-situ decomposition strengthening face-centered cubic structure Al x The method of CoCrFeNi high entropy alloy cladding layer is to ensure that Al x CrCoFeNi still maintains the FCC single-phase structure, while introducing MAX phase and ceramic particles produced by in-situ decomposition as strengthening phases, which becomes the research and development focus of this patent. Summary of the invention:

[0006] The purpose of the present invention is to provide an in-situ decomposition-strengthened face-centered cubic structure Al x Method for cladding CoCrFeNi high entropy alloy layer.

[0007] The in-situ decomposition-strengthened face-centered cubic structure Al x The design principles of the raw material composite powder composition of the CoCrFeNi high entropy alloy cladding layer are as follows:

[0008] The Al element generated by the in-situ decomposition of Cr2AlC enters the Al x After the CrCoFeNi grains are formed, x≤0.4 to ensure its FCC single-phase structure. 0.3 Taking CrCoFeNi as an example, after adding Cr2AlC, due to its full decomposition during the preparation of the composite cladding layer, the Al element diffuses into the high entropy alloy. Assuming that the Al element completely enters the high entropy alloy, it can be calculated that the mass fraction of Cr2AlC cannot exceed 7.84%. Taking into account the burnout of the low melting point element Al during the preparation of the cladding layer, its mass fraction can be relaxed to 12%, that is, for Al 0.3 The maximum limit mass fraction of CrCoFeNi and Cr2AlC is 12%.

[0009] It should be noted that for Al with x < 0.4 x CrCoFeNi can design the Cr2AlC content according to the above design principles to meet the Al content in the cladding layer. x CrCoFeNi maintains the single-phase structure of FCC.

[0010] The in-situ decomposition-strengthened face-centered cubic structure Al x The composition of raw material powder for preparing CoCrFeNi cladding layer is as follows:

[0011] According to the design principle of the composite powder of the present invention, the mass percentage of the raw material powder of the cladding layer of the present invention is: Cr2AlC: 5-17.5%, and the rest is Al x CrCoFeNi high entropy alloy powder, the sum of the mass fractions of the two is 100%. In addition, the shape and particle size of the raw material powder of the cladding layer meet the following definitions: Cr2AlC: spherical or irregular shape, particle size 15-60μm; Al x CrCoFeNi: spherical, particle size 45-150μm.

[0012] The in-situ decomposition-strengthened face-centered cubic structure Al x The final composition of the CoCrFeNi cladding layer is as follows:

[0013] The present invention in situ decomposition strengthening face-centered cubic structure Al x The characteristics of the CoCrFeNi cladding layer are as follows: Cr2AlC: 0-3%; CrC x : 5-14.5%; the rest is Al x CrCoFeNi. At the same time, Al in the cladding layer x CrCoFeNi is a single-phase FCC. The sum of the mass fractions of each component is 100%.

[0014] The in-situ decomposition-strengthened face-centered cubic structure Al x The properties of CoCrFeNi cladding layer are as follows:

[0015] The porosity of the composite cladding layer is less than 3%, its thickness is 0.5-2.5mm, and the surface hardness of the composite cladding layer is 600-700HV 0.2 The cavitation erosion resistance of the composite cladding layer is tested in accordance with the ASTM G32-6 material cavitation erosion resistance test standard, and the volume loss rate is less than 0.5mm 3 / h, the erosion resistance of the composite cladding layer was tested according to the ASTM G76-2018 material erosion performance test standard, and its mass loss rate was less than 10mg / min.

[0016] The in-situ decomposition-strengthened face-centered cubic structure Al x The preparation method of CoCrFeNi cladding layer is as follows:

[0017] Step 1: According to the design principle of composite powder, Al x CrCoFeNi and Cr2AlC are placed in a three-dimensional rotary mixer and fully mixed to obtain composite raw material powder;

[0018] Step 2: Prepare a substrate using alloy steel as the cladding layer, clean and remove rust from its surface, and then preheat it to 180°C in an insulation box. Keep it warm for 3-5 minutes and then fix it on a fixture;

[0019] Step 3: After drying the composite powder, place it in the powder feeder of the laser cladding equipment, and perform laser cladding on the alloy steel substrate to prepare Cr2AlC reinforced face-centered cubic structure Al x CrCoFeNi (x≤0.4) high entropy alloy cladding layer, the specific preparation parameters are as follows: laser power 1000-1200W, scanning speed 400-800mm / min, spot diameter 3-4mm, powder feeding rate 15-20g / min, overlap rate 40-50%, defocus amount +3mm;

[0020] Step 4: The thickness of the cladding layer finally obtained is 0.5-2.5 mm; the phase composition and mass fraction of each phase in the cladding layer are: Cr2AlC: 0-3%; CrC x : 5-14.5%, the rest is Al x CrCoFeNi; Al in cladding layer x CrCoFeNi is a single-phase FCC. The sum of the mass fractions of each component is 100%.

[0021] Compared with the prior art, the present invention has the following technical advantages:

[0022] The present invention provides an in-situ decomposition-strengthened face-centered cubic structure Al x The CoCrFeNi cladding method has obvious advantages in improving the cavitation and erosion resistance of turbine blades and turbine blades. The powder used is simple to obtain and has low cost. x Based on CrCoFeNi, low-cost micron-sized powder is used to in-situ generate a nano-scale ceramic reinforcement phase, further improving the cavitation and erosion resistance of the cladding layer. The cladding layer preparation process is simple and highly repeatable, with practical application prospects and considerable economic benefits. Description of the drawings:

[0023] Figure 1 This is the 5wt.% Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3Cross-sectional morphology of CoCrFeNi cladding layer

[0024] Figure 2 This is the 9wt.% Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3 Cross-sectional morphology of CoCrFeNi cladding layer

[0025] Figure 3 The 12wt.% Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3 Cross-sectional morphology of CoCrFeNi cladding layer Specific implementation method:

[0026] Example 1

[0027] According to the mass percentage of the raw material powder of the cladding layer: Cr2AlC: 5%, Al 0.3 CrCoFeNi 95%, the sum of the two components is 100%, weigh the required powder; place the above two raw material powders in a three-dimensional rotary mixer and mix them thoroughly; use alloy steel as a cladding layer to prepare a substrate, clean and derust its surface, preheat it to 180°C in an insulation box, keep it warm for 3-5 minutes, and then fix it on a fixture; dry the above mixed powder for 30 minutes and place it in the powder feeder of the laser cladding equipment, and perform laser cladding on the alloy steel substrate according to the process described in the claim to prepare Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3 CoCrFeNi cladding layer. The final composite cladding layer is as shown in the attached Figure 1 shown.

[0028] Example 2

[0029] According to the mass percentage of raw material powder of composite cladding layer: Cr2AlC: 9%, Al 0.3 CrCoFeNi 93%, the sum of the two components is 100%, weigh the required powder; place the above two raw material powders in a three-dimensional rotary mixer and mix them thoroughly; use alloy steel as a cladding layer to prepare a substrate, clean and derust its surface, preheat it to 180°C in an insulation box, keep it warm for 3-5 minutes, and then fix it on a fixture; dry the above mixed powder for 30 minutes and place it in the powder feeder of the laser cladding equipment, and perform laser cladding on the alloy steel substrate according to the process described in the claim to prepare Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3 CoCrFeNi cladding layer. The final cladding layer is as shown in the attached Figure 2 shown.

[0030] Example 3

[0031] According to the mass percentage of raw material powder of composite cladding layer: Cr2AlC: 12%, Al0.3 CrCoFeNi 91%, the sum of the two components is 100%, weigh the required powder; place the above two raw material powders in a three-dimensional rotary mixer and mix them thoroughly; use alloy steel as a cladding layer to prepare a substrate, clean and derust its surface, preheat it to 180°C in an insulation box, keep it warm for 3-5 minutes, and then fix it on a fixture; dry the above mixed powder for 30 minutes and place it in the powder feeder of the laser cladding equipment, and perform laser cladding on the alloy steel substrate according to the process described in the claim to prepare Cr2AlC in-situ decomposition strengthening face-centered cubic structure Al 0.3 CoCrFeNi cladding layer. The final cladding layer is as shown in the attached Figure 3 shown.

Claims

1. A method for preparing face-centered Al by in-situ decomposition strengthening x The method for CrCoFeNi high entropy alloy cladding layer is characterized by: The method comprises the following steps: Step 1: Al y CrCoFeNi powder and Cr2AlC powder are placed in a three-dimensional rotary mixer and mixed thoroughly to obtain composite raw material powder. The amount of Cr2AlC added has a limit value, and the Al element in the raw material powder is converted to Al x CrCoFeNi satisfies x≤0.4; Step 2: Prepare the substrate with alloy steel as the coating, clean and remove rust from its surface, place it in an insulation box and preheat it to 180°C, keep it warm for 3-5 minutes, and then fix it on the fixture; Step 3: After drying the composite powder, place it in the powder feeder of the laser cladding equipment and perform laser cladding on the alloy steel substrate to prepare Cr2AlC reinforced face-centered cubic structure Al x The specific preparation parameters of the CrCoFeNi high entropy alloy coating are as follows: laser power 1000-1200W, scanning speed 400-800mm / min, spot diameter 3-4mm, powder feeding rate 15-20g / min, overlap rate 40-50%, and defocus amount +3mm; Step 4: The final composite coating has a thickness of 0.5 to 2.5 mm, Cr2AlC: 0-3 wt.%; CrC z :5-14.5wt.%; the rest is Al x CrCoFeNi, the Al formed x CrCoFeNi is a single-phase FCC.

2. The in-situ decomposition strengthening method for preparing face-centered Al according to claim 1 x The method for CrCoFeNi high entropy alloy cladding layer is characterized by: The mass percentage of raw material powder used to prepare composite coating is: Cr2AlC: 5-17.5%, the rest is Al y CrCoFeNi high entropy alloy powder, the sum of the mass fractions of the two is 100%; in addition, the shape and particle size of the composite coating raw material powder meet the following definitions: Cr2AlC: spherical or irregular shape, particle size 15-60μm; Al y CrCoFeNi: spherical, particle size 45-150μm.

3. The in-situ decomposition strengthening method for preparing face-centered cubic Al according to claim 1 x The coating prepared by the CrCoFeNi high entropy cladding method has a porosity of less than 3%, a thickness of 0.5-2.5 mm, and a surface hardness of 600-700 HV. 0.2 The cavitation erosion resistance of the composite coating was tested according to the ASTM G32-6 material cavitation erosion resistance test standard, and the volume loss rate was less than 0.5mm 3 / h, the erosion resistance of the composite coating was tested according to the ASTM G76-2018 material erosion performance test standard, and its mass loss rate was less than 10mg / min.

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