Laser cladding high-entropy alloy coating and preparation method thereof

Abstract

This invention discloses a laser-clad high-entropy alloy coating and its preparation method. The coating consists of two layers: the first layer contains an in-situ generated TiC ceramic phase with increasing concentration, and the second layer contains Mo-coated SiC and the in-situ generated TiC ceramic phase, both uniformly distributed in the second layer. This coating exhibits excellent hardness, wear resistance, and corrosion resistance. In the first layer, TiC and Mo elements improve the density and stability of the passivation film, enhancing the coating's corrosion resistance. The top TiC is redistributed uniformly under remelting and ultrasonic treatment, increasing the hardness of the first layer and improving the interfacial adhesion. In the second layer, the uniform distribution of TiC and Mo-coated SiC mutually enhances the coating's hardness. Simultaneously, the Mo-coated SiC particles replace some of the TiC, preventing galvanic corrosion caused by the potential difference between TiC and the CoCrFeNiMo matrix. The strength transitions gradually from the first to the second layer, avoiding the problem of easy detachment between the coatings.

Description

Technical Field

[0001] This invention relates to a high-entropy alloy coating prepared by laser cladding, and more particularly to a laser-clad high-entropy alloy coating and its preparation method. Background Technology

[0002] High-entropy alloys, also known as multi-principal-element alloys, are composed of 5 to 13 elements, with each element's molar ratio ranging from 5% to 35%. They overcome the limitations of traditional metallic material synthesis by combining multiple metallic elements to obtain alloy materials with excellent properties such as high hardness, high strength, and corrosion resistance. CoCrFeNi-based high-entropy alloys, with their stable single-phase face-centered cubic structure, good mechanical properties, and excellent corrosion resistance, have been widely used and researched. However, the mechanical strength of CoCrFeNi-based high-entropy alloys is relatively low, failing to meet the requirements for high-strength, high-hardness components. TiC is a chemically stable ceramic material with a high melting point, high hardness, and low density. Adding TiC ceramic reinforcing phases can improve the strength and hardness of CoCrFeNi-based high-entropy alloys. However, TiC is unevenly distributed and prone to agglomeration in CoCrFeNi coatings, significantly affecting its strengthening effect on coating hardness. Ultrasonic-assisted laser cladding technology can promote the uniform distribution of TiC in CoCrFeNi coatings, making TiC particles less prone to agglomeration and significantly improving coating hardness, but at the cost of a noticeable decrease in corrosion resistance. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to improve the hardness, wear resistance and corrosion resistance of CoCrFeNi-based high-entropy alloys, and to provide a laser cladding high-entropy alloy coating and its preparation method.

[0004] Technical solution: The laser cladding high-entropy alloy coating of the present invention has a molar ratio of Fe, Cr, Co, Ni and Mo metal powders of 1:1:1:1:0.1-0.4. The coating consists of two layers. The first layer near the substrate material also contains an in-situ generated TiC ceramic phase, the content of which increases from bottom to top. The second layer also contains Mo-coated SiC and an in-situ generated TiC ceramic phase, both of which are uniformly distributed in the second layer.

[0005] Furthermore, the molar ratio of Fe, Cr, Co, Ni, and Mo metal powders in the first coating is 1:1:1:1:0.1-0.4.

[0006] Furthermore, the molar ratio of Ti to C in the first coating is 1:1, and the mass percentage of TiC in the first coating is 7-12%. The lower density of TiC compared to the CoCrFeNiMo matrix allows the TiC content to increase sequentially from bottom to top, reducing the potential difference between TiC and the CoCrFeNiMo matrix near the substrate material and preventing galvanic corrosion. Simultaneously, the in-situ generated TiC particles are less prone to agglomeration and have more uniform dispersion, refining the grain size within the matrix and providing more diffusion channels. This facilitates the rapid aggregation of passivation elements to form a denser passivation film. Mo elements enhance the density of the passivation film and improve the coating's corrosion resistance. In addition, the sequential increase of TiC particles from bottom to top refines the grain size, increases the number of grain boundaries to prevent dislocation slip, and gradually enhances the hardness and strength of the coating.

[0007] Furthermore, the thickness of the first coating is 0.6-1.2 mm.

[0008] Furthermore, the molar ratio of Fe, Cr, Co, Ni, and Mo metal powders in the second coating is 1:1:1:1:0.1-0.3.

[0009] Furthermore, in the second coating, the molar ratio of Ti to C is 1:1, the mass percentage of TiC in the second coating is 3-5%, and the mass percentage of Mo-coated SiC in the second coating is 1-3%. Ultrasonic dispersion refines the particles and prevents further aggregation, promoting the uniform distribution of TiC and Mo-coated SiC as reinforcing phases in the second coating. This refines the matrix grains, prevents dislocation slip, and plays a role in particle reinforcement, thereby improving the hardness of the coating. At the same time, Mo-coated SiC improves the interfacial bonding strength with the CoCrFeNiMo matrix. Mo-coated SiC partially replaces TiC, avoiding the increase in TiC particles that would create a greater potential difference between TiC and the CoCrFeNiMo matrix, leading to galvanic corrosion. The Mo coating can also prevent SiC from decomposing during laser cladding and combining with Cr to form Cr7C3, which would reduce the corrosion resistance of the coating, further improving the corrosion resistance of the second coating.

[0010] Furthermore, the thickness of the second coating is 1.2-1.8 mm.

[0011] Furthermore, the TiC deposited on top of the first coating is re-dispersed uniformly under the action of ultrasonic dispersion and remelting, which improves the bonding performance between the first and second coatings; in addition, the strength of the first coating gradually increases from the second coating, avoiding the problem of easy peeling between the coatings.

[0012] The method for preparing a laser cladding high-entropy alloy coating according to the present invention includes the following steps:

[0013] (1) Grind the substrate material and clean it with anhydrous ethanol, then dry it for later use;

[0014] (2) Fe, Cr, Co, Ni, Mo and Ti and C in a molar ratio of 1:1:1:1:0.1-0.4 were weighed in sequence, with TiC accounting for 7-12% of the mass in the first coating. The mixture was ball-milled under vacuum to obtain mixed powder 1.

[0015] (3) The mixed powder 1 is pre-placed on the surface of the substrate material, dried, and then placed in argon gas for laser cladding to form the first coating. The laser cladding processing parameters are: laser power of 1-1.8kW, scanning speed of 5-10mm / s, spot diameter of 2-4mm, and argon gas flow rate of 10-15L / min.

[0016] (4) Fe, Cr, Co, Ni, Mo, Ti and C with a molar ratio of 1:1:1:1:0.1-0.3 were weighed in sequence, and Mo-coated SiC was weighed in sequence. The mass percentage of TiC in the second coating was 3-5%, and the mass percentage of Mo-coated SiC in the second coating was 1-3%. The mixture was ball-milled under vacuum to obtain mixed powder 2.

[0017] (5) The mixed powder 2 is pre-placed on the surface of the first coating, dried, and then placed in argon gas for laser cladding and ultrasonic treatment to form the second coating. The processing parameters for laser cladding are: laser power of 1.5-2.5kW, scanning speed of 8-13mm / s, spot diameter of 2-4mm, and argon flow rate of 10-15L / min.

[0018] Furthermore, in steps (2) and (4), the particle size range of Fe, Cr, Co, Ni, and Mo metal powders is 70-125 μm, the particle size range of Ti powder is 30-80 μm, and the particle size range of C powder is 10-25 μm.

[0019] Furthermore, the ball milling conditions in steps (2) and (4) are as follows: ball milling speed is 30-70 r / min, ball-to-material ratio is 8-12:1, and ball milling time is 3-6 h.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. It has excellent hardness, wear resistance and corrosion resistance; 2. The TiC and Mo elements in the first coating improve the density and stability of the passivation film and enhance the corrosion resistance of the coating. The TiC on the top is redistributed uniformly under the action of remelting and ultrasound, which increases the hardness of the first coating and improves the interfacial bonding force of the coating; 3. The uniform distribution of TiC and Mo-coated SiC in the second coating helps to improve the hardness of the coating. At the same time, the Mo-coated SiC particles replace part of the TiC, avoiding galvanic corrosion caused by the potential difference between TiC and the CoCrFeNiMo matrix; 4. The strength gradually increases from the first coating to the second coating, avoiding the problem of easy peeling between coatings. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for preparing the high-entropy alloy coating of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1

[0024] A method for preparing a high-entropy alloy coating by laser cladding includes the following steps:

[0025] (1) Polish the 304 stainless steel with sandpaper, then clean it with anhydrous ethanol and dry it for later use.

[0026] (2) Fe, Cr, Co, Ni, Mo, Ti, and C powders were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 30 r / min, the ball-to-powder ratio was 12:1, and the ball milling time was 6 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.1, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 7% of the total mass of mixed powder 1, thus obtaining mixed powder 1.

[0027] (3) The mixed powder 1 is pre-placed on the surface of 304 stainless steel and dried at 80℃ for 8h to obtain 304 stainless steel with a powder layer 1 with a thickness of 0.6mm on the surface; the 304 stainless steel with powder layer 1 on the surface is placed in argon gas for laser cladding to form the first coating layer. The laser cladding processing parameters are: laser power of 1kW, scanning speed of 5mm / s, spot diameter of 2mm, and argon gas flow rate of 10L / min.

[0028] (4) Fe, Cr, Co, Ni, Mo, Ti, C, and Mo-coated SiC powder prepared in Example 1 were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 30 r / min, the ball-to-material ratio was 12:1, and the ball milling time was 6 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.1, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 3% of the total mass of mixed powder 2, and the mass of Mo-coated SiC accounted for 1% of the total mass of mixed powder 2, thus obtaining mixed powder 2.

[0029] (5) The mixed powder 2 is pre-placed on the surface of the first coating layer and then dried at 80°C for 8 hours, so that a powder layer 2 with a thickness of 1.8 mm is loaded on the surface of the first coating layer. Then, it is placed in argon gas for laser cladding and ultrasonic treatment at the same time to form the second coating layer. The processing parameters of laser cladding are: laser power of 1.5 kW, scanning speed of 8 mm / s, spot diameter of 2 mm, and argon gas flow rate of 10 L / min. The parameters of ultrasonic treatment are: working power of 2000 W, working frequency of 20 kHz, and amplitude of 8 μm. The head of the ultrasonic generator is at a 45° angle to the powder layer on the substrate surface and the distance is 10 cm.

[0030] Example 2

[0031] A method for preparing a high-entropy alloy coating by laser cladding includes the following steps:

[0032] (1) Polish the 304 stainless steel with sandpaper, then clean it with anhydrous ethanol and dry it for later use.

[0033] (2) Fe, Cr, Co, Ni, Mo, Ti, and C powders were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 40 r / min, the ball-to-powder ratio was 11:1, and the ball milling time was 5 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.2, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 9% of the total mass of mixed powder 1, thus obtaining mixed powder 1.

[0034] (3) The mixed powder 1 is pre-placed on the surface of 304 stainless steel and dried at 100℃ for 4h to obtain 304 stainless steel with a powder layer 1 with a thickness of 0.8mm on the surface; the 304 stainless steel with powder layer 1 on the surface is placed in argon gas for laser cladding to form the first coating layer. The laser cladding processing parameters are: laser power of 1.2kW, scanning speed of 6mm / s, spot diameter of 2mm, and argon gas flow rate of 12L / min.

[0035] (4) Fe, Cr, Co, Ni, Mo, Ti, C, and Mo-coated SiC powder prepared in Example 1 were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 40 r / min, the ball-to-material ratio was 11:1, and the ball milling time was 5 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.2, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 4% of the total mass of mixed powder 2, and the mass of Mo-coated SiC accounted for 1% of the total mass of mixed powder 2, thus obtaining mixed powder 2.

[0036] (5) The mixed powder 2 is pre-placed on the surface of the first coating layer and then dried at 100°C for 4 hours, so that a powder layer 2 with a thickness of 1.6 mm is loaded on the surface of the first coating layer. Then, it is placed in argon gas for laser cladding and ultrasonic treatment at the same time to form the second coating layer. The processing parameters of laser cladding are: laser power of 1.8 kW, scanning speed of 10 mm / s, spot diameter of 2 mm, and argon gas flow rate of 10 L / min. The parameters of ultrasonic treatment are: working power of 2100 W, working frequency of 25 kHz, and amplitude of 10 μm. The head of the ultrasonic generator is at a 45° angle to the powder layer on the substrate surface and the distance is 10 cm.

[0037] Example 3

[0038] A method for preparing a high-entropy alloy coating by laser cladding includes the following steps:

[0039] (1) Polish the 304 stainless steel with sandpaper, then clean it with anhydrous ethanol and dry it for later use.

[0040] (2) Fe, Cr, Co, Ni, Mo, Ti, and C powders were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 50 r / min, the ball-to-powder ratio was 10:1, and the ball milling time was 4 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.3, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 10% of the total mass of mixed powder 1, thus obtaining mixed powder 1.

[0041] (3) The mixed powder 1 is pre-placed on the surface of 304 stainless steel and dried at 110℃ for 2 hours to obtain 304 stainless steel with a powder layer 1 with a thickness of 0.9 mm on the surface; the 304 stainless steel with powder layer 1 on the surface is placed in argon gas for laser cladding to form the first coating layer. The laser cladding processing parameters are: laser power of 1.4kW, scanning speed of 8mm / s, spot diameter of 2mm, and argon gas flow rate of 15L / min.

[0042] (4) Fe, Cr, Co, Ni, Mo, Ti, C, and Mo-coated SiC powder prepared in Example 1 were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 50 r / min, the ball-to-material ratio was 10:1, and the ball milling time was 4 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.2, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 4% of the total mass of mixed powder 2, and the mass of Mo-coated SiC accounted for 2% of the total mass of mixed powder 2, thus obtaining mixed powder 2.

[0043] (5) The mixed powder 2 is pre-placed on the surface of the first coating layer and then dried at 110°C for 2 hours, so that a powder layer 2 with a thickness of 1.5 mm is loaded on the surface of the first coating layer. Then, it is placed in argon gas for laser cladding and ultrasonic treatment at the same time to form the second coating layer. The processing parameters of laser cladding are: laser power of 2.1 kW, scanning speed of 11 mm / s, spot diameter of 2 mm, and argon gas flow rate of 15 L / min. The parameters of ultrasonic treatment are: working power of 2300 W, working frequency of 30 kHz, and amplitude of 15 μm. The head of the ultrasonic generator is at a 45° angle to the powder layer on the substrate surface and the distance is 10 cm.

[0044] Example 4

[0045] A method for preparing a high-entropy alloy coating by laser cladding includes the following steps:

[0046] (1) Polish the 304 stainless steel with sandpaper, then clean it with anhydrous ethanol and dry it for later use.

[0047] (2) Fe, Cr, Co, Ni, Mo, Ti, and C powders were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 60 r / min, the ball-to-powder ratio was 9:1, and the ball milling time was 3 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.4, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 11% of the total mass of mixed powder 1, thus obtaining mixed powder 1.

[0048] (3) The mixed powder 1 is pre-placed on the surface of 304 stainless steel and dried at 120℃ for 2 hours to obtain 304 stainless steel with a powder layer 1 with a thickness of 1 mm on the surface; the 304 stainless steel with powder layer 1 on the surface is placed in argon gas for laser cladding to form the first coating layer. The laser cladding processing parameters are: laser power of 1.5kW, scanning speed of 10mm / s, spot diameter of 2mm, and argon gas flow rate of 10L / min.

[0049] (4) Fe, Cr, Co, Ni, Mo, Ti, C, and Mo-coated SiC powder prepared in Example 1 were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 60 r / min, the ball-to-material ratio was 9:1, and the ball milling time was 3 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.2, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 4% of the total mass of mixed powder 2, and the mass of Mo-coated SiC accounted for 3% of the total mass of mixed powder 2, thus obtaining mixed powder 2.

[0050] (5) The mixed powder 2 is pre-placed on the surface of the first coating layer and then dried at 110°C for 2 hours, so that a powder layer 2 with a thickness of 1.3 mm is loaded on the surface of the first coating layer. Then, it is placed in argon gas for laser cladding and ultrasonic treatment at the same time to form the second coating layer. The processing parameters of laser cladding are: laser power of 2.3 kW, scanning speed of 11 mm / s, spot diameter of 2 mm, and argon gas flow rate of 12 L / min. The parameters of ultrasonic treatment are: working power of 2400 W, working frequency of 35 kHz, and amplitude of 15 μm. The head of the ultrasonic generator is at a 45° angle to the powder layer on the substrate surface and the distance is 10 cm.

[0051] Example 5

[0052] A method for preparing a high-entropy alloy coating by laser cladding includes the following steps:

[0053] (1) Polish the 304 stainless steel with sandpaper, then clean it with anhydrous ethanol and dry it for later use.

[0054] (2) Fe, Cr, Co, Ni, Mo, Ti, and C powders were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 70 r / min, the ball-to-powder ratio was 8:1, and the ball milling time was 3 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.4, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 12% of the total mass of mixed powder 1, thus obtaining mixed powder 1.

[0055] (3) The mixed powder 1 is pre-placed on the surface of 304 stainless steel and dried at 100℃ for 3h to obtain 304 stainless steel with a powder layer 1 with a thickness of 1.2mm on the surface; the 304 stainless steel with powder layer 1 on the surface is placed in argon gas for laser cladding to form the first coating layer. The laser cladding processing parameters are: laser power of 1.8kW, scanning speed of 10mm / s, spot diameter of 2mm, and argon flow rate of 15L / min.

[0056] (4) Fe, Cr, Co, Ni, Mo, Ti, C, and Mo-coated SiC powder prepared in Example 1 were weighed in sequence according to the proportion and ball-milled under vacuum conditions. The ball milling speed was 70 r / min, the ball-to-material ratio was 8:1, and the ball milling time was 3 h. The molar ratio of Fe, Cr, Co, Ni, and Mo metal powders was 1:1:1:1:0.3, and the molar ratio of Ti and C was 1:1. The total mass of Ti and C accounted for 5% of the total mass of mixed powder 2, and the mass of Mo-coated SiC accounted for 3% of the total mass of mixed powder 2, thus obtaining mixed powder 2.

[0057] (5) The mixed powder 2 is pre-placed on the surface of the first coating layer and then dried at 100°C for 3 hours, so that a powder layer 2 with a thickness of 1.8 mm is loaded on the surface of the first coating layer. Then, it is placed in argon gas for laser cladding and ultrasonic treatment at the same time to form the second coating layer. The processing parameters of laser cladding are: laser power of 2.5 kW, scanning speed of 13 mm / s, spot diameter of 2 mm, and argon gas flow rate of 15 L / min. The parameters of ultrasonic treatment are: working power of 2500 W, working frequency of 40 kHz, and amplitude of 17 μm. The head of the ultrasonic generator is at a 45° angle to the powder layer on the substrate surface and the distance is 10 cm.

[0058] Comparative Example 1

[0059] Compared with Example 3, the surface of the 304 stainless steel in Comparative Example 1 only contains a first coating with a thickness of 2.4 mm, and the other steps and raw materials are the same as in Example 3.

[0060] Comparative Example 2

[0061] Compared with Example 3, the surface of the 304 stainless steel in Comparative Example 2 only contains a second coating with a thickness of 2.4 mm. Other steps and raw materials are the same as in Example 3.

[0062] Comparative Example 3

[0063] Compared with Example 3, the first and second coatings in Comparative Example 3 do not contain Mo, while other steps and raw materials are the same as in Example 3.

[0064] Comparative Example 4

[0065] Compared with Example 3, the first and second coatings in Comparative Example 4 do not contain TiC, while the other steps and raw materials are the same as in Example 3.

[0066] Comparative Example 5

[0067] Compared with Example 3, the second coating in Comparative Example 5 does not contain Mo-coated SiC particles, and the sum of the mass of Ti and C accounts for 6% of the total mass of the mixed powder 2. Other steps and raw materials are the same as in Example 3.

[0068] The purity of the powders used in the above embodiments and comparative examples is greater than or equal to 99.9%, wherein the particle size range of Fe, Cr, Co, Ni, and Mo metal powders is 70-125 μm, the particle size range of Ti powder is 30-80 μm, and the particle size range of C powder is 10-25 μm.

[0069] Mo-coated SiC was prepared by uniformly mixing SiC particles and Mo powder at a mass ratio of 6.3:1 and sintering them in a spark plasma sintering furnace. The resulting Mo-coated SiC particles had an average particle size of 1138 nm, while the average particle size of the SiC particles was 559 nm.

[0070] The coatings prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Table 1.

[0071] Table 1. Performance test results of coatings prepared in each embodiment and comparative example.

[0072] Serial Number Hardness value (HV) Corrosion potential (mV) <![CDATA[Corrosion current density (A·cm -2 )]]> Example 1 863.3 -297.5 3.45×10-8 Example 2 887.1 -278.1 2.16×10-8 Example 3 901.9 -271.4 1.17×10-8 Example 4 852.7 -289.8 3.13×10-8 Example 5 890.1 -283.2 2.73×10-8 Comparative Example 1 743.6 -239.4 8.35×10-9 Comparative Example 2 947.5 -324.6 5.77×10-8 Comparative Example 3 844.2 -356.5 7.69×10-8 Comparative Example 4 597.8 -312.8 4.21×10-8 Comparative Example 5 822.7 -339.2 6.42×10-8 304 stainless steel 275.5 -566.7 6.21×10-7

[0073] The hardness of the samples was tested using an HDX-1000 Vickers microhardness tester. For corrosion resistance analysis, a 3.5 wt% NaCl solution was used, and the scan rate was 1 mV / s.

[0074] As can be seen from the test results in Table 1, the coating prepared in Example 3 has high hardness and excellent corrosion resistance. Comparing Example 3 with Comparative Examples 1-2, the substrate surface of Comparative Example 1 only has the first coating, and the hardness of the coating of the same thickness is significantly reduced, while the corrosion resistance is slightly decreased. The substrate surface of Comparative Example 2 only has the second coating, and the hardness of the coating of the same thickness is slightly increased, while the corrosion resistance is worse. This indicates that a single coating cannot simultaneously possess high hardness and corrosion resistance. The synergistic effect of the first coating with good corrosion resistance and the second coating with high strength improves the overall performance of the coating.

[0075] Compared with Example 3, the corrosion resistance of Example 3, which lacks Mo, is worse, indicating that the addition of Mo increases the density of the passivation film, thereby significantly improving the corrosion resistance of the coating.

[0076] Compared with Comparative Example 3 and Comparative Example 4, Comparative Example 4, lacking TiC, exhibited decreased hardness and corrosion resistance. In the first coating, the content of TiC increased sequentially from bottom to top, reducing the potential difference between TiC and the CoCrFeNiMo matrix near the substrate material and preventing galvanic corrosion. Simultaneously, the in-situ generated TiC particles were less prone to agglomeration and had more uniform dispersion, refining the grain size within the matrix and providing more diffusion channels. This facilitated the rapid aggregation of passivation elements to form a denser passivation film. Mo elements enhanced the density of the passivation film and improved the corrosion resistance of the coating. Furthermore, the sequential increase of TiC particles from bottom to top refined the grain size, increased the number of grain boundaries, prevented dislocation slip, and gradually enhanced the hardness and strength of the coating. In the second coating, the addition of TiC and Mo-coated SiC synergistically acted as reinforcing phases, resulting in uniform distribution and increased coating hardness.

[0077] Comparing the data of Example 3 and Comparative Example 5, it can be seen that the corrosion resistance of the SiC coating without adding Mo decreases. This is because adding Mo to coat SiC partially replaces TiC, which avoids the increase of TiC particles causing more potential difference between TiC and the CoCrFeNiMo matrix, thus preventing galvanic corrosion. The coating of Mo can prevent SiC from decomposing during the laser cladding process and combining with Cr to form Cr7C3, which reduces the corrosion resistance of the coating, and further improves the corrosion resistance of the second coating.

Claims

1. A laser cladded high entropy alloy coating, characterized in that, The molar ratio of the metal powders of Fe, Cr, Co, Ni and Mo in the coating is 1:1:1:1:0.1-0.4, and the coating is divided into two layers; the first coating close to the base material further comprises an in-situ generated TiC ceramic phase, and the content of the TiC ceramic phase increases from the bottom to the top; the second coating further comprises Mo-coated SiC and an in-situ generated TiC ceramic phase, both of which are uniformly distributed in the second coating; the first coating is prepared by weighing Fe, Cr, Co, Ni and Mo in a molar ratio of 1:1:1:1:0.1-0.4 and Ti and C in a molar ratio of 1:1, wherein the mass ratio of TiC in the first coating is 7-12%, and the mixed powder 1 is obtained by ball milling under vacuum; the mixed powder 1 is pre-positioned on the surface of the base material, dried, and then subjected to laser cladding in an argon atmosphere to form the first coating; the mixed powder 2 is obtained by ball milling under vacuum by weighing Fe, Cr, Co, Ni, Mo, Ti and C in a molar ratio of 1:1:1:1:0.1-0.3 and Mo-coated SiC, wherein the mass ratio of TiC in the second coating is 3-5%, and the mass ratio of Mo-coated SiC in the second coating is 1-3%; the mixed powder 2 is pre-positioned on the surface of the first coating, dried, and then subjected to laser cladding in an argon atmosphere and ultrasonic treatment to form the second coating.

2. The laser cladded high-entropy alloy coating of claim 1, wherein, The thickness of the first coating is 0.6-1.2 mm.

3. The laser cladded high-entropy alloy coating of claim 1, wherein, The thickness of the second coating is 1.2-1.8 mm.

4. A method of producing the laser cladding high-entropy alloy coating according to claim 1, characterized in that, The method comprises the following steps: (1) polishing the base material and cleaning it with anhydrous ethanol, and drying it for standby use; (2) weighing Fe, Cr, Co, Ni and Mo in a molar ratio of 1:1:1:1:0.1-0.4 and Ti and C in a molar ratio of 1:1, wherein the mass ratio of TiC in the first coating is 7-12%, and the mixed powder 1 is obtained by ball milling under vacuum; (3) pre-positioning the mixed powder 1 on the surface of the base material, drying it, and then subjecting it to laser cladding in an argon atmosphere to form the first coating, and the processing parameters of the laser cladding are as follows: the laser power is 1-1.8 kW, the scanning speed is 5-10 mm / s, the spot diameter is 2-4 mm, and the argon flow rate is 10-15 L / min; (4) weighing Fe, Cr, Co, Ni and Mo in a molar ratio of 1:1:1:1:0.1-0.3, Ti and C in a molar ratio of 1:1, and Mo-coated SiC, wherein the mass ratio of TiC in the second coating is 3-5%, and the mass ratio of Mo-coated SiC in the second coating is 1-3%, and the mixed powder 2 is obtained by ball milling under vacuum; (5) pre-positioning the mixed powder 2 on the surface of the first coating, drying it, and then subjecting it to laser cladding in an argon atmosphere and ultrasonic treatment to form the second coating, and the processing parameters of the laser cladding are as follows: the laser power is 1.5-2.5 kW, the scanning speed is 8-13 mm / s, the spot diameter is 2-4 mm, and the argon flow rate is 10-15 L / min.

5. The method of claim 4, wherein the high-entropy alloy coating is prepared by laser cladding. The particle size of the Fe, Cr, Co, Ni, Mo metal powder in the steps (2) and (4) is 70-125 μm, the particle size of the Ti powder is 30-80 μm, and the particle size of the C powder is 10-25 μm.

6. The method of claim 4, wherein the laser cladding high-entropy alloy coating is prepared by a process comprising: The ball milling speed in the steps (2) and (4) is 30-70 r / min, the ball-to-material ratio is 8-12:1, and the ball milling time is 3-6 h.

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