A medium-entropy alloy laser metal deposition layer and preparation method

Abstract

The present invention provides a medium-entropy alloy laser metal deposition layer and a preparation method. In the present invention, a medium-entropy alloy powder is prepared by mixing Fe, Co, Ni, Cr, and B elements in a certain proportion, and a medium-entropy alloy laser metal deposition layer is prepared on a metal substrate by laser metal deposition. The deposition layer forms a good metallurgical bond with the metal surface, is smooth and dense, and has no metal residue coverage, cracks, or fissures on the surface. At the same time, the dendrite size in its microstructure shows a gradient distribution, and it has high hardness, strong wear resistance, and low component segregation. It is suitable for the repair and remanufacturing of various metal substrates such as high-temperature alloys, structural steels, and titanium alloys, as well as the surface protection of key components of marine engineering equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of medium-entropy alloy manufacturing, and relates to a medium-entropy alloy laser metal deposition layer and a preparation method thereof. Background Art

[0002] Under the erosion and corrosion of seawater, marine engineering equipment is prone to wear and corrosion due to complex mechanical, chemical and electrochemical effects, which causes huge economic losses to social production and becomes one of the bottlenecks restricting the development of marine engineering technology.

[0003] In order to solve the problem of easy corrosion of marine engineering equipment, it is necessary to construct a functional high-strength protective layer on the surface of marine engineering equipment. As an advanced laser manufacturing technology, laser metal deposition technology uses high-energy laser as a heat source and alloy powder as a deposition material. Through laser irradiation and action on the surface of the workpiece, the deposition material is quickly melted to form a liquid molten pool, and then quickly solidified to form a dense, uniform and thickness-controlled metallurgical deposition layer. The laser metal deposition layer can form a metallurgical bond with the matrix. The matrix material has a low dilution degree and a small heat input. It has special physical, chemical and mechanical properties that can be modulated, thereby achieving the effect of repairing the damaged workpiece surface and strengthening and extending the service life of the workpiece. It greatly improves the corrosion resistance and wear resistance of metal materials in the marine environment, extends the service life of marine engineering equipment, and has a very broad application and development prospect.

[0004] During the laser metal deposition process, a high-energy laser beam interacts with metal powder to form a liquid molten pool. As the laser beam moves away from the molten pool, the molten pool immediately cools, solidifies, and shrinks. Constrained by the surrounding materials, the laser metal deposition layer experiences thermal stress during the deposition process. The solidification order of laser metal deposition layers varies, resulting in large temperature gradients between the deposited material and the substrate, as well as within the deposited material. This results in a very complex thermal stress state within the laser metal deposition layer. When the thermal stress exceeds the yield strength of the material, the laser metal deposition layer will crack. This cracking phenomenon is particularly evident in high-strength deposition layers. The appearance of cracks will greatly affect the service life of the deposition layer, leading to the failure of the deposition layer to form. The problem of deposition layer cracking has seriously restricted the further promotion of this technology in industrial production, becoming a technical bottleneck that restricts the rapid development of this technology and greatly limits its application and popularization. Summary of the Invention

[0005] The purpose of the present invention is to provide a medium entropy alloy laser metal deposition layer and a preparation method thereof, so as to solve the problem that the existing laser metal deposition layer is prone to cracking.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The design concept of this invention is based on the extremely rapid solidification rate and variable solidification sequence of medium-entropy alloy materials during laser metal deposition. This allows the production of a crack-free, highly wear-resistant, and corrosion-resistant medium-entropy alloy deposit with a gradient microstructural dimensional variation. This method utilizes a medium-entropy alloy powder composed of Fe, Co, Ni, Cr, and B in specific proportions. This protective layer is then deposited on a metal substrate via laser metal deposition, improving the material's surface wear resistance and corrosion resistance, demonstrating broad industrial application prospects.

[0008] Specifically, the present invention provides a medium entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.05-0.25:0.02-0.25. Preferably, the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.2:0.2.

[0009] In this application, the raw materials for preparing the medium-entropy alloy laser metal deposition layer include the metal elements Fe, Co, Cr, and Ni, and the non-metallic element B. Because the atomic radius of B is much smaller than that of metal elements, when the atomic radius of the elements in the alloy powder varies greatly, the originally relatively neatly arranged crystal structure in the alloy will be distorted due to atomic squeezing or collapse, and the diffusion of atoms will be hindered, resulting in grain refinement and solid solution strengthening.

[0010] The magnitude of lattice distortion in medium-entropy alloys is usually quantitatively described by the average atomic size difference δ, as shown in the following formula:

[0011]

[0012] Where: is the atomic percentage of the i-th element; is the atomic radius of the ith element; is the average atomic radius.

[0013] As the above formula shows, the closer the atomic radii of the elements in the alloy, the smaller the δ value and the smaller the lattice distortion. Therefore, when a certain amount of element B is added to the alloy powder, an interstitial solid solution is formed, which enhances the solid solution strengthening effect and thus improves the strength of the medium-entropy alloy.

[0014] Because laser metal deposition (LMD) involves nonequilibrium solidification and rapid solidification, excess boron (B) readily reacts with other elements in the alloy powder to form borides. These borides, a ceramic phase with low toughness, are prone to cracking during LMD, leading to cladding failure. Therefore, the boron content in the alloy powder should be kept within a molar ratio of 0.02-0.25 to achieve high-quality, crack-free LMD layers.

[0015] In the raw materials for preparing the medium-entropy alloy laser metal deposition layer in the present application, the purity of each powder is higher than 99.9% and the particle size is 100-400 mesh.

[0016] In addition, the present invention also provides a method for preparing a medium-entropy alloy laser metal deposition layer, the method comprising:

[0017] S01: Fe, Co, Ni, Cr and B elemental powders are mixed to form medium entropy alloy powder.

[0018] In the present application, any mechanical method can be used to uniformly mix the Fe, Co, Ni, Cr and B elemental powders. More preferably, in the present application, the Fe, Co, Ni, Cr and B elemental powders are mixed under vacuum using a high-energy ball milling method. The ball milling jar used for high-energy ball milling is a vacuum stainless steel jar, and the balls used are stainless steel. The ball milling speed during ball milling by the high-energy ball milling method is 100-150 rpm, the ball-to-material ratio is 2:1-4:1, and the ball milling time is 4-6h. More preferably, the ball milling speed during ball milling by the high-energy ball milling method is 110 rpm, the ball-to-material ratio is 3:1, and the ball milling time is 5h.

[0019] After the Fe, Co, Ni, Cr and B elemental powders are uniformly mixed, they are dried at a drying temperature of 120-150° C. for 2-6 hours to obtain medium entropy alloy powders of different particle sizes.

[0020] S02: After mixing the medium entropy alloy powder with anhydrous ethanol, the mixture is evenly applied on the surface of the metal substrate and dried.

[0021] When mixed with anhydrous ethanol, the medium-entropy alloy powder forms a paste or viscous liquid. The liquid powder is evenly applied to the surface of a metal substrate to form a prefabricated layer with a thickness of 0.7-1.2 mm. The metal substrate with the prefabricated layer is dried at a temperature of 110-130°C for 1-3 hours. Preferably, the liquid powder is applied to a thickness of 1.2 mm on the metal substrate, the drying temperature is 120°C, and the drying time is 2 hours.

[0022] S03: performing laser deposition on the dried metal substrate to form a medium entropy alloy laser metal deposition layer on the surface of the metal substrate.

[0023] The dried metal substrate is subjected to laser deposition using a fiber laser with a laser power of 1.2-2 kW, a scanning speed of 2-5 mm / s, and a laser spot diameter of 2-5 mm to form a medium-entropy alloy laser metal deposition layer on the metal substrate surface. Preferably, the laser deposition laser power is 1.4-1.6 kW and the scanning speed is 3-4 mm / s.

[0024] The present invention has the following beneficial effects:

[0025] 1) In the present invention, the prepared medium-entropy alloy laser metal deposition layer forms a good metallurgical bond with the metal surface, the deposition layer is smooth and dense, and the surface is not covered with metal residues, cracks, or fissures.

[0026] 2) In the present invention, the dendrite size in the microstructure of the prepared medium-entropy alloy laser metal deposition layer presents a gradient distribution.

[0027] 3) In the present invention, the prepared medium-entropy alloy laser metal deposition layer has high hardness, strong wear resistance and small composition segregation.

[0028] 4) In the present invention, the prepared medium-entropy alloy laser metal deposition layer has a low dilution rate and a controllable thickness of up to several millimeters.

[0029] 5) The preparation method provided by the present invention is simple to operate, has high processing efficiency, and low production cost. It can be applied to the repair and remanufacturing of the surfaces of various metal substrates such as high-temperature alloys, structural steels, and titanium alloys. It can also be used for the surface protection of key components of marine engineering equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the macroscopic appearance of the medium entropy alloy laser metal deposition layer deposited on the metal surface;

[0031] Figure 2 This is the SEM (Scanning Electron Microscope) image of the medium-entropy alloy laser metal deposition layer;

[0032] Figure 3 This is the microhardness diagram of the medium entropy alloy laser metal deposition layer. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0034] Example 1

[0035] An embodiment of the present application provides a medium-entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.2:0.2, the particle size of each powder is 300 mesh, and the purity is higher than 99.9%.

[0036] The method for preparing a medium-entropy alloy laser metal deposition layer provided in the embodiment of the present application includes:

[0037] S101: The Fe, Co, Ni, Cr and B elemental powders in the above proportions are mixed by high-energy ball milling under vacuum, wherein the ball milling jar is a vacuum stainless steel jar, the balls used are stainless steel, the ball milling speed is 110 rpm, the ball-to-material ratio is 3:1, and the ball milling time is 5 hours. After the Fe, Co, Ni, Cr and B elemental powders are mixed evenly, they are dried at a drying temperature of 120°C for 2 hours to obtain the medium entropy alloy powder FeCoNiCr 0.2 B 0.2 .

[0038] S102: Medium entropy alloy powder FeCoNiCr 0.2 B 0.2 When mixed with anhydrous ethanol, it forms a paste or viscous powder liquid. Apply the powder liquid evenly to the surface of the 42CrMo steel substrate to form a prefabricated layer with a thickness of 1.2mm. Dry the 42CrMo steel substrate with the prefabricated layer at 120°C for 2 hours.

[0039] S103: The dried 42CrMo steel substrate is subjected to laser deposition using a fiber laser with a laser power of 1.2 kW, a scanning speed of 3 mm / s, and a laser spot diameter of 3 mm to form FeCoNiCr on the surface of the 42CrMo steel substrate. 0.2 B 0.2 Medium-entropy alloy deposition layer.

[0040] Example 2

[0041] An embodiment of the present application provides a medium-entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.05:0.02, the particle size of each powder is 100 mesh, and the purity is higher than 99.9%.

[0042] The method for preparing a medium-entropy alloy laser metal deposition layer provided in the embodiment of the present application includes:

[0043] S201: The Fe, Co, Ni, Cr and B elemental powders in the above proportions are mixed by high-energy ball milling under vacuum, wherein the ball milling jar is a vacuum stainless steel jar, the balls used are stainless steel, the ball milling speed is 100 rpm, the ball-to-material ratio is 2:1, and the ball milling time is 6 hours. After the Fe, Co, Ni, Cr and B elemental powders are mixed evenly, they are dried at a drying temperature of 150°C for 2 hours to obtain the medium entropy alloy powder FeCoNiCr 0.05 B 0.02 .

[0044] S202: Medium entropy alloy powder FeCoNiCr 0.05 B 0.02 When mixed with anhydrous ethanol, it forms a paste or viscous powder liquid. Apply the powder liquid evenly to the surface of the stainless steel substrate to form a prefabricated layer with a thickness of 0.7 mm. Dry the stainless steel substrate with the prefabricated layer at 110°C for 3 hours.

[0045] S203: The dried stainless steel substrate is subjected to laser deposition using a fiber laser with a laser power of 2 kW, a scanning speed of 2 mm / s, and a laser spot diameter of 2 mm to form FeCoNiCr on the surface of the stainless steel substrate. 0.05 B 0.02 Medium-entropy alloy deposition layer.

[0046] Example 3

[0047] An embodiment of the present application provides a medium-entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1: 0.25: 0.25, the particle size of each powder is 400 mesh, and the purity is higher than 99.9%.

[0048] The method for preparing a medium-entropy alloy laser metal deposition layer provided in the embodiment of the present application includes:

[0049] S301: The Fe, Co, Ni, Cr and B elemental powders in the above proportions are mixed by high-energy ball milling under vacuum, wherein the ball milling jar is a vacuum stainless steel jar, the balls used are stainless steel, the ball milling speed is 150 rpm, the ball-to-material ratio is 4:1, and the ball milling time is 4 hours. After the Fe, Co, Ni, Cr and B elemental powders are mixed evenly, they are dried at a drying temperature of 130°C for 6 hours to obtain the medium entropy alloy powder FeCoNiCr 0.25 B 0.25 .

[0050] S302: Medium entropy alloy powder FeCoNiCr 0.25 B 0.25When mixed with anhydrous ethanol, it forms a paste or viscous powder. Apply the powder evenly to the surface of the stainless steel substrate to form a prefabricated layer with a thickness of 1.2 mm. Dry the stainless steel substrate with the prefabricated layer at 130°C for 1 hour.

[0051] S303: The dried stainless steel substrate is subjected to laser deposition using a fiber laser with a laser power of 1.4 kW, a scanning speed of 5 mm / s, and a laser spot diameter of 5 mm to form FeCoNiCr on the surface of the stainless steel substrate. 0.25 B 0.25 Medium-entropy alloy deposition layer.

[0052] Example 4

[0053] An embodiment of the present application provides a medium-entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B with a molar ratio of 1:1:1:0.1:0.2, the particle size of each powder is 300 mesh, and the purity is higher than 99.9%.

[0054] The method for preparing a medium-entropy alloy laser metal deposition layer provided in the embodiment of the present application includes:

[0055] S401: The Fe, Co, Ni, Cr and B elemental powders in the above proportions are mixed by high-energy ball milling under vacuum, wherein the ball milling jar is a vacuum stainless steel jar, the balls used are stainless steel, the ball milling speed is 120 rpm, the ball-to-material ratio is 3:1, and the ball milling time is 5 hours. After the Fe, Co, Ni, Cr and B elemental powders are mixed evenly, they are dried at a drying temperature of 130°C for 4 hours to obtain the medium entropy alloy powder FeCoNiCr 0.1 B 0.2 .

[0056] S402: Medium entropy alloy powder FeCoNiCr 0.1 B 0.2 When mixed with anhydrous ethanol, it forms a paste or viscous powder liquid. Apply the powder liquid evenly to the surface of the 42CrMo steel substrate to form a prefabricated layer with a thickness of 1.0 mm. Dry the 42CrMo steel substrate with the prefabricated layer at 115°C for 2.5 hours.

[0057] S403: The dried 42CrMo steel substrate is subjected to laser deposition using a fiber laser with a laser power of 1.6Kw, a scanning speed of 4mm / s, and a laser spot diameter of 3mm to form FeCoNiCr on the surface of the 42CrMo steel substrate. 0.1 B 0.2 Medium-entropy alloy deposition layer.

[0058] Example 5

[0059] An embodiment of the present application provides a medium-entropy alloy laser metal deposition layer, wherein the raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.15:0.2, the particle size of each powder is 200 mesh, and the purity is higher than 99.9%.

[0060] The method for preparing a medium-entropy alloy laser metal deposition layer provided in the embodiment of the present application includes:

[0061] S501: The Fe, Co, Ni, Cr and B elemental powders in the above proportions are mixed by high-energy ball milling under vacuum, wherein the ball milling jar is a vacuum stainless steel jar, the balls used are stainless steel, the ball milling speed is 130 rpm, the ball-to-material ratio is 3:1, and the ball milling time is 3 hours. After the Fe, Co, Ni, Cr and B elemental powders are mixed evenly, they are dried at a drying temperature of 140°C for 3 hours to obtain the medium entropy alloy powder FeCoNiCr 0.15 B 0.2 .

[0062] S502: Medium entropy alloy powder FeCoNiCr 0.15 B 0.2 When mixed with anhydrous ethanol, it forms a paste or viscous powder liquid. Apply the powder liquid evenly to the surface of the 42CrMo steel substrate to form a prefabricated layer with a thickness of 0.9mm. Dry the 42CrMo steel substrate with the prefabricated layer at 120°C for 2 hours.

[0063] S503: The dried 42CrMo steel substrate is subjected to laser deposition using a fiber laser with a laser power of 1.8Kw, a scanning speed of 4mm / s, and a laser spot diameter of 4mm to form FeCoNiCr on the surface of the 42CrMo steel substrate. 0.15 B 0.2 Medium-entropy alloy deposition layer.

[0064] In order to verify that the medium entropy alloy laser metal deposition layer prepared in the embodiment of the present application has no cracks, the FeCoNiCr prepared in Example 1 is used in the present application. 0.2 B 0.2 The macroscopic appearance of the medium entropy alloy deposited layer was tested to obtain the attached Figure 1 . Figure 1 It can be seen that the medium-entropy alloy laser metal deposition layer prepared in Example 1 of the present application forms a good metallurgical bond with the metal surface without cracks or fissures.

[0065] In order to verify the microstructure of the medium entropy alloy laser metal deposition layer prepared in the embodiment of the present application, the FeCoNiCr prepared in Example 1 was used. 0.2 B 0.2 The medium entropy alloy deposited layer was tested by SEM and the attached Figure 2 The SEM picture shown in the attached Figure 2 It can be seen that the dendrite size in the microstructure of the medium-entropy alloy laser metal deposition layer prepared in Example 1 of the present application presents a gradient distribution.

[0066] In order to test the microhardness of the medium entropy alloy laser metal deposition layer prepared in the embodiment of the present application, the FeCoNiCr prepared in Example 1 was used. 0.2 B 0.2 The microhardness of the medium entropy alloy deposited layer was tested. Figure 3 . Figure 3 It can be seen that the medium-entropy alloy laser metal deposition layer prepared in Example 1 of the present application has a high microhardness, and the microhardness decreases with increasing distance from the deposition layer surface. The microhardness of the medium-entropy alloy laser metal deposition layer prepared in Example 1 of the present application can reach above 900 HV.

[0067] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A medium entropy alloy laser metal deposition layer, characterized in that: The raw materials for preparing the deposited layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.05-0.25:0.02-0.25, wherein Fe, Co, Ni, Cr and B are all single-substance powders, the microstructure size of the deposited layer changes gradiently, and the microhardness of the deposited layer is above 900HV.

2. The medium entropy alloy laser metal deposition layer according to claim 1, characterized in that The raw materials for preparing the deposition layer include Fe, Co, Ni, Cr and B in a molar ratio of 1:1:1:0.2:0.

2.

3. The medium entropy alloy laser metal deposition layer according to claim 1, characterized in that: The purity of each powder in the raw materials for preparing the deposition layer is higher than 99.9%, and the particle size is 100-400 meshes.

4. The method for preparing a medium entropy alloy laser metal deposition layer according to claim 1, characterized in that: include: Mixing Fe, Co, Ni, Cr and B elemental powders to form a medium entropy alloy powder; The medium entropy alloy powder is mixed with anhydrous ethanol, and then evenly applied on the surface of the metal substrate and dried; The dried metal substrate is subjected to laser deposition to form a medium entropy alloy laser metal deposition layer on the surface of the metal substrate.

5. The preparation method according to claim 4, characterized in that Fe, Co, Ni, Cr and B elemental powders are mixed by high-energy ball milling under vacuum and dried to obtain medium-entropy alloy powders.

6. The preparation method according to claim 5, characterized in that The ball mill speed is 100-150 rpm, the ball-to-material ratio is 2:1-4:1, and the ball milling time is 4-6 h.

7. The preparation method according to claim 5, characterized in that The drying temperature is 120-150°C and the drying time is 2-6 hours.

8. The preparation method according to claim 4, characterized in that The coating thickness of the medium entropy alloy powder on the surface of the metal substrate is 0.7-1.2 mm.

9. The preparation method according to claim 4, characterized in that The surface drying temperature of the metal substrate is 110-130° C., and the drying time is 1-3 hours.

10. The preparation method according to claim 4, characterized in that The laser power of laser deposition is 1.2-2kW, the scanning speed is 2-5mm / s, and the laser spot diameter is 2-5mm.

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