Laser-cladding toughened composite coating added with toughness net and preparation method of laser-cladding toughened composite coating

Abstract

The invention belongs to the technical field of preparation of metal surface coating materials, and relates to a preparation method of a laser cladding added tough net composite coating. The method comprises the following steps: derusting and polishing the surface of a steel material, cleaning and drying. Adding WC powder into the Fe5 alloy powder, uniformly mixing, and carrying out ball milling to obtain mixed powder; the tough mesh is laid on the surface of standby steel and then combined with the prefabricated powder, drying is conducted, and the composite tough mesh is obtained; and under the protection of argon, the composite tough net is subjected to laser cladding to the surface of the standby steel, and the toughened composite coating is formed. The surface quality of a cladding layer is obviously improved by adding the tough net, cracks are obviously inhibited, and good metallurgical bonding is formed between the tough net and a base material.

Description

Technical Field

[0001] This invention belongs to the field of metal surface coating material preparation technology, and relates to a method for preparing a laser cladding composite coating with added toughness mesh. Background Technology

[0002] Laser cladding technology is an economical and efficient surface modification technology belonging to the fields of advanced and green manufacturing. It can form high-performance protective coatings on the surface of parts, reducing the use of precious metal materials, lowering production costs, and increasing the service life of parts. Ceramic-reinforced metal-matrix composite coatings combine the high ductility and strength of metal materials with the high melting point and high wear resistance of ceramic materials. Using laser cladding technology to prepare metal-ceramic composite coatings is an important way to improve the wear resistance of metal substrate surfaces. However, the added hard ceramic phase particles and the metal matrix are two substances with different bonding properties. Especially when a large amount of ceramic phase is added to improve the coating's hardness and wear resistance, the difference in thermophysical properties such as the coefficient of thermal expansion can lead to high brittleness and a greater tendency to crack in the ceramic / metal composite coating, seriously affecting the quality and service life of the cladding layer. Furthermore, high-energy laser beam processing has the characteristics of rapid melting and solidification, resulting in large residual stresses within the coating. When the internal stress exceeds the material's resistance to deformation, cracks will form in the cladding layer. Large, penetrating cracks directly lead to a decrease in the mechanical properties of the part or even failure. Therefore, effectively suppressing cracking of laser cladding coatings is key to the widespread industrial application of high-hardness ceramic / metal matrix composite coatings. Summary of the Invention

[0003] This invention addresses the problems of high brittleness and a large tendency to crack in traditional ceramic / metal matrix composite coatings by proposing a novel laser cladding toughening composite coating with added toughening mesh and its preparation method.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution: A cladding process for adding a tough mesh composite coating, comprising the following steps: (1) Remove rust and polish the surface of the steel material, then clean it with ethanol and dry it to obtain the steel material for use.

[0005] (2) Add WC powder to Fe5 alloy powder, mix evenly, then dry and ball mill to obtain mixed powder.

[0006] (3) Add polyvinyl alcohol solution to the mixed powder and mix evenly to obtain a pre-made wet powder; after laying the tough mesh on the surface of the spare steel, combine it with the pre-made powder and dry it to obtain a composite tough mesh; under argon protection, laser cladding the composite tough mesh onto the surface of the spare steel to form a toughened composite coating; the laser cladding process parameters are: laser power 1450-1650W, scanning speed 1-2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 8-12L / min, and defocusing amount 12-15mm.

[0007] Preferably, the thickness of the pre-prepared wet powder in the mixed powder composite toughness mesh in step (3) is 1-1.2 mm.

[0008] Preferably, the composite tough mesh in step (3) is prepared using any of the following methods: The first method involves placing a flat, square-hole tough mesh sheet tightly against a stainless steel substrate on a two-dimensional plane. A 2-4% polyvinyl alcohol solution is mixed with an alloy powder and then spread on the tough mesh to obtain a doped tough mesh P. After drying, a composite tough mesh A is obtained.

[0009] The second method involves diagonally stretching a square-hole tough mesh into a diamond-shaped tough mesh, then placing a layer of polyvinyl alcohol solution (2-4% by mass) mixed with alloy powder on a stainless steel substrate, and finally drying it to obtain composite tough mesh B.

[0010] The third method involves laying a second layer of square-hole toughness mesh on the top layer of the doped toughness mesh P, pressing it down, and then drying it to obtain a composite toughness mesh C.

[0011] Preferably, the square-hole tough mesh is any one of 20 mesh × Φ0.08 W mesh, 40 mesh × Φ0.1 W mesh, 20 mesh × Φ0.12 W mesh, or 40 mesh × Φ0.1 Mo mesh. The mixed powder consists of 65-75 parts by weight of Fe5 alloy powder and 25-35 parts by weight of WC powder. The Fe5 alloy powder contains elements C, Cr, Si, Mn, B, and Fe, wherein the weight fraction of Fe is 50-55%.

[0012] The addition of the toughness mesh to the cladding composite coating effectively hinders the sedimentation of WC powder in the composite coating, making it more evenly distributed in the coating, and increasing the overall average hardness of the composite coating by about 15%.

[0013] The tough mesh in the cladding composite coating acts as a stress relaxation zone, effectively alleviating the residual tensile stress in the composite coating and reducing the initiation and further propagation of cracks in the composite coating. When the coating is subjected to indentation fracture test, the crack can achieve a good crack stop effect when it extends to the tough mesh.

[0014] Furthermore, the addition of a tough mesh to the cladding composite coating significantly improves the tensile fracture brittle fracture spalling phenomenon of the composite coating, thereby enhancing the tensile properties and wear resistance of the composite coating.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The surface quality of the cladding layer with added tough mesh obtained by the preparation method of this invention is significantly improved, cracking is significantly suppressed, and a good metallurgical bond is formed between the tough mesh and the base material. The cladding layer thickness reaches 0.8-1.4 mm, and the main phases are (Fe, Cr) solid solution and WC, Cr3C2, Cr 23 Composed of hard phases such as C6 and Cr7C3, the toughening network in the composite coating acts as a stress relaxation zone, effectively alleviating residual tensile stress in the coating. The toughening network effectively inhibits crack initiation and further propagation. It also improves the overall average hardness of the composite coating by hindering WC powder sedimentation, resulting in a more uniform distribution. The addition of the toughening network significantly improves the brittle fracture and spalling phenomenon during tensile fracture of the composite coating, enhancing its tensile properties and wear resistance. Toughened composite coatings can be prepared on the surface of mechanical parts by laser cladding, which can be used for surface optimization and repair, extending the service life of parts. Laser cladding is highly efficient, clean, pollution-free, and easily automated. Attached Figure Description

[0016] Figure 1 The macroscopic morphology of the laser cladding toughened composite coatings in Examples 1, 2, 4 and Comparative Examples 1-3 is shown.

[0017] Figure 2 The image shows the microstructure of the laser cladding toughened composite coating in Example 1.

[0018] Figure 3 This is a microscopic SEM image of the laser cladding toughened composite coating from Example 2. Figure 4 This is a SEM image of the crack shut-off effect in Example 1.

[0019] Figure 5 The residual stress distribution of the laser cladding toughened composite coatings in Examples 1-4 and Comparative Example 1 is shown.

[0020] Figure 6 The figures in the middle represent the tensile macroscopic morphology of the laser cladding toughened composite coatings of Examples 1-4 and Comparative Example 1, respectively. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0023] The manufacturers, specifications, or product numbers of some materials in the following examples are as follows: 304 stainless steel substrate: Chenxin Stainless Steel Technology.

[0024] Fe5 alloy powder: Zhongye Xindun alloy, the chemical composition is composed of six elements: C, Cr, Si, Mn, B and Fe. The sum of the mass percentages of the five elements C, Cr, Si, Mn and B is 48%, and the balance is Fe.

[0025] WC powder: China Metallurgical Research Institute, purity 99.99%.

[0026] Polyvinyl alcohol: degree of polymerization is 1700.

[0027] Example 1 (1) Use an angle grinder and sandpaper to remove rust and polish the surface of the 304 stainless steel substrate to obtain a bright and flat surface. Clean the surface of the steel substrate with anhydrous ethanol, place it in a 100℃ oven and dry for 60 minutes to remove moisture. Place the pretreated stainless steel substrate in a vacuum bag for later use.

[0028] (2) Using Fe5 alloy powder as the base powder, add WC powder, mix, dry and ball mill to obtain mixed powder, wherein the mass of WC powder added is 30% of the total mass of the mixed powder.

[0029] (3) According to the first preparation method, a 3% polyvinyl alcohol solution is used to pre-place a 40-mesh × Φ0.1 W mesh (Hongyun Metal Products Co., Ltd.) and mixed powder on the surface of the treated steel substrate, and then place it in a 100℃ oven to dry for 50 min. The thickness of the mixed powder on the steel substrate is 1 mm, and the mass ratio of polyvinyl alcohol solution to mixed powder is 1:3.

[0030] (4) Under argon protection, the steel substrate with pre-mixed powder is laser clad to form a toughened composite coating. The laser cladding process parameters are: laser power 1560W, scanning speed 2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 10L / min, and defocusing amount 13.5mm.

[0031] Testing revealed that the cladding layer had a smooth and flat surface, a significantly reduced number of cracks, and good adhesion between the tough mesh and the coating. Figure 1As shown in (a). High-magnification SEM images of the tissue are as follows. Figure 2 As shown. Figure 4 (ac) demonstrates the bridging and blocking effects as cracks propagate to the ductile mesh. After the coating indentation fractured under an artificially applied 50N load, the ductile mesh exhibited good crack-preventing properties, such as... Figure 4 As shown in (d), XRD results show that the cladding layer microstructure is mainly composed of (Fe, Cr) solid solution and WC, Cr3C2, and Cr. 23 C6 and Cr7C3, etc. Figure 5 (0.1w network) refers to the residual stress measured using the Huayun TM3 gradient stress detection and analysis system. Figure 5 As can be seen from the data, the toughened composite coating prepared in this embodiment has the most uniform residual tensile stress distribution and the lowest value. Figure 6 a represents the tensile results according to the national standard GB / T 228.1-2021 (Metallic materials, tensile testing—Part 1: Test at room temperature). In this example, the surface of the 0.1W mesh-toughened tensile specimen coating is relatively smooth, with almost no brittle spalling throughout the tensile area. Under a 60N load applied at room temperature, the composite coating with 0.1W mesh toughening exhibits the lowest average coefficient of friction and the best wear resistance.

[0032] Example 2 (1) Use an angle grinder and sandpaper to remove rust and polish the surface of the 304 stainless steel substrate to obtain a bright and flat surface. Clean the surface of the steel substrate with anhydrous ethanol, place it in a 100℃ oven and dry for 60 minutes to remove moisture. Place the pretreated stainless steel substrate in a vacuum bag for later use.

[0033] (2) Using Fe5 alloy powder as the base powder, add WC powder, mix, dry and ball mill to obtain mixed powder, wherein the mass of WC powder added is 30% of the total mass of the mixed powder.

[0034] (3) According to the first preparation method, a 3% polyvinyl alcohol solution is used to pre-place a 20-mesh × Φ0.08W mesh and mixed powder on the surface of the treated steel substrate, and then dry it. The thickness of the mixed powder on the steel substrate is 1 mm, and the mass ratio of polyvinyl alcohol solution to mixed powder is 1:3.

[0035] (4) Under argon protection, the steel substrate with pre-mixed powder is laser clad to form a toughened composite coating. The laser cladding process parameters are: laser power 1560W, scanning speed 2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 10L / min, and defocusing amount 13.5mm.

[0036] Testing revealed an uneven surface on the cladding layer, but the number of cracks was reduced, and the tough mesh bonded well to the coating. Figure 1 As shown in (b). High-magnification SEM images of the tissue are as follows. Figure 3 As shown. Figure 5 (0.08w) represents the residual stress measured using the Huayun TM3 gradient stress detection and analysis system. Figure 5 As can be seen from the results, the residual tensile stress of the toughened composite coating prepared in this embodiment is significantly reduced. Figure 6 b represents the tensile results according to the national standard GB / T 228.1-2021 (Metallic materials, tensile testing—Part 1: Room temperature test method). The toughened tensile specimen prepared in this embodiment has a relatively smooth coating surface and exhibits good brittle spalling in the tensile region. Under a 60N load applied at room temperature, the toughened composite coating prepared in this embodiment has a low average coefficient of friction.

[0037] Example 3 (1) Use an angle grinder and sandpaper to remove rust and polish the surface of the 304 stainless steel substrate to obtain a bright and flat surface. Clean the surface of the steel substrate with anhydrous ethanol, place it in a 100℃ oven and dry for 60 minutes to remove moisture. Place the pretreated stainless steel substrate in a vacuum bag for later use.

[0038] (2) Using Fe5 alloy powder as the base powder, add WC powder, mix, dry and ball mill to obtain mixed powder, wherein the mass of WC powder added is 30% of the total mass of the mixed powder.

[0039] (3) According to the first preparation method, a 3% polyvinyl alcohol solution is used to pre-place a 20-mesh × Φ0.12W mesh and mixed powder on the surface of the treated steel substrate, and then dry it. The thickness of the mixed powder on the steel substrate is 1 mm, and the mass ratio of polyvinyl alcohol solution to mixed powder is 1:3.

[0040] (4) Under argon protection, the steel substrate with pre-mixed powder is laser clad to form a toughened composite coating. The laser cladding process parameters are: laser power 1560W, scanning speed 2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 10L / min, and defocusing amount 13.5mm.

[0041] Tests showed that the cladding layer surface was relatively smooth, but defects were present. The number of cracks was reduced, and the tough mesh bonded well with the coating. Figure 5 (0.12w network) represents the residual stress measured using the Huayun TM3 gradient stress detection and analysis system. As can be seen from the figure, the toughened composite coating prepared in this embodiment has the maximum residual compressive stress. Figure 6c represents the tensile results according to the national standard GB / T 228.1-2021 (Metallic materials, tensile testing—Part 1: Test at room temperature). As can be seen from the figure, the toughened tensile specimen prepared in this embodiment has a relatively smooth coating surface, and the brittle spalling phenomenon in the tensile region is significantly improved. Under a 60N load applied at room temperature, the toughened composite coating exhibits a relatively high average coefficient of friction.

[0042] Example 4 (1) Use an angle grinder and sandpaper to remove rust and polish the surface of the 304 stainless steel substrate to obtain a bright and flat surface. Clean the surface of the steel substrate with anhydrous ethanol, place it in a 100℃ oven and dry for 60 minutes to remove moisture. Place the pretreated stainless steel substrate in a vacuum bag for later use.

[0043] (2) Using Fe5 alloy powder as the base powder, add WC powder, mix, dry and ball mill to obtain mixed powder, wherein the mass of WC powder added is 30% of the total mass of the mixed powder.

[0044] (3) According to the first preparation method, a 3% polyvinyl alcohol solution is used to pre-place a 40 mesh × Φ0.1Mo mesh and mixed powder on the surface of the treated steel substrate and then dry it. The thickness of the mixed powder on the steel substrate is 1 mm, and the mass ratio of polyvinyl alcohol solution to mixed powder is 1:3.

[0045] (4) Under argon protection, the steel substrate with pre-mixed powder is laser clad to form a toughened composite coating. The laser cladding process parameters are: laser power 1560W, scanning speed 2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 10L / min, and defocusing amount 13.5mm.

[0046] Testing revealed that the cladding layer had a smooth and flat surface, a significantly reduced number of cracks, and good adhesion between the tough mesh and the coating. Figure 1 As shown in (c). High-magnification SEM images of the tissue are as follows. Figure 3 As shown. XRD analysis revealed that the cladding layer microstructure mainly consists of (Fe, Cr) solid solution and WC, Cr3C2, and Cr. 23 C6 and Cr7C3, etc. Figure 5 (0.1Mo grid) shows the residual stress measured using the Huayun TM3 gradient stress detection and analysis system. As can be seen from the figure, the residual tensile stress of the toughened composite coating prepared in this embodiment is significantly reduced. Figure 6d represents the tensile results according to the national standard GB / T 228.1-2021 (Metallic materials, tensile testing—Part 1: Test method at room temperature). In this embodiment, the toughened tensile specimen has a relatively smooth coating surface, with almost no brittle spalling throughout the tensile region. Under a 60N load applied at room temperature, the toughened composite coating exhibits a low average coefficient of friction.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that a 3% polyvinyl alcohol solution was used, and no toughening mesh was added. Instead, the mixed powder was directly pre-placed on the surface of the treated steel substrate and then dried. The thickness of the mixed powder on the steel substrate was 1 mm.

[0048] Testing revealed that the cladding layer was uneven and contained numerous cracks, such as... Figure 1 As shown in (d), the cladding layer structure mainly consists of (Fe, Cr) solid solution and WC, Cr3C2, Cr 23 C6 and Cr7C3, etc. From Figure 5 As can be seen, the composite coating without the addition of a tough mesh exhibits significant residual tensile stress. Figure 6 e represents the tensile results according to the national standard GB / T 228.1-2021 (Metallic materials, tensile testing—Part 1: Test method at room temperature). The tensile specimen without the addition of a toughening mesh exhibits numerous cracks in the coating and a very rough surface, with significant brittle spalling throughout the tensile region. Under a 60N load at room temperature, the composite coating without the addition of a toughening mesh has the highest average coefficient of friction and the worst wear resistance.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that the laser cladding process parameters were adjusted to: laser power 1800W, scanning speed 2mm / s, while the rest of the preparation process remained unchanged.

[0050] Testing revealed that the surface formation quality of the cladding layer was extremely poor, exhibiting significant unevenness and substantial defects. The ductile mesh had been completely melted, failing to form a proper metallurgical bond. Figure 1 As shown in (e).

[0051] Comparative Example 3 The difference between this comparative example and Example 1 is that the laser cladding process parameters are adjusted to: laser power 1300W, scanning speed 2mm / s, while the rest of the preparation process remains unchanged.

[0052] Testing revealed that the surface forming quality of the cladding layer remained very poor, with significant defects appearing in the middle of the cladding layer. Furthermore, the tough mesh failed to form a good metallurgical bond with the coating. Figure 1 As shown in (f).

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A cladding process for adding a tough mesh composite coating, characterized in that, The steps are as follows: (1) Remove rust and polish the surface of the steel material, then clean it with ethanol and dry it to obtain a spare steel substrate; (2) Add WC powder to Fe5 alloy powder, mix evenly, then dry and ball mill to obtain mixed powder; (3) Add polyvinyl alcohol solution to the mixed powder and mix evenly to obtain a pre-made wet powder; after laying the tough mesh on the surface of the spare steel, combine it with the pre-made wet powder and dry it to obtain a composite tough mesh; under argon protection, laser cladding the composite tough mesh onto the surface of the spare steel to form a toughened composite coating; the laser cladding process parameters are: laser power 1450-1650W, scanning speed 1-2mm / s, spot size 25mm×1mm rectangular spot, gas delivery rate 8-12L / min, and defocusing amount 12-15mm.

2. The cladding process for the composite coating according to claim 1, characterized in that, Step (3) The thickness of the pre-prepared wet powder in the composite toughness mesh is 1-1.2 mm.

3. The cladding process for the composite coating according to claim 1, characterized in that, In step (3), the composite tough mesh is prepared using any of the following methods: The first method involves placing a flat, square-hole tough mesh sheet tightly against a stainless steel substrate on a two-dimensional plane. A 2-4% polyvinyl alcohol solution is mixed with the mixed powder and then spread on the tough mesh to obtain a doped tough mesh P. After drying, a composite tough mesh A is obtained. The second method involves diagonally stretching a square-hole tough mesh into a diamond-shaped tough mesh, then placing a layer of polyvinyl alcohol solution (2-4% by mass) mixed with the powder on a stainless steel substrate, and then drying it to obtain composite tough mesh B. The third method involves laying a second layer of square-hole toughness mesh on the top layer of the doped toughness mesh P, pressing it down, and then drying it to obtain a composite toughness mesh C.

4. The cladding process for the composite coating according to claim 3, characterized in that, The square-hole tough mesh is any one of 20 mesh × Φ0.08W mesh, 40 mesh × Φ0.1W mesh, 20 mesh × Φ0.12W mesh, and 40 mesh × Φ0.1Mo mesh. The mixed powder consists of 65-75 parts by weight of Fe5 alloy powder and 25-35 parts by weight of WC powder. The Fe5 alloy powder contains elements C, Cr, Si, Mn, B, and Fe, wherein the weight fraction of Fe element is 50-55%.

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