Gradient composite high-toughness wear-resistant coating and application and preparation method thereof

Abstract

The invention relates to the field of metal coatings, and discloses a gradient composite high-toughness wear-resistant coating and application and a preparation method thereof, the gradient composite high-toughness wear-resistant coating comprises a substrate layer, a middle layer cladded on the substrate layer and a boriding layer on the surface; the base layer is made of a FeCoCrNiTi high-entropy alloy; the middle layer comprises a plurality of laminated composite material layers, and the composite material layers contain TiB2 and FeCoCrNiTi high-entropy alloy; in the direction from the substrate layer to the boriding layer, the content of TiB2 in the composite material layer is gradually increased, and in the composite material layer attached to the boriding layer, the content of TiB2 is 16-20 wt%. The gradient composite high-toughness wear-resistant coating is suitable for strengthening agricultural soil-touching parts, resisting operation impact and reducing the abrasive particle abrasion condition, so that the service life of the soil-touching parts is prolonged, and the operation cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metal coatings, and in particular to a gradient composite high-toughness wear-resistant coating and an application and preparation method thereof. Background Art

[0002] The soil-contacting parts of agricultural machinery will fail due to wear from soil particles during contact with the soil, which is the main reason for their failure. The soil-contacting parts currently used cannot meet the needs of long-term agricultural operations. Since the soil in hilly areas contains many hard objects, the soil-contacting parts used in this area are often subjected to large impact loads, which cause greater wear. In the long run, the service life of the soil-contacting parts will be greatly reduced. The most common problem is the wear of the rotary tiller blade. Therefore, the wear resistance of the soil-contacting parts of agricultural machinery is an important issue that needs to be urgently solved in the current development of agricultural machinery. At present, most agricultural soil-contacting parts face poor heat resistance, are prone to large thermal deformation, have low hardness, poor wear resistance, and poor strength, and cannot complete the soil-contacting operation tasks well.

[0003] In the prior art, a single-layer high-entropy alloy coating is usually used to form a hard coating on the surface of the soil-contacting component substrate, thereby improving the hardness and wear resistance of the soil-contacting component, such as the disclosed application: an in-situ preparation method and product of a laser additively manufactured high-entropy alloy. However, due to the complexity of the soil environment, the single-layer high-entropy alloy coating suffers from severe abrasive wear, and its toughness is insufficient to resist the impact of the operation process, making it difficult to provide adequate protection for the soil-contacting component. Among gradient coatings, there are currently few that combine TiB2 and high-entropy alloy coatings, such as the disclosed technical solution: a tool containing a TiB2 coating and a preparation method thereof. This solution can only provide basic protection for the soil-contacting component, and it is difficult to protect the soil-contacting component when the soil environment is complex. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of low hardness, poor wear resistance and short service life of existing agricultural soil-contacting parts, and to provide a gradient composite high-strength and toughness wear-resistant coating and its application and preparation method. The gradient composite high-strength and toughness wear-resistant coating is suitable for strengthening agricultural soil-contacting parts, reducing abrasive wear, thereby increasing the service life of the soil-contacting parts and reducing operating costs.

[0005] In order to achieve the above-mentioned object, the present invention provides a gradient composite high-toughness wear-resistant coating, which comprises a base layer, an intermediate layer clad on the base layer, and a boronized layer on the surface;

[0006] The material of the base layer is FeCoCrNiTi high entropy alloy;

[0007] The intermediate layer includes a plurality of stacked composite material layers, wherein the composite material layers contain TiB2 and FeCoCrNiTi high entropy alloy; the content of TiB2 in the composite material layers gradually increases from the base layer to the boronized layer, and the content of TiB2 in the composite material layers bonded to the boronized layer is 16 to 20 wt%.

[0008] Further preferably, the content of TiB2 in the composite material layer bonded to the base layer is 5 to 9 wt%;

[0009] The TiB2 content in adjacent composite material layers varies from 2 to 4 wt%.

[0010] The content of TiB2 in the middle layer of the present invention is set according to a gradient ratio, which can enhance the overall hardness of the middle layer and at the same time make it more closely combined with the base layer.

[0011] In the present invention, the FeCoCrNiTi high entropy alloy contains 10-30wt% of Fe, 10-30wt% of Co, 10-30wt% of Cr, 10-30wt% of Ni and 10-30wt% of Ti.

[0012] In the present invention, the thickness of the base layer is 0.4-0.5 mm; the thickness of the intermediate layer is 0.15-0.2 mm; and the thickness of the boronized layer is 20-30 μm.

[0013] The second aspect of the present invention provides an application of the above-mentioned gradient composite high-toughness wear-resistant coating in the protection of agricultural soil-contacting parts (such as rotary tillage blades, furrowing blades, furrowing discs, plowshares and other agricultural soil-contacting parts).

[0014] The gradient composite high-toughness wear-resistant coating of the present invention has a high Ti content in the high entropy alloy used, and there is work hardening, so that the hardness of the soil-contacting parts is increased. The boronized layer can well resist the abrasive wear that occurs after being subjected to impact loads, greatly improving the anti-friction performance of the soil-contacting parts. The base layer and the middle layer can provide high-hardness support for the upper boronized layer, further increasing the anti-friction performance of the soil-contacting parts.

[0015] The third aspect of the present invention provides a method for preparing the above-mentioned gradient composite high-toughness wear-resistant coating, comprising the following steps:

[0016] (1) Pre-treating the surface of the substrate of the agricultural soil-contacting component;

[0017] (2) heating the pretreated agricultural soil-contacting component substrate to 300-350° C., and then using laser cladding technology to clad the FeCoCrNiTi high entropy alloy powder on the surface of the agricultural soil-contacting component substrate under protective gas, and forming a base layer after cooling;

[0018] (3) TiB2 powder and FeCoCrNiTi high entropy alloy powder are mixed to obtain a mixed powder, the agricultural soil-contacting component substrate obtained in step (2) is heated to 300-350° C., and then the mixed powder is clad on the surface of the base layer by laser cladding technology under a protective gas, and an intermediate layer is formed after cooling;

[0019] (4) performing a boronizing pre-treatment on the surface of the intermediate layer;

[0020] (5) Under protective gas, the surface of the intermediate layer after the pre-boronizing treatment is subjected to boronizing, quenching is performed after the boronizing is completed, the first tempering is performed after cooling, the second tempering is performed after cooling, and the boronized layer is formed after cooling.

[0021] In step (1) of the present invention, the specific steps of pre-treating the surface of the substrate of the agricultural soil-contacting component include: cleaning and polishing the surface of the substrate of the agricultural soil-contacting component, and cleaning and drying with alcohol. The purpose is to remove the oxide layer and impurities such as oil stains formed on the surface of the substrate of the agricultural soil-contacting component due to long-term contact with air, and improve the bonding strength with the coating.

[0022] Furthermore, in step (2), the FeCoCrNiTi high entropy alloy powder is dried in advance to remove residual moisture so that the coating effect is better, and then it is clad on the surface of the agricultural soil-contacting component substrate using laser cladding technology, so that it is deposited on the surface of the agricultural soil-contacting component substrate, and a base layer is formed after cooling.

[0023] In the present invention, the protective gas is selected from one or more of nitrogen, helium, neon, argon, krypton and xenon. In a specific embodiment, the protective gas is argon.

[0024] Preferably, in step (2), the particle size of the FeCoCrNiTi high entropy alloy powder is 300-400 mesh.

[0025] Furthermore, in step (2), the conditions of the laser cladding technology include: laser power of 2.2 to 2.4 kW, powder feeding rate of 2.2 to 2.8 g / min, and laser moving speed of 1.8 to 2.2 m / s.

[0026] In a preferred case, in step (2), after FeCoCrNiTi high entropy alloy powder is clad on the surface of the substrate of the agricultural soil-contacting component by laser cladding technology, it is placed in thermal insulation cotton and naturally cooled to form a base layer; wherein the cooling rate of natural cooling in the thermal insulation cotton is slower than that in the natural environment, which can increase the strength of the coating and achieve better results.

[0027] In step (3) of the present invention, the TiB2 powder and the FeCoCrNiTi high entropy alloy powder are first dried (drying is also for removing residual moisture so that the coating can perform better), and then mixed in different proportions to obtain mixed powders with different TiB2 contents. The mixed powders are then clad on the surface of the base layer using a multi-barrel powder feeding laser cladding technology, and an intermediate layer is formed after cooling.

[0028] Preferably, in step (3), the particle size of the FeCoCrNiTi high entropy alloy powder is 200-300 mesh, and the particle size of the TiB2 powder is 150-300 mesh.

[0029] Further in step (3), the conditions of the laser cladding technology include: laser power of 2.2 to 2.4 kW, powder feeding rate of 2.2 to 2.8 g / min, and laser moving speed of 1.8 to 2.2 m / s.

[0030] In the preferred case of step (3), in order to increase the strength of the coating, after the mixed powder is clad on the surface of the base layer using laser cladding technology, it is placed in thermal insulation cotton and is naturally cooled to form an intermediate layer.

[0031] The laser cladding technologies used above are all conventional technical operations in this field, and the amount of FeCoCrNiTi high entropy alloy powder and mixed powder used is only required to ensure that the thickness of the formed base layer and the intermediate layer meet the requirements.

[0032] In step (4) of the present invention, the purpose of performing a boronizing pretreatment on the surface of the intermediate layer is to enhance the bonding strength, wherein the specific steps of the boronizing pretreatment include: polishing the surface of the intermediate layer using 400#, 600# and 800# SiC sandpaper in sequence until obvious traces disappear and the surface is uniform, then mechanically polishing with a diamond spray polishing agent, then cleaning the surface with alcohol for 10 to 30 minutes, and then drying.

[0033] Furthermore, in step (5), the agricultural soil-contacting component substrate obtained in step (4) is completely placed in a boronizing agent (ensuring that the surface of the intermediate layer is completely in contact with the boronizing agent), and then the surface of the intermediate layer after the boronizing pre-treatment is boronized, and the boronizing conditions include: a temperature of 800 to 1200°C and a time of 8 to 10 hours.

[0034] When boriding is carried out under the above conditions, the boriding agent and the coating have a better combination effect.

[0035] The boronizing process uses a mixture of ferroboron (FeB) alloy and silicon carbide (SiC), and the weight ratio of the ferroboron alloy to silicon carbide is 1:12-20.

[0036] The above-mentioned boronizing adopts the conventional thermal diffusion boronizing technology in the art, and the amount of the boronizing agent used is sufficient as long as the thickness of the final boronized layer meets the requirements.

[0037] Furthermore, in step (5), quenching is performed to improve the structural properties, enhance the wear resistance and fatigue strength, wherein the specific operation of the quenching includes: keeping warm at 820-860°C for 8-12 minutes and then oil quenching; then cooling to room temperature, followed by washing, performing the first tempering, and performing the second tempering after cooling to room temperature. The tempering is to improve the structural stability and eliminate internal stress, wherein the conditions of the first tempering include: temperature of 180-220°C and time of 0.5-1.5h; the conditions of the second tempering include: temperature of 400-450°C and time of 3-4h; after the second tempering, cooling to room temperature and then washing to form a boronized layer.

[0038] In a specific embodiment, after the boriding layer is finally obtained in step (5), gauze and polishing cloth dipped in anhydrous ethanol are used to remove obvious impurities and high protruding burrs on the surface.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention forms a high entropy alloy FeCoCrNiTi base layer on the surface of agricultural soil-contacting parts through laser cladding technology, and then laser clads an intermediate layer on the surface of the high entropy alloy FeCoCrNiTi base layer through a laser cladding process, and finally boronizes the surface of the intermediate layer to form a boronized protective layer. The high entropy alloy FeCoCrNiTi base layer will form a protective layer on the surface of the agricultural soil-contacting parts, and the wear resistance of the substrate will be increased and the wear will be reduced. The addition of the intermediate layer will protect the high entropy alloy FeCoCrNiTi base layer and increase the wear resistance of the agricultural soil-contacting parts. The laser cladding process ensures the hardness and toughness between the substrate and the coating, and between the coatings. The addition of the boronized layer greatly increases the anti-friction performance of agricultural soil-contacting parts, wherein the laser cladding technology and the boronizing technology ensure the bonding between the coatings and between the substrate and the coating;

[0041] 2. The high-entropy alloy has a high Mn content, which causes work hardening and increases the hardness of the soil-contacting parts. When the boronized layer is subjected to impact load, abrasive wear occurs, which can increase wear resistance, reduce wear, and reduce the adverse effects of impact. In addition, the base layer and the middle layer can provide high-hardness support for the upper boronized layer, increase the anti-friction performance of the soil-contacting parts, and reduce the adverse effects of impact in harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of the gradient composite high-toughness wear-resistant coating in Example 1 of the present invention;

[0043] Figure 2 This is a morphological diagram of the cross section of the gradient composite high-strength and toughness wear-resistant coating obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0045] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0046] The specific implementation modes of the present invention will be described below through examples.

[0047] The room temperature referred to in the following examples is 25° C. The FeCoCrNiTi high entropy alloy used was purchased from Qinghe County Xindun Jinwu Materials Co., Ltd., and the FeCoCrNiTi high entropy alloy contained 22wt% Fe, 24wt% Co, 18wt% Cr, 19wt% Ni and 17wt% Ti.

[0048] Example 1

[0049] (1) Clean and polish the surface of the substrate of the agricultural soil-contacting component, clean it with alcohol and blow it dry;

[0050] (2) drying the FeCoCrNiTi high entropy alloy powder with a particle size of 325 mesh, heating the agricultural soil-contacting component substrate obtained in step (1) to 300° C., and then cladding the dried FeCoCrNiTi high entropy alloy powder on the surface of the agricultural soil-contacting component substrate using laser cladding technology under argon protection (the conditions of the laser cladding technology include: laser power of 2.4 kW, powder feeding amount of 2.5 g / min, and laser moving speed of 2 m / s), and then placing it in thermal insulation cotton, and forming a base layer after natural cooling;

[0051] (3) drying TiB2 powder with a particle size of 200 mesh and FeCoCrNiTi high entropy alloy powder with a particle size of 250 mesh, and mixing them in different proportions to obtain mixed powders with different TiB2 contents; heating the agricultural soil-contacting component substrate with a base layer obtained in step (2) to 300° C., and then cladding the mixed powders on the surface of the base layer using laser cladding technology under argon protection (the conditions of the laser cladding technology include: laser power of 2.4 kW, powder feeding amount of 2.5 g / min, and laser moving speed of 2 m / s); and then placing the mixed powders in thermal insulation cotton, and forming an intermediate layer after natural cooling.

[0052] (4) grinding the surface of the intermediate layer obtained in step (3) with 400#, 600# and 800# SiC sandpaper in sequence until obvious marks disappear and the surface is uniform, and then mechanically polishing with a diamond spray polishing agent, followed by cleaning the surface with alcohol for 20 minutes, and then drying;

[0053] (5) Under argon protection, the agricultural soil-contacting component substrate obtained in step (4) is completely placed in a boronizing agent (ensuring that the surface of the intermediate layer is completely in contact with the boronizing agent), and then the surface of the intermediate layer after the pre-boronizing treatment is boronized, the boronizing agent is a mixture of ferroboron alloy and silicon carbide, the weight ratio of ferroboron alloy to silicon carbide is 1:15, and the conditions of boronizing include: temperature of 1000°C and time of 8 hours; quenching after the completion of boronizing, the specific operation of quenching includes: oil quenching after keeping at 840°C for 10 minutes, cooling to room temperature after quenching, washing, and then performing the first tempering, the conditions of the first tempering include: temperature of 200°C and time of 1 hour, cooling to room temperature and performing the second tempering, the conditions of the second tempering include: temperature of 425°C and time of 3 hours, cooling to room temperature after the completion of the second tempering, and then washing to form a boronized layer, and using gauze and polishing cloth dipped in anhydrous ethanol to remove more obvious impurities and high protruding burrs on the surface;

[0054] The gradient composite high-toughness wear-resistant coating obtained in this embodiment includes a base layer clad on the surface of the agricultural soil-contacting component substrate, an intermediate layer clad on the base layer, and a boronized layer on the surface. The schematic diagram of its structure is shown in FIG. Figure 1 As shown; the material of the base layer is FeCoCrNiTi high entropy alloy; the middle layer includes 6 stacked composite material layers, and the composite material layers contain TiB2 and FeCoCrNiTi high entropy alloy; from the base layer to the boronized layer, the content of TiB2 in the composite material layer gradually increases, and the content of TiB2 in the composite material layer bonded to the boronized layer is 20.0wt%; the content of TiB2 in the first composite material layer bonded to the base layer is 5.0wt%; the content of TiB2 in the adjacent composite material layers varies by 3wt%;

[0055] The thickness of the base layer is 0.45 mm;

[0056] The thickness of the middle layer is 0.18mm;

[0057] The thickness of the boronized layer is 25 μm;

[0058] The morphology of the agricultural soil-contacting component with the gradient composite high-toughness wear-resistant coating obtained in this embodiment was observed: the cross-sectional morphology of the gradient composite high-toughness wear-resistant coating was observed by FEI Sirion IMP (scanning electron microscope), as shown in FIG. Figure 2 As shown, the overall coating is composed of three layers, and the layers are arranged closely, which shows that the bonding force between the layers is good, it is not easy to fall off, and it has strong wear resistance.

[0059] Comparative Example 1

[0060] The method of Example 1 is used, except that the middle layer includes 4 stacked composite material layers, and the content of TiB2 in the composite material layer bonded to the boronized layer is 14.0 wt%.

[0061] Comparative Example 2

[0062] The method of Example 1 is followed, except that the intermediate layer is not subjected to boronizing pretreatment and boronizing treatment, i.e., there is no boronized layer, and gauze and polishing cloth dipped in anhydrous ethanol are directly used to remove the more obvious impurities and high protruding burrs on the surface of the intermediate layer obtained in step (3).

[0063] Test Case

[0064] The following tests were performed on the agricultural soil-contacting parts with gradient composite high-toughness wear-resistant coatings obtained in Example 1 and Comparative Examples 1-2, and the test results are shown in Table 1:

[0065] Hardness test: The test was conducted by using a nano-indenter (G200, Agilent technologies, USA) using the continuous stiffness measurement method (CSM). The indenter was a diamond Berkovich tetrahedron indenter, and the tip roundness of the new indenter was less than 20 nanometers. The maximum load was 500mN, and the load resolution was 50nN. The displacement resolution was less than 0.01nm, using electromagnetic actuation and a capacitive sensor for measurement.

[0066] Friction coefficient test: The gradient composite high-strength and toughness wear-resistant coating was subjected to friction and wear experiments using a multifunctional friction tester (RTEC MFT-5000). The friction and wear experiments were conducted in a reciprocating sliding mode at a frequency of 5 Hz and a load of 5 N for 15 minutes; the sliding distance was 5 mm, and the friction pair used a 304 stainless steel ball with a diameter of 6 mm.

[0067] Table 1

[0068]

[0069] It can be seen from the results in Table 1 that, when Example 1 is compared with Comparative Example 1 and Comparative Example 2, the gradient composite high-strength and toughness wear-resistant coating of Example 1 has a higher hardness (29.52 GPa) and a lower friction coefficient (0.11), indicating that the gradient composite high-strength and toughness wear-resistant coating of the present invention has a higher hardness and good wear resistance, and correspondingly, its ability to resist impact deformation is also better, and its toughness is high, which can extend the use time and has a longer service life.

[0070] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0071] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A gradient composite high-toughness wear-resistant coating, characterized in that: The gradient composite high-toughness wear-resistant coating comprises a base layer, an intermediate layer clad on the base layer, and a boronized layer on the surface; The material of the base layer is FeCoCrNiTi high entropy alloy; The intermediate layer includes a plurality of stacked composite material layers, wherein the composite material layers contain TiB2 and FeCoCrNiTi high entropy alloy; the content of TiB2 in the composite material layers gradually increases from the base layer to the boronized layer, and the content of TiB2 in the composite material layers bonded to the boronized layer is 16 to 20 wt%.

2. The gradient composite high-toughness wear-resistant coating according to claim 1 is characterized in that: The FeCoCrNiTi high entropy alloy contains 10-30wt% of Fe, 10-30wt% of Co, 10-30wt% of Cr, 10-30wt% of Ni and 10-30wt% of Ti.

3. The gradient composite high-toughness wear-resistant coating according to claim 1 is characterized in that: In the composite material layer bonded to the base layer, the content of TiB2 is 5 to 9 wt%; The TiB2 content in adjacent composite material layers varies from 2 to 4 wt%.

4. The gradient composite high-toughness wear-resistant coating according to claim 1 is characterized in that: The thickness of the base layer is 0.4 to 0.5 mm; The thickness of the intermediate layer is 0.15 to 0.2 mm; The thickness of the boronized layer is 20-30 μm.

5. Application of the gradient composite high-toughness wear-resistant coating according to any one of claims 1 to 4 in the protection of agricultural soil-contacting parts.

6. The method for preparing the gradient composite high-toughness wear-resistant coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Pre-treating the surface of the substrate of the agricultural soil-contacting component; (2) heating the pretreated agricultural soil-contacting component substrate to 300-350° C., and then using laser cladding technology to clad the FeCoCrNiTi high entropy alloy powder on the surface of the agricultural soil-contacting component substrate under protective gas, and forming a base layer after cooling; (3) TiB2 powder and FeCoCrNiTi high entropy alloy powder are mixed to obtain a mixed powder, the agricultural soil-contacting component substrate obtained in step (2) is heated to 300-350° C., and then the mixed powder is clad on the surface of the base layer by laser cladding technology under a protective gas, and an intermediate layer is formed after cooling; (4) performing a boronizing pre-treatment on the surface of the intermediate layer; (5) Under protective gas, the surface of the intermediate layer after the pre-boronizing treatment is subjected to boronizing, quenching is performed after the boronizing is completed, the first tempering is performed after cooling, the second tempering is performed after cooling, and the boronized layer is formed after cooling.

7. The preparation method according to claim 6, characterized in that: In step (2), the particle size of the FeCoCrNiTi high entropy alloy powder is 300-400 mesh; In step (2), the conditions of the laser cladding technology include: laser power of 2.2 to 2.4 kW, powder feeding rate of 2.2 to 2.8 g / min, and laser moving speed of 1.8 to 2.2 m / s.

8. The preparation method according to claim 6 or 7, characterized in that: In step (3), the particle size of the FeCoCrNiTi high entropy alloy powder is 200-300 mesh, and the particle size of the TiB2 powder is 150-300 mesh; In step (3), the conditions of the laser cladding technology include: laser power of 2.2 to 2.4 kW, powder feeding rate of 2.2 to 2.8 g / min, and laser moving speed of 1.8 to 2.2 m / s.

9. The preparation method according to claim 6, characterized in that: In step (5), the boronizing conditions include: temperature of 800-1200° C. and time of 8-10 h; The boronizing agent used for boronizing is a mixture of ferroboron alloy and silicon carbide, and the weight ratio of ferroboron alloy to silicon carbide is 1:12-20.

10. The preparation method according to claim 6, characterized in that: In step (5), the specific operation of quenching includes: keeping the temperature at 820-860° C. for 8-12 minutes and then oil quenching; The conditions of the first tempering include: a temperature of 180 to 220° C. and a time of 0.5 to 1.5 h; The conditions for the second tempering include: a temperature of 400 to 450° C. and a time of 3 to 4 hours.

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