A method for preparing a TaWNbC particle-reinforced aluminum-based composite coating

Abstract

This invention discloses a method for preparing a TaWNbC particle-reinforced aluminum-based composite coating, comprising the following steps: mixing TaWNbC composite powder and pure aluminum powder uniformly under the protection of a protective gas to obtain a composite powder; sequentially subjecting the matrix material to sanding, ultrasonic cleaning with anhydrous ethanol, and drying to obtain a pretreated substrate; mixing the composite powder with sodium silicate binder and adding deionized water to obtain a coating slurry; uniformly coating the coating slurry onto the surface of the pretreated substrate and drying to obtain a pre-coated layer; and performing laser cladding treatment using a fiber laser under argon protection to form a TaWNbC-Al composite coating on the surface of the pretreated substrate. This invention optimizes the composition of the TaWNbC composite powder and pure aluminum powder, and optimizes the coating preparation process, thereby forming a dense TaWNbC-Al composite coating on the substrate surface. The high-melting-point strengthening elements such as Nb, Ta, and W in the composite coating can effectively improve the coating's hardness, wear resistance, and high-temperature stability, while simultaneously improving the problems of low hardness and poor wear resistance in ordinary aluminum coatings.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and specifically to a method for preparing a TaWNbC particle-reinforced aluminum-based composite coating. Background Technology

[0002] Titanium alloys, especially TC4 titanium alloys, have advantages such as high specific strength and good corrosion resistance, but their surface hardness and wear resistance are still insufficient to meet the requirements of high-load friction and wear conditions. Laser cladding to prepare a lightweight aluminum-based composite coating on the surface of TC4 titanium alloys can improve surface wear resistance while maintaining the lightweight advantage of the components.

[0003] Laser cladding technology, as a high-energy beam surface modification method, has advantages such as high energy density, small heat-affected zone, low dilution rate, and good metallurgical bonding between the coating and the substrate. It can prepare dense, high-performance functional coatings on metal substrates and has shown promising application prospects in the preparation of wear-resistant, corrosion-resistant, and high-temperature resistant coatings. However, due to the high reflectivity and thermal conductivity of aluminum alloys to lasers, problems such as unstable molten pools, poor coating quality, cracks, and porosity defects easily occur during laser cladding. These issues urgently need to be addressed by optimizing the composition of the cladding materials and the laser cladding process.

[0004] Refractory alloys Ta, W, and Nb possess characteristics such as high melting point, high elastic modulus, high hardness, and excellent wear resistance and high-temperature resistance, along with good thermal stability. Introducing them as reinforcing phases into aluminum-based surface coatings is expected to significantly improve the wear resistance and high-temperature service performance of the coating while maintaining the lightweight advantage of the aluminum matrix. Furthermore, the Ta-W-Nb-C system exhibits better interfacial wettability with Al-based alloys, which is more conducive to forming a stable metallurgical bonding interface, thereby improving the overall mechanical properties and service reliability of the coating. Currently, research on laser cladding of aluminum-based composite coatings on titanium alloy surfaces mainly focuses on ceramic particle-reinforced coatings or conventional alloy coatings. Although these methods improve surface hardness and wear resistance to some extent, they generally suffer from insufficient interfacial bonding, high crack sensitivity, and high coating brittleness, limiting their engineering applications. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing a TaWNbC particle-reinforced aluminum-based composite coating. This method optimizes the composition of pure aluminum powder and TaWNbC system composite powder and the laser cladding process parameters, thereby forming a composite coating with dense structure, good interfacial bonding, and excellent wear resistance and high temperature resistance on the substrate surface.

[0006] To better solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for preparing a TaWNbC particle-reinforced aluminum-based composite coating includes the following steps:

[0008] (1) The TaWNbC composite powder and pure aluminum powder are mixed evenly under the protection of a protective gas to obtain the composite powder;

[0009] (2) The substrate material is successively sanded with sandpaper, ultrasonically cleaned with anhydrous ethanol, and naturally dried to obtain the pretreated substrate.

[0010] (3) After mixing the composite powder with sodium silicate binder, deionized water is added to obtain the coating slurry;

[0011] (4) The above coating slurry is uniformly coated on the surface of the pretreated substrate and dried to form a pre-coated coating;

[0012] (5) Under argon protection, a fiber laser is used for laser cladding to form a TaWNbC-Al composite coating on the surface of the pretreated substrate material.

[0013] Preferably, in step (1), the protective gas is Ar gas.

[0014] Preferably, in step (1), the stirring speed during mixing is 100-200 rpm and the time is 5-10 h.

[0015] Preferably, in step (1), the mass fraction of the TaWNbC system composite powder in the composite powder is 50-60 wt.%, and the remainder is pure aluminum powder, and the sum of the two is 100%.

[0016] Preferably, in step (2), the substrate material is TC4 titanium alloy; and the sandpaper used for polishing is 600 mesh.

[0017] Preferably, in step (2), the ultrasonic frequency of the ultrasonic treatment is 35-45KHz and the time is 15-20min.

[0018] Preferably, in step (2), the surface roughness of the pretreated substrate is controlled to be Ra 3.2 to 6.3 μm.

[0019] Preferably, in step (3), the mass ratio of the composite powder to the sodium silicate binder is (10-15):1; and the solid content of the coating slurry is 82 wt.%–86 wt.%.

[0020] Preferably, in step (4), the coating thickness is 1.5-2.5 mm.

[0021] Preferably, in step (4), the drying temperature is 200℃ and the time is 1-3h.

[0022] Preferably, in step (5), the laser power during laser cladding is 300-500W, the scanning speed is 4-8mm / s, the overlap rate is 70%, the spot diameter is 2mm, and the argon protective gas flow rate is 12-15L / min.

[0023] Preferably, in step (5), the thickness of the TaWNbC-Al composite coating is 0.8-1.2 mm.

[0024] After drying and laser cladding, a dense cladding coating with a thickness of 0.8–1.2 mm is finally formed due to the elimination of pores between powder particles and the spreading of the molten pool.

[0025] The preparation method of the TaWNbC system composite powder in this invention includes the following steps:

[0026] Nb powder, TaC powder, W powder, deionized water, dispersant, and binder are mixed according to the formula and then prepared into a uniform slurry by high-energy ball milling.

[0027] The homogeneous slurry was centrifugally spray-dried and granulated under conditions of inlet air temperature of 180-220℃, outlet air temperature of 80-120℃, and centrifugal speed of 10000-15000 rpm to obtain precursor powder with a particle size of 10-100 μm. The precursor powder was degreased to remove residual organic matter and adsorbed impurities. The degreased powder was then spheroidized by radio frequency plasma using high-purity Ar as the carrier gas and high-purity Ar and H2 as sheath gas, with an H2 volume fraction of 1-10% in the sheath gas. The carrier gas flow rate was 2-5 L / min, and the sheath gas flow rate was 30-60 L / min. Under a power of 30-50 kW, the particles were rapidly melted in a high-temperature plasma flame, their surface tension contracted into spheres, and they rapidly solidified. After being graded and sieved, a TaWNbC composite powder with a sphericity ≥0.9, oxygen content ≤800 ppm, flowability ≤35 s / 50 g, and controllable particle size was obtained.

[0028] The atomic ratio of Nb, Ta, C, and W in the TaWNbC composite powder is 1:1:1:1; the amount of binder added is 2-8 wt.% of the total mass of Nb, TaC, and W powders, and the amount of dispersant added is 0.1-0.2 wt.% of the total mass of Nb, TaC, and W powders. The solid content of the slurry is 60 wt.%; the dispersant is PAANH4, and the binder is PVA.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] This invention forms a pre-coated layer on the substrate surface by mixing TaWNbC composite powder with pure aluminum powder and sodium silicate binder, which avoids the problems of low powder utilization and uneven cladding layer thickness in traditional laser synchronous powder feeding processes and improves process stability.

[0031] This invention utilizes the high-energy heat input during laser cladding to fully melt the TaWNbC component, which then undergoes a metallurgical reaction with the Al-based coating and TC4 substrate to form a dense TaWNbC-Al composite coating, significantly improving the bonding strength between the coating and the substrate.

[0032] The composite coating prepared by this invention contains high-melting-point strengthening elements such as Nb, Ta, and W, which can effectively improve the coating's hardness, wear resistance, and high-temperature stability, while also improving the problems of low hardness and poor wear resistance in ordinary aluminum coatings. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 Process flow diagram for preparing TaWNbC particle-reinforced aluminum-based composite coating;

[0035] Figure 2 This is a SEM image of the interface between the cladding coating and the substrate in Example 1;

[0036] Figure 3 This is a SEM image of the cladding coating area in Example 1;

[0037] Figure 4 This is an EDS surface scan of the cladding coating area in Example 1;

[0038] Figure 5 This is an EDS line scan image of the cladding coating and the substrate in Example 1. Detailed Implementation

[0039] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0040] The TaWNbC composite powder was prepared as follows in the examples below:

[0041] 197.8 g of Nb powder, 410.81 g of TaC powder, and 391.39 g of W powder were weighed as raw material powders, wherein the atomic ratio of Ta to C in the TaC powder was 1:1; the purity of the Nb powder, TaC powder, and W powder was not less than 99.5%, and the average particle size was 2 μm. Separately, 622.33 g of deionized water, 1.67 g of dispersant (PAANH4), and 41.67 g of polyvinyl alcohol (PVA-1788) were also taken.

[0042] First, PVA-1788 was added to deionized water and stirred to dissolve at 85°C. After cooling to room temperature, a dispersant (PAANH4) was added, and stirring continued until completely dispersed to obtain an organic additive solution. Subsequently, Nb powder, TaC powder, and W powder were added to the organic additive solution, pre-dispersed by mechanical stirring, and then placed in a high-energy ball mill for wet ball milling. The ball milling media were hard alloy balls, with a ball-to-material mass ratio of 5:1, a ball milling speed of 250 rpm, and a ball milling time of 15 h, resulting in a uniformly dispersed composite slurry without obvious agglomeration.

[0043] The obtained composite slurry was subjected to centrifugal spray drying and granulation. During the spray drying process, the inlet air temperature was controlled at 200℃, the outlet air temperature was controlled at 100℃, the centrifugal atomizing disc speed was 12000 rpm, and the slurry feed rate was 30 mL / min. After spray drying, the Ta-W-Nb-C system precursor powder was obtained. Then, the Ta-W-Nb-C system precursor powder was heated to 500℃ at a heating rate of 2℃ / min under a vacuum of less than 10 Pa and held at this temperature for 2 hours for degreasing.

[0044] The degreased powder was placed in an RF plasma spheroidizing device for spheroidization. During spheroidization, high-purity Ar was used as the carrier gas, and high-purity Ar and H2 were used as sheath gases. The volume fraction of H2 in the sheath gas was 3%. The carrier gas flow rate was 3 L / min, the Ar sheath gas flow rate was 45 L / min, the plasma power was 40 kW, and the powder feed rate was 20 g / min. After the powder entered the high-temperature plasma flame with the Ar carrier gas, it rapidly melted in a very short time and contracted into spheres under the action of surface tension. Subsequently, it rapidly solidified in the cooling zone and was then graded and sieved to obtain a sphericity of 0.93, an oxygen content of 620 ppm, a flow velocity of 31.21 s / 50 g, and a loose density of 2.46 g / cm³. 3 A TaWNbC composite powder with an average particle size of 30 μm.

[0045] Example 1

[0046] like Figure 1 As shown, a method for preparing a TaWNbC particle-reinforced aluminum-based composite coating includes the following steps:

[0047] (1) Weigh out TaWNbC composite powder and pure aluminum powder respectively, with a mass ratio of 1:1; place TaWNbC composite powder and pure aluminum powder in a powder mixing device, and mix them at a speed of 150 rpm for 8 hours under a protective atmosphere to obtain mixed powder.

[0048] (2) TC4 titanium alloy (Ti-6Al-4V, size 50mm×20mm×5mm) was selected as the substrate material. First, the surface of the substrate material was polished with 600-grit sandpaper to remove the surface oxide scale. Then, the substrate material was placed in a beaker containing anhydrous ethanol to completely immerse it in the ethanol and ultrasonically cleaned for 20 minutes to remove surface oil and impurities. After cleaning, it was naturally dried to obtain a pretreated substrate with a surface roughness of Ra 4.5 μm for later use.

[0049] (3) The composite powder and sodium silicate binder are mixed in a mass ratio of 12:1, and an appropriate amount of deionized water is added and mechanically stirred evenly to obtain a coating slurry with a solid content of 84.4 wt.%.

[0050] (4) The coating slurry is uniformly coated on the surface of the pretreated substrate obtained in step (2) with a coating thickness of 2.0 mm; then the coated sample is placed in a drying oven and kept at 200°C for 1 hour to allow the moisture in the slurry to evaporate fully and promote the curing of sodium silicate binder, thereby forming a stable solid pre-coated coating on the TC4 substrate surface.

[0051] (5) Laser cladding was performed using an IPG Photonics fiber laser under an argon protective atmosphere. The process parameters for laser cladding were: laser power of 460W, scanning speed of 5mm / s, overlap rate of 70%, spot diameter of 2mm, and argon protective gas flow rate of 15L / min, thereby forming a TaWNbC-Al composite coating on the TC4 substrate surface. The resulting coating had a uniform and dense structure, and a good metallurgical bonding interface was formed between the coating and the substrate.

[0052] Example 2

[0053] A method for preparing a TaWNbC particle-reinforced aluminum-based composite coating includes the following steps:

[0054] (1) Weigh out TaWNbC composite powder and pure aluminum powder respectively, with a mass ratio of 6:4; place TaWNbC composite powder and pure aluminum powder in a powder mixing device, and mix them for 8 hours at a speed of 150 rpm under the protection of protective gas to obtain mixed powder.

[0055] (2) TC4 titanium alloy (Ti-6Al-4V, size 50mm×20mm×5mm) was selected as the substrate material. First, the surface of the substrate material was polished with 600-grit sandpaper to remove the surface oxide scale. Then, the substrate material was placed in a beaker containing anhydrous ethanol to completely immerse it in the ethanol and ultrasonically cleaned for 20 minutes to remove surface oil and impurities. After cleaning, it was naturally dried to obtain a pretreated substrate with a surface roughness of Ra 6.3 μm for later use.

[0056] (3) The composite powder and sodium silicate binder are mixed in a mass ratio of 12:1, and an appropriate amount of deionized water is added and mechanically stirred evenly to obtain a coating slurry with a solid content of 84.4 wt.%.

[0057] (4) The coating slurry is uniformly coated on the surface of the pretreated substrate obtained in step (2) with a coating thickness of 2.5 mm; then the coated sample is placed in a drying oven and kept at 200°C for 3 hours to allow the moisture in the slurry to evaporate fully and promote the curing of sodium silicate binder, thereby forming a stable solid pre-coated coating on the TC4 substrate surface.

[0058] (5) Laser cladding was performed using an IPG Photonics fiber laser under an argon protective atmosphere. The process parameters for laser cladding were: laser power of 500W, scanning speed of 7mm / s, overlap rate of 70%, spot diameter of 2mm, and argon protective gas flow rate of 15L / min, thereby forming a TaWNbC-Al composite coating on the TC4 substrate surface. The resulting coating had a uniform and dense structure, and a good metallurgical bonding interface was formed between the coating and the substrate.

[0059] The microhardness of the products from Examples 1 and 2 was tested, as shown in Table 1.

[0060] Table 1

[0061]

[0062] As shown in Table 1, the hardness of the TaWNbC particle-reinforced aluminum-based composite coating in the examples is significantly higher than that of the TC4 substrate, indicating that the coating surface achieved the most significant strengthening effect after laser cladding. A comparison of Examples 1 and 2 reveals that when the TaWNbC content is increased to 60 wt.%, the Al content in the powder system decreases, the fluidity and wettability of the molten pool decline, and some refractory components are not fully dissolved, leading to a decrease in local microstructure uniformity. Therefore, the hardness is slightly lower than that of the 50 wt.% sample. This indicates that a higher TaWNbC content is not necessarily better; a mass fraction of 50 wt.% is preferred. The significant increase in hardness of the TaWNbC-Al composite coating is mainly attributed to the full melting of high-melting-point elements such as Ta, W, and Nb under high-energy laser irradiation, which react with the Al-based coating to form high-hardness intermetallic compounds or reinforcing phases. Simultaneously, the rapid solidification process induces grain refinement and produces a significant solid solution strengthening effect, thereby significantly improving the surface hardness. In summary, the coating-interface-substrate exhibits a relatively gentle hardness gradient distribution. This gradient change is beneficial to improving the load-bearing capacity of the coating during service and reducing the risk of interface cracking or peeling. At the same time, no obvious cracks or pore defects were found on the coating surface.

[0063] from Figure 2-5 It can be seen that under the high-energy heat input of laser cladding, the TaWNbC composite powder in the pre-formed coating undergoes melting and decomposition. Nb, Ta, W, and C elements rapidly diffuse into the Al molten pool and undergo complex metallurgical reactions with Ti elements from the TC4 matrix. EDS results show that Al and Nb elements are relatively uniformly distributed in the coating, indicating that Nb mainly exists in the form of solid solution strengthening or Al-Nb intermetallic compounds. Ti and W elements are enriched in local areas, indicating that the matrix has undergone some dilution and formed Ti-W strengthening regions. Ta elements are generally uniformly distributed, while C elements have a weak signal, suggesting that they may participate in the formation of fine carbide phases. Overall, the original TaWNbC particles have basically disappeared, and a dense metallurgical bonded coating composed of Al-based solid solution / intermetallic compounds / fine strengthening phases is finally formed.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations 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 scope of the present invention.

Claims

1. A method for preparing a TaWNbC particle-reinforced aluminum-based composite coating, characterized in that, Includes the following steps: (1) The TaWNbC composite powder and pure aluminum powder are mixed evenly under the protection of a protective gas to obtain the composite powder; (2) The substrate material is successively sanded with sandpaper, ultrasonically cleaned with anhydrous ethanol, and naturally dried to obtain the pretreated substrate. (3) After mixing the composite powder with sodium silicate binder, deionized water is added to obtain the coating slurry; (4) The above coating slurry is uniformly coated on the surface of the pretreated substrate and dried to form a pre-coated coating; (5) Under argon protection, a fiber laser is used for laser cladding to form a TaWNbC-Al composite coating on the surface of the pretreated substrate material.

2. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (1), the stirring speed during mixing is 100-200 rpm, and the time is 5-10 h.

3. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (1), the mass fraction of the TaWNbC system composite powder in the composite powder is 50-60 wt.%, and the remainder is pure aluminum powder, with the sum of the two being 100%.

4. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (2), the substrate material is TC4 titanium alloy; the sandpaper used for polishing is 600 mesh.

5. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (2), the ultrasonic frequency of the ultrasonic treatment is 35-45KHz and the time is 15-20min.

6. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (2), the surface roughness of the pretreated substrate is controlled to be Ra 3.2 to 6.3 μm.

7. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (3), the mass ratio of the composite powder to the sodium silicate binder is (10-15):1; the solid content of the coating slurry is 82 wt.%–86 wt.%.

8. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (4), the coating thickness is 1.5-2.5 mm; the drying temperature is 200℃ and the drying time is 1-3 h.

9. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (5), the laser power during laser cladding is 300-500W, the scanning speed is 4-8mm / s, the overlap rate is 70%, the spot diameter is 2mm, and the argon protective gas flow rate is 12-15L / min.

10. The method for preparing a TaWNbC particle-reinforced aluminum-based composite coating according to claim 1, characterized in that, In step (5), the thickness of the TaWNbC-Al composite coating is 0.8-1.2 mm.

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