Composite gradient preparation method of wear-resistant coating on surface of aluminum alloy

Abstract

The invention belongs to the technical field of aluminum alloy surface treatment, and particularly relates to a composite gradient preparation method of an aluminum alloy surface wear-resistant coating, which comprises the following steps: pretreating the aluminum alloy surface, preparing an injection layer with the thickness of 0.05-0.09 mm by adopting a supersonic gas power injection technology, and preparing a transition layer with the thickness of 0.5-0.8 mm by adopting a cold spraying technology, the transition layer is subjected to post-treatment by adopting a laser diffusion technology, and finally, alloy coated powder is cladded on the surface of the transition layer by adopting an ultra-high-speed laser cladding technology, so that the wear-resistant coating with the thickness of 0.7-1.2 mm is prepared; by means of the method, the problems that in the existing aluminum alloy laser cladding layer preparation process, the laser reflectivity is high, a molten pool cannot be effectively formed, the cladding layer dilution rate is high, and air hole defects exist are solved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy surface treatment technology, and specifically relates to a method for preparing a composite gradient of wear-resistant coatings on aluminum alloy surfaces. Background Technology

[0002] Aluminum alloys, due to their advantages such as low density, high strength, good plasticity, corrosion resistance, and good electrical and thermal conductivity, are widely used in aerospace, automotive, mechanical and electronic, and shipbuilding industries. However, under heavy loads, aluminum alloy components interact with other parts, resulting in friction and wear. The degree of wear directly affects the service life and maintenance costs of these components. Therefore, improving the wear resistance of aluminum alloys is a key factor in reducing the frequency of parts replacement and extending their service life.

[0003] Surface strengthening is an effective method to improve the wear resistance of aluminum alloys. Common methods for surface strengthening of aluminum alloys include electroplating, anodizing, physical vapor deposition, and thermal spraying. Among these, the films prepared by electroplating, anodizing, and physical vapor deposition are relatively thin and cannot effectively protect aluminum alloys from heavy-load friction and wear. The coatings prepared by thermal spraying are relatively brittle and are prone to cracking and peeling off under heavy-load friction and wear conditions, thus failing.

[0004] Laser cladding is a surface treatment method that uses a laser beam as a heat source to melt the alloy powder to be clad, which is then deposited on the surface of a substrate, forming a coating through metallurgical bonding. This technology can improve the surface hardness, wear resistance, corrosion resistance, and high-temperature oxidation resistance of materials by selecting different cladding materials. Compared to the technologies mentioned above, the coating prepared by laser cladding bonds to the substrate through metallurgical bonding. The coating is not limited in thickness and has relatively good ductility and toughness, thus significantly improving the heavy-duty friction and wear resistance of the substrate.

[0005] However, the following problems exist when preparing laser cladding coatings on aluminum alloy surfaces: First, aluminum alloys have low laser absorption rates; for a laser with a wavelength of 1.08 μm, the absorption rate is only 6%, and the reflected laser light will damage the cladding head. Second, aluminum alloys have high thermal conductivity; during the cladding process, most of the energy is rapidly dissipated due to this high thermal conductivity, making it difficult to effectively form a molten pool. Third, aluminum alloys have low melting points, easily forming coatings with excessively high dilution rates, affecting coating performance. Finally, aluminum alloys have high electronegativity, easily generating gases with powder materials and air at high temperatures; if these gases cannot escape in time, they can easily form porosity defects within the coating. Therefore, it is urgent to develop new technologies to achieve reliable preparation of wear-resistant coatings on aluminum alloy surfaces. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides a composite gradient preparation method for wear-resistant coatings on aluminum alloy surfaces, solving problems such as high laser reflectivity, ineffective molten pool formation, high dilution rate of the cladding layer, and porosity defects in the existing aluminum alloy laser cladding layer preparation process.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface, comprising the following steps: Step 1: Pre-treat the aluminum alloy surface by using a milling machine to perform milling along the X and Y directions of the aluminum alloy surface. Step 2: The injection layer is prepared using supersonic gas dynamic injection technology. The injection layer powder is injected onto the pretreated aluminum alloy surface to obtain an injection layer with a thickness of 0.05~0.09mm. The injection layer powder is a polygonal powder, which is one of pure Ni, nickel-based 718 or nickel-based 625 powder, with a particle size range of 50~100 μm. Step 3: A transition layer is prepared using cold spraying technology. The transition layer powder is prepared on the surface of the injection layer to obtain a transition layer with a thickness of 0.5~0.8mm. The transition layer is then post-processed using laser diffusion technology. The transition layer powder is a spherical powder, which is one of pure Ni, nickel-based 718 or nickel-based 625 powder, with a particle size range of 15~45 μm. Step 4: Prepare a wear-resistant coating using ultra-high-speed laser cladding technology. Fuse alloy-coated powder onto the surface of the transition layer to obtain a wear-resistant coating with a thickness of 0.7~1.2 mm. The alloy-coated powder is spherical powder, which is iron-based alloy-coated ceramic powder or cobalt-based alloy-coated ceramic powder, with a particle size range of 50~120 μm.

[0008] Preferably, the aluminum alloy is one of ZL101, ZL104, ZL107, ZL201, ZL305 or ZL401 cast aluminum alloy.

[0009] Preferably, the surface roughness of the aluminum alloy surface after milling in step one is Ra6.3~Ra12.5.

[0010] Preferably, during the milling process, the milling cutter speed is 1200~1800 rpm and the feed rate is 100~200 mm / min.

[0011] Preferably, in the process of preparing the injection layer using supersonic gas dynamic injection technology in step two, the supersonic operating gas is air, the operating temperature is 50~100 ℃, the operating pressure is 4~5 MPa, the operating distance is 10~30 mm, the operating speed is 500~1000 mm / min, and the powder feeding rate is 5~20 g / min.

[0012] Preferably, in the process of preparing the transition layer by cold spraying in step three, the main gas and carrier gas of cold spraying are both nitrogen or helium, the spraying temperature is 600~950 ℃, the spraying pressure is 3~5 MPa, the spraying distance is 20~100 mm, the gun speed is 40~100 mm / min, and the powder feeding rate is 20~30 g / min.

[0013] Preferably, in step three, during the post-processing of the transition layer using laser diffusion technology, the laser power is 200~500 W, the scanning speed is 250~500 mm / min, and the lateral movement distance is 1.5~2 mm.

[0014] Preferably, in the process of preparing wear-resistant coating by ultra-high speed laser cladding in step four, both the powder feeding gas and the protective gas are argon, the laser power is 1.8~3.0 kW, the scanning speed is 500~1000 mm / min, the lateral movement distance is 1.2~2.5 mm, the powder feeding rate is 25~50 g / min, and the protective gas flow rate is 16~20 L / min.

[0015] Preferably, the mass percentage of ceramic phase in the alloy-coated powder in step four is 20% to 50%.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: I. This invention employs supersonic gas dynamic injection technology to preferentially prepare an injection layer on the surface of aluminum alloy that is the same as the material of the cold spray transition layer, thus solving the problem that high-quality deposition of cold spray coatings cannot be achieved on the surface of cast aluminum.

[0017] Second, the transition layer prepared by the present invention using cold spraying technology avoids the problem of excessive laser reflectivity of aluminum alloy and prevents the adverse effects of aluminum alloy melting on the coating during the cladding process.

[0018] Third, this invention uses laser diffusion technology to post-process the transition layer. Through element self-diffusion, an intermetallic compound layer is first formed between the injection layer and the substrate interface, which improves the bonding strength between the coating and the substrate. Secondly, the injection layer and the transition layer are fused into one, which further enhances the bonding strength. Finally, the original pores and interparticle interfaces in the cold spray coating are eliminated, and the original internal stress in the coating is removed.

[0019] Fourth, this invention uses alloy-coated powder to prepare the cladding layer, which solves the problem of uneven distribution of ceramic phase particles in the cladding layer and reduces the crack sensitivity of the cladding layer.

[0020] Fifth, this invention uses ultra-high-speed laser cladding technology to prepare wear-resistant coatings, which reduces heat input during the cladding process, avoids thermal deformation of aluminum alloys, and reduces the dilution rate of the coating.

[0021] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein: Figure 1 This describes the microstructure of the gradient coating cross section on the aluminum alloy surface in Embodiment 1 of the present invention.

[0022] Figure 2 This is the hardness curve of the gradient coating section on the aluminum alloy surface in Embodiment 1 of the present invention.

[0023] Figure 3 This is the friction coefficient curve of the aluminum alloy substrate and the wear-resistant coating in Embodiment 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0025] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having meanings consistent with their meanings in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein.

[0026] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] This invention provides a method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface, specifically including the following steps: Step 1: Pre-treat the aluminum alloy surface by using a milling machine to perform milling along the X and Y directions of the aluminum alloy surface. In some embodiments of the present invention, the aluminum alloy is preferably one of ZL101, ZL104, ZL107, ZL201, ZL305 or ZL401 cast aluminum alloy; wherein, the surface roughness of the aluminum alloy after milling is preferably Ra6.3~Ra12.5, for example, Ra6.3, Ra7.5, Ra8.5, Ra9.5, Ra10.5, Ra11.5, Ra12.5; during the milling process, the milling cutter speed is preferably 1200~1800 rpm, for example, 1200 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1800 rpm; and the feed rate is preferably 100~200 mm / min, for example, 100 mm / min, 110 mm / min, 120 mm / min, 130 mm / min, 150 mm / min, 160 mm / min, 180 mm / min, 200 mm / min.

[0028] Step 2: Prepare the injection layer using supersonic gas dynamic injection technology. Inject the injection layer powder onto the pretreated aluminum alloy surface to obtain an injection layer with a preferred thickness of 0.05~0.09 mm, such as 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, or 0.09 mm. The injection layer powder is a polygonal powder, which is one of pure Ni, nickel-based 718, or nickel-based 625 powder, and the particle size range is preferably 50~100 μm, such as 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm. In the process of preparing the injection layer using supersonic gas dynamic injection technology, the supersonic operating gas is air, the operating temperature is preferably 50~100 ℃, for example, 50℃, 60℃, 70℃, 75℃, 80℃, 85℃, 90℃, or 100℃, the operating pressure is preferably 4~5 MPa, for example, 4 MPa, 4.2 MPa, 4.5 MPa, 4.8 MPa, or 5 MPa, the operating distance is preferably 10~30 mm, for example, 10 mm, 15 mm, 18 mm, 20 mm, 25 mm, or 30 mm, the operating speed is preferably 500~1000 mm / min, for example, 500 mm / min, 600 mm / min, 700 mm / min, 800 mm / min, 900 mm / min, or 1000 mm / min, and the powder feeding rate is preferably 5~20 g / min, for example, can be 5 g / min, 8 g / min, 10 g / min, 11 g / min, 13 g / min, 15 g / min, 20 g / min.

[0029] Step 3: A transition layer is prepared using cold spraying technology. The transition layer powder is prepared on the surface of the injection layer to obtain a transition layer with a thickness preferably of 0.5~0.8mm, such as 0.5mm, 0.6mm, 0.7mm, or 0.8mm. The transition layer is then post-treated using laser diffusion technology. The transition layer powder is a spherical powder, which is one of pure Ni, nickel-based 718, or nickel-based 625 powder, and the particle size range is preferably 15~45 μm, such as 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, or 45μm. In some embodiments of the present invention, the transition layer powder and the injection layer powder are the same powder. During the cold spraying process to prepare the transition layer, both the main gas and the carrier gas are nitrogen or helium. The spraying temperature is preferably 600~950℃, for example, 600℃, 700℃, 800℃, 900℃, or 950℃. The spraying pressure is preferably 3~5 MPa, for example, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, or 5 MPa. The spraying distance is preferably 20~100 mm, for example, 20mm, 30mm, 50mm, 60mm, 70mm, 80mm, 90mm, or 100mm. The gun travel speed is preferably 40~100 mm / min, for example, 40mm / min, 50mm / min, 60mm / min, 70mm / min, 80mm / min, 90mm / min, or 100mm / min. The powder feeding rate is preferably 20~30... The laser speed is preferably 200~500 W, for example, 20 g / min, 22 g / min, 25 g / min, 28 g / min, or 30 g / min. During the post-processing of the transition layer using laser diffusion technology, the laser power is preferably 200~500 W, for example, 200W, 300W, 400W, 450W, or 500W. The scanning speed is preferably 250~500 mm / min, for example, 250mm / min, 300mm / min, 350mm / min, 400mm / min, 450mm / min, or 500mm / min. The lateral moving distance is preferably 1.5~2 mm, for example, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, or 2.0mm.

[0030] Step 4: Prepare a wear-resistant coating using ultra-high-speed laser cladding technology. The alloy-coated powder is clad onto the surface of the transition layer to obtain a wear-resistant coating with a preferred thickness of 0.7–1.2 mm, such as 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, or 1.2 mm. The alloy-coated powder is spherical and is either iron-based alloy-coated ceramic powder or cobalt-based alloy-coated ceramic powder. The preferred particle size range is 50–120 μm, such as 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, or 120 μm. The preferred mass percentage of the ceramic phase in the alloy-coated powder is 20%–50%, such as 20%, 30%, 35%, 38%, 40%, 45%, or 50%. In the process of preparing wear-resistant coatings by ultra-high-speed laser cladding, both the powder feeding gas and the protective gas are argon. The laser power is preferably 1.8~3.0 kW, for example, 1.8kW, 2.1kW, 2.4kW, 2.5kW, 2.8kW, or 3.0kW. The scanning speed is preferably 500~1000 mm / min. The lateral movement distance is preferably 1.2~2.5 mm, for example, 1.2mm, 1.5mm, 1.8mm, 2.0mm, 2.4mm, or 2.5mm. The powder feeding rate is preferably 25~50 g / min, for example, 25 g / min, 30 g / min, 35 g / min, 38 g / min, 40 g / min, 45 g / min, or 50 g / min. The protective gas flow rate is preferably 16~20 L / min, for example, 16 L / min, 17 L / min, 18 L / min, 19 L / min, or 20 L / min.

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof: Example 1

[0032] This embodiment uses ZL101 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL101 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 200 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: Use polygonal pure Ni powder with a particle size range of 50~70 μm to prepare a supersonic gas-powered injection layer with a thickness of 0.05 mm. The supersonic gas-powered injection gas is air, the operating temperature is 50℃, the operating pressure is 4 MPa, the operating distance is 30 mm, the operating speed is 1000 mm / min, and the powder feeding rate is 5 g / min. Step 3: Prepare a cold-sprayed transition layer using spherical pure Ni powder with a particle size range of 30~45 μm. The transition layer thickness is 0.5 mm. The main gas and carrier gas for cold spraying are nitrogen. The spraying temperature is 600 ℃, the spraying pressure is 5 MPa, the spraying distance is 20 mm, the gun speed is 40 mm / min, and the powder feed rate is 20 g / min. The cold-sprayed transition layer is then subjected to laser diffusion treatment with a laser power of 200 W, a scanning speed of 250 mm / min, and a lateral movement distance of 1.5 mm. Step 4: Coat WC powder with spherical 304 stainless steel with a particle size range of 50~80 μm, wherein the WC content is 40%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 1.8 kW, the scanning speed is 500 mm / min, the lateral movement distance is 1.2 mm, the powder feeding rate is 25 g / min, the protective gas flow rate is 16 L / min, and the thickness of the prepared wear-resistant coating is 0.7 mm.

[0033] Figure 1 The microstructure of the gradient coating section on the aluminum alloy surface in this embodiment shows that the injection layer and the transition layer are completely fused, there are no pores or interparticle interfaces in the transition layer, and there are no defects such as pores or cracks in the cladding layer. Figure 2 The hardness curve of the gradient coating section on the aluminum alloy surface in this embodiment shows that the average hardness of the substrate is 243.35 HV. 0.2 The wear-resistant coating has an average hardness of 576.23 HV. 0.2 The hardness of the wear-resistant coating is significantly improved compared to the substrate; Figure 3 The figures show the friction coefficient curves of the aluminum alloy substrate and the wear-resistant coating in this embodiment. The average friction coefficient of the aluminum alloy substrate is 0.29, and the wear amount is 4.3 mg. The average friction coefficient of the wear-resistant coating is 0.36, and the wear amount is 0.53 mg. The wear-resistant coating can effectively protect the aluminum alloy substrate.

[0034] Example 2 This embodiment uses ZL104 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL104 cast aluminum alloy surface. The milling cutter speed is 1800 rpm and the feed rate is 100 mm / min. The surface roughness after machining is Ra 6.3. Step 2: A supersonic gas-powered injection layer is prepared using polygonal nickel-based 718 powder with a particle size range of 70~100 μm. The injection layer thickness is 0.09 mm. The supersonic gas-powered injection operation gas is air, the operating temperature is 100 ℃, the operating pressure is 5 MPa, the operating distance is 10 mm, the operating speed is 500 mm / min, and the powder feeding rate is 20 g / min. Step 3: Prepare a cold-sprayed transition layer using spherical nickel-based 718 powder with a particle size range of 15~30 μm. The transition layer thickness is 0.8 mm. The main gas and carrier gas for cold spraying are nitrogen. The spraying temperature is 950 ℃, the spraying pressure is 3 MPa, the spraying distance is 100 mm, the gun speed is 100 mm / min, and the powder feed rate is 30 g / min. The cold-sprayed transition layer is then subjected to laser diffusion treatment with a laser power of 500 W, a scanning speed of 500 mm / min, and a lateral movement distance of 2.0 mm. Step 4: Coat SiC powder with spherical Co01 stainless steel with a particle size range of 80~120 μm, wherein the SiC content is 20%. The powder feeding gas and protective gas for ultra-high speed laser cladding of the wear-resistant coating are argon. The laser power is 3.0kW, the scanning speed is 1000 mm / min, the lateral movement distance is 2.5 mm, the powder feeding rate is 50g / min, the protective gas flow rate is 20 L / min, and the thickness of the prepared wear-resistant coating is 1.2 mm.

[0035] Testing revealed that the transition layer in this embodiment was free of pores and interparticle interfaces, while the cladding layer was free of pores and cracks. The average hardness of the substrate was 121.96 HV. 0.2 The average coefficient of friction is 0.48, and the wear amount is 5.9 mg. The average hardness of the wear-resistant coating is 605.63 HV. 0.2 The average coefficient of friction is 0.51, and the wear amount is 0.26 mg. The wear-resistant coating can effectively protect the substrate. Example 3

[0036] This embodiment uses ZL107 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL107 cast aluminum alloy surface. The milling cutter speed is 1500 rpm and the feed rate is 120 mm / min. The surface roughness after machining is Ra 6.3. Step 2: A supersonic gas-powered injection layer is prepared using polygonal nickel-based 625 powder with a particle size range of 60~90 μm. The injection layer thickness is 0.08 mm. The supersonic gas-powered injection gas is air, the operating temperature is 80℃, the operating pressure is 4.5 MPa, the operating distance is 20 mm, the operating speed is 600 mm / min, and the powder feeding rate is 15 g / min. Step 3: A cold-sprayed transition layer is prepared using spherical nickel-based 625 powder with a particle size range of 15~45 μm. The transition layer thickness is 0.6 mm. Nitrogen is used as the main gas and carrier gas for cold spraying. The spraying temperature is 900 ℃, the spraying pressure is 4.5 MPa, the spraying distance is 80 mm, the gun speed is 60 mm / min, and the powder feed rate is 25 g / min. The cold-sprayed transition layer is then subjected to laser diffusion treatment with a laser power of 300 W, a scanning speed of 400 mm / min, and a lateral movement distance of 1.8 mm. Step 4: Coat TiC powder with spherical 316 stainless steel with a particle size range of 60~100 μm, wherein the TiC content is 50%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 2.5 kW, the scanning speed is 800 mm / min, the lateral movement distance is 2.0 mm, the powder feeding rate is 30 g / min, the protective gas flow rate is 18 L / min, and the thickness of the prepared wear-resistant coating is 1.0 mm.

[0037] Testing revealed no pores or interparticle interfaces within the transition layer, and no pores or cracks within the cladding layer. The average hardness of the substrate was 233.45 HV. 0.2 The average coefficient of friction is 0.41, and the wear amount is 3.1 mg. The average hardness of the wear-resistant coating is 553.81 HV. 0.2 With an average friction coefficient of 0.47 and a wear amount of 0.56 mg, the wear-resistant coating can effectively protect the substrate.

[0038] Example 4 This embodiment uses ZL201 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL101 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 150 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: A supersonic gas-powered injection layer is prepared using polygonal pure Ni powder with a particle size range of 50~80 μm. The injection layer thickness is 0.07 mm. The supersonic gas-powered injection gas is air, the operating temperature is 70 ℃, the operating pressure is 4.2 MPa, the operating distance is 15 mm, the operating speed is 700 mm / min, and the powder feeding rate is 13 g / min. Step 3: A cold-sprayed transition layer is prepared using spherical pure Ni powder with a particle size range of 15~40 μm. The transition layer thickness is 0.7 mm. Nitrogen is used as the main gas and carrier gas for cold spraying. The spraying temperature is 700 ℃, the spraying pressure is 3.5 MPa, the spraying distance is 60 mm, the gun speed is 70 mm / min, and the powder feed rate is 28 g / min. The cold-sprayed transition layer is then subjected to laser diffusion treatment with a laser power of 350 W, a scanning speed of 450 mm / min, and a lateral movement distance of 1.7 mm. Step 4: Coat WC powder with spherical CoO2 particles with a particle size range of 50~90 μm, wherein the WC content is 45%. The powder feeding gas and protective gas for ultra-high speed laser cladding of the wear-resistant coating are argon. The laser power is 2.8 kW, the scanning speed is 900 mm / min, the lateral movement distance is 2.4 mm, the powder feeding rate is 35 g / min, the protective gas flow rate is 19 L / min, and the thickness of the prepared wear-resistant coating is 1.1 mm.

[0039] Testing revealed no pores or interparticle interfaces within the transition layer, and no pores or cracks within the cladding layer. The average hardness of the substrate was 191.68 HV. 0.2 The average coefficient of friction is 0.49, and the wear amount is 4.2 mg. The average hardness of the wear-resistant coating is 627.39 HV. 0.2 With an average friction coefficient of 0.47 and a wear amount of 0.24 mg, the wear-resistant coating can effectively protect the substrate.

[0040] Example 5 This embodiment uses ZL305 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL305 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 110 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: A supersonic gas-powered injection layer was prepared using polygonal nickel-based 718 powder with a particle size range of 50~80 μm. The injection layer thickness was 0.07 mm. The supersonic gas-powered injection operating gas was air, the operating temperature was 75 ℃, the operating pressure was 4.8 MPa, the operating distance was 185 mm, the operating speed was 800 mm / min, and the powder feeding rate was 11 g / min. Step 3: Prepare a cold-sprayed transition layer using spherical pure Ni powder with a particle size range of 20~45 μm. The transition layer thickness is 0.6 mm. The main gas and carrier gas for cold spraying are nitrogen. The spraying temperature is 650 ℃, the spraying pressure is 4.5 MPa, the spraying distance is 30 mm, the gun speed is 50 mm / min, and the powder feed rate is 22 g / min. The cold-sprayed transition layer is then subjected to laser diffusion treatment with a laser power of 450 W, a scanning speed of 350 mm / min, and a lateral movement distance of 1.8 mm. Step 4: Coat SiC powder with spherical 430 stainless steel with a particle size range of 50~90 μm, wherein the SiC content is 35%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 2.4 kW, the scanning speed is 600 mm / min, the lateral movement distance is 1.8 mm, the powder feeding rate is 38 g / min, the protective gas flow rate is 17 L / min, and the thickness of the prepared wear-resistant coating is 1.0 mm.

[0041] Testing revealed no pores or interparticle interfaces within the transition layer, and no pores or cracks within the cladding layer. The average hardness of the substrate was 93.61 HV. 0.2 The average coefficient of friction is 0.56, and the wear amount is 6.3 mg. The average hardness of the wear-resistant coating is 582.43 HV. 0.2 The average coefficient of friction is 0.41, and the wear amount is 0.58 mg. The wear-resistant coating can effectively protect the substrate.

[0042] Example 6 This embodiment uses ZL401 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL401 cast aluminum alloy surface. The milling cutter speed is 1800 rpm, the feed rate is 200 mm / min, and the surface roughness after machining is Ra 6.3. Step 2: A supersonic gas-powered injection layer is prepared using polygonal nickel-based 718 powder with a particle size range of 60~95 ​​μm. The injection layer thickness is 0.08 mm. The supersonic gas-powered injection gas is air, the operating temperature is 85℃, the operating pressure is 4.3 MPa, the operating distance is 25 mm, the operating speed is 900 mm / min, and the powder feeding rate is 8 g / min. Step 3: A cold-sprayed transition layer was prepared using spherical nickel-based 625 powder with a particle size range of 20~40 μm. The transition layer thickness was 0.7 mm. Nitrogen was used as the main gas and carrier gas for cold spraying. The spraying temperature was 850 ℃, the spraying pressure was 4.5 MPa, the spraying distance was 50 mm, the gun speed was 60 mm / min, and the powder feed rate was 29 g / min. The cold-sprayed transition layer was then subjected to laser diffusion treatment with a laser power of 350 W, a scanning speed of 450 mm / min, and a lateral movement distance of 1.9 mm. Step 4: Coat TiC powder with spherical CoO3 particles with a particle size range of 60~100 μm, wherein the percentage content of TiC is 38%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 2.7 kW, the scanning speed is 750 mm / min, the lateral movement distance is 2.1 mm, the powder feeding rate is 42 g / min, the protective gas flow rate is 16 L / min, and the thickness of the prepared wear-resistant coating is 1.1 mm.

[0043] Testing revealed no pores or interparticle interfaces within the transition layer, and no pores or cracks within the cladding layer. The average hardness of the substrate was 203.46 HV. 0.2 The average coefficient of friction is 0.43, and the wear amount is 4.5 mg. The average hardness of the wear-resistant coating is 658.23 HV. 0.2 With an average friction coefficient of 0.52 and a wear amount of 0.23 mg, the wear-resistant coating can effectively protect the substrate.

[0044] Comparative Example 1 This comparative example uses ZL101 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL101 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 200 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: Use polygonal pure Ni powder with a particle size range of 50~70 μm to prepare a supersonic gas-powered injection layer with a thickness of 0.05 mm. The supersonic gas-powered injection gas is air, the operating temperature is 50℃, the operating pressure is 4 MPa, the operating distance is 30 mm, the operating speed is 1000 mm / min, and the powder feeding rate is 5 g / min. Step 3: Perform laser diffusion treatment on the injection layer. The laser power is 200 W, the scanning speed is 250 mm / min, and the lateral movement distance is 1.5 mm. Step 4: Coat WC powder with spherical 304 stainless steel with a particle size range of 50~80 μm, wherein the WC content is 40%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 1.8 kW, the scanning speed is 500 mm / min, the lateral movement distance is 1.2 mm, the powder feeding rate is 25 g / min, the protective gas flow rate is 16 L / min, and the thickness of the prepared wear-resistant coating is 0.7 mm.

[0045] Compared with Example 1, this comparative example did not use cold spraying technology to prepare the transition layer, which resulted in the inability to effectively form a laser cladding wear-resistant coating on the surface of ZL101 cast aluminum alloy, and severe ablation occurred on the surface of the aluminum alloy.

[0046] Comparative Example 2 This embodiment uses ZL101 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL101 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 200 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: Use polygonal pure Ni powder with a particle size range of 50~70 μm to prepare a supersonic gas-powered injection layer with a thickness of 0.05 mm. The supersonic gas-powered injection gas is air, the operating temperature is 50℃, the operating pressure is 4 MPa, the operating distance is 30 mm, the operating speed is 1000 mm / min, and the powder feeding rate is 5 g / min. Step 3: Prepare a cold spray transition layer using spherical pure Ni powder with a particle size range of 30~45 μm. The transition layer thickness is 0.5 mm. The main gas and carrier gas for cold spraying are nitrogen. The spraying temperature is 600 ℃, the spraying pressure is 5 MPa, the spraying distance is 20 mm, the gun speed is 40 mm / min, and the powder feeding rate is 20 g / min. Step 4: Coat WC powder with spherical 304 stainless steel with a particle size range of 50~80 μm, wherein the WC content is 40%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 1.8 kW, the scanning speed is 500 mm / min, the lateral movement distance is 1.2 mm, the powder feeding rate is 25 g / min, the protective gas flow rate is 16 L / min, and the thickness of the prepared wear-resistant coating is 0.7 mm.

[0047] Compared to Example 1, this comparative example did not use laser diffusion technology to post-process the transition layer, resulting in a large number of pores at the interface between the coating and the substrate on the surface of the ZL101 cast aluminum alloy and within the cold spray transition layer.

[0048] Comparative Example 3 This comparative example uses ZL101 cast aluminum alloy, and a wear-resistant coating is prepared on its surface using a composite gradient process, including the following steps: Step 1: Use a milling machine to mill along the X and Y directions of the ZL101 cast aluminum alloy surface. The milling cutter speed is 1200 rpm, the feed rate is 200 mm / min, and the surface roughness after machining is Ra 12.5. Step 2: Use polygonal pure Ni powder with a particle size range of 50~70 μm to prepare a supersonic gas-powered injection layer with a thickness of 0.05 mm. The supersonic gas-powered injection gas is air, the operating temperature is 50℃, the operating pressure is 4 MPa, the operating distance is 30 mm, the operating speed is 1000 mm / min, and the powder feeding rate is 5 g / min. Step 3: Prepare a cold spray transition layer using spherical pure Ni powder with a particle size range of 30~45 μm. The transition layer thickness is 1.0 mm. The main gas and carrier gas for cold spraying are nitrogen. The spraying temperature is 600 ℃, the spraying pressure is 5 MPa, the spraying distance is 20 mm, the gun speed is 40 mm / min, and the powder feeding rate is 20 g / min. Step 4: Coat WC powder with spherical 304 stainless steel with a particle size range of 50~80 μm, wherein the WC content is 40%. The powder feeding gas and protective gas for ultra-high speed laser cladding of wear-resistant coating are argon. The laser power is 1.8 kW, the scanning speed is 500 mm / min, the lateral movement distance is 1.2 mm, the powder feeding rate is 25 g / min, the protective gas flow rate is 16 L / min, and the thickness of the prepared wear-resistant coating is 0.7 mm.

[0049] Compared to Example 1, the thickness of the cold spraying process in this comparative example exceeds 0.8 mm, reaching 1.0 mm. This results in a large number of pores and interparticle interfaces remaining at the bottom of the cold spraying transition layer on the ZL101 cast aluminum alloy surface after laser diffusion treatment, which negatively affects the bonding strength of the protective layer.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface, characterized in that, Includes the following steps: Step 1: Pre-treat the aluminum alloy surface by using a milling machine to perform milling along the X and Y directions of the aluminum alloy surface. Step 2: The injection layer is prepared using supersonic gas dynamic injection technology. The injection layer powder is injected onto the pretreated aluminum alloy surface to obtain an injection layer with a thickness of 0.05~0.09mm. The injection layer powder is a polygonal powder, which is one of pure Ni, nickel-based 718 or nickel-based 625 powder, with a particle size range of 50~100 μm. Step 3: A transition layer is prepared using cold spraying technology. The transition layer powder is prepared on the surface of the injection layer to obtain a transition layer with a thickness of 0.5~0.8mm. The transition layer is then post-processed using laser diffusion technology. The transition layer powder is a spherical powder, which is one of pure Ni, nickel-based 718 or nickel-based 625 powder, with a particle size range of 15~45 μm. Step 4: Prepare a wear-resistant coating using ultra-high-speed laser cladding technology. Fuse alloy-coated powder onto the surface of the transition layer to obtain a wear-resistant coating with a thickness of 0.7~1.2 mm. The alloy-coated powder is spherical powder, which is iron-based alloy-coated ceramic powder or cobalt-based alloy-coated ceramic powder, with a particle size range of 50~120 μm.

2. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, The aluminum alloy is one of ZL101, ZL104, ZL107, ZL201, ZL305 or ZL401 cast aluminum alloys.

3. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, The surface roughness of the aluminum alloy surface after milling in step one is Ra6.3~Ra12.

5.

4. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 3, characterized in that, During the milling process, the milling cutter speed is 1200~1800 rpm and the feed rate is 100~200 mm / min.

5. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, In step two, during the preparation of the injection layer using supersonic gas dynamic injection technology, the supersonic operating gas is air, the operating temperature is 50~100 ℃, the operating pressure is 4~5 MPa, the operating distance is 10~30 mm, the operating speed is 500~1000 mm / min, and the powder feeding rate is 5~20 g / min.

6. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, In step three, during the cold spraying process for preparing the transition layer, both the main gas and the carrier gas are nitrogen or helium. The spraying temperature is 600~950 ℃, the spraying pressure is 3~5 MPa, the spraying distance is 20~100 mm, the gun speed is 40~100 mm / min, and the powder feeding rate is 20~30 g / min.

7. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, In step three, during the post-processing of the transition layer using laser diffusion technology, the laser power is 200-500 W, the scanning speed is 250-500 mm / min, and the lateral movement distance is 1.5-2 mm.

8. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, In the process of preparing wear-resistant coating by ultra-high speed laser cladding described in step four, both the powder feeding gas and the protective gas are argon, the laser power is 1.8~3.0 kW, the scanning speed is 500~1000 mm / min, the lateral movement distance is 1.2~2.5 mm, the powder feeding rate is 25~50 g / min, and the protective gas flow rate is 16~20 L / min.

9. The method for preparing a composite gradient wear-resistant coating on an aluminum alloy surface according to claim 1, characterized in that, The mass percentage of ceramic phase in the alloy-coated powder described in step four is 20% to 50%.

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