Preparation method of ultra-white oxidation coating on surface of 3D printing AlSi10Mg alloy part

Abstract

The invention discloses a preparation method of an ultra-white oxidation coating on the surface of a 3D printed AlSi10Mg alloy part, which comprises the following steps: primary machining: reducing a three-dimensional model of a required workpiece in equal proportion, and processing the 3D printed AlSi10Mg alloy part by taking the reduced three-dimensional model as a reference; primary sand blasting: carrying out primary sand blasting treatment on the workpiece subjected to primary machining; cold spraying is conducted, specifically, cold spraying treatment is conducted on the workpiece subjected to primary sand blasting, and then isopropyl alcohol is sprayed; secondary machining is conducted, specifically, secondary machining is conducted on the sprayed printing piece with the three-dimensional model of the needed workpiece as the benchmark; secondary sand blasting is conducted, specifically, the workpiece subjected to secondary machining is subjected to sand blasting treatment, and gravel obtained after secondary sand blasting is brown aluminum oxide; after sand blasting is completed, isopropyl alcohol is sprayed; the workpiece subjected to secondary sand blasting is placed in electrolyte, the workpiece subjected to secondary sand blasting serves as an anode, and micro-arc oxidation is conducted in a single-pulse constant-voltage oxidation mode; and post-treatment is conducted, specifically, the workpiece subjected to micro-arc oxidation is rinsed and subjected to heat treatment. Compared with the prior art, the invention has the advantages of high reflectivity and low absorptivity.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, specifically to a method for preparing an ultra-white oxide coating on the surface of a 3D printed AlSi10Mg alloy part. Background Technology

[0002] AlSi10Mg powder is an aluminum alloy powder material used in the manufacture of metal additives. AlSi10Mg powder exhibits excellent performance under selective laser melting (SLM) processes: particle size 15-53 μm, sphericity ≥97%, oxygen content as low as 300 ppm, flowability ≤70 s / 50 g, and loose density ≥1.45 g / cm³. 3 This ensures uniform powder distribution and minimal defects. By optimizing SLM process parameters, including a layer thickness of 30μm, laser power of 350-370W, and a speed of 1200-1300mm / s, formed parts with a density of 99.9% can be obtained. These parts exhibit outstanding mechanical properties: tensile strength ≥440MPa, yield strength ≥245MPa, elongation 6-8%, upper surface roughness Ra ≤2μm, side surface roughness ≤5μm, and dimensional error ±0.1mm. After appropriate heat treatment, while the strength decreases slightly, the elongation and impact toughness are significantly improved. Therefore, the high fluidity, low porosity, and fine-grained structure of AlSi10Mg powder endow it with the ability to rapidly and precisely form complex thin-walled aerospace, automotive, and consumer electronics components.

[0003] In aerospace applications, the absorptivity (α) and reflectivity (ρ) of materials are key optical parameters that determine their thermal control performance. Especially in extreme space environments, they directly affect spacecraft surface temperature control, energy efficiency, and equipment lifespan. Micro-arc oxidation, due to its technological characteristics, reacts in solution and can prepare a uniform thermal control and protective coating on the surface of irregular components. This coating possesses excellent properties such as high emissivity, strong adhesion, corrosion resistance, and simple processing, and has become the mainstream technology for integrated heat dissipation and protection of lightweight alloys in aerospace.

[0004] However, the micro-arc oxide film on the surface of aluminum alloys is usually gray, especially AlSi10Mg alloys with high silicon content. The oxide film prepared by conventional oxidation process is dark gray. The darkening of the oxide film color will lead to a decrease in the emissivity and an increase in the absorptivity of the coating, which is not conducive to the promotion and application of AlSi10Mg in the aerospace field.

[0005] Therefore, improvements are needed to the existing AlSi10Mg. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing an ultra-white oxide coating on the surface of 3D-printed AlSi10Mg alloy parts with high reflectivity and low absorptivity, in light of the above-mentioned technical status.

[0007] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for preparing an ultra-white oxide coating on the surface of a 3D printed AlSi10Mg alloy part, characterized by comprising the following steps:

[0008] ① One-time machining: The three-dimensional model of the required workpiece is scaled down by 0.5-1mm, and the 3D printed AlSi10Mg alloy part is machined based on the scaled-down three-dimensional model; the depth of the one-time machining is 0.5-1mm.

[0009] ② First sandblasting: The workpiece after one machining operation is subjected to a first sandblasting treatment; the sand used for sandblasting is one or a mixture of quartz sand, brown corundum or white corundum;

[0010] ③ Cold spraying: The workpiece after sandblasting is subjected to cold spraying treatment. The powder used for cold spraying is composed of 5-10% magnesium powder, 0.5-1% boron oxide, and the balance is aluminum powder by weight percentage. The spraying gas used for cold spraying is high-purity nitrogen, the spraying pressure is 0.8-1.5 MPa, the preheating temperature is 250-350℃, and the spraying distance is 15-30 mm. After cold spraying, isopropanol is then sprayed.

[0011] ④ Secondary machining: Based on the three-dimensional model of the required workpiece, secondary machining is performed on the printed part after spraying. The depth of the secondary machining is 0.5-0.6mm.

[0012] ⑤ Secondary sandblasting: The workpiece that has been machined twice is sandblasted, and the sand used in the secondary sandblasting is brown corundum; after sandblasting, isopropyl alcohol is sprayed on.

[0013] ⑥ Micro-arc oxidation: The workpiece that has been sandblasted twice is placed in an electrolyte, with the workpiece being sandblasted twice as the anode. Micro-arc oxidation is carried out in a single-pulse constant voltage oxidation mode under the conditions of voltage 500-700V, frequency 1000-4000Hz, and duty cycle 30-45%; the micro-arc oxidation time is 20-30min.

[0014] ⑦ Post-treatment: Rinse and heat treat the workpiece after micro-arc oxidation.

[0015] To increase the α-Al₂O₃ content in the oxide film and improve its stability through heat treatment, the post-treatment preferably includes the following steps:

[0016] S1, First rinse;

[0017] S2. Heat treatment: Perform multiple cycles of heat treatment. Each cycle is as follows: After the first rinse, the workpiece is held at 200-250℃ for 1-3 minutes, then the workpiece is ignited with an acetylene flame at 1800-2000℃. After that, the workpiece is cooled in an atmosphere at 200-250℃ and held at 1-3 minutes after cooling.

[0018] S3, Second rinse.

[0019] Preferably, the heat treatment is a three-cycle heat treatment.

[0020] Preferably, the first rinsing is: rinsing the workpiece again in a water glass solution at a temperature of 80-95℃ for 60-90 seconds and then drying it, wherein the sodium silicate content of the water glass solution is 1-3g / L;

[0021] The second rinsing step involves rinsing the heat-treated workpiece in deionized water at 70-85℃ for 180-300 seconds, followed by air drying. The first rinsing step, with its high temperature, serves to seal pores; the second rinsing step removes surface impurities.

[0022] Preferably, the depth of the first machining step is 0.5-1 mm; the depth of the second machining step is 0.5-0.6 mm. The depth of the first machining step is positively correlated with the thickness of the cold spray coating, ensuring that the dimensions of the workpiece produced by this invention are the same as the required workpiece dimensions.

[0023] Preferably, the nitrogen used in both the cold spraying and the secondary sandblasting is nitrogen with a purity of 99.99% or higher.

[0024] Preferably, the electrolyte in step ⑥ comprises the following components by weight: 2-5% sodium hexametaphosphate, 10-20% sodium borate, 1-2% sodium hydroxide, 0.05-0.2% nano boron oxide, and the balance being deionized water.

[0025] Preferably, the cathode for micro-arc oxidation in step ⑥ is one or more of graphite plate and stainless steel.

[0026] Preferably, in step ②, the gravel particle size is 10-40 mesh, the gas used is compressed air with a pressure of 6-6.5 MPa, the distance between the nozzle and the sandblasting surface is 5-15 cm, and the sandblasting time per unit nozzle area is 1-2 s.

[0027] Preferably, the gravel particle size in step ⑤ is 80-100 mesh, the sandblasting gas is compressed high-purity nitrogen gas with a pressure of 5.5-6 MPa, the distance between the nozzle and the sandblasting surface is 5-10 cm, and the sandblasting time per unit nozzle area is 0.5-1 s.

[0028] In step ③, the spraying gas for cold spraying is high-purity nitrogen, the spraying pressure is 0.8-1.5 MPa, the preheating temperature is 250-350℃, and the spraying distance is 15-30 mm.

[0029] Preferably, the preparation method of the cold spray powder in step ③ is as follows: aluminum powder, nano-boron oxide particles, and magnesium powder are sequentially placed into a sealed container, then anhydrous ethanol is added to the sealed container and nitrogen gas is injected; the powder is mixed evenly by rotating the container, and after mixing, the metal particles are allowed to settle naturally. The supernatant is then removed, and the lower solid-liquid mixture is the desired cold spray powder. The particle size range of the aluminum and magnesium powders is 10-30 μm, and the particle size of the boron oxide is 50-100 nm. The thickness of the cold spray is 1-1.5 mm.

[0030] Compared with the prior art, the advantages of the present invention are as follows:

[0031] 1. Cold spraying produces an aluminum-magnesium alloy coating that effectively isolates the substrate from contact with the micro-arc oxidation electrolyte, thereby blocking silicon elements in the workpiece substrate from participating in the oxidation reaction. This process prepares a high-purity aluminum oxide and magnesium oxide composite ceramic coating, improves the whiteness of the oxide film, and results in a coating with high reflectivity and low absorptivity, thereby enhancing the thermal control and protection performance of the alloy parts.

[0032] 2. Two machining operations and two sandblasting operations were performed to achieve precise control over the surface roughness of the 3D printed parts, improve the bonding state between the cold spray and micro-arc oxidation coatings and the substrate, and enhance the coating adhesion.

[0033] 3. Brown fused alumina is used for secondary sandblasting. As an alumina grit, brown fused alumina can reduce the contamination of silicon elements on the workpiece surface, reduce the influence of silicon elements on the coating color, improve reflectivity and reduce absorption rate.

[0034] 4. Cold spraying and secondary sandblasting are both thickly coated with isopropanol, which effectively inhibits the oxidation of magnesium powder, reduces the impact of loose magnesium oxide on the density of the coating, prevents the new substrate surface after sandblasting from contacting air and oxidizing, and reduces the adhesion of the oxide film in the later stage. In addition, the residual isopropanol on the surface is a discharge inhibitor of micro-arc oxidation, which can be utilized and consumed in the next process, and reduces the probability of disordered discharge on the workpiece surface during the high voltage and high current stage in the early stage of oxidation, thus improving the quality of the oxide film. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the emissivity and absorptivity tests for an example. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0038] Example 1

[0039] A method for preparing an ultra-white oxide coating on the surface of a 3D-printed AlSi10Mg alloy part includes the following steps:

[0040] ① One-time machining: The three-dimensional model of the required workpiece is scaled down by 0.5mm, and the 3D printed AlSi10Mg alloy part is machined based on the scaled-down three-dimensional model; the depth of the one-time machining is 0.5mm.

[0041] ② First sandblasting: The workpiece after one machining is subjected to the first sandblasting treatment; the sand for sandblasting is one or a mixture of quartz sand, brown corundum or white corundum; the sand particle size is 10 mesh, the gas used is compressed air, the pressure is 6 MPa, the distance between the nozzle and the sandblasting surface is 5 cm, and the sandblasting time per unit nozzle area is 1 second.

[0042] ③ Cold Spraying: The workpiece after sandblasting is subjected to cold spraying. The cold spray powder, by weight percentage, consists of 5% magnesium powder, 0.5% boron oxide, and the remainder is aluminum powder. The spraying gas is high-purity nitrogen, the spraying pressure is 0.8 MPa, the preheating temperature is 250℃, and the spraying distance is 15 mm. After cold spraying, isopropanol is sprayed. The preparation method of the cold spray powder is as follows: aluminum powder, nano-boron oxide particles, and magnesium powder are placed in a sealed container in sequence. Then, anhydrous ethanol is added to the sealed container, and nitrogen is injected. The powder is mixed evenly by rotating the container. After mixing, the metal particles are allowed to settle naturally. The supernatant is then removed, and the lower solid-liquid mixture is the required cold spray powder. The particle size range of aluminum powder and magnesium powder is 10 μm, and the particle size of boron oxide is 50 nm. The thickness of the cold spray is 1 mm.

[0043] ④ Secondary machining: Based on the three-dimensional model of the required workpiece, the printed part after spraying is subjected to secondary machining, and the depth of the secondary machining is 0.5mm.

[0044] ⑤ Secondary sandblasting: The workpiece undergoing secondary machining is sandblasted, and the sand used in the secondary sandblasting is brown corundum. After sandblasting, isopropyl alcohol is sprayed on. The nitrogen used in both the cold spraying and the secondary sandblasting is nitrogen with a purity of ≥99.99%. The sand particle size is 80 mesh. The sandblasting gas is compressed high-purity nitrogen with a gas pressure of 5.5 MPa. The distance between the nozzle and the sandblasting surface is 5 cm, and the sandblasting time per unit nozzle area is 0.5 s.

[0045] ⑥ Micro-arc oxidation: The workpiece that has undergone secondary sandblasting is placed in an electrolyte, with the workpiece as the anode and one or more of graphite plate and stainless steel as the cathode; a single-pulse constant voltage oxidation mode is used, and micro-arc oxidation is performed under the conditions of 500V voltage, 1000Hz frequency, and 30% duty cycle; the micro-arc oxidation time is 20min; the electrolyte includes the following components by weight: 2% sodium hexametaphosphate, 10% sodium borate, 1% sodium hydroxide, 0.05% nano boron oxide, and the balance is deionized water.

[0046] ⑦ Post-treatment: Rinse and heat treat the workpiece after micro-arc oxidation. Post-treatment includes the following steps:

[0047] S1. First rinse: Rinse the workpiece again in a water glass solution at 80℃ for 60 seconds and then air dry naturally. The sodium silicate content of the water glass solution is 1g / L.

[0048] S2. Heat treatment: Perform three cycles of heat treatment. Each cycle is as follows: After the first rinse, the workpiece is held at 200-250℃ for 1 minute, then the workpiece is ignited with an acetylene flame at 1800℃, and then the workpiece is cooled in an atmosphere of 200-250℃ and held at 1 minute after cooling.

[0049] S3. Second rinse: Rinse the heat-treated workpiece in deionized water at 70℃ for 180 seconds and then air dry naturally.

[0050] Example 2

[0051] A method for preparing an ultra-white oxide coating on the surface of a 3D-printed AlSi10Mg alloy part includes the following steps:

[0052] ① One-time machining: The three-dimensional model of the required workpiece is scaled down by 0.75mm, and the 3D printed AlSi10Mg alloy part is machined based on the scaled-down three-dimensional model; the depth of the one-time machining is 0.75mm.

[0053] ② First sandblasting: The workpiece after one machining is subjected to the first sandblasting treatment; the sand for sandblasting is one or a mixture of quartz sand, brown corundum or white corundum; the sand particle size is 25 mesh, the gas used is compressed air, the pressure is 6.25 MPa, the distance between the nozzle and the sandblasting surface is 10 cm, and the sandblasting time per unit nozzle area is 1.5 s.

[0054] ③ Cold spraying: The workpiece after sandblasting is subjected to cold spraying. The cold spray powder, by weight percentage, consists of 7.5% magnesium powder, 0.75% boron oxide, and the remainder is aluminum powder. The spraying gas is high-purity nitrogen, the spraying pressure is 1.2 MPa, the preheating temperature is 300℃, and the spraying distance is 22.5 mm. After cold spraying, isopropanol is sprayed. The preparation method of the cold spray powder is as follows: aluminum powder, nano-boron oxide particles, and magnesium powder are placed in a sealed container in sequence. Then, anhydrous ethanol is added to the sealed container, and nitrogen is injected. The powder is mixed evenly by rotating the container. After mixing, the metal particles are allowed to settle naturally. Then, the supernatant is removed, and the lower solid-liquid mixture is the required cold spray powder. The particle size range of aluminum powder and magnesium powder is 20 μm, and the particle size of boron oxide is 75 nm. The thickness of the cold spray is 1.25 mm.

[0055] ④ Secondary machining: Based on the three-dimensional model of the required workpiece, the printed part after spraying is subjected to secondary machining, and the depth of the secondary machining is 0.5mm.

[0056] ⑤ Secondary sandblasting: The workpiece undergoing secondary machining is sandblasted, and the sand used in the secondary sandblasting is brown corundum. After sandblasting, isopropyl alcohol is sprayed on. The nitrogen used for both the cold spraying and the secondary sandblasting is nitrogen with a purity of ≥99.99%. The sand particle size is 90 mesh, the sandblasting gas is compressed nitrogen with a purity ≥99.99%, the gas pressure is 5.75 MPa, the distance between the nozzle and the sandblasting surface is 7.5 cm, and the sandblasting time per unit nozzle area is 0.75 s.

[0057] ⑥ Micro-arc oxidation: The workpiece that has undergone secondary sandblasting is placed in an electrolyte, with the workpiece being the anode and the cathode being one or more of graphite plate and stainless steel; a single-pulse constant voltage oxidation mode is used, with micro-arc oxidation under the conditions of 600V, 2500Hz, and 37.5% duty cycle; the micro-arc oxidation time is 25min; the electrolyte includes the following components by weight: 3.5% sodium hexametaphosphate, 15% sodium borate, 1.5% sodium hydroxide, 0.1% nano boron oxide, and the balance being deionized water.

[0058] ⑦ Post-treatment: Rinse and heat treat the workpiece after micro-arc oxidation. Post-treatment includes the following steps:

[0059] S1. First rinse: Rinse the workpiece again in a water glass solution at 90℃ for 75 seconds and then air dry naturally. The sodium silicate content of the water glass solution is 2g / L.

[0060] S2. Heat treatment: Perform three cycles of heat treatment. Each cycle is as follows: After the first rinse, the workpiece is held at 225℃ for 2 minutes, then ignited with an acetylene flame at 1900℃, and then cooled in an atmosphere at 225℃. After cooling, the workpiece is held at 2 minutes.

[0061] S3. Second rinse: Rinse the heat-treated workpiece in deionized water at 80℃ for 250 seconds and then air dry naturally.

[0062] Example 3

[0063] A method for preparing an ultra-white oxide coating on the surface of a 3D-printed AlSi10Mg alloy part includes the following steps:

[0064] ① One-time machining: The three-dimensional model of the required workpiece is scaled down by 1mm, and the 3D printed AlSi10Mg alloy part is machined based on the scaled-down three-dimensional model; the depth of the one-time machining is 1mm.

[0065] ② First sandblasting: The workpiece after one machining is subjected to the first sandblasting treatment; the sand for sandblasting is one or a mixture of quartz sand, brown corundum or white corundum; the sand particle size is 40 mesh, the gas used is compressed air, the pressure is 6.5 MPa, the distance between the nozzle and the sandblasting surface is 15 cm, and the sandblasting time per unit nozzle area is 2 s.

[0066] ③ Cold spraying: The workpiece after sandblasting is subjected to cold spraying. The cold spray powder, by weight percentage, consists of 10% magnesium powder, 1% boron oxide, and the remainder is aluminum powder. The spraying gas is high-purity nitrogen, the spraying pressure is 1.5 MPa, the preheating temperature is 350℃, and the spraying distance is 30 mm. After cold spraying, isopropanol is sprayed. The preparation method of the cold spray powder is as follows: aluminum powder, nano-boron oxide particles, and magnesium powder are placed in a sealed container in sequence. Then, anhydrous ethanol is added to the sealed container, and nitrogen is injected. The powder is mixed evenly by rotating the container. After mixing, the metal particles are allowed to settle naturally. The supernatant is then removed, and the lower solid-liquid mixture is the required cold spray powder. The particle size range of aluminum powder and magnesium powder is 30 μm, and the particle size of boron oxide is 100 nm. The thickness of the cold spray is 1.5 mm.

[0067] ④ Secondary machining: Based on the three-dimensional model of the required workpiece, the printed part after spraying is subjected to secondary machining, and the depth of the secondary machining is 0.5mm.

[0068] ⑤ Secondary sandblasting: The workpiece undergoes secondary machining and is sandblasted. The sand used in the secondary sandblasting is brown corundum. After sandblasting, isopropyl alcohol is sprayed. The nitrogen used in both the cold spraying and the secondary sandblasting is nitrogen with a purity of ≥99.99%. The sand particle size is 100 mesh. The sandblasting gas is compressed high-purity nitrogen with a pressure of 6 MPa. The distance between the nozzle and the sandblasting surface is 10 cm, and the sandblasting time per unit nozzle area is 1 second.

[0069] ⑥ Micro-arc oxidation: The workpiece that has undergone secondary sandblasting is placed in an electrolyte, with the workpiece as the anode and one or more of graphite plate and stainless steel as the cathode; a single-pulse constant voltage oxidation mode is used, and micro-arc oxidation is performed under the conditions of 700V voltage, 4000Hz frequency, and 45% duty cycle; the micro-arc oxidation time is 30min; the electrolyte includes the following components by weight: 5% sodium hexametaphosphate, 20% sodium borate, 2% sodium hydroxide, 0.2% nano boron oxide, and the balance is deionized water.

[0070] ⑦ Post-processing: The workpiece after micro-arc oxidation is rinsed and heat-treated to obtain a 3D-printed AlSi10Mg alloy part with an ultra-white oxide coating on the surface. The post-processing includes the following steps:

[0071] S1. First rinse: Rinse the workpiece again in a water glass solution at 95℃ for 90 seconds and then air dry naturally. The sodium silicate content of the water glass solution is 3g / L.

[0072] S2. Heat treatment: Perform three cycles of heat treatment. Each cycle is as follows: After the first rinse, the workpiece is held at 250°C for 3 minutes, then ignited with an acetylene flame at 2000°C, and then cooled in an atmosphere at 250°C for 3 minutes after cooling.

[0073] S3. Second rinse: Rinse the heat-treated workpiece in deionized water at 85℃ for 300 seconds and then air dry naturally.

[0074] Comparative Example 1

[0075] Includes the following steps:

[0076] ① Micro-arc oxidation: The workpiece that has undergone secondary sandblasting is placed in an electrolyte, with the workpiece being the anode and the cathode being one or more of graphite plate and stainless steel; a single-pulse constant voltage oxidation mode is used, with micro-arc oxidation under the conditions of 500V voltage, 1000Hz frequency, and 30% duty cycle; the micro-arc oxidation time is 20min; the electrolyte includes the following components by weight: 2% sodium hexametaphosphate, 10% sodium borate, 1% sodium hydroxide, 0.05% nano boron oxide, and the balance being deionized water.

[0077] ② Post-treatment: The workpiece after micro-arc oxidation is rinsed and heat-treated. The post-treatment includes the following steps:

[0078] S1. First rinse: Rinse the workpiece again in a water glass solution at 80℃ for 60 seconds and then air dry naturally. The sodium silicate content of the water glass solution is 1g / L.

[0079] S2. Heat treatment: Perform three cycles of heat treatment. Each cycle is as follows: After the first rinse, the workpiece is held at 200-250℃ for 1 minute, then the workpiece is ignited with an acetylene flame at 1800℃, and then the workpiece is cooled in an atmosphere of 200-250℃ and held at 1 minute after cooling.

[0080] S3. Second rinse: Rinse the heat-treated workpiece in deionized water at 70℃ for 180 seconds and then air dry naturally.

[0081] The workpieces prepared in Examples 1-3 and Comparative Example 1 were tested, and the sample test schematic diagrams of emissivity and absorptivity are shown below. Figure 1 As shown, the test conditions are as follows:

[0082] Film thickness testing equipment: PM5 Gen2 ultrasonic thickness gauge;

[0083] Emissivity: Hemispherical emissivity (4.5-20μm); Equipment used: Intelligent Fourier Transform Infrared Spectrometer;

[0084] Absorption ratio: Direct absorption ratio of sunlight; Equipment used: Ultraviolet-Vis-NearInfrared Spectrophotometer.

[0085] As can be seen from Table 1, the coatings prepared in Examples 1-3 have high emissivity and absorptivity; the oxide film prepared in Comparative Example 1, which was not pre-coated with aluminum-magnesium coating by cold spraying, has a darker color, significantly lower emissivity than Examples 1-3, and significantly higher absorptivity than Examples 1-3. Therefore, the present invention has high reflectivity and low absorptivity, and thus the alloy parts prepared by the present invention have superior thermal control and protection performance.

[0086] Example 1 Example 2 Example 3 Comparative Example 1 Film thickness (μm) 18.56 23.24 26.87 22.46 Emission rate 0.828 0.874 0.890 0.739 Absorption ratio 0.401 0.387 0.383 0.596

[0087] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a super-white oxidized coating on the surface of a 3D printed AlSi10Mg alloy part, characterized in that: The method comprises the following steps: ① first machining: reducing the three-dimensional model of the required workpiece by 0.5-1mm in proportion, and machining the 3D printed AlSi10Mg alloy workpiece based on the reduced three-dimensional model; ② first sand blasting: performing first sand blasting treatment on the workpiece after the first machining; the sand of the sand blasting treatment is a mixture of one or more of quartz sand, brown corundum or white steel corundum; ③ cold spraying: performing cold spraying treatment on the workpiece after the first sand blasting, wherein the powder for cold spraying comprises, by weight percentage, 5-10% magnesium powder, 0.5-1% boron oxide, and the balance aluminum powder; after the cold spraying is completed, isopropyl alcohol is sprayed again; ④ second machining: generating the three-dimensional model of the required workpiece as a reference to perform second machining on the printed workpiece after spraying; ⑤ second sand blasting: performing sand blasting treatment on the workpiece after the second machining, wherein the sand of the second sand blasting is brown corundum; After the sand blasting is completed, isopropyl alcohol is sprayed again; ⑥ micro-arc oxidation: placing the workpiece after the second sand blasting in an electrolyte, taking the workpiece after the second sand blasting as an anode, and performing micro-arc oxidation in a single pulse constant voltage oxidation mode under the conditions of a voltage of 500-700V, a frequency of 1000-4000Hz, and a duty cycle of 30-45%; ⑦ post-treatment: performing rinsing and heat treatment on the workpiece after the micro-arc oxidation.

2. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The post-treatment comprises the following steps: S1, first rinsing; S2, heat treatment: performing multiple cycles of heat treatment, wherein each cycle comprises: placing the workpiece after the first rinsing in an atmosphere at 200-250℃ for 1-3min, burning the workpiece with an acetylene flame at 1800-2000℃, and then cooling the workpiece in an atmosphere at 200-250℃, and then placing the workpiece in the atmosphere for 1-3min; S3, second rinsing.

3. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 2, characterized in that: The heat treatment comprises three cycles of heat treatment.

4. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 2, characterized in that: The first rinsing comprises: rinsing the workpiece in a water glass solution at a temperature of 80-95℃ for 60-90s, and then drying the workpiece; the water glass solution contains 1-3g / L of sodium silicate; The second rinsing comprises: rinsing the workpiece after the heat treatment in deionized water at 70-85℃ for 180-300s, and then drying the workpiece.

5. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The depth of the first machining is 0.5-1mm; the depth of the second machining is 0.5-0.6mm.

6. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The electrolyte of step ⑥ comprises the following components by weight: 2-5% sodium hexametaphosphate, 10-20% sodium borate, 1-2% sodium hydroxide, 0.05-0.2% nano boron oxide, and the balance deionized water.

7. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The cathode of the micro-arc oxidation of step ⑥ is one or more of graphite plate and stainless steel; the time of the micro-arc oxidation is 20-30min.

8. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The sand particle size of step ② is 10-40 mesh, the gas used is compressed air, the pressure is 6-6.5Mpa, the distance between the nozzle and the sand blasting surface is 5-15cm, and the sand blasting time per unit nozzle area is 1-2s.

9. The method for preparing surface super-white oxidized coating of 3D-printed AlSi10Mg alloy parts according to claim 1, characterized in that: The sand particle size of step ⑤ is 80-100 mesh, the sand blasting gas is compressed high-purity nitrogen gas, the gas pressure is 5.5-6Mpa, the distance between the nozzle and the sand blasting surface is 5-10cm, and the sand blasting time per unit nozzle area is 0.5-1s; The purity of the nitrogen gas is greater than or equal to 99.99%.

10. The method for preparing super-white oxidized coating on the surface of 3D printed AlSi10Mg alloy part according to claim 1, characterized in that: The spraying gas of the step ③ cold spraying is high-purity nitrogen, the spraying pressure is 0.8-1.5 Mpa, the preheating temperature is 250-350 DEG C, and the spraying distance is 15-30 mm; The preparation method of the cold spraying powder is that: aluminum powder, nano boron oxide particles and magnesium powder are sequentially put into a sealed tank, then anhydrous ethanol is added into the sealed tank, and nitrogen is injected; the powder is uniformly mixed by tank rotation, after the mixing is completed, the metal particles are naturally settled, then the supernatant is removed, and the lower solid-liquid mixture is the required cold spraying powder.

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