Heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film and preparation method thereof

Abstract

The application discloses a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film and a preparation method thereof, and relates to the technical field of ceramic films. The method comprises the following steps: after the cast aluminum alloy substrate is pretreated, bipolar pulse micro-arc oxidation treatment is carried out in an electrolyte containing silicate, phosphate and citrate; then the substrate is immersed in a rare earth-titanate composite solution containing CeO2, La2O3 and butyl titanate for heat curing, so as to realize pore sealing and heat-resistant modification; and then the substrate is immersed in a wear-resistant composite solution containing alpha-Al2O3, h-BN, KH-560 and PVP, and is subjected to ultrasonic-assisted infiltration and secondary curing to obtain the ceramic film. The heat-resistant modification layer of the rare earth-titanate and the wear-resistant modification layer of alpha-Al2O3 / h-BN are synergistically combined, and the interlayer bonding problem is solved by using KH-560 and PVP, so that the high-temperature oxidation resistance, thermal stability and wear-resistant life of the film layer are significantly improved, and the method is suitable for high-temperature and high-wear working conditions of the cast aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of ceramic membrane technology, specifically to a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic membrane and its preparation method. Background Technology

[0002] Cast aluminum alloys are widely used in automotive engine blocks, turbine housings, brake discs, and other components that need to withstand high temperatures and frictional loads due to their advantages such as low density, high specific strength, and good casting processability. However, cast aluminum alloys have low hardness and insufficient high-temperature oxidation resistance, often leading to premature failure due to thermal fatigue and wear during actual service. Micro-arc oxidation technology can grow a ceramic film with α-Al2O3 as the main phase in situ on the surface of cast aluminum alloys, significantly improving the hardness and corrosion resistance of the substrate. However, conventional micro-arc oxidation films still suffer from problems such as phase transformation cracking and poor thermal conductivity matching under high-temperature conditions, and the micropores and microcracks on the film surface make it difficult for their tribological properties to meet the requirements of harsh operating conditions. In the prior art, Chinese invention patent CN105624758B discloses a method for preparing a micro-arc oxidation ceramic film on cast aluminum alloys. This method reduces the coefficient of friction of the film and improves its wear resistance by adding Bi2O3 as a solid lubricant to the electrolyte. However, this technical solution only improves the wear resistance of a single property and does not address the high-temperature service stability of the film. Furthermore, Bi2O3 has a melting point of only 824℃, and it will soften or even decompose under high-temperature conditions, failing to meet the dual requirements of heat resistance and wear resistance. Therefore, there is an urgent need to develop a preparation method that can simultaneously impart excellent heat resistance and wear resistance to cast aluminum alloy micro-arc oxidation ceramic films. Summary of the Invention

[0003] The purpose of this invention is to provide a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film and its preparation method, so as to solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0006] 1) The cast aluminum alloy substrate is subjected to silicon carbide sandpaper polishing, acetone ultrasonic cleaning, deionized water rinsing and drying in sequence;

[0007] 2) The pretreated substrate was placed in an electrolyte containing sodium silicate nonahydrate, potassium hydroxide, sodium tripolyphosphate and trisodium citrate dihydrate, and bipolar pulsed micro-arc oxidation was performed with the substrate as the anode and the stainless steel tank as the cathode. After the reaction, it was rinsed with deionized water and dried.

[0008] 3) The sample obtained in step 2) is immersed in a rare earth-titanium composite modification solution prepared by cerium oxide nanopowder, lanthanum oxide nanopowder, polyvinylpyrrolidone, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol. After soaking, draining and drying, it is subjected to thermosetting treatment in a muffle furnace.

[0009] 4) Immerse the sample obtained in step 3) in a wear-resistant composite treatment solution prepared from α-alumina nanoparticles, hexagonal boron nitride micro powder, Tween-80, silane coupling agent KH-560, polyvinylpyrrolidone, aluminum dihydrogen phosphate, nano silica sol, ammonia and deionized water for ultrasonic-assisted impregnation treatment, or spray the above wear-resistant composite treatment solution onto the surface of the sample obtained in step 3), drain and dry, and then perform a secondary curing treatment in a muffle furnace to obtain a ceramic film.

[0010] The basic ceramic film generated by micro-arc oxidation is mainly composed of γ-Al2O3. Inevitably, microscopic defects such as discharge micropores and microcracks exist in the film. These defects become channels for the oxidizing medium to penetrate into the substrate under high-temperature service conditions, accelerating the high-temperature failure of the film. This invention addresses this by impregnating a composite modification liquid composed of CeO2 and La2O3 nano-rare earth oxides and a tetrabutyl titanate precursor into the micropores and microcracks of the film. After thermosetting, the tetrabutyl titanate transforms in situ within the film pores to form a TiO2 ceramic phase. This TiO2 phase exhibits good high-temperature stability, effectively filling and repairing microscopic defects in the film, significantly reducing the total porosity and defect density of the film, and constructing a dense sealing structure, thereby blocking the penetration and diffusion of high-temperature oxidizing media into the substrate along the pores. Meanwhile, CeO2 and La2O3 nanoparticles are uniformly distributed within the film layer with the aid of PVP as a dispersant. Rare earth oxides possess excellent high-temperature antioxidant activity and thermal stability, which can pin grain boundaries and inhibit abnormal grain growth under high-temperature service conditions. This effectively delays grain coarsening and microstructure degradation of the ceramic phase in the film layer during long-term high-temperature service, thus significantly improving the structural integrity and thermal cycling fatigue life of the film layer under high-temperature conditions. Furthermore, the dense composite sealing structure formed by TiO2 and rare earth oxides within the film layer reduces the conduction rate of high-temperature heat from the film surface to the aluminum alloy substrate, reducing thermal shock to the substrate and further improving the service reliability of the cast aluminum alloy under high-temperature conditions.

[0011] The ceramic film surface after micro-arc oxidation inevitably contains discharge micropores and microcracks. These microscopic defects become stress concentration sources and wear debris accumulation points during friction, accelerating film wear failure. This invention introduces α-Al₂O₃ nanoparticles and hexagonal boron nitride microparticles into the pores and surface of the film using an ultrasonic-assisted infiltration process with aluminum phosphate-silica sol as a carrier. The α-Al₂O₃ nanoparticles, with their extremely high hardness, act as hard fillers and load-bearing elements in the film pores, significantly improving the overall hardness and indentation resistance of the film surface and reducing plowing and micro-cutting damage to the film from the mating parts during friction. Hexagonal boron nitride has a graphite-like layered crystal structure, with weak van der Waals forces between the layers. During friction, interlayer slippage easily occurs, forming a continuous solid lubrication transfer film in situ at the friction interface, effectively reducing the coefficient of friction and minimizing adhesive wear. During the secondary curing process, aluminum phosphate undergoes dehydration and condensation to form a three-dimensional network cemented structure. Nano-SiO2 sol further fills the micropores between the networks. The composite carrier matrix formed by these two components firmly anchors α-Al2O3 and h-BN particles within the micropores and surface pits of the film, preventing the wear-resistant particles from detaching and loosening during friction, thus ensuring the long-term durability of the wear-resistant modification effect of the film. The ultrasonic-assisted infiltration process utilizes the localized high-temperature, high-pressure microjets generated by ultrasonic cavitation to overcome the tendency of nanoparticles to aggregate due to their high surface energy. This promotes the uniform and dense penetration of wear-resistant particles into the deep pores of the film, improving the overall density and load-bearing uniformity of the ceramic film and significantly extending its wear-resistant life.

[0012] Preferably, in step 2), the concentration of sodium silicate nonahydrate in the electrolyte is 10-12 g / L.

[0013] Preferably, in step 2), the concentration of sodium tripolyphosphate in the electrolyte is 4-5 g / L.

[0014] Preferably, in step 2), the concentration of trisodium citrate dihydrate in the electrolyte is 1-2 g / L.

[0015] Preferably, in step 2), the bipolar pulsed micro-arc oxidation treatment time is 15 to 25 minutes.

[0016] Preferably, in step 3), the mass ratio of cerium oxide nanoparticles to lanthanum oxide nanoparticles is 1:(0.6-0.8).

[0017] Preferably, in step 3), the thermosetting temperature is 150–230°C and the thermosetting time is 50–90 min.

[0018] Preferably, in step 4), the mass ratio of the α-alumina nanoparticles to the hexagonal boron nitride micropowder is 3.5:(0.8-1.2).

[0019] Preferably, in step 4), the mass ratio of the silane coupling agent KH-560 to polyvinylpyrrolidone is 5:(1-3).

[0020] In the experiment, this invention found that after thermosetting during the heat-resistant modification process, the micropores and microcracks of the film were filled with TiO2 and rare earth oxides, forming a dense ceramic sealing layer. Although this significantly improved the heat resistance of the film, it also greatly reduced the surface porosity and pore connectivity of the film. As a result, the α-Al2O3 and h-BN particles in the subsequent wear-resistant modification could not effectively penetrate into the interior of the film. A large number of wear-resistant particles remained on the outermost surface of the film and could not be deeply anchored. They were very easy to fall off after friction load, which greatly reduced the wear-resistant modification effect. To address this technical problem, this invention introduces the silane coupling agent KH-560 and polyvinylpyrrolidone into the wear-resistant modification treatment solution. The methoxysilane group at one end of the KH-560 molecule can undergo a condensation reaction with the hydroxyl groups on the surface of the heat-modified TiO2 and rare earth oxide sealing layer, establishing a chemically bonded organosilane bridging layer on the sealing layer surface. The epoxy group at the other end can undergo ring-opening condensation with the aluminum phosphate carrier during the subsequent thermosetting stage, thereby gradually constructing a composite interfacial transition layer with synergistic effects of chemical bonding and physical adsorption between the sealed pore layer and the wear-resistant particle-carrier composite layer. This approach solves the problem of insufficient interfacial bonding between the heat-resistant modified layer and the wear-resistant modified layer due to differences in surface energy and pore blockage. PVP, as a high-molecular-weight surfactant, forms a steric stabilizing layer on the particle surface by coordinating and adsorbing with the active sites on the surface of α-Al₂O₃ and h-BN particles through the carbonyl group on its pyrrolidone ring. This effectively prevents the agglomeration and accumulation of wear-resistant particles above the sealing layer, allowing for more uniform dispersion and deposition of particles in residual micropores and surface micro-pits. Furthermore, it improves the wettability between the particles and the carrier matrix, enhancing the overall density and bonding strength of the composite layer. The synergistic effect of KH-560 and PVP simultaneously solves the technical challenges of difficult penetration of wear-resistant modification and weak interfacial bonding caused by heat-resistant modification sealing, addressing both chemical bonding and physical dispersion. This allows the effects of heat-resistant and wear-resistant modification to be fully superimposed without interference, ultimately achieving a synergistic improvement in the heat resistance and wear resistance of the ceramic film.

[0021] A heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film is prepared by the above method.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. By filling the micropores and cracks of the micro-arc oxidation film with a composite modified liquid of CeO2, La2O3 and TiO2, a sealed pore structure is formed to block the penetration of high-temperature oxidation media; at the same time, rare earth oxides pin the grain boundaries, inhibit grain coarsening, reduce heat conduction, and significantly improve the high-temperature structural stability and thermal cycling fatigue life of the film.

[0024] 2. By utilizing the hard bearing capacity of α-Al2O3 nanoparticles and the solid lubrication properties of h-BN, combined with ultrasonic-assisted impregnation and composite carrier anchoring, a uniform and dense wear-resistant layer is formed in the film, which effectively reduces the coefficient of friction and wear rate, and significantly extends the wear life of the film.

[0025] 3. By leveraging the synergistic effect of silane coupling agent KH-560 and PVP, the problems of poor penetration of wear-resistant particles and poor interfacial bonding after heat-resistant modification and sealing are solved from both chemical bonding and physical dispersion perspectives. This allows the two modification effects to be fully superimposed, achieving a synergistic improvement in the heat resistance and wear resistance of the ceramic film. Attached Figure Description

[0026] Figure 1 This is a low-magnification SEM image of the surface of the cast aluminum alloy micro-arc oxidation ceramic film prepared in Example 4 of the present invention.

[0027] Figure 2 This is a medium-magnification SEM image of the surface of the cast aluminum alloy micro-arc oxidation ceramic film prepared in Example 4 of the present invention.

[0028] Figure 3 This is a high-magnification SEM image of the surface of the cast aluminum alloy micro-arc oxidation ceramic film prepared in Example 4 of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0032] Step 1) Select a ZL101A cast aluminum alloy sample with dimensions of 50mm×20mm×5mm. Grind it step by step with 400#, 800#, 1200# and 2000# silicon carbide sandpaper until the surface has a uniform metallic luster. Then polish it until there are no fine scratches. Place the sample in an appropriate amount of acetone and ultrasonically clean it at a frequency of 40kHz for 12 minutes. After taking it out, rinse it with deionized water 3 times and dry it in a 60℃ forced-air drying oven for 30 minutes. Take it out for later use.

[0033] Step 2) Add sodium silicate nonahydrate, sodium tripolyphosphate and trisodium citrate dihydrate sequentially to deionized water. The concentrations of each component are as follows: sodium silicate nonahydrate 11.5 g / L, potassium hydroxide 4 g / L, sodium tripolyphosphate 4.8 g / L and trisodium citrate dihydrate 1.8 g / L. Stir until completely dissolved and let stand for 10 min. Immerse the sample treated in Step 1) as the anode in the electrolyte. Use a stainless steel tank as the cathode. Use a bipolar pulse power supply with a positive voltage of 400 V, a negative voltage of 100 V, a pulse frequency of 650 Hz and a duty cycle of 30%. Control the electrolyte temperature at 25 °C. Perform the micro-arc oxidation reaction for 20 min. After the reaction, take out the sample, rinse the surface with deionized water to remove residual electrolyte, and dry at 60 °C for 20 min to obtain the micro-arc oxidation base film.

[0034] Step 3) Add 1.0 g of cerium oxide nanoparticles, 0.75 g of lanthanum oxide nanoparticles, and 0.2 g of polyvinylpyrrolidone (PVP, K30) sequentially to 50 mL of anhydrous ethanol, and ultrasonically disperse at 40 kHz for 20 min to obtain dispersion A; add 2.0 g of tetrabutyl titanate to 30 mL of anhydrous ethanol, stir evenly, and slowly add 1.8 mL of glacial acetic acid for chelation stabilization, and continue stirring for 15 min to obtain solution B; slowly add solution B to dispersion A and stir at 450 r / min for 20 min to obtain composite modified solution C; immerse the sample obtained in step 2) in composite modified solution C, soak it in a 50℃ water bath for 45 min (turning it over every 10 min), take it out and drain it, and pre-dry it at 80℃ for 30 min; put the pre-dried sample into a muffle furnace, heat it to 200℃ at 3℃ / min and hold it for 70 min for thermosetting treatment, and cool it to room temperature with the furnace to obtain a heat-resistant modified film layer.

[0035] Step 4) Add 3.5g of α-alumina nanoparticles, 1.1g of hexagonal boron nitride micropowder, and 0.6g of Tween-80 sequentially to 80mL of deionized water, and ultrasonically disperse at 40kHz for 30min to obtain dispersion D; separately add 3.5g of aluminum dihydrogen phosphate to 40mL of deionized water, stir until completely dissolved, then add 0.8g of nano-silica sol (30% solid content), stir for 10min, then add 0.8mL of ammonia water (25% by mass) dropwise to adjust the pH to 4-5, and continue stirring for 5min to obtain carrier solution E; add 0.5g of silane coupling agent KH-560 to dispersion D. Add 0.25g of polyvinylpyrrolidone (PVP, K30) and stir for 10min. Then add carrier liquid E and stir at 500r / min for 15min to obtain wear-resistant composite treatment liquid F. Immerse the sample obtained in step 3) into treatment liquid F, turn on the ultrasonic generator (40kHz, 280W), control the temperature of the treatment liquid at 35℃, and ultrasonically assist in the impregnation for 35min. After draining, dry at 100℃ for 40min. Place the dried sample in a muffle furnace and heat it to 220℃ at 2℃ / min and hold for 60min for secondary curing treatment. Cool it to room temperature with the furnace to obtain a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film.

[0036] Example 2

[0037] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0038] Step 1) Select a ZL101A cast aluminum alloy sample with dimensions of 50mm×20mm×5mm. Grind it step by step with 400#, 800#, 1200# and 2000# silicon carbide sandpaper until the surface has a uniform metallic luster. Then polish it until there are no fine scratches. Place the sample in an appropriate amount of acetone and ultrasonically clean it at a frequency of 40kHz for 12 minutes. After taking it out, rinse it with deionized water 3 times and dry it in a 60℃ forced-air drying oven for 30 minutes. Take it out for later use.

[0039] Step 2) Add sodium silicate nonahydrate, sodium tripolyphosphate and trisodium citrate dihydrate sequentially to deionized water. The concentrations of each component are as follows: sodium silicate nonahydrate 10.5 g / L, potassium hydroxide 4 g / L, sodium tripolyphosphate 4.3 g / L and trisodium citrate dihydrate 1.2 g / L. Stir until completely dissolved and let stand for 10 min. Immerse the sample treated in Step 1) as the anode in the electrolyte. Use a stainless steel tank as the cathode. Use a bipolar pulse power supply with a positive voltage of 400 V, a negative voltage of 100 V, a pulse frequency of 650 Hz and a duty cycle of 30%. Control the electrolyte temperature at 25 °C. Perform the micro-arc oxidation reaction for 20 min. After the reaction, take out the sample, rinse the surface with deionized water to remove residual electrolyte, and dry at 60 °C for 20 min to obtain the micro-arc oxidation base film.

[0040] Step 3) Add 1.0 g of cerium oxide nanoparticles, 0.65 g of lanthanum oxide nanoparticles, and 0.2 g of polyvinylpyrrolidone (PVP, K30) sequentially to 50 mL of anhydrous ethanol, and ultrasonically disperse at 40 kHz for 20 min to obtain dispersion A; add 2.0 g of tetrabutyl titanate to 30 mL of anhydrous ethanol, stir evenly, and slowly add 1.8 mL of glacial acetic acid for chelation stabilization, and continue stirring for 15 min to obtain solution B; slowly add solution B to dispersion A and stir at 450 r / min for 20 min to obtain composite modified solution C; immerse the sample obtained in step 2) in composite modified solution C, soak in a 50℃ water bath for 45 min (turning over every 10 min), remove and drain, and pre-dry at 80℃ for 30 min; place the pre-dried sample in a muffle furnace, heat to 200℃ at 3℃ / min and hold for 70 min for thermosetting treatment, and cool to room temperature with the furnace to obtain a heat-resistant modified film layer.

[0041] Step 4) Add 3.5g of α-alumina nanoparticles, 0.9g of hexagonal boron nitride micropowder, and 0.6g of Tween-80 sequentially to 80mL of deionized water, and ultrasonically disperse at 40kHz for 30min to obtain dispersion D; separately add 3.5g of aluminum dihydrogen phosphate to 40mL of deionized water, stir until completely dissolved, then add 0.8g of nano-silica sol (30% solid content), stir for 10min, then add 0.8mL of ammonia water (25% by mass) dropwise to adjust the pH to 4-5, and continue stirring for 5min to obtain carrier solution E; add 0.5g of silane coupling agent KH-560 to dispersion D. Add 0.15g of polyvinylpyrrolidone (PVP, K30) and stir for 10min. Then add carrier liquid E and stir at 500r / min for 15min to obtain wear-resistant composite treatment liquid F. Immerse the sample obtained in step 3) into treatment liquid F, turn on the ultrasonic generator (40kHz, 280W), control the temperature of the treatment liquid at 35℃, and ultrasonically assist in impregnation for 35min. After draining, dry at 100℃ for 40min. Place the dried sample in a muffle furnace and heat it to 220℃ at 2℃ / min and hold for 60min for secondary curing treatment. Cool to room temperature with the furnace to obtain a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film.

[0042] Example 3

[0043] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0044] Step 1) Select a ZL101A cast aluminum alloy sample with dimensions of 50mm×20mm×5mm. Grind it step by step with 400#, 800#, 1200# and 2000# silicon carbide sandpaper until the surface has a uniform metallic luster. Then polish it until there are no fine scratches. Place the sample in an appropriate amount of acetone and ultrasonically clean it at a frequency of 40kHz for 12 minutes. After taking it out, rinse it with deionized water 3 times and dry it in a 60℃ forced-air drying oven for 30 minutes. Take it out for later use.

[0045] Step 2) Add sodium silicate nonahydrate, potassium hydroxide sodium tripolyphosphate, and trisodium citrate dihydrate sequentially to deionized water. The concentrations of each component are as follows: sodium silicate nonahydrate 11 g / L, potassium hydroxide 4 g / L, sodium tripolyphosphate 4.5 g / L, and trisodium citrate dihydrate 1.5 g / L. Stir until completely dissolved and let stand for 10 min. Immerse the sample treated in Step 1) as the anode in the electrolyte. Use a stainless steel tank as the cathode. Use a bipolar pulse power supply with a positive voltage of 400 V, a negative voltage of 100 V, a pulse frequency of 650 Hz, and a duty cycle of 30%. Control the electrolyte temperature at 25 °C. Perform the micro-arc oxidation reaction for 20 min. After the reaction, remove the sample, rinse the surface with deionized water to remove residual electrolyte, and dry at 60 °C for 20 min to obtain the micro-arc oxidation base film.

[0046] Step 3) Add 1.0 g of cerium oxide nanoparticles, 0.7 g of lanthanum oxide nanoparticles, and 0.2 g of polyvinylpyrrolidone (PVP, K30) sequentially to 50 mL of anhydrous ethanol, and ultrasonically disperse at 40 kHz for 20 min to obtain dispersion A; add 2.0 g of tetrabutyl titanate to 30 mL of anhydrous ethanol, stir evenly, and slowly add 1.8 mL of glacial acetic acid for chelation stabilization, and continue stirring for 15 min to obtain solution B; slowly add solution B to dispersion A and stir at 450 r / min for 20 min to obtain composite modified solution C; immerse the sample obtained in step 2) in composite modified solution C, soak in a 50℃ water bath for 45 min (turning over every 10 min), remove and drain, and pre-dry at 80℃ for 30 min; place the pre-dried sample in a muffle furnace, heat to 200℃ at 3℃ / min and hold for 70 min for thermosetting treatment, and cool to room temperature with the furnace to obtain a heat-resistant modified film layer.

[0047] Step 4) Add 3.5g of α-alumina nanoparticles, 1.0g of hexagonal boron nitride micropowder, and 0.6g of Tween-80 sequentially to 80mL of deionized water, and ultrasonically disperse at 40kHz for 30min to obtain dispersion D; separately add 3.5g of aluminum dihydrogen phosphate to 40mL of deionized water, stir until completely dissolved, then add 0.8g of nano-silica sol (30% solid content), stir for 10min, then add 0.8mL of ammonia water (25% by mass) dropwise to adjust the pH to 4-5, and continue stirring for 5min to obtain carrier solution E; add 0.5g of silane coupling agent KH-56 to dispersion D. 0 and 0.2 g of polyvinylpyrrolidone (PVP, K30) were stirred for 10 min, and then carrier liquid E was added. The mixture was stirred at 500 r / min for 15 min to obtain wear-resistant composite treatment liquid F. The sample obtained in step 3) was immersed in treatment liquid F, and an ultrasonic generator (40 kHz, 280 W) was turned on. The temperature of the treatment liquid was controlled at 35 ℃, and ultrasonic-assisted impregnation was carried out for 35 min. After being taken out and drained, the sample was dried at 100 ℃ for 40 min. The dried sample was placed in a muffle furnace and heated to 220 ℃ at 2 ℃ / min and held for 60 min for secondary curing treatment. The sample was then cooled to room temperature with the furnace to obtain a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film.

[0048] Example 4

[0049] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0050] Step 1) Select a ZL101A cast aluminum alloy sample with dimensions of 50mm×20mm×5mm. Grind it step by step with 400#, 800#, 1200# and 2000# silicon carbide sandpaper until the surface has a uniform metallic luster. Then polish it until there are no fine scratches. Place the sample in an appropriate amount of acetone and ultrasonically clean it at a frequency of 40kHz for 12 minutes. After taking it out, rinse it with deionized water 3 times and dry it in a 60℃ forced-air drying oven for 30 minutes. Take it out for later use.

[0051] Step 2) Add sodium silicate nonahydrate, potassium hydroxide sodium tripolyphosphate, and trisodium citrate dihydrate sequentially to deionized water. The concentrations of each component are as follows: sodium silicate nonahydrate 12 g / L, potassium hydroxide 4 g / L, sodium tripolyphosphate 5 g / L, and trisodium citrate dihydrate 2 g / L. Stir until completely dissolved and let stand for 10 min. Immerse the sample treated in Step 1) as the anode in the electrolyte. Use a stainless steel tank as the cathode. Use a bipolar pulse power supply with a positive voltage of 400 V, a negative voltage of 100 V, a pulse frequency of 650 Hz, and a duty cycle of 30%. Control the electrolyte temperature at 25 °C. Perform the micro-arc oxidation reaction for 25 min. After the reaction, remove the sample, rinse the surface with deionized water to remove residual electrolyte, and dry at 60 °C for 20 min to obtain the micro-arc oxidation base film.

[0052] Step 3) Add 1.0 g of cerium oxide nanoparticles, 0.8 g of lanthanum oxide nanoparticles, and 0.2 g of polyvinylpyrrolidone (PVP, K30) sequentially to 50 mL of anhydrous ethanol, and ultrasonically disperse at 40 kHz for 20 min to obtain dispersion A; add 2.0 g of tetrabutyl titanate to 30 mL of anhydrous ethanol, stir evenly, and slowly add 1.8 mL of glacial acetic acid for chelation stabilization, and continue stirring for 15 min to obtain solution B; slowly add solution B to dispersion A and stir at 450 r / min for 20 min to obtain composite modified solution C; immerse the sample obtained in step 2) in composite modified solution C, soak in a 50℃ water bath for 45 min (turning over every 10 min), remove and drain, and pre-dry at 80℃ for 30 min; place the pre-dried sample in a muffle furnace, heat to 230℃ at 3℃ / min and hold for 50 min for thermosetting treatment, and cool to room temperature with the furnace to obtain a heat-resistant modified film layer.

[0053] Step 4) Add 3.5g of α-alumina nanoparticles, 1.2g of hexagonal boron nitride micropowder, and 0.6g of Tween-80 sequentially to 80mL of deionized water, and ultrasonically disperse at 40kHz for 30min to obtain dispersion D; separately add 3.5g of aluminum dihydrogen phosphate to 40mL of deionized water, stir until completely dissolved, then add 0.8g of nano-silica sol (30% solid content), stir for 10min, then add 0.8mL of ammonia water (25% by mass) dropwise to adjust the pH to 4-5, and continue stirring for 5min to obtain carrier solution E; add 0.5g of silane coupling agent KH-56 to dispersion D. 0 and 0.3 g of polyvinylpyrrolidone (PVP, K30) were stirred for 10 min, and then carrier liquid E was added. The mixture was stirred at 500 r / min for 15 min to obtain wear-resistant composite treatment liquid F. The sample obtained in step 3) was immersed in treatment liquid F, and an ultrasonic generator (40 kHz, 280 W) was turned on. The temperature of the treatment liquid was controlled at 35 ℃, and ultrasonic-assisted impregnation was carried out for 35 min. After being taken out and drained, the sample was dried at 100 ℃ for 40 min. The dried sample was placed in a muffle furnace and heated to 220 ℃ at 2 ℃ / min and held for 60 min for secondary curing treatment. The sample was then cooled to room temperature with the furnace to obtain a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film.

[0054] Example 5

[0055] A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film includes the following steps:

[0056] Step 1) Select a ZL109A cast aluminum alloy sample with dimensions of 50mm×20mm×5mm. Grind it step by step with 400#, 800#, 1200# and 2000# silicon carbide sandpaper until the surface has a uniform metallic luster. Then polish it until there are no fine scratches. Place the sample in an appropriate amount of acetone and ultrasonically clean it at a frequency of 40kHz for 12 minutes. After taking it out, rinse it with deionized water 3 times and dry it in a 60℃ forced-air drying oven for 30 minutes. Take it out for use.

[0057] Step 2) Add sodium silicate nonahydrate, potassium hydroxide sodium tripolyphosphate, and trisodium citrate dihydrate sequentially to deionized water. The concentrations of each component are: sodium silicate nonahydrate 10 g / L, potassium hydroxide 4 g / L, sodium tripolyphosphate 4 g / L, and trisodium citrate dihydrate 1 g / L. Stir until completely dissolved and let stand for 10 min. Immerse the sample treated in Step 1) as the anode in the electrolyte. Use a stainless steel tank as the cathode. Use a bipolar pulse power supply with a positive voltage of 400 V, a negative voltage of 100 V, a pulse frequency of 650 Hz, and a duty cycle of 30%. Control the electrolyte temperature at 25 °C. Perform the micro-arc oxidation reaction for 15 min. After the reaction, remove the sample, rinse the surface with deionized water to remove residual electrolyte, and dry at 60 °C for 20 min to obtain the micro-arc oxidation base film.

[0058] Step 3) Add 1.0 g of cerium oxide nanoparticles, 0.6 g of lanthanum oxide nanoparticles, and 0.2 g of polyvinylpyrrolidone (PVP, K30) sequentially to 50 mL of anhydrous ethanol, and ultrasonically disperse at 40 kHz for 20 min to obtain dispersion A; add 2.0 g of tetrabutyl titanate to 30 mL of anhydrous ethanol, stir evenly, and slowly add 1.8 mL of glacial acetic acid for chelation stabilization, and continue stirring for 15 min to obtain solution B; slowly add solution B to dispersion A and stir at 450 r / min for 20 min to obtain composite modified solution C; immerse the sample obtained in step 2) in composite modified solution C, soak in a 50℃ water bath for 45 min (turning over every 10 min), remove and drain, and pre-dry at 80℃ for 30 min; place the pre-dried sample in a muffle furnace, heat to 150℃ at 3℃ / min and hold for 90 min for thermosetting treatment, and cool to room temperature with the furnace to obtain a heat-resistant modified film layer.

[0059] Step 4) Add 3.5g of α-alumina nanoparticles, 0.8g of hexagonal boron nitride micropowder, and 0.6g of Tween-80 sequentially to 80mL of deionized water, and ultrasonically disperse at 40kHz for 30min to obtain dispersion D; separately add 3.5g of aluminum dihydrogen phosphate to 40mL of deionized water, stir until completely dissolved, then add 0.8g of nano-silica sol (30% solid content), stir for 10min, then add 0.8mL of ammonia water (25% by mass) dropwise to adjust the pH to 4-5, and continue stirring for 5min to obtain carrier solution E; add 0.5g of silane coupling agent KH-56 to dispersion D. 0 and 0.1 g of polyvinylpyrrolidone (PVP, K30) were stirred for 10 min, and then carrier liquid E was added. The mixture was stirred at 500 r / min for 15 min to obtain wear-resistant composite treatment liquid F. The sample obtained in step 3) was immersed in treatment liquid F, and an ultrasonic generator (40 kHz, 280 W) was turned on. The temperature of the treatment liquid was controlled at 35 ℃, and ultrasonic-assisted impregnation was carried out for 35 min. After being taken out and drained, the sample was dried at 100 ℃ for 40 min. The dried sample was placed in a muffle furnace and heated to 220 ℃ at 2 ℃ / min and held for 60 min for secondary curing treatment. The sample was then cooled to room temperature with the furnace to obtain a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film.

[0060] Comparative Example 1: Compared with Example 4, step 3) heat resistance modification treatment was not performed, and step 4) wear resistance modification treatment was directly performed on the micro-arc oxidation base film layer.

[0061] Comparative Example 2: Compared with Example 4, only step 3) heat resistance modification treatment was performed, and step 4) wear resistance modification treatment was not performed.

[0062] Comparative Example 3: Compared with Example 4, step 4) did not include silane coupling agent KH-560 and polyvinylpyrrolidone (PVP).

[0063] Comparative Example 4: Compared with Example 4, no silane coupling agent KH-560 was added in step 4).

[0064] Comparative Example 5: Compared with Example 4, polyvinylpyrrolidone (PVP) was not added in step 4).

[0065] Performance testing:

[0066] (1) Film thickness test

[0067] The ceramic film thickness of each embodiment and comparative sample was measured using a MiniTest 730 eddy current thickness gauge. Before testing, the sample was calibrated using the standard film provided with the sample. Then, the probe was placed vertically and tightly against the central area of ​​the sample surface. Five different test points were randomly selected for each sample for measurement. The arithmetic mean of the five measurement results was taken as the film thickness value of the sample. The test accuracy was ±1μm.

[0068] (2) Microhardness test

[0069] The microhardness of the ceramic film surface of each sample was measured using an HVS-1000A Vickers microhardness tester. The test load was 0.98 N (HV0.1), and the holding time was 15 s. Five different locations were randomly selected on the film surface of each sample for indentation testing. After removing abnormal data with a deviation exceeding 15% of the average value, the arithmetic mean was taken as the microhardness value of the sample. The test results are expressed as HV0.1.

[0070] (3) Friction coefficient test

[0071] The tribological properties of each specimen were evaluated using a CFT-I type multifunctional friction and wear testing machine. The friction pair consisted of φ6 mm GCr15 bearing steel balls (hardness approximately 62 HRC). The test mode was rotating ball-disc contact, with a normal load of 5 N, a rotational speed of 200 r / min, a wear radius of 3 mm, and a total sliding distance of 500 m. The entire test was conducted at room temperature and in an atmospheric environment. The testing machine automatically collected and recorded the curve of friction coefficient changing with sliding distance. The average value of the friction coefficient in the stable phase (100–500 m range) was taken as the steady-state friction coefficient of the specimen.

[0072] (4) Wear rate test

[0073] After the friction and wear test, the three-dimensional morphology of the wear tracks on each sample was scanned and quantitatively analyzed using a VHX-600 ultra-depth-of-field three-dimensional microscope. The cross-sectional area of ​​the wear track was automatically calculated by software, and the wear track volume V (mm²) was obtained by integrating along the circumference of the wear track. 3 The wear rate is calculated using the formula W=V / (F·L), where F is the normal load (N) and L is the total sliding distance (m), with units of mm. 3 / (N·m), each sample was tested 3 times and the average value was taken.

[0074] (5) High-temperature thermal shock performance test

[0075] Each sample was placed in a muffle furnace preheated to 400°C and held for 10 minutes. Then, it was quickly removed and immersed in deionized water at 25°C to cool to room temperature. After the sample temperature returned to room temperature, it was removed, dried, and the surface condition of the film was observed. The above operation was repeated by placing it back into the muffle furnace at 400°C. This process was repeated until visible peeling, warping, or through cracks were observed on the surface of the film under a stereomicroscope. The number of cycles was recorded as the thermal shock life of the sample. The larger the value, the better the thermal fatigue resistance of the film.

[0076] (6) High-temperature oxidation weight gain test

[0077] Each sample was weighed using an analytical balance (accuracy 0.01 mg) to obtain its initial mass m0. The samples were then placed flat in a corundum crucible and placed in a muffle furnace. Oxidation was carried out continuously at 400℃ in air for 100 hours. After oxidation, the samples were cooled to room temperature in the furnace, and the mass m1 was measured again. The weight gain from high-temperature oxidation was calculated as Δm = (m1 - m0) / S, where S is the heated area of ​​the sample (cm²). 2 The results were expressed in mg / cm³ 2 This indicates that the smaller the value, the stronger the film's ability to protect against high-temperature oxidation of the substrate.

[0078] Table 1: Test Results of Examples and Comparative Examples

[0079]

[0080] As can be seen from the table above:

[0081] Comparative Example 1 (without heat resistance modification) only underwent 25 thermal shock cycles, with an oxidation weight gain as high as 0.76 mg / cm³. 2 This is far worse than the 142 times and 0.12 mg / cm² observed in Example 4. 2 This indicates that the CeO2 / La2O3-TiO2 composite sealing layer plays a key role in improving the high-temperature structural stability and oxidation resistance of the film; however, the friction coefficient of Comparative Example 1 (0.25) is close to that of Example 4, indicating that the wear-resistant modified layer itself has an independent lubrication and friction reduction function at room temperature.

[0082] Comparative Example 2 (without wear-resistant modification) had a friction coefficient as high as 0.52 and a wear rate of 5.80 × 10⁻⁶. -5 mm 3 / (N·m), which is much worse than 0.23 and 0.85×10 in Example 4. -5 mm 3 / (N·m), indicating that heat-resistant modification and pore sealing alone cannot improve the tribological properties of the film; however, the thermal shock cycles (138 times) and oxidative weight gain (0.14 mg / cm³) of Comparative Example 2 were significantly reduced. 2 Similar to Example 4, this further confirms that the high-temperature protection effect of the heat-resistant modified layer does not depend on the wear-resistant modified layer.

[0083] The wear rate of Comparative Example 3 (without KH-560 and PVP) was 3.25 × 10⁻⁶. -5 mm 3 / (N·m), Comparative Example 4 (without KH-560) is 2.68×10 -5 mm 3 / (N·m), Comparative Example 5 (without PVP) is 2.12×10 -5 mm 3 / (N·m), all significantly higher than 0.85×10 in Example 4.-5 mm 3 The value of KH-560 / (N·m) shows a decreasing trend of no KH-560 and PVP > no KH-560 > no PVP, indicating that the chemical bonding bridging effect of KH-560 and the dispersion stabilizing effect of PVP both contribute independently to the wear resistance modification effect. The effect is optimal when the two are used in combination, which verifies the necessity of the interface synergistic optimization design of the present invention.

[0084] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film, characterized in that, Includes the following steps: 1) The cast aluminum alloy substrate is subjected to silicon carbide sandpaper grinding, polishing, acetone ultrasonic cleaning, deionized water rinsing and drying in sequence; 2) The pretreated substrate was placed in an electrolyte containing sodium silicate nonahydrate, potassium hydroxide, sodium tripolyphosphate and trisodium citrate dihydrate, and bipolar pulsed micro-arc oxidation was performed with the substrate as the anode and the stainless steel tank as the cathode. After the reaction, it was rinsed with deionized water and dried. 3) The sample obtained in step 2) is immersed in a rare earth-titanium composite modification solution prepared by cerium oxide nanopowder, lanthanum oxide nanopowder, polyvinylpyrrolidone, tetrabutyl titanate, glacial acetic acid and anhydrous ethanol. After soaking, draining and drying, it is subjected to thermosetting treatment in a muffle furnace. 4) Immerse the sample obtained in step 3) in a wear-resistant composite treatment solution prepared from α-alumina nanoparticles, hexagonal boron nitride micro powder, Tween-80, silane coupling agent KH-560, polyvinylpyrrolidone, aluminum dihydrogen phosphate, nano silica sol, ammonia and deionized water for ultrasonic-assisted impregnation treatment, or spray the above wear-resistant composite treatment solution onto the surface of the sample obtained in step 3), drain and dry, and then perform a secondary curing treatment in a muffle furnace to obtain a ceramic film.

2. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 2), the concentration of sodium silicate nonahydrate in the electrolyte is 10-12 g / L.

3. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 2), the concentration of sodium tripolyphosphate in the electrolyte is 4-5 g / L.

4. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 2), the concentration of trisodium citrate dihydrate in the electrolyte is 1-2 g / L.

5. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 2), the bipolar pulsed micro-arc oxidation treatment time is 15 to 25 minutes.

6. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 3), the mass ratio of cerium oxide nanoparticles to lanthanum oxide nanoparticles is 1:(0.6-0.8).

7. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 3), the thermosetting temperature is 150-230℃ and the thermosetting time is 50-90 min.

8. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 4), the mass ratio of the α-alumina nanoparticles to the hexagonal boron nitride micropowder is 3.5:(0.8-1.2).

9. The method for preparing a heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film according to claim 1, characterized in that, In step 4), the mass ratio of the silane coupling agent KH-560 to polyvinylpyrrolidone is 5:(1-3).

10. A heat-resistant and wear-resistant cast aluminum alloy micro-arc oxidation ceramic film, characterized in that, It is prepared by the method described in any one of claims 1-9 above.

Images