High-silicon aluminum alloy coating as well as preparation method and application thereof

Abstract

The invention relates to a high-silicon aluminum alloy coating and a preparation method and application thereof. The high-silicon aluminum alloy coating has a pseudo-eutectic structure. The pseudo eutectic structure comprises a characteristic-free area; and the size of the Si phase in the non-characteristic area is 20-80 nm. According to the Hall-etch effect, the strengthening effect of a Si strengthening phase is fully exerted by a nanoscale refined and dispersively distributed Si phase in the high-silicon aluminum alloy coating, the situation that a base body is cut by a thick Si phase of a conventional cast aluminum-silicon alloy and cracks are generated is avoided, and the mechanical property of the high-silicon aluminum alloy coating is fully strengthened. The high-silicon aluminum alloy coating is good in high-temperature stability and excellent in service mechanical property at the temperature of 300 DEG C, and compared with the room temperature, the room temperature is not obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of metal surface modification technology, and in particular to a high-silicon aluminum alloy coating, its preparation method, and its application. Background Technology

[0002] Al-Si alloys are lightweight and possess outstanding high-temperature resistance, specific strength, and wear resistance, making them widely applicable in the automotive industry. However, traditional aluminum-silicon alloys suffer from insufficient stability at high temperatures, with mechanical properties significantly decreasing above 200°C, limiting the temperature range in which Al-Si alloys are suitable for use. Traditional solutions primarily compensate for these high-temperature limitations by forming a high-temperature-resistant second phase precipitation, for example: CN119392053A discloses a high-strength, high-toughness, and high-temperature resistant Al-Si-Cu-Mg aluminum alloy, its preparation method, and its application. The preparation method includes the following steps: (1) According to the component ratio, the raw materials are preheated and dried, and then the preheated raw materials are added to the melting equipment in sequence, heated and melted, and stirred evenly to obtain an alloy melt; (2) The alloy melt is refined and modified; (3) The refined alloy melt is shaped and processed to obtain an aluminum alloy blank product; (4) The obtained aluminum alloy blank product is subjected to T6 heat treatment to obtain a high-strength, high-toughness, and high-temperature resistant Al-Si-Cu-Mg aluminum alloy. The T6 heat treatment process includes: a solution temperature of 480-550℃, a holding time of 8-16 hours, quenching in water after solution treatment, a quenching temperature of 50-80℃, an artificial aging temperature of 160-230℃, a holding time of 4-8 hours, and cooling to room temperature with the furnace. The heat treatment process of solution treatment, quenching and artificial aging significantly improves the strength and toughness of Al-Si-Cu-Mg aluminum alloy at 200℃. The tensile strength at 200℃ is ≥280MPa, the yield strength is ≥250MPa, and the elongation after fracture is 6.0-15.0%.

[0003] CN118773491A discloses a heat-resistant aluminum-silicon alloy material and its preparation method. The heat-resistant aluminum-silicon alloy material includes an Al-12Si-1Cu-1Ni-1Mg matrix alloy and red mud chemically coated with Ni. By mass percentage, the red mud chemically coated with Ni is 0.5wt.%~2wt.%, and the Al-12Si-1Cu-1Ni-1Mg alloy is 98wt.%~99.5wt.%. The preparation method specifically includes the following steps: S1: Chemically coating the red mud after magnetically removing iron(III) oxide with Ni; S1-1: Drying the red mud after magnetically removing iron(III) oxide, grinding it, adding it to a NiSO4 solution for ultrasonic dispersion, stirring, filtering, and drying; S1-2: Grinding the red mud obtained in S1-1, then adding it to a mixed solution of NaBH4, NaOH, and C6H5Na3O7 at 50℃, stirring, filtering, and washing with deionized water. S1: Drying yields Ni-coated red mud; S2: Blocky aluminum-silicon alloy, aluminum-copper alloy, aluminum-nickel alloy, and aluminum-magnesium alloy are cut into small pieces in a machine tool and then dried for later use; S3: Industrial pure aluminum is placed in a graphite crucible and heated and melted in an electromagnetic induction furnace. Aluminum-silicon alloy, aluminum-copper alloy, and aluminum-nickel alloy are added to the melt, and after standing and holding at a certain temperature, the mixture is stirred and slag is removed; S4: After adjusting the temperature, aluminum-magnesium alloy is pressed into the bottom of the melt obtained in S3. After holding at a certain temperature, a refining agent is added, and after all raw materials are melted, the mixture is removed. S5: Add the Ni-coated red mud obtained in S1 while stirring, adjust the temperature and remove the slag to obtain an Al-12Si-1Cu-1Ni-1Mg / red mud alloy melt; S6: Pour the Al-12Si-1Cu-1Ni-1Mg / red mud alloy melt into a mold, demold to obtain an Al-12Si-1Cu-1Ni-1Mg / red mud alloy ingot; S7: Perform T6 heat treatment on the alloy material obtained in S6 to obtain the target product. After T6 heat treatment, the Vickers hardness of the heat-resistant aluminum-silicon alloy material increases from 175.97 HV to 210.51 HV, and the high-temperature tensile strength at 350℃ can reach 143.3 MPa.

[0004] CN117551920A discloses a high-temperature resistant, high-strength and high-toughness aluminum alloy for engine cylinder heads and its preparation method. The preparation method includes the following steps: S1 Preheating pure Al, pure Mg, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-titanium-boron master alloy, aluminum-strontium master alloy, and aluminum rare earth master alloy respectively; S2 Melting the preheated pure Al, then raising the temperature to 680-700℃ and adding the preheated aluminum-silicon master alloy and aluminum-manganese master alloy for melting, until the master alloys are completely melted. Then, the temperature is lowered to 620-650℃, and preheated pure Mg, aluminum-titanium-boron master alloy, aluminum-strontium master alloy, and aluminum-rare earth master alloy are added until completely melted; S3, the melt is heated to 660-680℃, a refining agent is added, and it is held at this temperature; S4, the melt after holding at this temperature is placed in a rotary degasser for degassing and refining. After refining, impurities on the surface of the melt are removed, and it is held at this temperature to obtain a casting blank; S5, the obtained casting blank is poured, solution-treated, quenched, aged, and then cooled to obtain the final product. This patent refines the grains and Si phase by adding 0-0.5wt.% rare earth elements, strengthens grain boundaries, eliminates Fe-rich phases, and improves high-temperature resistance. Its Al-Si alloy exhibits a significant increase in high-temperature tensile strength, reaching 339MPa at 25℃, 235MPa at 250℃, and 185MPa at 300℃.

[0005] However, the aforementioned processes are insufficient to achieve adequate refinement of the Al-Si alloy microstructure. The Al-Si alloys produced by these processes exhibit coarse primary Si and eutectic Si, which is extremely detrimental to the mechanical properties of the coating, easily causing matrix fracture and promoting crack propagation. Furthermore, the Al matrix softens and the strengthening effect of the Si phase decreases above 200℃, limiting the application of Al-Si alloys at high temperatures. In particular, rapidly solidified Al-Si alloys contain various metastable structures such as supersaturated solid solutions, nano-Si second phases, and amorphous materials. Under heat input, the Si phase coarsens, significantly reducing the strengthening effect of the alloy. Existing technologies, by adding high-temperature strengthening phases to Al-Si alloys, compensate for the decrease in high-temperature strength, but this only slows down the decline and does not fundamentally solve the problems of Si phase coarsening and Al matrix softening.

[0006] In summary, there is a need to develop a new high-silicon aluminum alloy coating that exhibits excellent high-temperature performance, enabling it to operate for extended periods at 300°C without a significant decrease in mechanical properties compared to room temperature. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-silicon aluminum alloy coating, its preparation method, and its application. The high-silicon aluminum alloy coating provided by this invention has a pseudo-eutectic structure, in which the Si phase is nanoscale in size. The nanoscale refined and dispersed Si phase fully exerts the strengthening effect of the Si strengthening phase, avoiding the coarse Si phase from cutting the matrix and causing crack initiation in conventional cast aluminum-silicon alloys. This fully enhances the mechanical properties of the high-silicon aluminum alloy coating, ultimately resulting in high-temperature performance of the high-silicon aluminum alloy, as well as high microhardness and average tensile bond strength at room temperature.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-silicon aluminum alloy coating, wherein the high-silicon aluminum alloy coating has a pseudo-eutectic structure; The pseudo-eutectic structure includes featureless regions; The size of the Si phase in the featureless region is 20~80nm.

[0009] The size of the Si phase in the featureless region is 20~80nm, for example, it can be 20nm, 40nm, 50nm, 60nm or 80nm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0010] Existing casting processes struggle to achieve sufficient microstructure refinement in Al-Si alloys, resulting in coarse primary and eutectic Si phases that negatively impact coating mechanical properties, easily cleaving the matrix and promoting crack propagation. This invention addresses this by creating a pseudo-eutectic structure in the high-silicon aluminum alloy coating, controlling the Si phase size to the nanometer scale. The nanometer-scale refined and dispersed Si phase fully leverages the strengthening effect of the Si reinforcing phase, thus significantly enhancing the mechanical properties of the high-silicon aluminum alloy coating. The high-silicon aluminum alloy coating of this invention exhibits high microhardness and average tensile bond strength at room temperature, along with excellent high-temperature thermal stability.

[0011] It should be noted that the matrix element in the high-silicon aluminum alloy coating of this invention is aluminum, and the mass percentage of silicon exceeds 25%.

[0012] It should be noted that the featureless region in this invention refers to the region that appears as a continuous, uniform, and consistent bright or dark band when observed under a scanning electron microscope. Typical solidification structures such as equiaxed crystals, columnar crystals, and dendritic crystals are not visible, nor are second-phase particles.

[0013] As a preferred technical solution of the present invention, the material of the high-silicon aluminum alloy coating includes an alloy composed of aluminum, silicon and cerium.

[0014] Preferably, the mass percentage of aluminum in the high-silicon aluminum alloy coating is 52-73%, for example, it can be 52%, 55%, 60%, 65% or 73%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] Preferably, the mass percentage of silicon in the high-silicon aluminum alloy coating is 25-40%, for example, it can be 25%, 30%, 35% or 40%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] Preferably, the mass percentage of cerium in the high-silicon aluminum alloy coating is 2-8%, for example, it can be 2%, 4%, 6% or 8%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] This invention limits the materials used in the high-silicon aluminum alloy coating and restricts the mass percentage of each element in the material. This results in a high-silicon aluminum alloy coating with high microhardness and average tensile bond strength at room temperature, as well as good high-temperature thermal stability. If the mass percentage of silicon is less than 25%, the lattice distortion effect of Si in the supersaturated solid solution and the strengthening effect of the nano-Si phase cannot be fully utilized. If the mass percentage of silicon is greater than 40%, the Si phase content will be too high, resulting in insufficient melting of the high-silicon aluminum alloy coating and low bonding strength. If the mass percentage of cerium is less than 2%, the segregation layer width will be insufficient and the high-temperature stability will be poor. If the mass percentage of cerium is greater than 8%, the formation of unfavorable phases will occur and the mechanical properties will decrease.

[0018] Preferably, the thickness of the high-silicon aluminum alloy coating is 100~400μm, for example, it can be 100μm, 200μm, 300μm or 400μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] As a preferred embodiment of the present invention, the microhardness of the high-silicon aluminum alloy coating is 300~400 HV. 0.2 For example, it could be 300HV 0.2 320HV 0.2 340HV 0.2 360HV 0.2 380HV 0.2 Or 400HV 0.2 However, this does not apply to all values ​​listed above; other unlisted values ​​within the range of values ​​mentioned above are also applicable.

[0020] Preferably, the nanohardness of the high-silicon aluminum alloy coating is 3~4 GPa, for example, it can be 3 GPa, 3.2 GPa, 3.4 GPa, 3.6 GPa, 3.8 GPa or 4 GPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0021] Preferably, the elastic modulus of the high-silicon aluminum alloy coating is 80~90GPa, for example, it can be 80GPa, 82GPa, 84GPa, 86GPa, 88GPa or 90GPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] Preferably, the average tensile bond strength of the high-silicon aluminum alloy coating is 50~70MPa, for example, it can be 50MPa, 55MPa, 60MPa, 65MPa or 70MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] In this invention, the average tensile bond strength of the high-silicon aluminum alloy coating is 50~70MPa, indicating that the high-silicon aluminum alloy coating has high service reliability.

[0024] In a second aspect, the present invention provides a method for preparing a high-silicon aluminum alloy coating according to the first aspect, the method comprising the following steps: (1) High-silicon aluminum alloy powder was sprayed onto the surface of an aluminum alloy substrate by supersonic plasma spraying to obtain a coating; (2) The coating is subjected to rapid heat treatment to obtain the high silicon aluminum alloy coating.

[0025] This invention first uses supersonic plasma spraying technology to spray high-silicon aluminum alloy powder onto the surface of an aluminum alloy substrate, resulting in a nanoscale pseudo-eutectic structure in the coating. Unlike the coarse polygonal Si phase in conventionally cast Al-Si alloys, the Si phase in the featureless region of the coating obtained by this invention has a size of 20~80nm, achieving sufficient refinement of the Si phase. Then, the Si phase in the coating is "strengthened" through rapid heat treatment. The rapid heat treatment process induces Ce grain boundary segregation, Si annealing twin formation, and Al grain boundary relaxation to suppress Si precipitation in Al-based supersaturated solid solutions, coarsening and morphological changes of nano-spherical Si, and suppress the formation of brittle and hard unfavorable phases. This achieves the stability of the metastable supersaturated solid solution and the nano-Si phase, thus preparing a high-silicon aluminum alloy coating with good high-temperature thermal stability.

[0026] It should be noted that the material of the aluminum alloy matrix in this invention includes any one of A383 aluminum-silicon alloy, A356 aluminum-silicon alloy, or 6061 aluminum-silicon alloy.

[0027] As a preferred technical solution of the present invention, the preparation method further includes sandblasting the aluminum alloy substrate before spraying to obtain a sandblasted substrate.

[0028] In this invention, the aluminum alloy substrate is sandblasted to remove oil and oxides from its surface.

[0029] Preferably, the abrasive used in the sandblasting process includes any one or at least two combinations of brown fused alumina, steel grit, or white fused alumina, wherein typical but non-limiting combinations include: a combination of brown fused alumina and steel grit, a combination of brown fused alumina and white fused alumina, a combination of steel grit and white fused alumina, and a combination of brown fused alumina, steel grit, and white fused alumina.

[0030] Preferably, the sandblasting pressure is 0.3~0.5MPa, for example, it can be 0.3MPa, 0.35MPa, 0.4MPa, 0.45MPa or 0.5MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the arithmetic mean surface roughness Sa of the substrate surface after sandblasting is 2~3μm, for example, it can be 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] As a preferred technical solution of the present invention, the preparation method further includes: before spraying, heating the sandblasted substrate to 80~120℃ using a plasma jet, for example, 80℃, 90℃, 100℃, 110℃ or 120℃, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0033] Before spraying, the present invention uses plasma jet to heat the sandblasted substrate to 80~120℃ to reduce the thermal stress between the coating and the substrate.

[0034] Preferably, the spraying current of the supersonic plasma spraying is 480~520A, for example, it can be 480A, 490A, 500A, 510A or 520A, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] Preferably, the spraying voltage of the supersonic plasma spraying is 110~130V, for example, it can be 110V, 115V, 120V, 125V or 130V, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, the spraying power of the supersonic plasma spraying is 50~70kW, for example, it can be 50kW, 55kW, 60kW, 65kW or 70kW, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] This invention limits the spraying power of supersonic plasma spraying to enable the coating to have a nanoscale pseudo-eutectic structure. If the spraying power is too low, the coating will not melt sufficiently, resulting in low bonding strength. If the spraying power is too high, Al will be over-melted, leading to Si phase growth and a decrease in coating toughness.

[0038] Preferably, the spraying distance of the supersonic plasma spraying is 90~110mm, for example, it can be 90mm, 95mm, 100mm, 105mm or 110mm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] This invention limits the spraying distance of supersonic plasma spraying to ensure that the coating has a nanoscale pseudo-eutectic structure. If the spraying distance is too small, the coating will not melt sufficiently; if the spraying distance is too large, the coating will not impact the substrate with enough force and will not spread sufficiently.

[0040] Preferably, the powder feed rate of the supersonic plasma spraying is 5~15g / min, for example, it can be 5g / min, 7g / min, 10g / min, 12g / min or 15g / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] This invention limits the amount of powder fed in supersonic plasma spraying to ensure that the coating has a nanoscale pseudo-eutectic structure. If the amount of powder fed is too small, the coating forming efficiency will be too low. If the amount of powder fed is too large, the powder will be heated unevenly and the mechanical properties of the coating will decrease.

[0042] Preferably, the powder feeding gas pressure of the supersonic plasma spraying is 0.5~0.7MPa, for example, it can be 0.5MPa, 0.55MPa, 0.6MPa, 0.65MPa or 0.7MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the supersonic plasma spraying is performed under gas protection.

[0044] Preferably, during the supersonic plasma spraying, the front and back sides of the aluminum alloy substrate are cooled.

[0045] In this invention, applying 0.4 MPa of double-sided front and back cleaning air (compressed air) during spraying to cool the substrate can reduce dust pollution in the air and improve the quality of the sprayed coating.

[0046] Preferably, the protective gas used in the gas protection includes a primary protective gas and a secondary protective gas.

[0047] Preferably, the protective main gas includes argon and / or nitrogen.

[0048] Preferably, the protective secondary gas includes hydrogen and / or nitrogen.

[0049] Preferably, the flow rate of the protective main gas is 80~120L / min, for example, it can be 80L / min, 90L / min, 100L / min, 110L / min or 120L / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0050] Preferably, the flow rate of the protective secondary gas is 10~30L / min, for example, it can be 10L / min, 15L / min, 20L / min, 25L / min or 30L / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0051] As a preferred embodiment of the present invention, the high-silicon aluminum alloy powder comprises aluminum, silicon, and cerium.

[0052] Preferably, the mass percentage of aluminum in the high-silicon aluminum alloy powder is 52-73%, for example, it can be 52%, 55%, 60%, 65% or 73%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0053] Preferably, the mass percentage of silicon in the high-silicon aluminum alloy powder is 25-40%, for example, it can be 25%, 30%, 35% or 40%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0054] Preferably, the mass percentage of cerium in the high-silicon aluminum alloy powder is 2-8%, for example, it can be 2%, 4%, 6% or 8%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0055] Preferably, the preparation of the high-silicon aluminum alloy powder includes: mixing Al-50Si master alloy, Al-20Ce alloy and aluminum to obtain a first mixture, and subjecting the first mixture to gas atomization treatment to obtain the high-silicon aluminum alloy powder.

[0056] In this invention, the gas atomization process involves melting the first mixture using electrode induction heating of a vacuum induction gas atomization device. The droplets formed by the molten first mixture are then broken into fine droplets by impact with high-pressure inert gas. These small droplets are then allowed to fly and solidify in the atomization tower of the vacuum induction gas atomization device to obtain the high-silicon aluminum alloy powder.

[0057] Preferably, the average particle size D50 of the high-silicon aluminum alloy powder is 15~45μm, for example, it can be 15μm, 20μm, 25μm, 30μm, 40μm or 45μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0058] Preferably, the temperature of the gas atomization treatment is 750~850℃, for example, it can be 750℃, 780℃, 800℃, 820℃ or 850℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0059] Preferably, the pressure of the gas atomization treatment is 0.8~1MPa, for example, it can be 0.8MPa, 0.85MPa, 0.9MPa, 0.95MPa or 1MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] It should be noted that the time for atomization can be selected by those skilled in the art based on the preparation volume, and no specific limitation is made here.

[0061] As a preferred technical solution of the present invention, the temperature of the rapid heat treatment is 300~350℃, for example, it can be 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0062] Preferably, the heating rate of the rapid heat treatment is 80~120℃ / min, for example, it can be 80℃ / min, 90℃ / min, 100℃ / min, 110℃ / min or 120℃ / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0063] This invention controls the temperature and heating rate of rapid heat treatment to suppress the formation of brittle and undesirable phases, so that the size of the Si phase in the high-silicon aluminum alloy coating is at the nanoscale. If the temperature is too low, the Ce element will diffuse slowly, resulting in the formation of undesirable intermetallic compounds. If the temperature is too high, the Si phase will be coarse.

[0064] Preferably, the rapid heat treatment time is 30 to 120 minutes, for example, 30 minutes, 50 minutes, 60 minutes, 80 minutes, 100 minutes or 120 minutes, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0065] As a preferred technical solution of the present invention, the preparation method includes the following steps: (1) The aluminum alloy substrate is sandblasted to obtain a sandblasted substrate with an arithmetic mean surface roughness Sa of 2~3μm; (2) The Al-50Si master alloy, Al-20Ce alloy and aluminum are mixed for the first time to obtain the first mixture. The first mixture is subjected to gas atomization treatment at a temperature of 750~850℃ and a pressure of 0.8~1MPa to obtain high silicon aluminum alloy powder. (3) Under gas protection, the sandblasted substrate is heated to 80~120℃ by plasma jet, and high silicon aluminum alloy powder is sprayed onto the surface of the sandblasted substrate by supersonic plasma spraying to obtain a coating; wherein, the spraying current of supersonic plasma spraying is 480~520A, the spraying voltage is 110~130V, the spraying power is 50~70kW, the spraying distance is 90~110mm, the powder feeding rate is 5~15g / min, and the powder feeding gas pressure is 0.5~0.7MPa; (4) The coating is subjected to rapid heat treatment at a temperature of 300~350℃, a heating rate of 80~120℃ / min, and a time of 30~120min to obtain the high silicon aluminum alloy coating; There is no specific order between steps (1) and (2).

[0066] Thirdly, the present invention provides an application of the high-silicon aluminum alloy coating according to the first aspect, said high-silicon aluminum alloy coating being used in the automotive industry.

[0067] The high-silicon aluminum alloy coating of this invention exhibits high microhardness and average tensile bond strength at room temperature, as well as good high-temperature performance, and has broad application prospects in the automotive industry.

[0068] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention enables the high-silicon aluminum alloy coating to have a pseudo-eutectic structure and controls the size of the Si phase to the nanoscale. The nanoscale refined and dispersed Si phase can fully exert the strengthening effect of the Si strengthening phase, thereby fully enhancing the mechanical properties of the coating. The high-silicon aluminum alloy coating of this invention can achieve a microhardness of 310 HV at room temperature. 0.2The above properties include an average tensile bond strength of over 50 MPa, a nano-hardness of over 3.0 GPa, an elastic modulus of around 90 GPa, and good high-temperature thermal stability at 300℃. (2) The present invention uses supersonic plasma spraying technology combined with rapid heat treatment to prepare a high silicon aluminum alloy coating with good high temperature thermal stability. The preparation method provided by the present invention is simple, convenient and easy to scale up industrially. Attached Figure Description

[0069] Figure 1 This is a SEM image of the Al-33Si-4Ce alloy powder provided in Example 1.

[0070] Figure 2 This is a TEM image of the coating surface provided in Example 1.

[0071] Figure 3 This is a TEM image of the high-silicon aluminum alloy coating provided in Example 1. Detailed Implementation

[0072] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0073] The aluminum alloy matrix used in the following embodiments is A383 aluminum-silicon alloy. The above limitation is only for clearly illustrating the technical solution of the present invention and is not considered as a further limitation of the present invention.

[0074] Example 1 This embodiment provides a high-silicon aluminum alloy coating, which has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~45nm; the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0075] The material of the high-silicon aluminum alloy coating is an Al-33Si-4Ce alloy, that is, the mass percentages of aluminum, silicon and cerium in the high-silicon aluminum alloy coating are 63%, 33% and 4% respectively, and the thickness of the high-silicon aluminum alloy coating is 200μm.

[0076] The microhardness of the high-silicon aluminum alloy coating is 338.14 HV. 0.2 The nano-hardness is 3.5 GPa, the elastic modulus is 85 GPa, and the average tensile bond strength is 59 MPa.

[0077] This embodiment also provides a method for preparing a high-silicon aluminum alloy coating, the method comprising the following steps: (1) The aluminum alloy substrate was sandblasted with brown fused alumina to obtain a sandblasted substrate with an arithmetic mean surface roughness Sa of 2.5 μm; wherein the sandblasting pressure was 0.4 MPa. (2) The Al-50Si master alloy, Al-20Ce alloy and aluminum are mixed for the first time to obtain the first mixture. The first mixture is subjected to gas atomization treatment at a temperature of 800℃ and a pressure of 0.9MPa to obtain Al-33Si-4Ce alloy powder with an average particle size D50 of 30μm. (3) Under the protective gas of argon gas with a main protective gas flow rate of 100 L / min and hydrogen gas with a secondary protective gas flow rate of 20 L / min, the sandblasted substrate is heated to 100°C by plasma jet in the supersonic plasma spraying equipment, and then Al-33Si-4Ce alloy powder is sprayed onto the surface of the sandblasted substrate by supersonic plasma spraying to obtain a coating; and during the spraying process, 0.4 MPa of double-sided cleaning gas (compressed air) is applied to cool the front and back sides of the aluminum alloy substrate. The spraying current of the supersonic plasma spraying is 500 A, the spraying voltage is 120 V, the spraying power is 60 kW, the spraying distance is 100 mm, the powder feeding rate is 10 g / min, and the powder feeding gas pressure is 0.6 MPa. (4) The coating is subjected to rapid heat treatment at a temperature of 300℃, a heating rate of 80℃ / min, and a time of 120min to obtain the high silicon aluminum alloy coating; There is no specific order between steps (1) and (2).

[0078] The SEM image of the Al-33Si-4Ce alloy powder obtained in step (2) is shown below. Figure 1 As shown, from Figure 1 It can be seen that the Al-33Si-4Ce alloy powder exhibits a near-spherical morphology with uniform particle size; the TEM image of the coating obtained in step (3) is shown below. Figure 2 As shown, from Figure 2 It can be seen that the Si phase size is around 20 nm; the TEM image of the high-silicon aluminum alloy coating obtained in this embodiment is shown below. Figure 3 As shown, from Figure 3 It can be seen that there is obvious grain boundary segregation of Ce element, and the α-Al grain size is about 100nm.

[0079] Example 2 This embodiment provides a high-silicon aluminum alloy coating, which has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~40nm; the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0080] The material of the high-silicon aluminum alloy coating is Al-40Si-2Ce alloy, that is, the mass percentages of aluminum, silicon and cerium in the high-silicon aluminum alloy coating are 58%, 40% and 2% respectively, and the thickness of the high-silicon aluminum alloy coating is 100μm.

[0081] The microhardness of the high-silicon aluminum alloy coating is 350 HV. 0.2 The nano-hardness is 3.6 GPa, the elastic modulus is 90 GPa, and the average tensile bond strength is 50 MPa.

[0082] This embodiment also provides a method for preparing a high-silicon aluminum alloy coating, the method comprising the following steps: (1) The aluminum alloy substrate was sandblasted with steel shot to obtain a sandblasted substrate with an arithmetic mean surface roughness Sa of 3 μm; wherein the sandblasting pressure was 0.5 MPa. (2) The Al-50Si master alloy, Al-20Ce alloy and aluminum are mixed for the first time to obtain the first mixture. The first mixture is subjected to gas atomization treatment at a temperature of 750℃ and a pressure of 1MPa to obtain Al-40Si-2Ce alloy powder with an average particle size D50 of 15μm. (3) Under the protective gas of argon gas with a main protective gas flow rate of 80 L / min and hydrogen gas with a secondary protective gas flow rate of 30 L / min, the sandblasted substrate is heated to 80°C by plasma jet in the supersonic plasma spraying equipment. Then, Al-40Si-2Ce alloy powder is sprayed onto the surface of the sandblasted substrate by supersonic plasma spraying to obtain a coating. During the spraying process, 0.4 MPa of double-sided cleaning gas (compressed air) is applied to cool the front and back sides of the aluminum alloy substrate. The spraying current of the supersonic plasma spraying is 520 A, the spraying voltage is 130 V, the spraying power is 70 kW, the spraying distance is 90 mm, the powder feeding rate is 5 g / min, and the powder feeding gas pressure is 0.7 MPa. (4) The coating is subjected to rapid heat treatment at a temperature of 320°C, a heating rate of 100°C / min, and a time of 60 min to obtain the high-silicon aluminum alloy coating; There is no specific order between steps (1) and (2).

[0083] Example 3 This embodiment provides a high-silicon aluminum alloy coating, which has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 50~80nm; the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0084] The material of the high-silicon aluminum alloy coating is an Al-25Si-8Ce alloy, that is, the mass percentages of aluminum, silicon and cerium in the high-silicon aluminum alloy coating are 67%, 25% and 8% respectively, and the thickness of the high-silicon aluminum alloy coating is 400μm.

[0085] The microhardness of the high-silicon aluminum alloy coating is 310 HV. 0.2 The nanohardness is 3.0 GPa, the elastic modulus is 82 GPa, and the average tensile bond strength is 62 MPa.

[0086] This embodiment also provides a method for preparing a high-silicon aluminum alloy coating, the method comprising the following steps: (1) Aluminum alloy substrate was sandblasted with white corundum to obtain a sandblasted substrate with an arithmetic mean surface roughness Sa of 2 μm; wherein, the sandblasting pressure was 0.3 MPa. (2) The Al-50Si master alloy, Al-20Ce alloy and aluminum are mixed for the first time to obtain the first mixture. The first mixture is subjected to gas atomization treatment at a temperature of 850℃ and a pressure of 0.8MPa to obtain Al-25Si-8Ce alloy powder with an average particle size D50 of 45μm. (3) Under the protective gas of argon gas with a main protective gas flow rate of 120 L / min and hydrogen gas with a secondary protective gas flow rate of 10 L / min, the substrate after sandblasting is heated to 120°C by plasma jet in the supersonic plasma spraying equipment, and then Al-25Si-8Ce alloy powder is sprayed onto the surface of the substrate after sandblasting by supersonic plasma spraying to obtain a coating; and during the spraying process, 0.4 MPa of double-sided cleaning gas (compressed air) is applied to cool the front and back sides of the aluminum alloy substrate. The spraying current of the supersonic plasma spraying is 480A, the spraying voltage is 110V, the spraying power is 50kW, the spraying distance is 110mm, the powder feeding rate is 15g / min, and the powder feeding gas pressure is 0.5MPa. (4) The coating is subjected to rapid heat treatment at a temperature of 350°C, a heating rate of 120°C / min, and a time of 30min to obtain the high-silicon aluminum alloy coating; There is no specific order between steps (1) and (2).

[0087] Example 4 This embodiment provides a high-silicon aluminum alloy coating, which differs from Embodiment 1 only in that the rapid heat treatment temperature is adjusted from 300°C to 200°C, while all other aspects are the same as in Embodiment 1.

[0088] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~25nm, the Ce element segregation in the high-silicon aluminum alloy coating is insufficient, and the internal stress of the high-silicon aluminum alloy coating is relatively large.

[0089] Example 5 This embodiment provides a high-silicon aluminum alloy coating, which differs from Embodiment 1 only in that the rapid heat treatment temperature is adjusted from 300°C to 400°C, while all other aspects are the same as in Embodiment 1.

[0090] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure, with interconnected Si phases, coarse grains, and a Si phase size of about 300 nm, resulting in decreased mechanical properties.

[0091] Example 6 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that step (2) is adjusted to: mixing Al-50Si intermediate alloy, Cu, and Mg to obtain a first mixture, and then subjecting the first mixture to gas atomization treatment at a temperature of 800°C and a pressure of 0.9MPa to obtain Al-25Si-4Cu-1Mg alloy powder. All other steps are the same as in Embodiment 1.

[0092] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~25nm; the high-silicon aluminum alloy coating has a Si annealed twin structure.

[0093] Example 7 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the spraying power of the supersonic plasma spraying in step (3) is adjusted from 60kW to 30kW. All other aspects are the same as in Embodiment 1.

[0094] The high-silicon aluminum alloy coating obtained in this embodiment has a large number of unmelted Si phase regions, a porosity of 15%, and no Ce element segregation in the high-silicon aluminum alloy coating, and no Si annealed twin structure is formed.

[0095] Example 8 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the spraying power of the supersonic plasma spraying in step (3) is adjusted from 60kW to 100kW. All other aspects are the same as in Embodiment 1.

[0096] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 100~145nm, and the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0097] Example 9 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the spraying distance of the supersonic plasma spraying in step (3) is adjusted from 100mm to 80mm. All other aspects are the same as in Embodiment 1.

[0098] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 50~65nm, and the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0099] Example 10 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the spraying distance of the supersonic plasma spraying in step (3) is adjusted from 100mm to 120mm. All other aspects are the same as in Embodiment 1.

[0100] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 55~65nm, and the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0101] Example 11 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the powder feeding rate of the supersonic plasma spraying in step (3) is adjusted from 10g / min to 2g / min. All other aspects are the same as in Embodiment 1.

[0102] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~25nm, and the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0103] Example 12 This embodiment provides a high-silicon aluminum alloy coating. The only difference from Embodiment 1 is that the powder feeding rate of the supersonic plasma spraying in step (3) is adjusted from 10g / min to 20g / min. All other aspects are the same as in Embodiment 1.

[0104] The high-silicon aluminum alloy coating obtained in this embodiment has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~25nm, and the high-silicon aluminum alloy coating has Ce element segregation and Si annealed twin structure.

[0105] Comparative Example 1 This comparative example provides a high-silicon aluminum alloy coating, which differs from Example 1 only in that the preparation method does not include step (4), but is otherwise the same as Example 1.

[0106] The high-silicon aluminum alloy coating obtained in this comparative example has a pseudo-eutectic structure; the pseudo-eutectic structure includes a featureless region; the size of the Si phase in the featureless region is 20~25nm, the Ce element in the high-silicon aluminum alloy coating does not segregate, and no Si annealed twin structure is formed.

[0107] Comparative Example 2 This comparative example provides a high-silicon aluminum alloy coating, which differs from Example 1 only in that step (4) of the preparation method is adjusted to: heat treatment of the coating at a temperature of 300°C, a heating rate of 20°C / min, and a time of 120min to obtain the high-silicon aluminum alloy coating. Otherwise, it is the same as Example 1.

[0108] The high-silicon aluminum alloy coating obtained in this comparative example has an interconnected Si phase structure with coarse Si phase grains, approximately 500 nm in size.

[0109] The bonding strength of high-silicon aluminum alloy coatings was determined using the GB / T8642-2002 standard for testing tensile bonding strength of thermal spray coatings. Three sets of repeated tests were conducted under the same conditions, and the average value was calculated to obtain the average tensile bonding strength, so as to reduce the random error of bonding strength, ensure the repeatability of bonding strength, and avoid randomness.

[0110] The high-silicon aluminum alloy coatings obtained in Examples 1-12 and Comparative Examples 1-2 were tested as follows: (1) Thermal stability: The high-silicon aluminum alloy coating was heated to 300℃ in the furnace at a heating rate of 30℃ / min and held for 48h. The sample was then removed from the heat treatment furnace and the oxide film on the surface was removed by grinding and polishing. The size of the Si phase in the featureless region of the high-silicon aluminum alloy coating before and after processing was statistically analyzed by TEM HAADF images and corresponding EDS results. At least 20 Si particles were counted for each sample, and the average particle size was taken to ensure the accuracy of the test results. (2) Microhardness test: The test conditions are as follows: load 0.98N, holding time 15s, microhardness values ​​of 20 array points for each sample, and average value of 20 points; (3) Nanohardness and elastic modulus test: The test conditions are: maximum load is 500mN, loading and unloading rate is 1000mN / min, holding time is 10s, 5 points are selected for each sample and the average value of the 5 points is taken. The phase composition and mechanical properties of the high-silicon aluminum alloy coatings in each embodiment and comparative example before and after the thermal stability test were detected. The changes in phase composition and mechanical properties were obtained by subtracting the phase composition (or mechanical properties) of the high-silicon aluminum alloy coating before the thermal stability test from the phase composition (or mechanical properties) of the high-silicon aluminum alloy coating before the thermal stability test. The calculation results are shown in Table 1.

[0111] Table 1 The test results show that: (1) As can be seen from Examples 1 to 3, the present invention can achieve the segregation of Ce element and the formation of Si annealing twins through rapid heat treatment, so that the high-silicon aluminum alloy coating has excellent high-temperature stability. Taking Example 1 as an example, before and after the thermal stability test, the size of the Si phase in the featureless region of the high-silicon aluminum alloy coating was 20~45nm and 28~57nm, respectively, which confirms that its Si phase size stability is excellent at 300℃.

[0112] (2) As can be seen from Examples 1 and 4-5, the rapid heat treatment temperature in Example 1 is 300℃, the Si phase size of the high silicon aluminum alloy coating without feature regions is 20~45nm, and the microhardness is 338.14HV. 0.2 The nanoscale hardness is 3.5 GPa, the elastic modulus is 85 GPa, the average tensile bond strength is 59 MPa, and the size change of the Si phase in the characteristic region before and after the thermal stability test is +8~+12 nm, while the microhardness change is +0.6 HV. 0.2 The nanoscale hardness change was +0.1 GPa, and the elastic modulus change was -1.5 GPa. In Example 4, the rapid heat treatment temperature was 200℃, and the Si phase size in the featureless region of the prepared high-silicon aluminum alloy coating was 20~25 nm, with a microhardness of 325.47 HV. 0.2 The nanoscale hardness is 3.3 GPa, the elastic modulus is 84 GPa, the average tensile bond strength is 56 MPa, and the size change of the Si phase in the characteristic region before and after the thermal stability test is +25~+35 nm, while the microhardness change is -38 HV. 0.2 The nanohardness change was -0.6 GPa, and the elastic modulus change was -6 GPa. In Example 5, the rapid heat treatment temperature was 400℃, and the Si phase size in the featureless region of the prepared high-silicon aluminum alloy coating was 280~320 nm, with a microhardness of 256.83 HV. 0.2 The nanoscale hardness is 2.8 GPa, the elastic modulus is 88 GPa, the average tensile bond strength is 42 MPa, and the size change of the Si phase in the characteristic region before and after the thermal stability test is +180~+220 nm, while the microhardness change is -67 HV. 0.2The nano-hardness changed by -0.7 GPa, and the elastic modulus changed by -9 GPa. It can be seen that the rapid heat treatment temperature affects the segregation of Ce and the size of the Si phase in the coating. Too high a temperature will lead to the growth of the Si phase, while too low a temperature will result in insufficient segregation of Ce, ultimately affecting the high-temperature stability of the coating.

[0113] (3) As can be seen from Examples 1 and 6, the high-silicon aluminum alloy coating prepared by spraying Al-33Si-4Ce alloy powder in Example 1 has a Si phase size of 20~45nm without characteristic regions and a microhardness of 338.14HV. 0.2 The nanoscale hardness is 3.5 GPa, the elastic modulus is 85 GPa, the average tensile bond strength is 59 MPa, and the size change of the Si phase in the characteristic region before and after the thermal stability test is +8~+12 nm, while the microhardness change is +0.6 HV. 0.2 The nanoscale hardness change was +0.1 GPa, and the elastic modulus change was -1.5 GPa; In Example 6, Al-25Si-4Cu-1Mg alloy powder was sprayed to prepare a high-silicon aluminum alloy coating with Si phase size of 20-25 nm in the featureless region and a microhardness of 328.59 HV. 0.2 The nanoscale hardness is 3.4 GPa, the elastic modulus is 86 GPa, the average tensile bond strength is 54 MPa, and the size change of the Si phase in the characteristic region before and after the thermal stability test is +55~+70 nm, while the microhardness change is -83 HV. 0.2 The nano-hardness changed by -0.9 GPa, and the elastic modulus changed by -8 GPa. This demonstrates that the doping of the rare earth element Ce has a significant impact on the performance of the high-silicon aluminum alloy coating, directly affecting its high-temperature stability.

[0114] (4) As can be seen from Examples 1 and 7-8, the supersonic plasma spraying power in Example 1 was 60kW, the Si phase size of the coating without feature regions was 20~40nm, and the microhardness was 354.31HV. 0.2 The nanoscale hardness is 3.7 GPa, the elastic modulus is 82 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +8~+12 nm, and the microhardness change is +0.6 HV. 0.2 The nanoscale hardness changed by +0.1 GPa, and the elastic modulus changed by -1.5 GPa. In Example 7, the spraying power was 30 kW, and the prepared coating contained a large number of unmelted Si phase regions, with a porosity of 15% and a microhardness of 210.38 HV. 0.2 The nanoscale hardness is 2.3 GPa, the elastic modulus is 75 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +90~+110 nm, and the microhardness change is -54 HV. 0.2The nanoscale hardness change was -0.6 GPa, and the elastic modulus change was -9 GPa; in Example 8, the spraying power was 100 kW, and the prepared coating had a Si phase size of 90-130 nm in the featureless region and a microhardness of 305.72 HV. 0.2 The nanoscale hardness is 3.1 GPa, the elastic modulus is 86 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +90~+110 nm, and the microhardness change is -73 HV. 0.2 The nano-hardness change was -0.7 GPa, and the elastic modulus change was -11 GPa. It is evident that the spraying power affects the coating's melting degree and bonding strength. This invention, by limiting the spraying power, ensures the formation of a nanoscale Si phase in the coating and improves the high-temperature stability of the high-silicon aluminum alloy coating.

[0115] (5) As can be seen from Examples 1 and 9-10, in Example 1, the spraying distance was 100 mm, the Si phase size of the coating without feature regions was 20-40 nm, and the microhardness was 354.31 HV. 0.2 The nanoscale hardness is 3.7 GPa, the elastic modulus is 82 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +8~+12 nm, and the microhardness change is +0.6 HV. 0.2 The nanoscale hardness change was +0.1 GPa, and the elastic modulus change was -1.5 GPa; in Example 9, the spraying distance was 80 mm, and the Si phase size of the coating without characteristic regions was 45~60 nm, with a microhardness of 335.49 HV. 0.2 The nanoscale hardness is 3.4 GPa, the elastic modulus is 81 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +22~+30 nm, and the microhardness change is -30 HV. 0.2 The nanohardness change was -0.4 GPa, and the elastic modulus change was -3.5 GPa. In Example 10, the spraying distance was 120 mm, and the Si phase size of the coating without characteristic regions was 50-62 nm, with a microhardness of 328.64 HV. 0.2 The nanoscale hardness is 3.3 GPa, the elastic modulus is 82 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +28~+35 nm, and the microhardness change is -33 HV. 0.2 The nano-hardness change was -0.4 GPa, and the elastic modulus change was -5 GPa. It is evident that the spraying distance affects the degree of coating melting and bonding strength. This invention, by limiting the spraying distance, ensures the formation of a nanoscale Si phase in the coating and improves the high-temperature stability of the high-silicon aluminum alloy coating.

[0116] (6) As can be seen from Examples 1 and 11-12, in Example 1, the powder feeding rate was 10 g / min, the Si phase size of the coating without characteristic regions was 20-40 nm, and the microhardness was 354.31 HV. 0.2 The nanoscale hardness is 3.7 GPa, the elastic modulus is 82 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +8~+12 nm, and the microhardness change is +0.6 HV. 0.2 The nanoscale hardness changed by +0.1 GPa, and the elastic modulus changed by -1.5 GPa; in Example 11, the powder feed rate was 2 g / min, and the Si phase size in the featureless region of the prepared coating was 20-25 nm, with a microhardness of 351.27 HV. 0.2 The nanoscale hardness is 3.7 GPa, the elastic modulus is 83 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +10~+16 nm, and the microhardness change is -8 HV. 0.2 The nanohardness change was -0.1 GPa, and the elastic modulus change was -2 GPa; in Example 12, the powder feed rate was 20 g / min, and the Si phase size of the coating without characteristic regions was 20-30 nm, with a microhardness of 332.85 HV. 0.2 The nanoscale hardness is 3.4 GPa, the elastic modulus is 84 GPa, and for the final high-silicon aluminum alloy coating, the size change of the Si phase in the featureless region before and after the thermal stability test is +18~+25 nm, and the microhardness change is -35 HV. 0.2 The nano-hardness changed by -0.4 GPa, and the elastic modulus changed by -6 GPa. This shows that the powder feed rate affects the coating forming efficiency and melting degree; a low powder feed rate has little impact on the mechanical properties of the high-silicon aluminum alloy coating.

[0117] (7) As can be seen from Example 1 and Comparative Examples 1-2, rapid heat treatment is the key to ensuring the stable high-temperature performance of high-silicon aluminum alloy coatings. Comparative Example 1 did not undergo rapid heat treatment, and the prepared coating had a Si phase size of 20-25 nm without characteristic regions, no Ce element segregation, and no Si annealing twin structure. Before and after the thermal stability test, the microhardness of the coating was 354.31 HV. 0.2 and 274.31HV 0.2 Comparative Example 2 used a slow heat treatment with a heating rate of 20℃ / min. The Si phase in the prepared coating was interconnected, and the grains were coarse, with a size of about 500nm. Both lost their high-temperature stability. It can be seen that the coating and the matching rapid heat treatment process designed in this invention effectively stabilized the Si phase in the nano-Al-Si coating and improved the high-temperature stability of the mechanical properties of the high-silicon aluminum alloy coating.

[0118] In summary, this invention utilizes supersonic plasma spraying combined with rapid heat treatment to induce a pseudo-eutectic structure in the high-silicon aluminum alloy coating. Furthermore, the Si phase size is controlled at the nanoscale. The refined and dispersed nanoscale Si phase fully leverages the strengthening effect of the Si reinforcing phase, significantly improving the coating's mechanical properties. The high-silicon aluminum alloy coating of this invention achieves a microhardness of 310 HV at room temperature. 0.2 The average tensile bond strength can reach over 50 MPa, the nano hardness can reach over 3.0 GPa, the elastic modulus is about 90 GPa, and it has good high-temperature thermal stability at 300℃.

[0119] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A high-silicon aluminum alloy coating, characterized in that, The high-silicon aluminum alloy coating has a pseudo-eutectic structure; The pseudo-eutectic structure includes featureless regions; The size of the Si phase in the featureless region is 20~80nm.

2. The high-silicon aluminum alloy coating according to claim 1, characterized in that, The material of the high-silicon aluminum alloy coating includes an alloy composed of aluminum, silicon, and cerium. Preferably, the mass percentage of aluminum in the high-silicon aluminum alloy coating is 52-73%. Preferably, the mass percentage of silicon in the high-silicon aluminum alloy coating is 25-40%. Preferably, the mass percentage of cerium in the high-silicon aluminum alloy coating is 2-8%; Preferably, the thickness of the high-silicon aluminum alloy coating is 100~400μm.

3. The high-silicon aluminum alloy coating according to claim 1 or 2, characterized in that, The microhardness of the high-silicon aluminum alloy coating is 300~400 HV. 0.2 ; Preferably, the nanohardness of the high-silicon aluminum alloy coating is 3~4 GPa; Preferably, the elastic modulus of the high-silicon aluminum alloy coating is 80~90 GPa; Preferably, the average tensile bond strength of the high-silicon aluminum alloy coating is 50~70 MPa.

4. A method for preparing a high-silicon aluminum alloy coating according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) High-silicon aluminum alloy powder was sprayed onto the surface of an aluminum alloy substrate by supersonic plasma spraying to obtain a coating; (2) The coating is subjected to rapid heat treatment to obtain the high silicon aluminum alloy coating.

5. The preparation method according to claim 4, characterized in that, The preparation method further includes sandblasting the aluminum alloy substrate before spraying to obtain a sandblasted substrate; Preferably, the abrasive used in the sandblasting process includes any one or a combination of at least two of brown fused alumina, steel grit, or white fused alumina; Preferably, the sandblasting pressure is 0.3~0.5MPa; Preferably, the arithmetic mean surface roughness Sa of the substrate surface after sandblasting is 2~3μm.

6. The preparation method according to claim 5, characterized in that, The preparation method further includes: heating the sandblasted substrate to 80~120℃ using a plasma jet before spraying; Preferably, the spraying current of the supersonic plasma spraying is 480~520A; Preferably, the spraying voltage of the supersonic plasma spraying is 110~130V; Preferably, the spraying power of the supersonic plasma spraying is 50~70kW; Preferably, the spraying distance of the supersonic plasma spraying is 90~110mm; Preferably, the powder feeding rate of the supersonic plasma spraying is 5~15g / min; Preferably, the powder feeding gas pressure for the supersonic plasma spraying is 0.5~0.7MPa; Preferably, the supersonic plasma spraying is performed under gas protection; Preferably, during the supersonic plasma spraying, the front and back sides of the aluminum alloy substrate are cooled.

7. The preparation method according to any one of claims 4-6, characterized in that, The high-silicon aluminum alloy powder includes aluminum, silicon, and cerium. Preferably, the mass percentage of aluminum in the high-silicon aluminum alloy powder is 52-73%; Preferably, the mass percentage of silicon in the high-silicon aluminum alloy powder is 25-40%. Preferably, the mass percentage of cerium in the high-silicon aluminum alloy powder is 2-8%; Preferably, the preparation of the high-silicon aluminum alloy powder includes: mixing Al-50Si master alloy, Al-20Ce alloy and aluminum to obtain a first mixture, and subjecting the first mixture to gas atomization treatment to obtain the high-silicon aluminum alloy powder; Preferably, the average particle size D50 of the high-silicon aluminum alloy powder is 15~45μm; Preferably, the temperature of the gas atomization treatment is 750~850℃; Preferably, the pressure of the gas atomization treatment is 0.8~1MPa.

8. The preparation method according to any one of claims 4-7, characterized in that, The rapid heat treatment temperature is 300~350℃; Preferably, the heating rate of the rapid heat treatment is 80~120℃ / min; Preferably, the rapid heat treatment time is 30~120 min.

9. The preparation method according to any one of claims 4-8, characterized in that, The preparation method includes the following steps: (1) The aluminum alloy substrate is sandblasted to obtain a sandblasted substrate with an arithmetic mean surface roughness Sa of 2~3μm; (2) The Al-50Si master alloy, Al-20Ce alloy and aluminum are mixed for the first time to obtain the first mixture. The first mixture is subjected to gas atomization treatment at a temperature of 750~850℃ and a pressure of 0.8~1MPa to obtain high silicon aluminum alloy powder. (3) Under gas protection, the sandblasted substrate is heated to 80~120℃ by plasma jet, and high silicon aluminum alloy powder is sprayed onto the surface of the sandblasted substrate by supersonic plasma spraying to obtain a coating; wherein, the spraying current of supersonic plasma spraying is 480~520A, the spraying voltage is 110~130V, the spraying power is 50~70kW, the spraying distance is 90~110mm, the powder feeding rate is 5~15g / min, and the powder feeding gas pressure is 0.5~0.7MPa; (4) The coating is subjected to rapid heat treatment at a temperature of 300~350℃, a heating rate of 80~120℃ / min, and a time of 30~120min to obtain the high silicon aluminum alloy coating; There is no specific order between steps (1) and (2).

10. An application of the high-silicon aluminum alloy coating according to any one of claims 1-3, characterized in that, The high-silicon aluminum alloy coating is used in the automotive industry.

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