Preparation method of high-strength composite metal turbocharger shell

Abstract

The invention discloses a preparation method of a high-strength composite metal turbocharger shell, and relates to the technical field of metal processing.The preparation method comprises the following steps that S1, nickel-based high-temperature alloy powder and yttrium oxide powder are evenly mixed and then put into a ball mill; s2, the mixed alloy powder is put into a vacuum induction melting furnace, aluminum-based intermediate alloy is added, and liquid metal is obtained; and S3, the liquid metal is poured into a mold, is taken out after being naturally cooled to the room temperature, and is subjected to heat treatment and surface coating treatment. The yttrium oxide powder is added, the function of improving the mechanical property of the turbocharger shell is achieved, yttrium oxide particles are dispersed and distributed in a casting, grain boundary slippage and dislocation movement are effectively hindered, and the yield strength, tensile strength and hardness of the turbocharger shell are improved; the yttrium oxide particles form a net structure, so that the overall performance of the turbocharger shell is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and specifically to a preparation method for a high-strength composite metal turbocharger housing. Background Art

[0002] A turbocharger is an air compressor that compresses air to increase the intake air volume. Since the turbocharger operates in harsh environments such as high temperature and high pressure, its housing needs to withstand the huge pressures from the turbine and the impeller, as well as the vibrations and impacts generated due to the engine operation. Therefore, the turbocharger housing must have high strength to resist the effects of these forces.

[0003] As a key component for protecting the internal mechanical structure, the turbocharger housing must have the characteristic of high strength. However, traditional turbocharger housing materials, such as cast iron and cast steel, although having a certain strength, are difficult to meet the increasingly demanding performance requirements. Therefore, a preparation method for a high-strength composite metal turbocharger housing is extremely important.

[0004] 1. Patent document CN115788941B discloses a drag reduction and heat insulation supercharger and its preparation method. The above patent realizes the reduction of heat loss of the supercharger, improves the supercharger efficiency, and further improves the engine thermal efficiency. However, the above patent cannot achieve the function of improving the mechanical properties of the turbocharger housing.

[0005] 2. Patent document CN108194148B discloses a preparation method for a highly reliable radial flow supercharger turbine impeller. The above patent realizes the improvement of the local strength performance of the turbine impeller and achieves the goal of improving reliability. However, the above patent cannot achieve the function of improving the quality of the turbocharger housing.

[0006] 3. Patent document CN104907492B discloses a manufacturing method for a double-layer wall hollow turbine blade. The above patent realizes the solution to the problems that the double-layer wall cooling channels and impact holes are difficult to form and the forming quality is poor in the traditional casting process. However, the above patent cannot achieve the function of improving the strength of the turbocharger housing.

[0007] 4. Patent document CN107983950B discloses a method for injection molding a high-strength supercharger turbine impeller. The above patent realizes the improvement of the mechanical properties of the turbine alloy. However, the above patent cannot achieve the function of improving the surface hardness of the turbocharger housing.

[0008] In summary, the above patent cannot achieve the function of improving the mechanical properties of the turbocharger housing, cannot achieve the function of improving the quality of the turbocharger housing, cannot achieve the function of improving the strength of the turbocharger housing, and cannot achieve the function of improving the surface hardness of the turbocharger housing, resulting in problems such as low service life, low qualification rate, and easy damage of the prepared turbocharger housing; Therefore, this application proposes a preparation method for a high-strength composite metal turbocharger housing that can achieve the function of improving the mechanical properties of the turbocharger housing, can achieve the function of improving the quality of the turbocharger housing, can achieve the function of improving the strength of the turbocharger housing, and can achieve the function of improving the surface hardness of the turbocharger housing. Summary of the Invention

[0009] The purpose of the present invention is to provide a preparation method for a high-strength composite metal turbocharger housing to solve the technical problems in the above background art that it cannot achieve the function of improving the mechanical properties of the turbocharger housing, cannot achieve the function of improving the quality of the turbocharger housing, cannot achieve the function of improving the strength of the turbocharger housing, cannot achieve the function of improving the surface hardness of the turbocharger housing, resulting in low service life, low qualification rate, and easy damage of the prepared turbocharger housing.

[0010] To achieve the above purpose, the present invention provides the following technical solution: A preparation method for a high-strength composite metal turbocharger housing, the preparation method includes the following steps: S1. Mixing and ball milling treatment: Mix nickel-based superalloy powder and 1wt% yttrium oxide powder evenly and put them into a ball mill. Introduce argon into the ball mill and carry out ball milling treatment for 6 - 24h, with a ball-to-material ratio of 6:1; S2. Alloy melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400°C. When all the raw material powders are completely melted, add 0.01wt% aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500°C, and keep it warm for 15min to obtain liquid metal; S3. Pouring and post-treatment: Pour the liquid metal from the melting furnace into a mold for pouring. The pouring temperature is 1500°C. After pouring, let the casting cool naturally in the mold to room temperature and then take it out. Carry out heat treatment and surface coating treatment on the casting to obtain a turbocharger housing.

[0011] Preferably, the preparation method of the aluminum-based master alloy containing titanium carbide and titanium boride in step S2 includes the following steps: Put aluminum powder, carbon nanotubes, titanium powder, and boron powder into a mixing container, use a mechanical stirring device to mix them evenly, put the mixed powder into a ball mill, and carry out ball milling treatment for 48h, with a ball-to-material ratio of 8:1; After the ball milling is completed, the powder is taken out of the ball mill, screened and impurity-removed. The processed powder is wrapped with aluminum foil, and the wrapped powder is put into a hydraulic press for pressing to obtain an alloy cylinder; The pressed alloy cylinder is coated with graphite paper and put into a graphite mold. The graphite mold is placed in a vacuum hot explosion furnace for heating and heat preservation to obtain an aluminum-based master alloy containing titanium carbide and titanium boride.

[0012] Preferably, the preparation method of the mold in step S3 includes the following steps: Prototype wax mold making: According to the design drawing of the turbocharger housing, a three-dimensional model of the turbocharger housing is constructed using three-dimensional modeling software, and the wax material is printed into a solid wax mold matching the model data by a 3D printer; Coating and sand sprinkling: Mix silica sol and refractory zircon sand to prepare a coating. The prepared coating is evenly coated on the surface of the wax mold. Before the coating dries, refractory zircon sand is sprinkled on it. The wax mold coated with the coating and sprinkled with sand is put into a drying chamber for drying to obtain a mold shell with a wax mold; Steam dewaxing: Step 2 is repeated 4 times to obtain a 4-layer mold shell with a wax mold. The mold shell with the wax mold is put into a steam dewaxing kettle, the dewaxing kettle is heated and steam is introduced. After dewaxing is completed, it is naturally cooled to room temperature, and the wax and other impurities remaining on the mold shell are cleaned up; Initial firing and mold preparation: The dewaxed mold shell is put into a furnace for heat treatment to obtain a mold.

[0013] Preferably, the heat treatment in step S3 includes the following steps: Clean the surface of the casting, remove the impurities on the surface of the casting, and perform drying treatment; Put the casting into a heat treatment furnace, slowly heat it to 1150 °C, keep it warm for 1.5 h, quickly take the casting out of the heat treatment furnace, and put the casting into cold water at 25 °C for rapid cooling.

[0014] Preferably, the surface coating treatment in step S3 includes the following steps: Put chromium carbide aluminum powder and aluminum-clad nickel powder into a ball mill, ball mill and mix for 20 min, the ball-to-material ratio is 10:1, put the mixed powder into an oven, and dry it at 80 °C for 1.5 h; Clean the casting after heat treatment, perform drying treatment and preheating treatment, the preheating temperature is 110 °C, send the mixed powder into a plasma spraying device, and evenly spray the powder on the surface of the casting through a spraying gun.

[0015] Preferably, the components of the nickel-based superalloy powder are calculated by mass percentage, including 0.05 wt% of carbon powder, 20 wt% of cobalt powder, 15 wt% of chromium powder, 2 wt% of tungsten powder, 0.02 wt% of zirconium powder, and the rest is nickel powder.

[0016] Preferably, the mass ratio of the aluminum powder, carbon nanotubes, titanium powder and boron powder is 12:1:(3 - 4):(3 - 4).

[0017] Preferably, the following steps are further included in the step S2: S21. Melt self-rotation and particle dispersion: During the heat preservation process, use the rotation device of the melting furnace to make the liquid metal generate self-rotation, and uniformly disperse the aluminum-based master alloy in the liquid metal.

[0018] Preferably, the following steps are further included in the step S3: S31. Use measuring tools and equipment to accurately measure the size and shape of the casting, and detect the size and shape.

[0019] Preferably, the step 2 further includes: grinding and polishing the coating on the surface of the casting.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By adding yttrium oxide powder, the present invention realizes the function of improving the mechanical properties of the turbocharger housing. The yttrium oxide particles are dispersed in the casting, effectively hindering grain boundary slip and dislocation movement, improving the yield strength, tensile strength and hardness of the turbocharger housing. During the preparation process of the turbocharger housing, the yttrium oxide particles form a network structure, enhancing the overall performance of the turbocharger housing; 2. By using silica sol and zircon sand to prepare the mold, the present invention reduces the sand sticking phenomenon during the casting process, improves the surface finish of the casting, reduces the defects on the surface of the casting, is conducive to the uniform distribution and adhesion of the coating, and improves the bonding force between the metal coating and the casting matrix, realizing the function of improving the quality of the turbocharger housing; 3. By adding an aluminum-based master alloy, the present invention realizes the function of improving the strength of the turbocharger housing. The aluminum-based master alloy containing titanium carbide and titanium boride can form fine compound particles during the melting process, promoting the formation of fine grains in the alloy liquid, thereby refining the grain structure, improving the mechanical properties of the casting. Titanium carbide and titanium boride have high hardness and corrosion resistance, which can enhance the corrosion resistance and wear resistance of the casting surface and extend the service life; 4. By performing metal coating treatment on the surface of the casting with chromium carbide aluminum powder and aluminum-coated nickel powder, the present invention realizes the function of improving the surface hardness of the turbocharger housing. Chromium carbide aluminum has excellent mechanical properties and can significantly improve the hardness and wear resistance of the housing surface. Aluminum-coated nickel powder has good self-bonding and spraying properties, ensuring a firm bond between the coating and the housing and improving the overall hardness. Description of the Drawings

[0021] Figure 1Schematic diagram of the preparation process of the turbocharger housing of the present invention; Figure 2 Schematic diagram of the preparation process of the aluminum-based master alloy of the present invention; Figure 3 Schematic diagram of the preparation process of the mold of the present invention; Figure 4 Schematic diagram of the heat treatment process of the present invention; Figure 5 Schematic diagram of the surface coating treatment process of the present invention; Figure 6 Schematic diagram of the yttrium oxide powder mixing and ball milling treatment process of the present invention; Figure 7 Schematic diagram of the alloy melting process of the present invention; Figure 8 Schematic diagram of the casting and post-treatment process of the present invention. Specific embodiments

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Example 1, please refer to Figure 1 、 Figure 6 、 Figure 7 and Figure 8 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method comprising the following steps: S1. Mixing and ball milling treatment: Mix nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly and put them into a ball mill. The components of the nickel-based superalloy powder are calculated by mass percentage, including 0.05 wt% carbon powder, 20 wt% cobalt powder, 15 wt% chromium powder, 2 wt% tungsten powder, 0.02 wt% zirconium powder, and the rest is nickel powder. Pass argon into the ball mill for ball milling treatment for 6-24 h, and the ball-to-material ratio is 6:1; S2. Alloy melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. When all the raw material powders are completely melted, add 0.01 wt% aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal; S3. Pouring and Post-treatment: Pour the liquid metal from the melting furnace into the mold for pouring. The pouring temperature is 1500 °C. After pouring, let the casting cool naturally in the mold to room temperature and then take it out. Perform heat treatment and surface coating treatment on the casting to obtain the turbocharger housing.

[0024] Furthermore, perform ball milling on the mixed nickel-based superalloy powder and yttrium oxide powder. The powder particles continuously collide and rub against the grinding balls in the ball mill and among themselves, causing the powder to be continuously rolled, crushed, and deformed, thereby refining the particles of the nickel-based superalloy powder and yttrium oxide powder, gradually reducing their particle size, which helps the uniform mixing and reaction of the raw materials during the subsequent melting process, improves the microstructure uniformity and mechanical properties of the casting; through ball milling, the surface energy of the powder particles increases, the activity improves, enhancing the density and strength of the casting. At the same time, the collision and friction during ball milling can make different types of powder particles mix more evenly, avoiding segregation or non-uniform composition during the melting process. Argon gas is introduced during ball milling to protect the powder. During the preparation process, the nickel-based superalloy powder, as the matrix material, has high strength, high heat resistance, and good corrosion resistance, improving the overall performance of the turbocharger housing. The introduction of yttrium oxide powder can inhibit the grain growth of the casting during melting and solidification, thereby refining the grain structure and improving the mechanical properties of the casting. In addition, the yttrium oxide powder forms a network structure in the casting, which can hinder the propagation of cracks, thereby improving the fracture toughness and fatigue resistance of the material, further enhancing the mechanical properties of the casting, increasing the toughness of the casting, enabling it to better absorb energy when subjected to external impact, thereby improving the impact resistance. At the same time, as a dispersion strengthening phase, after the nickel-based superalloy powder and yttrium oxide powder are mixed, the yttrium oxide particles are dispersed in the alloy, effectively hindering grain boundary slip and dislocation movement, thereby improving the strength of the casting. The high-temperature stability of the yttrium oxide particles enables them to maintain the strengthening effect on the casting at high temperatures.

[0025] Example 2, please refer to Figure 1 and Figure 2 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method comprising the following steps: S1. Put aluminum powder, carbon nanotubes, titanium powder and boron powder into a mixing container, where the mass ratio of aluminum powder, carbon nanotubes, titanium powder and boron powder is 12:1:4:4. Use a mechanical stirring device to mix them evenly. Put the mixed powder into a ball mill for ball milling treatment for 48 h with a ball-to-material ratio of 8:1. After the ball milling is completed, take out the powder from the ball mill, conduct screening and impurity removal treatment. Wrap the treated powder with aluminum foil, put the wrapped powder into a hydraulic press for pressing treatment to obtain an alloy cylinder. Use graphite paper to wrap the pressed alloy cylinder and put it into a graphite mold. Then put the graphite mold into a vacuum hot explosion furnace for heating and heat preservation to obtain an aluminum-based master alloy containing titanium carbide and titanium boride. S2. Mix nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly and put them into a ball mill. Pass argon into the ball mill for ball milling treatment for 6 - 24 h with a ball-to-material ratio of 6:1. Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. When all the raw material powders are completely melted, add 0.01 wt% aluminum-based master alloy containing titanium carbide and titanium boride. Heat the melting furnace to 1500 °C and keep it warm for 15 min. During the heat preservation process, use the rotating device of the melting furnace to make the liquid metal rotate by itself, so that the aluminum-based master alloy is evenly dispersed in the liquid metal to obtain liquid metal. S3. Pour the liquid metal from the melting furnace into a mold for casting. The casting temperature is 1500 °C. After the casting is completed, take out the casting from the mold after it is naturally cooled to room temperature. Conduct heat treatment and surface coating treatment on the casting to obtain a turbocharger housing.

[0026] Furthermore, by adding aluminum powder, carbon nanotubes, titanium powder and boron powder, titanium reacts with carbon to form titanium carbide, and at the same time titanium reacts with boron to form titanium boride. When the aluminum-based master alloy containing titanium carbide and titanium boride is added to the melting furnace, the aluminum-based master alloy containing titanium carbide and titanium boride can be used as a reinforcing phase to improve the strength and hardness of the turbocharger housing. The aluminum-based master alloy containing titanium carbide and titanium boride can form fine compound particles during the melting process. These particles have a high melting point and a low surface energy and can stably exist in the molten metal. These particles can act as crystal nuclei to promote the formation of fine grains in the molten metal, thereby refining the grain structure. The refined grains can increase the number of grain boundaries per unit volume, thereby enhancing the grain boundary strength. At the same time, the refined grains can effectively resist the action of external forces, reduce the generation and propagation of cracks, and thus improve the mechanical properties of the casting. The fine grains can be evenly distributed during the heat treatment process, making the tissue transformation during the heat treatment more uniform, thereby improving the heat treatment effect and further improving the mechanical properties of the casting. In addition, titanium carbide and titanium boride have high hardness and corrosion resistance, and their presence can enhance the corrosion resistance and wear resistance of the casting surface and extend the service life. During the smelting process, the smelting furnace is heated to 1500 °C and held for 15 minutes, which is beneficial to the full diffusion and reaction of elements in the liquid metal, forming a uniform organizational structure. Using the rotating device of the smelting furnace to make the liquid metal rotate by itself helps the strengthening phases in the aluminum-based master alloy to be evenly dispersed in the liquid metal, avoiding segregation and agglomeration. Through alloying, nickel-based superalloy powder, yttrium oxide powder and aluminum-based master alloy are combined into a composite metal material with high strength, high heat resistance and good corrosion resistance. By refining the grains and evenly dispersing the strengthening phases, the strength and toughness of the casting are improved, enabling it to withstand the high temperature and high pressure suffered by the turbocharger housing during operation, thereby increasing the service life of the turbocharger housing.

[0027] Example 3, please refer to Figure 1 and Figure 3 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method of the mold includes the following steps: Prototype wax mold making: According to the design drawing of the turbocharger housing, use three-dimensional modeling software to construct a three-dimensional model of the turbocharger housing, and print the wax material into a solid wax mold that matches the model data through a 3D printer; Coating and sand sprinkling: Mix colloidal silica and refractory zircon sand to prepare a coating, evenly coat the prepared coating on the surface of the wax mold, and sprinkle refractory zircon sand before the coating dries. Put the wax mold coated with the coating and sprinkled with sand into a drying chamber for drying to obtain a mold shell with a wax mold; Steam dewaxing: Repeat step 2 four times to obtain a 4-layer mold shell with a wax mold. Put the mold shell with the wax mold into a steam dewaxing kettle, heat the dewaxing kettle and introduce steam. After dewaxing is completed, cool it naturally to room temperature, and clean the wax and other impurities remaining on the mold shell; Initial firing and mold preparation: Put the dewaxed mold shell into a furnace for heat treatment to obtain a mold.

[0028] Furthermore, by injecting the molten metal into the mold, castings with the required shape and size are obtained, thus ensuring the accuracy and quality of the castings. High-quality molds can ensure that the surface finish and internal organizational structure of the castings meet the requirements, thereby improving the overall performance of the turbocharger housing; Colloidal silica can form a stable silicon network structure in a high-temperature environment, thereby enhancing the mechanical properties of the mold and enabling it to withstand the thermal shock during high-temperature smelting and pouring processes. Zircon sand has extremely high refractoriness and high-temperature resistance, which can effectively prevent the mold from deforming or being damaged at high temperatures, thereby ensuring the accuracy and quality of the castings. As a binder, colloidal silica can firmly bond refractory materials such as zircon sand together to form a high-strength mold structure.

[0029] Example 4, please refer to Figure 1 andFigure 4 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method comprising the following steps: S1. Mixing and ball milling treatment: Mix nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly and then put them into a ball mill. Introduce argon into the ball mill and conduct ball milling treatment for 6 - 24 h with a ball-to-material ratio of 6:1; S2. Alloy melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. When all the raw material powders are completely melted, add 0.01 wt% aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal; S3. Pouring and post-treatment: Pour the liquid metal from the melting furnace into a mold for pouring. The pouring temperature is 1500 °C. After pouring, let the casting cool naturally in the mold to room temperature and then take it out. Clean the surface of the casting to remove impurities on the surface of the casting, conduct drying treatment, put the casting into a heat treatment furnace, slowly heat it to 1150 °C, keep it warm for 1.5 h, quickly take the casting out of the heat treatment furnace, and put the casting into cold water at 25 °C for rapid cooling to obtain the turbocharger housing.

[0030] Furthermore, during the heat treatment process, the grains inside the metal will rearrange and grow, forming a more uniform and dense microstructure, adjusting the metal microstructure of the turbocharger housing, eliminating internal stresses and tissue defects generated during the casting process, thereby improving the overall stability of the turbocharger housing and enhancing the stability of the turbocharger housing in high-temperature and high-pressure environments.

[0031] Example 5, please refer to Figure 1 and Figure 5 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method comprising the following steps: S1. Mixing and ball milling treatment: Mix nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly and then put them into a ball mill. Introduce argon into the ball mill and conduct ball milling treatment for 6 - 24 h with a ball-to-material ratio of 6:1; S2. Alloy melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. When all the raw material powders are completely melted, add 0.01 wt% aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal; S3. Pouring and Post-treatment: Pour the liquid metal from the melting furnace into the mold for pouring. The pouring temperature is 1500 °C. After pouring, let the casting cool naturally in the mold to room temperature and then take it out. Conduct hot pressing treatment. Put chromium carbide aluminum powder and nickel-coated aluminum powder into a ball mill, ball mill and mix for 20 min with a ball-to-material ratio of 10:1. Put the mixed powder into an oven and dry it at 80 °C for 1.5 h. Clean the casting, conduct drying treatment and preheating treatment with a preheating temperature of 110 °C. Put chromium carbide aluminum powder and nickel-coated aluminum powder into a ball mill, ball mill and mix for 20 min with a ball-to-material ratio of 10:1. Put the mixed powder into an oven and dry it at 80 °C for 1.5 h. Feed the mixed powder into a plasma spraying device and evenly spray the powder on the surface of the casting through a spraying gun. Grind and polish the coating on the surface of the casting to obtain the turbocharger housing.

[0032] Furthermore, through ball milling treatment, the uniform mixing and refinement of chromium carbide aluminum powder and nickel-coated aluminum powder can be ensured, thereby improving the performance of the coating. Put the mixed powder into an oven to remove moisture and volatile substances in the powder and prevent defects from occurring during the spraying process. Before spraying, conduct preheating treatment on the turbocharger housing to reduce the thermal stress during spraying, thereby improving the bonding strength of the coating; the excellent chemical corrosion resistance of chromium carbide aluminum can protect the housing from being eroded by various corrosive media and improve the durability of the housing; the aluminum layer in the nickel-coated aluminum powder can form a dense oxide protective film to prevent the housing from oxidizing at high temperatures, thereby improving the oxidation resistance of the housing, and the nickel layer provides good wear resistance and thermal shock resistance and can resist wear and thermal stress caused by friction and temperature changes.

[0033] Example 6, please refer to Figure 1 and Figure 5 , a preparation method of a high-strength composite metal turbocharger housing, the preparation method comprising the following steps: S1. According to the design drawing of the turbocharger housing, use 3D modeling software to construct a three-dimensional model of the turbocharger housing. Print the wax material into a solid wax mold that matches the model data through a 3D printer. Mix silica sol and refractory zircon sand to prepare a coating. Uniformly coat the prepared coating on the surface of the wax mold. Before the coating dries, sprinkle refractory zircon sand. Put the wax mold coated with the coating and sprinkled with sand into a drying chamber for drying to obtain a mold shell with a wax mold. Repeat the operation to obtain a 4-layer mold shell with a wax mold. Put the mold shell with a wax mold into a steam dewaxing kettle, heat the dewaxing kettle and introduce steam. After dewaxing is completed, cool naturally to room temperature, clean the wax and other impurities remaining on the mold shell, and put the dewaxed mold shell into a furnace for heat treatment to obtain a mold; S2. Mix the nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly, then put them into a ball mill. Introduce argon gas into the ball mill and conduct ball milling for 6 - 24 h with a ball-to-material ratio of 6:1. Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. When all the raw material powders are completely melted, add 0.01 wt% aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal. S3. Pour the liquid metal from the melting furnace into a mold for casting. The casting temperature is 1500 °C. After casting, let the casting cool naturally to room temperature in the mold and then take it out. Conduct hot pressing treatment. Put chromium carbide aluminum powder and nickel-clad aluminum powder into a ball mill, ball mill and mix for 20 min with a ball-to-material ratio of 10:1. Put the mixed powder into an oven and dry it at 80 °C for 1.5 h. Conduct heat treatment on the casting, clean the heat-treated casting, conduct drying treatment and preheating treatment with a preheating temperature of 110 °C. Put chromium carbide aluminum powder and nickel-clad aluminum powder into a ball mill, ball mill and mix for 20 min with a ball-to-material ratio of 10:1. Put the mixed powder into an oven and dry it at 80 °C for 1.5 h. Feed the mixed powder into a plasma spraying device, and evenly spray the powder on the surface of the casting through a spraying gun. Grind and polish the coating on the surface of the casting to obtain a turbocharger housing.

[0034] Furthermore, silica sol has excellent bonding properties and can firmly bond refractory materials such as zircon sand together to form a smooth and firm mold surface. At the same time, zircon sand has high hardness and high wear resistance, can resist the erosion and wear of the molten metal on the mold surface during the casting process, and maintain the smoothness of the mold surface, making the prepared mold surface smooth and not easily worn. During the casting process, the smooth surface of the mold can reduce the friction between the casting and the mold, thereby reducing the surface roughness of the casting and improving the surface finish, and thus reducing defects on the casting surface, such as pores and slag inclusions. These defects will weaken the bonding force between the coating and the substrate, thereby improving the bonding force between the metal coating and the casting substrate. At the same time, the smooth surface is conducive to the uniform distribution and adhesion of the coating, improving the overall performance and durability of the coating. The good bonding between the coating and the casting substrate can enhance the spalling resistance, wear resistance and corrosion resistance of the coating, thereby improving the overall performance of the turbocharger housing.

[0035] Comparative Example 1, A preparation method of a high-strength composite metal turbocharger housing, the preparation method includes the following steps: S1. Mixing and ball milling treatment: Put the nickel-based superalloy powder into a ball mill, introduce argon gas into the ball mill, conduct ball milling for 6 - 24 h with a ball-to-material ratio of 6:1; S2. Alloy Melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. After all the raw material powders are completely melted, add an aluminum-based master alloy containing 0.01 wt% titanium carbide and titanium boride, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal; S3. Pouring and Post-treatment: Pour the liquid metal from the melting furnace into a mold for pouring. The pouring temperature is 1500 °C. After pouring, let the casting cool naturally to room temperature in the mold and then take it out. Clean the surface of the casting to remove impurities on the surface of the casting, and conduct a drying treatment. Put the casting into a heat treatment furnace, slowly heat it to 1150 °C, keep it warm for 1.5 h, quickly take the casting out of the heat treatment furnace, and put the casting into cold water at 25 °C for rapid cooling to obtain a turbocharger housing.

[0036] Comparative Example 2. A preparation method of a high-strength composite metal turbocharger housing, characterized in that: the preparation method includes the following steps: S1. Mixing and Ball Milling Treatment: Mix the nickel-based superalloy powder and 1 wt% yttrium oxide powder evenly and then put them into a ball mill. Pass argon into the ball mill for ball milling treatment for 6 - 24 h, and the ball-to-powder ratio is 6:1; S2. Alloy Melting: Put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400 °C. After all the raw material powders are completely melted, heat the melting furnace to 1500 °C, and keep it warm for 15 min to obtain liquid metal; S3. Pouring and Post-treatment: Pour the liquid metal from the melting furnace into a mold for pouring. The pouring temperature is 1500 °C. After pouring, let the casting cool naturally to room temperature in the mold and then take it out. Conduct heat treatment and surface coating treatment on the casting to obtain a turbocharger housing.

[0037] Performance Testing Test 1 Tensile Strength Performance Test: Use the preparation methods of Example 1, Example 5, Example 6, and Comparative Examples 1 - 2 to prepare samples with dimensions of 8 mm × 4 mm × 2 mm, and use a universal material testing machine for testing. Record the tensile loads at the time of fracture of the samples at 25 °C and 800 °C; Test 2 Impact Strength Performance Test: Use the preparation methods of Example 1, Example 5, Example 6, and Comparative Examples 1 - 2 to prepare samples with dimensions of 10 mm × 10 mm × 50 mm, and use impact testing equipment for testing. Record the impact strength of the samples; Test 3 Hardness Performance Test: Use a HDX-1000 type microhardness tester to conduct microhardness testing on the samples prepared in Example 1, Example 5, Example 6, and Comparative Examples 1 - 2, and record the hardness values of the samples.

[0038] Table 1 Test Results of Tensile Strength Performance Test

[0039] Table 2 Test results of impact strength performance

[0040] Table 3 Test results of hardness performance

[0041] Working principle: The nickel-based superalloy powder has high-temperature strength and corrosion resistance. The addition of yttrium oxide powder improves the thermal stability and oxidation resistance of the material. The mixed powder is put into a ball mill, and argon is introduced to prevent the powder from oxidizing. During the ball milling process, the powder particles are gradually refined under the impact and shear of the grinding balls and the grinding tank, and a uniform mixing effect is achieved; The mixed alloy powder is put into a vacuum induction melting furnace, and the powder is melted by heating. The vacuum environment can prevent the metal from being oxidized and contaminated during the melting process. When the raw material powder is completely melted, an aluminum-based master alloy containing titanium carbide and titanium boride is added. These compounds can act as heterogeneous nucleating agents to promote the nucleation and refinement of crystals in the melt, thereby improving the mechanical properties and corrosion resistance of the material; The liquid metal is poured from the melting furnace into a mold. The smooth surface of the mold can reduce the friction between the casting and the mold, reduce the defects on the surface of the casting, and improve the bonding force between the metal coating and the casting substrate. The casting is heat-treated to eliminate internal stress and improve the mechanical properties of the material, and surface coating treatment is carried out to improve the corrosion resistance and wear resistance of the shell.

[0042] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A method for preparing a high-strength composite metal turbocharger housing, characterized in that: The preparation method comprises the following steps: S1. Mixing and ball milling: uniformly mix nickel-based high-temperature alloy powder and 1wt% yttrium oxide powder and put them into a ball mill. Then, introduce argon gas into the ball mill for ball milling for 6-24h, with a ball-to-material ratio of 6:

1. S2, alloy smelting: put the mixed alloy powder into a vacuum induction melting furnace, heat the melting furnace to 1400°C, and when all the raw material powders are completely melted, add 0.01wt% of aluminum-based master alloy containing titanium carbide and titanium boride, heat the melting furnace to 1500°C, and keep it warm for 15 minutes to obtain liquid metal; S3. Pouring and post-processing: Pour the liquid metal from the smelting furnace into the mold for pouring at a pouring temperature of 1500°C. After the pouring is completed, the casting is naturally cooled to room temperature in the mold and then taken out. The casting is heat treated and surface coated to obtain a turbocharger housing.

2. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The method for preparing the aluminum-based master alloy containing titanium carbide and titanium boride in step S2 comprises the following steps: Aluminum powder, carbon nanotubes, titanium powder and boron powder were placed in a mixing container and uniformly mixed using a mechanical stirring device. The mixed powders were placed in a ball mill for ball milling for 48 hours with a ball-to-material ratio of 8:

1. After the ball milling is completed, the powder is taken out from the ball mill, sieved and impurity-removed, the processed powder is wrapped with aluminum foil, and the wrapped powder is put into a hydraulic press for pressing to obtain an alloy cylinder; The pressed alloy cylinder is wrapped with graphite paper and placed in a graphite mold. The graphite mold is placed in a vacuum thermal explosion furnace for heating and heat preservation to obtain an aluminum-based master alloy containing titanium carbide and titanium boride.

3. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The method for preparing the mold in step S3 comprises the following steps: Prototype wax model production: According to the design drawings of the turbocharger housing, use 3D modeling software to build a 3D model of the turbocharger housing, and use a 3D printer to print the wax material into a solid wax model that matches the model data; Coating and sanding: Mix silica sol and refractory zircon sand to prepare coating, evenly coat the prepared coating on the surface of the wax model, and sprinkle refractory zircon sand before the coating dries. Put the wax model coated with coating and sanded into a drying room for drying to obtain a mold shell with wax model; Steam dewaxing: Repeat step 2 4 times to obtain a 4-layer mold shell with a wax pattern, put the mold shell with the wax pattern into a steam dewaxing kettle, heat the dewaxing kettle and pass steam, and after dewaxing is completed, cool it naturally to room temperature and clean up the wax and other impurities remaining on the mold shell; Initial firing and mold preparation: The dewaxed mold shell is placed in a furnace for heating treatment to obtain a mold.

4. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The heat treatment in step S3 includes the following steps: Clean the casting surface, remove impurities on the casting surface, and dry it; Place the casting in a heat treatment furnace, slowly heat it to 1150°C, keep it warm for 1.5 hours, quickly take the casting out of the heat treatment furnace, and quickly cool the casting in cold water at 25°C.

5. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The surface coating treatment in step S3 comprises the following steps: The chromium carbide aluminum powder and aluminum-coated nickel powder were placed in a ball mill and mixed for 20 minutes with a ball-to-material ratio of 10:

1. The mixed powder was placed in an oven and dried at 80°C for 1.5 hours. The casting after heat treatment is cleaned, dried and preheated at a temperature of 110°C. The mixed powder is sent to a plasma spraying device and the powder is evenly sprayed on the surface of the casting through a spray gun.

6. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The components of the nickel-based high-temperature alloy powder, calculated by mass percentage, include 0.05wt% carbon powder, 20wt% cobalt powder, 15wt% chromium powder, 2wt% tungsten powder, 0.02wt% zirconium powder, and the rest is nickel powder.

7. The method for preparing a high-strength composite metal turbocharger housing according to claim 2, characterized in that: The mass ratio of the aluminum powder, carbon nanotubes, titanium powder and boron powder is 12:1:(3-4):(3-4).

8. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The step S2 also includes the following steps: S21. Melt self-rotation and particle dispersion: During the heat preservation process, the rotating device of the melting furnace is used to make the liquid metal self-rotate, and the aluminum-based master alloy is evenly dispersed in the liquid metal.

9. The method for preparing a high-strength composite metal turbocharger housing according to claim 1, characterized in that: The step S3 also includes the following steps: S31. Use measuring tools and equipment to accurately measure the size and shape of castings and inspect the size and shape.

10. The method for preparing a high-strength composite metal turbocharger housing according to claim 5, characterized in that: The surface coating treatment also includes: grinding and polishing the coating on the surface of the casting.

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