A method for manufacturing a high Nb-TiAl alloy turbocharger

Abstract

This disclosure discloses a method for manufacturing a high-Nb-TiAl alloy turbocharger, belonging to the field of turbocharger manufacturing technology. The manufacturing method includes: preparing high-Nb-TiAl alloy powder using a rotating electrode powder preparation method with integrated oxygen content control throughout the entire process; using a SEBM forming process to scan and melt the high-Nb-TiAl alloy powder layer by layer to form a high-Nb-TiAl alloy turbocharger; and subjecting the high-Nb-TiAl alloy turbocharger to heat treatment and fluorination. The high-Nb-TiAl alloy turbocharger manufacturing process employed in this disclosure can improve the uniformity of the alloy structure and grain size, reduce the weight of the turbocharger, improve the high-temperature creep performance of the turbocharger, enhance stability, further improve engine acceleration performance, reduce energy consumption and smoke, and prevent blade breakage failure at extremely high speeds.

Description

Technical Field

[0001] This disclosure belongs to the field of turbocharger manufacturing technology, specifically relating to a method for manufacturing a high Nb-TiAl alloy turbocharger. Background Technology

[0002] Turbochargers are mounted on the intake and exhaust manifolds of an engine, operating under extremely harsh conditions of high temperature, high pressure, and high speed. This results in demanding operating environments and stringent requirements, necessitating sophisticated material forming processes and processing techniques. The materials must possess excellent high-temperature mechanical properties, as well as good resistance to fatigue and creep.

[0003] The turbocharger turbine is a crucial and important component of a turbocharger. With the development of turbocharger technology, turbine materials are constantly being updated. Previously, 20Cr3MoWV(A) was commonly used in diesel engine turbocharger turbines. However, this material was only suitable for relatively large turbochargers operating at low speeds (around 40,000 r / min). As turbocharger speeds increase and their size decreases, and diesel engine exhaust temperatures sometimes exceed 750℃, this material no longer meets the requirements for turbocharger use. Currently, turbocharger turbines for general automobiles commonly use K418 nickel-based superalloy. Turbochargers made from this alloy have certain limitations, such as high processing difficulty, heavy weight, poor engine acceleration, high energy consumption, slow acceleration, and high smoke emissions. At high speeds, turbine blades often deform. Furthermore, nickel-based K418 alloys and other metal materials often accumulate carbon deposits on their surface, leading to dynamic imbalance at high speeds. Additionally, tiny carbon fragments that detach and impact the turbine blades at extremely high speeds can cause blade breakage and failure. Summary of the Invention

[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method for manufacturing a high Nb-TiAl alloy turbocharger.

[0005] This disclosure provides a method for manufacturing a high-Nb-TiAl alloy turbocharger, the method comprising:

[0006] High Nb-TiAl alloy powder was prepared using a rotating electrode powder preparation method with integrated oxygen content control technology throughout the entire process.

[0007] The high Nb-TiAl alloy powder is formed by layer-by-layer scanning melting using the SEBM forming process to create a high Nb-TiAl alloy turbocharger.

[0008] The high Nb-TiAl alloy turbocharger is subjected to heat treatment and fluorination.

[0009] Optionally, high Nb-TiAl alloy powder is prepared using a rotating electrode powder preparation method with integrated oxygen content control throughout the entire process, including:

[0010] Titanium, aluminum, and niobium metal powders are subjected to two consumable melting processes and one induction melting process to form an electrode rod, wherein the oxygen content of the electrode rod is below 500 ppm.

[0011] Under conditions where the oxygen content is less than 0.2 ppm, the electrode rod is crushed using a plasma rotating electrode powder making device, and the crushed powder is sieved and packaged under an argon atmosphere to form high Nb-TiAl alloy powder, wherein the oxygen content of the high Nb-TiAl alloy powder is less than 670 ppm.

[0012] Optionally, in the high Nb-TiAl alloy powder, the atomic ratio of titanium, aluminum and niobium is (40-50):(40-50):(4-10).

[0013] Optionally, the high Nb-TiAl alloy powder is Ti-45Al-8Nb alloy powder.

[0014] Optionally, the step of forming a high Nb-TiAl alloy turbocharger by layer-by-layer scanning melting of the high Nb-TiAl alloy powder using the SEBM forming process includes:

[0015] Preheat the substrate;

[0016] Powder is spread on the substrate according to the preset powder layer thickness, and the powder layer is preheated with preheating current to make the high Nb-TiAl alloy powder micro-sintered.

[0017] Selective melting of powder is performed to form a molten layer;

[0018] The molten layer is preheated a second time;

[0019] The process involves repeatedly spreading powder onto a substrate and scanning the molten powder layer by layer to form a high-Nb-TiAl alloy turbocharger.

[0020] Optionally, the substrate is preheated to 1100-1200℃ for 10-30 minutes; and / or,

[0021] The preheating temperature for the powder layer is 1100-1200℃; and / or,

[0022] The temperature for secondary preheating of the molten layer is 1100-1200℃.

[0023] Optionally, the process parameters for selective melting of the powder are as follows: melting current of 10-12.5 mA, electron beam scanning speed of 3.5-5 m / s, scanning interval of 100 μm, powder layer height of 40-60 μm, and density greater than 98%.

[0024] Optionally, the high Nb-TiAl alloy turbocharger is subjected to heat treatment, including:

[0025] The high Nb-TiAl alloy turbocharger was subjected to a first heat treatment at 1400-1500℃ for 20-40 minutes.

[0026] The high Nb-TiAl alloy turbocharger was subjected to a second heat treatment at 1300-1400℃ for 50-60 minutes.

[0027] The high Nb-TiAl alloy turbocharger was subjected to a third heat treatment at 900-1000℃ for 50-60 minutes.

[0028] Optionally, the high Nb-TiAl alloy turbocharger is subjected to a first heat treatment at 1450°C for 30 minutes.

[0029] The high Nb-TiAl alloy turbocharger was subjected to a second heat treatment at 1350℃ for 60 min.

[0030] The high Nb-TiAl alloy turbocharger was subjected to a third heat treatment at 950℃ for 60 minutes.

[0031] Optionally, the high-Nb-TiAl alloy turbocharger is subjected to fluorination treatment, including:

[0032] In a fluorine-containing electrolyte, a high Nb-TiAl alloy turbocharger is treated for 10-30 minutes using liquid-phase electrolytic plasma deposition technology to inject fluorine ions into the surface of the high Nb-TiAl alloy and grow an F-containing oxide film in situ.

[0033] Optionally, the fluorinated electrolyte comprises a first component and a second component; wherein,

[0034] The first component is sodium fluoride or potassium fluoride;

[0035] The second component is ethanol or ethylene glycol.

[0036] This disclosure proposes a method for manufacturing a high-Nb-TiAl alloy turbocharger, comprising: preparing high-Nb-TiAl alloy powder using a rotating electrode powder preparation method with integrated oxygen content control technology throughout the entire process; forming a high-Nb-TiAl alloy turbocharger by layer-by-layer scanning melting of the high-Nb-TiAl alloy powder using a SEBM forming process; and subjecting the high-Nb-TiAl alloy turbocharger to heat treatment and fluorination treatment. The alloy composition and manufacturing process used in this disclosure can improve the uniformity and size of the alloy structure, reduce the weight of the turbocharger, improve the high-temperature creep performance of the turbocharger, enhance stability, further improve engine acceleration performance, reduce energy consumption and smoke, and prevent blade breakage failure at extremely high speeds. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating a specific embodiment of the manufacturing method of a high Nb-TiAl alloy turbocharger according to this disclosure.

[0038] Figure 2 The XRD diffraction patterns of the high Nb-TiAl alloy turbocharger samples obtained under different forming parameters in Example 1 of this disclosure are as follows: (a) 10 mA; (b) 10.5 mA; (c) 11 mA; (d) 11.5 mA; (e) 12.5 mA.

[0039] Figure 3 The tensile fracture morphology of the high Nb-TiAl alloy turbocharger sample obtained in Example 1 of this disclosure under electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA is shown below; (ab) 10 mA-3.5 m / s; (cd) 11 mA-3.5 m / s;

[0040] Figure 4 The tensile stress-strain curves of the high Nb-TiAl alloy turbocharger specimens obtained in Example 1 of this disclosure under electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA are shown in (a) 10 mA - 3.5 m / s; (b) 11 mA - 3.5 m / s.

[0041] Figure 5 The creep results of the high Nb-TiAl alloy turbocharger sample obtained in Example 1 of this disclosure under the conditions of electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA are shown in (a) 10 mA-3.5 m / s; (b) 11 mA-3.5 m / s.

[0042] Figure 6 The engine acceleration curves for the high Nb-TiAl alloy turbocharger and the K418 alloy turbocharger of Embodiment 1 of this disclosure are shown.

[0043] Figure 7 The smoke opacity curves of the high Nb-TiAl alloy turbocharger and the K418 alloy turbocharger of Embodiment 1 of this disclosure are shown.

[0044] Figure 8 The fuel consumption conversion ratio for the high Nb-TiAl alloy turbocharger and K418 alloy turbocharger in water operation of Embodiment 1 of this disclosure;

[0045] Figure 9 For Comparative Example 1 of this disclosure, the tensile fracture morphology of high Nb-TiAl alloy samples was obtained under electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA; (ab) 10 mA-3.5 m / s; (cd) 11 mA-3.5 m / s;

[0046] Figure 10 For Comparative Example 1 of this disclosure, tensile stress-strain curves of high Nb-TiAl alloy samples were obtained under electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA; (a) 10 mA - 3.5 m / s; (b) 11 mA - 3.5 m / s;

[0047] Figure 11 For Comparative Example 1 of this disclosure, creep results of high Nb-TiAl alloy samples were obtained under electron beam scanning speed of 3.5 m / s and melting currents of 10 mA and 11 mA; (a)

[0048] 10mA-3.5m / s; (b) 11mA-3.5m / s. Detailed Implementation

[0049] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0050] like Figure 1 As shown, this disclosure provides a manufacturing method S100 for a high Nb-TiAl alloy turbocharger, specifically including the following steps S110 to S130:

[0051] S110. High Nb-TiAl alloy powder is prepared by using a rotating electrode powder preparation method and an integrated oxygen content control technology throughout the entire process.

[0052] Specifically, titanium, aluminum, and niobium metal powders are subjected to two consumable metal melting processes and one induction melting process to form electrode rods with an oxygen content below 500 ppm. Then, under conditions where the oxygen content is less than 0.2 ppm, the electrode rods are crushed using a plasma rotating electrode powder-making device. The crushed powder is then sieved and packaged under an argon atmosphere to form high-Nb-TiAl alloy powder with an oxygen content below 670 ppm. This embodiment, by controlling the oxygen content of the alloy powder, can reduce alloy defects, improve the alloy's strength and toughness, and ensure stable operation of components under high temperature and high pressure environments. Simultaneously, the low oxygen content helps reduce internal weak points in the alloy, making it less prone to fatigue cracking under cyclic loading, thereby improving fatigue resistance. This is particularly beneficial for aerospace components operating under alternating stress, extending their service life and reducing maintenance costs.

[0053] In some preferred embodiments, the temperature range for the two self-consumable melting processes is 1400-1600°C, and the temperature range for the one induction melting process is 1500-1650°C.

[0054] In some other preferred embodiments, the atomic ratio of titanium, aluminum and niobium in the high Nb-TiAl alloy powder is (40-50):(40-50):(4-10). For example, the high Nb-TiAl alloy powder is Ti-45Al-8Nb alloy powder. Of course, alloy powders with other atomic ratios can also be used, and there is no specific limitation on this.

[0055] Compared to the current use of K418 nickel-based superalloys in turbochargers, this embodiment uses Ti, Al, and Nb as turbocharger raw materials, which has advantages such as low density. This reduces the weight of rotating components in the turbocharger, lowers the moment of inertia during vehicle operation, and improves the turbocharger's response speed. This allows the engine to adjust the intake air volume more quickly under different operating conditions, improving power performance and fuel economy. Secondly, the high-Nb-TiAl alloy provides higher strength and rigidity, ensuring structural stability of components in the high-speed rotation and high-temperature, high-pressure working environment of the turbocharger. It can withstand greater pressure and stress, is less prone to deformation and damage, and improves the reliability and service life of the turbocharger.

[0056] S120: A high Nb-TiAl alloy turbocharger is formed by layer-by-layer scanning and melting of high Nb-TiAl alloy powder using the SEBM forming process.

[0057] Specifically, step S120 includes the following steps:

[0058] 1) Preheating the substrate, wherein the substrate preheating temperature is preferably 1100-1200℃, for example, 1100℃, 1150℃, 1200℃, etc., and the time is preferably 10-30min, for example, 10min, 20min, 30min, etc. Preheating the substrate gives the TiAl alloy turbocharger toughness and plasticity during the forming process; at the same time, it reduces thermal stress and prevents the generation of thermal cracks; preheating the substrate can also ensure that the initial powder layer is slightly melted, so that the initial powder layer is sintered steadily and will not cause "powder blowing" phenomenon due to the impact of electron beam.

[0059] 2) Powder is spread on the substrate according to a preset thickness, and the powder layer is preheated with a preheating current to micro-sinter the high Nb-TiAl alloy powder. The powder is spread on the substrate to a thickness of 40-60 μm, and the preheating temperature is 1100-1200℃. By preheating the high Nb-TiAl alloy powder during the powder spreading process, the micro-sintering of the high Nb-TiAl alloy powder reduces its fluidity and improves the stability of the powder bed. The slight sintering of the high Nb-TiAl alloy powder allows it to withstand the impact force of the electron beam before selective melting, further preventing powder blowing.

[0060] 3) Selective melting of high Nb-TiAl alloy powder to form a molten layer.

[0061] Specifically, based on the preset three-dimensional model of the turbocharger, the powder in the target area of ​​the powder layer is melted to ensure complete melting and dense layer-to-layer bonding without fusion defects. The process parameters for selective melting of high Nb-TiAl alloy powder are as follows: melting current of 10-12.5 mA, electron beam scanning speed of 3.5-5 m / s, scanning interval of 100 μm, powder layer height of 40-60 μm, and density of 98.05-99.89%.

[0062] In some preferred embodiments, the melting current is preferably 10mA, 10.5mA, or 11mA, within which powder blowing is minimal. The electron beam scanning speed is preferably 3.5m / s or 4m / s, as lower speeds are beneficial for forming well-formed lamellar structures.

[0063] 4) The molten layer is preheated a second time.

[0064] Specifically, after the melting scan is completed, the molten layer is preheated a second time using an electron beam. The temperature for the second preheating of the molten layer is 1100-1200℃ to reduce the cooling rate of the molten layer, avoid the formation of a temperature gradient difference, and the second preheating can also promote the stability of the powder layer during the next powder spreading.

[0065] 5) Repeat the process of spreading powder on the substrate and melting the powder layer by layer to form a high Nb-TiAl alloy turbocharger.

[0066] Specifically, steps 2) through 4) are repeated, with powder layer by layer being laid on the substrate and the predetermined area of ​​the powder layer being melted. After the molten layer is formed, powder is continued to be laid and melted on the molten layer, and the powder is laid and melted layer by layer until the desired high Nb-TiAl alloy turbocharger is formed. It should be understood that after selective melting, argon gas can be introduced into the chamber to accelerate the cooling rate of the formed part. After cooling to room temperature, the formed sample is removed from the chamber and the unmelted powder is removed.

[0067] This embodiment employs the SEBM forming process to scan and melt high Nb-TiAl alloy powder layer by layer to form a high Nb-TiAl alloy turbocharger. It can manufacture a turbine with a complex structure based on a three-dimensional model. By using a high-energy-density electron beam as a heat source, the alloy powder can be rapidly melted and solidified, achieving good metallurgical bonding between powder particles and forming a high-density microstructure without obvious defects. At the same time, it can also refine the grain structure, forming a fine and uniform grain structure, suppressing the formation of harmful phases, thereby improving the overall mechanical and high-temperature performance of the turbocharger.

[0068] S130, heat treatment and fluorination treatment of high Nb-TiAl alloy turbochargers.

[0069] Specifically, this embodiment employs a heat treatment process to obtain a uniformly distributed microstructure. The heat treatment process comprises three parts, as follows:

[0070] The high Nb-TiAl alloy turbocharger is subjected to a first heat treatment at 1400-1500℃ for 20-40 minutes. That is, the temperature is first heated to the β phase single-phase region and held for a short time, then cooled to cause the β→α phase transformation, and then cooled again to retain the α phase as much as possible.

[0071] The high Nb-TiAl alloy turbocharger was subjected to a second heat treatment at 1300-1400℃ for 50-60 minutes, followed by furnace cooling at 1350℃ to obtain a uniform lamellar structure.

[0072] The high Nb-TiAl alloy turbocharger was subjected to a third heat treatment at 900-1000℃ for 50-60 minutes.

[0073] The heat treatment process employed in this embodiment transforms the residual α phase in the high Nb-TiAl alloy into an ordered α2 phase (α→α2). The resulting lamellar structure consists of equiaxed and a small amount of columnar lamellars, with lamellar sizes ranging from 40 to 60 μm. Heat treatment eliminates the B2 phase, optimizing the microstructure of the SEBM-formed high Nb-TiAl alloy. The microstructure transforms from γ laths, B2 phase, and γ / α2 lamellae into a fine-grained, fully γ / α2 lamellar structure, with a reduced B2 phase content. This hinders dislocation movement and crack propagation, further enhancing the alloy's performance and optimizing its microstructure. The fully γ / α2 lamellar structure exhibits excellent high-temperature stability, maintaining good structure and properties even at high temperatures. Compared to structures containing the B2 phase, the γ / α2 lamellar structure is less prone to phase transformation and grain growth at high temperatures, effectively resisting high-temperature creep and oxidation, thereby improving the service life and reliability of the high Nb-TiAl alloy turbocharger at high temperatures. Secondly, the γ / α2 lamellar structure can form a denser oxide film, preventing further intrusion of corrosive media, thereby improving the corrosion resistance of the high Nb-TiAl alloy turbocharger and giving it better durability in harsh working environments. In other words, this embodiment, through further heat treatment of the high Nb-TiAl alloy turbocharger, helps to improve the microstructure, increase the strength and hardness of the turbocharger, improve mechanical properties, and prevent the high Nb-TiAl alloy turbocharger from oxidizing in high-temperature environments (e.g., 700°C).

[0074] Furthermore, the fluorination treatment of the high Nb-TiAl alloy turbocharger in this embodiment includes:

[0075] In a fluorinated electrolyte, a high-Nb-TiAl alloy turbocharger was treated for 10-30 minutes using liquid-phase electrolytic plasma deposition technology. Fluorine ions were injected into the surface of the turbocharger sample, resulting in the in-situ growth of an fluorine-containing oxide film. Fluorination treatment enhances the stability of the material structure, increasing the Al content on the alloy surface. High-temperature aluminum fluoride readily diffuses from pores or cracks to the alloy surface, undergoing oxidation to transform into Al₂O₃, continuously forming dense Al₂O₃ and improving oxidation resistance. This heat treatment improves the microstructure and reduces the B₂ phase content, further enhancing the material's structural stability and thus improving creep resistance. In other words, the presence of the fluorine-containing oxide film and Al₂O₃ strengthens the grain boundaries of the alloy. During creep, grain boundaries are prone to sliding and deformation; this oxide film hinders grain boundary sliding, improving their creep resistance. This enhances the overall creep performance of the high-Nb-TiAl alloy turbocharger, enabling it to more effectively resist creep deformation under long-term high temperature and stress.

[0076] In some preferred embodiments, the fluorinated electrolyte includes a first component and a second component; wherein the first component is sodium fluoride or potassium fluoride; and the second component is ethanol or ethylene glycol. For example, the fluorinated electrolyte is sodium fluoride and ethanol, sodium fluoride and ethylene glycol, potassium fluoride and ethanol, or potassium fluoride and ethylene glycol.

[0077] In this embodiment, fluorination treatment of the formed sample can form a fluoride film on the alloy surface, reducing the friction coefficient of the turbocharger during operation. For example, on the contact surfaces between the turbine and components such as bearings and seals, fluorination treatment can reduce friction loss and improve mechanical efficiency. Secondly, the fluoride film can fill the microscopic defects and pores on the alloy surface, making the surface smoother, reducing the generation and shedding of wear particles, while also improving structural stability, enhancing creep performance, and extending the service life of the high Nb-TiAl alloy turbocharger.

[0078] The manufacturing method of the high Nb-TiAl alloy turbocharger will be further explained below with reference to specific embodiments:

[0079] Example 1

[0080] This example demonstrates a high Nb-TiAl alloy turbocharger, comprising the following steps:

[0081] S1. Titanium, aluminum, and niobium metal powders are subjected to two consumable melting processes at 1500℃ and one induction melting process at 1550℃ to form an electrode rod with an oxygen content below 500ppm. Then, under the condition of oxygen content less than 0.2ppm, the electrode rod is crushed using a plasma rotating electrode powder making device. The crushed powder is then sieved and packaged under an argon atmosphere to form Ti-45Al-8Nb alloy powder with an oxygen content below 670ppm.

[0082] S2. Preheat the substrate at 1100℃ for 10 min. Spread the Ti-45Al-8Nb alloy powder from step S1 onto the substrate to a thickness of 50 μm. Preheat the spread powder layer at 1100℃ to completely melt the powder in the target area, ensuring dense layer-to-layer bonding without fusion defects. The process parameters for selective melting of the powder are as follows: melting current is 10 mA, 10.5 mA, 11 mA, 11.5 mA, and 12.5 mA sequentially; electron beam scanning speed is 3.5 m / s, 4.0 m / s, 4.5 m / s, and 5.0 m / s sequentially; scanning spacing is 100 μm; and powder layer height is 50 μm. The temperature for secondary preheating of the molten layer is 1100℃. Repeat the process of spreading and melting the powder layer onto the substrate multiple times to form a Ti-45Al-8Nb alloy turbocharger with a density of over 98%.

[0083] like Figure 2 As shown, the diffraction peaks of the samples formed under the above process parameters in this embodiment are all composed of the γ phase, α2 phase, and B2 phase, and no other phase peaks were detected. Among the samples with different beam currents, the strongest diffraction peak corresponds to γ ​​(111); at the position of 40.285°, the diffraction peak corresponds to the B2 phase (110), and the peak intensity of the samples obtained under the conditions of 10mA-11.5mA does not change significantly, while the diffraction peak intensity of the samples obtained under the beam current of 12.5mA suddenly increases; for the α2 phase, under the conditions of various beam currents and scanning speeds, the position and intensity of the diffraction peaks of the samples do not differ significantly, and the formed turbocharger sample is a Ti-45Al-8Nb alloy.

[0084] S3. The Ti-45Al-8Nb alloy turbocharger is subjected to a first heat treatment at 1450℃ for 30 minutes, a second heat treatment at 1350℃ for 60 minutes, and a third heat treatment at 950℃ for 60 minutes.

[0085] S4. In a fluorine-containing electrolyte, a Ti-45Al-8Nb alloy turbocharger is treated for 10 minutes using liquid-phase electrolytic plasma deposition technology to inject fluorine ions into the surface of the Ti-45Al-8Nb alloy, thereby growing an in-situ fluorine-containing oxide film. The electrolyte includes sodium fluoride and ethanol.

[0086] The tensile properties, port morphology, and creep of the samples were analyzed under the conditions of electron beam scanning speed of 3.5 m / s and melting current of 10 mA and 11 mA.

[0087] Specifically, such as Figure 3 As shown, a large number of stepped tear bridges were found on the fracture surface of the heat-treated sample. At the same time, the fracture mode of the whole lamellar structure after heat treatment is generally manifested as lamellar fracture and fracture along the lamellar layer. This phenomenon is generally related to the orientation of the lamellar layer and the direction of the tensile force axis. The fracture mode under the two processes of 10mA-3.5m / s and 11mA-3.5m / s is a mixed fracture along the lamellar layer and through the lamellar layer.

[0088] Specifically, such as Figure 4As shown, the tensile properties of the samples obtained under the above conditions at 700℃ were analyzed. The tensile strength of the Ti-45Al-8Nb alloy turbocharger obtained by the 10mA-3.5m / s process and after heat treatment reached 500.95MPa, and the elongation of the sample reached 8.12%. The tensile strength of the Ti-45Al-8Nb alloy turbocharger obtained by the 11mA-3.5m / s process and after heat treatment reached 482.2MPa, and the elongation reached 7.02%. Heat treatment alleviated the degradation behavior of the microstructure, resulting in equiaxed or columnar lamellar structures in the forming direction, and the absence of coarse γ-lamellae. Therefore, with the increase of lamellar structure and the decrease of other structures such as bimorphic structures after heat treatment, the strength of the sample decreased while the plasticity increased compared with that before heat treatment. This allows the turbocharger to better adapt to stress concentration and deformation during operation, avoid sudden brittle fracture, and improve reliability.

[0089] Specifically, such as Figure 5 As shown, the fluorinated turbocharger samples maintained a relatively short creep duration in the first stage. The samples obtained under 10 mA - 3.5 m / s conditions lasted approximately 100 hours, while those under 11 mA - 3.5 m / s conditions lasted approximately 130 hours. From the entry into the steady-state creep stage to 500 hours, there was no trend towards entering the acceleration stage. At this point, the creep value after 100 hours decreased. At 100 hours, the creep value of the sample obtained under 10 mA - 3.5 m / s conditions was 0.165%, while the creep value of the sample obtained under 11 mA - 3.5 m / s conditions was 0.242%. This may be due to pore defects causing a higher initial creep value compared to the dual-treatment 10 mA - 3.5 m / s condition, but lower than the 500-hour creep value of the sample in Comparative Example 1.

[0090] Furthermore, this embodiment compares and analyzes a Ti-45Al-8Nb alloy turbocharger formed under conditions of 10mA-3.5m / s with a conventional K418 turbocharger.

[0091] like Figure 6 As shown, compared to a diesel engine equipped with a K418 turbocharger, a certain type of diesel engine equipped with the Ti-45Al-8Nb alloy turbocharger of this embodiment has a 35% higher full-load acceleration. The engine based on the Ti-45Al-8Nb alloy turbocharger has higher acceleration, faster speed response, and higher efficiency.

[0092] like Figure 7 As shown, compared to a diesel engine equipped with a K418 turbocharger, a certain type of diesel engine equipped with the Ti-45Al-8Nb alloy turbocharger of this embodiment has a 0.2 Bordeaux reduction in steady-state smoke opacity.

[0093] like Figure 8As shown, compared to a diesel engine equipped with a K418 turbocharger, a certain type of diesel engine equipped with the Ti-45Al-8Nb alloy turbocharger of this embodiment has a fuel consumption that is 3 g / kW·h lower and an overall mechanical efficiency that is 1.5% higher.

[0094] In summary, the turbocharger manufactured using the alloy and process described in this embodiment can effectively reduce processing difficulty, reduce turbocharger weight, improve engine acceleration, reduce energy consumption and smoke emissions, and improve stability.

[0095] Comparative Example 1

[0096] The turbocharger manufacturing method of this comparative example is the same as that of Example 1, except that steps S3 and S4 are omitted, that is, the high Nb-TiAl alloy turbocharger is formed by SEBM forming process.

[0097] Similarly, the tensile properties, port morphology, and creep of the samples obtained in this comparative example with an electron beam scanning speed of 3.5 m / s and a melting current of 10 mA and 11 mA were analyzed.

[0098] Specifically, such as Figure 9 As shown, the fracture morphology of the untreated alloy sample exhibits brittle fracture characteristics, containing numerous small cleavage surfaces and tearing cracks. The fracture morphology of the sample obtained under the 10mA-3.5m / s condition shows some cleavage fractures through lamellar layers, some microcracks, and dimples. The overall fracture morphology appears as a smooth cross-section, and the fracture mode is brittle fracture. The fracture mode of the sample obtained under the 11mA-3.5m / s condition is also brittle fracture. The fracture morphology of the sample obtained under the 10mA-3.5m / s condition is different from that of the sample obtained under the 10mA-3.5m / s condition, with more microcracks. This indicates that the untreated sample is prone to brittle fracture.

[0099] Specifically, such as Figure 10 As shown, the tensile strength of the sample obtained under the condition of 10mA-3.5m / s reached 670.15MPa and the elongation of the sample reached 4.15%. The tensile strength of the sample obtained under the process of 11mA-3.5m / s reached 619.19MPa and the elongation reached 3.51%.

[0100] Specifically, such as Figure 11 As shown, the creep sludge of the sample obtained under 10mA-3.5m / s conditions was 0.204% after 100h, and the creep sludge of the sample obtained under 11mA-3.5m / s conditions was 0.202% after 100h. After a creep test at 500MPa for 500h, both samples maintained the first creep stage for 180h, and then entered a steady state. They did not show any tendency to enter the accelerated creep stage up to 500h.

[0101] In summary, a comparison between Comparative Example 1 and Example 1 shows that the SEBM-formed Ti-45Al-8Nb alloy turbocharger, after appropriate heat treatment, exhibits a microstructure dominated by equiaxed and columnar lamellar structures, with lamellar sizes generally ranging from 40 to 60 μm. This replaces the pre-heat-treatment microstructure of lamellar γ- and α2 grains along the forming direction, maintaining a consistent microstructure throughout. Furthermore, bright bands with alternating light and dark areas are formed at the boundaries of the lamellar structures, with contrasting structures in the dark areas. This demonstrates that controlling the heat treatment process can improve the uniformity, size, and elongation of the microstructure, thereby enhancing fatigue and vibration resistance. Secondly, a dense Al2O3 film was obtained on the sample surface through electrochemical fluorination. In contrast, the alloy surface without electrochemical fluorination first forms a loose TiO2 film, allowing O atoms to diffuse into the alloy interior through this film, exacerbating oxidation and negatively impacting structural stability. In other words, fluorination further improves the structural stability of TiAl alloys, ensuring both the reduction of initial creep to meet service requirements and the reduction of creep under long-term temperature and stress.

[0102] This disclosure proposes a method for manufacturing a high-Nb-TiAl alloy turbocharger, which has the following advantages over the prior art:

[0103] First, by adjusting the alloy composition, this disclosure forms a turbocharger with a high Nb-TiAl alloy composition, which can reduce the weight of the rotating parts of the turbocharger and reduce the moment of inertia, making the turbocharger respond more quickly and improving engine power performance and fuel economy. At the same time, the turbocharger of this alloy has higher strength and specific stiffness, and its structural stability is better when subjected to high-speed rotation and high temperature and pressure, making it less prone to deformation and damage.

[0104] Secondly, this disclosure utilizes the SEBM forming process to precisely scan and melt high Nb-TiAl alloy powder layer by layer based on a three-dimensional model, manufacturing complex shapes and structures, such as complex cooling channels and twisted blades. This facilitates the optimization of turbocharger performance and efficiency. By controlling the oxygen content during powder preparation, SEBM forming parameters, and subsequent heat treatment and fluorination, the microstructure and properties of the high Nb-TiAl alloy can be precisely controlled to meet the requirements of different operating conditions and reduce processing difficulty. In addition, through the synergistic effect of heat treatment and fluorination, the high-temperature oxidation resistance and creep resistance of the turbocharger can be improved, preventing deformation and extending its service life.

[0105] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for manufacturing a high Nb-TiAl alloy turbocharger, characterized in that, The manufacturing method includes: High Nb-TiAl alloy powder was prepared using a rotating electrode powder preparation method with integrated oxygen content control throughout the entire process, including: Titanium, aluminum, and niobium metal powders are subjected to two consumable melting processes and one induction melting process to form an electrode rod, wherein the oxygen content of the electrode rod is below 500 ppm. Under conditions where the oxygen content is less than 0.2 ppm, the electrode rod is crushed using a plasma rotating electrode powder-making device. The crushed powder is then sieved and packaged under an argon atmosphere to form high Nb-TiAl alloy powder. The oxygen content of the high Nb-TiAl alloy powder is less than 670 ppm. In the high Nb-TiAl alloy powder, the atomic ratio of titanium, aluminum, and niobium is (40-50):(40-50):(4-10). A high-Nb-TiAl alloy turbocharger is formed by layer-by-layer scanning melting of the high-Nb-TiAl alloy powder using the SEBM forming process, including: Preheat the substrate to a temperature of 1100-1200℃ for 10-30 minutes. Powder is spread on the substrate according to the preset powder layer thickness, and the powder layer is preheated with preheating current to make the powder micro-sinter; the preheating temperature of the powder layer is 1100-1200℃. Selective melting of high Nb-TiAl alloy powder was performed to form a molten layer; The molten layer is preheated a second time; the temperature for the second preheating of the molten layer is 1100-1200℃. The process of repeatedly spreading powder on a substrate and scanning the molten powder layer by layer was used to form a high Nb-TiAl alloy turbocharger. The high Nb-TiAl alloy turbocharger is subjected to heat treatment and fluorination treatment; wherein, Heat treatment includes: The high Nb-TiAl alloy turbocharger was subjected to a first heat treatment at 1400-1500℃ for 20-40 minutes. The high Nb-TiAl alloy turbocharger was subjected to a second heat treatment at 1300-1400℃ for 50-60 minutes. The high Nb-TiAl alloy turbocharger was subjected to a third heat treatment at 900-1000℃ for 50-60 minutes. Fluorination treatment includes: In a fluorine-containing electrolyte, a high Nb-TiAl alloy turbocharger is treated for 10-30 minutes using liquid-phase electrolytic plasma deposition technology to inject fluorine ions into the surface of the high Nb-TiAl alloy and grow an F-containing oxide film in situ.

2. The manufacturing method according to claim 1, characterized in that, The high Nb-TiAl alloy powder used is Ti-45Al-8Nb.

3. The manufacturing method according to claim 1, characterized in that, The process parameters for selective melting of powder are as follows: melting current is 10-12.5mA, electron beam scanning speed is 3.5-5m / s, scanning interval is 100μm, and powder layer height is 40-60μm.

4. The manufacturing method according to claim 1, characterized in that, The fluorinated electrolyte comprises a first component and a second component; wherein... The first component is sodium fluoride or potassium fluoride; The second component is ethanol or ethylene glycol.

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