Additive manufacturing of a precipitation strengthened high temperature alloy without hot cracking and method of making the same

Abstract

The present application relates to the technical field of additive manufacturing, and discloses an additive manufacturing heat-crack-free precipitation-strengthened high-temperature alloy and a preparation method thereof. The present application divides the layer into a plurality of mutually parallel scanning strips according to a preset translation direction and scanning strip interval, and performs strip scanning by means of laser self-rotation + translation motion coupling, thereby significantly enhancing the molten pool disturbance, realizing periodic shearing fracture of dendrite tips, breaking the columnar crystal epitaxial growth, realizing grain equiaxialization, and weakening anisotropy. In addition, the laser scanning is a high-speed scanning strategy with a translation speed greater than or equal to 1500 mm / s, shallow molten pools are formed by high-speed scanning, the surface tension in the shallow molten pool is utilized to strengthen the internal convection of the molten pool, the dendrites are refined, the formation of columnar crystals in the high-temperature alloy is further reduced, the anisotropy of mechanical properties is significantly eliminated, and the transverse strength and creep resistance under high temperature are improved. Equiaxed grains can effectively hinder the directional propagation of cracks along the columnar grain boundary, thereby significantly enhancing the fatigue life and damage tolerance.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and discloses an additive manufacturing method for a hot crack-free precipitation-strengthened high-temperature alloy and its preparation method. Background Technology

[0002] High-temperature alloys generally possess high strength, good resistance to oxidation and hot corrosion, excellent creep and fatigue resistance, and high reliability, making them widely used in the fabrication of hot-end components for advanced propulsion systems in aerospace, petrochemical, and other fields. The fabrication of complex high-temperature alloy components has become a key core technology in aerospace and other fields. However, existing high-temperature alloy component fabrication processes such as forging, powder metallurgy, and casting all have certain limitations in the fabrication of complex components. Laser Additive Manufacturing (LAM) technology utilizes the "discrete-stacking" principle to achieve direct manufacturing of parts from digital models to solid objects, greatly improving design freedom and becoming one of the key manufacturing technologies for complex components. However, during the laser additive manufacturing process, metal powder undergoes a series of complex and highly non-equilibrium phase changes, including melting, solidification, vaporization, and solid-state phase transitions. Furthermore, the high temperature gradient, high cooling rate, and cyclic heating-cooling effect can easily lead to large residual stresses, cracks, and other defects inside the printed part, significantly increasing the risk of fatigue failure during service. Currently, only a very few high-temperature alloys with excellent weldability, such as IN718, IN625, and Hastelloy X, can be guaranteed to remain crack-free during laser additive manufacturing. These alloys cannot generate a sufficient number of γ′ phases to strengthen the alloy, making it difficult to meet the high-temperature and high-stress service requirements above 800℃. While alloys with poor weldability, such as CM247LC, IN939, and IN738LC, may have a sufficient number of γ′ phases, they are highly prone to cracking during manufacturing, leading to a decline in their mechanical properties. This severely limits the application of these alloys in high-temperature components, especially failing to meet the requirements of critical components in aero-engines and gas turbines.

[0003] The core challenge of laser additive manufacturing lies in how to synergistically address the formability issues of high Al+Ti alloys and the microstructural inhomogeneities caused by refractory elements such as Mo, W, and Ta through process control. The extremely high temperature gradients and rapid cooling rates during laser additive manufacturing easily lead to hot cracks in the alloy at the end of solidification, especially when the total Al+Ti content exceeds 6%, resulting in a wide solidification range, long interdendritic liquid film retention time, and significantly increased crack susceptibility. This necessitates precise optimization of process parameters (such as laser power, scanning speed, and scanning strategy) to broaden the crack-free forming process window while ensuring melt pool stability and good formability. On the other hand, refractory elements (Mo, W, Ta) are prone to microscopic segregation during rapid non-equilibrium solidification, accumulating along interdendritic or grain boundaries, exacerbating microstructural inhomogeneity. The layer-by-layer epitaxial growth and repeated thermal cycling unique to additive manufacturing further intensify the anisotropy of element distribution and grain orientation. Although subsequent solution heat treatment aims to eliminate segregation, it is difficult to achieve complete rehomogenization due to the low diffusion rate of refractory elements, resulting in residual deposited crack defects or strong anisotropy in properties. Summary of the Invention

[0004] The purpose of this invention is to provide an additive manufacturing method for a hot-crack-free precipitation-strengthened high-temperature alloy and its preparation method. This method enables periodic shearing fracture of dendrite tips, interrupting the epitaxial growth of columnar crystals, achieving equiaxed grains, and reducing anisotropy. Furthermore, it utilizes surface tension in the shallow molten pool to enhance convection within the pool, refining dendrites and further reducing columnar crystal formation within the high-temperature alloy. This significantly eliminates anisotropy in mechanical properties and improves transverse strength and creep resistance at high temperatures. Simultaneously, equiaxed crystals effectively hinder crack propagation along the columnar grain boundaries, significantly enhancing fatigue life and damage tolerance, and comprehensively improving the reliability of the component during service.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a hot-crack-free precipitation-strengthened superalloy using additive manufacturing, comprising:

[0007] Based on the arrangement and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced ​​in the vertical direction; the laser scanning forming equipment is used to form a laser spot to melt the metal powder scanning area corresponding to each slice of the target part.

[0008] Following a bottom-up, layered slicing structure, powder is sequentially laid layer by layer in the forming chamber. The laser spot diameter is adjusted to a preset diameter using an electric beam expander. A laser rotation and translational motion coupled scanning method is employed to scan and melt the metal powder at each layer's processing location, completing the laser scanning forming of the target part. The laser rotation and translational motion coupled scanning method includes:

[0009] Each ply is divided into multiple parallel scanning strips according to a preset translation direction and a preset scanning strip interval. The laser spot has the same translation direction on each scanning strip of the same ply, and the translation speed is greater than or equal to 1500 mm / s.

[0010] On the same scanning strip, the laser spot rotates at the point on the center line of the scanning strip at the current scanning position to form a ring scanning area with a radius R. The radius R is 1 to 1.5 times the radius of the laser spot. After completing the self-rotation scanning of the current ring scanning area, it moves to the next ring scanning area, and the edges of the two adjacent ring scanning areas are tangent.

[0011] Furthermore, on the same scan strip, the dwell time of each annular scan area is based on... Analysis yielded, among which The dwell time for each annular scan region, The preset number of rotations for a single annular scan area. The preset translation speed for the scanning strip.

[0012] Furthermore, the scanning strips of adjacent layers are rotated by 67°; on the same scanning strip, the angle of the start and stop position of the next annular scanning area differs from the angle of the start and stop position of the previous annular scanning area by 67°.

[0013] Furthermore, the metal powder is prepared by atomizing a mixture containing C, Si, Cr, Co, Mo, Al, Ti, W, Ta, P, B, and Ni elements to obtain Ni-based high-temperature alloy powder with a hollow powder content of less than 3%; wherein, by mass percentage, the ratio of Ni:Co:Cr is (40-45):(21-25):(15-20), and the Al+Ti content is ≥7wt.%, with Ti / Al = 1-1.8.

[0014] Furthermore, it also includes:

[0015] Establish an analytical model for the average electron vacancy number of Ni-based superalloy powders based on elemental molar amounts and electron vacancies. ,in The average number of electron vacancies in Ni-based superalloy powder. For the first The number of electron vacancies in each element. For the first The molar content of each element;

[0016] Using the preset upper limit of the average number of electron vacancies in Ni-based superalloy powder as a constraint, the analysis model is used to perform optimization analysis on the mass percentage of each element in Ni-based superalloy powder, and the optimized value of the mass percentage of the corresponding element in Ni-based superalloy powder is obtained.

[0017] Furthermore, the constraints also include: the total content of Ta+W+Mo is <8 wt.%, wherein Ta ≤1.5 wt.%, W ≤6 wt.%, Mo ≤1.5 wt.%, and W / Ta >3 or W / Mo >3.

[0018] Furthermore, the constraints also include: the amount of B is 0.01 to 0.03 wt.%, the amount of P is 0.01 to 0.02 wt.%, and the amount of C is 0.05 to 0.1 wt.% by mass percentage.

[0019] Furthermore, after completing the laser scanning forming of the target part, the laser-scanned target part is heated in the range of 1150-1200℃ at a rate of 10℃ / min, held at that temperature for 4 hours, and then slowly cooled in stages; the first stage cooling rate is ≤7℃ / min to 1050℃, and held at that temperature for 4 hours; after the first stage cooling is completed, the second stage air cooling is carried out to 870℃ and held at that temperature for 16 hours, and the air cooling is then obtained.

[0020] To achieve the above-mentioned technical effects, the present invention also provides an additive manufacturing hot crack-free precipitation-strengthened high-temperature alloy, which is prepared by the aforementioned preparation method.

[0021] Compared with existing technologies, the beneficial effects of this invention are as follows: By dividing the layup into multiple parallel scanning strips according to a preset translational direction and a preset scanning strip interval, and performing strip scanning using a laser rotation + translational motion coupling method, this invention significantly enhances molten pool disturbance, achieves periodic shearing and fracture of dendrite tips, interrupts the epitaxial growth of columnar crystals, realizes equiaxed grains, and reduces anisotropy. Furthermore, the laser scanning employs a high-speed scanning strategy with a translational speed greater than or equal to 1500 mm / s. This high scanning speed is controlled to create a shallow molten pool, utilizing the surface tension within the shallow pool to enhance internal convection, refine dendrites, and further reduce the formation of columnar crystals in high-temperature alloys. This significantly eliminates anisotropy in mechanical properties and improves transverse strength and creep resistance at high temperatures. Simultaneously, equiaxed crystals effectively hinder crack propagation along the columnar grain boundaries, significantly enhancing fatigue life and damage tolerance, and comprehensively improving the reliability of the component during service. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the laser rotation and translational motion coupled scanning path in Examples 1 to 3;

[0023] Figure 2This is a diagram of the additive manufacturing depositional metallurgical microstructure in Example 2;

[0024] Figure 3 This is a morphology diagram of the additively manufactured deposited grains in Example 2;

[0025] Figure 4 This is a graph showing the grain aspect ratio analysis in Example 2;

[0026] Figure 5 This is a microstructure diagram after heat treatment in Example 2;

[0027] Figure 6 This is a morphological diagram of the γ′ phase in Example 2;

[0028] Figure 7 This is a comparative diagram of the deposited metallurgical microstructure in additive manufacturing.

[0029] Figure 8 This is a comparative example of the morphology of additively manufactured deposited grains.

[0030] Figure 9 This is a comparative diagram showing the aspect ratio analysis of additively manufactured deposited grains.

[0031] Figure 10 This is a comparative diagram of the microstructure of additive manufacturing heat treatment.

[0032] Among them, 1. Scanning strips. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0034] Example 1

[0035] See Figure 1 A method for preparing a hot-crack-free precipitation-strengthened superalloy using additive manufacturing, comprising:

[0036] Based on the arrangement and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced ​​in the vertical direction; the laser scanning forming equipment is used to form a laser spot to melt the metal powder scanning area corresponding to each slice of the target part.

[0037] Following a bottom-up, layered slicing structure, powder is sequentially laid layer by layer in the forming chamber. The laser spot diameter is adjusted to a preset diameter using an electric beam expander. A laser rotation and translational motion coupled scanning method is employed to scan and melt the metal powder at each layer's processing location, completing the laser scanning forming of the target part. The laser rotation and translational motion coupled scanning method includes:

[0038] Each ply is divided into multiple parallel scanning strips 1 according to a preset translation direction and a preset scanning strip 1 interval. The translation direction of the laser spot on each scanning strip 1 on the same ply is the same, and the translation speed is greater than or equal to 1500mm / s.

[0039] On the same scanning strip 1, the laser spot rotates along the center line of the scanning strip 1 at the current scanning position to form a ring scanning area with a radius R. The radius R is 1 to 1.5 times the radius of the laser spot. After completing the self-rotation scanning of the current ring scanning area, it is translated to the next ring scanning area, and the edges of the two adjacent ring scanning areas are tangent.

[0040] In this embodiment, the layup is performed according to a preset translation direction and a preset scanning strip 1 interval ( Figure 1 In step d), the process is divided into multiple parallel scanning strips 1. Strip scanning is performed using a laser rotation + translational motion coupling method, significantly enhancing molten pool disturbance. This results in periodic shearing and fracture of dendrite tips, interrupting the epitaxial growth of columnar crystals, achieving equiaxed grains, and reducing anisotropy. Furthermore, the laser scanning employs a high-speed scanning strategy with a translational speed greater than or equal to 1500 mm / s. This high scanning speed is controlled to create a shallow molten pool. The surface tension within the shallow molten pool enhances internal convection, refines dendrites, and further reduces the formation of columnar crystals in the high-temperature alloy. This significantly eliminates anisotropy in mechanical properties and improves transverse strength and creep resistance at high temperatures. Simultaneously, equiaxed crystals effectively hinder crack propagation along the columnar grain boundaries, significantly enhancing fatigue life and damage tolerance, and comprehensively improving the reliability of the component during service.

[0041] In this embodiment, the dwell time of each annular scanning area on the same scanning strip 1 is based on... Analysis yielded, among which The dwell time for each annular scan region, The preset number of rotations for a single annular scan area. The preset translation speed is set for scanning strip 1. By considering the preset number of rotations of a single annular scanning area and the preset translation speed of scanning strip 1, and by calculating the reasonable dwell time of each annular scanning area, it is possible to effectively interrupt columnar crystal growth and further limit the formation of columnar crystals in the high-temperature alloy.

[0042] In the specific implementation process, the scanning strips 1 of adjacent layers are rotated by 67°; on the same scanning strip 1, the angle of the start and stop position of the next annular scanning area is 67° different from the angle of the start and stop position of the previous annular scanning area.

[0043] In some embodiments, the metal powder is prepared by atomizing a mixture containing C, Si, Cr, Co, Mo, Al, Ti, W, Ta, P, B, and Ni elements to obtain Ni-based high-temperature alloy powder with a hollow powder content of less than 3%; wherein:

[0044] The main role of Cr is to improve the high-temperature corrosion resistance of Ni-based superalloys. Therefore, the Cr content should be as high as possible to stimulate the high-entropy effect. However, the Cr content should also be controlled to reduce the precipitation of harmful phases. Therefore, the Cr content is generally 15-20 wt.%.

[0045] Co can reduce the stacking fault energy of the matrix, promote the precipitation of the γ' phase in the alloy, stabilize the alloy and expand the heat treatment window; moreover, Co is beneficial to the stability of the microstructure, and it is easily dissolved in the matrix, which can produce hysteresis diffusion effect and lattice distortion effect; therefore, the Co content is selected to be 20-25 wt.%.

[0046] In this embodiment, the Ni-based superalloy matrix is ​​mainly composed of Ni-Co-Cr, with Ni mass fraction of 40-45 wt.%, Co mass fraction of 21-25 wt.%, and Cr mass fraction of 15-20 wt.%. By introducing high content of Co and Cr elements, high entropy effect, hysteresis diffusion effect, lattice distortion effect and "cocktail" effect are generated in the Ni matrix, thereby improving the solid solution strengthening effect.

[0047] Mo is a solid solution strengthening element that can increase the mismatch of γ / γ′, making the mismatched dislocation network denser and effectively hindering dislocation movement, thus improving performance. However, Mo has a very bad effect on the hot corrosion resistance of the alloy, so the Mo content is 0.5-1.5 wt.%.

[0048] The advantages of Ta are: it mainly improves the high-temperature strength of alloys by increasing the amount of γ' phase and enhancing its strength and thermal stability, while also having a solid solution strengthening effect. Ta has a large atomic radius and a low diffusion rate, which can affect the diffusion behavior of other elements within the alloy, inhibiting the formation of low-melting-point eutectic between dendrites to some extent and reducing the alloy's crack susceptibility. Furthermore, Ta also has beneficial effects on the alloy's oxidation resistance, hot corrosion resistance, and durability, and does not induce the formation of the TCP phase; therefore, 1-1.5 wt.% Ta can be added to the alloy.

[0049] W is a strong solid solution strengthening element that can improve interatomic bonding and diffusion activation energy, fully leveraging the strengthening effects of W and Ta to effectively enhance high-temperature performance. However, excessive W addition can lead to microstructure instability and the formation of brittle TCP phases such as μ and P phases. Therefore, the W content in the alloy is typically 3-6 wt.%.

[0050] In existing technologies, refractory elements such as Mo, W, and Ta are typically added to ensure high-temperature strength. The Mo+W+Ta content generally exceeds 10 wt.%, and the high content of these elements reduces the diffusion rate at high temperatures. This makes it difficult to improve the anisotropy of the additive manufacturing alloy's microstructure during solution heat treatment, resulting in significant differences in the properties of the additive manufacturing high-temperature alloy along and perpendicular to the deposition direction, making it difficult to meet application requirements. For the Ni-based high-temperature alloy in this embodiment, the high-entropy effect is utilized to enhance solid solution strengthening. The total Ta+W+Mo content is designed to be <8 wt.%, with Ta ≤1.5%, W ≤6%, and Mo ≤1.5%, and W / Ta or W / Mo >3, providing a certain solid solution strengthening effect while facilitating the uniformity of the microstructure during solution heat treatment.

[0051] Al is a fundamental element in nickel-based superalloys, forming the strengthening γ' phase (Ni3Al). Its content plays a crucial role in high-temperature performance, and it is also essential for the alloy's oxidation resistance. Therefore, a certain amount of Al must be added to superalloys. However, excessive Al can reduce the microstructure stability of the superalloy, leading to the precipitation of harmful phases (such as promoting carbide formation) and promoting the formation of low-melting-point eutectic phases between dendrites, thus increasing the alloy's crack susceptibility. Therefore, the Al content in the alloy should be controlled between 2.5-3.5 wt.%.

[0052] Ti is also a fundamental element for the formation of the γ' phase. When Ti is added to the alloy, the γ' phase changes from Ni3Al to Ni3(Al,Ti). Ti also has a beneficial effect on the alloy's resistance to hot corrosion. However, excessive Ti easily forms a large amount of carbides, leading to poor alloy microstructure stability. Therefore, the Ti content in this alloy is controlled at 4.5-5.5 wt.%.

[0053] In existing technologies, to ensure additive manufacturing processability, the Al+Ti content is generally controlled to be <6 wt.%, resulting in the γ' phase volume fraction in the alloy typically being below 40%, limiting the strengthening effect at high temperatures. For the Ni-based superalloy of this embodiment, the Al+Ti content is ≥7 wt.%, and the addition of a certain amount of Ta, through the high entropy effect, slows down the precipitation rate of the γ' phase, reduces solid-state phase transformation cracks, and achieves low additive manufacturing crack sensitivity even with high Al+Ti content. Furthermore, as the Ti / Al ratio increases, the antiphase domain boundary energy of the γ' phase increases, thereby improving mechanical properties. A high Ti / Al ratio is beneficial for increasing the antiphase domain boundary energy of the γ' phase, but an excessively high Ti / Al ratio will increase the mismatch of the γ' / γ phases, making the γ' phase unstable. Moreover, an excessively high Ti content also leads to an increase in carbide content, impairing the mechanical properties of the alloy. An excessively low Ti content also easily generates harmful phases. Therefore, a Ti / Al ratio of 1 to 1.8 is the optimal choice.

[0054] Trace elements such as C, B, and P are mainly grain boundary strengthening elements. They can form discontinuous fine carbides at grain boundaries, thereby improving grain boundary strength. However, if the content is too high, hard and brittle continuous chain-like carbides will be formed, becoming crack initiation and propagation areas, which is detrimental to the alloy properties. Therefore, the amount of B added to the alloy ranges from 0.01 to 0.03 wt.%, the amount of P ranges from 0.01 to 0.02 wt.%, and the amount of C ranges from 0.05 to 0.1 wt.%.

[0055] In this embodiment, in addition to improving the solid solution strength of the matrix to increase crack resistance, a small amount of B, P, and C are added. These elements segregate at the grain boundaries, further enhancing the grain boundary strength and ensuring high-temperature performance.

[0056] Example 2

[0057] See Figures 1 to 6 A method for preparing a hot-crack-free precipitation-strengthened superalloy using additive manufacturing is disclosed. This embodiment uses Ni-based superalloy powder as raw material for additive manufacturing of the target part. The elements in the Ni-based superalloy powder include C, Si, Cr, Co, Mo, Al, Ti, W, Ta, P, B, and Ni. The preparation process mainly includes the following steps:

[0058] Step 1: Selection of Raw Materials

[0059] 1.1 Establishing an analytical model for the average electron vacancy number of Ni-based superalloy powders based on elemental molar amounts and electron vacancies ,in The average number of electron vacancies in Ni-based superalloy powder. For the first The number of electron vacancies in each element. For the first The molar content of each element;

[0060] 1.2 Using the preset upper limit of the average number of electron vacancies in Ni-based superalloy powder as a constraint, the analysis model is used to perform optimization analysis on the mass percentage of each element in Ni-based superalloy powder to obtain the optimized mass percentage value of the corresponding element in Ni-based superalloy powder.

[0061] In this embodiment, the upper limit of the average number of electron vacancies in the Ni-based superalloy powder is set to 1.6. Under the constraints of the Ni:Co:Cr ratio (40-45):(21-25):(15-20), Al+Ti content ≥7wt.%, Ti / Al = 1-1.8, Ta+W+Mo total content <8wt.%, Ta ≤1.5wt.%, W ≤6wt.%, Mo ≤1.5wt.%, W / Ta >3 or W / Mo >3, and B content range of 0.01-0.03wt.%, P content range of 0.01-0.02wt.%, and C content range of 0.05-0.1wt.%, the main components of the Ni-based superalloy powder are obtained through optimization as follows: C content 0.06wt.%, Si content ≤0.06wt.%, Cr content 18.5wt.%, Co content 23.5wt.%, and Mo content 1wt. Al content is 2.5 wt.%, Ti content is 4.5 wt.%, W content is 4.3 wt.%, Ta content is 1.2 wt.%, P content is 0.012 wt.%, B content is 0.011 wt.%, and the balance is Ni.

[0062] The analysis model was used to verify that the average number of electron vacancies in the alloy was 1.52, which meets the design requirements.

[0063] Step 2: Powder Preparation

[0064] In this embodiment, Ni-based superalloy powder is prepared using methods such as argon atomization or rotary motor atomization. The powder sphericity reaches 90%, and the content of hollow powder is less than 3%. The powder particle size range can be 0-45μm, 0-53μm, or 15-45μm and 15-53μm. In this embodiment, 15-53μm powder is used, and the content of powder in the 0-15μm range does not exceed 25%.

[0065] Step 3: Component Forming

[0066] 3.1 A three-dimensional solid geometric model of the target part is established using computer-aided design software. Then, the three-dimensional solid geometric model is sliced ​​into layers with a slice thickness and a powder layer thickness of 20 μm. The width of the scanning strip 1 is set to 2 mm. The scanning strip 1 determines the laser translation direction and moves in a Zigzag manner. The adjacent scanning strips 1 are rotated 67°.

[0067] 3.2 Adjust the laser spot diameter using an electric beam expander, setting the laser spot diameter to 100 μm;

[0068] 3.3 Setting the laser scanning path and laser process parameters. A coupled laser rotation and translation motion is used. The scanning trajectory rotates with a radius of 50 μm, the laser power is 180 W, and the laser scanning speed is 1700 mm / s, completing the scanning of the first annular scanning area. The second annular scanning area begins scanning along the laser translation direction determined by scanning strip 1, with the edge of the second annular scanning area tangent to the edge of the first annular scanning area; the angle of the start and stop positions of the second annular scanning area differs from that of the first annular scanning area by 67°; this process continues until the translational scanning of the first scanning strip 1 is completed, with the scanning trajectory as shown below. Figure 1 As shown, e represents the translation direction and path, and f represents the laser's self-rotation direction;

[0069] 3.4 Then, perform the second scan strip 1, with a spacing of 180 μm between the second scan strip 1 and the first scan strip 1, and continue scanning in a manner similar to that in 3.3 until the layup scan is completed;

[0070] 3.5 After completing the scanning of all scanning strips 1 of the current layup, perform powder laying and scanning of the next layup above the current layup, repeating until the target part is formed.

[0071] 3.6 The alloy block specimen was ground and polished according to the standard metallographic specimen preparation method. The metallographic structure image is as follows. Figure 2 , Figure 3 As shown, the formed sample has no obvious cracks, only a few micropores, exhibiting high laser formability and a forming density of 99.8%; Figure 4 As shown, columnar crystals are not prominent (grain aspect ratio is 3.5).

[0072] IV. Heat Treatment

[0073] Due to the non-equilibrium solidification of selective laser melting (SLM), the rapid cooling rate and incomplete element diffusion lead to severe elemental segregation and the presence of segregated phases. Solution heat treatment is the most common and effective method to improve segregation and reduce harmful segregated phases in single-crystal superalloys. In this embodiment, the sample was cooled to 1100℃ at a rate of 6℃ / min for 4 hours, held at that temperature for 4 hours, air-cooled, and then held at 870℃ for 16 hours. The resulting target part sample exhibited curved grain boundaries, such as... Figure 5 As shown, the volume fraction of the precipitated strengthening phase γ′ reaches approximately 50%, as... Figure 6 As shown.

[0074] V. Performance Testing

[0075] The mechanical properties of the target part samples obtained in this embodiment were tested, and the relevant test results are shown in Table 1:

[0076] Table 1. Statistical table of transverse and longitudinal mechanical properties of the target part sample in Example 2

[0077]

[0078] As shown in the table above, the transverse and longitudinal mechanical properties are similar, the anisotropy difference is small, and the high temperature strength is relatively high.

[0079] Example 3

[0080] This embodiment uses Ni-based superalloy powder as raw material for additive manufacturing of the target part. The elements in the Ni-based superalloy powder include C, Si, Cr, Co, Mo, Al, Ti, W, Ta, P, B, and Ni. The preparation process mainly includes the following steps:

[0081] Step 1: Selection of Raw Materials

[0082] 1.1 Establishing an analytical model for the average electron vacancy number of Ni-based superalloy powders based on elemental molar amounts and electron vacancies ,in The average number of electron vacancies in Ni-based superalloy powder. For the first The number of electron vacancies in each element. For the first The molar content of each element;

[0083] 1.2 Using the preset upper limit of the average number of electron vacancies in Ni-based superalloy powder as a constraint, the analysis model is used to perform optimization analysis on the mass percentage of each element in Ni-based superalloy powder to obtain the optimized mass percentage value of the corresponding element in Ni-based superalloy powder.

[0084] In this embodiment, the upper limit of the average number of electron vacancies in the Ni-based superalloy powder is set to 1.7. Under the constraints of the Ni:Co:Cr ratio (40-45):(21-25):(15-20), Al+Ti content ≥7wt.%, Ti / Al = 1-1.8, Ta+W+Mo total content <8wt.%, Ta ≤1.5wt.%, W ≤6wt.%, Mo ≤1.5wt.%, W / Ta >3 or W / Mo >3, and B content range of 0.01-0.03wt.%, P content range of 0.01-0.02wt.%, and C content range of 0.05-0.1wt.%, the main components of the Ni-based superalloy powder are obtained through optimization as follows: C content 0.08wt.%, Si content 0.01wt.%, Cr content 19.5wt.%, Co content 23.5wt.%, Mo content 1.2wt.%, and Al content 3wt.%. The composition is as follows: Ti content is 5 wt.%, W content is 4.5 wt.%, Ta content is 1.4 wt.%, P content is 0.015 wt.%, B content is 0.014 wt.%, and the balance is Ni.

[0085] The analysis model was used for verification, and the average number of electron vacancies in the alloy was calculated to be 1.63, which meets the design requirements.

[0086] Step 2: Powder Preparation

[0087] In this embodiment, 0-53μm Ni-based high-temperature alloy powder is prepared by argon atomization or rotary motor atomization, wherein the content of powder in the 0-15μm range does not exceed 25%.

[0088] Step 3: Component Forming

[0089] 3.1 A three-dimensional solid geometric model of the target part is established using computer-aided design software. Then, the three-dimensional solid geometric model is sliced ​​into layers with a slice thickness and a powder layer thickness of 30 μm. The width of the scanning strip 1 is set to 2 mm. The scanning strip 1 determines the laser translation direction and moves in a Zigzag manner. The adjacent scanning strips 1 are rotated 67°.

[0090] 3.2 Adjust the laser spot diameter using an electric beam expander, setting the laser spot diameter to 100 μm;

[0091] 3.3 Setting the laser scanning path and laser process parameters. A coupled laser rotation and translation motion is used. The scanning trajectory rotates with a radius of 60μm, the laser power is 190W, and the laser scanning speed is 1800mm / s, completing the scanning of the first annular scanning area. The second annular scanning area begins scanning along the laser translation direction determined by scanning strip 1, with the edge of the second annular scanning area tangent to the edge of the first annular scanning area; the angle of the start and stop positions of the second annular scanning area differs from that of the first annular scanning area by 67°; this process continues until the translational scanning of the first scanning strip 1 is completed, with the scanning trajectory as shown below. Figure 1 As shown;

[0092] 3.4 Then, the second scan strip 1 is scanned, with a 100 μm interval between the second scan strip 1 and the first scan strip 1, following a similar scanning method as in 3.3 of this embodiment, until the layup scan is completed;

[0093] 3.5 After completing the scanning of all scanning strips 1 of the current layup, perform powder laying and scanning of the next layup above the current layup, repeating until the target part is formed.

[0094] 3.6 The alloy block sample was ground and polished according to the standard metallographic sample preparation method. The formed sample had no obvious cracks, only a small number of micropores, and had high laser formability, with a forming density of 99.8%.

[0095] IV. Heat Treatment

[0096] In this embodiment, the temperature was 1180℃ for 4 hours, cooled to 1100℃ at a cooling rate of 6℃ / min, held for 4 hours, air-cooled, and then held at 870℃ for 16 hours.

[0097] V. Performance Testing

[0098] The mechanical properties of the target part samples obtained in this embodiment were tested, and the relevant test results are shown in Table 2:

[0099] Table 2. Statistical table of transverse and longitudinal mechanical properties of the target part sample in Example 3

[0100]

[0101] As shown in the table above, the transverse and longitudinal mechanical properties are similar, the anisotropy difference is small, and the high strength is relatively high.

[0102] Comparative Example

[0103] Step 1: Selection of Raw Materials

[0104] This embodiment uses MarM247 alloy as a comparative example. Its main components are: C 0.08 wt.%, Si 0.02 wt.%, Cr 8.5 wt.%, Co 9.5 wt.%, Mo 0.5 wt.%, Zr 0.01 wt.%, Al 5.5 wt.%, Fe 0.1 wt.%, W 10.2 wt.%, Ta 3.0 wt.%, Hf 1.5 wt.%, Ti 0.8 wt.%, with the balance being Ni. In this alloy, the Al+Ti content is 6.3 wt.%, and the Mo+W+Ta content is 13.7 wt.%. The average number of electron vacancies in this alloy can be calculated to be 1.19, indicating high structural stability and low precipitation of harmful phases.

[0105] Step 2: Powder Preparation

[0106] In this embodiment, 15-53μm MarM247 alloy powder is prepared by argon atomization or rotary motor atomization, wherein the content of powder in the 0-15μm range does not exceed 25%.

[0107] Step 3: Component Forming

[0108] 3.1 A three-dimensional solid geometric model of the target part was established using computer-aided design software. This model was then sliced ​​into layers, and the laser scanning path and laser process parameters were set. The laser power was 150W, the laser scanning speed was 1000mm / s, the scanning interval (scanning strip 1 interval d) was 80μm, the powder layer thickness was 20μm, and the volume energy input was 93.75J / mm². 3 A partitioned scanning strategy is adopted, with a partition size of 10mm and a rotation of 67° between adjacent layers;

[0109] 3.2 The alloy block specimen was ground and polished according to the standard metallographic specimen preparation method, such as... Figure 7 and Figure 8 The formed sample contained obvious cracks and a small number of micropores, with a forming density of 99.2%. Columnar crystals were prominent, and the grain aspect ratio reached 5.3. Figure 9 As shown.

[0110] IV. Heat Treatment

[0111] In this case, the solution was treated at 1240℃ for 4 hours, then cooled to 1080℃ at an air cooling rate, held for 4 hours, air cooled again, and subsequently held at 870℃ for 16 hours. Despite using higher solution temperatures, the microstructure exhibited anisotropy, such as... Figure 10 As shown, Figure 10 In the middle, (a) is perpendicular to the deposition direction, and (b) is along the deposition direction.

[0112] V. Performance Testing

[0113] The mechanical properties of the target part samples obtained in this embodiment were tested, and the relevant test results are shown in Table 3:

[0114] Table 3. Statistical table of transverse and longitudinal mechanical properties of the target part samples in the comparison example.

[0115]

[0116] As can be seen from the table above, the target part samples in the comparison examples have large differences in mechanical properties in the longitudinal and transverse directions, significant anisotropy, and poor transverse properties.

[0117] Compared with the control example, in Examples 2 and 3, a higher Ti / Al ratio was used to control the volume fraction of the γ' phase (45-60%) to ensure high-temperature performance while strengthening the γ and γ′ phases and effectively suppressing the formation of γ / γ' low-melting-point eutectic. In addition, a higher content of solid solution strengthening elements such as Cr and Co was added to enhance the intrinsic strength of the matrix by utilizing the high entropy effect, and trace amounts of grain boundary elements C, B, and P were added to strengthen the grain boundaries. Furthermore, during the preparation of Ni-based superalloy powder, under the constraints of a given range of element content or ratio, the content of each component element in the Ni-based superalloy powder is optimized using an analytical model to ensure that the average number of electron vacancies in the Ni-based superalloy meets the limit requirements. This ensures high structural stability of the alloy and prevents the precipitation of harmful phases. At the same time, the composition is controlled to suppress the formation of liquefaction cracks, solidification cracks, and solid-state cracks as much as possible. Simultaneously, the precipitation strengthening, solid solution strengthening, and grain boundary strengthening effects of alloy elements are utilized to improve the high-temperature mechanical properties of the alloy and maintain high-temperature structural stability. This enables the alloy to reach the level of high-performance additive manufacturing superalloys and meet the service requirements at 900℃ and higher temperatures.

[0118] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hot-crack-free precipitation-strengthened superalloy using additive manufacturing, characterized in that, include: Based on the arrangement and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced ​​in the vertical direction; the laser scanning forming equipment is used to form a laser spot to melt the metal powder scanning area corresponding to each slice of the target part. Following a bottom-up, layered slicing structure, powder is sequentially laid layer by layer in the forming chamber. The laser spot diameter is adjusted to a preset diameter using an electric beam expander. A laser rotation and translational motion coupled scanning method is employed to scan and melt the metal powder at each layer's processing location, completing the laser scanning forming of the target part. The laser rotation and translational motion coupled scanning method includes: Each ply is divided into multiple parallel scanning strips according to a preset translation direction and a preset scanning strip interval. The laser spot has the same translation direction on each scanning strip of the same ply, and the translation speed is greater than or equal to 1500 mm / s. On the same scanning strip, the laser spot rotates at the point on the center line of the scanning strip at the current scanning position to form a ring scanning area with a radius R. The radius R is 1 to 1.5 times the radius of the laser spot. After completing the self-rotation scanning of the current ring scanning area, it moves to the next ring scanning area, and the edges of the two adjacent ring scanning areas are tangent.

2. The preparation method according to claim 1, characterized in that, The dwell time of each annular scan area on the same scan strip is based on Analysis yielded, among which The dwell time for each annular scan region, The preset number of rotations for a single annular scan area. The preset translation speed for the scanning strip.

3. The preparation method according to claim 1, characterized in that, The scanning strips of adjacent layers rotate 67°; on the same scanning strip, the angle of the start and stop position of the next annular scanning area differs from the angle of the start and stop position of the previous annular scanning area by 67°.

4. The preparation method according to claim 1, characterized in that, The metal powder is prepared by atomizing a mixture containing C, Si, Cr, Co, Mo, Al, Ti, W, Ta, P, B, and Ni elements to obtain Ni-based high-temperature alloy powder with a hollow powder content of less than 3%; wherein, by mass percentage, the ratio of Ni:Co:Cr is (40-45):(21-25):(15-20), and the Al+Ti content is ≥7wt.%, with Ti / Al = 1-1.

8.

5. The preparation method according to claim 4, characterized in that, Also includes: Establish an analytical model for the average electron vacancy number of Ni-based superalloy powders based on elemental molar amounts and electron vacancies. ,in The average number of electron vacancies in Ni-based superalloy powder. For the first The number of electron vacancies in each element. For the first The molar content of each element; Using the preset upper limit of the average number of electron vacancies in Ni-based superalloy powder as a constraint, the analysis model is used to perform optimization analysis on the mass percentage of each element in Ni-based superalloy powder, and the optimized value of the mass percentage of the corresponding element in Ni-based superalloy powder is obtained.

6. The preparation method according to claim 5, characterized in that, The constraints also include: the total content of Ta+W+Mo is <8 wt.%, of which Ta ≤1.5 wt.%, W ≤6 wt.%, Mo ≤1.5 wt.%, and W / Ta >3 or W / Mo >3.

7. The preparation method according to claim 5, characterized in that, The constraints also include: the amount of B is 0.01 to 0.03 wt.%, the amount of P is 0.01 to 0.02 wt.%, and the amount of C is 0.05 to 0.1 wt.% by mass percentage.

8. The preparation method according to claim 1, characterized in that, After completing the laser scanning forming of the target part, the laser-scanned target part is heated in the range of 1150-1200℃ at a rate of 10℃ / min, held at the temperature for 4 hours, and then slowly cooled in stages. The first stage involves cooling at a rate of ≤7℃ / min to 1050℃, holding at that temperature for 4 hours, followed by air cooling; then heating at a rate of 10℃ / min to 870℃ and holding at that temperature for 16 hours, followed by air cooling to obtain the final product.

9. An additively manufactured, crack-free, precipitation-strengthened high-temperature alloy, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

Images