High-temperature alloy for generating nano reinforced phase in situ by utilizing double-laser additive, preparation method and application of high-temperature alloy

Abstract

The invention relates to the field of high-temperature alloys, in particular to a high-temperature alloy preparation method for generating a nano reinforced phase in situ by using dual-laser additive, which comprises the following steps: preparing powder according to the performance requirement of a component; parameters of the dual-laser DED system are set; performing main laser deposition to form a molten pool deposition layer; auxiliary laser local heating is carried out, and a nanometer reinforced phase is generated in situ on a deposition layer of the molten pool; and the step S3 and the step S4 are repeated, and multi-layer deposition is formed till the component is completed. In addition, in-situ reaction of active elements or compounds is achieved in the additive manufacturing process to form nano-particles, matrix columnar crystals can be converted into isometric crystals, dispersion strengthening is achieved, and the high-temperature strength of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloys, and more specifically, to a high-temperature alloy using dual-laser additive manufacturing to generate nano-reinforcing phases in situ, its preparation method, and its application. Background Technology

[0002] High-temperature alloys have critical applications in aerospace, energy equipment, and other fields, such as turbine blades, gas turbines, high-temperature molds, and core components of nuclear power plants. In these applications, materials must simultaneously possess high-temperature strength, creep resistance, thermal stability, and fatigue resistance. Traditional methods for preparing high-temperature alloys include casting, powder metallurgy, and hot isostatic pressing, but these methods have the following shortcomings: 1. Limitations on microstructure uniformity and performance: Casting processes are prone to segregation, voids and coarse grain structures, which limit the high-temperature performance and lifespan of materials; Powder metallurgy can obtain a more uniform microstructure, but it is inefficient in manufacturing complex shaped components.

[0003] 2. Nano-strengthening is difficult to achieve: Premixing nanoparticles for powder preparation easily leads to particle agglomeration and poor dispersibility, affecting the strengthening effect. At the same time, the powder flowability and powder delivery uniformity are also affected.

[0004] Laser-directed energy deposition (DED) has attracted attention in aero-engines and energy equipment due to its high deposition rate and ability to fabricate complex, large-sized components. Compared to powder bed melting (PBF), DED has higher deposition efficiency and can build large-sized components, but its high melt pool temperature and slow cooling rate tend to form coarse-grained structures, limiting the effectiveness of traditional grain strengthening methods. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing. By realizing the in-situ reaction of active elements or compounds to form nanoparticles during the additive manufacturing process, the columnar crystals of the matrix can be transformed into equiaxed crystals, thereby achieving dispersion strengthening and improving the high-temperature strength of the material.

[0006] Another objective of this invention is to provide a high-temperature alloy that utilizes dual-laser additive manufacturing to generate nano-reinforcing phases in situ. By introducing the in-situ generated nano-reinforcing phases, the columnar crystals of the matrix can be transformed into equiaxed crystals, achieving dispersion strengthening and improving the high-temperature strength of the material.

[0007] The technical problem solved by this invention is achieved by the following technical solution.

[0008] On one hand, embodiments of the present invention provide a method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing, comprising the following steps: S1, Prepare powder according to the performance requirements of the component; S2, set the parameters of the dual-laser DED system according to the performance requirements of the components; S3, main laser deposition to form a molten pool deposition layer; S4, supplemented by localized laser heating, generates nano-reinforcing phases in situ in the molten pool deposition layer; S5. Repeat steps S3 and S4 to form multi-layer deposition until the component is complete.

[0009] In some embodiments of the present invention, in step S3, the laser power is 200–800 W, the scanning speed is 2–5 mm / s, the powder feed rate is 5–15 g / min, and the protective atmosphere is Ar with an oxygen content of <50 ppm.

[0010] In some embodiments of the present invention, in step S4, the laser power is 50–300 W, the pulse width is 290 fs–900 ps, ​​and the scanning speed is 2–5 mm / s.

[0011] In some embodiments of the present invention, step S4 further includes adjusting the scanning trajectory of the auxiliary laser to achieve a uniform distribution of the nano-reinforcement phase.

[0012] In some embodiments of the present invention, the particle size of the powder is 40-120 μm.

[0013] Secondly, embodiments of the present invention provide an application of in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing, which is used to prepare Ni-based, Co-based, Fe-based, and high-entropy alloy systems based on the above method.

[0014] In some embodiments of the present invention, when preparing the nickel-based alloy, the powder comprises the following raw materials by mass percentage: Mo: 8-10%, Cr: 20-25%, Fe: 15-20%, Co: 2-5%, W: 0.5-1%, C: 0-0.1%, Si: 0-0.1%, Ni: balance.

[0015] In preparing the high-entropy alloy, the powder comprises the following raw materials by mass percentage: Co: 22–24%, Cr: 18–20%, Fe: 18–20%, Mn: 18–20%, Ni: 18–20%, Al: 0.8–1.2%, Ti: 0.5–0.8%, C: 0–0.05%, O: ≤0.03%, balance being unavoidable impurities.

[0016] Thirdly, the present invention provides a high-temperature alloy prepared by the above-mentioned high-temperature alloy preparation method using dual-laser additive in-situ generation of nano-reinforcing phases.

[0017] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: The preparation method provided by this invention utilizes the synergistic effect of two lasers. The main laser is used for deposition and shaping to ensure the continuous and stable molten pool, while the auxiliary laser is used for thermal excitation and chemical reaction triggering. By adjusting the laser power, scanning path, and delay, the formation region and concentration of the nano-reinforcing phase can be precisely controlled. The prepared high-temperature alloy exhibits significant improvement in mechanical properties under high-temperature tensile conditions. Especially during long-term high-temperature service, the nanoparticles effectively suppress dislocation movement and grain boundary slip, extending the material life.

[0018] By precisely controlling the temperature gradient at the molten pool front using pulsed lasers, active elements or compounds undergo chemical reactions or precipitation during rapid cooling, forming oxide nanoparticles with sizes ranging from 20 to 130 nm. Subsequently, the molten pool turbulence induced by the shock wave generates strong shearing action, effectively suppressing particle coarsening. Due to the extremely high cooling rate, these nanoparticles are uniformly distributed within the grain boundaries and grain interiors, thus achieving a significant dispersion strengthening effect.

[0019] By employing auxiliary laser local scanning, power regulation, and scanning strategy design, the distribution of nanoparticles can be optimized while maintaining the deposition efficiency of large-scale components, thus achieving a balance between macroscopic uniformity and microscopic enhancement of the components.

[0020] The method provided by this invention is applicable to Ni-based, Co-based, Fe-based and high-entropy alloy systems. By adjusting the powder composition and laser parameters, it can be adapted to different service environments and component requirements. At the same time, it can be combined with subsequent heat treatment to further optimize the microstructure and properties.

[0021] This enables the high-temperature alloys prepared by DED to not only possess the ability to manufacture complex components and high deposition efficiency, but also to improve the mechanical properties of the matrix through in-situ nano-strengthening, providing a feasible technical path for the preparation of high-temperature structural materials for aero-engines, gas turbines and nuclear energy equipment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of the high-temperature alloy preparation method using dual-laser additive manufacturing to generate nano-reinforcing phases in situ according to the present invention; Figure 2 This is a comparison diagram of grain size between dual-laser additive manufacturing and single-laser additive manufacturing in Embodiment 1 of the present invention; Figure 3 This is a statistical diagram showing the morphology and size distribution of nanoparticles produced by dual-laser additive manufacturing in Example 1 of the present invention. Figure 4 This is a comparison image of the grain morphology (EBSD) of dual-laser additive manufacturing in Example 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0026] This invention provides a method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing, comprising the following steps: S1. Prepare powder according to the performance requirements of the component; the particle size of the powder is 40-120μm. S2, set the parameters of the dual-laser DED system according to the performance requirements of the components; S3, main laser deposition to form a molten pool deposition layer; S4, supplemented by localized laser heating, generates nano-reinforcing phases in situ in the molten pool deposition layer; S5. Repeat steps S3 and S4 to form multi-layer deposition until the component is complete.

[0027] In step S3, the laser power is 200–800 W, the scanning speed is 2–5 mm / s, the powder feed rate is 5–15 g / min, and the protective atmosphere is Ar with an oxygen content of <50 ppm. In step S4, the laser power is 50–300 W, the pulse width is 290 fs–900 ps, ​​and the scanning speed is 2–5 mm / s.

[0028] Step S4 also includes adjusting the scanning trajectory of the auxiliary laser to achieve a uniform distribution of the nano-reinforced phase.

[0029] Based on the above method, it can be used to prepare Ni-based, Co-based, Fe-based and high-entropy alloy systems.

[0030] Dual laser synergy: The main laser is used for deposition and shaping to ensure the continuous and stable molten pool, while the auxiliary laser is used for thermal excitation and chemical reaction triggering. By adjusting the laser power, scanning path and delay, precise control over the formation area and concentration of the nano-reinforced phase can be achieved.

[0031] In-situ nano-oxide enhanced phase formation mechanism: A pulsed laser precisely controls the temperature gradient at the molten pool front, inducing chemical reactions or precipitation of active elements or compounds during rapid cooling, forming oxide nanoparticles with sizes ranging from 20 to 130 nm. Subsequently, the shock wave-induced molten pool turbulence generates strong shearing action, effectively suppressing particle coarsening. Due to the extremely high cooling rate, these nanoparticles are uniformly distributed within the grain boundaries and grain interiors, thus achieving a significant dispersion strengthening effect.

[0032] Example 1 As attached Figure 1 As shown, the high-temperature alloy of this embodiment was prepared according to the following steps. 1. Raw materials: High-temperature alloy nickel-based powder is selected, with the following composition: Mo: 8-10%, Cr: 20-25%, Fe: 15-20%, Co: 2-5%, W: 0.5-1%, C: 0-0.1%, Si: 0-0.1%, Ni-balance, and the powder particle size range is 100-120 μm.

[0033] 2. Dual-laser DED system configuration The master laser (L1) is used to achieve molten pool deposition and shaping; L2 lasers are used to activate specific reactions, such as elemental segregation, redox reactions, or interfacial energy modulation. Dual lasers can be arranged coaxially or off-axis, with an adjustable delay time Δt ranging from 0 to 1 s. The L1 laser parameters are: laser power 200–800 W, scanning speed: 2–5 mm / s; L2 laser parameters are: laser power 50–300 W, pulse width: 290 fs-900 ps, ​​scanning speed: 2-5 mm / s; 3. In-situ reaction and nanophase formation mechanism Under the influence of L1, a molten pool deposition layer is formed; L2 local control of the molten pool temperature gradient specifically utilizes a high-frequency pulsed laser as an energy input source to instantaneously irradiate the molten pool surface, inducing the formation of local hot spots with temperatures much higher than the substrate temperature, increasing the chemical activity of elements, and causing short-range diffusion of active elements. By controlling the solidification process and dynamically regulating the temperature gradient and supercooling of the solid / liquid interface through instantaneous thermal perturbation using high-frequency pulsed laser, the continuous growth of columnar dendrites is suppressed, allowing nano-reinforcing phases (such as CrO2) to precipitate in situ in the frontal region of the molten pool. This achieves a controllable transformation of the solidification structure from columnar crystals to ultrafine equiaxed crystals, resulting in significant dispersion strengthening of nanoparticles.

[0034] By adjusting the scanning trajectory of L2, the uniform distribution of the nanophase can be achieved by adjusting the distance between the auxiliary laser and the main laser, that is, the positional relationship between the auxiliary laser and the molten pool (front, middle, and tail of the molten pool).

[0035] The front part of the molten pool (the leading edge) is located in the rapid advancement zone of the solid-liquid interface, where the temperature gradient and supercooling are the largest. The impact mainly induces interfacial instability and evaporation-recondensation nucleation. The resulting nanoparticles are the smallest in size (usually tens of nanometers) and relatively limited in number, but have the strongest nucleation ability. They are easily captured directly by the solidification front and contribute the most to grain refinement. They can be used for load-bearing components with extremely high requirements for strength, fatigue and crack resistance, such as aero-engine blades, gas turbine blades, load-bearing frames, and key structural components of high-temperature alloys or high-entropy alloys.

[0036] The central part of the molten pool has the highest temperature, the deepest molten pool, and the most intense flow. The impact mainly leads to the breakup of the molten jet and the atomization of droplets, resulting in the largest number of nanoparticles with medium size (tens to hundreds of nanometers). However, under strong convection, the nanoparticles are relatively unstable, and some may agglomerate or re-dissolve. Their main function is to homogenize the composition and break up dendrites. They are suitable for large-volume or complex components with high requirements for microstructure and composition homogeneity, such as molds, additive manufacturing load-bearing shells, pressure vessel repair areas, and functionally graded material components.

[0037] The tail end of the molten pool is in a rapid solidification and cooling phase, where the number of newly formed particles from impact is limited. The primary effect is the recapture, growth, and maturation of particles generated in the front and middle sections, resulting in the largest, most widely distributed, and easily agglomerated particles. Its role is more about regulating the final microstructure and stress state than directly refining the grains. This method is more suitable for components with high requirements for residual stress, dimensional stability, and surface quality, such as precision repair parts, thin-walled structures, mold cavity surfaces, and wear-resistant coatings.

[0038] 4. Optimization of process parameters Main laser power: 200-800 W; Main laser scanning speed: 3 mm / s; Powder feed rate: 10 g / min; Protective atmosphere: Ar, oxygen content <50 ppm; Auxiliary laser power: 50-300 W; Auxiliary laser pulse width: 290 fs; Auxiliary laser scanning speed: 3 mm / s; Auxiliary laser delay time: 0-1 s; The laser power combination and time delay parameters were optimized through orthogonal experiments to control the nanophase size between 20 and 120 nm.

[0039] Orthogonal experimental parameter design: the main laser power is selected as 200W, 400W, and 600W, the auxiliary laser power is selected as 50W, 150W, and 300W, and the auxiliary laser delay time is 0s, 0.5s, and 1s.

[0040] The optimized parameters are: main laser power 400 W, main laser scanning speed 4 mm / s, main laser powder feed rate 10 g / min, protective atmosphere: Ar; auxiliary laser pulse width 290 fs, auxiliary laser power 50 W, auxiliary laser scanning speed 4 mm / s, auxiliary laser delay time 0.5 s. The orthogonal test results are shown in Table 1.

[0041] Table 1

[0042] 5. Performance Testing and Verification Dual-laser additive manufacturing: an alloy prepared using the above-mentioned raw materials and optimal parameters; Single-laser additive manufacturing: Unlike dual-laser additive manufacturing, only the main laser is used, and the auxiliary laser is not used.

[0043] Using the aforementioned dual-laser additive manufacturing and single-laser additive manufacturing as test objects, their grain distribution was tested, and the results are as follows: Figure 2 As shown. From Figure 2 It can be concluded that the grain size of dual-laser additive manufacturing is concentrated at 20-30µm and has a high degree of concentration, while the grain size distribution of single-laser additive manufacturing is wider.

[0044] Its microstructure was observed using TEM, and the results are as follows: Figure 3 and 4 As shown. From Figure 3 and 4 It can be concluded that the microstructure of dual-laser additive manufacturing exhibits a composite structure reinforced by fine grains and dispersed nanoparticles, indicating that the dual-laser additive manufacturing process generates nanophases in situ and distributes them uniformly.

[0045] As shown in Tables 2 and 3, the dual-laser additive alloy exhibits 10–30% higher tensile strength at 600℃ compared to the single-laser additive alloy sample without nano-reinforcing phase; and 20–40% higher creep life at 600℃ and 100MPa compared to the single-laser additive alloy without nano-reinforcing phase.

[0046] Table 2

[0047] Table 3

[0048] Example 2 The CoCrFeMnNi high-entropy alloy of this embodiment was prepared according to the following steps: 1. Raw materials The selected high-entropy alloy powder is composed of Co: 22–24%, Cr: 18–20%, Fe: 18–20%, Mn: 18–20%, Ni: 18–20%, Al: 0.8–1.2%, Ti: 0.5–0.8%, C: 0–0.05%, O: ≤0.03%, with the balance being unavoidable impurities; the powder particle size distribution D50 = 95–115 μm, and the sphericity ≥0.92.

[0049] 2. Dual-laser DED system configuration Main laser L1: Continuous fiber laser, power 400–1000 W, scanning speed 3–5 mm / s, used for molten pool deposition forming; Auxiliary laser L2: pulsed green laser, wavelength 515 nm, power 30–200 W, pulse width 290 fs–900 ps; scanning speed 3–5 mm / s, spot diameter 3 mm; L1 and L2 are arranged as a bypass axis. The focus of L2 can be programmed to be adjusted between 0–2 mm at the leading edge of the L1 molten pool, the middle of the molten pool, or the tail of the molten pool. The delay time Δt = 0–0.5 s is adjustable.

[0050] 3. In-situ reaction and nanophase formation mechanism Within the steady-state molten pool formed by L1, Al and Ti elements are enriched between dendrites. L2 irradiates the tail of the molten pool with high-frequency pulses, causing an instantaneous temperature rise of ΔT = 80–150 K, triggering the solid-state ordered transformation of [Al,Ti] + γ-FCC → γ′-L12 (Co,Cr,Fe,Mn,Ni)3(Al,Ti). The pulsed thermal perturbation simultaneously reduces the temperature gradient G by 30–50% and increases the solidification rate R by 20–40%, inhibiting the epitaxial growth of columnar crystals and promoting the in-situ dispersed precipitation of the γ′ phase on the γ matrix, with an average particle size of 20–80 nm and a volume fraction of 5–12%. By changing the scanning trajectory and Δt of L2, the nano-γ′ phase can be uniformly distributed within the deposition layer or gradient concentrated on the surface.

[0051] 4. Optimization of process parameters Orthogonal experimental parameter design: main laser power 400, 600, 800W, scanning speed 4 mm / s, powder feeding rate: 15 g / min; powder feeding amount 5, 10, 15 g / min; auxiliary laser power 30, 150, 200 W, auxiliary laser pulse width selected 290fs, scanning speed 4mm / s, delay time 0, 0.3, 0.5s; The optimal coupling parameters were determined by orthogonal experiments: main laser power 600 W, main laser scanning speed 4 mm / s, main laser powder feed rate 15 g / min, protective atmosphere: Ar; auxiliary laser pulse width 290 fs, auxiliary laser power 150 W, auxiliary laser scanning speed 4 mm / s, auxiliary laser delay time 0.3 s. Under these conditions, the average size of γ′ was 46.02 nm, the volume fraction was 9.2%, and the deposition density was 99.6%. The results of the orthogonal experiments are shown in Table 4.

[0052] Table 4

[0053] In summary, the high-temperature alloy preparation method provided by this invention, which utilizes dual-laser additive manufacturing to generate nano-reinforcing phases in situ, can form oxides and nano-reinforcing phases with controllable size and uniform distribution in the matrix, and promote the transformation of columnar crystals in the matrix to equiaxed crystals, thereby significantly improving high-temperature tensile strength. This provides an efficient and controllable preparation technology path for high-temperature structural materials such as aero-engines, gas turbines, and nuclear energy equipment.

[0054] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing, characterized in that, Includes the following steps: S1, Prepare powder according to the performance requirements of the component; S2, set the parameters of the dual-laser DED system according to the performance requirements of the components; S3, main laser deposition to form a molten pool deposition layer; S4, supplemented by localized laser heating, generates nano-reinforcing phases in situ in the molten pool deposition layer; S5. Repeat steps S3 and S4 to form multi-layer deposition until the component is complete.

2. The method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 1, characterized in that, In step S3, the laser power is 200–800 W, the scanning speed is 2–5 mm / s, the powder feed rate is 5–15 g / min, and the protective atmosphere is Ar with an oxygen content of < 50 ppm.

3. The method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 1, characterized in that, In step S4, the laser power is 50–300 W, the pulse width is 290 fs–900 ps, ​​and the scanning speed is 2–5 mm / s.

4. The method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 1, characterized in that, Step S4 also includes adjusting the scanning trajectory of the auxiliary laser to achieve a uniform distribution of the nano-reinforcement phase.

5. The method for preparing high-temperature alloys by in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 1, characterized in that, The particle size of the powder is 40-120μm.

6. An application of in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing, characterized in that: The high-temperature alloy preparation method according to any one of claims 1-5 is used to prepare Ni-based, Co-based, Fe-based and high-entropy alloy systems.

7. The application of in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 6, characterized in that: In preparing the nickel-based alloy, the powder comprises, by mass percentage, the following raw materials: Mo: 8-10%, Cr: 20-25%, Fe: 15-20%, Co: 2-5%, W: 0.5-1%, C: 0-0.1%, Si: 0-0.1%, Ni: balance.

8. The application of in-situ generation of nano-reinforcing phases using dual-laser additive manufacturing according to claim 6, characterized in that: In preparing the high-entropy alloy, the powder comprises the following raw materials by mass percentage: Co: 22–24%, Cr: 18–20%, Fe: 18–20%, Mn: 18–20%, Ni: 18–20%, Al: 0.8–1.2%, Ti: 0.5–0.8%, C: 0–0.05%, O: ≤0.03%, balance being unavoidable impurities.

9. A high-temperature alloy, characterized in that, It is prepared by the high-temperature alloy preparation method of in-situ generation of nano-reinforcing phase using dual-laser additive manufacturing as described in any one of claims 1-5.

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