Laser powder bed molten nickel-based superalloy crack restraining and efficient forming method based on annular light beam

Abstract

The invention belongs to the field of metal additive manufacturing, and provides a laser powder bed molten nickel-based superalloy crack inhibiting and efficient forming method based on an annular light beam, which comprises the following steps: laying nickel-based superalloy powder on a substrate, and carrying out laser melting accumulation layer by layer by adopting the annular light beam to form a three-dimensional sample piece; according to the annular light beam, a Gaussian beam is shaped into an annular shape through an adjustable ring mode fiber laser or an optical diffraction element DOE, light spots are stably focused on the surface of a powder bed, light spot energy distribution is characterized in that the center is low, the edge is high, the diameter of the light spots is 120-220 microns, and the energy ratio of an annular belt to a core part is 3-10. According to the method, the annular light beam is adopted, laser energy space distribution is changed, limitation of traditional laser induced defects is broken through from the process level, and the problem that high-quality forming of the nickel-based high-temperature alloy (especially IN738 alloy) through the LPBF process is difficult to achieve is solved to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing and relates to a method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Laser Powder Bed Fusion (LPBF) is one of the most representative technologies in the field of metal additive manufacturing. Currently, most LPBF systems employ Gaussian laser beams, characterized by a high-energy distribution at the center and low-energy distribution at the edges. This heat source configuration easily leads to steep temperature gradients and extremely high cooling rates during actual forming, resulting in significant thermal stress concentration and promoting the initiation and propagation of microcracks. Furthermore, the non-uniform heat input caused by Gaussian lasers hinders the release of residual stress, ultimately affecting the integrity and reliability of the formed parts. This mismatch between materials and processes is particularly pronounced when forming difficult-to-weld nickel-based superalloys. Ring laser beams, with their ring-shaped distribution of low energy at the center and high energy at the edges, can significantly optimize the heat input method of the molten pool. Numerous studies have shown that residual stress is a necessary condition for crack initiation during additive manufacturing. The residual stress induced by ring beams is more evenly distributed, has lower values, and possesses stronger stress self-release capabilities, which overall contributes to improved forming stability and microstructure uniformity.

[0004] The rich elemental diversity of nickel-based superalloys endows them with excellent microstructural stability and high-temperature mechanical properties, but significantly weakens their formability in highly constrained forming processes (welding, additive manufacturing). Laser powder bed melting (LPBF) technology, due to its unique and extraordinary metallurgical characteristics, generates significant temperature gradients and residual stresses during forming. These extreme thermodynamic conditions, combined with the material properties of nickel-based superalloys (wide solidification temperature range, high proportion of strengthening phases, etc.), result in most alloys exhibiting extremely high crack susceptibility. This problem has become a key technological bottleneck restricting the large-scale application of nickel-based superalloys in laser additive manufacturing.

[0005] IN738 alloy is a typical precipitation-strengthened nickel-based superalloy widely used in high-temperature components such as gas turbines and aero engines. However, numerous experiments have confirmed that IN738 alloy is prone to hot cracking during LPBF forming, exhibiting extremely high cracking susceptibility. While various techniques, such as parameter optimization, the addition of ceramic phases, and compositional optimization, have mitigated crack formation to some extent, they typically come at the cost of increased cost or performance loss.

[0006] A study has disclosed a method for preparing highly formable aluminum alloy materials based on laser beam shaping, using a mirror and a conical mirror to shape the beam. However, this type of beam shaping method suffers from relatively poor beam uniformity, accuracy, and stability, as well as low light energy utilization. Due to the complex optical path structure, it is difficult to achieve precise control of energy distribution in different regions. Furthermore, the differences in the thermophysical properties and laser interaction mechanisms between aluminum alloys and nickel-based superalloys mean that the disclosed techniques applicable to aluminum alloys are insufficient to solve the LPBF forming crack problem in difficult-to-weld nickel-based superalloys (especially IN738 alloy). Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a method for crack suppression and efficient forming of nickel-based superalloys using a laser powder bed fusion process based on a ring beam. The invention's research reveals that using an adjustable ring-mode fiber laser or a DOE optical diffraction element for ring beam shaping, coupled with a specific energy ratio (3-10), can significantly improve crack suppression, thus solving to some extent the problem of achieving high-quality forming of nickel-based superalloys (especially IN738 alloy) using the LPBF process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal, comprising: Nickel-based high-temperature alloy powder is deposited on a substrate and then layer-by-layer laser melting and deposition is performed using a ring beam to form a three-dimensional sample. The ring beam is shaped into a ring using an adjustable ring-mode fiber laser or an optical diffraction element (DOE), so that the beam spot is stably focused on the powder bed surface. The beam spot energy distribution is characterized by low energy at the center and high energy at the edges. The beam spot diameter is 120-220 μm, and the energy ratio between the ring and the core is between 3 and 10.

[0009] Research has revealed that the bottleneck in the forming of difficult-to-weld superalloys using LPBF technology lies primarily in the mismatch between the heat input method and the material's solidification behavior. To address this, this invention employs a ring-shaped laser beam to alter the spatial distribution of laser energy, overcoming the limitations of traditional laser-induced defects at the process level and thus resolving, to some extent, the cracking problem in nickel-based superalloys (especially IN738 alloy).

[0010] It should be noted that theoretical studies show that a lower energy ratio between the ring and the core results in a smaller molten pool temperature gradient and better crack suppression. However, due to the high reflectivity of aluminum alloy powder, it is essential to ensure energy in the central region; that is, the energy ratio between the ring and the core cannot be too large. If the central energy is low, unmelted voids are likely to occur. Typically, this ratio should be less than 2. This invention targets difficult-to-weld nickel-based superalloys, which have worse formability than aluminum alloy LPBF. Therefore, the energy ratio between the ring and the core should be as small as possible to reduce the molten pool temperature gradient and residual thermal stress. Furthermore, the low reflectivity of nickel-based superalloys allows for a larger energy ratio between the ring and the core. Experimental findings show that setting the energy ratio to be greater than 3 ensures a smaller molten pool temperature gradient, lower residual stress, and a better crack suppression effect.

[0011] Meanwhile, due to the change in energy distribution, the molten pool stability of the ring light is better, which allows for the use of higher power and lower scanning speed without keyhole defects, which is beneficial for achieving large layer thickness forming. To this end, the present invention chooses to limit the energy ratio of the ring and the center to less than 10, so that the center still has a certain amount of energy to meet the needs of dense forming and high-efficiency forming of large layer thickness.

[0012] In a second aspect, the present invention provides a nickel-based superalloy prepared by the method described above.

[0013] Beneficial effects of the present invention (1) By using a ring laser beam instead of a traditional Gaussian beam, the present invention significantly reduces the temperature gradient and cooling rate at the center of the molten pool. The change in grain growth direction helps the melt filling process at the end of solidification and inhibits crack formation. In addition, due to the more balanced stress distribution, the adjustment of the residual stress direction helps the crack self-passivation and propagation inhibition. The density of the formed sample can reach more than 99.7%. (2) Experimental results show that, under optimized process parameters, the room temperature tensile strength of IN738 alloy formed by LPBF based on ring beam reaches 1050 MPa and the elongation after fracture reaches 11%, which is not much different from the tensile strength of the high-sinusoidal beam formed part, but the elongation after fracture increases by nearly 300%; after heat treatment, the room temperature tensile strength reaches 1120 MPa and the elongation after fracture reaches 8.0%, which is nearly 10% higher than the tensile strength of the high-sinusoidal beam formed part, but the elongation after fracture increases by nearly 300%; at 1100℃, the alloy tensile strength reaches 145 MPa and the elongation after fracture reaches 8%, which is nearly 23% higher than the tensile strength of the high-sinusoidal beam formed part, and the elongation after fracture decreases slightly.

[0014] (3) The method of the present invention does not rely on alloy composition modification or additional equipment configuration, and has strong versatility and industrialization feasibility.

[0015] (4) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 The diagram shows the energy distribution of a Gaussian beam (a) and a ring beam (b).

[0018] Figure 2 Metallographic images of deposited IN738 alloy formed by LPBF process under different beam patterns (Gaussian beam and ring beam) with the same parameters (40 μm layer thickness): (a) IN738 alloy formed in Comparative Example 1, (b) IN738 alloy formed in Example 1.

[0019] Figure 3 Scanning electron microscope images of IN738 alloy formed by LPBF process under Gaussian and ring beam morphologies (melt pool morphology and dendrite orientation at a layer thickness of -40 μm with the same parameters): (a) IN738 alloy formed in Comparative Example 1, (b) IN738 alloy formed in Example 1, and crack morphology generated during Gaussian beam forming: (c) and (d) IN738 alloy formed in Comparative Example 1.

[0020] Figure 4 Metallographic images of deposited IN738 alloy formed by LPBF process under ring beam under different layer thicknesses (120 μm, 140 μm) and different scanning intervals (130 μm, 150 μm): (a) IN738 alloy formed in Example 2, (b) IN738 alloy formed in Example 3, (c) IN738 alloy formed in Example 4, and (d) IN738 alloy formed in Example 5.

[0021] Figure 5 Stress-strain curves of IN738 alloy formed by LPBF process under Gaussian beam and ring beam conditions (room temperature: deposited state, heat-treated state; 1100 °C: heat-treated state): Gaussian beam is Comparative Example 1, and ring beam is Example 1. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or product instructions. Similarly, unless otherwise specified, the test methods of this invention are performed in accordance with conventional methods in the art or industry-standard methods or practices. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0024] Explanation of terms involved: The term "IN738" refers to a precipitation-strengthened nickel-based superalloy that possesses good strength, thermal stability, and oxidation resistance. However, it has poor formability under strong constraints (welding, additive manufacturing, etc.) and is prone to microcracks.

[0025] The term "thermal crack" refers to microcracks formed during the LPBF forming process, characterized by cracks parallel to the printing direction.

[0026] This invention provides a method for crack suppression and efficient forming of nickel-based superalloys using laser powder bed molten metal based on a ring beam, comprising: Nickel-based high-temperature alloy powder is deposited on a substrate and then layer-by-layer laser melting and deposition is performed using a ring beam to form a three-dimensional sample. The ring beam is shaped into a ring using an adjustable ring-mode fiber laser or an optical diffraction element (DOE), so that the beam spot is stably focused on the powder bed surface. The beam spot energy distribution is characterized by low energy at the center and high energy at the edges. The beam spot diameter is 120-220 μm, and the energy ratio between the ring and the core is between 3 and 10.

[0027] This invention addresses the hot-cracking susceptibility of nickel-based superalloys (especially IN738 alloy) by precisely limiting the energy ratio between the ring and the core. The wide and shallow molten pool induced by the annular beam and the symmetrical thermal stress release path help mitigate the synergistic effect of liquid film separation and grain boundary stress concentration caused by rapid solidification, thereby reducing the susceptibility to solidification cracks. At the same time, the optimized temperature gradient direction can weaken the intergranular segregation drive and suppress the excessive accumulation of brittle elements (such as B and Zr) at the grain boundaries, further enhancing the material's crack resistance.

[0028] Secondly, the ring beam in this invention adopts an axisymmetric ring energy distribution structure, which can simultaneously reduce the heat input in the central region of the molten pool and enhance the heat input in the surrounding region, thereby expanding the lateral heat diffusion range, increasing the size of the molten pool, reducing the depth-to-width ratio of the molten pool, and enhancing the thermal stability of the molten pool. Finally, compared with shaping by mirrors or conical mirrors, the present invention uses DOE modules or dedicated ring lasers to provide a more stable and uniform energy distribution, thereby better controlling the thermal flow field of the molten pool and reducing the risk of hot cracking.

[0029] The selection of the substrate needs to take into account factors such as the material's coefficient of thermal expansion, wettability, chemical stability, and heat treatment characteristics. Therefore, this invention has studied the material of the substrate. In some embodiments, the substrate material is alloy steel / nickel-based alloy to obtain better forming effect of nickel-based high-temperature alloys (especially IN738 alloy).

[0030] Particle size is one of the key factors affecting the forming quality of alloys. The particle size of nickel-based alloy powder should be moderate, ensuring that the powder can be evenly spread on the substrate surface while also ensuring sufficient melting during the cladding process. In some embodiments, the particle size distribution of the nickel-based superalloy is 15-53 μm to obtain better forming results and reduce crack formation.

[0031] In some embodiments, the nickel-based superalloy is IN738 alloy, which is composed of the following weight percentages: Al: 3.2-3.7 wt.%; Ti: 3.0-3.5 wt.%; Cr: 15.7-16.3 wt.%; Co: 8.0-9.0 wt.%; W: 2.4-2.8 wt.%; Mo: 1.5-2.5 wt.%; Ta: 1.5-2.0 wt.%; Nb: 0.6-1.1 wt.%; C: 0.1-0.2 wt.%; B: 0.005-0.015 wt.%; Zr: 0.05-0.15 wt.%; with the balance being Ni. Using this proportion of gas-atomized IN738 alloy (domestic grade: K438, composition according to GB / T 14992) powder results in superior forming performance.

[0032] Common scanning methods in industrial welding include interlayer rotation of 0°, 67°, and 90°. This invention has found that selecting the latter two interlayer rotation angles can better reduce crack density. Therefore, in some embodiments, the process parameters for the layer-by-layer laser melting and deposition are: laser power of 180-460 W, scanning speed of 400-1500 mm / s, layer thickness of 30-180 μm, scanning spacing of 60-200 μm, and the scanning strategy employing interlayer rotation of 67° or 90° with alternating scanning. The forming atmosphere is an inert atmosphere. This invention's method requires no additional energy field, additional process steps, or composition adjustments. It optimizes the molten pool thermal field and solidification behavior simply by adjusting the laser energy distribution, exhibiting good process compatibility and engineering feasibility. It is suitable for high-quality additive manufacturing of nickel-based superalloys (such as IN738). By combining the matching relationship between different layer thicknesses and scanning spacing, the ring beam exhibits excellent process adaptability and is suitable for a wider parameter window. Therefore, in some implementations, the layer thickness is 80–180 μm and the scanning spacing is 110–180 μm, so as to significantly improve the forming efficiency while ensuring the forming density and surface quality. The method of the present invention is not limited to IN738 alloy, but can also be applied to other difficult-to-weld nickel-based alloy powders. Preferably, the total content of Al, Ti and Ta in the nickel-based superalloy is >5 wt.%, and more preferably, the nickel-based superalloy is IN939, CM247LC, etc.

[0033] In some implementations, mechanical polishing and ultrasonic cleaning with ethanol are used to remove oxides and oil from the substrate surface to ensure that the substrate surface is clean before molding.

[0034] More specifically, including: (1) Substrate treatment: Alloy steel / nickel-based alloy is selected as the substrate material. Mechanical grinding and ultrasonic cleaning with ethanol are used to remove surface oxides and oil stains to ensure that the substrate surface is clean before forming. (2) Powder preparation: Gas-atomized IN738 alloy (domestic grade: K438, composition according to GB / T 14992) powder with a particle size distribution of 15~53 μm was selected. Its chemical composition range is: Al: 3.2~3.7 wt.%; Ti: 3.0~3.5 wt.%; Cr: 15.7~16.3 wt.%; Co: 8.0~9.0 wt.%; W: 2.4~2.8 wt.%; Mo: 1.5~2.5 wt.%; Ta: 1.5~2.0 wt.%; Nb: 0.6~1.1 wt.%; C: 0.1~0.2 wt.%; B: 0.005~0.015 wt.%; Zr: 0.05~0.15 wt.%; balance is Ni; (3) Laser system configuration: A tunable ring-mode fiber laser or an optical diffraction element (DOE) is used to shape the Gaussian beam into a ring. The energy distribution of the spot is characterized by low energy at the center and high energy at the edge. The spot diameter is 120~220 μm. The energy ratio between the ring and the core is required to be between 3 and 10. While ensuring a low temperature gradient, sufficient energy is ensured to achieve dense shaping. The optical system is used to achieve stable focusing of the spot on the powder bed surface. (4) Setting of forming parameters: laser power is 180~460 W, scanning speed is 400~1500 mm / s, layer thickness is 30~180 μm, scanning spacing is 60~200 μm, scanning strategy adopts interlayer rotation 67° / 90° staggered scanning, and forming atmosphere is high-purity argon (≥99.999%). (5) Sample preparation: Under the above conditions, powder laying and layer-by-layer laser melting and deposition are completed to complete the preparation of three-dimensional sample.

[0035] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0036] Comparative Example 1: In this comparative example, the IN738 alloy was formed using the commonly used Gaussian beam LPBF process in industry and subjected to room temperature / high temperature (1100 ℃) tensile property tests, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder with D50 of 32.1 μm was selected for LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Cr: 15.77%; Co: 8.61%; W: 2.68%; Mo: 1.77%; Al: 3.55%; Ti: 3.41%; Nb: 0.84%; Ta: 1.72%; C: 0.14%; B: 0.008%; Zr: 0.11%; balance is Ni.

[0037] (2) IN738 alloy powder was formed by LPBF using MT280 metal additive manufacturing equipment. The detailed process parameters are as follows: laser power 280 W, scanning speed 900 mm / s, layer thickness 40 μm, scanning spacing 90 μm, and interlayer rotation 67°.

[0038] (3) The deposited alloy was observed using a metallographic microscope and a scanning electron microscope. The formed sample was heat-treated using a tube furnace. The mechanical properties of the printed (As-built, AB) and heat-treated (Heat treatment, HT) samples were tested at room temperature / high temperature (1100 ℃) using a mechanical testing machine.

[0039] Example 1: In this embodiment, the IN738 alloy is formed using the ring beam LPBF process and subjected to room temperature / high temperature (1100 ℃) tensile property testing, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder obtained by vacuum atomization with a D50 of 31.3 μm was selected for ring beam LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Co: 8.34%; Cr: 16.11%; W: 2.45%; Mo: 1.69%; Al: 3.41%; Ti: 3.44%; Ta: 1.78%; Nb: 0.72%; C: 0.14%; B: 0.01%; Zr: 0.09%; balance is Ni; (2) The Gaussian beam of MT280 was shaped into a ring beam using the DOE module. The beam diameter was 170 μm and the energy ratio of the ring to the core was 7:1. Then, the device was used to perform LPBF forming on IN738 alloy powder. The detailed process parameters are as follows: laser power 280 W, scanning speed 900 mm / s, layer thickness 40 μm, scanning spacing 90 μm, and interlayer rotation 67°.

[0040] (3) The deposited alloy was observed using a metallographic microscope and a scanning electron microscope. The formed sample was heat-treated using a tube furnace. The mechanical properties of the AB and HT alloys were tested at room temperature / high temperature (1100 ℃) using a mechanical testing machine.

[0041] Example 2: In this embodiment, the IN738 alloy is formed using the ring beam LPBF process and then subjected to metallographic observation, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder obtained by vacuum atomization with a D50 of 33.4 μm was selected for ring beam LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Co: 8.77%; Cr: 16.22%; W: 2.65%; Mo: 1.66%; Al: 3.36%; Ti: 3.30%; Ta: 1.72%; Nb: 0.93%; C: 0.15%; B: 0.009%; Zr: 0.12%; balance is Ni; (2) The Gaussian beam of MT280 was shaped into a ring beam using the DOE module. The beam diameter was 156 μm and the energy ratio of the ring to the core was 5:1. Then, the device was used to form IN738 alloy powder by LPBF. The detailed process parameters are as follows: laser power 360 W, scanning speed 800 mm / s, layer thickness 120 μm, scanning spacing 90 μm, interlayer rotation 67°, and the deposition state formation was observed using an optical microscope.

[0042] Example 3: In this embodiment, the IN738 alloy is formed using the ring beam LPBF process and then subjected to metallographic observation, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder obtained by vacuum atomization with a D50 of 34.1 μm was selected for ring beam LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Co: 8.67%; Cr: 16.27%; W: 2.68%; Mo: 1.77%; Al: 3.46%; Ti: 3.32%; Ta: 1.78%; Nb: 0.73%; C: 0.15%; B: 0.009%; Zr: 0.12%; balance is Ni; (2) The Gaussian beam of MT280 was shaped into a ring beam using the DOE module. The beam diameter was 178 μm and the energy ratio of the ring to the core was 4:1. Then, the device was used to form IN738 alloy powder by LPBF. The detailed process parameters are as follows: laser power 460 W, scanning speed 900 mm / s, layer thickness 140 μm, scanning spacing 90 μm, interlayer rotation 67°, and the deposition state formation was observed using an optical microscope.

[0043] Example 4: In this embodiment, the IN738 alloy is formed using the ring beam LPBF process and then subjected to metallographic observation, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder obtained by vacuum atomization with a D50 of 34.7 μm was selected for ring beam LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Co: 8.26%; Cr: 15.67%; W: 2.55%; Mo: 1.89%; Al: 3.23%; Ti: 3.12%; Ta: 1.98%; Nb: 0.76%; C: 0.13%; B: 0.009%; Zr: 0.13%; balance Ni; (2) The Gaussian beam of MT280 was shaped into a ring beam using the DOE module. The beam diameter was 154 μm and the energy ratio of the ring to the core was 7:2. Then, the device was used to form IN738 alloy powder by LPBF. The detailed process parameters are as follows: laser power 320 W, scanning speed 900 mm / s, layer thickness 40 μm, scanning spacing 130 μm, interlayer rotation 67°, and the deposition state formation was observed using an optical microscope.

[0044] Example 5: In this embodiment, the IN738 alloy is formed using the ring beam LPBF process and then subjected to metallographic observation, including the following steps: The specific preparation method is as follows: (1) IN738 alloy powder obtained by vacuum atomization with a D50 of 33.9 μm was selected for ring beam LPBF forming test. The elements contained in IN738 alloy and the mass percentage of each element are as follows: Co: 8.11%; Cr: 16.23%; W: 2.87%; Mo: 1.5%; Al: 3.63%; Ti: 3.44%; Ta: 1.65%; Nb: 0.85%; C: 0.15%; B: 0.01%; Zr: 0.10%; balance is Ni; (2) The Gaussian beam of MT280 was shaped into a ring beam using the DOE module. The beam diameter was 196 μm and the energy ratio of the ring to the core was 3:1. Then, the device was used to form IN738 alloy powder by LPBF. The detailed process parameters are as follows: laser power 360 W, scanning speed 1000 mm / s, layer thickness 40 μm, scanning spacing 150 μm, interlayer rotation 90°, and the deposition state formation was observed using an optical microscope.

[0045] Taking the IN738 alloy prepared in the comparative example and the embodiment as an example, the test results of its various properties are as follows: Figure 1-4 As shown.

[0046] Figure 1 As shown, Figure 1 Image (a) is a schematic diagram of the energy distribution of a Gaussian beam. It can be seen that the energy is high in the middle and low at the edges. Figure 1 (b) is a schematic diagram of the energy distribution of the ring beam after DOE shaping. It can be seen that most of the energy in the middle is shielded, and the energy distribution is characterized by low energy in the middle and high energy at the edges.

[0047] Figure 2 As shown, Figure 2 The middle image (a) is a metallographic image of IN738 alloy formed by Gaussian beam LPBF. It can be seen that there are a large number of microcracks inside the alloy, indicating poor forming quality. Figure 2 (b) is a metallographic image of IN738 alloy formed by LPBF with a ring beam. It can be seen that there are no cracks inside the alloy, only a very small number of pores, and the forming quality is excellent.

[0048] Figure 3 As shown, Figure 3 The middle (a) is a scanning electron microscope image of the molten pool morphology and dendrite growth orientation of IN738 alloy formed by Gaussian beam LPBF. It can be seen that the molten pool has a large depth-to-width ratio, the molten pool is nearly U-shaped, and the dendrite growth direction varies greatly at different positions of the molten pool. Figure 3 (b) is a scanning electron microscope image of the molten pool morphology and dendrite growth orientation of IN738 alloy formed by LPBF with annular beam. It can be seen that the molten pool has a small depth-to-width ratio and a nearly flat bottom. The dendrite growth direction is mostly the same at different positions of the molten pool and tends to be parallel to the forming direction. The dendrites span multiple molten pools. Figure 3(c, d) shows the crack morphology in IN738 alloy formed by Gaussian beam LPBF. It can be seen that the crack opening direction is consistent with the dendrite direction, indicating that the ring beam may suppress the cracks with a dendrite orientation that is relatively consistent with the dendrite orientation, which is beneficial to melt flow and feeding in the final stage of solidification. Figure 4 As shown, Figure 4 The images shown in the middle (ad) are metallographic images of IN738 alloy formed by annular beam LPBF with layer thicknesses of 120 / 140 μm and scanning intervals of 130 / 150 μm, respectively. It can be seen that no cracks are present inside the alloy, only a small number of pores. Note: Other forming parameters are presented in Examples 2-5.

[0049] Figure 5 As shown, Figure 5 In the middle (a, b), the room temperature stress-strain curves of IN738 alloy formed by Gaussian beam and ring beam LPBF in the deposited state and heat-treated state are shown. It can be seen that the alloy formed by ring beam in both the deposited state and the heat-treated state has better comprehensive mechanical properties and the elongation is increased by nearly 300%. Figure 5 (c) shows the stress-strain curves of IN738 alloy formed by Gaussian beam and ring beam LPBF under heat treatment at 1100 ℃. It can be seen that the tensile strength of the sample formed by ring beam is increased by nearly 25%, while the elongation is not significantly different.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for crack suppression and efficient forming of nickel-based superalloys using laser powder bed molten metal based on a ring beam, characterized in that, include: Nickel-based high-temperature alloy powder is deposited on a substrate and then layer-by-layer laser melting and deposition is performed using a ring beam to form a three-dimensional sample. The ring beam is shaped into a ring using an adjustable ring-mode fiber laser or an optical diffraction element (DOE), so that the beam spot is stably focused on the powder bed surface. The beam spot energy distribution is characterized by low energy at the center and high energy at the edges. The beam spot diameter is 120-220 μm, and the energy ratio between the ring and the core is between 3 and 10.

2. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, The substrate is made of alloy steel / nickel-based alloy.

3. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, The particle size distribution of the nickel-based superalloy is 15-53 μm.

4. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, The nickel-based superalloy is IN738 alloy, which is composed of the following components by weight percentage: Al: 3.2-3.7 wt.%; Ti: 3.0-3.5 wt.%; Cr: 15.7-16.3 wt.%; Co: 8.0-9.0 wt.%; W: 2.4-2.8 wt.%; Mo: 1.5-2.5 wt.%; Ta: 1.5-2.0 wt.%; Nb: 0.6-1.1 wt.%; C: 0.1-0.2 wt.%; B: 0.005-0.015 wt.%; Zr: 0.05-0.15 wt.%; with the balance being Ni.

5. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, The operating parameters for the layer-by-layer laser melting and deposition are: laser power of 180-460 W, scanning speed of 400-1500 mm / s, layer thickness of 30-180 μm, scanning spacing of 60-200 μm, scanning strategy of interlayer rotation of 67° / 90° staggered scanning, and forming atmosphere of inert atmosphere.

6. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, The layer thickness is 80–180 μm, and the scanning spacing is 110–180 μm.

7. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, In the nickel-based superalloy, the total content of Al, Ti, and Ta is >5 wt.%.

8. The method for crack suppression and efficient forming of nickel-based superalloys based on a ring beam laser powder bed molten metal as described in claim 1, characterized in that, Mechanical polishing and ultrasonic cleaning with ethanol were used to remove oxides and oil stains from the substrate surface.

9. The nickel-based superalloy prepared by the method according to any one of claims 1-8.

10. The application of a ring beam in reducing the crack sensitivity of laser powder bed forming of nickel-based superalloys, characterized in that, The scanning strategy employs interlayer rotation of 67° / 90° staggered scanning.

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