A method of ultrasonic assisted, compositionally graded, interlaminar impact composite additive manufacturing of a gh4099 alloy component

Abstract

The present application relates to the technical field of metal additive manufacturing, and particularly relates to a method for preparing a GH4099 alloy component by ultrasonic assistance, composition gradient and interlayer impact composite additive manufacturing. The present application adopts GH4099 alloy powder, and a first forming area of the alloy component is prepared on a substrate by a laser powder bed melting process; GH4099 alloy composite powder is adopted on the first forming area, and a second forming area of the alloy component is prepared by layer-by-layer deposition through a laser directional energy deposition process, so that a formed alloy component is obtained; the formed alloy component is subjected to solid solution treatment and aging treatment, so that a GH4099 alloy component is obtained; the laser directional energy deposition process is carried out at the same time, and an online ultrasonic assistance, gradient oxide dispersion strengthening design and periodic interlayer laser impact strengthening are applied. Through the above three kinds of auxiliary designs, the present application realizes the organization refinement, performance improvement and residual stress synergistic regulation of the GH4099 alloy component.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and in particular to a method for preparing GH4099 alloy components by ultrasonic-assisted, compositional gradient, and interlayer impact composite additive manufacturing. Background Technology

[0002] Laser composite additive manufacturing technology, which combines laser powder bed fusion (LPBF) and laser directed energy deposition (LDED), provides an innovative solution for the integrated and efficient manufacturing of large aerospace components. This technology fully leverages the complementary advantages of the two processes, utilizing LPBF to form high-precision, complex feature structures and employing LDED to efficiently stack large-size, simple geometric regions, thereby significantly shortening the manufacturing cycle, reducing subsequent machining, and lowering iteration costs.

[0003] However, during this composite manufacturing process, the LPBF and LDED regions exhibit drastically different microstructures due to significant differences in heat input modes and cooling rates, with the most critical difference being the substantial variation in grain size. This difference directly leads to a mismatch in the response behavior and final mechanical properties of the two regions during subsequent heat treatment, becoming a key technical bottleneck restricting the overall performance of the composite component.

[0004] In the LDED region, due to high heat input and relatively slow cooling rate, epitaxial growth easily occurs at the bottom of the molten pool, using the solidified layer as a substrate, forming a coarse columnar grain structure. More importantly, with increasing deposition height, the heat accumulation effect intensifies, leading to a gradient increase in grain size from bottom to top, with particularly coarse grains in the top region. This coarse columnar grain structure promotes the precipitation of large, bulky carbides at grain boundaries and also provides conditions for the coarsening and non-uniform distribution of the γ′ strengthening phase. For precipitation-strengthened nickel-based superalloys like GH4099, coarse grains and unfavorable precipitate distribution severely impair their strength and ductility. In contrast, the LPBF region, due to its extremely high cooling rate, achieves a uniform and fine grain structure, with internal precipitates not yet fully formed. In the subsequent solution-aging heat treatment uniformly applied to the entire component, the two regions exhibited significant differences in their responses to the same heat treatment regime: the fine-grained LPBF region successfully recrystallized and obtained a uniform and fine γ′ strengthening phase, resulting in a substantial improvement in performance; however, the LDED region, due to the pinning effect of coarse grain boundary carbides and its low initial dislocation density, experienced hindered recrystallization, and the precipitation strengthening effect of the γ′ phase was insufficient. Ultimately, the LDED region became the bottleneck in overall performance, and the plasticity mismatch between it and the LPBF region easily led to early failure of the component during service.

[0005] Therefore, the key to improving the performance of composite components lies in the targeted optimization of the microstructure in the LDED region, with the core objective being grain refinement. This requires a multi-dimensional approach: First, suppressing columnar epitaxial growth and promoting equiaxed crystal formation during deposition to directly obtain a refined initial microstructure. This can be achieved by optimizing process parameters to reduce energy input, increasing cooling rates, introducing heterogeneous nucleation sites to improve the nucleation rate and refine grains, or applying ultrasonic external fields to agitate the molten pool and interrupt columnar epitaxial growth. Second, introducing additional deformation storage energy during or after deposition to enhance recrystallization capabilities during subsequent heat treatment, indirectly achieving microstructure refinement. This can be achieved through techniques such as laser shock peening. Specific measures include introducing nanoparticles as nucleating agents during LDED, adding ultrasonic external fields to break dendrites and refine grains, and using laser shock peening to introduce high-density dislocations and residual compressive stress on the surface. However, while single oxide dispersion strengthening (ODS) design can provide heterogeneous nucleation sites, its refining effect may be weakened with heat accumulation under the high heat input of LDED, and may exacerbate abrupt changes in composition and properties at the interface. Single laser shock peening (LSP) post-treatment can improve the surface stress state, but it is difficult to intervene in the already formed coarse solidified structure and has limited impact on deeper structures. Conventional ultrasound-assisted treatment is also ineffective in suppressing grain gradient coarsening caused by continuous heat accumulation. Therefore, a composite method capable of synergistically controlling composition, solidification process, and stress state from multiple dimensions is urgently needed to systematically solve the core problems of coarse structure and uneven properties in the LDED region. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing GH4099 alloy components using ultrasonic-assisted, composition-gradient, and interlaminar impact composite additive manufacturing. This method integrates three composite processes during the LDED process: gradient ODS powder design, non-contact ultrasonic molten pool assistance, and periodic interlaminar laser shock strengthening. These processes work synergistically from the three dimensions of composition, microstructure, and stress, aiming to significantly refine the grains in the LDED region, improve its comprehensive mechanical properties, and effectively manage residual stress. Ultimately, this results in composite additive manufacturing components with highly matched properties between the LPBF region and the LDED region, and excellent overall plasticity uniformity.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: One of the technical solutions of this invention provides a method for preparing GH4099 alloy components, comprising the following steps: (1) Using GH4099 alloy powder, the first forming area of ​​the alloy component is prepared on the substrate by laser powder bed melting process under an inert atmosphere; (2) GH4099 alloy composite powder is deposited layer by layer on the first forming area by laser directional energy deposition process to prepare the second forming area of ​​the alloy component, and the formed alloy component is obtained. (3) The formed alloy components are subjected to solution treatment and aging treatment to obtain GH4099 alloy components; In step (2), the GH4099 alloy composite powder is composed of GH4099 alloy powder and yttrium oxide, wherein the mass fraction of yttrium oxide in the GH4099 alloy composite powder varies in a predetermined gradient along the deposition height direction; In step (2), while the laser-directed energy deposition process is being carried out, the deposited molten pool is subjected to non-contact ultrasonic treatment. In step (2), when the laser directional energy deposition process is performed, after each preset N layers are deposited, the deposition process is paused, and the top surface that has been deposited is subjected to full-coverage laser shock treatment, where N is 3~8 and N is an integer.

[0008] The second technical solution of the present invention provides a GH4099 alloy component prepared by the above-mentioned preparation method.

[0009] This invention employs gradient ODS design to achieve adaptive regulation in space, using low ODS content at the interface to avoid microstructure discontinuities caused by abrupt compositional changes, and high ODS content at the top to enhance grain refinement, thereby matching the thermal accumulation effect. Simultaneous ultrasonic assistance refines grains instantly during molten pool solidification, forming an in-situ composite grain refinement effect with the gradient ODS. Periodic interlayer LSP (Laminated Stress Particle Size) interrupts and resets the stress field during manufacturing, not only inhibiting crack initiation but also introducing high-density dislocations that provide additional driving force for recrystallization during subsequent heat treatment. This driving force, combined with the heterogeneous nucleation sites introduced by the gradient ODS, produces a synergistic strengthening effect that promotes recrystallization in the LDED (Low-Density Surface-Earned Defect) region. The synergistic effect of these three factors ultimately results in a multi-scale, superior microstructure in the LDED region of the composite component, characterized by a smooth interface transition, overall grain refinement, and optimized surface stress state, thus significantly improving overall plasticity uniformity.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. Multi-scale synergistic regulation to systematically solve the problem of uneven performance: This invention focuses on three core processes: gradient ODS composition design, online ultrasonic microstructure refinement, and periodic interlaminar stress regulation, achieving multi-dimensional synergistic effects. Gradient ODS lays the foundation at the compositional level, mitigating abrupt changes in interfacial microstructure; ultrasonic assistance intervenes in the solidification process, directly refining grains and enhancing the intrinsic plasticity of the LDED region; and interlaminar LSP (laser shock peening) manages the stress field, eliminating the risk of cracking. These three processes work synergistically from the perspectives of macroscopic interface, microstructure, and internal stress state, systematically solving the core problem of uneven plasticity in LPBF / LDED composite components.

[0011] 2. Significantly Improved Strength-Plasticity Matching in the LDED Region: Ultrasonic assistance ensures that the LDED region obtains fine equiaxed or fragmented columnar crystal structures. Combined with the dispersion strengthening effect of gradient ODS, the strength of the LDED region is effectively improved. The fine-grained structure itself can coordinate deformation and delay stress concentration, which is conducive to improving plasticity. Ultimately, the mechanical properties of the LDED region, especially its plasticity, can be matched to the LPBF region to the greatest extent, eliminating performance shortcomings.

[0012] 3. Effectively suppress manufacturing defects and improve forming reliability: Periodic interlayer LSP treatment is equivalent to introducing a stress relief valve in the deposition process, periodically eliminating high tensile stress, and turning the stress state into favorable compressive stress. This greatly reduces the tendency of high γ′ phase content GH4099 alloy to crack during LDED, broadens the process window for manufacturing complex components, and improves the forming success rate.

[0013] 4. Achieving uniformity and optimization of overall component performance: The final composite component exhibits a significantly reduced performance gradient between the LPBF and LDED regions, resulting in a more uniform overall plasticity distribution. This enhances the component's strain coordination under complex loads, effectively preventing premature local failures and significantly improving its reliability and service life in harsh operating environments such as aero-engines. This achieves the invention's ultimate goal of a smooth performance gradient and excellent overall plasticity-toughness matching.

[0014] 5. Industrial Applicability: The ultrasonic-assisted, compositional gradient, and interlaminar impact composite additive manufacturing method for GH4099 alloy components described in this invention is particularly suitable for the manufacture of large-size nickel-based superalloy components in the aerospace field that require high performance uniformity, reliability, and complexity, such as integral bladed disks, turbine casings, diffuser shells, and load-bearing frames. By integrating multiple processes into online composite and synergistic control during LDED deposition, active and precise control is achieved for the microstructure refinement, performance improvement, and stress optimization of weak points (LDED regions) in composite additive manufactured components. This significantly improves the overall service performance and lifespan of the components, demonstrating significant engineering application value and industrialization prospects. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the laser composite additive manufacturing process described in this invention; Figure 2 This is a schematic diagram of the interlayer laser shock peening process described in this invention; Figure 3 The metallographic images of the LPBF-LDED composite deposited part in Comparative Example 1 without the composite auxiliary process are shown, where (a) is the metallographic structure of the LPBF region and (b) is the metallographic structure of the LDED region. Figure 4 The image shows the microstructure of the LPBF-LDED composite deposit prepared by the method of the present invention in Example 1, where (a) is the microstructure of the LPBF region and (b) is the microstructure of the LDED region. Figure 5 This is a comparison chart of the room temperature tensile stress-strain curves of Example 1 and Comparative Example 1. Detailed Implementation

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0018] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0020] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0022] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.

[0023] This invention addresses the technical bottlenecks in the composite additive manufacturing of GH4099 alloy components using laser powder bed melting (LDED) and laser directed energy deposition (LDED). These bottlenecks arise from high heat input and continuous heat accumulation in the LDED region, leading to coarse grains, severe microstructure gradients, and high residual tensile stress, resulting in performance mismatch with the LPBF region and susceptibility to cracking. The invention proposes an ultrasonic-assisted, compositional gradient, and interlaminar shock-strength composite additive manufacturing method. This method integrates three composite auxiliary processes simultaneously during LDED deposition: gradient ODS powder supply, which spatially achieves adaptive compositional control to mitigate interface abrupt changes and provide heterogeneous nucleation sites for recrystallization, effectively alleviating interface microstructure abrupt changes; non-contact ultrasonic-assisted melt pool treatment, which interrupts columnar crystal epitaxial growth and refines grains at the moment of solidification, improving strength and plasticity; and periodic interlaminar laser shock strengthening, which periodically introduces high-density dislocations and residual compressive stress during manufacturing, providing recrystallization driving force for subsequent heat treatment and suppressing cracking. The three components work synergistically to ultimately obtain a composite additive manufacturing component with highly matched microstructure and properties between the LPBF and LDED regions and excellent overall plasticity uniformity, providing an integrated forming solution for the high-quality fabrication of complex high-performance high-temperature alloy structural parts.

[0024] This invention provides a method for preparing GH4099 alloy components, comprising the following steps: (1) Using GH4099 alloy powder, the first forming area of ​​the alloy component is prepared on the substrate by laser powder bed melting process under an inert atmosphere; (2) GH4099 alloy composite powder is deposited layer by layer on the first forming area by laser directional energy deposition process to prepare the second forming area of ​​the alloy component, and the formed alloy component is obtained. (3) The formed alloy components are subjected to solution treatment and aging treatment to obtain GH4099 alloy components; In step (2), the GH4099 alloy composite powder is composed of GH4099 alloy powder and yttrium oxide, wherein the mass fraction of yttrium oxide in the GH4099 alloy composite powder varies in a predetermined gradient along the deposition height direction; In step (2), while the laser-directed energy deposition process is being carried out, the deposited molten pool is subjected to non-contact ultrasonic treatment. In step (2), when the laser directional energy deposition process is performed, after each preset N layers are deposited, the deposition process is paused, and the top surface that has been deposited is subjected to full-coverage laser shock treatment, where N is 3~8 and N is an integer.

[0025] Step (1) of this invention is to use GH4099 alloy powder to prepare a first forming region with high precision or complex assembly characteristics on a substrate by laser powder bed melting process under an inert atmosphere. This region constitutes the basic or precision part of the component.

[0026] In some embodiments of the present invention, the process parameters of the laser powder bed melting process are: laser power 120W, scanning speed 1100 mm / s, scanning spacing 0.06 mm, and layer thickness 0.02 mm.

[0027] In this invention, the inert atmosphere includes argon.

[0028] Step (2) of this invention involves depositing GH4099 alloy composite powder layer by layer on the first forming region using laser-directed energy deposition (LDED) technology to prepare the second forming region of the alloy component, thereby obtaining the formed alloy component. During the LED process, the following three composite auxiliary processes are performed simultaneously: Step (2a) Gradient ODS Powder Synchronous Deposition: A pre-mixed composite powder, consisting of GH4099 alloy powder and Y2O3 nanoparticles, is supplied to the laser directional energy deposition powder feeding system; and through real-time calculation and metering control, the mass fraction of Y2O3 nanoparticles in the composite powder changes in a preset gradient along the deposition height direction. Step (2b) Ultrasonic Assisted Molten Pool Treatment: During LDED deposition, the transmitter head of the non-contact ultrasonic generator is aligned with and applied to the current molten pool, and the transmitter head moves synchronously with the deposition head of the laser directional energy deposition. Step (2c) Periodic interlayer laser shock enhancement: After each preset N layers are deposited, the LDED deposition process is paused, and the uppermost surface of the deposited layer is subjected to full-coverage laser shock treatment using an integrated laser shock enhancement device; where N is an integer from 3 to 8.

[0029] In this invention, the first forming region is preferably a high-precision region of the GH4099 alloy component, and the second forming region is preferably a simple region of the large-size shape of the GH4099 alloy component.

[0030] In some embodiments of the present invention, the process parameters of the laser-directed energy deposition process are as follows: laser power 700~800W (e.g., 700W, 750W, 780W or 800W, etc.), spot diameter 3 mm, scanning speed 4~6 mm / s (e.g., 4mm / s, 5mm / s, 5.5mm / s or 6mm / s, etc.), powder feed rate 7~10 g / min (e.g., 7 g / min, 8 g / min, 9 g / min or 10 g / min, etc.), and single-layer lifting height 0.65 mm.

[0031] In this invention, the mass fraction gradient of yttrium oxide is designed as follows: the content is low in the initial deposition layer near the LPBF / LDED interface, and the content gradually increases with the deposition height; the yttrium oxide content in the initial deposition layer of the second forming region is 0.05~0.15 wt.%, for example, it can be 0.05 wt.%, 0.1 wt.%, or 0.15 wt.%, etc., and gradually increases with the deposition height until the yttrium oxide content in the top deposition layer is 0.3~0.5 wt.%, for example, it can be 0.3 wt.%, 0.4 wt.%, or 0.5 wt.%, etc.

[0032] In this invention, there are no restrictions on the selection of GH4099 alloy powder, as long as it is suitable for laser powder bed melting process and laser directed energy deposition process. In some embodiments of this invention, the GH4099 alloy powder is a high-temperature alloy (GH4099) spherical powder; the particle size distribution of the GH4099 alloy powder is 15~53μm (suitable for laser powder bed melting process) or 45~105μm (suitable for laser directed energy deposition process).

[0033] In this invention, the process parameters for the non-contact ultrasonic treatment are as follows: the ultrasonic frequency is 20~100kHz, for example, it can be 20kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz or 100kHz, etc.; the vertical distance between the end face of the ultrasonic transmitter and the surface of the molten pool is 50~150 mm, for example, it can be 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 120mm or 150mm, etc.; and the sound pressure acting on the molten pool is 0.5~10 MPa, for example, it can be 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa or 10 MPa, etc.

[0034] In this invention, the process parameters of the full-coverage laser shock treatment are as follows: the laser pulse energy is 5~15J, for example, 5J, 10J or 15J, etc.; the pulse width is 10~20ns, for example, 10ns, 15ns or 20ns, etc.; the spot diameter is 2~4mm, for example, 2mm, 3mm or 4mm, etc.; the spot overlap rate is 50~70%, for example, 50%, 60% or 70%, etc.; each point is impacted 1~5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times; the number of deposition layers N between each round of shock treatment is preferably 4~6 layers, for example, 4 layers, 5 layers or 6 layers.

[0035] In this invention, the temperature of the surface to be impacted must be kept below 200°C before full-coverage laser shock treatment.

[0036] In some embodiments of the present invention, the temperature of the deposition surface to be impacted is ensured to drop below 200°C by online temperature monitoring, and then the surface is subjected to laser shock peening treatment; before laser shock peening, an absorption layer and a constraint layer are automatically formed in the area to be impacted, and after the impact is completed, the residual absorption layer on the surface is removed.

[0037] Step (3) of this invention is to perform solution treatment and aging treatment on the formed alloy component to obtain the desired final microstructure and mechanical properties, thereby obtaining the GH4099 alloy component.

[0038] In this invention, the solution treatment temperature is 1140~1180℃, for example, 1140℃, 1150℃, 1160℃ or 1180℃, etc., and the time is 1~4h, for example, 1h, 2h, 3h or 4h, etc., and after the solution treatment is completed, air cooling or oil quenching is performed.

[0039] In this invention, the aging treatment temperature is 760~820℃, for example, 760℃, 780℃, 800℃ or 820℃, etc., and the time is 16~24h, for example, 16h, 18h, 20h, 22h or 24h, etc., and air cooling is performed after the aging treatment.

[0040] The present invention also provides a GH4099 alloy component prepared by the above-described preparation method. The LDED region of the GH4099 alloy component has a gradient refined structure with gradually increasing grain size from the interface to the top, and the surface layer has a residual compressive stress layer introduced by laser shock strengthening. The overall average plasticity of the component is improved by no less than 80% compared with the control component with the same process parameters but without the treatment of steps (2a), (2b) and (2c).

[0041] In some embodiments of the present invention, the GH4099 alloy component is a GH4099 alloy simulation part comprising a lower complex mounting edge (LPBF forming) and an upper simple wall (LDED forming).

[0042] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] The equipment and testing methods used in the following embodiments of the present invention are as follows: LPBF forming equipment: EOS M100 industrial-grade metal 3D printer with a maximum laser power of 200W, a spot diameter of approximately 40μm, controllable oxygen content in the forming chamber ≤0.1%, and substrate preheating temperature of 200℃.

[0044] LDED Composite Processing Equipment: This system adopts a laser composite additive manufacturing system, which integrates a 6-axis robot, a 4kW fiber laser, a coaxial powder feeding head, a dual-bin gradient powder feeder, a non-contact ultrasonic sound generator (frequency adjustable from 20 to 100 kHz, maximum sound pressure 10 MPa), a laser shock enhancement unit (Nd:YAG laser, wavelength 1064nm, pulse energy adjustable from 0.5 to 20 J), and an online infrared temperature measurement module.

[0045] Powder materials: High-temperature alloy (GH4099) spherical powder, with a particle size distribution of 45~105μm (suitable for LDED) and 15~53μm (suitable for LPBF), purchased from AVIC MITEK. Y2O3 nanoparticles, purity 99.9%, average particle size 50nm, purchased from Aladdin Reagents.

[0046] Microstructure characterization: The metallographic structure was observed using an Olympus GX53 optical microscope. After mechanical grinding and polishing, the grain boundaries were exposed by chemical etching (anhydrous copper sulfate + anhydrous ethanol + hydrochloric acid).

[0047] Mechanical property testing: Room temperature tensile tests were conducted on an Instron 5982 universal testing machine according to GB / T 228.1-2010 standard. The gauge length of the specimens was taken from the LDED region and the interfacial region of the component, and the tensile rate was 1 mm / min. No less than 3 specimens were tested under each condition, and the average value was taken.

[0048] Example 1 This embodiment aims to prepare a GH4099 alloy simulation part that includes a complex lower mounting edge (LPBF forming) and a simple upper wall (LDED forming); Step 1: LPBF forming of precision base portion LPBF (Liquid Crystallization) was formed using GH4099 alloy spherical powder (particle size 15~53μm) under an argon-protected atmosphere (oxygen content ≤0.02%). The process parameters were: laser power 120W, scanning speed 1100 mm / s, scanning spacing 0.06 mm, and layer thickness 0.02 mm. A base with a complex mounting edge structure and a forming height of 30 mm was used as the first forming area. Testing showed that the LPBF region had a density >99.5%.

[0049] Step 2: LDED forming and composite auxiliary processes The substrate with the LPBF base is transferred to the LDED composite processing area. LDED forming is performed using GH4099 alloy powder (particle size 45~105μm), depositing a cylindrical wall with a height of 80 mm as the second forming area. During the LDED process, the following three composite auxiliary processes are performed simultaneously: (2a) Gradient ODS powder supply: Two composite powders were pre-prepared: powder A (GH4099 powder + 0.1 wt.% Y2O3 nanoparticles) and powder B (GH4099 + 0.4 wt.% Y2O3 nanoparticles). A dual-bucket gradient powder feeding system was used. Powder A was supplied at the beginning of the deposition stage (near the LPBF / LDED interface). Subsequently, within a deposition height of 40 mm, the proportion of powder B was linearly increased to 100% by the control system, while the proportion of powder A was correspondingly reduced to 0, so that the Y2O3 content gradually increased from 0.1 wt.% at the interface to 0.4 wt.% at the top.

[0050] (2b) Ultrasonic Assisted Deposition: The transmitter head of the non-contact ultrasonic generator is mechanically fixed to the LDED deposition head, maintaining a vertical distance of 80 mm between the transmitter end face and the molten pool surface. The ultrasonic frequency is set to 60 kHz, and the sound pressure acting on the molten pool is monitored in real time to be approximately 3~4 MPa.

[0051] (2c) Periodic interlayer laser shock peening: After every 5 layers (approximately 2.0 mm thick) are deposited, LDED deposition is paused. The surface temperature is monitored using an online infrared thermometer. When the temperature drops below 150°C, the laser shock peening unit is activated. The process parameters are: laser pulse energy 10 J, pulse width 15 ns, spot diameter 3 mm, spot overlap rate 60%, and 3 shocks per point. Before shocking, black paint is uniformly sprayed onto the area to be shocked as an absorption layer using an automated coating system, and a stable water curtain is used as a constraint layer. After shocking, the residual absorption layer on the surface is cleaned using a lightweight auxiliary tool.

[0052] The basic process parameters for LDED are: laser power 750W, spot diameter 3 mm, scanning speed 5 mm / s, powder feeding rate 8g / min, and single-layer lifting height 0.65 mm.

[0053] Step 3: Post-heat treatment After the component is formed as a whole, it undergoes solution treatment and aging: heat treatment at 1140℃ for 2 hours, followed by air cooling; then heat treatment at 780℃ for 20 hours, followed by air cooling, to obtain a GH4099 alloy simulation part.

[0054] Analysis and Results: Organizational Analysis: Figure 4 This is the metallographic structure of the LPBF-LDED region prepared using the method of the present invention in this embodiment. Due to the gradient design of Y2O3 content increasing from 0.1 wt.% at the interface to 0.4 wt.% at the top, the LDED region structure exhibits the following characteristics: In the region near the interface (Y2O3 content 0.1 wt.%), due to the low content, the epitaxial growth of columnar crystals is mainly interrupted by ultrasound assistance, forming a mixed structure of fine equiaxed crystals and residual columnar crystals, with an average grain size of about 65 μm, achieving a smooth transition with the fine-grained region of LPBF. In the middle region (Y2O3 content 0.2~0.3 wt.%), as the Y2O3 content increases, the number of heterogeneous nucleation sites increases, and the grains are further refined, with an average grain size of about 55 μm. In the top region (Y2O3 content 0.4 wt.%), the Y2O3 content reaches its highest level, and the dispersion strengthening and grain refinement effects are most significant. Combined with ultrasound assistance, a uniform and fine equiaxed crystal structure is formed, with an average grain size of about 45 μm.

[0055] Overall, the method of this invention causes the grain size of the LDED region to gradually refine with increasing height (65μm at the interface → 55μm in the middle → 45μm at the top), forming a gradient refinement structure that counteracts the thermal accumulation effect. At the same time, twins and high dislocation density regions introduced by laser shock strengthening are visible on the surface.

[0056] Mechanical properties: Results of room temperature tensile tests ( Figure 5 The results show that the composite component prepared using the method of this invention achieves an overall tensile strength of 824 MPa, an elongation after fracture of 30.18%, and an overall yield strength of 608 MPa. The overall plasticity of the component is approximately 163% higher than that of a directly deposited component without any composite auxiliary treatment (Comparative Example 1, the LPBF-LDED component has an elongation after fracture of only 11.48%). Simultaneously, the tensile strength is increased by approximately 10%, and the yield strength by approximately 12.3%.

[0057] Example 2 This embodiment aims to investigate the effect of the number N of periodic interlayer laser shock strengthening intervals on the microstructure and properties of components, in order to optimize the process window.

[0058] Except for the number of spacer layers N in step 2c for laser shock strengthening, all other process parameters are exactly the same as in Example 1. Three sets of experiments were set up: Group A: N=3 (LSP is performed once every 3 layers); Group B: N=5 (same as Example 1); Group C: N=8 (LSP is performed once every 8 layers).

[0059] After each group of components was completed, post-treatment was carried out using the same heat treatment regime as in Example 1, and the microstructure and room temperature tensile properties of the LDED region were characterized.

[0060] Results and Analysis: Group B (N=5) exhibits the best overall performance: significant grain refinement, gentle microstructure gradient, and optimal strength-plasticity balance. Group A (N=3), due to excessively frequent processing, slightly affected deposition efficiency, and there was slight overlap in the heat-affected zone; its improvement in plasticity was comparable to Group B. Group C (N=8), due to excessively large interlayer spacing, failed to promptly suppress microstructure coarsening caused by localized heat accumulation; its grain size was slightly larger than Group B, resulting in a relatively low improvement in plasticity. The results indicate that a N range of 4–6 layers represents the optimal process window.

[0061] Example 3: This embodiment aims to verify the effectiveness of the method of the present invention under mid-frequency ultrasound and moderate gradient changes in ODS content.

[0062] Step 1: LPBF forming Same as Example 1.

[0063] Step 2: LDED forming and composite auxiliary processes Basic LDED parameters: laser power 800W, spot diameter 3 mm, scanning speed 6 mm / s, powder feed rate 10 g / min, single-layer lifting height 0.68 mm.

[0064] (2a) Gradient ODS powder supply: The content of Y2O3 nanoparticles gradually increases from 0.08 wt.% at the interface to 0.35 wt.% at the top, and the gradient change is completed within a 50 mm deposition height.

[0065] (2b) Ultrasonic assisted deposition: The ultrasonic frequency was set to 45 kHz, the vertical distance between the transmitter and the surface of the molten pool was 100 mm, and the sound pressure acting on the molten pool was stabilized at 2~3 MPa.

[0066] (2c) Periodic interlayer laser shock peening: LSP treatment is performed every 6 layers (N=6). The LSP process parameters are: laser pulse energy 8 J, pulse width 18 ns, spot diameter 3.5 mm, spot overlap rate 55%, and 4 shocks per point. The shock is started when the deposited surface cools to below 180°C.

[0067] Step 3: Post-heat treatment After the component is formed as a whole, it is solution treated at 1160℃ for 3 hours and then air-cooled; it is then aged at 800℃ for 20 hours and then air-cooled.

[0068] Analysis and Results: Microstructure analysis: The LDED region of the component has a uniform microstructure, with the grain size decreasing from about 70 μm at the interface to about 50 μm at the top, forming a gradient refinement microstructure that counteracts the thermal accumulation effect.

[0069] Mechanical properties: Room temperature tensile tests showed an overall tensile strength of 815 MPa, an elongation after fracture of 28.5%, and a yield strength of 595 MPa. The overall plasticity was improved by approximately 148% compared to Comparative Example 1, demonstrating that excellent synergistic refining effects can still be achieved under medium-frequency ultrasound and medium gradient content.

[0070] Example 4: This embodiment aims to explore the effects of combining high-frequency ultrasound, high-content ODS gradient, and more frequent interlaminar shocks.

[0071] Step 1: LPBF forming Same as Example 1.

[0072] Step 2: LDED forming and composite auxiliary processes Basic LDED parameters: laser power 700W, spot diameter 3 mm, scanning speed 4 mm / s, powder feed rate 7 g / min, single-layer lifting height 0.68 mm.

[0073] (2a) Gradient ODS powder supply: The content of Y2O3 nanoparticles gradually increases from 0.12 wt.% at the interface to 0.48 wt.% at the top.

[0074] (2b) Ultrasonic assisted deposition: The ultrasonic frequency is set to 80 kHz, the vertical distance between the transmitter and the surface of the molten pool is 70 mm, and the sound pressure acting on the molten pool is increased to 5~6 MPa.

[0075] (2c) Periodic interlayer laser shock peening: LSP treatment is performed once every 4 layers (N=4). The LSP process parameters are: laser pulse energy 12 J, pulse width 12 ns, spot diameter 2.5 mm, spot overlap rate 65%, and 5 shocks per point. The shock is started when the deposited surface cools to below 120°C.

[0076] Step 3: Post-heat treatment After the component is formed as a whole, it is solution treated at 1150℃ for 1.5 hours and then oil quenched; it is then aged at 770℃ for 24 hours and then air cooled.

[0077] Analysis and Results: Microstructure analysis: High-frequency ultrasound combined with high sound pressure resulted in stronger cavitation and acoustic flow effects in the molten pool, leading to a significant grain refinement effect. Combined with the high content of Y2O3 nanoparticles and the recrystallization driving force introduced by high-frequency LSP, an extremely fine equiaxed grain structure with an average grain size of only about 40 μm was formed at the top of the LDED region, resulting in a significant gradient refinement structure.

[0078] Mechanical properties: Room temperature tensile tests showed an overall tensile strength of up to 840 MPa, an elongation after fracture of 32.1%, and a yield strength of 620 MPa. The overall plasticity was improved by approximately 180% compared to Comparative Example 1, achieving an excellent performance match.

[0079] Example 5: This embodiment aims to verify the effectiveness of the method of the present invention under low-frequency ultrasound and low ODS gradient content.

[0080] Step 1: LPBF forming Same as Example 1.

[0081] Step 2: LDED forming and composite auxiliary processes Basic LDED parameters: laser power 750W, spot diameter 3 mm, scanning speed 5 mm / s, powder feed rate 8 g / min, single-layer lifting height 0.68 mm.

[0082] (2a) Gradient ODS powder supply: The content of Y2O3 nanoparticles increases from 0.06 wt.% at the interface to 0.32 wt.% at the top, and the gradient change is completed within a 60 mm deposition height.

[0083] (2b) Ultrasonic assisted deposition: The ultrasonic frequency was set to 25 kHz, the vertical distance between the transmitter head and the surface of the molten pool was 120 mm, and the sound pressure acting on the molten pool was stabilized at 1~2 MPa.

[0084] (2c) Periodic interlayer laser shock peening: LSP treatment is performed every 3 layers (N=3). The LSP process parameters are: laser pulse energy 6 J, pulse width 18 ns, spot diameter 3 mm, spot overlap rate 50%, and 3 shocks per point. The shock is started when the deposited surface cools to below 150°C.

[0085] Step 3: Post-heat treatment After the component is formed as a whole, it is solution treated at 1150℃ for 2.5 hours and then air-cooled; it is then aged at 780℃ for 20 hours and then air-cooled.

[0086] Analysis and Results: Microstructure analysis: The LDED region of the component has a relatively uniform microstructure, with the grain size decreasing gradually from about 75 μm at the interface to about 60 μm at the top. Low-frequency ultrasound can still effectively interrupt the epitaxial growth of columnar crystals, and combined with the low ODS gradient, it forms a relatively gentle gradient refinement microstructure.

[0087] Mechanical properties: Room temperature tensile tests showed an overall tensile strength of 805 MPa, an elongation after fracture of 26.8%, and a yield strength of 585 MPa. The overall plasticity was improved by approximately 133% compared to Comparative Example 1, demonstrating that the method of this invention can still achieve a significant synergistic refining effect under low-frequency ultrasound and low gradient content.

[0088] This embodiment uses N=3, which is lower than the preferred range (4~6 layers), but it still achieves a significant refinement effect, proving the effectiveness of the method of the present invention within a wider process window.

[0089] Example 6: This embodiment aims to verify the effectiveness of the method of the present invention under medium- and high-frequency ultrasound and medium- and high ODS gradient content.

[0090] Step 1: LPBF forming Same as Example 1.

[0091] Step 2: LDED forming and composite auxiliary processes Basic LDED parameters: laser power 780W, spot diameter 3 mm, scanning speed 5.5 mm / s, powder feed rate 9 g / min, single-layer lifting height 0.68 mm.

[0092] (2a) Gradient ODS powder supply: The content of Y2O3 nanoparticles increases from 0.10 wt.% at the interface to 0.45 wt.% at the top, and the gradient change is completed within a deposition height of 55 mm.

[0093] (2b) Ultrasonic assisted deposition: The ultrasonic frequency was set to 70 kHz, the vertical distance between the transmitter and the surface of the molten pool was 80 mm, and the sound pressure acting on the molten pool was stabilized at 4~5 MPa.

[0094] (2c) Periodic interlayer laser shock peening: LSP treatment is performed every 5 layers (N=5). The LSP process parameters are: laser pulse energy 10 J, pulse width 15 ns, spot diameter 3 mm, spot overlap rate 60%, and 4 shocks per point. The shock is started when the deposited surface cools to below 150°C.

[0095] Step 3: Post-heat treatment After the component is formed as a whole, it is solution treated at 1160℃ for 2 hours and then air-cooled; it is then aged at 790℃ for 18 hours and then air-cooled.

[0096] Analysis and Results: Microstructure analysis: The combination of medium- and high-frequency ultrasound and medium- to high-content Y2O3 nanoparticles resulted in strong cavitation and acoustic flow effects in the molten pool, leading to significant grain refinement. The LDED region exhibited a uniform microstructure, with grain size decreasing gradually from approximately 60 μm at the interface to approximately 45 μm at the top, forming a well-refined gradient microstructure.

[0097] Mechanical properties: Room temperature tensile tests showed an overall tensile strength of up to 830 MPa, an elongation after fracture of 31.2%, and a yield strength of 615 MPa. The overall plasticity was improved by approximately 172% compared to Comparative Example 1, achieving excellent performance matching.

[0098] Comparative Example 1: LPBF-LDED Composite Deposition without Composite Auxiliary Processes Similar to Example 1, the difference is that no composite auxiliary process is performed in step 2, i.e., there is no gradient ODS powder supply, no ultrasonic assistance, and no interlayer LSP. Only the same LDED basic process parameters are used to deposit an 80 mm high cylindrical wall on the LPBF substrate. The post-heat treatment regime is the same as in Example 1.

[0099] In this comparative example, the LDED region formed a coarse columnar crystal structure that spanned several layers (see...). Figure 3 The grain size increases sharply from bottom to top, with an average grain size of approximately 120 μm near the interface and exceeding 250 μm in the top region. Room temperature tensile testing showed an overall tensile strength of 750 MPa and an elongation after fracture of 11.48%, indicating poor overall plasticity matching of the component. Microcrack initiation was observed during deposition. These results verify the necessity of the composite auxiliary process described in this invention for improving the microstructure and properties of the LDED zone.

[0100] Comparative Example 2: Gradient-free ODS design (using uniform ODS content) Same as Example 1, except that in step 2a, instead of using gradient ODS powder supply, a uniform composite powder with a Y2O3 content of 0.25 wt.% is used for LDED deposition throughout the process. The remaining processes (ultrasound, LSP) and post-heat treatment are the same as in Example 1.

[0101] In this comparative example, although the LDED region achieved some grain refinement due to ultrasound and LSP, the uniform Y2O3 content of 0.25 wt.% was used throughout the process, resulting in a relatively high content (0.25 wt.%) at the interface. This, combined with a faster cooling rate at the interface deposition, led to a more abrupt change in microstructure near the LPBF / LDED interface, forming a distinct interface transition zone. In the top region, the content failed to increase synchronously with the thermal accumulation effect (0.4 wt.% at the top in Example 1), resulting in insufficient grain refinement and a slightly larger grain size than in Example 1, with a still relatively abrupt microstructure gradient. Room temperature tensile testing showed an overall elongation at break of 9.21%, lower than 30.18% in Example 1 and also lower than 11.48% in Comparative Example 1. The plasticity across the interface region was slightly lower than in Example 1, indicating that gradient ODS design plays an important role in smoothing out the abrupt changes in interfacial microstructure.

[0102] Comparative Example 3: Deposition without Ultrasonic Assistance Same as Example 1, except that the ultrasonic-assisted generator is not activated in step 2b. The remaining processes (gradient ODS, LSP) and post-heat treatment are the same as in Example 1.

[0103] In this comparative example, the grain refinement effect in the LDED region mainly relies on the heterogeneous nucleation sites provided by the gradient ODS and the recrystallization driving force introduced by the LSP. However, due to the lack of direct ultrasonic intervention in the solidification process of the molten pool, the columnar epitaxial growth was not sufficiently interrupted, resulting in an overall grain size slightly larger than that of Example 1 (average grain size of approximately 95 μm) and slightly poorer microstructure uniformity. Room temperature tensile testing showed an overall tensile strength of 802 MPa and an elongation after fracture of 10.62%, lower than the 30.18% of Example 1, indicating that ultrasonic assistance plays an irreplaceable role in achieving in-situ microstructure refinement and improving intrinsic plasticity.

[0104] Comparative Example 4: LSP without interlayer processing Same as Example 1, except that periodic interlayer laser shock peening is not performed in step 2c. The remaining processes (gradient ODS, ultrasonication) and post-heat treatment are the same as in Example 1.

[0105] In this comparative example, the LDED region accumulated high residual tensile stress due to the lack of stress control during deposition, and a small number of microcracks were observed after deposition. Although subsequent heat treatment could partially relieve the stress, the microcracks that had already formed could not heal, leading to a decrease in the overall mechanical properties of the component. Room temperature tensile testing showed that the tensile strength of the LDED region was 750 MPa, and the elongation after fracture was only 12.5%, with most of the fracture originating at the microcracks. These results confirm the crucial role of interlaminar LSP in suppressing cracking and improving forming reliability.

[0106] Comparative Example 5: Single process combination (no gradient ODS + no ultrasonic + with LSP) This comparative example aims to compare whether the effects of the present invention can be achieved when there is a lack of component gradient design and ultrasound assistance, and only interlayer LSP is relied upon.

[0107] Step 1: LPBF forming Same as Example 1.

[0108] Step 2: LDED forming and composite auxiliary processes Basic LDED parameters: same as in Example 3 (laser power 800W, spot diameter 3 mm, scanning speed 6 mm / s, powder feed rate 10 g / min, single-layer lifting height 0.68 mm).

[0109] (2a) Gradient ODS powder supply: No Y2O3 nanoparticles are added, only pure GH4099 powder is used.

[0110] (2b) Ultrasonic-assisted deposition: The ultrasonic-assisted device is not turned on.

[0111] (2c) Periodic interlayer laser shock peening: LSP treatment is performed every 5 layers. The LSP process parameters are the same as in Example 1 (laser pulse energy 10 J, pulse width 15 ns, spot diameter 3 mm, spot overlap rate 60%, 3 shocks per point). The shock is started when the deposited surface cools to below 150°C.

[0112] Step 3: Post-heat treatment Same as Example 3 (solution treatment at 1160℃ for 3 hours, followed by air cooling; aging treatment at 800℃ for 20 hours, followed by air cooling).

[0113] Analysis and Results: Microstructural analysis: Metallographic observation shows that the LDED zone is still dominated by coarse columnar crystals, with the grain size increasing from about 110 μm at the interface to about 200 μm at the top. LSP only introduces a refinement layer and residual compressive stress about 300-500 μm deep on the surface, but has limited improvement on the coarse solidification structure inside.

[0114] Mechanical properties: Room temperature tensile testing showed an overall tensile strength of 780 MPa and an elongation at break of only 13.5%. Although this is a slight improvement compared to Comparative Example 1 (11.48%), it is far lower than the levels of Examples 1-6 (26.8%~32.1%). This indicates that LSP post-treatment alone cannot fundamentally solve the problems of coarse tissue and uneven properties in the LDED region. It must be combined with gradient ODS and ultrasound assistance to achieve full-chain regulation of tissue properties from the solidification process to the solid-state phase transition.

[0115] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a GH4099 alloy component, characterized in that, Includes the following steps: (1) Using GH4099 alloy powder, the first forming area of ​​the alloy component is prepared on the substrate by laser powder bed melting process under an inert atmosphere; (2) GH4099 alloy composite powder is used on the first forming area and deposited layer by layer by laser directional energy deposition process to prepare the second forming area of ​​the alloy component, thereby obtaining the formed alloy component; (3) The formed alloy components are subjected to solution treatment and aging treatment to obtain GH4099 alloy components; In step (2), the GH4099 alloy composite powder is composed of GH4099 alloy powder and yttrium oxide, wherein the mass fraction of yttrium oxide in the GH4099 alloy composite powder varies in a predetermined gradient along the deposition height direction; In step (2), while the laser-directed energy deposition process is being carried out, the deposited molten pool is subjected to non-contact ultrasonic treatment. In step (2), when the laser directional energy deposition process is performed, after each preset N layers are deposited, the deposition process is paused, and the top surface that has been deposited is subjected to full-coverage laser shock treatment, where N is 3~8 and N is an integer.

2. The preparation method according to claim 1, characterized in that, The mass fraction gradient of yttrium oxide was designed as follows: the yttrium oxide content in the initial deposition layer of the second forming region was 0.05~0.15 wt.%, which gradually increased with the deposition height until the yttrium oxide content in the top deposition layer was 0.3~0.5 wt.%.

3. The preparation method according to claim 1, characterized in that, The process parameters for the non-contact ultrasonic treatment are as follows: the ultrasonic frequency is 20~100kHz, the vertical distance between the end face of the ultrasonic transmitter and the surface of the molten pool is 50~150 mm, and the sound pressure applied to the molten pool is 0.5~10 MPa.

4. The preparation method according to claim 1, characterized in that, The process parameters for the full-coverage laser shock treatment are as follows: laser pulse energy of 5~15J, pulse width of 10~20ns, spot diameter of 2~4mm, spot overlap rate of 50~70%, and 1~5 impacts per point.

5. The preparation method according to claim 1, characterized in that, Before performing full-coverage laser shock treatment, the temperature of the surface to be impacted must be kept below 200℃.

6. The preparation method according to claim 1, characterized in that, The solution treatment temperature is 1140~1180℃, and the time is 1~4h. After the solution treatment is completed, air cooling or oil quenching is performed.

7. The preparation method according to claim 1, characterized in that, The aging treatment is carried out at a temperature of 760~820℃ for 16~24h, followed by air cooling.

8. GH4099 alloy components prepared by the preparation method according to any one of claims 1 to 7.

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