Additive manufacturing high-volume-fraction gamma'phase nickel-based superalloy and heat treatment method thereof

Abstract

The invention discloses an additive manufacturing high-volume-fraction gamma'phase nickel-based superalloy and a heat treatment method thereof.The heat treatment method comprises the steps that the additive manufacturing nickel-based superalloy is placed at the temperature of 750-800 DEG C, stress relief annealing treatment, solution treatment, hot isostatic pressing treatment and aging treatment are conducted, and the additive manufacturing nickel-based superalloy subjected to heat treatment is obtained; the additive manufacturing nickel-based superalloy comprises the following chemical components of, by weight, 15.0% to 20.0% of Cr, 7.0% to 10.0% of Co, 2.0% to 3.0% of W, 1.0% to 2.5% of Mo, 3.0% to 3.5% of Al, 3.0% to 3.5% of Ti, 1.0% to 2.0% of Ta, 0.01% to 0.1% of C, 0.001% to 0.005% of B, 0.001% to 0.01% of Zr, 0.5% to 1.5% of Nb and the balance Ni. Through multi-stage heat treatment, on one hand, internal stress caused by rapid cooling of additive manufacturing is eliminated through stress relief annealing treatment and hot isostatic pressing treatment, and on the other hand, the structure is more uniform through solution treatment and heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing 3D printing technology, specifically relating to an additive manufacturing method for high volume fraction γ' phase nickel-based high-temperature alloys and its heat treatment method. Background Technology

[0002] Nickel-based superalloys, with their excellent high-temperature strength, creep resistance, and resistance to high-temperature oxidation and hot corrosion, have become the preferred material for core hot-end components in aerospace, energy, and power industries (such as turbine blades in aero-engines, combustion chambers in gas turbines, and heat transfer tubes in nuclear power reactors). These components operate in harsh environments, requiring long-term exposure to temperatures of 600-1000℃, complex alternating loads, and corrosive media, placing extremely high demands on the material's microstructure uniformity, mechanical stability, and reliability. Traditional nickel-based superalloy components are primarily manufactured using forging and casting processes; however, these traditional methods have significant limitations in meeting the demands of modern equipment for lightweight and complex structures.

[0003] The rise of additive manufacturing (AM) technologies (such as Selective Laser Melting (SLM) and Electron Beam Powder Bed Fusion (EB-PBF)) has provided a breakthrough solution for the fabrication of complex nickel-based superalloy components. This technology, through the principle of "layer-by-layer deposition," can directly shape metal powder into near-net-shape complex structures, increasing material utilization to over 80%. Simultaneously, it allows for flexible control of the local composition and microstructure of components, laying the foundation for the manufacturing of high-performance, customized hot-end components. The core strengthening mechanism of nickel-based superalloys relies on the uniform and dispersed distribution of coherent precipitates such as the γ' phase (Ni3Al / Ti) and the γ'' phase (Ni3Nb). Although both the γ' phase and the γ matrix are FCC structures, there is a 1%-2% difference in lattice constant (e.g., the lattice constant of Ni3Al is about 3.57 Å, while that of the γ-Ni matrix is ​​about 3.52 Å). This mismatch creates a spherically symmetric elastic strain field around the γ' phase. At room temperature, for dislocations in the matrix to cross the γ' phase, they must overcome the additional stress generated by the strain field. For edge dislocations, the strain field generates a force perpendicular to the slip plane; for screw dislocations, it induces additional torsional resistance. This strengthening effect is significantly enhanced with the increase of the γ' phase volume fraction. At high temperatures, dislocations readily bypass fine precipitates via "climb" (i.e., atomic diffusion causing dislocations to move along the direction perpendicular to the slip plane). A high volume fraction of the γ' phase can reduce the "channel" for dislocation climb through steric hindrance. When the γ' phase is uniformly dispersed and has a sufficiently high volume fraction, the matrix channel width between adjacent γ' phases decreases, increasing the atomic diffusion distance required for dislocation climb and thus suppressing the climb rate. Simultaneously, γ' phase precipitates at grain boundaries can "pin" the grain boundaries, reducing creep deformation caused by grain boundary slip at high temperatures and further enhancing the alloy's creep resistance. In summary, for nickel-based superalloys, the volume fraction of the γ' phase dominates the alloy's room temperature and high-temperature mechanical properties.

[0004] Currently, although some heat treatment methods for additively manufactured nickel-based superalloys have been reported, most are for alloys with low γ' phase content, such as IN718, GH3536, and GH4169. These alloys have low contents of alloying elements such as Al, Ti, Ta, and Nb, fewer types of precipitated phases, and relatively simple heat treatment steps. These methods are not entirely suitable for additively manufactured nickel-based superalloys with high γ' phase volume fractions. Therefore, developing a dedicated heat treatment method that can specifically eliminate residual stress, control grain size, and achieve uniform and dispersed precipitation of strengthening phases in additively manufactured nickel-based superalloys with high γ' phase volume fractions has become a key technological bottleneck for promoting the large-scale application of additively manufactured nickel-based superalloys. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide an additive manufacturing method for high volume fraction γ' phase nickel-based superalloys and its heat treatment method.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a heat treatment method for additive manufacturing of high volume fraction γ' phase nickel-based superalloys, comprising, Additive-manufactured nickel-based superalloys are subjected to stress-relief annealing, solution treatment, hot isostatic pressing, and aging treatment at 750-800℃ to obtain heat-treated additive-manufactured nickel-based superalloys. The additively manufactured nickel-based superalloy comprises the following chemical composition: Cr: 15.0-20.0 wt%, Co: 7.0-10.0 wt%, W: 2.0-3.0 wt%, Mo: 1.0-2.5 wt%, Al: 3.0-3.5 wt%, Ti: 3.0-3.5 wt%, Ta: 1.0-2.0 wt%, C: 0.01-0.1 wt%, B: 0.001-0.005 wt%, Zr: 0.001-0.01 wt%, Nb: 0.5-1.5 wt%, with the balance being Ni.

[0009] As a preferred embodiment of the heat treatment method described in this invention, the stress-relief annealing process involves heating the heat treatment furnace to 750-800°C, placing the additively manufactured nickel-based superalloy into the heat treatment furnace for stress-relief annealing, and holding the heat for 4-6 hours; finally, the alloy is removed and air-cooled.

[0010] As a preferred embodiment of the heat treatment method described in this invention, the solution treatment involves placing the stress-relieved annealed additive-manufactured nickel-based superalloy at a temperature of 1100-150°C for solution treatment, followed by air cooling.

[0011] As a preferred embodiment of the heat treatment method described in this invention, the hot isostatic pressing (HIP) process involves placing the solution-treated additive-manufactured nickel-based superalloy at a temperature of 1100-1120°C and a constant pressure of 180 MPa for HIP treatment, followed by furnace cooling.

[0012] As a preferred embodiment of the heat treatment method of the present invention, the aging treatment involves placing the additively manufactured nickel-based superalloy after hot isostatic pressing at a temperature of 800°C for aging treatment; followed by air cooling at room temperature.

[0013] As a preferred embodiment of the heat treatment method described in this invention, the additively manufactured nickel-based superalloy comprises the following chemical composition: Cr: 15.72 wt%, Co: 8.73 wt%, W: 2.37 wt%, Mo: 1.52 wt%, Al: 3.23 wt%, Ti: 2.94 wt%, Ta: 1.45 wt%, C: 0.05 wt%, B: 0.002 wt%, Zr: 0.002 wt%, Nb: 1.02 wt%, with the balance being Ni.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide an additive manufacturing high volume fraction γ' phase nickel-based superalloy obtained by a heat treatment method.

[0015] As a preferred embodiment of the additive manufacturing of high volume fraction γ' phase nickel-based superalloys according to the present invention, wherein: the microstructure of the additively manufactured high volume fraction γ' phase nickel-based superalloy is completely free of cracks, and the γ' phase is spherical.

[0016] As a preferred embodiment of the additive manufacturing of high volume fraction γ' phase nickel-based superalloys according to the present invention, wherein: the average size of the additively manufactured high volume fraction γ' phase nickel-based superalloy is 300nm-600nm, the volume fraction is >60vol%, and the average grain size is 50-120μm.

[0017] As a preferred embodiment of the additive manufacturing of high volume fraction γ' phase nickel-based superalloys according to the present invention, wherein: at room temperature, σb≥1300MPa, σ0.2≥1000MPa, A≥10%; at 650℃±5℃, σb≥1000MPa, σ0.2≥800MPa, A≥10%; and at 760℃±5℃ and constant stress of 585MPa±5MPa, the duration is ≥20h.

[0018] Beneficial effects of this invention: (1) The stress-relief annealing temperature of this invention is designed to be 750-800℃, which is lower than the stress-relief annealing temperature of common additive manufacturing nickel-based superalloys. By holding the temperature for a longer time, the stress is prevented from being released rapidly under external heat, which could lead to cracking of the sample. On the other hand, the fine-grained structure generated by rapid solidification in additive manufacturing can be preserved. Unlike other common heat treatment methods for nickel-based superalloys that first undergo hot isostatic pressing and then solution treatment, this invention, based on stress-relief annealing, first eliminates element segregation and micro-lattice distortion at grain boundaries through solution treatment, redistributes grain boundary elements, and reduces the risk of cracking in subsequent heat treatment. After solution treatment, combined with hot isostatic pressing, the additive manufacturing nickel-based superalloy is free of microcracks, has lower porosity, and to a certain extent, homogenizes the microstructure. Through aging treatment, the volume fraction of the γ′ phase in the additive manufacturing nickel-based superalloy is increased, a dispersed and appropriately sized γ′ phase is obtained, and cracking and recrystallization caused by residual stress are eliminated, thereby improving the high-temperature mechanical properties of the additive manufacturing nickel-based superalloy.

[0019] (2) This invention employs multi-stage heat treatment. On the one hand, stress-relief annealing and hot isostatic pressing eliminate internal stress caused by rapid cooling in additive manufacturing, thereby eliminating cracks and pores in the matrix and providing a foundation for subsequent heat treatment. On the other hand, solution treatment and heat treatment make the microstructure more uniform, eliminate elemental segregation, increase the volume fraction of the γ′ phase in the additive-manufactured nickel-based superalloy, coarsen the grain size, and improve the mechanical properties at room temperature, thus achieving the goal of optimizing alloy performance. The heat treatment process of this invention is applicable to additive-manufactured nickel-based superalloy samples using selective laser melting and has a certain degree of universality. Moreover, the heat treatment method does not require special environments such as vacuum or argon, thus possessing the characteristics of simplicity, low cost, and high efficiency, making it an effective way to optimize additive-manufactured nickel-based superalloys. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of 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. Wherein: Figure 1 SEM images of the nickel-based alloy powder raw materials used in the embodiments and comparative examples of this invention; Figure 2 This is a SEM microstructure image of the printed nickel-based superalloy in an embodiment of the present invention. Figure 3 This is a macroscopic view of the heat-treated nickel-based superalloy in Example 1 of the present invention; Figure 4 This is a SEM microstructure image of the heat-treated nickel-based superalloy in Example 1 of the present invention; Figure 5 This is a TEM microstructure image of the heat-treated nickel-based superalloy in Example 1 of the present invention; Figure 6 The room temperature tensile properties of the nickel-based superalloy in the printed state in Example 1 of this invention; Figure 7 The room temperature tensile properties of the heat-treated nickel-based superalloy in Example 1 of this invention; Figure 8 This is a SEM microstructure image of the heat-treated nickel-based superalloy in Comparative Example 1 of the present invention. Figure 9 This is a macroscopic image of the heat-treated nickel-based superalloy in Comparative Example 2 of the present invention; Figure 10 This is a microstructure of the heat-treated nickel-based superalloy γ' in Comparative Example 2 of the present invention. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available. The term "printed state" refers to a sample that has not undergone heat treatment.

[0025] Example 1 This embodiment prepares an additively manufactured nickel-based superalloy: (1) The additively manufactured nickel-based superalloy comprises the following chemical composition by weight percentage: Cr: 15.72 wt%, Co: 8.73 wt%, W: 2.37 wt%, Mo: 1.52 wt%, Al: 3.23 wt%, Ti: 2.94 wt%, Ta: 1.45 wt%, C: 0.05 wt%, B: 0.002 wt%, Zr: 0.002 wt%, Nb: 1.02 wt%, balance Ni.

[0026] (2) All raw materials were mixed and nickel-based superalloy powder was prepared by argon atomization system. The crucible was a zirconia crucible, the melting power was 65kW, the holding time was 25min, and the gas pressure was 3.5 MPa. The nickel-based alloy powder with a particle size of 15-53μm was screened by vibrating sieving equipment for laser additive manufacturing. The layer thickness was controlled at 30μm, the scanning interval was 90μm, the laser power was 180W, the scanning rate was 800mm / s, the interlayer rotation angle was 90°, and an orthogonal scanning strategy was adopted. The protective gas was argon. The formed sample was a rectangular prism sample with a size of 20mm×20mm×70mm. Then, the additively manufactured nickel-based superalloy sample was heat-treated and its performance was tested according to the following steps: (3) Stress-relief annealing: The heat treatment furnace (box muffle furnace) is heated to 750°C, and the additive manufacturing nickel-based superalloy to be treated (along with the substrate) is placed in the furnace for stress-relief annealing. The holding time is 4 hours. Then it is taken out and air-cooled to room temperature to obtain the additive manufacturing nickel-based superalloy sample after stress-relief annealing. The sample is separated from the substrate by wire EDM.

[0027] (4) Solution treatment: The printed part after stress relief annealing is subjected to solution treatment to obtain a solution-treated printed part. Specifically, the printed part after hot isostatic pressing is heated to 1120°C and subjected to solution treatment for 2 hours, and then taken out and air-cooled to room temperature to obtain a solution-treated printed part; wherein the heating rate is 10°C / min.

[0028] (5) Hot Isostatic Pressing (HIP): The printed parts after solution treatment are subjected to hot isostatic pressing (HIP) to obtain the printed parts after HIP treatment. The parameters of the HIP treatment are as follows: the temperature of the HIP treatment is 1120℃ and the pressure of the HIP treatment is 180MPa; the printed parts are kept at the temperature and pressure of the HIP treatment for 2 hours and then cooled in the furnace to obtain the printed parts after HIP treatment; the heating rate of the printed parts to the temperature of the HIP treatment is 30℃ / min.

[0029] (6) Aging treatment: The hot isostatic pressing (HIP) printed part is subjected to aging treatment to obtain additive manufacturing nickel-based high-temperature alloy. The hot isostatic pressing (HIP) printed part is heated to 800°C and aged for 12 hours. Then it is taken out and air-cooled to room temperature to obtain the aged printed part. The heating rate is 10°C / min.

[0030] (7) The additive manufacturing nickel-based high-temperature alloy sample after heat treatment is sliced ​​and sent to a scanning electron microscope for observation. The microstructure reaches the expected effect, and the heat treatment is over.

[0031] (8) The additively manufactured nickel-based superalloy sample after complete heat treatment is processed into tensile and creep samples to complete the mechanical property test.

[0032] Figure 1 Scanning electron microscope images of nickel-based superalloy powders used for additive manufacturing show that the powder has good sphericity, contains a small amount of satellite powder, and the particle size distribution meets the raw material requirements of selective laser melting additive manufacturing.

[0033] Figure 2 Scanning electron microscope (SEM) images of the embodied additively manufactured nickel-based superalloy show numerous unfused pores and a small number of microcracks in the matrix. These defects significantly affect the alloy's high-temperature mechanical properties. Furthermore, the matrix also exhibits characteristic molten pool structures unique to the additive manufacturing process. These microcracks and pores mostly appear at the boundaries of the molten pool, specifically at the junctions of columnar and equiaxed crystals.

[0034] Figure 3 The image shows the macroscopic appearance of the nickel-based superalloy after complete heat treatment in this embodiment. It can be seen that the sample surface is dense and there is no obvious oxidation or peeling. The sample did not crack after being treated with the heat treatment regime of this embodiment.

[0035] Figure 4 The images shown are scanning electron microscope images of the additively manufactured nickel-based superalloys prepared in this embodiment, for comparison. Figure 2 It can be seen that, compared to the printed state, the alloy achieved full densification after complete heat treatment, with porosity and microcracks completely disappearing. Furthermore, the fully heat-treated microstructure exhibited a high volume fraction of spherical, uniformly sized γ' phase. At lower aging temperatures, the precipitation of carbides and borides was suppressed to some extent, ensuring the alloy's high-temperature mechanical properties.

[0036] Figure 5The transmission electron microscope (TEM) image of the additively manufactured nickel-based superalloy prepared in this embodiment shows that after complete heat treatment, a high volume fraction of γ' phase was formed in the matrix. The γ' phase is a mixture of spherical and cubic shapes. The volume fraction of the γ' phase in the microstructure of the additively manufactured nickel-based superalloy is >60%, and the size of the γ' phase is 300-600 nm.

[0037] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloys prepared in this embodiment in the printed and heat-treated states are shown in Table 1. Figure 6 and Figure 7 The room temperature mechanical properties of the alloys obtained in the printed state and the process of Example 1 are shown respectively.

[0038] Table 1

[0039] As shown in Table 1, the room temperature yield strength and tensile strength of the alloy treated by the heat treatment process in this embodiment are improved, while the plasticity is slightly reduced. The 650℃ mid-temperature yield strength and tensile strength of the alloy treated by the heat treatment process are both improved, and the plasticity of the alloy is significantly enhanced. At 650℃, the yield strength of the alloy reaches 928 MPa, a significant improvement compared to 840 MPa in the printed state, achieving further optimization of mid-to-high temperature performance and demonstrating the alloy's potential superior properties. Furthermore, the creep rupture life at 760℃ / 585 MPa is also improved from almost no life in the printed state to 21.5 hours in the heat-treated state. In summary, the heat treatment process in this embodiment achieves optimization of the alloy's microstructure and properties, resulting in a significant performance breakthrough.

[0040] Example 2 The difference from Example 1 is that in step (6), the printed part after hot isostatic pressing is heated to 700°C, aged for 12 hours, and then taken out and air-cooled to room temperature to obtain the printed part after solution treatment; wherein, the heating rate is 10°C / min, and the rest is the same as in Example 1.

[0041] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloy prepared in this embodiment in the printed and heat-treated states are shown in Table 2.

[0042] Table 2

[0043] As shown in Table 2, the room temperature yield strength and tensile strength of the alloy treated by the heat treatment process in this embodiment are improved, while the plasticity is slightly reduced. The 650℃ mid-temperature yield strength and tensile strength of the alloy treated by the heat treatment process are both improved, and the plasticity of the alloy is significantly enhanced, achieving further optimization of its mid-to-high temperature performance. Furthermore, the crease life at 760℃ / 585MPa is increased from almost zero in the printed state to 19 hours in the heat-treated state. In summary, the heat treatment process in this embodiment achieves optimization of the alloy's microstructure and properties.

[0044] Example 3 The difference from Example 1 is that in step (1), Cr: 19.42wt%, Co: 9.33wt%, W: 1.77wt%, Mo: 2.42wt%, Al: 3.02wt%, Ti: 3.04wt%, Ta: 1.15wt%, C: 0.04wt%, B: 0.003wt%, Zr: 0.005wt%, Nb: 0.99wt%, and the balance is Ni.

[0045] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloys prepared in this embodiment in the printed and heat-treated states are shown in Table 3. Table 3

[0046] As shown in Table 3, the room temperature yield strength and tensile strength of the alloy treated by the heat treatment process in this embodiment are improved, while the plasticity is slightly reduced. The 650℃ mid-temperature yield strength and tensile strength of the alloy treated by the heat treatment process are both improved, and the plasticity of the alloy is significantly enhanced, achieving further optimization of its mid-to-high temperature performance. Furthermore, the crease life at 760℃ / 585MPa is increased from almost zero in the printed state to 17.5 hours in the heat-treated state. In summary, the heat treatment process of this embodiment is applicable to additive manufacturing of nickel-based superalloys with other compositions using the γ' phase as the reinforcing phase according to this invention.

[0047] Comparative Example 1 The difference from Example 1 is that Comparative Example 1 does not perform hot isostatic pressing on the nickel-based superalloy printed parts, but directly performs the following heat treatment: Stress-relief annealing: The heat treatment furnace (box muffle furnace) is heated to 750℃, and the additive manufacturing nickel-based superalloy to be treated (along with the substrate) is placed in the furnace for stress-relief annealing. The holding time is 4 hours. Then, it is taken out and air-cooled to room temperature to obtain the additive manufacturing nickel-based superalloy sample after stress-relief annealing. The sample is separated from the substrate using an electrical discharge wire cutting device.

[0048] Solution treatment: The printed parts after hot isostatic pressing (HIP) are subjected to solution treatment to obtain solution-treated printed parts. Specifically, the printed parts after HIP are heated to 1120°C and subjected to solution treatment for 2 hours, then removed and air-cooled to room temperature to obtain solution-treated printed parts; wherein the heating rate is 10°C / min.

[0049] Aging treatment: The printed part after solution treatment is subjected to aging treatment to obtain an additively manufactured nickel-based superalloy. Specifically, the printed part after hot isostatic pressing is heated to 800°C and aged for 12 hours, then removed and air-cooled to room temperature to obtain the aged printed part; wherein the heating rate is 10°C / min.

[0050] The additively manufactured nickel-based superalloy samples, after complete heat treatment, were processed into tensile and creep samples to complete mechanical property testing.

[0051] Figure 8 Scanning electron microscope images of additively manufactured nickel-based superalloys prepared for this comparative example, for comparison. Figure 2 , Figure 4 It can be seen that, compared with the fully heat-treated nickel-based superalloy, cracks still exist in the matrix of the sample that has not undergone hot isostatic pressing. Compared with the printed alloy, the crack size in the alloy of this comparative example has expanded significantly after a series of heat treatments. This indicates that it is necessary to use hot isostatic pressing to eliminate microcracks after stress-relief annealing.

[0052] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloys prepared in this comparative example in the printed and heat-treated states are shown in Table 4. Table 4

[0053] As shown in Table 4, the nickel-based superalloy in Comparative Example 1, after undergoing traditional stress-relief annealing + solution treatment + aging, experienced stress concentration release, leading to the propagation and initiation of cracks in the sample, thus damaging the alloy's properties. In this embodiment, the room temperature yield strength and tensile strength of the alloy treated by the heat treatment process were improved, while the plasticity decreased slightly. The 650℃ mid-temperature yield strength and tensile strength of the alloy treated by the heat treatment process were improved, but the alloy's plasticity remained poor. Furthermore, the crease life at 760℃ / 585MPa was still at an extremely low level. In summary, the heat treatment process in this embodiment does not meet the industry standards for additive manufacturing of nickel-based superalloys.

[0054] Comparative Example 2 The difference from Example 1 is that the heat treatment process for the nickel-based superalloy printed parts in Comparative Example 1 involves hot isostatic pressing followed by solution treatment. The heat treatment process is as follows: Stress-relief annealing: The heat treatment furnace (box muffle furnace) is heated to 750℃, and the additive manufacturing nickel-based superalloy to be treated (along with the substrate) is placed in the furnace for stress-relief annealing. The holding time is 4 hours. Then, it is taken out and air-cooled to room temperature to obtain the additive manufacturing nickel-based superalloy sample after stress-relief annealing. The sample is separated from the substrate using an electrical discharge wire cutting device.

[0055] Hot Isostatic Pressing (HIP): The printed parts after solution treatment are subjected to hot isostatic pressing (HIP) to obtain HIP-treated printed parts. The parameters for HIP are as follows: the HIP temperature is 1120℃, and the HIP pressure is 180MPa; the parts are held at the HIP temperature and pressure for 2 hours, and then cooled in the furnace to obtain the HIP-treated printed parts; the heating rate of the printed parts to the HIP temperature is 30℃ / min.

[0056] Solution treatment: The printed parts after hot isostatic pressing (HIP) are subjected to solution treatment to obtain solution-treated printed parts. Specifically, the printed parts after HIP are heated to 1120°C and subjected to solution treatment for 2 hours, then removed and air-cooled to room temperature to obtain solution-treated printed parts; wherein the heating rate is 10°C / min.

[0057] Aging treatment: The printed part after solution treatment is subjected to aging treatment to obtain an additively manufactured nickel-based superalloy. Specifically, the printed part after hot isostatic pressing is heated to 800°C and aged for 12 hours, then removed and air-cooled to room temperature to obtain the aged printed part; wherein the heating rate is 10°C / min.

[0058] The additively manufactured nickel-based superalloy samples, after complete heat treatment, were processed into tensile and creep samples to complete mechanical property testing.

[0059] Figure 10 Scanning electron microscope images of additively manufactured nickel-based superalloys prepared for this comparative example, for comparison. Figure 4 , Figure 5 It can be seen that, compared with the nickel-based superalloy after heat treatment in Example 1, the γ' phase in this comparative example has a square shape, a volume fraction of γ' phase of less than 60%, and a larger γ' size after a series of heat treatments.

[0060] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloys prepared in this comparative example in the printed and heat-treated states are shown in Table 5. Table 5

[0061] As shown in Table 5, the nickel-based superalloy of Comparative Example 2 exhibits relatively low room temperature yield strength and tensile strength, with a plasticity of only 6%, after undergoing the common heat treatment sequence of stress-relief annealing + hot isostatic pressing + solution treatment + aging. Furthermore, the alloy's mechanical properties at 650℃ after heat treatment are also poor. In conclusion, the heat treatment process in this embodiment does not meet the industry standards for additive manufacturing of nickel-based superalloys.

[0062] Comparative Example 3 The difference from Example 1 is that in Comparative Example 3, when the nickel-based superalloy printed parts were subjected to solution treatment and aging, water was used as the cooling medium to cool to room temperature. The specific heat treatment regime is as follows: Stress-relief annealing: The heat treatment furnace (box muffle furnace) is heated to 750℃, and the additive manufacturing nickel-based superalloy to be treated (along with the substrate) is placed in the furnace for stress-relief annealing. The holding time is 4 hours. Then, it is taken out and air-cooled to room temperature to obtain the additive manufacturing nickel-based superalloy sample after stress-relief annealing. The sample is separated from the substrate using an electrical discharge wire cutting device.

[0063] Solution treatment: The printed parts after stress-relief annealing are subjected to solution treatment to obtain solution-treated printed parts. Specifically, the printed parts after hot isostatic pressing are heated to 1120℃ and subjected to solution treatment for 2 hours, then removed and water-cooled to room temperature to obtain solution-treated printed parts; wherein the heating rate is 10℃ / min and the cooling rate is >10℃ / s.

[0064] Hot Isostatic Pressing (HIP): The printed parts after solution treatment are subjected to hot isostatic pressing (HIP) to obtain HIP-treated printed parts. The parameters for HIP are as follows: the HIP temperature is 1120℃, and the HIP pressure is 180MPa; the parts are held at the HIP temperature and pressure for 2 hours, and then cooled in the furnace to obtain the HIP-treated printed parts; the heating rate of the printed parts to the HIP temperature is 30℃ / min.

[0065] Aging treatment: The printed part after hot isostatic pressing is subjected to aging treatment to obtain an additively manufactured nickel-based superalloy. Specifically, the printed part after hot isostatic pressing is heated to 800℃ and aged for 12 hours, then removed and water-cooled to room temperature to obtain the aged printed part; wherein the heating rate is 10℃ / min and the cooling rate is >10℃ / s.

[0066] The additively manufactured nickel-based superalloy samples, after complete heat treatment, were processed into tensile and creep samples to complete mechanical property testing.

[0067] Figure 9The macroscopic image of the additively manufactured nickel-based superalloy prepared for this comparative example shows that after a series of heat treatments, large macroscopic cracks appeared on the surface of the alloy block. The cracks started from the sample boundary and extended to the middle of the block surface. This indicates that the use of water as a cooling medium caused macroscopic cracks under thermal stress due to the large temperature difference between the surface and the center.

[0068] The instantaneous tensile and creep properties of the additively manufactured nickel-based superalloys prepared in this comparative example in the printed and heat-treated states are shown in Table 6. Table 6

[0069] As shown in Table 6, due to the use of a higher cooling rate water cooling strategy during solution treatment and aging cooling of the nickel-based superalloy in Comparative Example 3, more residual stress accumulated in the matrix, resulting in numerous cracks and macroscopic cracks in the sample, which damaged the alloy's properties. In this embodiment, the alloy treated by the heat treatment process showed improved room temperature yield strength and tensile strength, with almost no plasticity; the alloy treated by the heat treatment process also showed improved 650℃ mid-temperature yield strength and tensile strength, with almost no plasticity. Furthermore, during the 760℃ / 585MPa creep rupture life measurement, the sample fractured during the loading stage. In summary, the heat treatment process in this embodiment does not meet the industry standards for additive manufacturing of nickel-based superalloys.

[0070] In summary, the additive manufacturing method for nickel-based superalloys provided by this invention effectively solves the cracking problem in additive manufacturing of high crack-sensitive alloys, as well as the cracking problem in the post-processing stage. It provides a systematic solution for high internal quality and one-time integral forming of complex structural parts, and has important theoretical significance and industrial application value.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A heat treatment method for additively manufacturing a high volume fraction of γ' phase nickel-based superalloy, characterized in that: Comprising, The additive manufacturing nickel-based superalloy is placed at 750-800 DEG C for stress relief annealing treatment, solid solution treatment, hot isostatic pressing treatment and aging treatment to obtain the heat-treated additive manufacturing nickel-based superalloy. The additive manufacturing nickel-based superalloy comprises the following chemical components: Cr: 15.0-20.0wt%, Co: 7.0-10.0wt%, W: 2.0-3.0wt%, Mo: 1.0-2.5wt%, Al: 3.0-3.5wt%, Ti: 3.0-3.5wt%, Ta: 1.0-2.0wt%, C: 0.01-0.1wt%, B: 0.001-0.005wt%, Zr: 0.001-0.01wt%, Nb: 0.5-1.5wt%, and the balance of Ni.

2. The heat treatment method according to claim 1, wherein: The stress relief annealing treatment is to heat the heat treatment furnace to 750-800 DEG C, and the additive manufacturing nickel-based superalloy is placed in the heat treatment furnace for stress relief annealing treatment, and the holding time is 4-6h; and finally it is taken out for air cooling.

3. The heat treatment method according to claim 1, wherein: The solid solution treatment is to place the additive manufacturing nickel-based superalloy after stress relief annealing at a temperature of 1100-150 DEG C for solid solution treatment, and then air cooling.

4. The heat treatment method according to claim 1, wherein: The hot isostatic pressing treatment is to place the additive manufacturing nickel-based superalloy after solid solution treatment at a temperature of 1100-1120 DEG C under a constant pressure of 180 MPa for hot isostatic pressing treatment, and then furnace cooling.

5. The heat treatment method according to claim 1, wherein: The aging treatment is to place the additive manufacturing nickel-based superalloy after the hot isostatic pressing treatment at a temperature of 800 DEG C for aging treatment, and then room temperature air cooling.

6. The heat treatment method according to claim 1, wherein: The additive manufacturing nickel-based superalloy comprises the following chemical components: Cr: 15.72wt%, Co: 8.73wt%, W: 2.37wt%, Mo: 1.52wt%, Al: 3.23wt%, Ti: 2.94wt%, Ta: 1.45wt%, C: 0.05wt%, B: 0.002wt%, Zr: 0.002wt%, Nb: 1.02wt%, and the balance of Ni.

7. The additive manufacturing high volume fraction gamma prime nickel-based superalloy prepared by the heat treatment method of any one of claims 1-6.

8. The additively manufactured high volume fraction γ' phase nickel- base superalloy of claim 7, wherein: The additive manufacturing high volume fraction gamma prime nickel-based superalloy has no crack, and the gamma prime phase is spherical.

9. The additively manufactured high volume fraction γ' phase nickel- base superalloy of claim 7, wherein: The additive manufacturing high volume fraction gamma prime nickel-based superalloy has an average size of 300-600nm, a volume fraction of >60vol%, and an average grain size of 50-120μm.

10. The additively manufactured high volume fraction γ' phase nickel- base superalloy of claim 7, wherein: At room temperature, σb≥1300MPa, σ0.2≥1000MPa, and A≥10%; at 650 DEG C±5 DEG C, σb≥1000MPa, σ0.2≥800MPa, and A≥10%; and at 760 DEG C±5 DEG C under a constant stress of 585MPa±5MPa, the duration is ≥20h.

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