Additive manufacturing nickel-based superalloy and preparation method thereof

Abstract

The invention relates to an additive manufacturing nickel-based superalloy and a preparation method thereof, and relates to the technical field of superalloy additive manufacturing. According to the main technical scheme, a gamma'phase in a microstructure of the additive manufacturing nickel-based superalloy comprises a first gamma 'phase, a second gamma' phase and a third gamma 'phase; wherein the size of the first gamma'phase is 1-3 [mu] m, the size of the second gamma 'phase is 300-400 nm, and the size of the third gamma' phase is 30-100 nm; the density of the additive manufacturing nickel-based superalloy is not lower than 99.0%, preferably greater than or equal to 99.9%; preferably, the interior of the additive manufacturing nickel-based superalloy is free of cracks. The method is mainly used for solving the problems that an existing additive manufacturing high-temperature alloy is prone to cracking, and performance indexes of a traditional casting alloy cannot be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of superalloy additive manufacturing, and particularly to an additive manufacturing nickel-based superalloy and a preparation method thereof. Background Art

[0002] In traditional superalloy preparation technologies, such as investment casting, powder metallurgy, and deformation processing technologies, although alloys with high temperature resistance, oxidation resistance, fatigue resistance, and corrosion resistance can be produced, there are limitations in manufacturing complex structural components, with a long production cycle and high costs. With the growing demand for high-temperature and high-strength materials in fields such as aerospace, the limitations of these technologies have become more evident.

[0003] Additive manufacturing (AM) technology, especially selective laser melting (SLM), provides a new solution for the production of superalloys. AM technology enables seamless integration of design and manufacturing, eliminating the need for traditional molds and making it possible to manufacture more complex and precise structures. This technology can not only shorten the production cycle and reduce costs but also achieve better material properties through a precisely controlled manufacturing process. Significant progress has been made in the preparation of stainless steel and titanium alloys using SLM technology, and related research has become increasingly mature. For superalloys, especially nickel-based superalloys with a high γ'-phase content, the excellent properties demonstrated in commercial applications have also attracted extensive attention from the research community, and related research is being actively promoted.

[0004] However, the characteristics of rapid heating and rapid cooling during the additive manufacturing process, although helpful for obtaining finer grain structures and more uniform material properties, also bring new challenges. Different from traditional preparation processes, additive manufacturing technologies include powder feeding, powder spreading, and arc additive manufacturing, etc., all of which have the characteristics of rapid cooling and rapid heating. Therefore, it is inevitable that the alloys prepared have deficiencies such as micropores and insufficient precipitation of strengthening phases. This requires innovation in the composition adjustment and post-treatment of additive manufacturing nickel-based superalloys to adapt to this new manufacturing technology.

[0005] Existing related research has reduced the crack sensitivity by increasing a large amount of C element and Hf element, but it has brought stability problems to the microstructure of the alloy. In addition, there is also research on the influence of B and Zr elements on the cracks of the alloy. Although reducing the content of both can reduce the crack density, cracks cannot be completely eliminated. In addition, the influence of Mn and Si elements on the cracks has also been studied. Relying solely on process optimization cannot completely eliminate cracks either. There has been research on using hot isostatic pressing and heat treatment to adjust the microstructure, but the process technologies involved have not obtained ideal properties.

[0006] In summary, there is an urgent need for an additive manufacturing nickel-based superalloy and its preparation process to solve the problems of easy cracking of additive manufacturing superalloys and the inability to meet the performance indicators of traditional casting alloys. Summary of the Invention

[0007] In view of this, the present invention provides an additive manufacturing nickel-based superalloy and its preparation method, mainly aiming to solve the problems of easy cracking of existing additive manufacturing superalloys and the inability to meet the performance indicators of traditional casting alloys.

[0008] To achieve the above object, the present invention mainly provides the following technical solutions:

[0009] On the one hand, an embodiment of the present invention provides an additive manufacturing nickel-based superalloy, wherein the γ' phase in the microstructure of the additive manufacturing nickel-based superalloy includes a first γ' phase, a second γ' phase, and a third γ' phase; wherein, the size of the first γ' phase is 1-3 μm, the size of the second γ' phase is 300-400 nm, and the size of the third γ' phase is 30-100 nm; the density of the additive manufacturing nickel-based superalloy is not less than 99.0%, preferably ≥99.9%; preferably, there are no cracks inside the additive manufacturing nickel-based superalloy.

[0010] Preferably, the first γ' phase is cubic, preferably cube-shaped; the second γ' phase is cubic, preferably cube-shaped; the third γ' phase is spherical; and / or

[0011] The volume fraction of the γ' phase in the microstructure of the additive manufacturing nickel-based superalloy is 55-60%; wherein, among all the γ' phases, the volume fraction of the first γ' phase is 5-8%, the volume fraction of the second γ' phase is 77-85%, and the volume fraction of the third γ' phase is 10-15%.

[0012] Preferably, the additive manufacturing superalloy includes the following chemical components:

[0013] Cr: 16.0-18.0 wt%, Co: 8.5-10.0 wt%, W: 2.5-4.0 wt%, Ta: 2.0-3.0 wt%, Mo: 2.0-4.0 wt%, Nb: 0.5-2.0 wt%, C: 0.05-0.25 wt%, Zr: 0.01-0.05 wt%, B: 0.001-0.01 wt%, Al: 3.4-3.9 wt%, Ti: 2.9-3.6 wt%, and the balance is Ni;

[0014] Preferably, by weight percentage, the additive manufacturing superalloy comprises the following chemical components: Cr: 17.0 - 18.0 wt%, Co: 9.0 - 10.0 wt%, W: 3.0 - 4.0 wt%, Ta: 2.0 - 3.0 wt%, Mo: 2.8 - 4.0 wt%, Nb: 1.2 - 2.0 wt%, C: 0.12 - 0.25 wt%, Zr: 0.01 - 0.025 wt%, B: 0.001 - 0.005 wt%, Al: 3.4 - 3.8 wt%, Ti: 2.9 - 3.2 wt%, and the balance is Ni.

[0015] Preferably, the yield strength of the additive manufacturing nickel - based superalloy at room temperature > 900 MPa, the fracture strength > 1380 MPa, and the fracture plasticity > 10%; and / or the yield strength of the additive manufacturing nickel - based superalloy at 650 °C > 950 MPa, the fracture strength > 1250 MPa, and the fracture plasticity > 10%.

[0016] Preferably, the preparation method comprises the following steps:

[0017] Additive manufacturing treatment: performing additive manufacturing treatment on the nickel - based superalloy powder to obtain a printed part;

[0018] Hot isostatic pressing treatment: performing hot isostatic pressing treatment on the printed part to obtain a printed part after hot isostatic pressing treatment;

[0019] Solution and aging treatment: performing solution and aging treatment on the printed part after hot isostatic pressing treatment to obtain an additive manufacturing nickel - based superalloy.

[0020] Preferably, in the step of the additive manufacturing treatment:

[0021] Performing additive manufacturing treatment on the nickel - based superalloy powder by using the selective laser melting additive manufacturing process SLM to obtain a printed part;

[0022] Preferably, the parameters of the selective laser melting additive manufacturing process SLM are as follows: the laser power is 150 - 310 W, the scanning speed is 700 - 1300 mm / min, the layer rotation angle is 55 - 80 °, the single - layer thickness is 0.03 - 0.05 mm, the track spacing is 0.06 - 0.10 mm, and the laser spot diameter is 0.05 - 0.1 mm; preferably, the protective gas is selected from Ar gas or N2 gas.

[0023] Preferably, in the step of the hot isostatic pressing treatment:

[0024] The temperature of the hot isostatic pressing treatment is 1160 - 1200 °C, and the pressure of the hot isostatic pressing treatment is 150 - 180 MPa; at the temperature and pressure of the hot isostatic pressing treatment, heat preservation is carried out for 2 - 4 h, and then cooling is carried out to obtain a printed part after the hot isostatic pressing treatment;

[0025] Preferably, the cooling method is furnace cooling;

[0026] Preferably, the heating rate for heating the printed part to the temperature of the hot isostatic pressing treatment is 20 - 30 °C / min.

[0027] Preferably, in the solution treatment and aging treatment steps:

[0028] The printed part after the hot isostatic pressing treatment is heated to 1120 - 1160 °C for solution treatment for 1 - 3 h, and after cooling, a printed part after the solution treatment is obtained; the printed part after the solution treatment is heated to 1040 - 1100 °C for primary aging treatment for 2 - 8 h, and after cooling, a printed part after the primary aging treatment is obtained; the printed part after the primary aging treatment is heated to 850 - 900 °C for secondary aging treatment for 15 - 30 h, and after cooling, an additive manufacturing nickel-based superalloy is obtained;

[0029] Preferably, the cooling method is air cooling;

[0030] Preferably, the heating rate is 5 - 15 °C / min.

[0031] Preferably, before the additive manufacturing treatment step, the following steps are further included:

[0032] Design a preset chemical composition range: According to the influence of the elements of the superalloy on cracks, determine the content ranges of the solution strengthening elements W, Mo, Co, Cr, Nb, Ta and the grain boundary strengthening elements C, B, Zr, and design the ranges of Al and Ti through thermodynamic software to obtain the preset chemical composition range of the nickel-based superalloy;

[0033] Experimental screening: Screen the required chemical composition of the nickel-based superalloy and the best process parameters for the additive manufacturing treatment;

[0034] Preferably, in the step of experimental screening: First, use thermodynamic simulation software to evaluate the effects of different elements on the solidification temperature range and low-melting-point phases of the alloy to determine the elements that help narrow the solidification temperature range and reduce the formation of low-melting-point phases; Subsequently, combined with the strengthening effect of solid solution elements, increase the solid solution elements to improve the solid solution strength of the superalloy matrix; Then, determine the optimal content of age-hardening elements based on the strain aging sensitivity to ensure the high-temperature stability of the alloy; At the same time, to suppress cracks, when selecting process parameters, internal residual stress and the Hall-Petch grain boundary strengthening effect need to be considered, and process parameters that can refine the grain size and reduce residual stress are selected; Finally, screening is carried out by analyzing the experimental results of thermodynamic calculations and high-throughput experimental data to determine the required chemical composition of the nickel-based superalloy and the optimal process parameters for additive manufacturing treatment;

[0035] Preferably, by weight percentage, the preset chemical composition range includes: Cr: 14 - 18.0 wt%, Co: 7 - 10.0 wt%, W: 1.5 - 4.0 wt%, Ta: 0.5 - 3.0 wt%, Mo:

[0036] 1.0 - 4.0 wt%, Nb: 0.1 - 2.0 wt%, C: 0 - 0.0.25 wt%, Zr: 0 - 0.10 wt%, B: 0 - 0.03 wt%, Al: 2.0 - 5.0 wt%, Ti: 2.0 - 4.5 wt%, and the balance is Ni;

[0037] Preferably, the required additive manufacturing superalloy selected includes the following chemical composition:

[0038] Cr: 16.0 - 18.0 wt%, Co: 8.5 - 10.0 wt%, W: 2.5 - 4.0 wt%, Ta: 2.0 - 3.0 wt%, Mo: 2.0 - 4.0 wt%, Nb: 0.5 - 2.0 wt%, C: 0.05 - 0.25 wt%, Zr: 0.01 - 0.05 wt%, B: 0.001 - 0.01 wt%, Al: 3.4 - 3.9 wt%, Ti: 2.9 - 3.6 wt%, and the balance is Ni;

[0039] Preferably, Cr: 17.0 - 18.0 wt%, Co: 9.0 - 10.0 wt%, W: 3.0 - 4.0 wt%, Ta: 2.0 - 3.0 wt%, Mo: 2.8 - 4.0 wt%, Nb: 1.2 - 2.0 wt%, C: 0.12 - 0.25 wt%, Zr: 0.01 - 0.025 wt%, B: 0.001 - 0.005 wt%, Al: 3.4 - 3.8 wt%, Ti: 2.9 - 3.2 wt%, and the balance is Ni;

[0040] Preferably, in the experimental screening steps: based on the preset chemical composition range of the nickel-based superalloy, multiple groups of nickel-based superalloy compositions are designed, and multiple alloy powders are prepared; a selective laser melting printing device is used to print samples corresponding to multiple groups of process parameters on the substrate for each group of alloy powders; the printed samples are subjected to crack and porosity analysis, the cracks and pores are quantitatively counted to obtain the selected printing process window, and the samples are observed through the microstructure to exclude the chemical composition range that causes cracks, and the chemical composition range corresponding to the crack-free samples is screened out to obtain the chemical composition of the required nickel-based superalloy.

[0041] Preferably, before the step of hot isostatic pressing treatment, a heat treatment design step is further included; wherein, the heat treatment design step further includes:

[0042] Step 1) Formulate the hot isostatic pressing treatment and the process parameter range

[0043] According to the structural characteristics of the printed part, hot isostatic pressing treatment is selected for the printed part to eliminate the internal holes and cracks of the printed part, and improve the density and mechanical properties of the material;

[0044] Determine the remelting temperature of γ′ and the transformation temperature of the precipitated phase of the additive manufacturing superalloy required, and determine the process parameters of the hot isostatic pressing treatment to avoid primary melting;

[0045] Step 2) Design the solution treatment and aging treatment system

[0046] Design the process parameters of the solution treatment and aging treatment system so that the microstructure of the additive manufacturing nickel-based superalloy after aging treatment includes three sizes of γ′ phases, specifically the first γ′ phase, the second γ′ phase, and the third γ′ phase; wherein, the size of the first γ′ phase is 1-3 μm, the size of the second γ′ phase is 300-400 nm, and the size of the third γ′ phase is 30-100 nm.

[0047] Compared with the prior art, an additive manufacturing nickel-based superalloy and a preparation method thereof of the present invention at least have the following beneficial effects:

[0048] On the one hand, an embodiment of the present invention provides an additive manufacturing nickel-based superalloy. The γ' phase in the microstructure of the additive manufacturing nickel-based superalloy includes a first γ' phase, a second γ' phase, and a third γ' phase. Among them, the size of the first γ' phase is 1-3 μm, the size of the second γ' phase is 300-400 nm, and the size of the third γ' phase is 30-100 nm. Preferably, the first γ' phase is cubic, preferably cube-shaped; the second γ' phase is cubic, preferably cube-shaped; the third γ' phase is spherical. Preferably, the volume fraction of the γ' phase in the microstructure of the additive manufacturing nickel-based superalloy is 55-60%. Among them, among all the γ' phases, the volume fraction of the first γ' phase is 5-8%, the volume fraction of the second γ' phase is 77-85%, and the volume fraction of the third γ' phase is 10-15%. Regarding the additive manufacturing nickel-based superalloy with the above-mentioned microstructure proposed in the embodiment of the present invention, the following is described: In the matrix, the fine third γ' phase is densely and evenly distributed on the matrix, with a very large number, building a fine network structure. The medium-sized second γ' phase is evenly distributed in the matrix and has the largest number. They widely exist inside the alloy and constitute the key part to improve the material properties. The relatively large-sized first γ' phase is relatively few and dispersed in the matrix, with the smallest number. They exist relatively isolated in the matrix, which helps to improve the thermal fatigue resistance and fracture toughness of the material. This multi-scale γ' phase distribution method enables the alloy to achieve the best balance in terms of strength, toughness, and high-temperature performance. The fine third γ' phase effectively hinders the movement of dislocations through its dense network structure, thereby improving the yield strength and tensile strength of the material. The medium-sized second γ' phase enhances the creep resistance of the material while maintaining a relatively high strength. The relatively large-sized first γ' phase reduces the initiation and propagation of thermal fatigue cracks through its relatively discrete distribution, thereby improving the thermal fatigue resistance of the material. Therefore, an additive manufacturing nickel-based superalloy proposed in the embodiment of the present invention can solve the problems of easy cracking in existing additive manufacturing superalloys and the inability to reach the performance indicators of traditional cast alloys.

[0049] Further, an additive manufacturing nickel-based superalloy provided by an embodiment of the present invention, by weight percentage, the additive manufacturing superalloy comprises the following chemical components: Cr: 16.0-18.0 wt%, Co: 8.5-10.0 wt%, W: 2.5-4.0 wt%, Ta: 2.0-3.0 wt%, Mo: 2.0-4.0 wt%, Nb: 0.5-2.0 wt%, C: 0.05-0.25 wt%, Zr: 0.01-0.05 wt%, B: 0.001-0.01 wt%, Al: 3.4-3.9 wt%, Ti: 2.9-3.6 wt%, and the balance is Ni. Preferably, by weight percentage, the additive manufacturing superalloy comprises the following chemical components: Cr: 17.0-18.0 wt%, Co: 9.0-10.0 wt%, W: 3.0-4.0 wt%, Ta: 2.0-3.0 wt%, Mo: 2.8-4.0 wt%, Nb: 1.2-2.0 wt%, C: 0.12-0.25 wt%, Zr: 0.01-0.025 wt%, B: 0.001-0.005 wt%, Al: 3.4-3.8 wt%, Ti: 2.9-3.2 wt%, and the balance is Ni. It should be noted here that: the embodiment of the present invention is based on the composition of the traditional cast IN738 alloy and is improved to the above chemical composition range to prepare crack-free printed parts through additive manufacturing treatment.

[0050] On the other hand, an embodiment of the present invention provides a preparation method for an additive manufacturing nickel-based superalloy. Based on the above chemical composition, the present invention designs a selective laser melting additive manufacturing process SLM and controls the corresponding process parameters to prepare crack-free printed parts; further, the present invention suppresses micropores and cracks in the printed parts through hot isostatic pressing treatment. On this basis, the present invention designs a solution and aging treatment adapted to the above chemical composition to retain a small part of the large-sized γ' phase in the printed parts after hot isostatic pressing treatment, and convert another part of the large-sized γ' phase into small-sized and medium-sized γ' phases, and finally obtain three sizes of γ' phases, so that the heat-treated additive manufacturing nickel-based superalloy can not only inhibit cracks, but also has excellent comprehensive performance, which is superior to that of the traditional cast IN738 alloy.

[0051] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following takes the preferred embodiments of the present invention and describes them in detail in conjunction with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a microstructural diagram of an additive manufacturing nickel-based superalloy prepared in Example 1;

[0053] Figure 2It is the microstructural diagram of the printed part after hot isostatic pressing in Embodiment 1 of the present invention;

[0054] Figure 3 It is the SEM diagram of the printed part after additive manufacturing in Embodiment 1 of the present invention; among them, Figure 3 The magnification factors of Figures (a) and (b) in it are different;

[0055] Figure 4 It is the microstructural diagram of an additive manufactured nickel-based superalloy prepared in Embodiment 2;

[0056] Figure 5 It is the microstructural diagram of an additive manufactured nickel-based superalloy prepared in Embodiment 3;

[0057] Figure 6 It is the SEM diagram of the printed part after additive manufacturing in Comparative Example 2;

[0058] Figure 7 It is the microstructural diagram of the alloy in Comparative Example 3; among them, Figure 7 Figure (a) in it is the microstructural diagram of the printed part prepared in Comparative Example 3, and obvious cracks can be seen in the printed part; Figure (b) is the microstructural diagram of the printed part after heat treatment in Comparative Example 3;

[0059] Figure 8 It is the microstructural diagram of an additive manufactured nickel-based superalloy prepared in Comparative Example 4;

[0060] Figure 9 It is the microstructural diagram of an additive manufactured nickel-based superalloy prepared in Comparative Example 5; among them, Figure 9 Figure (a) in it is the microstructural diagram of the printed part after heat treatment in Comparative Example 5, and Figure (b) is an enlarged view of Figure (a);

[0061] Figure 10 It is the specimen diagram of an additive nickel-based superalloy sample with dimensions of 16×16×50 mm in the embodiment for tensile and creep performance tests;

[0062] Figure 11 It is the comparison diagram of the creep performance results between the additive manufactured nickel-based superalloy specimen prepared in Embodiment 1 and other studies. Detailed implementation manners

[0063] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the accompanying drawings and preferred embodiments to detail the specific implementation manners, structures, features, and their effects of the application according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0064] On the one hand, an embodiment of the present invention provides an additive manufactured nickel-based superalloy, wherein, as Figure 1 shown, the γ'-phase in the microstructure of the additive manufactured nickel-based superalloy includes a first γ'-phase, a second γ'-phase, and a third γ'-phase; wherein, the size of the first γ'-phase is 1 μm - 3 μm, the size of the second γ'-phase is 300 - 400 nm, and the size of the third γ'-phase is 30 - 100 nm. Preferably, the third γ'-phase is spherical (the "size" is the diameter of the spherical γ'-phase); the second γ'-phase is cubic (the "size" is the side length of the cubic γ'-phase), preferably a cube; the first γ'-phase is cubic (the "size" is the side length of the cubic γ'-phase), preferably a cube. Preferably, the volume fraction of the γ'-phase in the microstructure of the additive manufactured nickel-based superalloy is 55 - 60%; wherein, among all the γ'-phases, the volume fraction of the first γ'-phase is 5 - 8%, the volume fraction of the second γ'-phase is 77 - 85%, and the volume fraction of the third γ'-phase is 10 - 15%.

[0065] Preferably, by weight percentage, the additive manufactured superalloy comprises the following chemical components:

[0066] Cr: 16.0 - 18.0 wt% (preferably 17.0 - 18.0 wt%), Co: 8.5 - 10.0 wt% (preferably 9.0 - 10.0 wt%), W: 2.5 - 4.0 wt% (preferably 3.0 - 4.0 wt%), Ta: 2.0 - 3.0 wt% (preferably 2.0 - 3.0 wt%), Mo: 2.0 - 4.0 wt% (preferably 2.8 - 4.0 wt%), Nb: 0.5 - 2.0 wt% (preferably 1.2 - 2.0 wt%), C: 0.05 - 0.25 wt% (preferably 0.12 - 0.25 wt%), Zr: 0.01 - 0.05 wt% (preferably 0.01 - 0.025 wt%), B: 0.001 - 0.01 wt% (preferably 0.001 - 0.005 wt%), Al: 3.4 - 3.9 wt% (preferably 3.4 - 3.8 wt%), Ti: 2.9 - 3.6 wt% (preferably 2.9 - 3.2 wt%), and the balance is Ni.

[0067] On the other hand, an embodiment of the present invention provides a preparation method of an additive manufactured nickel-based superalloy, mainly including the following steps:

[0068] Additive manufacturing treatment: performing additive manufacturing treatment on the nickel-based superalloy powder to obtain a printed part.

[0069] Among them, in this step, selective laser melting additive manufacturing process is used to perform additive manufacturing on nickel-based superalloy powder to obtain a printed part;

[0070] Among them, the parameters of the selective laser melting additive manufacturing process are as follows: the laser power is 150 - 310W, the scanning speed is 700 - 1300mm / min, the layer rotation angle is 55 - 80°, the single layer thickness is 0.03 - 0.05mm, the track spacing is 0.06 - 0.10mm, and the laser spot diameter is 0.05 - 0.1mm; preferably, the protective gas is selected from Ar gas or N2 gas.

[0071] Hot isostatic pressing treatment: The printed part is subjected to hot isostatic pressing treatment to obtain a printed part after hot isostatic pressing treatment.

[0072] Among them, in this step: the temperature of the hot isostatic pressing treatment is 1160 - 1200°C, and the pressure of the hot isostatic pressing treatment is 150 - 180MPa; at the temperature and pressure of the hot isostatic pressing treatment, keep warm for 2 - 4h, and then cool to obtain a printed part after hot isostatic pressing treatment; preferably, the cooling method is furnace cooling; preferably, the heating rate of the printed part to the temperature of the hot isostatic pressing treatment is 20 - 30°C / min.

[0073] It should be noted here that in the embodiment of the present invention, the step of hot isostatic pressing treatment is used to eliminate dislocations and cracks in the printed part; however, after the hot isostatic pressing treatment, the size of the γ' phase in the printed part will increase (generally becoming large-sized γ' phase).

[0074] Solution and aging treatment: The printed part after the hot isostatic pressing treatment is subjected to solution and aging treatment to obtain an additive manufacturing nickel-based superalloy.

[0075] Preferably, in this step, the printed part after the hot isostatic pressing treatment is heated to 1120 - 1160°C for solution treatment for 1 - 3h, and after cooling, a printed part after solution treatment is obtained; the printed part after solution treatment is heated to 1040 - 1100°C for primary aging treatment for 2 - 8h, and after cooling, a printed part after primary aging treatment is obtained; the printed part after primary aging treatment is heated to 850 - 900°C for secondary aging treatment for 15 - 30h, and after cooling, an additive manufacturing nickel-based superalloy is obtained.

[0076] It should be noted here that: the carbides in the printed part are nano-sized MC-type carbides. The above heat treatment system in the embodiment of the present invention avoids the significant increase and aggregation of the carbide size. The dispersed carbides can pin the grain boundaries, strengthen the matrix, and improve the mechanical properties of the alloy.

[0077] Regarding the design of the solution treatment and aging treatment steps of the embodiments of the present invention, the following explanations are needed: As described above, after hot isostatic pressing treatment, the size of the γ' phase in the printed parts will increase (generally becoming large-sized γ' phases). However, when the present inventor designed the solution treatment and aging treatment, it was desired to retain a part of the large-sized γ' phases, and the rest would become two different-sized γ' phases, and finally three different-sized γ' phases were obtained. Under the synergistic effect of these three γ' phases, the mechanical properties of the additive manufacturing nickel-based superalloy of the present invention were significantly improved. Based on this design, the above-mentioned solution treatment and aging treatment parameters were proposed. In the microstructure of the additive manufacturing nickel-based superalloy after the existing heat treatment, there are no three-sized γ' phases described in the present invention (specifically, the largest-sized γ' phase is formed due to the precipitation and growth of the γ' phase after hot isostatic pressing treatment. During the solution treatment process, part of the large-sized γ' phases are dissolved (retaining a part of the large-sized γ' phases), and fine spherical γ' phases will precipitate after cooling. Through the first-stage aging treatment, part of the fine spherical γ' phases grow into cubes (medium-sized γ' phases), and then through the second-stage aging treatment, more γ' phases are precipitated, and at the same time, the finer γ' phases grow).

[0078] Preferably, the embodiments of the present invention provide a preparation method for an additive manufacturing nickel-based superalloy. Before the additive manufacturing treatment, the following steps are further included: designing the element range of the nickel-based superalloy, screening the crack-free composition range by combining thermodynamic software calculation and high-throughput experiments; screening the process parameters of selective laser melting additive manufacturing.

[0079] Specifically, the constituent elements of the nickel-based superalloy are divided into four categories and adjusted separately according to the functions of the elements. By weight percentage, the chemical composition includes: solution strengthening elements: Cr 14.0 - 18.0 wt%, Co 7.0 - 10.0 wt%, W 1.5 - 4.0 wt%, Ta 0.5 - 3.0 wt%, Mo 1.0 - 4.0 wt%, Nb 0.1 - 2.0 wt%; grain boundary strengthening elements: C ≤ 0.25 wt%, Zr < 0.10 wt%, B ≤ 0.03 wt%; precipitation strengthening elements: Al 2.0 - 5.0 wt%, Ti 2.0 - 4.5 wt%; the balance is Ni and impurity elements (such as Mn, Si, and P).

[0080] To obtain a higher matrix strength, increase the content of solution strengthening elements; reduce the crack sensitivity while ensuring the grain boundary strengthening effect, so the content of grain boundary strengthening elements is reduced but not eliminated; reduce the content of other impurity elements to obtain an optimized composition range: Cr: 16.0 - 18.0 wt% (preferably 17.0 - 18.0 wt%), Co: 8.5 - 10.0 wt% (preferably 9.0 - 10.0 wt%), W: 2.5 - 4.0 wt% (preferably 3.0 - 4.0 wt%), Ta: 2.0 - 3.0 wt% (preferably 2.0 - 3.0 wt%), Mo: 2.0 - 4.0 wt% (preferably 2.8 - 4.0 wt%), Nb: 0.5 - 2.0 wt% (preferably 1.2 - 2.0 wt%), C: 0.05 - 0.25 wt% (preferably 0.12 - 0.25 wt%), Zr: 0.01 - 0.05 wt% (preferably 0.01 - 0.025 wt%), B: 0.001 - 0.01 wt% (preferably 0.001 - 0.005 wt%), Al: 3.4 - 3.9 wt% (preferably 3.4 - 3.8 wt%), Ti: 2.9 - 3.6 wt% (preferably 2.9 - 3.2 wt%), and the balance is Ni.

[0081] Use a selective laser melting (SLM) printing device to print samples with multiple sets of process parameters on a substrate; perform crack and porosity analysis on the printed superalloy, quantify and statistically analyze the cracks and porosity to obtain an optimal process window; determine the composition range where cracks occur through microscopic microstructure observation.

[0082] Preferably, according to the characteristics of rapid cooling and rapid heating in additive manufacturing, the structure after additive manufacturing is a γ matrix and MC carbides; at the same time, optimize the composition according to the elements affecting the formation of strain aging cracks and liquation cracks. To improve the strength of the matrix and avoid stress cracks, increase the solution strengthening elements and C element to improve the strength of the matrix. Excessive γ′ phase forming elements and low melting point forming elements will increase the crack sensitivity, so reduce the B and Zr, Ti and Al elements.

[0083] Before the step of hot isostatic pressing treatment, a heat treatment design step is also included; wherein, the heat treatment design step further includes:

[0084] Step 1) Formulate the hot isostatic pressing treatment and process parameter range

[0085] According to the structural characteristics of the printed part, select to perform hot isostatic pressing treatment on the printed part to eliminate the holes and cracks inside the printed part, and improve the density and mechanical properties of the material;

[0086] Determine the remelting temperature of γ′ and the transformation temperature of the precipitation phase of the required additive manufacturing superalloy, and determine the process parameters of the hot isostatic pressing treatment to avoid primary melting.

[0087] Step 2) Design the solution treatment and aging treatment system

[0088] Design the process parameters of the solution treatment and aging treatment system so that the microstructure of the additive manufactured nickel-based superalloy after aging treatment includes three sizes of γ′ phases, specifically the first γ′ phase, the second γ′ phase, and the third γ′ phase; among them, the size of the first γ′ phase is 1 - 3 μm, the size of the second γ′ phase is 300 - 400 nm, and the size of the third γ′ phase is 30 - 100 nm.

[0089] Specifically, in order to retain some large-sized γ′ phases after hot isostatic pressing, the printed parts after hot isostatic pressing are heated to 1120 - 1160 °C for solution treatment for 1 - 3 h. After cooling, the printed parts after solution treatment are obtained; in order to control the spherical γ′ phase precipitated after solution treatment into a cubic shape and to ensure a more stable structure, a double aging heat treatment system is introduced. The printed parts after solution treatment are heated to 1040 - 1100 °C for the first-stage aging treatment for 2 - 8 h. After cooling, the printed parts after the first-stage aging treatment are obtained; in order to further increase the proportion of γ′ in the alloy and the strengthening effect of the spherical γ′ phase, the printed parts after the first-stage aging treatment are heated to 850 - 900 °C for the second-stage aging treatment for 15 - 30 h. After cooling, the additive manufactured nickel-based superalloy is obtained;

[0090] In summary, an additive manufactured nickel-based superalloy and its preparation method provided by the embodiments of the present invention have at least the following advantages:

[0091] (1) By precisely controlling the alloy composition and coordinating the contents of grain boundary strengthening elements such as C, Zr, and B, as well as solution and precipitation strengthening elements such as Co, Cr, Mo, W, Al, Ti, Nb, and Ta, the embodiments of the present invention reduce the crack sensitivity of the nickel-based superalloy (IN738 alloy). The present invention enhances the crack propagation resistance of the alloy, significantly reduces the crack tendency during the additive manufacturing process, and thus improves the overall performance and durability of the alloy.

[0092] (2) The present invention reduces the crack tendency, enlarges the processing process window, and improves the comprehensive performance of the superalloy by adjusting the alloy composition and adopting specific post-treatment processes such as hot isostatic pressing (HIP) and appropriate heat treatment. And it is verified that the effect of optimizing the alloy composition, especially coordinating and adjusting the contents of grain boundary strengthening elements, solution strengthening elements, and precipitation strengthening elements, is effective. The present invention improves the creep resistance of the alloy at high temperatures, enabling it to have a longer creep rupture life and higher reliability in high-temperature environments.

[0093] (3) The present invention improves the performance of the alloy and broadens the application fields of the alloy. Compared with the traditional preparation technology of IN738 cast superalloy, the additive manufacturing technology adopted by the present invention does not require a mold and can directly form components with complex structures, greatly shortening the production cycle and reducing the production cost. The present invention not only improves the high-temperature performance and crack resistance of IN738 nickel-based superalloy, but also realizes the comprehensive improvement of material properties by optimizing the additive manufacturing process and post-treatment technology, meeting the urgent needs of high-performance materials in the fields of aerospace and the like.

[0094] In summary, the present invention realizes the multi-peak uniform distribution of γ' phase and the uniform distribution of carbides in the nickel-based superalloy, significantly improving the strength, plasticity and creep life of the alloy, and the comprehensive mechanical properties are better than those of traditional forgings. The present invention effectively solves the cracking problem in the additive manufacturing of alloys with high crack sensitivity, provides a systematic solution for the high internal quality and one-time integral forming of complex structural parts, and has important theoretical significance and industrial application value.

[0095] The present invention is further described below through specific embodiments:

[0096] Example 1

[0097] In this embodiment, an additive manufacturing nickel-based superalloy is prepared. Among them, in terms of weight percentage, the additive manufacturing nickel-based superalloy includes the following chemical components:

[0098] Al (3.4 wt%), Ti (2.9 wt%), the combined content of Al+Ti is 6.3 wt%, Co (9 wt%), Cr (16.0 wt%), W (3.0 wt%), Mo (2.0 wt%), the combined content of Co+Cr+W+Mo is 30 wt%, Ta (2.0 wt%), Nb (0.9 wt%), B (0.005 wt%), C (0.1 wt%), Zr (0.01 wt%), and the balance is Ni.

[0099] Among them, it mainly includes the following steps:

[0100] Additive manufacturing treatment: Selective laser melting (SLM) additive manufacturing treatment is carried out on the nickel-based superalloy powder to obtain a printed part. Among them, the process parameters of the selective laser melting additive manufacturing treatment are as follows: the laser power is 230 W, the scanning speed is 900 mm / min, the layer rotation angle is 67°, the single layer thickness is 0.03 mm, the track spacing is 0.08 mm, the laser spot diameter is 0.06 mm, and the shielding gas is Ar gas.

[0101] Among them, the SEM diagram of the printed part is shown in Figure 3 as shown. From Figure 3It can be seen that: through additive manufacturing treatment, the printed parts obtained have no cracks.

[0102] Hot isostatic pressing treatment: The printed parts are subjected to hot isostatic pressing treatment to obtain the printed parts after hot isostatic pressing treatment. Among them, the parameters of the hot isostatic pressing treatment are as follows: the temperature of the hot isostatic pressing treatment is 1180 °C, and the pressure of the hot isostatic pressing treatment is 160 MPa; at the temperature and pressure of the hot isostatic pressing treatment, keep warm for 2 h, and then cool with the furnace to obtain the printed parts after hot isostatic pressing treatment; among them, the heating rate of the printed parts to the temperature of the hot isostatic pressing treatment is 30 °C / min.

[0103] Among them, here through hot isostatic pressing treatment, the micropores and cracks of the printed parts are further inhibited. For the microstructure diagram of the printed parts after hot isostatic pressing treatment, see Figure 2 as shown. The size of the γ′ phase in the printed parts increases and becomes a large-size γ′ phase.

[0104] Solution and aging treatment: The printed parts after the hot isostatic pressing treatment are subjected to solution and aging treatment to obtain an additively manufactured nickel-based superalloy. Among them, the printed parts after the hot isostatic pressing treatment are heated to 1120 °C for solution treatment for 2 h, and after cooling, the printed parts after solution treatment are obtained; the printed parts after solution treatment are heated to 1080 °C for aging treatment for 4 h, and after cooling, the printed parts after primary aging treatment are obtained; the printed parts after primary aging treatment are heated to 850 °C for secondary aging treatment for 24 h, and after cooling, an additively manufactured nickel-based superalloy is obtained; among them, the heating rate is 10 °C / min.

[0105] For the microstructure diagram of the additively manufactured nickel-based superalloy obtained in this embodiment, see Figure 1 as shown. From Figure 1 it can be seen that: the γ′ phase in the microstructure of the additively manufactured nickel-based superalloy includes the first γ′ phase, the second γ′ phase, and the third γ′ phase; among them, the size of the first γ′ phase is 1 μm - 3 μm, the size of the second γ′ phase is 300 - 400 nm, and the size of the third γ′ phase is 30 - 100 nm. The first γ′ phase is cubic; the second γ′ phase is cube-shaped; the third γ′ phase is spherical. And, the volume fraction of the γ′ phase in the microstructure of the additively manufactured nickel-based superalloy is 55 - 60%; among them, among all the γ′ phases, the volume fraction of the first γ′ phase is 5 - 8%, the volume fraction of the second γ′ phase is 77 - 85%, and the volume fraction of the third γ′ phase is 10 - 15%.

[0106] By conducting tensile property tests on the additively manufactured nickel-based superalloy prepared in this embodiment, the yield strengths at room temperature and 650 °C are measured. The experimental results are shown in Tables 1 and 2.

[0107] By conducting a creep performance test on the additive manufacturing nickel-based superalloy prepared in this embodiment (for the specimen diagram of the creep performance test, see Figure 10 as shown), the creep life of the alloy under the conditions of 760 °C and 590 MPa is 112 h.

[0108] Example 2

[0109] In this embodiment, an additive manufacturing nickel-based superalloy is prepared. In terms of weight percentage, the additive manufacturing nickel-based superalloy includes the following chemical components:

[0110] Al (3.5 wt%), Ti (3.2 wt%), and the combined content of Al + Ti is 6.7 wt%; Co (9.1 wt%), Cr (17 wt%), W (3.0 wt%), Mo (2.8 wt%), and the combined content of Co + Cr + W + Mo is 31.9 wt%, Ta (2 wt%), Nb (1.2 wt%), B (0.005 wt%), C (0.12 wt%), Zr (0.03 wt%), and the balance is Ni.

[0111] It mainly includes the following steps:

[0112] Additive manufacturing process: The nickel-based superalloy powder is subjected to selective laser melting additive manufacturing (SLM) to obtain a printed part. Among them, the process parameters of the selective laser melting additive manufacturing are as follows: the laser power is 230 W, the scanning speed is 900 mm / min, the layer rotation angle is 67°, the single-layer thickness is 0.03 mm, the track spacing is 0.08 mm, the laser spot diameter is 0.06 mm, and the shielding gas is Ar gas.

[0113] Among them, in this embodiment, through the additive manufacturing process, the obtained printed part has no cracks.

[0114] Hot isostatic pressing process: The printed part is subjected to hot isostatic pressing to obtain a printed part after hot isostatic pressing. Among them, the parameters of the hot isostatic pressing are as follows: the temperature of the hot isostatic pressing is 1180 °C, the pressure of the hot isostatic pressing is 160 MPa; at the temperature and pressure of the hot isostatic pressing, it is kept warm for 2 h, and then cooled with the furnace to obtain a printed part after hot isostatic pressing; among them, the heating rate of the printed part to the temperature of the hot isostatic pressing is 30 °C / min.

[0115] Solution and aging treatment: The printed parts after hot isostatic pressing are subjected to solution and aging treatment to obtain an additive manufacturing nickel-based superalloy. Among them, the printed parts after hot isostatic pressing are heated to 1120 °C for 2 h of solution treatment. After cooling, the printed parts after solution treatment are obtained; the printed parts after solution treatment are heated to 1080 °C for 4 h of primary aging treatment. After cooling, the printed parts after primary aging treatment are obtained; the printed parts after primary aging treatment are heated to 850 °C for 24 h of secondary aging treatment. After cooling, an additive manufacturing nickel-based superalloy is obtained; among them, the heating rate is 10 °C / min.

[0116] As Figure 4 shown, the γ′ phase in the microstructure of the additive manufacturing nickel-based superalloy obtained in this embodiment includes a first γ′ phase, a second γ′ phase, and a third γ′ phase; among them, the size of the first γ′ phase is 1 μm - 3 μm, the size of the second γ′ phase is 300 - 400 nm, and the size of the third γ′ phase is 30 - 100 nm. The first γ′ phase is cubic; the second γ′ phase is cubic; the third γ′ phase is spherical. And, the volume fraction of the γ′ phase in the microstructure of the additive manufacturing nickel-based superalloy is 55 - 60%; among them, in all γ′ phases, the volume fraction of the first γ′ phase is 5 - 8%, the volume fraction of the second γ′ phase is 77 - 85%, and the volume fraction of the third γ′ phase is 10 - 15%.

[0117] By performing a tensile property test on the additive manufacturing nickel-based superalloy prepared in this embodiment, the yield strength at room temperature and 650 °C is measured. The experimental results are shown in Tables 1 and 2.

[0118] By performing a creep property test on the additive manufacturing nickel-based superalloy prepared in this embodiment, the creep life of the alloy at 760 °C and 590 MPa is obtained as 128 h.

[0119] Example 3

[0120] This embodiment prepares an additive manufacturing nickel-based superalloy. Among them, in terms of weight percentage, this additive manufacturing nickel-based superalloy includes the following chemical components:

[0121] Al (3.5 wt%), Ti (3.2 wt%), and the combined content of Al + Ti is 6.7 wt%; Co (9.1 wt%), Cr (17 wt%), W (3.0 wt%), Mo (2.8 wt%), and the combined content of Co + Cr + W + Mo is 31.9 wt%, Ta (2 wt%), Nb (1.2 wt%), B (0.005 wt%), C (0.12 wt%), Zr (0.03 wt%), and the balance is Ni.

[0122] The main steps are as follows:

[0123] Additive manufacturing process: The nickel-based superalloy powder is subjected to selective laser melting additive manufacturing process (SLM) to obtain a printed part. Among them, the process parameters of the selective laser melting additive manufacturing process are as follows: the laser power is 230 W, the scanning speed is 900 mm / min, the layer rotation angle is 67°, the single layer thickness is 0.03 mm, the track spacing is 0.08 mm, the laser spot diameter is 0.06 mm, and the protective gas is Ar gas.

[0124] Among them, in this embodiment, through the additive manufacturing process, the obtained printed part has no cracks.

[0125] Hot isostatic pressing process: The printed part is subjected to hot isostatic pressing process to obtain a printed part after hot isostatic pressing. Among them, the parameters of the hot isostatic pressing process are as follows: the temperature of the hot isostatic pressing process is 1180 °C, the pressure of the hot isostatic pressing process is 160 MPa; at the temperature and pressure of the hot isostatic pressing process, it is kept warm for 2 h, and then cooled with the furnace to obtain a printed part after hot isostatic pressing; among them, the heating rate of the printed part to the temperature of the hot isostatic pressing process is 30 °C / min.

[0126] Solution and aging treatment: The printed part after the hot isostatic pressing process is subjected to solution and aging treatment to obtain an additive manufacturing nickel-based superalloy. Among them, the printed part after the hot isostatic pressing process is heated to 1160 °C and subjected to solution treatment for 1 h. After cooling, the printed part after solution treatment is obtained; the printed part after solution treatment is heated to 1080 °C for primary aging treatment for 4 h. After cooling, the printed part after primary aging treatment is obtained; the printed part after primary aging treatment is heated to 850 °C for secondary aging treatment for 24 h. After cooling, the additive manufacturing nickel-based superalloy is obtained; among them, the heating rate is 10 °C / min.

[0127] As Figure 5 shown, the γ' phase in the microstructure of the additive manufacturing nickel-based superalloy obtained in this embodiment includes the first γ' phase, the second γ' phase, and the third γ' phase; among them, the size of the first γ' phase is 1 μm - 3 μm, the size of the second γ' phase is 300 - 400 nm, and the size of the third γ' phase is 30 - 100 nm. The first γ' phase is cubic; the second γ' phase is cubic; the third γ' phase is spherical. And, the volume fraction of the γ' phase in the microstructure of the additive manufacturing nickel-based superalloy is 55 - 60%; among them, in all γ' phases, the volume fraction of the first γ' phase is 5 - 8%, the volume fraction of the second γ' phase is 77 - 85%, and the volume fraction of the third γ' phase is 10 - 15%.

[0128] By conducting tensile property tests on the additive manufacturing nickel-based superalloy prepared in this example, the yield strengths at room temperature and 650 °C were measured. The experimental results are shown in Table 1.

[0129] By conducting creep property tests on the additive manufacturing nickel-based superalloy prepared in this example, the creep life of the alloy under the conditions of 760 °C - 590 MPa was obtained as 178 h.

[0130] Comparative Example 1

[0131] A conventional casting IN738 nickel-based superalloy was prepared in Comparative Example 1. Among them, in terms of weight percentage, the chemical composition of this nickel-based superalloy is as follows:

[0132] Al (3.5 wt%), Ti (3.5 wt%), and the combined content of Al + Ti is 7.0 wt%; Co (8.5 wt%), Cr (16.0 wt%), W (2.6 wt%), Mo (1.7 wt%), and the combined content of Co + Cr + W + Mo is 28.8 wt%, Ta (1.7 wt%), Nb (0.9 wt%), B (0.01 wt%), C (0.1 wt%), Zr (0.05 wt%), and the balance is Ni.

[0133] A nickel-based superalloy ingot was prepared by a conventional method; then the ingot was heat-treated. Among them, the heat treatment is as follows: the nickel-based superalloy ingot was subjected to solution heat treatment at a temperature of 1120 °C for 2 h, and after air cooling, the solution heat-treated nickel-based superalloy was heated to 850 °C for aging heat treatment and held for 24 h, and then air cooled. Among them, the heating rate is 10 °C / min.

[0134] The performance test data of Examples 1 - 3 and Comparative Example 1 are shown in Table 1.

[0135] Table 1

[0136] Room temperature Yield strength MPa Tensile strength MPa Elongation at break % Example 1 922 1387 18 Example 2 1012 1400 17.5 Example 3 1092 1465 10.5 Comparative example 1 880 1030 7.3

[0137] Table 2

[0138] 650℃ Yield strength MPa Tensile strength MPa Elongation at break % Example 1 1063 1285 10.1 Example 2 977 1304 12 Example 3 1061 1338 12.5 Comparative example 1 800 985 8.1

[0139] It can be seen from Table 1 that compared with the conventional as-cast alloy (casting IN738 nickel-based superalloy), the performance of the nickel-based superalloy prepared in the examples of the present invention has been significantly improved, which indicates that the additive manufacturing nickel-based superalloy prepared in this example can reach or even exceed the as-cast level.

[0140] Comparative Example 2

[0141] Comparative Example 2: An additive manufacturing nickel-based superalloy was prepared, which was different from Example 1 in that the chemical composition and heat treatment system of the alloy in Comparative Example 2 were different from those in Example 1, and the others were the same.

[0142] Among them, the chemical composition of the additive manufacturing nickel-based superalloy in Comparative Example 2 was as follows: Al (3.5 wt%), Ti (3.5 wt%), and the combined content of Al + Ti was 7.0 wt%; solid solution strengthening elements Co (8.5 wt%), Cr (16.0 wt%), W (2.6 wt%), and Mo (1.7 wt%), and the combined content of Co + Cr + W + Mo was 28.8 wt%, Ta (1.7 wt%) and Nb (0.9 wt%), elements B (0.01 wt%), C (0.1 wt%), and Zr (0.05 wt%), and the balance was Ni.

[0143] For the microstructure diagram of the printed part prepared in Comparative Example 2, see Figure 6 as shown. From Figure 6 it can be seen that a large number of cracks appeared inside the sample prepared from the components in Comparative Example 2, and the crack sensitivity was relatively large.

[0144] It can be seen from this that using the chemical composition of the as-cast IN738 nickel-based superalloy directly for additive manufacturing will result in cracks.

[0145] Comparative Example 3

[0146] Comparative Example 3: An additive manufacturing nickel-based superalloy was prepared, which was different from Example 1 in that the chemical composition and heat treatment system of the alloy in Comparative Example 3 were different from those in Example 1, and the others were the same.

[0147] Among them, the chemical composition of the nickel-based superalloy in Comparative Example 3 was as follows: Al (3.5 wt%), Ti (3.5 wt%), and the combined content of Al + Ti was 7.0 wt%; solid solution strengthening elements Co (8.5 wt%), Cr (16.0 wt%), W (2.6 wt%), and Mo (1.7 wt%), and the combined content of Co + Cr + W + Mo was 28.8 wt%, Ta (1.7 wt%) and Nb (0.9 wt%), elements B (0.01 wt%), C (0.1 wt%), and Zr (0.05 wt%), and the balance was Ni.

[0148] Among them, the printed part in Comparative Example 3 was not subjected to hot isostatic pressing, and the following heat treatment system was directly carried out: the printed part was heated to 800 °C, stress relief annealing was carried out for 24 h, and air cooling was carried out; then, it was heated to 1170 °C for solution heat treatment for 2 h, and air cooling was carried out; finally, the nickel-based superalloy after solution heat treatment was heated to 750 °C for aging heat treatment and held for 24 h, and air cooling was carried out.

[0149] Figure 7Microstructure diagram of the alloy in Comparative Example 3; among them, Figure 7 Figure (a) in Figure 7 is the microstructure diagram of the printed part prepared in Comparative Example 3, and it can be seen that the printed part has obvious cracks; Figure (b) is the microstructure diagram of the printed part after heat treatment in Comparative Example 3, and it can be seen that: the cracks cannot be eliminated after heat treatment, further aggravating the crack propagation, and the performance drops significantly.

[0150] Comparative Example 4

[0151] An additively manufactured nickel-based superalloy was prepared in Comparative Example 4. The difference from Example 1 is that: the alloy chemical composition and heat treatment system in Comparative Example 4 are different from those in Example 1, and the others are the same.

[0152] Among them, the chemical composition of the nickel-based superalloy in Comparative Example 4 is as follows: Al (3.5 wt%), Ti (3.5 wt%), and the combined content of Al+Ti is 7.0 wt%; solution strengthening elements Co (8.5 wt%), Cr (16.0 wt%), W (2.6 wt%) and Mo (1.7 wt%), and the combined content of Co+Cr+W+Mo is 28.8 wt%, Ta (1.7 wt%) and Nb (0.9 wt%), elements Hf (1 wt%), B (0.01 wt%), C (0.1 wt%) and Zr (0.05 wt%), and the balance is Ni.

[0153] Among them, in Comparative Example 4, the printed part is not subjected to hot isostatic pressing treatment, and the following heat treatment system is directly carried out: the printed part is heated to 1120 °C for solution heat treatment for 2 h, and air-cooled; finally, the nickel-based superalloy after solution heat treatment is heated to 850 °C for aging heat treatment for 24 h, and air-cooled.

[0154] It should be noted here that: although adding 1 wt% of Hf can heal cracks and reduce crack density, the cracks still cannot be completely eliminated (see Figure 8 shown), resulting in performance degradation.

[0155] Comparative Example 5

[0156] An additively manufactured nickel-based superalloy was prepared in Comparative Example 5. The difference from Example 1 is that: the heat treatment system in Comparative Example 5 is different from that in Example 1, and the others are the same.

[0157] Among them, in Comparative Example 5, the printed part is subjected to hot isostatic pressing treatment, and then heated to 1180 °C for solution heat treatment for 2 h, and air-cooled to obtain the printed part after solution treatment; the printed part after solution treatment is heated to 1080 °C for primary aging treatment for 4 h, and after cooling, the printed part after primary aging treatment is obtained; finally, the nickel-based superalloy after solution heat treatment is heated to 850 °C for aging heat treatment for 24 h, and air-cooled.

[0158] Figure 9 Microstructure diagram of the additive manufacturing nickel-based superalloy prepared in Comparative Example 5; wherein, Figure 9 Figure (a) in it is the microstructure diagram of the printed part after heat treatment in Comparative Example 5, and (b) is an enlarged view of Figure (a). It can be seen that: since the solution heat treatment temperature is not within the scope of the present invention, the carbide size after heat treatment increases, and a three-peak γ'-phase cannot be obtained. Instead, a two-peak γ'-phase is obtained (the γ'-phase sizes are mainly two types, one is ≤100 nm, and the other is 300 - 500 nm, and there is no γ'-phase with a size of 1 - 3 microns).

[0159] Figure 11 is the creep performance of the additive manufacturing nickel-based superalloy sample prepared in Example 2 of the present invention compared with other research results. From Figure 11 it can be seen that: Figure 11 The three trend lines in it respectively represent the relationship between stress and LMP of the additive manufacturing IN738 alloy, other superalloys, and as-cast IN738. These trend lines show that as the LMP value increases, the stress gradually decreases, indicating the creep performance of the material at higher temperatures and longer times. The data points of the additive manufacturing nickel-based superalloy sample prepared in Example 2 of the present invention are marked with red pentagrams, which are located in the higher LMP value region of the figure, and its stress value is competitive compared with the data points under other materials and process conditions. This indicates that at the same LMP value, the stress level of the additive manufacturing nickel-based superalloy prepared in the examples of the present invention is higher, meaning that it can still maintain a higher strength under high-temperature and long-time conditions. Therefore, compared with additive manufacturing IN738, other superalloys, and as-cast IN738, the additive manufacturing nickel-based superalloy prepared in the examples of the present invention can still maintain a higher stress level when the LMP value is higher, indicating its advantage in high-temperature creep performance.

[0160] In summary, an additive manufacturing nickel-based superalloy and a preparation method thereof provided by the embodiments of the present invention effectively solve the cracking problem in the additive manufacturing of high crack-sensitivity alloys, and provide a systematic solution for the high internal quality and one-time integral forming of complex structural parts, having important theoretical significance and industrial application value.

[0161] The above are only preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An additive manufacturing nickel-based superalloy, characterized in that, The γ' phases in the microstructure of the additive manufacturing nickel-based superalloy include a first γ' phase, a second γ' phase, and a third γ' phase; wherein, the size of the first γ' phase is 1-3 μm, the size of the second γ' phase is 300-400 nm, and the size of the third γ' phase is 30-100 nm; The density of the additive manufacturing nickel-based superalloy is not less than 99.0%, preferably ≥99.9%; Preferably, there are no cracks inside the additive manufacturing nickel-based superalloy.

2. The additive manufacturing nickel-based superalloy according to claim 1, wherein The first γ' phase is cubic, preferably cube-shaped; the second γ' phase is cubic, preferably cube-shaped; the third γ' phase is spherical; and / or The volume fraction of the γ' phases in the microstructure of the additive manufacturing nickel-based superalloy is 55-60%; wherein, among all the γ' phases, the volume fraction of the first γ' phase is 5-8%, the volume fraction of the second γ' phase is 77-85%, and the volume fraction of the third γ' phase is 10-15%.

3. The additive manufacturing nickel-based superalloy according to claim 1 or 2, characterized in that, By weight percentage, the additive manufacturing superalloy comprises the following chemical components: Cr: 16.0-18.0 wt%, Co: 8.5-10.0 wt%, W: 2.5-4.0 wt%, Ta: 2.0-3.0 wt%, Mo: 2.0-4.0 wt%, Nb: 0.5-2.0 wt%, C: 0.05-0.25 wt%, Zr: 0.01-0.05 wt%, B: 0.001-0.01 wt%, Al: 3.4-3.9 wt%, Ti: 2.9-3.6 wt%, and the balance is Ni; Preferably, by weight percentage, the additive manufacturing superalloy comprises the following chemical components: Cr: 17.0-18.0 wt%, Co: 9.0-10.0 wt%, W: 3.0-4.0 wt%, Ta: 2.0-3.0 wt%, Mo: 2.8-4.0 wt%, Nb: 1.2-2.0 wt%, C: 0.12-0.25 wt%, Zr: 0.01-0.025 wt%, B: 0.001-0.005 wt%, Al: 3.4-3.8 wt%, Ti: 2.9-3.2 wt%, and the balance is Ni.

4. The additive manufacturing nickel-based superalloy according to any one of claims 1-3, characterized in that The yield strength of the additive manufacturing nickel-based superalloy at room temperature > 900 MPa, the fracture strength > 1380 MPa, and the fracture plasticity > 10%; and / or The yield strength of the additive manufacturing nickel-based superalloy at 650 °C > 950 MPa, the fracture strength > 1250 MPa, and the fracture plasticity > 10%.

5. The preparation method of the additive manufacturing nickel-based superalloy according to any one of claims 1-4, characterized in that, The preparation method comprises the following steps: Additive manufacturing treatment: performing additive manufacturing treatment on nickel-based superalloy powder to obtain a printed part; Hot isostatic pressing treatment: performing hot isostatic pressing treatment on the printed part to obtain a printed part after hot isostatic pressing treatment; Solution and aging treatment: performing solution and aging treatment on the printed part after hot isostatic pressing treatment to obtain an additive manufacturing nickel-based superalloy.

6. The preparation method of the additive manufactured nickel-based superalloy according to claim 5, characterized in that, In the step of the additive manufacturing treatment: The selective laser melting (SLM) additive manufacturing process is used to perform additive manufacturing on nickel-based superalloy powder to obtain a printed part. Preferably, the parameters of the selective laser melting (SLM) additive manufacturing process are as follows: the laser power is 150 - 310 W, the scanning speed is 700 - 1300 mm / min, the layer rotation angle is 55 - 80°, the single layer thickness is 0.03 - 0.05 mm, the track spacing is 0.06 - 0.10 mm, and the laser spot diameter is 0.05 - 0.1 mm. Preferably, the protective gas is selected from Ar gas or N2 gas.

7. The preparation method of the additive manufacturing nickel-based superalloy according to claim 5, characterized in that, In the step of hot isostatic pressing treatment: The temperature of the hot isostatic pressing treatment is 1160 - 1200 °C, and the pressure of the hot isostatic pressing treatment is 150 - 180 MPa. At the temperature and pressure of the hot isostatic pressing treatment, keep warm for 2 - 4 h, and then cool to obtain the printed part after hot isostatic pressing treatment. Preferably, the cooling method is furnace cooling. Preferably, the heating rate for heating the printed part to the temperature of the hot isostatic pressing treatment is 20 - 30 °C / min.

8. The preparation method of the additively manufactured nickel-based superalloy according to claim 5, characterized in that, In the step of solution treatment and aging treatment: Heat the printed part after hot isostatic pressing treatment to 1120 - 1160 °C, perform solution treatment for 1 - 3 h, and after cooling, obtain the printed part after solution treatment. Heat the printed part after solution treatment to 1040 - 1100 °C for primary aging treatment for 2 - 8 h, and after cooling, obtain the printed part after primary aging treatment. Heat the printed part after primary aging treatment to 850 - 900 °C for secondary aging treatment for 15 - 30 h, and after cooling, obtain the additive manufactured nickel-based superalloy. Preferably, the cooling method is air cooling. Preferably, the heating rate is 5 - 15 °C / min.

9. The preparation method of the additively manufactured nickel-based superalloy according to claim 5, wherein, Before the additive manufacturing treatment step, the following steps are further included: Design a preset chemical composition range: According to the influence of the elements of the superalloy on cracks, determine the content ranges of the solid solution strengthening elements W, Mo, Co, Cr, Nb, Ta and the grain boundary strengthening elements C, B, Zr, and design the ranges of Al and Ti through thermodynamic software to obtain the preset chemical composition range of the nickel-based superalloy. Experimental screening: Screen the required chemical composition of the nickel-based superalloy and the optimal process parameters for additive manufacturing treatment. Preferably, in the step of experimental screening: First, use thermodynamic simulation software to evaluate the effects of different elements on the solidification temperature range and low-melting-point phases of the alloy to determine the elements that help narrow the solidification temperature range and reduce the formation of low-melting-point phases; Subsequently, in combination with the strengthening effect of solid solution elements, increase the solid solution elements to improve the solid solution strength of the superalloy matrix; Then, determine the optimal content of age-hardening elements based on the strain aging sensitivity to ensure the high-temperature stability of the alloy; At the same time, in order to inhibit cracks, when selecting process parameters, internal residual stress and Hall-Petch grain boundary strengthening effect need to be considered, and process parameters that can refine the grain size and reduce residual stress are selected; Finally, screen by analyzing the results of thermodynamic calculation experiments and high-throughput experimental data to determine the required chemical composition of the nickel-based superalloy and the optimal process parameters for additive manufacturing treatment; Preferably, by weight percentage, the preset chemical composition range includes: Cr: 14 - 18.0 wt%, Co: 7 - 10.0 wt%, W: 1.5 - 4.0 wt%, Ta: 0.5 - 3.0 wt%, Mo: 1.0 - 4.0 wt%, Nb: 0.1 - 2.0 wt%, C: 0 - 0.025 wt%, Zr: 0 - 0.10 wt%, B: 0 - 0.03 wt%, Al: 2.0 - 5.0 wt%, Ti: 2.0 - 4.5 wt%, and the balance is Ni; Preferably, the selected additive manufacturing superalloy required includes the following chemical composition: Cr: 16.0 - 18.0 wt%, Co: 8.5 - 10.0 wt%, W: 2.5 - 4.0 wt%, Ta: 2.0 - 3.0 wt%, Mo: 2.0 - 4.0 wt%, Nb: 0.5 - 2.0 wt%, C: 0.05 - 0.25 wt%, Zr: 0.01 - 0.05 wt%, B: 0.001 - 0.01 wt%, Al: 3.4 - 3.9 wt%, Ti: 2.9 - 3.6 wt%, and the balance is Ni; Preferably, Cr: 17.0 - 18.0 wt%, Co: 9.0 - 10.0 wt%, W: 3.0 - 4.0 wt%, Ta: 2.0 - 3.0 wt%, Mo: 2.8 - 4.0 wt%, Nb: 1.2 - 2.0 wt%, C: 0.12 - 0.25 wt%, Zr: 0.01 - 0.025 wt%, B: 0.001 - 0.005 wt%, Al: 3.4 - 3.8 wt%, Ti: 2.9 - 3.2 wt%, and the balance is Ni; Preferably, in the step of experimental screening: based on the preset chemical composition range of the nickel-based superalloy, multiple groups of nickel-based superalloy compositions are designed, and multiple groups of alloy powders are prepared; using a selective laser melting printing device, multiple groups of alloy powders are respectively printed on a substrate to obtain samples corresponding to multiple groups of process parameters; the printed samples are analyzed for cracks and pores, the cracks and pores are quantitatively counted, the selected printing process window is obtained, and the samples are observed through the microstructure to exclude the chemical composition range that causes cracks, and the chemical composition range corresponding to the crack-free samples is screened out to obtain the chemical composition of the required nickel-based superalloy.

10. The preparation method of the additively manufactured nickel-based superalloy according to claim 5, characterized in that, Before the step of hot isostatic pressing treatment, a heat treatment design step is further included; wherein, the heat treatment design step further includes: Step 1) Formulate the hot isostatic pressing treatment and process parameter range According to the structural characteristics of the printed part, hot isostatic pressing treatment is selected for the printed part to eliminate the holes and cracks inside the printed part and improve the density and mechanical properties of the material; Determine the remelting temperature of γ′ and the transformation temperature of the precipitation phase of the additive manufacturing superalloy required, and determine the process parameters of the hot isostatic pressing treatment to avoid primary melting; Step 2) Design the solution treatment and aging treatment system Design the process parameters of the solution treatment and aging treatment system so that the microstructure of the additive manufacturing nickel-based superalloy after aging treatment includes three sizes of γ′ phases, specifically the first γ′ phase, the second γ′ phase, and the third γ′ phase; among them, the size of the first γ′ phase is 1-3 μm, the size of the second γ′ phase is 300-400 nm, and the size of the third γ′ phase is 30-100 nm.

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