Method for improving resistance of nickel-based superalloy to oxygen-rich combustion and nickel-based superalloy

Abstract

The present application belongs to the technical field of nickel-based superalloy, and discloses a method for improving the oxygen-enriched combustion resistance of a nickel-based superalloy and the nickel-based superalloy. The nickel-based superalloy is prepared by using a nickel-based superalloy powder as a raw material and sequentially performing additive manufacturing, solid solution treatment and aging treatment. The printing direction of the additive manufacturing is controlled so that the grain boundary morphology of the nickel-based superalloy is perpendicular to the flow direction of high-temperature and high-pressure oxygen-enriched combustion gas. The high-temperature and high-pressure oxygen-enriched combustion gas is combustion gas with a temperature of ≥500 DEG C, a pressure of ≥3.5 MPa and an oxygen concentration of >90%. The grain boundary morphology of the nickel-based superalloy is perpendicular to the flow direction of the high-temperature and high-pressure oxygen-enriched combustion gas, and the oxygen-enriched combustion resistance of the nickel-based superalloy is improved.

Description

Technical Field

[0001] This invention belongs to the field of nickel-based superalloy technology, and more specifically, relates to a method for improving the oxygen-rich combustion resistance of nickel-based superalloys and a nickel-based superalloy. Background Technology

[0002] As engine thrust increases, materials face severe challenges. Nickel-based superalloys must endure extremely harsh working environments characterized by high temperature, high pressure, oxygen-rich conditions, and high loads. This makes superalloy materials prone to a combustion phenomenon similar to that of wood or nylon, known as metal combustion. This metal combustion phenomenon is often accompanied by a rapid increase in temperature, flame formation, volume reduction, and violent heat release, severely limiting the operating temperature of superalloy materials.

[0003] Currently, the preparation of high-temperature alloy parts through additive manufacturing processes is becoming increasingly mature. Using additive manufacturing technology, it is possible to achieve lightweight and integrated design and manufacturing of structures, as well as the overall manufacturing of internal flow channel structures in hot-end components such as combustion chambers, thereby improving product performance and reliability, shortening manufacturing cycles, and reducing manufacturing costs.

[0004] Additive manufacturing technology, due to its high cooling rate and strong temperature gradient directionality, promotes dendrite growth along... <100> Crystalline growth leads to directional solidification, resulting in anisotropic material properties, with the anisotropy of the microstructure depending on the structural orientation. Grain boundaries, possessing lower melting points and serving as rapid diffusion channels for elements, are crucial factors influencing element diffusion. The number and anisotropy of grain boundaries in a material both affect its combustion performance. Therefore, to further improve the oxygen-enriched combustion resistance of high-temperature alloy parts fabricated using additive manufacturing processes, a novel method for enhancing the oxygen-enriched combustion resistance of nickel-based high-temperature alloys needs to be developed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method and a nickel-based superalloy for improving its resistance to oxygen-enriched combustion. This invention aligns the grain boundary morphology of the nickel-based superalloy with the flow direction of high-temperature, high-pressure, oxygen-enriched combustion gases, thereby enhancing its resistance to oxygen-enriched combustion.

[0006] To achieve the above objectives, the present invention provides a method for improving the resistance of nickel-based superalloys to oxygen-rich combustion. The method includes: using nickel-based superalloy powder as raw material, sequentially performing additive manufacturing, solution treatment, and aging treatment to obtain the nickel-based superalloy; and controlling the printing direction of the additive manufacturing to make the grain boundary morphology of the nickel-based superalloy perpendicular to the flow direction of the high-temperature, high-pressure, oxygen-rich combustion gas. The high-temperature, high-pressure, oxygen-enriched gas is a gas with a temperature ≥500℃, a pressure ≥3.5MPa, and an oxygen concentration >90%.

[0007] In this invention, the printing direction of additive manufacturing is the same as the layer-by-layer growth direction of the printed alloy. Therefore, the printing direction of additive manufacturing determines the direction in which the columnar crystals grow, and thus determines the grain boundary morphology. This invention controls the printing direction of additive manufacturing to be perpendicular to the flow direction of high-temperature, high-pressure, oxygen-rich gas, so that the grain boundary morphology of the nickel-based high-temperature alloy of this invention is perpendicular to the flow direction of high-temperature, high-pressure, oxygen-rich gas.

[0008] In this invention, the combustion characteristics of metallic materials under high temperature, high pressure, and oxygen-rich environments are related to grain boundaries within the material. Grain boundaries, acting as high-speed diffusion channels for elements, have relatively low melting points and diffusion activation energies. During combustion, grain boundaries preferentially melt, thereby promoting the diffusion of combustible elements into the fusion zone. Differences in grain morphology inevitably affect the diffusion path of elements. Compared to grain boundaries parallel to the combustion direction, grain boundaries perpendicular to the combustion direction hinder the diffusion and reaction pathways of flammable elements. Figure 2 Therefore, by optimizing the printing strategy so that the grain boundary morphology is perpendicular to the combustion direction, the present invention can improve the material's resistance to oxygen-rich combustion.

[0009] According to the present invention, preferably, the nickel-based high-temperature alloy powder needs to undergo vacuum drying and sieving treatment in sequence before being subjected to the additive manufacturing process.

[0010] According to the present invention, preferably, the operating conditions for the vacuum drying process include: temperature 120-150℃ and time 4-8h.

[0011] In this invention, the equipment used for the vacuum drying process is a vacuum drying oven. The purpose of the vacuum drying process is to remove the moisture and a small amount of hydrogen adsorbed by the powder, prevent the formation of pores and hydrogen-induced cracks during printing, and avoid the increase of oxygen content.

[0012] According to the present invention, preferably, the nominal particle size range of the nickel-based superalloy powder after the sieving process is 8-50 μm (the particle size distribution of the powder is tested using a Malvern laser particle size analyzer).

[0013] In this invention, the sieving process is carried out by using a vibrating screen or an air classifier to separate and remove satellite powder, agglomerated powder, oversized particles, and abnormal particles generated during the printing process, as well as those caused by splashing and oxidation, to ensure uniform powder spreading and stable flowability.

[0014] According to the present invention, preferably, the additive manufacturing operation parameters include: under a protective atmosphere, a preset temperature of 70-150°C in the forming chamber, an initial powder thickness of 30-80μm, a laser rotation angle between adjacent layers of 65-70°, preferably 67°, a laser power of 180-320W, a laser scanning speed of 800-1200mm / s, and a laser scanning spacing of 0.08-0.12mm.

[0015] According to the present invention, preferably, the solution treatment includes: placing the additively manufactured material into a muffle furnace that has undergone a first heat treatment, and holding the additively manufactured material at 1075-1085°C for 0.8-1.2 hours, followed by air cooling to 15-30°C; The muffle furnace that has undergone the first heat preservation treatment is a muffle furnace that has been kept at 1075-1085℃ for 1.5-2.5 hours.

[0016] In this invention, air cooling refers to the process of placing the alloy sample in the air and allowing it to cool slowly and naturally to 15-30°C.

[0017] According to the present invention, preferably, the aging treatment includes: placing the solution-treated material into a muffle furnace that has undergone a second heat treatment, so that the solution-treated material is first heat-treated at 710-730°C for 7.5-8.5 hours, and then heat-treated at 610-630°C for 7.5-8.5 hours before air cooling to 15-30°C; The muffle furnace that has undergone the second heat preservation treatment is a muffle furnace that has been kept at 710-730℃ for 1.5-2.5 hours.

[0018] In this invention, the process of cooling from 710-730℃ to 610-630℃ is furnace cooling, and the cooling rate is 55℃ / h.

[0019] In this invention, as a preferred embodiment, the method for improving the resistance of nickel-based superalloys to oxygen-rich combustion includes the following steps: (1) The nickel-based superalloy powder is pretreated (vacuum drying and sieving) to obtain pretreated nickel-based superalloy powder; (2) Using pretreated nickel-based high-temperature alloy powder, an alloy sample is printed by additive manufacturing equipment, ensuring that the printing direction of the additive manufacturing is perpendicular to the flow direction of the high-temperature, high-pressure, oxygen-rich gas (i.e., the alloy combustion direction). (3) The additive manufacturing material is subjected to solution treatment and aging treatment in sequence to obtain a nickel-based high-temperature alloy with grain boundary morphology perpendicular to the flow direction of high-temperature, high-pressure, oxygen-rich gas.

[0020] In this invention, the additively manufactured material, after heat treatment (solution treatment and aging treatment), yields a nickel-based superalloy with grain boundary morphology and matrix structure as follows: Figure 3 , Figure 4 As shown: like Figure 3 It can be seen that the alloy sample of the present invention is composed of columnar grains arranged parallel to the construction direction, and the grain boundaries are perpendicular to the alloy combustion direction; like Figure 4It can be seen that a large number of nanoscale spherical reinforcing phases (γ′ / γ′′ reinforcing phases) are precipitated within the grains, and a small amount of blocky carbides (MC) and δ phases are retained at the grain boundaries. A small amount of Laves phases that were not completely dissolved during the heat treatment process can also be observed. Through the heat treatment process, the low-melting-point Laves phase in the deposited state can be eliminated as much as possible, and the γ′ / γ′′ reinforcing phases can be fully precipitated.

[0021] According to the present invention, preferably, the average grain size of the nickel-based superalloy is 8-35 μm and the grain aspect ratio is 0.1-0.6.

[0022] According to the present invention, preferably, the nickel-based superalloy is at least one of the following: a nickel-based superalloy for a liquid oxygen-kerosene rocket engine turbopump, a nickel-based superalloy for a liquid oxygen-kerosene rocket engine gas pipeline, and a nickel-based superalloy for a liquid oxygen-kerosene rocket engine turbine spherical shell. Therefore, the direction of high-temperature, high-pressure, oxygen-rich gas flow (i.e., the alloy combustion direction) faced by the nickel-based superalloy prepared by the present invention is fixed and definite.

[0023] According to the present invention, preferably, the nickel-based superalloy is at least one of GH4022, GH4169 and GH4061.

[0024] According to the present invention, preferably, when the diameter of the nickel-based superalloy is 3.15-3.20 mm and the height is ≥110 mm, the combustion pressure threshold under the conditions of 15-30 °C and oxygen concentration >99.5% is 5.2 MPa.

[0025] Another aspect of the present invention provides a nickel-based superalloy obtained by the method described above for improving the oxygen-rich combustion resistance of nickel-based superalloys.

[0026] The beneficial effects of the technical solution of the present invention are as follows: This invention utilizes additive manufacturing technology to prepare alloy samples with anisotropic characteristics and optimizes the printing strategy to make the grain boundary morphology of nickel-based superalloys perpendicular to the flow direction of high-temperature, high-pressure, oxygen-rich gas (i.e., the alloy combustion direction). This can improve the combustion pressure threshold of nickel-based superalloys. Specifically, the method of this invention increases the combustion pressure threshold (the oxygen pressure in the container during oxygen-rich combustion testing, which measures the oxygen pressure at which the material will ignite) of nickel-based superalloys (diameter 3.15-3.20 mm, height ≥ 110 mm) under room temperature (15-30℃) and pure oxygen (oxygen concentration > 99.5%) conditions from 4.7 MPa to 5.2 MPa.

[0027] This invention utilizes the characteristic that grain boundaries perpendicular to the combustion direction can hinder the diffusion and reaction pathways of flammable elements, thereby improving the oxygen-enriched ablation resistance of nickel-based superalloys and significantly enhancing their safety and flame-retardant properties in high-temperature, high-pressure, and oxygen-enriched environments.

[0028] The method of this invention optimizes the printing strategy (controlling the printing direction of the additive manufacturing) so that the grain boundary morphology of the prepared alloy is perpendicular to the combustion direction. It has the characteristics of mature process, promoting lightweighting and integration, applicable to a variety of complex parts, enabling large-scale production to shorten the production cycle and reduce production costs. Therefore, it can be widely promoted and applied.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0030] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0031] Figure 1 The diagram shows the printing direction and alloy combustion direction of Embodiment 1 and Comparative Example 1 of the present invention.

[0032] Figure 2 A schematic diagram illustrating the mechanism by which this invention improves the resistance of nickel-based superalloys to oxygen-rich combustion is shown.

[0033] Figure 3 The image shows an electron backscatter diffraction (EBSD) image of a nickel-based superalloy prepared by a method for improving the oxygen-rich combustion resistance of nickel-based superalloys according to Embodiment 1 of the present invention.

[0034] Figure 4 The image shown is a scanning electron microscope (SEM) image of a nickel-based superalloy prepared by a method for improving the oxygen-rich combustion resistance of nickel-based superalloys according to Embodiment 1 of the present invention.

[0035] Figure 5 The test results of the alloy test samples corresponding to Embodiment 1 and Comparative Example 1 of the present invention in the test example are shown (burning length, "x, y, z" represent coordinate axes).

[0036] Figure 6 The test results (combustion rate) of the alloy test samples corresponding to Example 1 and Comparative Example 1 of the present invention in the test example are shown.

[0037] Figure 7 The image shows the post-combustion morphology of the alloy test sample corresponding to Example 1 of the present invention during the test example of oxygen-enriched combustion performance testing ("3mm" is the scale).

[0038] Figure 8 The image shows the post-combustion morphology of the alloy test sample corresponding to Comparative Example 1 of the present invention after the oxygen-enriched combustion performance test in the test example ("3mm" is the scale). Detailed Implementation

[0039] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0040] In the following examples and comparative examples: The EOS M290 Selective Laser Melting (SLM) system includes a fiber laser with a maximum power of 400W, an argon gas protection device, a computer numerical control module, and an automatic powder spreading system. The forming chamber measures 250mm × 250mm × 325mm and is equipped with a focusing optical system with a focal plane spot diameter of 100μm.

[0041] Example 1

[0042] This embodiment provides a method for improving the oxygen-enriched combustion resistance of nickel-based superalloy (GH4169), the method comprising the following steps: (1) Place GH4169 nickel-based high-temperature alloy powder into a vacuum drying oven and vacuum dry it at 130°C for 8 hours to remove the moisture adsorbed by the powder and obtain dry powder.

[0043] (2) The dried powder was sieved using a vibrating screen to separate and remove satellite powder, agglomerated powder, oversized particles and abnormal particles that may be generated during the printing process, to obtain pretreated nickel-based high-temperature alloy powder. The average particle size was measured to be about 20.14 μm (the particle size distribution of the powder was tested using a Malvern laser particle size analyzer).

[0044] (3) The flow direction of the high-temperature, high-pressure, oxygen-rich gas (the high-temperature, high-pressure, oxygen-rich gas is gas with a temperature ≥ 500℃, pressure ≥ 3.5MPa, and oxygen concentration > 90%) facing the nickel-based superalloy prepared in this embodiment (i.e., the alloy combustion direction) is fixed and determined; the printing direction in this embodiment is designed according to the flow direction of the high-temperature, high-pressure, oxygen-rich gas facing the alloy to ensure that the printing direction is perpendicular to the alloy combustion direction, thereby ensuring that the grain boundary morphology of the nickel-based superalloy prepared in this embodiment is perpendicular to the flow direction of the high-temperature, high-pressure, oxygen-rich gas; the sample printed in this embodiment is a columnar alloy sample (e.g. Figure 1 ), specifically: Before printing, the stainless steel substrate is surface polished and ultrasonically cleaned with anhydrous ethanol for 10 minutes. Then it is placed in the forming chamber of the EOSM290 selective laser melting (SLM) system (i.e. the additive manufacturing equipment used in this embodiment) and the forming chamber is preheated to reach the preset temperature of 80°C. Argon gas with a purity of ≥99.99% is introduced into the forming chamber as a protective gas, and the flow rate of the protective gas is controlled at 6L / min. After the oxygen content in the chamber is ≤50ppm, the SLM forming process is started. The initial powder thickness was 50 μm (then 30 μm thick powder layers were laid layer by layer by a powder spreading roller), the laser rotation angle between adjacent layers was 67°, the laser power was 285W, the laser scanning speed was 960 mm / s, and the laser scanning spacing was 0.11 mm.

[0045] (4) Heat the muffle furnace to 1080°C and keep it at that temperature for 2 hours to obtain a muffle furnace that has undergone the first heat treatment; put the additive manufacturing material into the muffle furnace that has undergone the first heat treatment, and keep the additive manufacturing material at 1080°C for 1 hour and then air cool it to 25°C to complete the solution treatment.

[0046] (5) The muffle furnace is heated to 720℃ and held for 2 hours to obtain a muffle furnace after the second holding treatment; the solution-treated material is placed in the muffle furnace after the second holding treatment, and the solution-treated material is first held at 720℃ for 8 hours, then held at 620℃ for 8 hours and then air-cooled to 25℃ to complete the aging treatment, resulting in a nickel-based superalloy with grain boundary morphology perpendicular to the flow direction of the high-temperature, high-pressure, oxygen-rich gas, with an average grain size of 21.87±12.13μm and a grain aspect ratio of 0.35±0.21, as shown. Figure 2 , Figure 4 As shown, the grain boundaries in the alloy are perpendicular to the direction of alloy combustion. A large number of nanoscale spherical strengthening phases (γ′ / γ′′ strengthening phases) are precipitated in the grains. A small amount of blocky carbides (MC) and δ phase are retained at the grain boundaries. A small amount of Laves phase that was not completely dissolved during the heat treatment process can also be observed.

[0047] Comparative Example 1

[0048] The only difference between this comparative example and Example 1 is that: The printing direction of this comparative example is designed based on the flow direction of the high-temperature, high-pressure, oxygen-rich gas facing the alloy surface, ensuring that the printing direction is parallel to the combustion direction of the alloy, thereby ensuring that the grain boundary morphology of the nickel-based high-temperature alloy prepared in this comparative example is parallel to the flow direction of the high-temperature, high-pressure, oxygen-rich gas.

[0049] Test case

[0050] The columnar nickel-based superalloys obtained in Example 1 and Comparative Example 1 had a diameter of 16 mm and a height of 120 mm. Through wire cutting and centerless grinding, alloy test samples with a diameter of 3.20 mm and a height of 120 mm were obtained.

[0051] This test example examines the oxygen-enriched combustion resistance of the alloy test samples corresponding to Example 1 and Comparative Example 1 using the accelerated ignition method (PIC method). The test procedure is as follows: (1) Measure the size of the test sample, add a combustion enhancer to one end of the test sample, wrap a NiCr resistance wire around the outside of the combustion enhancer, and connect the positive and negative poles of the ignition electrode to the two ends of the resistance wire; (2) The test sample is suspended inside the combustion pressure vessel and the vessel is sealed; (3) First, clean the combustion pressure vessel with high-pressure pure oxygen and purge the air inside the vessel; the cleaning process is as follows: pressurize to 3.5MPa and then release the air to 0.1MPa; repeat this process three times. (4) High-pressure oxygen is injected into the combustion pressure vessel and the predetermined test oxygen pressure is reached; (5) Start the DC power supply of the ignition system, use the large current to ignite the NiCr resistance wire and the combustion aid, the combustion aid drives the test sample to burn, and the high temperature molten droplets of the combustion reaction fall into the ceramic receiving cup. (6) Start the high-speed camera to film the combustion process; (7) After the test sample stops burning, turn off the DC power supply, open the vent valve, and when the pressure inside the pressure vessel drops to 0.1 MPa, open the pressure vessel, take out the test sample and measure its remaining length.

[0052] The conditions for the oxygen-enriched combustion resistance test include: test temperature at room temperature (25°C), test environment oxygen concentration >99.5%, and test oxygen pressures of 3.5, 4.5, 5, 5.5, and 6 MPa, respectively.

[0053] Depend on Figure 5 It can be known that: The combustion pressure threshold of the alloy sample in Comparative Example 1, whose grain boundary morphology is parallel to the combustion direction, is 4.7 MPa. The combustion pressure threshold of the alloy sample with grain boundary morphology perpendicular to the combustion direction in Example 1 was 5.2 MPa; Therefore, it can be seen that by optimizing the printing strategy, the present invention makes the grain boundary morphology perpendicular to the combustion direction, thereby significantly improving the oxygen-rich combustion resistance of the prepared high-temperature alloy material.

[0054] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for improving the resistance of nickel-based superalloys to oxygen-rich combustion, characterized in that, The method includes: using nickel-based superalloy powder as raw material, sequentially performing additive manufacturing, solution treatment, and aging treatment to obtain a nickel-based superalloy; and controlling the printing direction of the additive manufacturing to make the grain boundary morphology of the nickel-based superalloy perpendicular to the flow direction of the high-temperature, high-pressure, oxygen-rich gas. The high-temperature, high-pressure, oxygen-enriched gas is a gas with a temperature ≥500℃, a pressure ≥3.5MPa, and an oxygen concentration >90%. When the diameter of the nickel-based superalloy is 3.15-3.20 mm and the height is ≥110 mm, the combustion pressure threshold under the conditions of 15-30℃ and oxygen concentration >99.5% is 5.2 MPa.

2. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, Before the nickel-based high-temperature alloy powder is subjected to the additive manufacturing process, it must undergo vacuum drying and sieving in sequence. The operating conditions for the vacuum drying process include: temperature 120-150℃, time 4-8h; The nominal particle size range of the nickel-based superalloy powder after the sieving process is 8-50 μm.

3. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, The additive manufacturing operating parameters include: under a protective atmosphere, a pre-set temperature of 70-150℃ in the forming chamber, an initial powder thickness of 30-80μm, a laser rotation angle of 65-70° between adjacent layers, a laser power of 180-320W, a laser scanning speed of 800-1200mm / s, and a laser scanning spacing of 0.08-0.12mm.

4. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, The solution treatment includes: placing the additively manufactured material into a muffle furnace that has undergone a first heat treatment, and then air-cooling the additively manufactured material to 15-30°C after holding it at 1075-1085°C for 0.8-1.2 hours. The muffle furnace that has undergone the first heat preservation treatment is a muffle furnace that has been kept at 1075-1085℃ for 1.5-2.5 hours.

5. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, The aging process includes: placing the solution-treated material into a muffle furnace that has undergone a second heat treatment, and then holding the solution-treated material at 710-730℃ for 7.5-8.5 hours, and then holding it at 610-630℃ for 7.5-8.5 hours before air cooling to 15-30℃. The muffle furnace that has undergone the second heat preservation treatment is a muffle furnace that has been kept at 710-730℃ for 1.5-2.5 hours.

6. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, The average grain size of the nickel-based superalloy is 8-35 μm, and the grain aspect ratio is 0.1-0.

6.

7. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 1, wherein, The nickel-based superalloy is at least one of the following: nickel-based superalloy for liquid oxygen-kerosene rocket engine turbopump, nickel-based superalloy for liquid oxygen-kerosene rocket engine gas pipeline, and nickel-based superalloy for liquid oxygen-kerosene rocket engine turbine spherical shell.

8. The method for improving the resistance to oxygen-rich combustion of nickel-based superalloys according to claim 7, wherein, The nickel-based superalloy is at least one of GH4022, GH4169 and GH4061.

9. The nickel-based superalloy obtained by the method for improving the oxygen-rich combustion resistance of nickel-based superalloys according to any one of claims 1-8.

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