A nickel-based cast superalloy and its preparation method

Abstract

The application provides a nickel-based cast high-temperature alloy and a preparation method thereof, wherein the chemical composition of the nickel-based cast high-temperature alloy is as follows: 0.12wt%-0.15wt% of C, 18.5wt%-21.5wt% of Cr, 10wt%-18wt% of Co, 2.5wt%-4.5wt% of W, 1.5wt%-3.0wt% of Mo, 1.5wt%-3.0wt% of Al, 3.2wt%-4.0wt% of Ti, 1.3wt%-2.5wt% of Nb, 0.010wt%-0.013wt% of B, Zr≤0.1wt%, and the balance of Ni. The nickel-based cast high-temperature alloy has good mechanical properties, microstructure stability and process performance, and can be used for preparing large thin-walled complex structure hot end structural parts.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy technology, specifically relating to a nickel-based cast high-temperature alloy and its preparation method. Background Technology

[0002] High-temperature alloys, with their excellent high-temperature mechanical properties, have become an important metallic structural material in the development of the aerospace industry worldwide. These materials can operate stably for extended periods under high-temperature conditions, reliably withstanding the combined effects of complex stress, oxidation, corrosion, and other harsh conditions. They are widely used in critical hot-end components of aero-engines, such as combustion chambers, turbine disks, blades, and casings. With the development of aerospace technology, the performance requirements for engine materials are becoming increasingly demanding, leading to a gradual increase in the types and contents of alloying elements in high-temperature alloys. High alloying increases the strength and reduces the plasticity of high-temperature alloys, significantly increasing their resistance to deformation. This has led to the development of cast high-temperature alloys based on wrought high-temperature alloys. Cast high-temperature alloys can be used for the precise casting of complex structural components.

[0003] Currently, K4169 alloy is the most widely used polycrystalline casting high-temperature alloy in my country. However, the maximum service temperature of K4169 alloy is 650℃. Using K4169 alloy above this temperature will cause significant microstructural degradation, making it highly susceptible to hot cracking within the allowable stress range of components, thus jeopardizing their operational safety. While some existing high-alloy nickel-based casting high-temperature alloys can meet the requirements for high-temperature strength, they generally have poor weldability and cannot meet the requirements for welding and repairing casting defects in complex thin-walled castings.

[0004] In summary, there is an urgent need to develop new types of high-temperature cast alloys with higher operating temperatures, good casting and welding properties, and the ability to meet the precision forming requirements of complex hot-end components. Summary of the Invention

[0005] In view of this, the present invention provides a nickel-based cast high-temperature alloy and its preparation method, the main purpose of which is to increase the service temperature of the nickel-based cast high-temperature alloy to 750-850℃, while having good casting and welding properties, so as to meet the precision forming requirements of complex hot-end components.

[0006] On the one hand, in order to achieve the above objectives, the present invention provides a nickel-based cast superalloy, wherein the chemical composition of the nickel-based cast superalloy, by weight percentage, is as follows:

[0007] 0.12 wt% < C < 0.15 wt%, 18.5 wt% < Cr < 21.5 wt%, 10 wt% < Co < 18 wt%, 2.5 wt% < W < 4.5 wt%, 1.5 wt% < Mo < 3.0 wt%, 1.5 wt% < Al < 3.0 wt%, 3.2 wt% < Ti < 4.0 wt%, 1.3 wt% < Nb < 2.5 wt%, 0.010 wt% < B < 0.013 wt%, Zr ≤ 0.1 wt%, and the balance is Ni.

[0008] Preferably, in the nickel-based cast superalloy: S ≤ 0.0015 wt%, O ≤ 0.0015 wt%, N ≤ 0.0050 wt%.

[0009] Preferably, the room temperature tensile strength R m ≥ 1050 MPa, the room temperature tensile yield strength R p0.2 ≥ 850 MPa, and the elongation after fracture at room temperature A ≥ 5%.

[0010] Preferably, the tensile strength R of the nickel-based cast superalloy under the condition of 800 °C m ≥ 820 MPa, the tensile yield strength R p0.2 ≥ 700 MPa, and the elongation after fracture at room temperature A ≥ 2%.

[0011] Preferably, the nickel-based cast superalloy has a creep life τ ≥ 50 h under the conditions of 870 - 900 °C and 225 - 250 MPa.

[0012] Preferably, the nickel-based cast superalloy does not precipitate harmful phases during long-term aging up to 1500 h under the condition of 800 - 850 °C.

[0013] Preferably, the nickel-based cast superalloy can achieve the casting and defect repair welding of ultra-thin wall castings with a thickness of 1.0 - 2.0 mm.

[0014] Preferably, the nickel-based cast superalloy has a two-stage or multi-stage γ' phase precipitation state and a granular or rod-shaped MC carbide precipitation morphology in the grains (there are no other types of carbides except MC carbides); at the grain boundaries, there is a multi-stage size γ' phase and M 23 C6 carbide interphase precipitation strengthening state; preferably, there are also near-equiaxed MC carbides at the grain boundaries (there is no precipitation morphology of long strips along the grain boundaries). Here, MC is prone to cracking, and if it precipitates in a long strip shape at the grain boundaries, it is very easy to cause grain boundary cracks.

[0015] On the other hand, the embodiments of the present invention provide a preparation method for the nickel-based cast superalloy described in any one of the above, which includes the following steps:

[0016] Remelting and casting steps of master alloy: Remelt the master alloy, and after the alloy is liquefied and cleared, pour the alloy liquid into the mold at a temperature of 1400-1500℃. After cooling, perform shell cleaning treatment to obtain nickel-based casting high-temperature alloy.

[0017] Preferably, the remelting and casting of the master alloy is carried out in a vacuum induction casting furnace.

[0018] Preferably, the method further includes a shell preheating step; wherein the shell preheating step includes: treating the shell with heat-insulating fixtures; heating the heat-insulating shell to 850-1000℃ and holding it at that temperature for 2-6 hours for preheating treatment; after preheating treatment, transferring the heat-insulating shell to a casting furnace for alloy liquid casting treatment; preferably, the heat-insulating fixture treatment includes wrapping with heat-insulating cotton or filling with sand. Preferably, the shell preheating step is carried out in a muffle furnace. The shell is prepared using investment casting to ensure good MC carbide precipitation morphology in the alloy, with MC carbides in granular or rod-shaped forms within the grains and a near-equiaxed morphology at grain boundaries; there are no elongated morphologies distributed along the grains.

[0019] Preferably, after the remelting and casting process of the master alloy, the method further includes:

[0020] Heat treatment steps: The nickel-based cast superalloy is heat-treated to obtain the heat-treated nickel-based cast superalloy.

[0021] Preferably, the heat treatment step includes solution treatment and multi-stage aging treatment, so that the alloy can obtain a bilevel or multi-level γ′ phase precipitation state within the grains, and multi-level γ′ phase and M phase at the grain boundaries. 23 The interphase precipitation strengthening state of C6 carbides improves the strength-ductility balance of the alloy.

[0022] Preferably, the solution treatment temperature is not lower than 1180°C, and air cooling is used.

[0023] Preferably, the multi-stage aging process includes a first-stage aging process, a second-stage aging process, and a third-stage aging process performed sequentially; wherein, the temperature of the first-stage aging process is 1030-1080℃, and the time of the first-stage aging process does not exceed 4 hours; the temperature of the second-stage aging process is 810-850℃, and the time of the second-stage aging process is not less than 12 hours; the temperature of the third-stage aging process is 700-750℃, and the time of the third-stage aging process is not less than 12 hours; preferably, air cooling is used after each stage of aging process.

[0024] Compared with the prior art, the nickel-based cast superalloy and its preparation method of the present invention have at least the following beneficial effects:

[0025] The present invention provides a nickel-based cast superalloy and a preparation method thereof. In terms of weight percentage, the chemical composition of the nickel-based cast superalloy is as follows: 0.12 wt% < C < 0.15 wt%, 18.5 wt% < Cr < 21.5 wt%, 10 wt% < Co < 18 wt%, 2.5 wt% < W < 4.5 wt%, 1.5 wt% < Mo < 3.0 wt%, 1.5 wt% < Al < 3.0 wt%, 3.2 wt% < Ti < 4.0 wt%, 1.3 wt% < Nb < 2.5 wt%, 0.010 wt% < B < 0.013 wt%, Zr ≤ 0.1 wt%, and Ni is the balance. Regarding the above design of the alloy chemical composition, the following explanations are provided: (1) The C element has an important influence on the formation of carbides in the alloy. Here, the present invention controls the content of the C element and, at the same time, coordinates the addition and control of the Ti, Nb, and Cr elements in the alloy, so that the alloy can precipitate MC carbides with good stability, and at the same time, fine M 23 C6 carbides are formed in a semi-continuous state at the grain boundaries, while improving the intragranular and grain boundary strengths of the alloy. (2) The Cr element is the main corrosion-resistant element of the alloy described in the present invention. The present invention selects a lower Cr content on the basis of maintaining sufficient corrosion resistance of the alloy to optimize M 23C6 carbide precipitation morphology to improve grain boundary strength, while inhibiting the precipitation of harmful phases and improving microstructure stability. (3) Co, W, and Mo are important solid solution strengthening elements of the alloy described in this invention. They can improve the strength of the alloy by generating short-range lattice distortion stress field, promoting the precipitation of γ′ phase, and reducing the stacking fault energy of the alloy; however, excessive addition of Co, W, and Mo elements will lead to the precipitation of harmful phases such as σ phase, μ phase, and P phase, as well as unstable carbide phases. The reasonable design of the Co, W, and Mo element content in this invention is one of the key points for the alloy described in this invention to have excellent strength-microstructure stability matching. (4) Al, Ti, and Nb are important precipitation strengthening elements of the alloy described in this invention. Their content has a key influence on the precipitation amount of γ′ phase and the effect of hindering dislocation movement, and can significantly affect the strength of the alloy. In addition, the addition of Nb element can improve the stability of MC carbide, inhibit its decomposition during long-term service, and help improve the microstructure stability of the alloy. The Ti / Al ratio is one of the key microstructure stability indicators of high-temperature alloys, which is related to whether the alloy is prone to precipitating the harmful η phase. The γ′ phase has a significant impact on the weldability of the alloy; generally, as the γ′ phase content increases, the weldability of the alloy deteriorates. Therefore, the content of Al, Ti, and Nb elements, as well as their relative content, are key factors in achieving the excellent strength-structure stability-weldability balance of the alloy described in this invention. (5) B and Zr elements are grain boundary strengthening elements; reasonable control of their content can enable the alloy described in this invention to obtain good grain boundary strength and casting performance. In summary, this invention, through the above composition design, increases the service temperature of nickel-based casting high-temperature alloys to 750-850℃, while also possessing good casting and welding performance, to meet the precision forming requirements of complex hot-end components.

[0026] Furthermore, the mechanical properties of the alloy described in this invention are significantly affected by the solidification structure. Equiaxed grain structures with moderate grain size exhibit a better strength-ductility balance compared to other solidification structures. MC carbides are mainly formed during the alloy's solidification process, and their size and morphology are unaffected by subsequent heat treatment. This invention helps improve alloy properties by reducing the casting and shell temperatures to obtain fine MC carbide precipitation morphologies; however, excessively low casting and shell temperatures increase the tendency for solidification defects such as shrinkage cavities and porosity to form in the alloy. Therefore, rationally designing the alloy's casting and shell temperatures is crucial; a good solidification crystal structure and primary MC carbide precipitation morphology are the foundation and guarantee for the alloy to possess good mechanical properties.

[0027] Furthermore, grain boundaries are generally weak points in high-temperature alloys during high-temperature service environments. To improve the grain boundary strength of the alloy described in this invention, this invention controls the M of the alloy by precisely designing the C and Cr content. 23 C6 carbide precipitation behavior, M 23During the main aging treatment of the alloy described in this invention (the aging temperature is close to the alloy's service temperature), C6 carbides are dispersed and precipitated at the grain boundaries with appropriate size and granular morphology. Furthermore, this invention also finely controls the γ′ phase and M by synergistically controlling the content of Al, Ti, and Nb elements. 23 The precipitation temperature difference of C6 carbides, achieved through multi-step aging treatment, is determined at M... 23 Before, during, and after the precipitation of C6 carbides, γ′ phases of different sizes form at the grain boundaries. These gradient-sized γ′ phases interact with M... 23 The interspersed C6 phase significantly increases the number density of precipitated phases at the grain boundaries of the alloy, effectively improving the strength and plasticity of the alloy. Attached Figure Description

[0028] Figure 1 The grain boundary microstructure of the heat-treated alloy prepared in Comparative Example 1 is shown.

[0029] Figure 2 The low-magnification and high-magnification grain boundary microstructures of the heat-treated alloy prepared in Example 2;

[0030] Figure 3 The actual casting thin-walled annular part prepared in Example 3;

[0031] Figure 4 The actual casting thin-walled annular part prepared for Comparative Example 3;

[0032] Figure 5 The macroscopic morphology and X-ray flaw detection results of the cast test plate prepared in Example 4 after welding;

[0033] Figure 6 The results are from X-ray inspection of a certain alloy after sealing welding using existing technology. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The purpose of this invention is to provide a nickel-based cast superalloy and its preparation method. Compared with existing similar alloys, the solution of this invention increases the service temperature of the nickel-based cast superalloy to 750-850℃, while also exhibiting good casting and welding properties.

[0036] The technical solution adopted by the present invention is as follows:

[0037] On the one hand, the present invention provides a nickel-based cast superalloy. By weight percentage, the chemical composition of the alloy is as follows:

[0038] 0.12 wt% < C < 0.15 wt%, 18.5 wt% < Cr < 21.5 wt%, 10 wt% < Co < 18 wt%, 2.5 wt% < W < 4.5 wt%, 1.5 wt% < Mo < 3.0 wt%, 1.5 wt% < Al < 3.0 wt%, 3.2 wt% < Ti < 4.0 wt%, 1.3 wt% < Nb < 2.5 wt%, 0.010 wt% < B < 0.013 wt%, Zr ≤ 0.1 wt%, and the balance is Ni.

[0039] In the chemical composition of the alloy, S ≤ 0.0015 wt%, O ≤ 0.0015 wt%, and N ≤ 0.0050 wt%.

[0040] On the other hand, an embodiment of the present invention provides a preparation method for a nickel-based cast superalloy, which includes the following steps:

[0041] Step of preparing the mold shell: The mold shell of the workpiece is prepared by the investment precision casting method; the mold shell is subjected to heat preservation tooling treatment; the mold shell after the heat preservation tooling treatment is placed in a muffle furnace, heated to 850 - 1000 °C with the furnace, and kept warm for 2 - 6 h. After the heat preservation is completed, it is directly and quickly transferred to a vacuum induction casting furnace.

[0042] Steps of remelting and pouring the master alloy: The master alloy is remelted in a vacuum induction casting furnace with a capacity of 10 kg - 25 kg. After melting and clearing, the alloy liquid is poured into the mold shell at 1400 - 1500 °C, and the mold shell is air-cooled outside the furnace in a sand box. After the sand box is cooled to room temperature, the shell cleaning treatment is carried out to obtain the nickel-based cast superalloy.

[0043] The obtained nickel-based cast superalloy is subjected to heat treatment of "solution treatment + multi-stage aging treatment" to obtain a multi-stage size γ' phase + M 23 interphase precipitation strengthening state of C6 carbide, improving the strength-plasticity matching of the alloy.

[0044] The nickel-based cast superalloy provided by the present invention has good mechanical properties, tissue stability and process performance. It can meet the following mechanical property requirements:

[0045] Room temperature tensile R m ≥ 1050 MPa, R p0.2 ≥ 850 MPa, A ≥ 5%; 800 °C tensile R m ≥ 820 MPa, R p0.2≥700MPa, A≥2%; high temperature creep aging at 870℃ / 255MPa, creep life τ≥50h. No harmful phases precipitate during long-term aging at 850℃ for up to 1500h; enables perfect casting and defect repair welding of 1.0-2.0mm ultra-thin wall castings.

[0046] Furthermore, regarding the chemical composition design of the nickel-based cast superalloy of the present invention, the design principle of the present invention is as follows:

[0047] C element has a significant impact on carbide formation in the alloy. Combined with the addition of Ti, Nb, and Cr elements, the alloy can precipitate stable MC carbides, while simultaneously forming fine M particles distributed in a semi-continuous state at the grain boundaries. 23 C6 carbides simultaneously improve the intragranular and grain boundary strength of the alloy.

[0048] Cr is the main corrosion-resistant element in the alloy described in this invention. Considering the application environment of the alloy described in this invention, a lower Cr content is selected while maintaining sufficient corrosion resistance, and M is optimized. 23 C6 carbide precipitation morphology improves grain boundary strength while inhibiting the precipitation of harmful phases and enhancing microstructure stability.

[0049] Co, W, and Mo are important solid solution strengthening elements in the alloy described in this invention. They can improve the alloy strength by generating a short-range lattice distortion stress field, promoting the precipitation of the γ′ phase, and reducing the alloy stacking fault energy. However, excessive addition of Co, W, and Mo can lead to the precipitation of harmful phases such as the σ phase, μ phase, and P phase. Appropriately designing the content of Co, W, and Mo is one of the key points to achieving an excellent strength-microstructure stability balance in the alloy described in this invention.

[0050] Al, Ti, and Nb are important precipitation strengthening elements in the alloy described in this invention. Their contents have a crucial impact on the precipitation amount of the γ′ phase and its effect on hindering dislocation movement, significantly affecting the alloy's strength. Furthermore, the addition of Nb can improve the stability of MC carbides, inhibiting their decomposition during long-term service and contributing to improved alloy microstructure stability. The Ti / Al ratio is one of the key microstructure stability indicators of high-temperature alloys, relating to whether the alloy is prone to precipitating the harmful η phase. The γ′ phase has a significant impact on weldability; generally, an increase in the γ′ phase content leads to a deterioration in weldability. Therefore, the contents of Al, Ti, and Nb, and their relative contents, are key factors in achieving an excellent balance of strength, microstructure stability, and weldability in the alloy described in this invention.

[0051] B and Zr are grain boundary strengthening elements. Properly controlling their content can enable the alloy described in this invention to achieve good grain boundary strength and casting properties. To ensure good mechanical properties, the S, O, and N content of the alloy should be strictly controlled, with S ≤ 15 ppm, O ≤ 15 ppm, and N ≤ 50 ppm.

[0052] The mechanical properties of the alloy described in this invention are significantly affected by the solidification structure. Equiaxed grain structures with moderate grain size exhibit a better strength-ductility balance compared to other solidification structures. MC carbides are mainly formed during the alloy's solidification process, and their size and morphology are unaffected by subsequent heat treatment. Lowering the casting and shell temperatures helps to obtain fine MC carbide precipitation morphologies, thus improving alloy properties. However, excessively low casting and shell temperatures increase the tendency for solidification defects such as shrinkage cavities and porosity to form in the alloy. Therefore, rationally designing the casting and shell temperatures is crucial; a good solidification crystal structure and primary MC carbide precipitation morphology are the foundation and guarantee for the alloy to possess good mechanical properties.

[0053] Grain boundaries are generally weak points in high-temperature alloys during high-temperature service environments. To improve the grain boundary strength of the alloy described in this invention, the invention controls the M (grain boundary strength) of the alloy by precisely designing the C and Cr content. 23 C6 precipitation behavior. This causes M to... 23 During the main aging treatment of the alloy described in this invention (the aging temperature is close to the alloy's service temperature), C6 carbides are dispersed and precipitated at the grain boundaries with appropriate size and granular morphology. Furthermore, this invention also finely controls the γ′ phase and M by synergistically controlling the content of Al, Ti, and Nb elements. 23 The precipitation temperature difference of C6 carbides. Through multi-step aging treatment, precipitation occurs at M... 23 Before, during, and after the precipitation of C6 carbides, γ′ phases of different sizes form at the grain boundaries. These gradient-sized γ′ phases interact with M... 23 The interspersed C6 phase significantly increases the number density of precipitated phases at the grain boundaries of the alloy, effectively improving the strength and plasticity of the alloy.

[0054] The present invention will be further illustrated below through specific experimental examples:

[0055] This invention provides a solution-and-aging nickel-based cast high-temperature alloy containing solid solution strengthening elements of Cr, Co, W, and Mo, and aging strengthening elements of Al, Ti, and Nb.

[0056] The novel alloy proposed in this invention is batched according to its alloy composition, melted in a vacuum induction melting furnace, and cast into master alloy bars with a diameter of 75-95mm. Alloy test bars, plates, or castings are then produced using investment casting to test the alloy's mechanical properties, weldability, and casting properties.

[0057] Example 1

[0058] In this embodiment, a nickel-based cast high-temperature alloy test bar was prepared, and the chemical composition of the nickel-based cast high-temperature alloy test bar is shown in Table 1.

[0059] Table 1. Alloy chemical composition (wt%) of Example 1

[0060] C Cr Co W Mo Al Ti Nb B Zr S O N Ni 0.13 19.2 11.0 2.7 1.7 2.26 3.55 1.75 0.011 0.01 <0.0005 0.0004 <0.0003 margin

[0061] The preparation method in this embodiment mainly includes the following steps:

[0062] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition is shown in Table 1.

[0063] Preparation steps of the mold shell: The mold shell is prepared by investment casting; the mold shell is kept warm by filling with sand; the investment casting mold shell sand box is placed in a muffle furnace and heated to 950±10℃ with the furnace, and kept warm for 4 hours for preheating treatment. After the preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0064] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at a casting temperature of (1400~1500)±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain a nickel-based cast high-temperature alloy test bar.

[0065] Heat treatment: The alloy test bar was subjected to heat treatment of “(1180℃±10℃)×4h×air cooling+(1060℃±10℃)×4h×air cooling+(840℃±10℃)×16h×air cooling+(725℃±10℃)×16h×air cooling” to obtain the heat-treated nickel-based cast high-temperature alloy test bar.

[0066] The mechanical properties of the nickel-based cast high-temperature alloy test bar prepared in this embodiment were tested, and the performance data are shown in Table 2.

[0067] Comparative Example 1

[0068] Comparative Example 1 prepared a nickel-based cast high-temperature alloy test bar, the chemical composition of which is shown in Table 1.

[0069] The preparation method of Comparative Example 1 mainly includes the following steps:

[0070] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition is shown in Table 1.

[0071] Preparation steps of the mold shell: The mold shell is prepared by investment casting; the mold shell is kept warm by filling with sand; the investment casting mold shell sand box is placed in a muffle furnace and heated to 1050±10℃ with the furnace, and kept warm for 4 hours for preheating treatment; after preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0072] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at 1430±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain nickel-based cast high-temperature alloy test bars.

[0073] Heat treatment: The alloy test bar was subjected to heat treatment of “(1180℃±10℃)×4h×air cooling+(1060℃±10℃)×4h×air cooling+(840℃±10℃)×16h×air cooling+(725℃±10℃)×16h×air cooling” to obtain the heat-treated nickel-based cast high-temperature alloy test bar.

[0074] The mechanical properties of the nickel-based cast high-temperature alloy test bar prepared in Comparative Example 1 were tested, and the performance data are shown in Table 2.

[0075] Table 2 shows the room temperature tensile mechanical properties of the alloy test bars prepared in Example 1 and Comparative Example 1.

[0076]

[0077] A comparison of Example 1 and Comparative Example 1 shows that the casting process has a significant impact on the mechanical properties of the alloy. In Comparative Example 1, the shell temperature was too high (high preheating temperature), resulting in the presence of large and intergranular elongated primary MC carbides (such as...) in the solidification structure. Figure 1 As shown in the figure, this significantly reduces the strength and plasticity of the cast alloy.

[0078] Example 2

[0079] In this embodiment, a nickel-based cast high-temperature alloy test bar was prepared, and the chemical composition of the nickel-based cast high-temperature alloy test bar is shown in Table 3.

[0080] The preparation method in this embodiment mainly includes the following steps:

[0081] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition is shown in Table 3.

[0082] Shell preparation steps: The shell is prepared by investment casting; the shell is kept warm by filling with sand; the investment casting shell sand box is placed in a muffle furnace and heated to 950±10℃ with the furnace, and kept warm for 4 hours for preheating treatment. After the heat preservation is completed, it is directly and quickly transferred to a vacuum induction casting furnace.

[0083] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at a casting temperature of 1430±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain nickel-based cast high-temperature alloy test bars.

[0084] Heat treatment: The alloy test bar was subjected to heat treatment of “(1180℃±10℃)×4h×air cooling+(1060℃±10℃)×4h×air cooling+(840℃±10℃)×16h×air cooling+(725℃±10℃)×16h×air cooling” to obtain the heat-treated nickel-based cast high-temperature alloy test bar.

[0085] The mechanical properties of the nickel-based cast superalloy test rods prepared in this embodiment were tested, and the performance data are shown in Table 4. The grain boundary microstructure morphology of the heat-treated nickel-based cast superalloy test rods in this embodiment is shown in Table 4. Figure 2 As shown, multi-level γ′ phases precipitate within the alloy grains, and the MC carbides are granular with small precipitate sizes; no other types of carbides are present. At the grain boundaries, multi-level γ′ phases and M phases are formed. 23 The C6 carbide exhibits a phase-enhanced precipitation state, while the MC carbide at the grain boundaries shows a good precipitation state with no intergranular strip-shaped precipitation.

[0086] Table 3 shows the alloy chemical composition (wt%) of Example 2 and Comparative Example 2.

[0087]

[0088] Comparative Example 2

[0089] Comparative Example 2 prepared a nickel-based cast high-temperature alloy test bar, the chemical composition of which is shown in Table 3.

[0090] The preparation method of Comparative Example 2 mainly includes the following steps:

[0091] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition is shown in Table 3.

[0092] Preparation steps of the mold shell: The mold shell is prepared by investment casting; the mold shell is kept warm by filling with sand; the investment casting mold shell sand box is placed in a muffle furnace and heated to 950±10℃ with the furnace, and kept warm for 4 hours for preheating. After the heat preservation is completed, it is directly and quickly transferred to a vacuum induction casting furnace.

[0093] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at 1430±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain nickel-based cast high-temperature alloy test bars.

[0094] Heat treatment: The alloy test bar was subjected to heat treatment of “(1180℃±10℃)×4h×air cooling+(1060℃±10℃)×4h×air cooling+(840℃±10℃)×16h×air cooling+(725℃±10℃)×16h×air cooling” to obtain the heat-treated nickel-based cast high-temperature alloy test bar.

[0095] The mechanical properties of the nickel-based cast high-temperature alloy test bar prepared in Comparative Example 2 were tested, and the performance data are shown in Table 4.

[0096] Table 4. High-temperature tensile mechanical properties of the alloy test bars prepared in Example 2 and Comparative Example 2.

[0097]

[0098] Comparing Example 2 with Comparative Example 2, it is shown that chemical composition also has a significant impact on the mechanical properties of the alloy. When the tensile temperature of Example 2 was increased from 800℃ to 820℃, the strength of the alloy did not decrease significantly, while the strength of the alloy in Comparative Example 2 decreased significantly at 820℃.

[0099] It should be noted that the chemical composition of the alloy in Example 2 conforms to the design of this invention. The content of C, Cr, Co, W, and Mo in the alloy is higher than that in Comparative Example 2 alloy. Without increasing the content of γ′ phase-forming elements, the alloy strength is improved by utilizing solid solution strengthening elements and carbide-forming elements. The alloy preparation method described in this invention, combined with increasing the content of C and Cr elements, promotes M... 23 The intercalation of C6 carbides with γ′ at grain boundaries enhances the grain boundary strength of the alloy. The solid solution strengthening effects of Cr, Co, W, and Mo improve the basic strength of the alloy. The dissolution temperature of the γ′ phase is increased by utilizing Co, W, and Mo, thereby improving the high-temperature strength of the alloy. Furthermore, Co, W, and Mo promote the formation of stacking faults during plastic deformation, inhibit dislocation cross-slip, and enhance the interaction between the γ′ phase and dislocations. The combined effects of these improvements, along with the enhanced alloy composition, result in the alloy in Example 2 exhibiting superior high-temperature mechanical properties.

[0100] Example 3

[0101] This embodiment prepares a cast thin-walled annular component with the same chemical composition as in Example 2. The thin-walled annular component has an inner and outer ring structure, with an outer ring diameter of 250 mm, an inner ring diameter of 135 mm, a height of 60 mm, and inner ring blades with a wall thickness of approximately 1 mm.

[0102] The preparation method in this embodiment mainly includes the following steps:

[0103] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition was the same as in Example 2.

[0104] Shell preparation steps: The shell is prepared by investment casting; the shell is insulated by wrapping it with insulating cotton; the investment casting shell sand box is placed in a muffle furnace and heated to 1000±10℃ with the furnace, and held for 4 hours for preheating treatment; after the preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0105] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into the mold shell at a casting temperature of 1430±10℃. The mold shell is air-cooled outside the furnace while wrapped with insulation cotton. After cooling to room temperature, the shell is cleaned to obtain a cast thin-walled ring part.

[0106] like Figure 3 As shown, the thin-walled annular part prepared in this embodiment is well formed, and no solidification defects such as surface cracks, porosity, or shrinkage cavities are observed.

[0107] Comparative Example 3

[0108] Comparative Example 3 prepared a cast thin-walled annular component with the same chemical composition as Comparative Example 2. The thin-walled annular component has an inner and outer ring structure, with an outer ring diameter of 250 mm, an inner ring diameter of 135 mm, a height of 60 mm, and inner ring blades with a wall thickness of approximately 1 mm.

[0109] The preparation method of Comparative Example 3 mainly includes the following steps:

[0110] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and its specific chemical composition was the same as that of Comparative Example 2.

[0111] Shell preparation steps: The shell is prepared by investment casting; the shell is insulated by wrapping it with insulating cotton; the investment casting shell sand box is placed in a muffle furnace and heated to 1000±10℃ with the furnace, and held at that temperature for 4 hours for preheating treatment; after preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0112] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into the mold shell at a casting temperature of 1430±10℃. The mold shell is air-cooled outside the furnace while wrapped with insulation cotton. After cooling to room temperature, the shell is cleaned to obtain a cast thin-walled ring part.

[0113] The thin-walled annular part prepared in this embodiment has good overall forming, but there are unfilled defects in the thin-walled area, and a small number of pore defects exist on the surface of the casting, such as... Figure 4 As shown.

[0114] A comparison between Example 3 and Comparative Example 3 demonstrates that alloy composition has a significant impact on the forming quality of thin-walled ring-shaped parts with complex structures. Compared to Comparative Example 3, the alloy in Example 3 has higher C and B contents. Appropriately increasing the C and B content helps improve the melt flowability of the alloy, enhances its casting properties, and reduces the formation of defects such as porosity and voids.

[0115] Example 4

[0116] In this embodiment, a 3mm thick nickel-based cast high-temperature alloy test plate was prepared, with the same chemical composition as in Example 1.

[0117] The preparation method in this embodiment mainly includes the following steps:

[0118] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition was the same as in Example 1.

[0119] Shell preparation steps: The shell is prepared by investment casting; the shell is kept warm by filling with sand; the investment casting shell sand box is placed in a muffle furnace and heated to 950±10℃ with the furnace, and kept warm for 4 hours for preheating treatment; after preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0120] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at a casting temperature of 1430±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain a nickel-based cast high-temperature alloy test plate.

[0121] Various welding wires were used to perform 7mm diameter hole sealing welding and butt welding on the nickel-based cast superalloy test plate prepared in this embodiment. X-ray inspection was performed after welding. The results showed that common commercial welding wires are not suitable for the superalloy material described in this invention, and cracks appeared after hole sealing welding. Special welding wires for nickel-based superalloy materials achieved good hole sealing welding and butt welding results, with no welding cracks observed. Figure 5 As shown.

[0122] Specialized welding wires have a chemical composition similar to the base alloy. Based on the base alloy, the content of γ′-forming elements and easily segregating elements is appropriately adjusted to ensure good welding results. In contrast, when using existing technology to perform sealing welding on a certain existing alloy of the same type, without the availability of alloy-specific welding wire, good welding cannot be achieved regardless of whether the same type of welding wire or 263 welding wire is used. Figure 6 As shown.

[0123] Comparative Example 4

[0124] In this comparative example, a K4169 nickel-based cast high-temperature alloy test bar was prepared, and the chemical composition of the alloy test bar is shown in Table 1.

[0125] Table 5. Alloy chemical composition (wt%) of Comparative Example 4

[0126] C Cr Ni Mo Al Ti Nb Mn Si S O N Fe 0.06 19.5 52.5 3.1 0.5 1.0 4.9 0.02 0.02 <0.0005 0.0005 0.001 margin

[0127] The preparation method of this comparative example mainly includes the following steps:

[0128] Preparation of master alloy: The master alloy was smelted in a vacuum induction furnace, and the specific chemical composition is shown in Table 5.

[0129] Preparation steps of the mold shell: The mold shell is prepared by investment casting; the mold shell is kept warm by filling with sand; the investment casting mold shell sand box is placed in a muffle furnace and heated to 900±10℃ with the furnace, and kept warm for 4 hours for preheating treatment. After the preheating treatment, it is directly and quickly transferred to a vacuum induction casting furnace.

[0130] Master alloy remelting and casting steps: The master alloy is remelted in a vacuum induction casting furnace. After remelting and cleaning, the molten alloy is poured into a mold shell at a casting temperature of (1400~1500)±10℃. The mold shell is air-cooled outside the furnace in a sand box. After the sand box cools to room temperature, the shell is cleaned to obtain a nickel-based cast high-temperature alloy test bar.

[0131] Heat treatment: The alloy test bar was subjected to heat treatment of “(1100℃±10℃)×2h×air cooling+(950℃±10℃)×2h×air cooling+(720℃±10℃)×8h×furnace cooling (55℃ / h) to 620℃+(620℃±10℃)×8h×air cooling” to obtain the heat-treated nickel-based cast high-temperature alloy test bar.

[0132] The mechanical properties of the nickel-based cast superalloy test bar prepared in this comparative example were tested, and the performance data are shown in Table 6. It can be seen that the mechanical properties of the K4169 alloy (especially under high-temperature conditions) are significantly lower than those of the alloy described in this invention.

[0133] Table 6. High-temperature tensile mechanical properties of the alloy specimens prepared in Comparative Example 4

[0134]

[0135] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A nickel-based cast high-temperature alloy, characterized in that, The chemical composition of the nickel-based cast high-temperature alloy is as follows in terms of weight percentage: 0.12wt%<C<0.15wt%, 18.5wt%<Cr<21.5wt%, 10wt%<Co<18wt%, 2.5wt%<W<4.5wt%, 1.5wt%<Mo<3.0wt%, 1.5wt%<Al<3.0wt%, 3.2wt%<Ti<4.0wt%, 1.3wt%<Nb<2.5wt%, 0.010wt%<B<0.013wt%, Zr≤0.1wt%, and the balance of Ni; The nickel-based cast high-temperature alloy has a dual-stage or multi-stage γ' phase precipitation state, a granular or rod-shaped MC carbide precipitation morphology in the grain; and a multi-stage size γ' phase and M 23 intergranular precipitation strengthening state of C6 carbide.

2. The nickel-base cast superalloy of claim 1, wherein, In the nickel-based cast high-temperature alloy: S≤0.0015wt%, O≤0.0015wt%, and N≤0.0050wt%.

3. The nickel-based cast high-temperature alloy according to claim 1, wherein: The nickel-based cast high-temperature alloy has a room temperature tensile strength R m ≥ 1050 MPa, a room temperature tensile yield strength R p0.2 ≥ 850 MPa, a room temperature elongation A ≥ 5%; and / or The nickel-based cast high-temperature alloy has a tensile strength R m ≥ 820 MPa, a tensile yield strength R p0.2 ≥ 700 MPa, a room temperature elongation A ≥ 2%; and / or the nickel-based cast high-temperature alloy has a creep rupture life τ≥50h under the conditions of 870-900℃ and 225-250MPa; and / or the nickel-based cast high-temperature alloy does not precipitate harmful phases in long-term aging for up to 1500h under the condition of 800-850℃; and / or the nickel-based cast high-temperature alloy can realize cast forming and defect repair welding of 1.0-2.0mm ultra-thin wall castings.

4. The nickel-base cast superalloy of claim 1, wherein, The nickel-based cast high-temperature alloy has near-equiaxed MC carbides at grain boundaries.

5. The method of producing a nickel-based cast superalloy according to any one of claims 1 to 4, characterized in that, It comprises the following steps: a master alloy remelting and casting step: remelting the master alloy, after the alloy is liquefied and cleaned, pouring the alloy liquid into a mold shell at a temperature of 1400-1500℃, and after cooling, performing shell cleaning treatment to obtain the nickel-based cast high-temperature alloy; a heat treatment step: heat treating the nickel-based cast high-temperature alloy to obtain the heat-treated nickel-based cast high-temperature alloy; The heat treatment step includes solid solution treatment and multi-stage aging treatment, so that the alloy can obtain a dual-stage or multi-stage γ' phase precipitation state in the crystal, a multi-stage size γ' phase and M 23 The intergranular precipitation strengthening state of C6 carbide is obtained, so that the strength and plasticity matching of the alloy is improved. wherein the temperature of the solid solution treatment is not less than 1180℃, and the cooling mode is air cooling; wherein the multi-stage aging treatment comprises sequentially performing a first-stage aging treatment, a second-stage aging treatment, and a third-stage aging treatment; wherein the temperature of the first-stage aging treatment is 1030-1080℃, and the time of the first-stage aging treatment is not more than 4h; the temperature of the second-stage aging treatment is 810-850℃, and the time of the second-stage aging treatment is not less than 12h; and the temperature of the third-stage aging treatment is 700-750℃, and the time of the third-stage aging treatment is not less than 12h.

6. The method of producing a nickel-based cast superalloy according to claim 5, characterized in that, The master alloy remelting and casting treatment is performed in a vacuum induction casting furnace.

7. The method of producing a nickel-based cast superalloy according to claim 5, characterized in that, The method further comprises a mold shell preheating step; wherein the mold shell preheating step comprises: performing heat preservation tooling treatment on the mold shell, heating the mold shell after the heat preservation tooling treatment to 850-1000℃, and preserving for 2-6h for preheating treatment; after the preheating treatment, transferring the mold shell after the heat preservation tooling treatment to a casting furnace for alloy liquid pouring treatment.

8. The method of producing a nickel-based cast superalloy according to claim 7, characterized in that, The mold shell preheating step is performed in a muffle furnace.

9. The method of producing a nickel-based cast superalloy according to claim 7, characterized in that, The heat preservation tooling treatment mode comprises a heat preservation cotton wrapping mode or a sand filling mode.

10. The method of producing a nickel-based cast superalloy according to claim 5, wherein Each stage of aging treatment adopts air cooling.

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