Weldable and castable high-specific-strength Ni3Al-based alloy, preparation method thereof and alloy part

Abstract

The invention relates to the technical field of nickel-based alloys, in particular to a weldable and castable high-specific-strength Ni3Al-based alloy, a preparation method of the weldable and castable high-specific-strength Ni3Al-based alloy and an alloy part. The weldable and castable high-specific-strength Ni3Al-based alloy comprises the following components in percentage by mass: 5.5%-9.5% of Al, 5%-15% of Cr, 0.01%-0.2% of C, 9%-15% of Fe, 1%-8% of Mo + W, 0.1%-3.5% of Ti, 0.005%-0.08% of B, 0.2%-2% of Hf and the balance of Ni and inevitable impurities. Elements such as Fe, Al, Ti, Cr, Mo, W and Hf are adopted, the material design bottleneck that the total mass fraction of Al and Ti in a nickel-based alloy exceeds 6% and cannot be welded is broken through, and the obtained alloy has light specific gravity, excellent mechanical property and oxidation resistance and good welding manufacturability and castability and meets the development requirement of a new generation of aero-engines.

Description

Technical Field

[0001] The present invention relates to the technical field of nickel-based alloys, in particular to a weldable and castable high-specific-strength Ni3Al-based alloy, a preparation method thereof, and alloy components. Background Art

[0002] Weldability is a key property of cast superalloys, directly impacting their application range and service reliability. Good weldability not only allows castings to be repaired through repair welding, improving yield and reducing manufacturing costs, but many components require structural welding for connection, placing even stricter demands on the alloy's weldability. Existing technology indicates that alloys with a combined Al and Ti mass fraction exceeding 6% are difficult to weld. While most wrought superalloys with low Al and Ti contents can be fusion welded, their low γ′-strengthening phase content leads to poor thermal stability, typically initiating rapid remelting above 900°C, resulting in a sharp decline in mechanical properties above 900°C. While most cast superalloys exhibit good mechanical properties, their high Al and Ti contents result in poor or even unweldable weldability. The development of new-generation aircraft engines is driving increasing demands for component weight reduction and high-temperature resistance. Hot-end components operate at temperatures exceeding 900°C and even approaching 1100°C. Furthermore, to minimize weight, component designs are becoming highly integrated and complex, transforming multiple components into a single, large, and complex component. This presents significant casting challenges and places higher demands on the material's casting processability. However, existing weldable materials suffer from high specific gravity, poor temperature resistance, insufficient strength, poor castability, and high cost. Therefore, there is an urgent need to develop a new high-temperature structural material that is lightweight, has high specific strength, and exhibits excellent weldability and castability, capable of serving at temperatures between 900 and 1100°C.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide a weldable and castable high-specific-strength Ni3Al-based alloy, a preparation method thereof, and alloy components. The Ni3Al-based alloy of the present invention can be stably used in the range of 900 to 1100°C, while being lightweight, having high specific strength, and having good welding and casting properties.

[0005] In order to achieve the above-mentioned object of the present invention, the first aspect of the present invention provides a weldable and castable high specific strength Ni3Al-based alloy, which comprises, by mass percentage: Al 5.5%~9.5%, Cr 5%~15%, C 0.01%~0.2%, Fe 9%~15%, Mo+W 1%~8%, Ti 0.1%~3.5%, B 0.005%~0.08%, Hf 0.2%~2%, and the balance is Ni and unavoidable impurities.

[0006] In a specific embodiment of the present invention, the Ni3Al-based alloy does not contain at least one of Ta, Zr, Co, and Si. Further, the Ni3Al-based alloy does not contain Ta, Zr, Co, and Si.

[0007] In a specific embodiment of the present invention, the mass percentage ratio of Fe element to Al element in the Ni3Al-based alloy is Fe / Al≤2.3. Further, the mass percentage ratio of Fe element to Al element in the Ni3Al-based alloy is Fe / Al in the range of 1 to 2.3.

[0008] In a specific embodiment of the present invention, in the Ni3Al-based alloy, the mass percentage ratio of Ti element to Al element is Ti / Al≤0.5.

[0009] In a specific embodiment of the present invention, the Ni3Al-based alloy includes a γ′ phase, a γ phase, a carbide phase, and a β phase (NiAl phase). Furthermore, in the Ni3Al-based alloy, the γ′ phase content is ≥50%, the β phase content is ≤20%, and the carbide phase content is 0.1% to 5%.

[0010] The second aspect of the present invention provides a method for preparing the weldable and castable high specific strength Ni3Al-based alloy of the first aspect, comprising the following steps: The components of the weldable and castable high specific strength Ni3Al-based alloy according to the first aspect of the present invention are prepared, vacuum induction melted, and then cast.

[0011] In a specific embodiment of the present invention, the vacuum induction melting includes: mixing materials according to the alloy composition, placing electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten, and graphite in a crucible, and adding other elements from a hopper; after the materials in the crucible are completely melted, refining begins; after the refining is completed, cooling to a temperature close to the solidified shell and adding metallic aluminum, after melting, adding metallic titanium and ferroboron, after melting, adding argon gas and adding hafnium sponge, stirring evenly, and pouring when the molten steel temperature is controlled at 1400-1480°C.

[0012] The third aspect of the present invention provides an alloy component, which is mainly made of the weldable and castable high specific strength Ni3Al-based alloy according to the first aspect of the present invention.

[0013] In a specific embodiment of the present invention, the tensile strength of the alloy component at 900°C is ≥600 MPa; the tensile strength of the alloy component at 1000°C is ≥350 MPa; and the tensile strength of the alloy component at 1100°C is ≥120 MPa.

[0014] In a specific embodiment of the present invention, the alloy component has a durability of ≥100 h under the conditions of 1090° C. / 27 MPa.

[0015] In a specific embodiment of the present invention, the density of the alloy component is ≤8g / cm 3 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts Fe, Al, Ti, Cr, Mo, W, Hf and other elements, breaking through the material design bottleneck of nickel-based alloys that cannot be welded when the total mass fraction of Al and Ti exceeds 6%. The obtained Ni3Al-based alloy has light specific gravity, excellent mechanical properties, good welding processability and castability, meeting the development needs of the new generation of aircraft engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 The as-cast optical microstructure of the Ni3Al-based alloy provided in Example 2 of the present invention; Figure 2 Appearance (a) and peeling condition (b) of the Ni3Al-based alloy sample after oxidation at 1100°C for 100 hours provided in Example 2 of the present invention; Figure 3 X-ray image (a) and metallographic structure (b) of the fusion weld of the Ni3Al-based alloy provided in Example 2 of the present invention; Figure 4 This is an X-ray image of the fusion weld of the Ni3Al-based alloy body provided in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0019] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0020] As aircraft engine component designs trend toward integrated, lightweight, hollow, and thin-walled designs with high structural efficiency, casting becomes increasingly challenging. Good weldability not only allows castings to be repaired through repair welding, improving yield and reducing manufacturing costs, but also requires many components to be connected through structural welding, placing stringent demands on the material's weldability. Furthermore, high-thrust-to-weight ratio aircraft engine designs place even higher demands on component heat resistance and mechanical properties, with service temperatures reaching 900°C or even 1000°C, and the need for weight reduction is extremely stringent. Currently, for high-temperature components requiring welding, cast alloys of wrought alloys (such as K4169, K648, and K5188) are mostly used. While these alloys can be fusion welded, they generally suffer from high specific gravity, insufficient heat resistance, and insufficient strength. Among them, the service temperature of K4169 alloy is limited to below 650℃; K648 alloy can be used below 850℃, but its strength is low at higher temperatures, which limits the service performance of castings; K5188 alloy is a widely used weldable high-temperature alloy with service temperature above 1000℃, but its specific gravity is relatively large (9.09g / cm 3 ), its temperature resistance cannot meet the development requirements of the next-generation aircraft engines, and its cost is high. CM939 alloy is currently the most widely used material for large, complex, thin-walled casing castings, but its temperature resistance is limited to below 800°C, which is insufficient. Existing weldable materials cannot meet the requirements of the next-generation aircraft engines for light weight, high temperature resistance, high strength, and good welding and casting processability, resulting in a shortage of available materials.

[0021] Based on this, the first aspect of the present invention provides a weldable and castable high specific strength Ni3Al-based alloy, which comprises, by mass percentage: Al 5.5%~9.5%, Cr 5%~15%, C 0.01%~0.2%, Fe 9%~15%, Mo+W 1%~8%, Ti 0.1%~3.5%, B 0.005%~0.08%, Hf 0.2%~2%, and the balance is Ni and unavoidable impurities.

[0022] The present invention adopts a new material design concept and adopts a certain amount of elements such as Fe, Al, Ti, Cr, Mo, W, and Hf. Under the premise of ensuring the good welding processability and castability of Ni3Al-based alloy, the alloy has a light specific gravity and excellent mechanical properties, and the cost is lower, meeting the development needs of the next generation of aircraft engines. The Ni3Al-based alloy of the present invention is a weldable alloy with high service temperature and excellent comprehensive performance. It breaks through the material design bottleneck of nickel-based alloys with a total mass fraction of Al and Ti exceeding 6%, which cannot be welded, and solves the problem of lack of available materials faced by the next generation of aircraft engines.

[0023] Al is the main element forming the γ′ phase Ni3 (Al, Ti), and a sufficient amount of γ′ phase is the key to the excellent high-temperature mechanical properties of the alloy of the present invention. At the same time, the high Al content allows the alloy surface to form a dense and stable Al2O3 film under high temperature environment, preventing oxygen from further penetrating into the alloy, playing a protective role, and is crucial to the alloy's oxidation resistance above 1000°C. Therefore, the alloy must have a high Al content. However, too high an Al content will lead to the formation of excessive NiAl phase, which is soft at high temperatures and hard and brittle at room temperature, which is not conducive to the alloy's high-temperature mechanical properties and processability. Therefore, the Al content in the alloy of the present invention is 5.5wt% to 9.5wt%, for example, it can be 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt% or any two thereof, so as to ensure the alloy's high-temperature mechanical properties, oxidation resistance and processability.

[0024] The Cr element mainly plays the role of improving the oxidation resistance and corrosion resistance. By adding an appropriate amount of Cr element, the formation of a Cr2O3 protective film on the alloy surface can be promoted, so that the alloy has good oxidation resistance below 1000°C; adding an appropriate amount of element Cr to the Ni3Al-based alloy can effectively improve the medium-temperature plasticity of the alloy and overcome the medium-temperature brittleness problem of the Ni3Al-based alloy. However, too high a Cr content easily causes the alloy to precipitate brittle phases such as the σ phase at high temperatures, reducing the high-temperature structural stability of the alloy and worsening the high-temperature mechanical properties. Therefore, the Cr element content in the alloy of the present invention is 5wt% to 15wt%, for example, it can be 5wt%, 6wt%, 7wt%, 7.5wt%, 8wt%, 10wt%, 12wt%, 13wt%, 15wt% or a range composed of any two of them, so as to ensure both the high-temperature mechanical properties and the oxidation resistance and corrosion resistance of the alloy.

[0025] The C element is a carbide-forming element. The C element content is regulated within the range of 0.01 wt% to 0.2 wt%, for example, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.2 wt%, or any two thereof, to form a small amount of (Ti, Mo) C and HfC particles in the alloy of the present invention, thereby preventing excessive grain growth by hindering grain boundary movement and playing a strengthening role.

[0026] Adding an appropriate amount of Fe element to the Ni3Al-based alloy of the present invention can greatly improve the welding processability of the alloy, realize the fusion welding of the alloy, and also significantly improve the additive manufacturing processability. However, in the alloy system of the present invention, too high Fe content will lead to the precipitation of more NiAl phases, and may also form brittle phases such as σ phase, which is not conducive to the high-temperature mechanical properties of the alloy. Therefore, the Fe element content in the alloy of the present invention is 9wt% to 15wt%, for example, it can be 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt% or a range composed of any two of them, so as to ensure both the welding processability and high-temperature mechanical properties of the alloy.

[0027] The Mo+W of the present invention refers to the sum of the mass percentages of the Mo element and the W element. The alloy of the present invention may contain only the W element, only the Mo element, or both the W element and the Mo element, and the sum of the mass percentages of the two elements is within a limited range. When adding appropriate amounts of Mo and W elements to the Ni3Al-based alloy, on the one hand, the atomic radius of Mo and W is large, and entering the matrix can play a significant solid solution strengthening role; on the other hand, Mo and W can partially replace the Al atoms in Ni3Al, increase the mismatch degree of the γ / γ' phase, and promote the strengthening effect of the γ' phase. In addition, Mo and W can also play a strengthening role by forming carbide particles with C. At the same time, appropriate amounts of Mo and W are used to ensure a low specific gravity. Therefore, the total content of the Mo element and the W element in the alloy of the present invention is controlled within a range of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% or any two thereof, so as to ensure both the mechanical properties and the low specific gravity of the alloy.

[0028] Ti is the main forming element of γ′ phase Ni3(Al,Ti). The addition of Ti can promote the formation of γ′ phase, improve the high temperature stability of the alloy, and form a small amount of (Ti,Mo)C particles, which play an auxiliary strengthening role. However, too high Ti content can easily lead to the formation of η phase, which is not conducive to the mechanical properties of the alloy. Therefore, the content of Ti in the alloy of the present invention should be controlled within the range of 0.1wt% to 3.5wt%, for example, it can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt% or any two thereof, so as to ensure both high temperature mechanical properties and durability.

[0029] The introduction of an appropriate amount of element B into the alloy of the present invention can effectively strengthen grain boundaries and improve dislocation slip on grain boundaries, prevent hydrogen diffusion along the grain boundaries, and avoid the possibility of environmental hydrogen embrittlement within the material, thereby improving the plasticity of the alloy. The content of element B in the alloy of the present invention should be controlled within a range of 0.005wt% to 0.08wt%, for example, 0.005wt%, 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, or any combination thereof.

[0030] The incorporation of an appropriate amount of Hf into the alloy of the present invention significantly enhances the alloy's high-temperature oxidation resistance by affecting the morphology and chemical composition of the oxide at high temperatures, as well as the degree of internal oxidation. Hf, as a γ'-forming element, promotes the precipitation of the γ' phase, further improving the alloy's high-temperature mechanical properties. The appropriate addition of Hf also improves the alloy's casting processability. The Hf content in the alloy of the present invention should be controlled within a range of 0.2% to 2% by weight, for example, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, or any combination thereof.

[0031] In a specific embodiment of the present invention, the Ni3Al-based alloy does not contain at least one of Ta, Zr, Co, and Si. Further, the Ni3Al-based alloy does not contain Ta, Zr, Co, and Si.

[0032] The introduction of Ta into the Ni3Al-based alloy of the present invention, on the one hand, easily induces the precipitation of σ phase (harmful phase) and excessive β phase, resulting in a decrease in mechanical properties; on the other hand, it increases the specific gravity of the alloy. Moreover, Ta is expensive, which is not conducive to alloy cost control.

[0033] Prior art indicates that trace additions of Si to nickel-based superalloys can promote the formation of a protective oxide film. However, the present invention has discovered that the addition of 0.2% to 2% Hf, combined with other elements, can provide the alloy with sufficient high-temperature oxidation resistance. At the same time, the introduction of Si can reduce grain boundary bonding, degrading the alloy's high-temperature mechanical properties, particularly its durability. Therefore, the present invention significantly improves oxidation resistance without the addition of Si, while also preventing Si from degrading durability and other properties.

[0034] As for the Co element, its introduction into the alloy system can improve the deformation processing performance. However, the alloy of the present invention is a casting alloy, and there is no need to introduce the expensive Co element.

[0035] Prior art indicates that the introduction of Zr into nickel-based superalloys can improve casting processability and toughness. However, the present invention has found that the addition of 0.2% to 2% Hf, combined with other elements, can provide the alloy with good casting processability. Regarding toughness, the addition of B in this alloy, combined with other components, improves the alloy's toughness, avoiding the increased hot cracking tendency caused by the simultaneous addition of Zr and B, which can lead to poor casting and weldability.

[0036] In a specific embodiment of the present invention, in the Ni3Al-based alloy, the mass percentage ratio of the Fe element to the Al element, Fe / Al, is ≤2.3. Furthermore, in the Ni3Al-based alloy, the mass percentage ratio of the Fe element to the Al element, Fe / Al, is 1 to 2.3. For example, Fe / Al can be 1, 1.2, 1.5, 1.6, 1.8, 2, 2.2, 2.3, or a range composed of any two thereof. This ensures that sufficient γ′ phase is formed in the Ni3Al-based alloy of the present invention while avoiding the formation of excessive β phase, thereby ensuring excellent high-temperature mechanical properties of the alloy and giving the alloy good weldability.

[0037] In a specific embodiment of the present invention, in the Ni3Al-based alloy, the mass percentage ratio of the Ti element to the Al element (Ti / Al) is ≤ 0.5. For example, the Ti / Al ratio can be 0.02, 0.05, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, or a range of any two thereof, thereby ensuring the formation of sufficient γ′ phase in the Ni3Al-based alloy of the present invention while avoiding the formation of excessive β phase, thereby enabling the alloy to have excellent high-temperature mechanical properties.

[0038] In a specific embodiment of the present invention, the Ni3Al-based alloy includes a γ′ phase, a γ phase, a carbide phase, and a β phase (NiAl phase). Furthermore, in the Ni3Al-based alloy, the γ′ phase content is ≥50%, the β phase content is ≤20%, and the carbide phase content is 0.1% to 5%.

[0039] By regulating the alloy composition, sufficient γ′ phase and an appropriate amount of carbide phase are obtained, while the β phase content is kept within a reasonable range, ensuring both high-temperature mechanical properties and processability. The γ′ phase is the alloy's primary strengthening phase; a higher γ′ content improves high-temperature mechanical properties. The β phase is brittle at room temperature and soft at high temperatures; an excessive amount of β phase can lead to poor processability and a decrease in high-temperature mechanical properties. A low carbide content results in ineffective grain boundary strengthening, while a high carbide content is detrimental to the alloy's mechanical properties.

[0040] For example, in different embodiments, in the Ni3Al-based alloy, the γ′ phase content can be 50%, 55%, 60%, 65%, 70%, 72% or a range consisting of any two thereof, for example, 60% to 70%; the β phase content can be 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or a range consisting of any two thereof, for example, ≤4%; the carbide phase content can be 0.1%, 0.3%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 4%, 5% or a range consisting of any two thereof, for example, 0.6% to 1.5%.

[0041] The second aspect of the present invention provides a method for preparing the weldable and castable high specific strength Ni3Al-based alloy of the first aspect, comprising the following steps: The components of the weldable and castable high specific strength Ni3Al-based alloy according to the first aspect of the present invention are prepared, vacuum induction melted, and then poured.

[0042] The raw materials of each element in the alloy can be as follows, but are not limited thereto. For example, electrolytic nickel, metallic aluminum, metallic chromium, graphite, pure iron, metallic molybdenum, metallic tungsten, metallic titanium, ferroboron, sponge hafnium, etc. can be used as raw materials.

[0043] In a specific embodiment of the present invention, vacuum induction melting includes: mixing materials according to alloy composition, placing electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten, and graphite in a crucible, and adding other elements from a hopper; after the materials in the crucible are completely melted, refining begins; after refining is completed, cooling to a temperature close to the solidified shell, adding metallic aluminum, and after melting, adding metallic titanium and ferroboron, and after melting, adding argon gas and adding hafnium sponge, stirring evenly, and pouring when the molten steel temperature is controlled at 1400-1480°C.

[0044] After refining, the present invention adds aluminum first, followed by titanium, because adding aluminum lowers the melting point of the alloy melt and releases heat, which is beneficial for smelting. Adding titanium further lowers the melting point, so ferroboron is added after the titanium. Hafnium is added last to prevent excessive burning of the highly active hafnium. Argon is also added to prevent contamination of the melt by oxygen or other gases, avoid oxide formation, and promote heat transfer, thereby improving smelting efficiency.

[0045] The present invention provides a specific method for preparing a weldable and castable high-specific-strength Ni3Al-based alloy, but is not limited thereto. The method may include: mixing the materials according to the alloy composition, placing electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten, and graphite in a crucible, and adding other elements from a hopper; heating the materials in the crucible, first applying low-power electricity to remove hydrogen, then applying high-power electricity until they are completely melted, and then starting refining at a refining temperature of 1530°C to 1580°C for 15 to 90 minutes, with a vacuum degree of <5 Pa during refining; after refining, cooling the material to a temperature close to the solidified shell, adding metallic aluminum in batches, adding metallic titanium and ferroboron after clear melting, and then adding hafnium sponge after clear melting with argon gas, stirring at high power, and controlling the molten steel temperature to 1400 to 1480°C for casting. The specific refining time is conventionally adjusted depending on the amount of molten steel. The specific casting method can be conventional bottom casting or vacuum continuous casting, which will not be described in detail here.

[0046] The third aspect of the present invention provides an alloy component, which is mainly made of the weldable and castable high specific strength Ni3Al-based alloy according to the first aspect of the present invention.

[0047] In a specific embodiment of the present invention, the tensile strength of the alloy component at 900°C is ≥600 MPa, for example, it can be 600 MPa, 610 MPa, 620 MPa, 630 MPa, 640 MPa, 650 MPa, 660 MPa, 670 MPa, 680 MPa, or a range consisting of any two thereof; the tensile strength of the alloy component at 1000°C is ≥350 MPa, for example, it can be 350 MPa, 360 MPa, 370 MPa, 380 MPa, 390 MPa, 400 MPa, 410 MPa, 420 MPa, 430 MPa, 435 MPa, or a range consisting of any two thereof; the tensile strength of the alloy component at 1100°C is ≥120 MPa, for example, it can be 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 183 MPa, or a range consisting of any two thereof.

[0048] In a specific embodiment of the present invention, the alloy component has a durability life of ≥100 h at 1090 ° C / 27 MPa, for example, it can be 100 h, 110 h, 120 h, 130 h, 140 h, 150 h, 160 h, 170 h, 180 h, 190 h, 200 h, 210 h, 220 h or a range consisting of any two thereof.

[0049] In a specific embodiment of the present invention, the density of the alloy component is ≤8g / cm 3 , for example, it can be 8g / cm 3 , 7.9g / cm 3 , 7.8g / cm 3 , 7.7g / cm3 , 7.66g / cm 3 Or a range consisting of any two of them.

[0050] Examples 1 to 8 Examples 1 to 8 provide weldable and castable high-specific-strength Ni3Al-based alloys and preparation methods thereof. The composition of the Ni3Al-based alloys is shown in Table 1.

[0051] A method for preparing a weldable and castable high-specific-strength Ni3Al-based alloy comprises the following steps: (1) Select electrolytic nickel, metallic aluminum, metallic chromium, graphite, pure iron, metallic molybdenum, metallic tungsten, metallic titanium, ferroboron, and sponge hafnium as raw materials, and weigh the raw materials according to the actual composition ratio of the alloy.

[0052] (2) Electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten and graphite are placed in a crucible, and other elements are added from a hopper; smelting is carried out in a medium frequency induction vacuum melting furnace, heating the materials in the crucible, first supplying electricity at a low power to remove hydrogen, then supplying electricity at a high power until the whole is melted, and refining begins. The refining temperature is 1550±10℃, and the refining time is 80min. The vacuum degree during refining is less than 5Pa; after the refining is completed, the temperature is lowered to a temperature close to the solidified shell, and metallic aluminum is added in two equal batches. After the melting is complete, metallic titanium and ferroboron are added. After the melting is complete, argon is added and sponge hafnium is added. The materials are stirred at a high power for about 1 to 2min, and the pouring is carried out when the molten steel temperature is controlled at 1440±10℃.

[0053] Table 1 Composition of different weldable and castable high-strength Ni3Al-based alloys (wt%)

[0054] Comparative Examples 1 to 4 Comparative Examples 1 to 4 provide Ni3Al-based alloys and their preparation methods, respectively. The preparation methods are similar to those in Example 1, except that the compositions of the Ni3Al-based alloys are different. The compositions of the Ni3Al-based alloys in Comparative Examples 1 to 4 are shown in Table 2.

[0055] Table 2 Composition of different Ni3Al-based alloys (wt%)

[0056] Comparative Example 5 Comparative Example 5 provides a weldable high-temperature alloy K5188, which is a currently used weldable high-temperature alloy that can serve above 1000°C. The alloy comprises, by mass percentage, Cr 22.0%, W 14.5%, B 0.01%, C 0.1%, Ni 22.0%, and the balance Co.

[0057] Comparative Example 6 Comparative Example 6 provides a high-temperature alloy CM939, which is currently widely used for large, complex, thin-walled casing castings, mostly used below 850°C, has good welding processability and castability, and includes, by mass percentage, the following: C 0.12%, Cr22.4%, Co 19.0%, W 2.0%, Al 1.7%, Ti 3.4%, Nb 0.85%, Ta 1.25%, B 0.006%, and the balance is Ni.

[0058] Comparative Example 7 Comparative Example 7 provides a high-temperature alloy K487, which has a maximum service temperature of 850°C and good castability and weldability. The alloy comprises, by mass percentage, 0.07% C, 18.5% Cr, 10.0% Mo, 4.5% W, 2.5% Ti, 1.3% Al, and the balance Ni.

[0059] Experimental Example 1 Figure 1 This is the as-cast optical microscopic microstructure of the Ni3Al-based alloy provided in Example 2 of the present invention. The white massive phase in the figure represents the γ / γ' eutectic, the white granular phase represents the carbide phase, the gray irregular massive phase represents the β phase (NiAl phase), and the matrix is ​​a γ'+γ two-phase region. The volume fractions of the γ' phase, carbide phase, and β phase in the alloys of different examples of the present invention and comparative examples were statistically analyzed, and the results are shown in Table 3.

[0060] Table 3 Volume fraction of each phase in different alloys

[0061] Furthermore, the ingots obtained in different embodiments of the present invention and comparative examples were respectively prepared into standard samples for comparative tests, and the density, mechanical properties, etc. were tested, as shown in Tables 4 to 6, respectively.

[0062] Table 4 Density of different alloys (g / cm 3 )

[0063] Table 5 High temperature tensile strength of different alloys (MPa)

[0064] Table 6 High temperature rupture life of different alloys (h)

[0065] In the field of aviation materials, density is a key physical property, and low specific gravity can achieve valuable weight reductions for aviation components. As shown in Table 4, the Ni3Al-based alloy of the present invention significantly improves various performance characteristics while significantly reducing its density, offering significant advantages. This also results in a lower cost for the alloy.

[0066] In terms of mechanical properties, the Ni3Al-based alloy of the present invention, due to its high Al content and the combination with other elements, allows the γ′ strengthening phase in the alloy to completely dissolve back at temperatures exceeding 1150°C, thus maintaining sufficient high-temperature strength above 1000°C. Tables 5 and 6 show that the tensile strength at 900°C is significantly higher than that of CM939 and K487 alloys, and the tensile strength at 1000°C and 1100°C far exceeds that of K5188, CM939, and K487 alloys. Under the same conditions, the endurance life of the alloy far exceeds that of K5188, CM939, and K487 alloys by several dozen times, and this advantage becomes more pronounced at higher temperatures.

[0067] At the same time, the Ni3Al-based alloy of the present invention has excellent high-temperature oxidation resistance. Figure 2 The appearance and peeling of the Ni3Al-based alloy provided in Example 2 of the present invention after oxidation at 1100°C / 100h. As can be seen from the figure, the oxide film on the surface of the sample is uniform and complete, and there is only a very small amount of peeling material in the crucible, which fully demonstrates that the high-temperature oxidation resistance advantage of the alloy of the present invention is very obvious.

[0068] Experimental Example 2 The welding processability of the Ni3Al-based alloy of the present invention was verified. Taking Example 2 and Comparative Example 3 as examples, the welding wire was selected as the main body welding wire, and argon arc welding was performed (welding current 60A, argon gas flow rate 5L / min, base material thickness 3mm). Figure 3 The X-ray image and metallographic structure of the fusion weld of the Ni3Al-based alloy provided in Example 2 of the present invention were obtained. The weld was free of defects such as cracks after visual inspection, fluorescence inspection, and X-ray inspection. Further observation of the microstructure showed that no microcracks were found in either the heat-affected zone or the weld layer, and the structure on both sides of the weld was uniform and the transition was good. Figure 4 The X-ray image of the fusion weld of the Ni3Al-based alloy provided in Comparative Example 3 of the present invention shows that the weld has through cracks and poor weldability.

[0069] In summary, the Ni3Al-based alloy of the present invention has light specific gravity, excellent mechanical properties, good welding processability and castability, and meets the development needs of a new generation of aircraft engines.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Weldable and castable high specific strength Ni3Al based alloy, characterized by: Calculated by mass percentage: Al 5.5%~9.5%, Cr 5%~15%, C 0.01%~0.2%, Fe 9%~15%, Mo+W 1%~8%, Ti 0.1%~3.5%, B 0.005%~0.08%, Hf 0.2%~2%, and the balance is Ni and unavoidable impurities.

2. The weldable and castable high specific strength Ni3Al-based alloy according to claim 1, characterized in that: The Ni3Al-based alloy does not contain at least one of Ta, Zr, Co and Si elements.

3. The weldable and castable high specific strength Ni3Al-based alloy according to claim 1, characterized in that: In the Ni3Al-based alloy, the mass percentage ratio of Fe element to Al element, Fe / Al, is ≤2.

3.

4. The weldable and castable high specific strength Ni3Al-based alloy according to claim 1, characterized in that: In the Ni3Al-based alloy, the mass percentage ratio of Fe element to Al element, Fe / Al, is 1 to 2.

3.

5. The weldable and castable high specific strength Ni3Al-based alloy according to claim 1, characterized in that: In the Ni3Al-based alloy, the mass percentage ratio of Ti element to Al element (Ti / Al) is ≤0.

5.

6. The weldable and castable high specific strength Ni3Al-based alloy according to claim 1, characterized in that: The Ni3Al-based alloy includes a γ' phase, a γ phase, a carbide phase and a β phase.

7. The weldable and castable high specific strength Ni3Al-based alloy according to claim 6, characterized in that: In the Ni3Al-based alloy, the γ′ phase content is ≥50%, the β phase content is ≤20%, and the carbide phase content is 0.1% to 5%.

8. A method for preparing a weldable and castable high specific strength Ni3Al-based alloy, characterized in that: The method comprises the following steps: preparing the components of the weldable and castable high-specific-strength Ni3Al-based alloy according to any one of claims 1 to 7, performing vacuum induction melting, and then pouring.

9. An alloy component, characterized in that The invention is mainly made of the weldable and castable high specific strength Ni3Al-based alloy as claimed in any one of claims 1 to 7.

10. The alloy component according to claim 9, characterized in that Has at least one of the following characteristics: (1) The tensile strength of the alloy component at 900°C is ≥ 600 MPa; (2) The tensile strength of the alloy component at 1000°C is ≥350 MPa; (3) The tensile strength of the alloy component at 1100°C is ≥120 MPa; (4) The alloy components have a durability of ≥100h at 1090°C / 27MPa; (5) The density of the alloy component is ≤8g / cm 3 .

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