Weldable castable high specific strength ni3al-based alloys, methods of making and alloy components

Abstract

The application 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 an alloy part. The weldable and castable high-specific-strength Ni3Al-based alloy comprises the following components in percentage by mass: 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 inevitable impurities. The application adopts elements such as Fe, Al, Ti, Cr, Mo, W and Hf, breaks through the material design bottleneck that the total mass fraction of Al and Ti in the nickel-based alloy exceeds 6% and cannot be welded, and the obtained alloy has light specific gravity, excellent mechanical properties and oxidation resistance, good weldability and castability, and meets the development needs of a new generation of aero-engines.

Description

TECHNICAL FIELD

[0001] The present application 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 an alloy part. BACKGROUND

[0002] Weldability is a key property of cast high-temperature alloys, which directly affects its application range and service reliability. Good weldability not only enables the castings to be repaired by repair welding, improving the yield and reducing the preparation cost. Moreover, many parts need to be connected by structural welding, which puts higher requirements on the weldability of the alloy. The existing technology shows that when the total mass fraction of Al and Ti in the alloy is more than 6%, the alloy is difficult to weld. The Al and Ti content in the wrought high-temperature alloy is low, and most of them can be fusion welded, but the content of the gamma prime strengthening phase is low, which leads to poor thermal stability. Generally, it starts to dissolve rapidly above 900℃, which leads to a sharp decrease in the mechanical properties of the alloy above 900℃. Although most cast high-temperature alloys have good mechanical properties, they have poor weldability or even cannot be welded due to high Al and Ti content. The development of new generation of aero-engines requires lighter and more temperature-resistant parts. The service temperature of the hot end parts is above 900℃ or even close to 1100℃. In order to reduce the weight to the greatest extent, the structure of the parts is highly integrated and complex, which is designed as a large and complex part from multiple parts. The casting difficulty is very high, and higher requirements are put forward for the casting process of the material. However, the existing serviceable weldable materials have problems such as high specific gravity, poor temperature resistance, insufficient strength, poor castability and high cost. Therefore, it is urgent to develop a new type of high-temperature structural material which can be stably served at 900-1100℃, has light weight, high specific strength and good weldability and castability.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application aims to provide a weldable and castable high specific strength Ni3Al-based alloy, a preparation method thereof and an alloy part. The Ni3Al-based alloy of the present application can be stably served at 900-1100℃, and has light weight, high specific strength and good weldability and castability.

[0005] In order to achieve the above-mentioned purpose of the present application, the first aspect of the present application provides a weldable and castable high specific strength Ni3Al-based alloy, which comprises, by mass percentage:

[0006] 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 being Ni and unavoidable impurities.

[0007] In the embodiment of the present application, the Ni3Al-based alloy does not contain at least one of Ta, Zr, Co and Si elements. Further, the Ni3Al-based alloy does not contain Ta, Zr, Co and Si elements.

[0008] In the embodiment of the present application, 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 1-2.3.

[0009] In the embodiment of the present application, the mass percentage ratio of Ti element to Al element in the Ni3Al-based alloy is Ti / Al≤0.5.

[0010] In the embodiment of the present application, the Ni3Al-based alloy comprises γ' phase, γ phase, carbide phase and β phase (NiAl phase). Further, in the Ni3Al-based alloy, the content of γ' phase is ≥50%, the content of β phase is ≤20%, and the content of carbide phase is 0.1%-5%.

[0011] The second aspect of the present application provides a preparation method of the weldable and castable high specific strength Ni3Al-based alloy of the first aspect, comprising the following steps:

[0012] According to the component allocation of the weldable and castable high specific strength Ni3Al-based alloy of the first aspect of the present application, vacuum induction melting is carried out, and then pouring is carried out.

[0013] In the embodiment of the present application, the vacuum induction melting comprises: according to the alloy component allocation, 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 is started; after the refining is completed, the temperature is lowered to near the solidified crust, and metallic aluminum is added, and after the melting is cleaned, metallic titanium and boron iron are added, and after the solution is cleaned, argon gas is added to add sponge hafnium, and stirring is uniform, and pouring is carried out when the temperature of the molten steel is 1400-1480℃.

[0014] The third aspect of the present application provides an alloy component, which is mainly prepared from the weldable and castable high specific strength Ni3Al-based alloy of the first aspect of the present application.

[0015] In the embodiment of the present application, the 900℃ tensile strength of the alloy component is ≥600MPa; the 1000℃ tensile strength of the alloy component is ≥350MPa; and the 1100℃ tensile strength of the alloy component is ≥120MPa.

[0016] In the detailed description of the present application, the alloy component has a stress-rupture life of ≥100h at 1090℃ / 27MPa.

[0017] In the detailed description of the present application, the alloy component has a density of ≤8g / cm 3 .

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The present application uses Fe, Al, Ti, Cr, Mo, W, Hf and other elements, breaks through the material design bottleneck that the total mass fraction of Al and Ti in the nickel-based alloy exceeds 6%, and makes the obtained Ni3Al-based alloy have light specific gravity, excellent mechanical properties and good weldability and castability, thereby meeting the research and development needs of the new generation of aero-engines. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0021] Figure 1 The Ni3Al-based alloy as provided in Example 2 of the present application provides a cast light microscope microstructure;

[0022] Figure 2 The Ni3Al-based alloy as provided in Example 2 of the present application provides a sample appearance (a) and spalling condition (b) after 1100℃ / 100h oxidation;

[0023] Figure 3 The Ni3Al-based alloy as provided in Example 2 of the present application provides an X-ray image (a) and a metallographic structure (b) of a fusion welding weld of the alloy body;

[0024] Figure 4 The Ni3Al-based alloy as provided in Example 2 of the present application provides an X-ray image of a fusion welding weld of the alloy body. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be clearly and completely described below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, rather than all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0026] With the design of aero-engine components tending to be integrated, lightened and hollowed, etc., the integrated structure design of high structural efficiency, the casting difficulty is getting bigger and bigger. Good welding performance not only enables the casting to be repaired by repair welding, improves the yield and reduces the preparation cost, and many components need to be connected by structural welding, which puts forward strict requirements on the weldability of the material. At the same time, the design of high thrust ratio aero-engine puts forward higher requirements on the temperature resistance and mechanical properties of the components, the service temperature reaches 900℃ or even 1000℃, and the weight reduction requirement is very strict. At present, for the high-temperature components that need to be welded, the casting alloy of deformation alloy (such as K4169, K648, K5188, etc.) is mostly used. Although these alloys can be fusion welded, they generally have problems such as large specific gravity, insufficient temperature resistance and strength. Among them, the service temperature of K4169 alloy is limited to below 650℃; K648 alloy can be used below 850℃, but its strength at higher temperature is low, which limits the service performance of the casting; K5188 alloy is a widely used weldable high-temperature alloy that can be used above 1000℃, but its specific gravity is relatively large (9.09g / cm 3 ), the temperature resistance cannot meet the research and development needs of the new generation of aero-engine, and the cost is high. CM939 alloy is the most widely used material for large and complex thin-walled casing castings, but the temperature resistance is limited to below 800℃, which cannot meet the needs. The existing serviceable weldable materials cannot meet the requirements of the new generation of aero-engine for light specific gravity, high temperature resistance, high strength, good welding process and casting process, and face the situation of no available materials.

[0027] Therefore, the present application provides a weldable and castable high specific strength Ni3Al-based alloy in the first aspect, which comprises, by mass percentage:

[0028] 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%, the balance being Ni and unavoidable impurities.

[0029] The application adopts a brand-new material design concept, cooperates with a certain amount of Fe, Al, Ti, Cr, Mo, W, Hf and other elements, under the condition of ensuring good welding process and castability of the Ni3Al-based alloy, makes the alloy have light specific gravity and excellent mechanical properties, and the cost is lower, meets the development needs of the new generation of aero-engine. The Ni3Al-based alloy of the application is a weldable alloy with high service temperature and good comprehensive performance, breaks through the material design bottleneck that the total mass fraction of Al and Ti in the nickel-based alloy exceeds 6%, and solves the situation that there is no material available for the new generation of aero-engine.

[0030] Al element is the main forming element of γ' phase Ni3(Al, Ti), and sufficient γ' phase is the key to the excellent high-temperature mechanical properties of the alloy of the application, and high Al content makes the alloy surface form a dense and stable Al2O3 film in a high-temperature environment, prevents oxygen from further penetrating into the alloy, plays a protective role, and is crucial to the oxidation resistance of the alloy above 1000℃. Therefore, the alloy must have a higher Al content. However, too high Al content will lead to the formation of too much NiAl phase, which is soft at high temperature and hard and brittle at room temperature, which is not conducive to the high-temperature mechanical properties and processability of the alloy. Therefore, the Al content in the alloy of the application is 5.5wt%-9.5wt%, for example, it can be 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt% or a range consisting of any two of them, in order to ensure the high-temperature mechanical properties, oxidation resistance and processability of the alloy.

[0031] Cr element mainly plays a role in improving oxidation resistance and corrosion resistance. By adding an appropriate amount of Cr element, a Cr2O3 protective film can be formed on the surface of the alloy, so that the alloy has good oxidation resistance below 1000℃; adding an appropriate amount of Cr element 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 Cr content is easy to make the alloy precipitate σ phase and other brittle phases at high temperature, reduce the high-temperature microstructure stability of the alloy, and deteriorate the high-temperature mechanical properties. Therefore, the Cr content in the alloy of the application is 5wt%-15wt%, for example, it can be 5wt%, 6wt%, 7wt%, 7.5wt%, 8wt%, 10wt%, 12wt%, 13wt%, 15wt% or a range consisting of any two of them, in order to ensure the high-temperature mechanical properties and oxidation resistance, corrosion resistance of the alloy.

[0032] C element is the forming element of carbide, the content of C element is controlled in the range of 0.01wt%-0.2wt%, for example, it can be 0.01wt%, 0.05wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.2wt% or a range consisting of any two of them, to form a small amount of (Ti, Mo) C and HfC particles in the alloy of the application, prevent excessive grain growth by hindering grain boundary movement, and play a strengthening role.

[0033] Adding an appropriate amount of Fe element in the Ni3Al-based alloy of the application can greatly improve the weldability of the alloy, realize the fusion welding of the alloy, and also significantly improve the additive manufacturing process. However, in the alloy system of the application, too high Fe content will lead to the precipitation of more NiAl phase, and may also form brittle phases such as sigma phase, which is not conducive to the high temperature mechanical properties of the alloy. Therefore, the content of Fe element in the alloy of the application is 9wt%-15wt%, for example, it can be 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt% or a range consisting of any two of them, to ensure the weldability and high temperature mechanical properties of the alloy.

[0034] Mo+W in the application refers to the sum of the mass percentages of Mo element and W element, the alloy of the application can only contain W element, only contain Mo element, or contain both W element and Mo element, as long as the sum of the mass percentages of the two is within the limited range. Adding an appropriate amount of Mo and W elements to the Ni3Al-based alloy, on the one hand, Mo and W have large atomic radii, which can play a significant solid solution strengthening effect when entering the matrix; on the other hand, Mo and W can partially replace Al atoms in Ni3Al, increase the misfit degree of γ / γ' two phases, and promote the strengthening effect of γ' phase. In addition, Mo and W can also play a strengthening effect by forming carbide particles with C. At the same time, an appropriate amount of Mo and W is used to ensure low specific gravity. Therefore, the total content of Mo element and W element in the alloy of the application is controlled in the range of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% or any two of them, to ensure the mechanical properties and low specific gravity of the alloy.

[0035] Ti element is the main forming element of γ' phase Ni3(Al, Ti), the addition of Ti element can promote the formation of γ' phase, improve the high temperature stability of the alloy, and also form a small amount of (Ti, Mo) C particles, which play a role in auxiliary strengthening; but too high Ti content is easy to form η phase, which is not conducive to the mechanical properties of the alloy, therefore the content of Ti element in the alloy of the application should be controlled in 0.1wt%-3.5wt%, for example, it can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt% or a range consisting of any two of them, in order to ensure the high temperature mechanical properties and endurance performance.

[0036] The introduction of appropriate amount of B element in the alloy of the application can effectively strengthen the grain boundary and improve the dislocation slip on the grain boundary, prevent the diffusion of hydrogen along the grain boundary, avoid the possibility of environmental hydrogen embrittlement in the material, thereby improving the plasticity of the alloy. The content of B element in the alloy of the application should be controlled in 0.005wt%-0.08wt%, for example, it can be 0.005wt%, 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt% or a range consisting of any two of them.

[0037] The introduction of appropriate amount of Hf element in the alloy of the application can improve the adhesion of the oxide film and the alloy matrix by affecting the morphology and chemical composition of the oxide at high temperature and the degree of internal oxidation, greatly improve the high temperature oxidation resistance of the alloy; Hf element as a γ' phase forming element, promotes the precipitation of γ' phase, further improves the high temperature mechanical properties of the alloy; appropriate addition of Hf can also improve the casting process of the alloy. The content of Hf element in the alloy of the application should be controlled in 0.2wt%-2wt%, for example, it can be 0.2wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt% or a range consisting of any two of them.

[0038] In the specific embodiment of the application, the Ni3Al-based alloy does not contain at least one of Ta, Zr, Co and Si elements. Further, the Ni3Al-based alloy does not contain Ta, Zr, Co and Si elements.

[0039] In the Ni3Al-based alloy of the application, the introduction of Ta can easily induce the precipitation of σ phase (harmful phase) and excessive β phase, which leads to the decrease of mechanical properties, on the other hand, it can increase the specific gravity of the alloy, and the price of Ta is high, which is not conducive to the cost control of the alloy.

[0040] The prior art shows that trace addition of Si in nickel-based superalloys can promote the formation of protective oxide film. However, the present application has found that the addition of 0.2% to 2% Hf in combination with the other elements can provide sufficient high-temperature oxidation resistance for the alloy; at the same time, the introduction of Si can lead to a decrease in the grain boundary bonding force and reduce the high-temperature mechanical properties, especially the stress-rupture properties, of the alloy. Therefore, the present application can significantly improve the oxidation resistance without introducing Si, and at the same time avoid the deterioration of the stress-rupture properties and the like.

[0041] For the Co element, the introduction of Co in the alloy system can improve the deformation processing performance, but the alloy of the present application is a cast alloy, and there is no need to introduce the expensive Co element.

[0042] The prior art shows that the introduction of Zr in nickel-based superalloys can improve the castability and toughness. However, the present application has found that the addition of 0.2% to 2% Hf in combination with the other elements can provide good castability for the alloy; for the toughness, the addition of B in combination with the other components in the alloy can improve the toughness of the alloy, and avoid the increase in the hot cracking tendency caused by the simultaneous addition of Zr and B, thereby leading to poor castability and poor welding processability.

[0043] In the specific embodiments of the present application, 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 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 formed by any two of them, which can ensure that sufficient γ′ phase is formed in the Ni3Al-based alloy of the present application, while avoiding the formation of excessive β phase, thereby ensuring excellent high-temperature mechanical properties of the alloy and making the alloy have good weldability.

[0044] In the specific embodiments of the present application, the mass percentage ratio of Ti element to Al element in the Ni3Al-based alloy is Ti / Al≤0.5. For example, Ti / Al can be 0.02, 0.05, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5 or a range formed by any two of them, thereby ensuring that sufficient γ′ phase is formed in the Ni3Al-based alloy of the present application, while avoiding the formation of excessive β phase, so that the alloy has excellent high-temperature mechanical properties.

[0045] In the specific embodiments of the present application, the Ni3Al-based alloy includes γ′ phase, γ phase, carbide phase and β phase (NiAl phase). Further, in the Ni3Al-based alloy, the content of γ′ phase is ≥50%, the content of β phase is ≤20%, and the content of carbide phase is 0.1% to 5%.

[0046] The alloy composition is adjusted to obtain sufficient γ' phase, appropriate carbide phase and not too high β phase content, so as to ensure high temperature mechanical properties, processing performance and the like. The γ' phase is the main strengthening phase of the alloy, and the higher the content is, the more favorable the high temperature mechanical properties are; the β phase is relatively brittle at room temperature and relatively soft at high temperature, and excessive β phase content can easily lead to poor processing performance of the alloy and decline of the high temperature mechanical properties; and the content of the carbide phase is not obvious if too low, and the content of the carbide phase is not conducive to the mechanical properties of the alloy if too high.

[0047] As in different embodiments, the content of the γ' phase in the Ni3Al-based alloy can be 50%, 55%, 60%, 65%, 70%, 72% or a range formed by any two of them, for example 60%-70%; the content of the β phase can be 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or a range formed by any two of them, for example ≤4%; and the content of the carbide phase can be 0.1%, 0.3%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 4%, 5% or a range formed by any two of them, for example 0.6%-1.5%.

[0048] The second aspect of the present application provides a preparation method of the weldable and castable high specific strength Ni3Al-based alloy of the first aspect, comprising the following steps:

[0049] According to the component allocation of the weldable and castable high specific strength Ni3Al-based alloy of the first aspect of the present application, vacuum induction melting is performed, and then pouring is performed.

[0050] The raw materials of the elements in the alloy can be used as follows, but are not limited thereto, for example, electrolytic nickel, metal aluminum, metal chromium, graphite, pure iron, metal molybdenum, metal tungsten, metal titanium, boron iron, sponge hafnium and the like can be used as raw materials.

[0051] In the specific embodiment of the present application, the vacuum induction melting comprises: according to the component allocation of the alloy, placing electrolytic nickel, metal chromium, pure iron, metal molybdenum, metal tungsten and graphite in a crucible, and adding other elements from a hopper; after the materials in the crucible are completely melted, refining is started; after the refining is completed, the temperature is lowered to near the solidified shell, metal aluminum is added, metal titanium and boron iron are added after the melt is cleaned, sponge hafnium is added after the solution is cleaned, stirring is uniform, and pouring is performed when the temperature of the molten steel is 1400-1480℃.

[0052] After the refining is completed, the addition of metal aluminum can lower the melting point of the alloy melt, accompanied by heat release, which is beneficial to the material melting, so the metal aluminum is added first, and then the metal titanium is added; after the metal titanium is added, the melting point of the melt is further reduced, so the boron iron is added after the metal titanium is added. Finally, the metal hafnium is added to avoid excessive burning loss of the strong active metal hafnium, and argon is filled to prevent the melt from being contaminated by oxygen or other gases, avoid the generation of oxides, and promote heat transfer to improve the smelting efficiency.

[0053] The present application provides a preparation method of a specific weldable and castable high specific strength Ni3Al-based alloy, but is not limited thereto, which can include: according to the alloy composition, charging electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten, graphite into a crucible, and other elements are added from a hopper; heating the materials in the crucible, first sending power at a small power to remove hydrogen, and then sending power at a large power to full melting, starting refining, the refining temperature is 1530-1580℃, the refining time is 15-90min, and the vacuum degree during refining is <5Pa; after the refining is completed, the temperature is lowered to near the solid shell, and the metallic aluminum is added in batches, the metallic titanium and ferroboron are added after the melt is cleaned, the sponge hafnium is added after the solution is cleaned, the argon is filled, the large power is stirred uniformly, and the pouring is performed when the temperature of the molten steel is controlled to be 1400-1480℃. The specific refining time is adjusted regularly according to the amount of molten steel. The specific pouring can be formed by using the conventional bottom casting or vacuum continuous casting, which is not described herein.

[0054] The third aspect of the present application provides an alloy component, which is mainly prepared from the weldable and castable high specific strength Ni3Al-based alloy of the first aspect of the present application.

[0055] In the specific embodiment of the present application, the 900℃ tensile strength of the alloy component is ≥600MPa, for example, can be 600MPa, 610MPa, 620MPa, 630MPa, 640MPa, 650MPa, 660MPa, 670MPa, 680MPa or a range consisting of any two of them; the 1000℃ tensile strength of the alloy component is ≥350MPa, for example, can be 350MPa, 360MPa, 370MPa, 380MPa, 390MPa, 400MPa, 410MPa, 420MPa, 430MPa, 435MPa or a range consisting of any two of them; the 1100℃ tensile strength of the alloy component is ≥120MPa, for example, can be 120MPa, 130MPa, 140MPa, 150MPa, 160MPa, 170MPa, 180MPa, 183MPa or a range consisting of any two of them.

[0056] In the specific embodiment of the present application, the alloy component has a stress-rupture life ≥100h at 1090℃ / 27MPa, for example, can be 100h, 110h, 120h, 130h, 140h, 150h, 160h, 170h, 180h, 190h, 200h, 210h, 220h or a range consisting of any two of them.

[0057] In the specific embodiment of the present application, the density of the alloy component is ≤8g / cm 3 , for example, can be 8g / cm 3 , 7.9g / cm 3 , 7.8g / cm3 7.7 g / cm3 3 7.66 g / cm3 3 or a range consisting of any two of them.

[0058] Examples 1-8

[0059] Examples 1-8 respectively provide a weldable and castable high specific strength Ni3Al-based alloy and a preparation method thereof, the composition of the Ni3Al-based alloy is shown in Table 1.

[0060] The preparation method of the weldable and castable high specific strength Ni3Al-based alloy comprises the following steps:

[0061] (1) Selecting electrolytic nickel, metallic aluminum, metallic chromium, graphite, pure iron, metallic molybdenum, metallic tungsten, metallic titanium, boron iron, and sponge hafnium as raw materials, and weighing the raw materials according to the actual alloy composition ratio for standby.

[0062] (2) Placing electrolytic nickel, metallic chromium, pure iron, metallic molybdenum, metallic tungsten, and graphite in a crucible, and adding other elements from a hopper; melting in a medium-frequency induction vacuum melting furnace, heating the materials in the crucible, first sending small power to remove hydrogen, then sending large power to full melting, starting refining, the refining temperature is 1550±10℃, refining for 80min, the vacuum degree during refining is <5Pa; after the refining is completed, the temperature is lowered to near the solid shell, and an equal amount of two batches of metallic aluminum is added, after melting, metallic titanium and boron iron are added, after dissolving, argon gas is filled to add sponge hafnium, large power stirring for about 1-2min, and the molten steel is poured when the temperature is controlled at 1440±10℃.

[0063] Table 1 Composition of different weldable and castable high specific strength Ni3Al-based alloys (wt%)

[0064]

[0065] Comparative Examples 1-4

[0066] Comparative Examples 1-4 respectively provide a Ni3Al-based alloy and a preparation method thereof, the preparation method refers to Example 1, and the difference lies in that the composition of the Ni3Al-based alloy is different. The composition of the Ni3Al-based alloy of Comparative Examples 1-4 is shown in Table 2.

[0067] Table 2 Composition of different Ni3Al-based alloys (wt%)

[0068]

[0069] Comparative Example 5

[0070] Comparative Example 5 provides a weldable high-temperature alloy K5188, which is a weldable high-temperature alloy currently in use and can serve above 1000℃, and comprises, by mass percent: Cr 22.0%, W 14.5%, B 0.01%, C 0.1%, Ni 22.0%, and the balance Co.

[0071] Comparative Example 6

[0072] Comparative Example 6 provides a high-temperature alloy CM939, which is a material currently widely used for large and complex thin-walled casing castings, and is mainly used below 850℃, has good weldability and castability, and comprises, by mass percent: C 0.12%, Cr 22.4%, Co 19.0%, W 2.0%, Al 1.7%, Ti 3.4%, Nb 0.85%, Ta 1.25%, B 0.006%, and the balance Ni.

[0073] Comparative Example 7

[0074] Comparative Example 7 provides a high-temperature alloy K487, which has a service temperature of up to 850℃ and has good castability and weldability, and comprises, by mass percent: C 0.07%, Cr 18.5%, Mo 10.0%, W 4.5%, Ti 2.5%, Al 1.3%, and the balance Ni.

[0075] Experimental Example 1

[0076] Figure 1 The cast light microscope microstructure of the Ni3Al-based alloy provided in Embodiment 2 of the present application is shown in the figure. The white block phase is γ / γ' eutectic, the white granular phase is carbide phase, the gray irregular block phase is β phase (NiAl phase), and the matrix is γ' + γ two-phase region. The volume fractions of γ' phase, carbide phase and β phase in the alloys of different embodiments and comparative examples of the present application are counted, and the results are shown in Table 3.

[0077] Table 3 Volume fractions of different phases in different alloys

[0078]

[0079] Further, the ingots prepared in different embodiments and comparative examples of the present application are respectively prepared into standard samples for comparative tests, and the density, mechanical properties and the like are tested, which are shown in Tables 4-6, respectively.

[0080] Table 4 Density (g / cm 3 )

[0081]

[0082] Table 5 High-temperature tensile strength (MPa) of different alloys

[0083]

[0084] Table 6 High temperature stress-rupture life (h) of different alloys

[0085]

[0086] In the field of aviation materials, density is one of the key physical property parameters, and low specific gravity can achieve valuable weight reduction of aviation components. As can be seen from Table 4, the Ni3Al-based alloy of the present application has a significantly reduced density while significantly improving various properties, which has a very obvious advantage. At the same time, the alloy of the present application has a relatively low cost.

[0087] In terms of mechanical properties, the Ni3Al-based alloy of the present application can maintain sufficient high-temperature strength at 1000℃ or above due to the high Al content and the combination of other elements, and the complete re-dissolution temperature of the γ' strengthening phase in the alloy can reach 1150℃ or above. As can be seen from Tables 5 and 6, the tensile strength at 900℃ is significantly higher than that of CM939 and K487 alloys, the tensile strength at 1000℃ and 1100℃ is much higher than that of K5188, CM939 and K487 alloys, and the stress-rupture life under the same conditions is much higher than that of K5188, CM939 and K487 alloys, reaching several tens of times or more, and the higher the temperature, the more obvious the advantage.

[0088] At the same time, the Ni3Al-based alloy of the present application has excellent high-temperature oxidation resistance. Figure 2 The appearance and spalling of the Ni3Al-based alloy provided in Example 2 of the present application after 1100℃ / 100h oxidation are shown in the figure, and as can be seen, the oxidation film on the surface of the sample is uniform and complete, and there is only a small amount of spalling in the crucible, which fully illustrates that the high-temperature oxidation resistance of the alloy of the present application is very obvious.

[0089] Experimental Example 2

[0090] The welding process of the Ni3Al-based alloy of the present application was verified. Taking Example 2 and Comparative Example 3 as examples, the welding wire was selected as the body welding wire, and the argon arc welding was carried out (welding current 60A, argon flow rate 5L / min, base material thickness 3mm). Figure 3 The X-ray image and microstructure of the body fusion welding of the Ni3Al-based alloy provided in Example 2 of the present application are shown in the figure, and the welding seam is free of cracks and other defects after visual inspection, fluorescence inspection and X-ray inspection; further observation of the microstructure shows that there is no microcrack in the heat-affected zone or the welding layer, and the microstructure on both sides of the welding seam is uniform and the transition is good. Figure 4 The X-ray image of the body fusion welding of the Ni3Al-based alloy provided in Comparative Example 3 of the present application is shown in the figure, and the welding seam has a through crack, which has poor weldability.

[0091] In conclusion, the Ni3Al-based alloy has light specific gravity, excellent mechanical properties, good weldability and castability, and meets the development needs of a new generation of aeroengines.

[0092] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A weldable, castable, high specific strength Ni3Al-based alloy, characterized in that, comprising, by mass percent: Al 5.5% to 9.5%, Cr 5% to 15%, C 0.01% to 0.2%, Fe 9% to 15%, Mo+W 1% to 8%, Ti 0.1% to 3.5%, B 0.005% to 0.08%, Hf 0.2% to 0.8%, and the balance Ni and unavoidable impurities; the Ni3Al-based alloy does not contain Si element; in the Ni3Al-based alloy, the mass ratio of Fe element to Al element, Fe / Al, is 1 to 2.

3.

2. The weldable, castable, high specific strength Ni3Al-based alloy of claim 1, wherein, in the Ni3Al-based alloy, at least one of Ta, Zr and Co elements is not contained.

3. The weldable, castable, high specific strength Ni3Al-based alloy of claim 1, wherein: in the Ni3Al-based alloy, the mass ratio of Ti element to Al element, Ti / Al, is ≤0.

5.

4. The weldable, castable, high specific strength Ni3Al-based alloy of claim 1, wherein, in the Ni3Al-based alloy, γ' phase, γ phase, carbide phase and β phase are contained.

5. The weldable, castable, high specific strength Ni3Al-based alloy of claim 4, wherein: in the Ni3Al-based alloy, the content of γ' phase is ≥50%, the content of β phase is ≤20%, and the content of carbide phase is 0.1% to 5%.

6. A method of producing a weldable and castable high specific strength Ni3Al-based alloy, characterized by, comprising the following steps: distributing the components of the weldable and castable high specific strength Ni3Al-based alloy according to any one of claims 1 to 5, vacuum induction melting, and then pouring.

7. An alloy component characterized by, mainly made of the weldable and castable high specific strength Ni3Al-based alloy according to any one of claims 1 to 5.

8. The alloy component of claim 7, wherein, having at least one of the following characteristics: (1) the tensile strength of the alloy part at 900℃ is ≥600MPa; (2) the tensile strength of the alloy part at 1000℃ is ≥350MPa; (3) the tensile strength of the alloy part at 1100℃ is ≥120MPa; (4) the stress-rupture life of the alloy part at 1090℃ / 27MPa is ≥100h; (5) the alloy component has a density < 8 g / cm3 3 .

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