Nickel-based single-crystal high-temperature alloy and preparation method thereof

Abstract

The invention relates to a nickel-based single-crystal high-temperature alloy and a preparation method thereof, and relates to the technical field of single-crystal high-temperature alloys. According to the main technical scheme, the nickel-based single crystal high-temperature alloy is prepared from the following chemical components in percentage by mass: 6 to 8 weight percent of Cr, 7 to 9 weight percent of Co, 1 to 3 weight percent of Mo, 7 to 9 weight percent of W, 5 to 7 weight percent of Ta, 5 to 7 weight percent of Al, 0.5 to 2 weight percent of Ti, 0.5 to 1 weight percent of Nb, 0.008 to 0.013 weight percent of N and the balance of Ni. After the Nb and the trace element N are introduced, the void ratio in the as-cast alloy is reduced by 35%, the void ratio of the heat-treated alloy is reduced to 28% after treatment of a set heat treatment process, and the high-temperature strength and the endurance life of the low-cost second-generation single-crystal high-temperature alloy are further improved. The nickel-based single-crystal high-temperature alloy is particularly suitable for manufacturing hot-end high-temperature components with long service life and high reliability in the fields of aviation, aerospace, energy and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal high temperature alloys, and in particular to a nickel-based single crystal high temperature alloy and a preparation method thereof. Background Art

[0002] With the development of science and technology fields such as aircraft engines, ship gas turbines and ground gas turbines, the single crystal high-temperature alloy materials used in engine turbine blades must have high density and high-temperature strength. At the same time, their research and development must have low use and maintenance costs.

[0003] At present, with the addition of Re element, the strength of the γ matrix phase of single crystal superalloy is greatly improved, the movement of dislocations in the matrix is ​​restricted, and the high temperature strength of single crystal alloy is significantly improved. However, the price of Re element is very expensive, which is not conducive to the sustainable development of single crystal superalloy. Therefore, it is urgent to develop low-cost and high-performance single crystal superalloy without Re element.

[0004] At present, Chinese researchers have developed a series of Re-free second-generation nickel-based single-crystal superalloys by increasing the volume fraction of the γ′ phase, such as DD98M, DD13, DD413M and M09A. The high-temperature properties of these alloys are similar to those of traditional Re-containing second-generation single-crystal superalloys, but the porosity of the alloys has reached 0.18%, and it is impossible to further improve their high-temperature strength by regulating the alloy elements to reduce the alloy porosity.

[0005] In summary, people expect to obtain a nickel-based single crystal high-temperature alloy with low preparation cost, excellent density and high-temperature durability. Summary of the invention

[0006] In view of this, the present invention provides a nickel-based single crystal high-temperature alloy and a preparation method thereof, the main purpose of which is to provide a nickel-based single crystal high-temperature alloy with low preparation cost, excellent density and high-temperature durability.

[0007] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0008] On the one hand, an embodiment of the present invention provides a nickel-based single crystal high-temperature alloy, which includes the following chemical components, in mass percentage: Cr: 6-8wt%, Co: 7-9wt%, Mo: 1-3wt%, W: 7-9wt%, Ta: 5-7wt%, Al: 5-7wt%, Ti: 0.5-2wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni.

[0009] Preferably, the nickel-based single crystal high-temperature alloy includes the following chemical components, in mass percentage: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni.

[0010] Preferably, it includes the following chemical components in mass percentage: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.6-0.8wt%, N: 0.009-0.011wt%, and the balance is Ni.

[0011] Preferably, if the nickel-based single crystal high temperature alloy is a cast alloy, the nickel-based single crystal high temperature alloy has dispersedly distributed approximately spherical TiN phase and NbN phase between dendrites; preferably, the diameter of the TiN phase and NbN phase is 3-5 μm.

[0012] Preferably, if the nickel-based single crystal high-temperature alloy is a heat-treated alloy, the matrix phase of the nickel-based single crystal high-temperature alloy includes a γ phase and a γ′ phase, and the reinforcement phase is a dispersed, approximately spherical TiN phase and NbN phase; preferably, the diameter of the TiN phase and the NbN phase is 3-5 μm.

[0013] Preferably, if the nickel-based single crystal high temperature alloy is a cast alloy, the porosity of the nickel-based single crystal high temperature alloy is 0.05-0.15%.

[0014] Preferably, if the nickel-based single crystal high temperature alloy is a heat-treated alloy, the porosity of the nickel-based single crystal high temperature alloy is 0.15-0.3%.

[0015] Preferably, the nickel-based single crystal high-temperature alloy has a durability life of 240 to 260 hours under the conditions of 800±1°C and 750±1MPa.

[0016] The nickel-based single crystal high-temperature alloy has a durability of 215 to 245 hours under the conditions of 980±1° C. and 250±1 MPa.

[0017] The nickel-based single crystal high-temperature alloy has a durability of 115 to 135 hours under the conditions of 1100±1° C. and 137±1 MPa.

[0018] On the other hand, an embodiment of the present invention provides a method for preparing the above-mentioned nickel-based single crystal at high temperature, which comprises the following steps:

[0019] Vacuum induction melting: vacuum induction melting produces a master alloy ingot that meets the required chemical composition;

[0020] Preparing a single crystal alloy: preparing the master alloy ingot into a single crystal alloy;

[0021] Heat treatment: The single crystal alloy is subjected to solution treatment and aging treatment in sequence to obtain a nickel-based single crystal high temperature alloy.

[0022] Preferably, during vacuum induction melting, the N element is added to the vacuum induction furnace in the form of CrN.

[0023] Preferably, in the vacuum induction melting step, the refining temperature is 1550±10°C, the refining time is 30 to 50 minutes, and the vacuum degree during the refining period is ≤5Pa.

[0024] Preferably, the step of solution treatment includes: heating the single crystal alloy to a first solution temperature at a first set heating rate, keeping the first solution temperature for a first time, heating it to a second solution temperature at a second set heating rate, keeping the second solution temperature for a second time, heating it to a third solution temperature at a third set heating rate, keeping the third solution temperature for a third time, cooling to room temperature, and obtaining a single crystal alloy after solution treatment; wherein the first solution temperature is 1285-1295°C, the second solution temperature is 1295-1305°C, and the third solution temperature is 1305-1310°C; the third solution temperature is greater than the second solution temperature; the second solution temperature is greater than the first solution temperature; the first set heating rate is 3-10°C / min; the second set heating rate is 1-3°C / min; the third set heating rate is 1-3°C / min; preferably, the first time is 1-3h, the second time is 1-3h, and the third time is 3-6h.

[0025] Preferably, the aging treatment step comprises: heating the single crystal high-temperature alloy after the solution treatment to 1060-1090°C at a heating rate of 50-100°C / min, keeping it warm for 4-8 hours, and cooling it to room temperature; then heating it to 850-900°C at a heating rate of 50-100°C / min, keeping it warm for 20-32 hours, and cooling it to room temperature to obtain a nickel-based single crystal high-temperature alloy.

[0026] On the other hand, an embodiment of the present invention further provides a nickel-based single crystal high-temperature alloy part, wherein the nickel-based single crystal high-temperature alloy part is made of any of the single crystal high-temperature alloys described above.

[0027] Preferably, the nickel-based single crystal high-temperature alloy part is a low-pressure turbine blade or a high-pressure guide vane of an engine.

[0028] Compared with the prior art, the nickel-based single crystal high-temperature alloy and the preparation method thereof of the present invention have at least the following beneficial effects:

[0029] On the one hand, an embodiment of the present invention provides a nickel-based single crystal high-temperature alloy, which includes the following chemical components, in mass percentage: Cr: 6-8wt%, Co: 7-9wt%, Mo: 1-3wt%, W: 7-9wt%, Ta: 5-7wt%, Al: 5-7wt%, Ti: 0.5-2wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni. Here, regarding the nickel-based single crystal high-temperature alloy with the above-mentioned composition in the embodiment of the present invention, the present invention introduces Nb (0.5-1wt%) and trace element N (0.008-0.013wt%) on the basis of "Cr: 6-8wt%, Co: 7-9wt%, Mo: 1-3wt%, W: 7-9wt%, Ta: 5-7wt%, Al: 5-7wt%, Ti: 0.5-2wt%": the addition of an appropriate amount of N can form finely dispersed nitrides (TiN, NbN), which can compensate for the shrinkage cavities between dendrites during solidification, reduce the number of casting voids in the alloy, and improve the density and high-temperature durability of the alloy (it should be emphasized here that: based on the alloy system of the present invention, the above-mentioned N content is not dissolved in the matrix phase, but forms nitrides and exists between dendrites during solidification, thereby reducing the molten pool space between dendrites to avoid molten pool shrinkage cavities). However, too much N content will form large-sized nitrides, forming nitride skeletons between dendrites, destroying the integrity of dendrites, resulting in an increase in the density of alloy voids and deteriorating the mechanical properties of the alloy. When the Ti content is too much, TiN with large size and irregular shape will be formed, causing stress concentration on the matrix and aggravating crack initiation. Therefore, the present invention also adds a small amount of Nb element on this basis. On the one hand, fine NbN can be formed while forming fine and dispersed TiN, further compensating for the solidification and shrinkage between dendrites; on the other hand, Nb can shorten the distance between dendrites and promote the late stage of solidification, and the melt can fill the gaps between dendrites (here, solidification shrinkage and melt filling the gaps between dendrites are important reasons for reducing holes). In summary, through the synergistic effect of the above elements, the nickel-based single crystal high-temperature alloy has excellent density. At the same time, due to the reduction of internal voids and defects in the alloy, the cracking tendency of the creep crack source is reduced, thereby improving the high-temperature durability of the alloy and no Re element needs to be added, so that the preparation cost of the nickel-based single crystal high-temperature alloy is low.

[0030] On the other hand, the embodiment of the present invention provides a method for preparing a nickel-based single crystal high-temperature alloy, which selects a set solution treatment system so that the increase rate of the solution temperature is slow, which can make the alloy maintain a long time at high temperature, which is beneficial to the uniform distribution of nitrides in the alloy and the sufficient flow of the melt between dendrites. In addition, the set heat treatment system only regulates the morphology and size of the γ′ precipitation phase, and has no significant effect on the already formed TiN phase and NbN phase.

[0031] In summary, a nickel-based single crystal high-temperature alloy provided in an embodiment of the present invention contains finely dispersed TiN and NbN, which can reduce the shrinkage cavities between dendrites during the shrinkage-feeding solidification process, reduce the number of casting voids in the alloy (the void rates in the cast and heat-treated states are reduced by 35% and 28%, respectively), and improve the density of the alloy; in addition, under three long-lasting loading conditions of 800℃ / 750MPa, 980℃ / 250MPa and 1100℃ / 137MPa, the long-lasting life of the alloy of the present invention is increased by 20-30h, 40-50h and 25-35h, respectively.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Figure 1 is a hole defect image of the as-cast alloy prepared in Comparative Example 1 and Example 1;

[0034] Figure 2 Figure 1 is a hole defect image of the heat-treated alloys prepared in Comparative Example 1 and Example 1;

[0035] Figure 3 The morphology and composition analysis of the nitride in the heat-treated alloy prepared in Example 2;

[0036] Figure 4 This is a comparison chart of the endurance life of the alloy prepared in Example 2, the alloy prepared in Comparative Example 2, and the DD5 alloy;

[0037] Figure 5 The nitride morphology of the alloy prepared in Comparative Example 4 with a N content of 0.045 wt%;

[0038] Figure 6 It is a comparison chart of the endurance life of the alloy of comparative example 3, the alloy of comparative example 4 and the alloy of example 2 under three conditions of 800°C / 750MPa, 980°C / 250MPa and 1100°C / 137MPa;

[0039] Figure 7 A comparison diagram of the sizes of hot nitrides of the heat-treated alloys in Comparative Example 5 and Example 1;

[0040] Figure 8 is a comparison diagram of the segregation of γ and γ′ phase components in the heat-treated alloys in Comparative Example 6 and Example 1;

[0041] Fig. 9 It is a comparison chart of the high temperature creep life of the heat-treated alloys in Example 7 and Example 1. DETAILED DESCRIPTION

[0042] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0043] Chemical composition also has an important influence on the high-temperature durability of single crystal high-temperature alloys. Among them, trace elements N and Ti form nitrides (TiN) present in single crystal high-temperature alloys. Generally speaking, large-sized prismatic TiN will cause stress concentration, reduce the fluidity of the melt between dendrites, aggravate the formation of solidification voids, and significantly damage the mechanical properties of the alloy. However, a small amount of N addition will form fine dispersed TiN in the solidification zone between dendrites during the solidification process, compensate for the solidification shrinkage between dendrites, reduce the porosity of the alloy, and thus improve the density and high-temperature strength of the alloy. Therefore, the high-temperature mechanical properties of low-cost Re-free single crystal high-temperature alloys can be further improved by strengthening with trace N elements.

[0044] In addition, the existing related technologies further improve the high-temperature creep resistance of nickel-based single crystal high-temperature alloys by regulating carbides. Carbides improve the high-temperature creep resistance of alloys by reducing shrinkage holes during casting. However, carbides are large in size and uneven in shape, and are prone to crack initiation during subsequent loading. Therefore, compared with carbides, small-sized and high-strength nitrides have a broader application space.

[0045] The scheme of the present invention is mainly as follows:

[0046] On the one hand, an embodiment of the present invention provides a nickel-based single crystal high-temperature alloy, which includes the following chemical components, in mass percentage: Cr: 6-8wt%, Co: 7-9wt%, Mo: 1-3wt%, W: 7-9wt%, Ta: 5-7wt%, Al: 5-7wt%, Ti: 0.5-2wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni.

[0047] Preferably, it includes the following chemical components in mass percentage: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni.

[0048] Further preferably, it includes the following chemical components in mass percentage: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.6-0.8wt%, N: 0.009-0.011wt%, and the balance is Ni.

[0049] It should be noted that the N content in a general single crystal high temperature alloy is less than 0.005%. Generally, N will react with the C phase, affecting carbides and further affecting voids and alloy properties. However, the present invention regulates the N content, Ti content, and Nb content, so that N reacts with Ti and Nb (since the Gibbs free energy of N, Ti, and Nb forming nitrides is lower, they are more likely to form nitrides with each other than with other elements), and has nothing to do with C.

[0050] The present invention adds Nb element to form NbN nitride at the same time as TiN, avoiding the formation of large-sized pointed TiN, while ensuring the content of fine dispersed nitrides and improving the density of the alloy. Therefore, Nb and Ti have a good synergistic regulation effect.

[0051] Here, it should be noted that the addition of an appropriate amount of N can form fine and dispersed nitrides (TiN, NbN), which can compensate for the shrinkage cavities between dendrites during solidification, reduce the number of casting voids in the alloy, and improve the density and high-temperature durability of the alloy. However, excessive N content will form large-sized nitrides, form nitride skeletons between dendrites, destroy the integrity of dendrites, increase the density of alloy voids, and deteriorate the mechanical properties of the alloy. Excessive Ti content will form TiN with large size and irregular shape, causing stress concentration on the matrix and aggravating crack initiation. Therefore, a small amount of Nb element is added to the alloy of the present invention. On the one hand, fine NbN can be formed while forming fine and dispersed TiN, further compensating for the solidification and shrinkage between dendrites; on the other hand, Nb can shorten the distance between dendrites, promote the late stage of solidification, and the molten liquid can fill the gaps between dendrites.

[0052] In addition, regarding the preparation of the above-mentioned nickel-based single crystal high-temperature alloy: pure Ni, Co, Cr, W, Mo, Ta, Ti, Al, Nb and other elements and CrN alloy (except CrN, the others are basically pure metals, including pure Cr and CrN alloys) are melted in a vacuum induction furnace (refining temperature: 1520±10°C, refining time is 30min, vacuum degree during refining period ≤5Pa), and cast into a master alloy ingot with chemical composition meeting the requirements, and then remelted by high-speed solidification method or liquid metal cooling method (preferably, 1530℃±10℃ casting, directional solidification pulling rate is 5mm / min±2mm / min; not limited to this), and directional solidified into a single crystal test rod by a spiral crystal selector or seed crystal method. Heat treatment is required before use. The solution heat treatment conditions are to heat the temperature to 1285-1295°C at a heating rate of 3-10°C / min and keep it for 1-3h, then heat the temperature to 1295-1305°C at a heating rate of 1-3°C / min and keep it for 1-3h, then heat the temperature to 1305-1310°C at a heating rate of 1-3°C / min and keep it for 3-6h, and air cool to room temperature after the insulation. The aging treatment method is to heat the temperature to 1060-1090°C at 50-100°C / min and keep it for 4-8h (primary aging), air cool to room temperature after the insulation, and then heat the temperature to 850-900°C at 50-100°C / min and keep it for 20-32h (secondary aging), and air cool to room temperature after the insulation.

[0053] Here, regarding the preparation method of the present invention, it should be noted that:

[0054] (1) Solution treatment is to eliminate the eutectic structure, eliminate the component segregation between dendrites and dendrite stems, and achieve uniform alloy composition. Primary aging mainly controls the size of the γ′ precipitate phase, and secondary aging mainly controls the morphology of the γ′ precipitate phase. Through heat treatment, a uniform and fine γ′ precipitate phase is obtained to ensure that the alloy has excellent high-temperature strength.

[0055] (2) In the solution treatment of the present invention, by controlling the heating rate, the temperature increase rate is slow, so that the alloy can be kept at high temperature for a long time, which is beneficial to the uniform distribution of nitrides in the alloy and the sufficient flow of molten liquid between dendrites. When smelting single crystals, N and Ti, Nb combine to form finely dispersed TiN, NbN and other phases between dendrites. Since nitrides have a high melting point and strong phase stability, only the morphology and size of the γ′ precipitation phase are regulated during the solution and aging heat treatment, and there is no significant effect on the already formed TiN and NbN phases.

[0056] (3) The present invention adopts a multi-step solution treatment to achieve:

[0057] Improved organizational structure: By gradually adjusting the solution temperature and time, the phase transformation and element distribution in the alloy can be better controlled, dendrite segregation can be eliminated, and the organizational structure of the alloy can be improved.

[0058] Improved durability: Multi-step solution treatment can significantly improve the durability of the alloy, especially the mechanical properties at high temperatures.

[0059] Inhibiting the precipitation of harmful phases: By controlling the solid solution process, the precipitation of harmful phases such as TCP phase can be reduced.

[0060] Optimizing element distribution: Multi-step solution treatment can optimize the distribution of key elements in the alloy, thereby improving the overall performance of the alloy.

[0061] In summary, the present invention develops a nickel-based single crystal high-temperature alloy, in which the density of the alloy is further improved, and its high-temperature endurance life is higher than that of the typical second-generation single crystal high-temperature alloy DD5, thereby achieving a low-cost way to improve the endurance life of the Re-free second-generation single crystal alloy, and can be used for high-performance and long-life aircraft engine turbine blade materials.

[0062] The nickel-based single crystal high-temperature alloy of the present invention has at least the following advantages:

[0063] (1) The nickel-based single crystal high temperature alloy of the present invention contains finely dispersed TiN and NbN, which can reduce the shrinkage cavities between dendrites during the shrinkage solidification process, reduce the number of casting voids in the alloy, and improve the density of the alloy. Therefore, compared with the low-cost second-generation nickel-based single crystal high temperature alloy without the introduction of N and Nb, the porosity of the cast and heat-treated state is reduced by 35% and 28%, respectively.

[0064] (2) Under the three conditions of sustained loading of 800°C / 750MPa, 980°C / 250MPa and 1100°C / 137MPa, the service life of the alloy of the present invention is respectively increased by 20 to 30 hours, 40 to 50 hours and 25 to 35 hours compared with the low-cost second-generation nickel-based single crystal high-temperature alloy without the introduction of N and Nb.

[0065] The present invention is further described below by specific embodiments:

[0066] Example 1

[0067] Example 1: Prepare a nickel-based single crystal high-temperature alloy, which includes the following chemical components, in mass percentage: Cr: 6.8wt%, Co: 8.3wt%, Mo: 2.6wt%, W: 7.3wt%, Ta: 5.7wt%, Al: 5.5wt%, Ti: 1.1wt%, Nb: 0.6wt%, N: 0.009wt%, and the balance is Ni.

[0068] The method for preparing the nickel-based single crystal high-temperature alloy of this embodiment comprises the following steps:

[0069] 1) Prepare a master alloy ingot having the above chemical composition by smelting in a vacuum induction furnace (wherein the refining temperature is 1550°C, the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5Pa). During smelting, the N element is added to the vacuum induction furnace in the form of CrN.

[0070] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0071] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0072] The solution treatment conditions are as follows: heating to 1285°C at a heating rate of 3°C / min and keeping warm for 2h; then heating to 1295°C at a heating rate of 2°C / min and keeping warm for 3h; then heating to 1308°C at a heating rate of 2°C / min and keeping warm for 4h; and air cooling to room temperature after the insulation is completed.

[0073] The aging treatment method is as follows: heating to 1060°C at a heating rate of 60°C / min, keeping warm for 5 hours, air cooling to room temperature after the end of the heat preservation, and then heating to 860°C at a heating rate of 60°C / min and keeping warm for 24 hours, and air cooling to room temperature after the end of the heat preservation.

[0074] Comparative Example 1

[0075] Comparative Example 1: A nickel-based single crystal high-temperature alloy is prepared, which includes the following chemical components, in mass percentage: Cr: 6.8wt%, Co: 8.3wt%, Mo: 2.6wt%, W: 7.3wt%, Ta: 5.7wt%, Al: 5.5wt%, Ti: 1.1wt%, and the balance is Ni.

[0076] The preparation method of the nickel-based single crystal high-temperature alloy of Comparative Example 1 comprises the following steps:

[0077] 1) A master alloy ingot having the above chemical composition is prepared by smelting in a vacuum induction furnace (wherein the refining temperature is 1550° C., the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5 Pa).

[0078] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0079] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0080] The solution treatment conditions are as follows: heating to 1285°C at a heating rate of 15°C / min and keeping warm for 2h; then heating to 1290°C at a heating rate of 1°C / min and keeping warm for 2h; then heating to 1308°C at a heating rate of 2°C / min and keeping warm for 4h; and air cooling to room temperature after the insulation is completed.

[0081] The aging treatment method is as follows: heating to 1060°C at a heating rate of 60°C / min, keeping warm for 5 hours, air cooling to room temperature after the end of the heat preservation, and then heating to 860°C at a heating rate of 60°C / min and keeping warm for 24 hours, and air cooling to room temperature after the end of the heat preservation.

[0082] Here, Comparative Example 1 is an original nickel-based single crystal high alloy, and Example 1 introduces N and Nb elements on the basis of Comparative Example 1, that is, a modified nickel-based single crystal high temperature alloy. In addition, the heat treatment system used in Example 1 is different from that in Comparative Example 1.

[0083] The chemical compositions of the nickel-based single crystal high-temperature alloys of Example 1 and Comparative Example 1 are shown in Table 1.

[0084] Table 1 shows the chemical composition (wt%) of the nickel-based single crystal high temperature alloys of Example 1 and Comparative Example 1.

[0085] alloy Cr Co Mo W Ta Al Ti Nb N Ni Comparative Example 1 6.8 8.3 2.6 7.3 5.7 5.5 1.1 0 0 margin Example 1 6.8 8.3 2.6 7.3 5.7 5.5 1.1 0.6 0.009 margin

[0086] The alloys of Example 1 and Comparative Example 1 in the cast and heat-treated state were cut vertically <001> Direction of tissue morphology, observe the macroscopic morphology of internal tissue.

[0087] The cast alloy of Example 1 (i.e., Figure 1 The modified alloy in the step of Example 1, the single crystal test rod in the step of Example 1) and the cast alloy of Comparative Example 1 (ie, Figure 1 The hole morphology of the original alloy in the single crystal test rod in the step of comparative example 1 is as follows Figure 1 As shown. Figure 1 It can be seen that the number of pores in the as-cast alloy of Example 1 is significantly reduced, because the fine, dispersed, nearly spherical TiN and NbN phases (the diameters of the TiN and NbN phases are 3-5 μm) are formed in situ in the interdendritic parts of the alloy of Example 1, which can compensate for the shrinkage cavities between the dendrites during the solidification process and reduce the number of casting cavities of the alloy, so the number of pores in the as-cast alloy of Example 1 is significantly reduced. At the same time, the interdendritic distance of the as-cast alloy of Example 1 is also significantly reduced.

[0088] The heat-treated alloy of Example 1 (i.e., Figure 2 The modified alloy in the example 1) and the heat-treated alloy of the comparative example 1 (i.e., Figure 2 The pore morphology of the original alloy is as follows Figure 2 As shown. Figure 2 It can be seen that the number of pores in the heat-treated alloy of Example 1 (0.25%) is still less than the number of pores in the heat-treated alloy of Comparative Example 1 (0.38%). This is because the number of pores in the cast alloy of Example 1 is relatively small, about 0.12%, while the number of pores in the cast alloy of Comparative Example 1 is 0.22%. Therefore, after heat treatment, the number of pores in the alloy of the present invention is still small.

[0089] Example 2

[0090] Example 2: Prepare a nickel-based single crystal high-temperature alloy, which includes the following chemical components, in mass percentage: Cr: 6.4wt%, Co: 7.3wt%, Mo: 2.6wt%, W: 9wt%, Ta: 5.5wt%, Al: 6.8wt%, Ti: 1.5wt%, Nb: 0.8wt%, N: 0.012wt%, and the balance is Ni.

[0091] The method for preparing the nickel-based single crystal high-temperature alloy of this embodiment comprises the following steps:

[0092] 1) Prepare a master alloy ingot having the above chemical composition by smelting in a vacuum induction furnace (wherein the refining temperature is 1550°C, the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5Pa). During smelting, the N element is added to the vacuum induction furnace in the form of CrN.

[0093] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0094] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0095] The solution treatment conditions are as follows: heating to 1285°C at a heating rate of 8°C / min and keeping warm for 3 hours; then heating to 1295°C at a heating rate of 1.5°C / min and keeping warm for 3 hours; then heating to 1310°C at a heating rate of 2°C / min and keeping warm for 5 hours; and air cooling to room temperature after the insulation is completed.

[0096] The aging treatment method is as follows: heating to 1090°C at a heating rate of 80°C / min, keeping warm for 5 hours, air cooling to room temperature after the end of the insulation, and then heating to 860°C at a heating rate of 80°C / min and keeping warm for 30 hours, and air cooling to room temperature after the end of the insulation.

[0097] Comparative Example 2

[0098] Comparative Example 2: A nickel-based single crystal high-temperature alloy is prepared, which includes the following chemical components, in mass percentage: Cr: 6.4wt%, Co: 7.3wt%, Mo: 2.6wt%, W: 9wt%, Ta: 5.5wt%, Al: 6.8wt%, Ti: 1.5wt%, and the balance is Ni.

[0099] The method for preparing the nickel-based single crystal high-temperature alloy of this embodiment comprises the following steps:

[0100] 1) A master alloy ingot having the above chemical composition is prepared by smelting in a vacuum induction furnace (wherein the refining temperature is 1550° C., the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5 Pa).

[0101] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0102] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0103] The solution treatment conditions are as follows: heating to 1285°C at a heating rate of 20°C / min and keeping warm for 3 hours; then heating to 1295°C at a heating rate of 1.5°C / min and keeping warm for 3 hours; then heating to 1310°C at a heating rate of 2°C / min and keeping warm for 5 hours; and air cooling to room temperature after the insulation is completed.

[0104] The aging treatment method is as follows: heating to 1090°C at a heating rate of 80°C / min, keeping warm for 5 hours, air cooling to room temperature after the end of the insulation, and then heating to 860°C at a heating rate of 80°C / min and keeping warm for 30 hours, and air cooling to room temperature after the end of the insulation.

[0105] Here, Comparative Example 2 is the original nickel-based single crystal high alloy, and Example 2 introduces N and Nb elements on the basis of Comparative Example 2, that is, a modified nickel-based single crystal high temperature alloy. In addition, the heat treatment system used in Example 2 is different from that in Comparative Example 2.

[0106] The chemical compositions of the nickel-based single crystal high-temperature alloys of Example 2 and Comparative Example 2 are shown in Table 2.

[0107] Table 2 shows the chemical composition (wt%) of the nickel-based single crystal high temperature alloys of Example 2 and Comparative Example 2.

[0108] alloy Cr Co Mo W Ta Al Ti Nb N Ni Comparative Example 2 6.4 7.3 2.6 9 5.5 6.8 1.5 0 0 margin Example 2 6.4 7.3 2.6 9 5.5 6.8 1.5 0.8 0.012 margin

[0109] (1) The morphology and composition analysis of the nitride of the heat-treated nickel-based single crystal high-temperature alloy in Example 2 of the present invention are as follows: Figure 3It can be found that the TiN formed in the alloy of Example 2 of the present invention is spherical and small in size, with a diameter of only 3 to 4 μm; the diameter of the NbN phase is about 5 μm, embedded in the γ / γ′ phase.

[0110] (2) The Larson-Miller curves of the alloy in Example 2, the alloy in Comparative Example 2 and the typical second-generation nickel-based single crystal high-temperature alloy DD5 are compared as follows: Figure 4 As shown. Figure 4 It can be seen that the endurance performance of the alloy of Example 2 is significantly higher than that of the alloy of Comparative Example 2 and the DD5 alloy.

[0111] Comparative Example 3

[0112] Comparative Example 3: A nickel-based single crystal high-temperature alloy is prepared, which includes the following chemical components, in mass percentage: Cr: 7.1wt%, Co: 8.3wt%, Mo: 2.2wt%, W: 8.2wt%, Ta: 6.8wt%, Al: 5.2wt%, Ti: 1.4wt%, and the balance is Ni.

[0113] The method for preparing the nickel-based single crystal high-temperature alloy of this embodiment comprises the following steps:

[0114] 1) A master alloy ingot having the above chemical composition is prepared by smelting in a vacuum induction furnace (wherein the refining temperature is 1550° C., the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5 Pa).

[0115] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0116] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0117] Among them, the solution treatment conditions are: 1290℃ / 2h+1295℃ / 2h+1298℃ / 4h, air cooling (AC).

[0118] The aging treatment method is: 1080℃ / 6h, AC+870℃ / 24h, AC.

[0119] Comparative Example 4

[0120] Comparative Example 4: A nickel-based single crystal high-temperature alloy is prepared, which includes the following chemical components, in mass percentage: Cr: 7.1wt%, Co: 8.3wt%, Mo: 2.2wt%, W: 8.2wt%, Ta: 6.8wt%, Al: 5.2wt%, Ti: 1.4wt%, N: 0.045wt%, and the balance is Ni.

[0121] The method for preparing the nickel-based single crystal high-temperature alloy of this embodiment comprises the following steps:

[0122] 1) A master alloy ingot having the above chemical composition is prepared by smelting in a vacuum induction furnace (wherein the refining temperature is 1550° C., the refining time is 40 minutes, and the vacuum degree during the refining period is ≤5 Pa).

[0123] 2) The master alloy ingot is grown into a single crystal in a high temperature gradient directional solidification furnace (growth rate is 5mm / min), and the spiral crystal selection method is used to make <001> Oriented single crystal test bar.

[0124] 3) The single crystal test rod is subjected to solution treatment and aging treatment to obtain a nickel-based single crystal high temperature alloy.

[0125] Among them, the solution treatment conditions are: 1290℃ / 2h+1295℃ / 2h+1300℃ / 4h, AC.

[0126] The aging treatment method is: 1080℃ / 6h, AC+870℃ / 24h, AC.

[0127] The chemical compositions of the nickel-based single crystal high-temperature alloys of Comparative Examples 3 and 4 are shown in Table 3.

[0128] Table 3 shows the chemical composition (wt%) of the nickel-based single crystal high temperature alloys of Comparative Examples 3 and 4.

[0129] alloy Cr Co Mo W Ta Al Ti Nb N Ni Comparative Example 3 7.1 8.3 2.2 8.2 6.8 5.2 1.4 0 0 Remain Comparative Example 4 7.1 8.3 2.2 8.2 6.8 5.2 1.4 0 0.045 Remain

[0130] The nitride morphology of the alloy in Comparative Example 4 is as follows Figure 5 As shown. And the present invention Figure 3 By comparison, it can be seen that: due to the higher N content in comparative example 4, the TiN preferentially grows along the (111) crystal plane, resulting in the nitride of comparative example 4 being needle-shaped with a length of about 20 μm. The long needle-shaped nitride will cause stress concentration inside the single crystal high-temperature alloy and damage the mechanical properties of the alloy.

[0131] The comparison of the durability of Comparative Example 4, Example 2 and Comparative Example 3 is as follows: Figure 6 As shown, it was found that: (1) the alloy of the present invention (the alloy of Example 2) can further improve the mechanical properties of the single crystal alloy; (2) excessive content of N element will be harmful to the mechanical properties of the alloy, and adding a small amount of N element will improve the mechanical properties of the alloy.

[0132] Comparative Example 5

[0133] Comparative Example 5 prepares a nickel-based single crystal high-temperature alloy. The difference from Example 1 is that Comparative Example 5 does not contain the Nb element, and the other parts are completely the same.

[0134] The chemical compositions of the nickel-based single crystal high-temperature alloys of Example 1 and Comparative Example 5 are shown in Table 4.

[0135] Table 4 shows the chemical composition (wt%) of the nickel-based single crystal high temperature alloys of Comparative Example 5 and Example 1.

[0136] alloy Cr Co Mo W Ta Al Ti Nb N Ni Example 1 6.8 8.3 2.6 7.3 5.7 5.5 1.1 0.6 0.009 Remain Comparative Example 5 6.8 8.3 2.6 7.3 5.7 5.5 1.1 0 0.009 Remain

[0137] The average size of the nitrides after heat treatment of the alloys in Comparative Example 5 and Example 1 is as follows: Figure 7 As shown. It can be seen that: since the alloy of comparative example 5 does not contain Nb element, the nitride is only TiN, so TiN will continue to grow with the diffusion of elements during casting and heat treatment. Therefore, the size of the nitride of comparative example 5 is slightly larger, which will aggravate the tendency of crack formation between TiN and the single crystal matrix while compensating for the solidification shrinkage cavity, thereby damaging the mechanical properties of the single crystal alloy.

[0138] Comparative Example 6

[0139] Comparative Example 6: A nickel-based single crystal high temperature alloy is prepared. The difference between Comparative Example 6 and Example 1 is that the heat treatment system is different, and the other conditions are completely the same. The heat treatment system of Comparative Example 6 is as follows:

[0140] The solution treatment conditions are as follows: heating to 1285°C at a heating rate of 15°C / min and keeping warm for 2 hours; then heating to 1295°C at a heating rate of 5°C / min and keeping warm for 3 hours; then heating to 1308°C at a heating rate of 5°C / min and keeping warm for 4 hours; after the insulation, air cooling to room temperature is completed.

[0141] The aging treatment method is as follows: heating to 1060°C at a heating rate of 60°C / min, keeping warm for 5 hours, air cooling to room temperature after the end of the heat preservation, and then heating to 860°C at a heating rate of 60°C / min and keeping warm for 24 hours, and air cooling to room temperature after the end of the heat preservation.

[0142] The γ and γ′ phase components of the alloys in Comparative Example 6 and Example 1 after heat treatment are as follows: Figure 8 It can be seen that: due to the excessively fast solid solution rate in Comparative Example 6, the elements of the single crystal alloy of the present invention diffuse unevenly, thereby reducing the strength of the γ phase and the γ′ phase, making its performance inferior to that of Example 1.

[0143] Comparative Example 7

[0144] Comparative Example 7 prepares a nickel-based single crystal high-temperature alloy. The difference from Example 1 is that the Ti element in Comparative Example 7 is not within the required scope of the present invention, and the others are completely the same.

[0145] The chemical compositions of the nickel-based single crystal high-temperature alloys of Example 1 and Comparative Example 7 are shown in Table 5.

[0146] Table 5 shows the chemical composition (wt%) of the nickel-based single crystal high temperature alloys of Comparative Example 7 and Example 1.

[0147] alloy Cr Co Mo W Ta Al Ti Nb N Ni Example 1 6.8 8.3 2.6 7.3 5.7 5.5 1.1 0.6 0.009 Remain Comparative Example 7 6.8 8.3 2.6 7.3 5.7 5.5 0.4 0.6 0.009 Remain

[0148] Here, since the alloy of Comparative Example 7 has a low Ti content, a low spherical TiN content, and a low Ti content dissolved in the γ' phase, the low spherical nitride content leads to insufficient shrinkage-feeding capacity of the alloy molten pool. At the same time, the low content of the main strengthening elements in the γ' phase leads to low γ' opposite phase domain boundary energy, poor dislocation barrier ability, and significantly damages the mechanical properties of the single crystal alloy. Fig. 9 : is a comparison chart of the high temperature creep life of the heat-treated alloys in Comparative Example 7 and Example 1; Fig. 9 It can be clearly seen that the mechanical properties of the heat-treated alloy of Comparative Example 7 are inferior to those of Example 1.

[0149] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A nickel-based single crystal high temperature alloy, characterized in that: In terms of mass percentage, it includes the following chemical components: Cr: 6-8wt%, Co: 7-9wt%, Mo: 1-3wt%, W: 7-9wt%, Ta: 5-7wt%, Al: 5-7wt%, Ti: 0.5-2wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni.

2. The nickel-based single crystal high-temperature alloy according to claim 1, characterized in that: In terms of mass percentage, it includes the following chemical components: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.5-1wt%, N: 0.008-0.013wt%, and the balance is Ni; Preferably, it includes the following chemical components in mass percentage: Cr: 6.7-7.5wt%, Co: 7.5-8.5wt%, Mo: 1.5-2.5wt%, W: 7.7-8.7wt%, Ta: 5.5-6.5wt%, Al: 5.5-6.5wt%, Ti: 1.4-1.8wt%, Nb: 0.6-0.8wt%, N: 0.009-0.011wt%, and the balance is Ni.

3. The nickel-based single crystal high temperature alloy according to claim 1 or 2, characterized in that: If the nickel-based single crystal high temperature alloy is a cast alloy, the dendrites of the nickel-based single crystal high temperature alloy have dispersedly distributed, approximately spherical TiN phases and NbN phases; preferably, the diameters of the TiN phases and NbN phases are 3-5 μm; If the nickel-based single crystal high-temperature alloy is a heat-treated alloy, the matrix phase of the nickel-based single crystal high-temperature alloy includes a γ phase and a γ′ phase, and the reinforcement phase is a dispersed, approximately spherical TiN phase and NbN phase; preferably, the diameter of the TiN phase and the NbN phase is 3-5 μm.

4. The nickel-based single crystal high temperature alloy according to any one of claims 1 to 3, characterized in that: If the nickel-based single crystal high temperature alloy is a cast alloy, the porosity of the nickel-based single crystal high temperature alloy is 0.05-0.15%; and / or If the nickel-based single crystal high temperature alloy is a heat-treated alloy, the porosity of the nickel-based single crystal high temperature alloy is 0.15-0.3%.

5. The nickel-based single crystal high temperature alloy according to any one of claims 1 to 4, characterized in that: The nickel-based single crystal high temperature alloy has a durability of 240 to 260 hours at 800±1°C and 750±1MPa; and / or The nickel-based single crystal high temperature alloy has a durability of 215 to 245 hours at 980±1°C and 250±1MPa; and / or The nickel-based single crystal high-temperature alloy has a durability of 115 to 135 hours under the conditions of 1100±1° C. and 137±1 MPa.

6. The method for preparing a nickel-based single crystal at high temperature according to any one of claims 1 to 5, characterized in that: It includes the following steps: Vacuum induction melting: vacuum induction melting produces a master alloy ingot of the desired chemical composition; Preparing a single crystal alloy: preparing the master alloy ingot into a single crystal alloy; Heat treatment: subjecting the single crystal alloy to solution treatment and aging treatment in sequence to obtain a nickel-based single crystal high temperature alloy; Preferably, during vacuum induction melting, the N element is added to the vacuum induction furnace in the form of CrN; Preferably, in the vacuum induction melting step, the refining temperature is 1550±10°C, the refining time is 30 to 50 minutes, and the vacuum degree during the refining period is ≤5Pa.

7. The method for preparing a nickel-based single crystal high-temperature alloy according to any one of claims 1 to 6, characterized in that: The step of solution treatment comprises: The single crystal alloy is heated to a first solid solution temperature at a first set heating rate, kept at the first solid solution temperature for a first time, heated to a second solid solution temperature at a second set heating rate, kept at the second solid solution temperature for a second time, heated to a third solid solution temperature at a third set heating rate, kept at the third solid solution temperature for a third time, and then cooled to room temperature to obtain a single crystal alloy after solid solution treatment; wherein the first solid solution temperature is 1285-1295°C, the second solid solution temperature is 1295-1305°C, and the third solid solution temperature is 1305-1310°C; the third solid solution temperature is greater than the second solid solution temperature; the second solid solution temperature is greater than the first solid solution temperature; the first set heating rate is 3-10°C / min; the second set heating rate is 1-3°C / min; the third set heating rate is 1-3°C / min; Preferably, the first time is 1 to 3 hours, the second time is 1 to 3 hours, and the third time is 3 to 6 hours.

8. The method for preparing a nickel-based single crystal high-temperature alloy according to claim 7, characterized in that: The aging treatment step includes: The single crystal high-temperature alloy after the solution treatment is heated to 1060-1090°C at a heating rate of 50-100°C / min, kept at this temperature for 4-8 hours, and then cooled to room temperature; then the temperature is further heated to 850-900°C at a heating rate of 50-100°C / min, kept at this temperature for 20-32 hours, and then cooled to room temperature to obtain a nickel-based single crystal high-temperature alloy.

9. A nickel-based single crystal high temperature alloy part, characterized in that: The nickel-based single crystal high-temperature alloy part is made of the single crystal high-temperature alloy described in any one of claims 1-5.

10. The nickel-based single crystal high-temperature alloy part according to claim 9, characterized in that: The nickel-based single crystal high-temperature alloy part is a low-pressure turbine blade or a high-pressure guide blade of an engine.

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