Method for eliminating interdendritic eutectic and / or holes of Ni3Al-based single crystal alloy

Abstract

The invention provides a method for eliminating interdendritic eutectic and / or holes of Ni3Al-based single crystal alloy, and belongs to the technical field of alloy repair. The method comprises the following steps: carrying out hot isostatic pressing treatment on the Ni3Al-based single crystal alloy to be repaired; the Ni3Al-based single crystal alloy to be repaired contains interdendritic eutectic and / or holes. According to the method, the to-be-repaired Ni3Al-based single crystal alloy is subjected to hot isostatic pressing treatment, the hot isostatic pressing technology is a heat treatment method combining high temperature and isostatic pressing, the compactness of the Ni3Al-based single crystal alloy can be remarkably improved by adopting the technology, the microscopic structure is uniform, and the mechanical property of the Ni3Al-based single crystal alloy is improved; on the basis, interdendritic eutectic and / or holes in the Ni3Al-based single crystal alloy can be simply and rapidly eliminated, so that the anti-fatigue performance and creep resistance of the alloy are remarkably improved, technical support is provided for service safety and prolonging of the service life of the alloy, for example, the replacement frequency of a Ni3Al-based single crystal alloy turbine guide blade can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy repair, in particular to a method for eliminating interdendritic eutectics and / or pores in a Ni3Al-based single crystal alloy. Background Art

[0002] Ni3Al-based single crystal alloys, due to their excellent high-temperature strength, creep resistance, and high specific strength, have been used in the manufacture of important structural and functional components such as aircraft engine turbine guide vanes. However, due to the influence of casting conditions and alloy composition, microporosity often forms during solidification. Furthermore, in the later stages of solidification, the segregation of low-melting-point elements can lead to the formation of brittle interdendritic eutectic structures, which can easily lead to stress concentration and ultimately form crack sources, seriously affecting the service life of Ni3Al-based single crystal alloy turbine guide vanes. Therefore, exploring methods to eliminate weak structures in Ni3Al-based single crystal alloys is of great scientific significance.

[0003] The traditional method for eliminating interdendritic eutectic structure is mainly solution heat treatment. However, due to the large number of elements in Ni3Al-based single crystal alloys and the severe segregation of cast elements, a long gradient solution heat treatment (i.e., multi-stage solution heat treatment) is often required. However, when gradient solution heat treatment is used, as the heat treatment time increases, solution micropores are easily formed in the alloy, seriously impairing the service performance of the alloy. Summary of the Invention

[0004] The object of the present invention is to provide a method for eliminating interdendritic eutectics and / or pores in Ni3Al-based single crystal alloys. The method of the present invention can simply and quickly eliminate interdendritic eutectics and / or pores (the pores include microporosity and / or solid solution micropores) in Ni3Al-based single crystal alloys, and can effectively improve the fatigue resistance and creep resistance of the alloy.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for eliminating interdendritic eutectics and / or pores in a Ni3Al-based single crystal alloy, comprising the following steps:

[0007] The Ni3Al-based single crystal alloy to be repaired is subjected to hot isostatic pressing treatment; the Ni3Al-based single crystal alloy to be repaired contains interdendritic eutectics and / or pores.

[0008] Preferably, the Ni3Al-based single crystal alloy to be repaired comprises the following elements, in percentage by mass: Mo 7-12%, Re 0-2%, Cr 1-3%, Hf0.5-1.0%, Al 6-9%, Ta2-3.5%, C 0.05-0.10%, B0.003-0.01%, and Ni balance; the volume fraction of the interdendritic eutectic in the Ni3Al-based single crystal alloy to be repaired is 5-10%, and the porosity is 0.005-0.025%.

[0009] Preferably, the Ni3Al-based single crystal alloy to be repaired is a cast single crystal alloy obtained by gradient solution heat treatment; the temperature of the gradient solution heat treatment is greater than the γ′ dissolution temperature and less than the solidus temperature.

[0010] Preferably, the gradient solution heat treatment includes: heating to 1300±2°C and keeping warm for 2 hours; then heating to 1305±2°C and keeping warm for 2 hours; then heating to 1310±2°C and keeping warm for 2 hours; then heating to 1315±2°C and keeping warm for 2 hours; then heating to 1325±2°C and keeping warm for 2 hours; then heating to 1330±2°C and keeping warm for 4 hours; then heating to 1335±2°C and keeping warm for 6 hours; and finally air cooling.

[0011] Preferably, the Ni3Al-based single crystal alloy to be repaired is a cast single crystal alloy obtained by rapid solution heat treatment; the temperature of the rapid solution heat treatment is greater than the initial melting temperature and less than the solidus temperature, and the holding time is 4 to 6 hours.

[0012] Preferably, the rapid solution heat treatment comprises: heating to 1330±10° C., keeping the temperature for 4 hours, and then air cooling.

[0013] Preferably, the Ni3Al-based single crystal alloy to be repaired is a Ni3Al-based single crystal alloy turbine guide blade containing interdendritic eutectic and / or pores.

[0014] Preferably, the temperature of the hot isostatic pressing treatment is greater than the γ′ re-dissolution temperature and less than the solidus temperature, the pressure is 100-160 MPa, and the heat and pressure holding time is 3-8 hours.

[0015] Preferably, the temperature of the hot isostatic pressing treatment is 1330±5°C, the pressure is 160 MPa, and the heat preservation and pressure holding time is 3 to 8 hours.

[0016] Preferably, the hot isostatic pressing treatment is performed in a protective atmosphere.

[0017] The present invention provides a method for eliminating interdendritic eutectics and / or pores in a Ni3Al-based single crystal alloy, comprising the following steps: subjecting the Ni3Al-based single crystal alloy to be repaired to hot isostatic pressing (HIP); wherein the Ni3Al-based single crystal alloy to be repaired contains interdendritic eutectics and / or pores. The present invention subjects the Ni3Al-based single crystal alloy to hot isostatic pressing (HIP). Hot isostatic pressing (HIP) is a heat treatment method that combines high temperature and isostatic pressing. The present invention utilizes this technology to significantly improve the compactness of the Ni3Al-based single crystal alloy and achieve a uniform microstructure. Based on this, the elimination of interdendritic eutectics and the closure of pores in the Ni3Al-based single crystal alloy can be achieved simply and quickly, thereby significantly improving the alloy's fatigue resistance and creep resistance, providing technical support for service safety and extending the alloy's service life. For example, the HIP can effectively reduce the frequency of replacement of Ni3Al-based single crystal alloy turbine guide blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a three-dimensional rendering of the holes of the standard heat-treated alloy in Example 1;

[0019] Figure 2 This is the pore size distribution diagram of the standard heat-treated alloy in Example 1;

[0020] Figure 3 These are four views of the Ni3Al-based single crystal alloy after repair in Example 1;

[0021] Figure 4 The microstructures of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1 are shown;

[0022] Figure 5 This is a comparison chart of the spinning bending fatigue properties of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy at 800°C in Example 1;

[0023] Figure 6 This is a comparison chart of the rupture performance of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1 at 1100°C / 120MPa;

[0024] Figure 7 3A is a microstructure diagram of the Ni3Al-based single crystal alloy to be repaired and the repaired Ni3Al-based single crystal alloy in Example 2;

[0025] Figure 8 Four views of the Ni3Al-based single crystal alloy after repair in Example 2;

[0026] Figure 9 3. This is a comparison chart of the rotational bending fatigue properties of the Ni3Al-based single crystal alloy to be repaired and the repaired Ni3Al-based single crystal alloy at 800°C in Example 2;

[0027] Figure 10 This is a comparison chart of the endurance performance of the Ni3Al-based single crystal alloy to be repaired and the repaired Ni3Al-based single crystal alloy under 1100°C / 120MPa conditions in Example 2. DETAILED DESCRIPTION

[0028] The present invention provides a method for eliminating interdendritic eutectics and / or pores in a Ni3Al-based single crystal alloy, comprising the following steps:

[0029] The Ni3Al-based single crystal alloy to be repaired is subjected to hot isostatic pressing treatment; the Ni3Al-based single crystal alloy to be repaired contains interdendritic eutectics and / or pores.

[0030] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art or are prepared using methods well known to those skilled in the art.

[0031] The method of the present invention can be used to repair a Ni3Al-based single crystal alloy containing interdendritic eutectics and / or pores (i.e., a Ni3Al-based single crystal alloy to be repaired), thereby eliminating the interdendritic eutectics and / or pores. As one embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired comprises the following elements, in percentage by mass: Mo 7-12%, Re 0-2%, Cr 1-3%, Hf 0.5-1.0%, Al 6-9%, Ta 2-3.5%, C 0.05-0.10%, B 0.003-0.01%, and the balance Ni. In an embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired comprises the following elements, measured in percentage by mass: Mo 7-10%, Re 0.5-2%, Cr 1-2%, Hf 0.5-1.0%, Al 6-7%, Ta 2-3.5%, C 0.05-0.10%, B 0.003-0.01%, and the balance Ni. As one embodiment of the present invention, the volume fraction of the interdendritic eutectic in the Ni3Al-based single crystal alloy to be repaired is 5-10%, and may further be 7-9%; the porosity is 0.005-0.025%, and may further be 0.01-0.02%. As one embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired is a high-γ' alloy, and the volume fraction of the γ' phase in the Ni3Al-based single crystal alloy to be repaired is ≥70%.

[0032] As an embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired can be a cast single crystal alloy obtained by gradient solution heat treatment; the temperature (T) of the gradient solution heat treatment is greater than the γ′ dissolution temperature and less than the solidus temperature, that is, the γ′ dissolution temperature <T < solidus temperature. As an embodiment of the present invention, the gradient solution heat treatment includes: heating to 1300±2°C, keeping warm for 2 hours; then heating to 1305±2°C, keeping warm for 2 hours; then heating to 1310±2°C, keeping warm for 2 hours; then heating to 1315±2°C, keeping warm for 2 hours; then heating to 1325±2°C, keeping warm for 2 hours; then heating to 1330±2°C, keeping warm for 4 hours; then heating to 1335±2°C, keeping warm for 6 hours; and finally air cooling. In an embodiment of the present invention, the gradient solution heat treatment includes: heating to 1300°C and keeping warm for 2 hours; then heating to 1305°C and keeping warm for 2 hours; then heating to 1310°C and keeping warm for 2 hours; then heating to 1315°C and keeping warm for 2 hours; then heating to 1320°C and keeping warm for 2 hours; then heating to 1325°C and keeping warm for 2 hours; then heating to 1330°C and keeping warm for 4 hours; then heating to 1335°C and keeping warm for 6 hours; and finally air cooling. In order to avoid the formation of interdendritic eutectic (i.e., initial melting spot) in the above-mentioned gradient solution heat treatment, the operation time is relatively long, but long-term heat treatment makes it easy to form holes in the Ni3Al-based single crystal alloy. The method of the present invention can repair the Ni3Al-based single crystal alloy after the gradient solution heat treatment so that the holes are completely closed. In an embodiment of the present invention, the equipment used for the gradient solution heat treatment is a tubular furnace.

[0033] As an embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired can be a cast single crystal alloy obtained by rapid solution heat treatment; the temperature (T) of the rapid solution heat treatment is greater than the initial melting temperature and less than the solidus temperature, that is, the initial melting temperature <T < solidus temperature; the holding time of the rapid solution heat treatment is 4 to 6 hours. As an embodiment of the present invention, the rapid solution heat treatment includes: heating to 1330±10°C, keeping warm for 4 hours, and then air cooling. In an embodiment of the present invention, the rapid solution heat treatment includes: heating to 1335°C, keeping warm for 4 hours, and then air cooling. The above-mentioned rapid solution heat treatment directly carries out a one-step heat preservation treatment under higher temperature conditions, and the operation time is shorter. However, carrying out the heat preservation treatment directly under higher temperature conditions will lead to overheating, that is, it is easy to form interdendritic eutectic (i.e., initial melting spot) in Ni3Al-based single crystal alloy, and there will also be holes (including micro-porosity and / or solid solution micropores). The method of the present invention can repair Ni3Al-based single crystal alloy after rapid solution heat treatment, eliminate the initial melting spot formed by overheating, and close the micro-porosity and solid solution micropores present in the alloy. Therefore, the method of the present invention does not need to adopt traditional gradient solution heat treatment, but can directly subject the cast single crystal alloy to rapid solution heat treatment and hot isostatic pressing treatment in sequence to efficiently prepare high-performance Ni3Al-based single crystal alloy. In an embodiment of the present invention, the equipment used for the rapid solution heat treatment is a tubular furnace.

[0034] As an embodiment of the present invention, the method for preparing the cast single crystal alloy used in the above technical solution includes the following steps: preparing the cast single crystal alloy according to the composition of the Ni3Al-based single crystal alloy, and preparing the cast single crystal alloy by the seed crystal method after refining and casting. The present invention does not specifically limit the conditions of the refining and casting, and the conditions familiar to those skilled in the art can be used. As an embodiment of the present invention, the conditions for preparing the cast single crystal alloy by the seed crystal method include: a pulling rate of 4 to 4.5 mm / min, specifically 4.3 mm / min; a casting temperature of 1530 to 1550°C, and further 1530 to 1540°C.

[0035] As an embodiment of the present invention, the Ni3Al-based single crystal alloy to be repaired may be a Ni3Al-based single crystal alloy turbine guide blade containing interdendritic eutectic and / or pores.

[0036] After obtaining the Ni3Al-based single crystal alloy to be repaired, the present invention performs hot isostatic pressing on the Ni3Al-based single crystal alloy to be repaired. As one embodiment of the present invention, the temperature (T) of the hot isostatic pressing treatment is greater than the γ′ dissolution temperature and less than the solidus temperature, that is, the γ′ dissolution temperature <T < solidus temperature; the pressure of the hot isostatic pressing treatment can be 100-160MPa, specifically 100MPa, 110MPa, 120MPa, 130MPa, 140MPa, 150MPa or 160MPa; the heat preservation and pressure holding time of the hot isostatic pressing treatment can be 3-8h, specifically 3h, 4h, 5h, 6h, 7h or 8h. In an embodiment of the present invention, the temperature of the hot isostatic pressing treatment is 1330±5℃, the pressure is 160MPa, and the heat preservation and pressure holding time is 4-8h. As one embodiment of the present invention, the hot isostatic pressing treatment is carried out in a protective atmosphere, and the protective atmosphere can be argon. In an embodiment of the present invention, the equipment used for the hot isostatic pressing treatment is a hot isostatic pressing furnace.

[0037] The present invention subjects the Ni3Al-based single crystal alloy to be repaired to hot isostatic pressing to obtain a repaired Ni3Al-based single crystal alloy, which does not contain interdendritic eutectic and does not contain pores (including microporosity and solid solution micropores), and has a porosity of 0; and the matrix structure of the repaired Ni3Al-based single crystal alloy is a two-phase structure of γ′ and γ, and the size and morphology of the γ′ phase are basically consistent with those of the Ni3Al-based single crystal alloy to be repaired; in addition, the repaired Ni3Al-based single crystal alloy has excellent fatigue resistance and creep resistance. The fatigue limit of the repaired Ni3Al-based single crystal alloy at 800°C is 400-458MPa, which can be at least 100-2000MPa under the same stress conditions compared to the Ni3Al-based single crystal alloy to be repaired. 6 Weekly increase to 10 7 cycles, that is, an order of magnitude higher; compared with the Ni3Al-based single crystal alloy to be repaired, the endurance life of the repaired Ni3Al-based single crystal alloy at a temperature of 1100°C and a stress of 120 MPa can be increased by 69 to 136%.

[0038] In order to achieve complete homogenization of the alloy structure, traditional solution heat treatment usually uses a gradient solution heat treatment method with complex steps to increase the initial melting temperature. However, holes are easily generated during the gradient solution heat treatment process. The hole defects mainly come from the pores formed by the incomplete escape of gas during the solidification of the alloy and the micro-porosity caused by poor shrinkage compensation. In addition, the temperature control accuracy of the three types of furnaces commonly used in industrial production is ±10°C. However, due to the narrow window of heat treatment of Ni3Al-based single crystal alloys, that is, the temperature control accuracy requirements are high, overheating is prone to occur, resulting in initial melting and the formation of initial melting spots that cannot be eliminated, thereby affecting the high-temperature mechanical properties of the alloy and even causing parts to be scrapped. The method of the present invention can eliminate the initial melting spots and close the holes of Ni3Al-based single crystal alloys after traditional gradient solution heat treatment or Ni3Al-based single crystal alloys that have been initially melted, and can effectively improve the fatigue resistance and creep resistance of the alloy.

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] In terms of mass percentage, the Ni3Al-based single crystal alloy in the following embodiments includes the following elements: Mo 7-10%, Re 0.5-2%, Cr 1-2%, Hf 0.5-1.0%, Al 6-7%, Ta 2-3.5%, C 0.05-0.10%, B 0.003-0.01%, and Ni as the balance.

[0041] Example 1

[0042] This embodiment repairs the Ni3Al-based single crystal alloy to be repaired (specifically, eliminates the holes therein), including the following steps:

[0043] According to the composition of Ni3Al-based single crystal alloy, after refining and casting, the cast single crystal alloy was prepared by seed crystal method (with a pulling rate of 4.3 mm / min and a casting temperature of 1530°C).

[0044] The cast single crystal alloy is subjected to a gradient solution heat treatment (the equipment used is a tube furnace) to obtain a Ni3Al-based single crystal alloy to be repaired (also known as a standard heat-treated alloy); the gradient solution heat treatment comprises: heating from room temperature (25°C) to 1300°C, holding for 2 hours; then heating to 1305°C, holding for 2 hours; then heating to 1310°C, holding for 2 hours; then heating to 1315°C, holding for 2 hours; then heating to 1320°C, holding for 2 hours; then heating to 1325°C, holding for 2 hours; then heating to 1330°C, holding for 4 hours; then heating to 1335°C, holding for 6 hours; then air cooling;

[0045] The Ni3Al-based single crystal alloy to be repaired is subjected to hot isostatic pressing treatment (the equipment used is a hot isostatic pressing furnace) to obtain the repaired Ni3Al-based single crystal alloy; the hot isostatic pressing treatment includes: heating from room temperature to 1330±5°C in an argon atmosphere, setting the pressure to 160MPa, keeping the temperature at room temperature and holding the pressure for 4h, and then cooling with the furnace.

[0046] Figure 1 This is a three-dimensional rendering of the pores of the standard heat-treated alloy in Example 1. The results show that a large number of micropores exist inside the standard heat-treated alloy obtained after gradient solution heat treatment.

[0047] Figure 2 The pore size distribution diagram of the standard heat-treated alloy in Example 1 shows that the standard heat-treated alloy obtained after gradient solution heat treatment has larger pores, with the volume of the largest pore being 5.94×10 4 μm 3 , the sphericity is 0.494.

[0048] Figure 3 These are four views of the Ni3Al-based single crystal alloy after repair in Example 1. The results show that the pores in the standard heat-treated alloy are completely closed after hot isostatic pressing.

[0049] Figure 4 Figure 1 shows the microstructures of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1, where a) is the microstructure of the standard heat-treated alloy and b) is the microstructure of the repaired Ni3Al-based single crystal alloy. The results show that the matrix structure of the repaired Ni3Al-based single crystal alloy is a two-phase structure of γ′ and γ, and the size and morphology of the γ′ phase are basically consistent with those of the standard heat-treated alloy.

[0050] Table 1 shows the comparison of the pores in the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1. The results show that after hot isostatic pressing, the pores in the alloy are completely eliminated and the porosity is 0.

[0051] Table 1 Comparison of holes in standard heat-treated alloy and repaired Ni3Al-based single crystal alloy in Example 1

[0052] holes Standard heat-treated alloy <![CDATA[Ni3Al-based single crystal alloy after repair]]> Number of holes 900 0 Porosity (%) 0.01 0

[0053] Figure 5 This is a comparison of the spinning-bending fatigue properties of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1 at 800°C. Specifically, the fatigue limit of the sample was measured by the lifting and lowering method with an initial stress value set. The experimental temperature was 800°C, the waveform was a sine wave, the stress ratio was -1, and the rotation speed was 5000 r / min. Figure 5 Here, SHT refers to the standard heat-treated alloy, and HIP refers to the repaired Ni3Al-based single crystal alloy. The results show that after hot isostatic pressing (HIP), the fatigue limit of the alloy at 800°C increased from 354 MPa to 458 MPa.

[0054] Figure 6 This is a comparison chart of the endurance performance of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy in Example 1 at 1100°C / 120MPa. Specifically, the temperature was measured at the upper, middle, and lower points. The sample underwent a heating-holding-loading-fracture process. After reaching the target temperature, the sample was held for 10 minutes before loading began. The test data acquisition frequency was 5 minutes. -1 ; Figure 6 Here, SHT refers to the standard heat-treated alloy, and HIP refers to the repaired Ni3Al-based single crystal alloy. The results show that at a temperature of 1100°C and a stress of 120 MPa, the stress-rupture life of the standard heat-treated alloy and the repaired Ni3Al-based single crystal alloy was 52.5 hours and 88.9 hours, respectively. This indicates that the HIP treatment increased the stress-rupture life by 69%.

[0055] Example 2

[0056] This embodiment repairs the Ni3Al-based single crystal alloy to be repaired (specifically, eliminates the pores and the interdendritic eutectic, i.e., the initial melting spot), including the following steps:

[0057] According to the composition of Ni3Al-based single crystal alloy, after refining and casting, the cast single crystal alloy was prepared by seed crystal method (with a pulling rate of 4.3 mm / min and a casting temperature of 1530°C).

[0058] The as-cast single crystal alloy is subjected to a rapid solution treatment (using a tube furnace) to obtain a Ni3Al-based single crystal alloy to be repaired; the rapid solution treatment comprises: heating from room temperature to 1335°C, holding for 4 hours, and then air cooling;

[0059] The Ni3Al-based single crystal alloy to be repaired is subjected to hot isostatic pressing (the equipment used is a hot isostatic pressing furnace) to obtain the repaired Ni3Al-based single crystal alloy; the hot isostatic pressing treatment includes: heating from room temperature to 1330±5°C, setting the pressure to 160MPa, keeping the temperature and pressure for 8h, and then cooling with the furnace.

[0060] Figure 7 Figures 2 and 3 show the microstructures of the Ni3Al-based single crystal alloy to be repaired and after repair in Example 2, with a) showing the microstructure of the Ni3Al-based single crystal alloy to be repaired and b) showing the microstructure of the Ni3Al-based single crystal alloy after repair. The results show that the Ni3Al-based single crystal alloy to be repaired in Example 2 has a typical incipient melt structure, with numerous incipient melt spots and pores formed between the dendrites. After hot isostatic pressing, the alloy structure recovers and the pores are eliminated.

[0061] Figure 8 These are four views of the repaired Ni3Al-based single crystal alloy in Example 2. The results show that after the repaired Ni3Al-based single crystal alloy is subjected to hot isostatic pressing, the porosity is 0 and the structure is basically restored to the original structure.

[0062] Figure 9 This is a comparison chart of the rotational bending fatigue properties of the Ni3Al-based single crystal alloy to be repaired and the repaired Ni3Al-based single crystal alloy at 800°C in Example 2. The results show that after hot isostatic pressing treatment, the fatigue limit of the alloy at 800°C is increased from 318MPa to 400MPa.

[0063] Figure 10 This is a comparison chart of the endurance performance of the Ni3Al-based single crystal alloy to be repaired and the repaired Ni3Al-based single crystal alloy under 1100°C / 120MPa conditions in Example 2. The results show that under the conditions of temperature of 1100°C and stress of 120MPa, the endurance life of the standard heat-treated alloy and the repaired alloy is 27.2h and 64.2h, respectively. That is, after the alloy is subjected to hot isostatic pressing treatment, the endurance life is increased by 136%.

[0064] The above results demonstrate that, compared to conventional gradient solution heat treatment methods, the present method can simply and rapidly eliminate harmful microstructures such as interdendritic eutectics and pores in Ni3Al-based single crystal alloys. After hot isostatic pressing (HIP), the size and morphology of the γ′ phase in the alloy remain essentially the same as before HIP. The large amount of interdendritic eutectics in the alloy is completely removed, while also closing the microporosity generated during casting and the solution micropores formed during solution heat treatment, achieving a nearly fully dense (zero porosity) alloy. Furthermore, after HIP, the fatigue and creep resistance of the alloy are significantly improved. Therefore, the present method effectively addresses the issues of long eutectic solution times, the inability to eliminate initial molten spots after formation, and poor fatigue and creep resistance in high-γ′ alloys (γ′ volume fraction ≥ 70%). It has broad application value, particularly in the preparation and repair of Ni3Al-based single crystal alloy turbine guide blades.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for eliminating interdendritic eutectics and / or pores in Ni3Al-based single crystal alloys, characterized in that: The following steps are involved: The Ni3Al-based single crystal alloy to be repaired is subjected to hot isostatic pressing treatment; the Ni3Al-based single crystal alloy to be repaired contains interdendritic eutectics and / or pores.

2. The method according to claim 1, characterized in that Calculated by mass percentage, the Ni3Al-based single crystal alloy to be repaired includes the following elements: Mo 7-12%, Re 0-2%, Cr 1-3%, Hf 0.5-1.0%, Al 6-9%, Ta 2-3.5%, C 0.05-0.10%, B 0.003-0.01%, and Ni balance; the volume fraction of the interdendritic eutectic in the Ni3Al-based single crystal alloy to be repaired is 5-10%, and the porosity is 0.005-0.025%.

3. The method according to claim 2, characterized in that The Ni3Al-based single crystal alloy to be repaired is a cast single crystal alloy obtained by gradient solution heat treatment; the temperature of the gradient solution heat treatment is greater than the γ′ dissolution temperature and less than the solidus temperature.

4. The method according to claim 3, characterized in that The gradient solution heat treatment includes: heating to 1300±2°C and keeping warm for 2 hours; then heating to 1305±2°C and keeping warm for 2 hours; then heating to 1310±2°C and keeping warm for 2 hours; then heating to 1315±2°C and keeping warm for 2 hours; then heating to 1325±2°C and keeping warm for 2 hours; then heating to 1330±2°C and keeping warm for 4 hours; then heating to 1335±2°C and keeping warm for 6 hours; and finally air cooling.

5. The method according to claim 2, characterized in that The Ni3Al-based single crystal alloy to be repaired is a cast single crystal alloy obtained by rapid solution heat treatment; the temperature of the rapid solution heat treatment is greater than the initial melting temperature and less than the solidus temperature, and the holding time is 4 to 6 hours.

6. The method according to claim 5, characterized in that The rapid solution heat treatment includes: heating to 1330±10° C., keeping the temperature for 4 hours, and then air cooling.

7. The method according to any one of claims 1 to 6, characterized in that The Ni3Al-based single crystal alloy to be repaired is a Ni3Al-based single crystal alloy turbine guide blade containing interdendritic eutectic and / or pores.

8. The method according to any one of claims 1 to 6, characterized in that The temperature of the hot isostatic pressing treatment is greater than the γ′ re-dissolution temperature and less than the solidus temperature, the pressure is 100-160 MPa, and the heat and pressure holding time is 3-8 hours.

9. The method according to claim 8, characterized in that The temperature of the hot isostatic pressing treatment is 1330±5° C., the pressure is 160 MPa, and the heat preservation and pressure holding time is 3 to 8 hours.

10. The method according to claim 9, characterized in that The hot isostatic pressing treatment is carried out in a protective atmosphere.

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