Method for reducing residual stress of high-temperature alloy by hot isostatic pressing

Abstract

The application provides a method for reducing residual stress of an additive manufacturing high-temperature alloy based on hot isostatic pressing, which comprises the following steps: 1) placing the additive manufacturing high-temperature alloy into a hot isostatic pressing furnace, performing vacuum pumping, and stopping the vacuum pump when the vacuum degree is 10 ‑3 -10 ‑4 Pa; introducing inert gas into the hot isostatic pressing furnace, and heating the additive manufacturing high-temperature alloy to a first preset hot isostatic pressing temperature; 2) keeping the additive manufacturing high-temperature alloy at the first preset hot isostatic pressing temperature and a first pressure for a first preset holding time; then heating the additive manufacturing high-temperature alloy to a second preset hot isostatic pressing temperature, and keeping the additive manufacturing high-temperature alloy at the second preset hot isostatic pressing temperature and a second pressure for a second preset holding time; and obtaining the high-temperature alloy after cooling treatment. The application can significantly reduce the residual stress of the additive manufacturing high-temperature alloy, effectively reduce the internal micropores of the additive manufacturing high-temperature alloy, and make the alloy have higher high-temperature mechanical properties and toughness and good microstructure stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing technology, in particular to a method for reducing residual stress of high-temperature alloy by hot isostatic pressing. BACKGROUND

[0002] Laser additive manufacturing technology is a very convenient flexible manufacturing means. At present, laser additive manufacturing mainly focuses on titanium alloy, nickel-based high-temperature alloy and other materials. Compared with traditional processing technology, laser additive manufacturing technology has the characteristics of no need for part blank preparation, high material utilization rate, small machining allowance, short production and manufacturing cycle, etc.

[0003] High-temperature alloy has become the first choice for advanced aerospace engine high-temperature structural parts due to its excellent mechanical properties and temperature resistance. However, due to the high strength of high-temperature alloy, internal and external micropores and microcracks are easily generated during additive manufacturing process, and there is a large residual stress, which easily leads to part cracking during service and heat treatment. At present, the effect of reducing the residual stress of parts by optimizing the additive manufacturing process is very limited, and heat treatment is also an effective means to reduce the residual stress of high-temperature alloy by additive manufacturing.

[0004] Based on the above background, it is of great significance to develop a method for reducing the residual stress of high-temperature alloy parts based on hot isostatic pressing for the popularization and application of additive manufacturing of high-temperature alloy. SUMMARY

[0005] Therefore, the present application provides a method for reducing the residual stress of high-temperature alloy by additive manufacturing based on hot isostatic pressing, which mainly aims to make the high-temperature alloy have lower internal micropores and cracks, and at the same time have higher mechanical properties.

[0006] In order to achieve the above purpose, the present application mainly provides the following technical scheme:

[0007] On the one hand, the embodiment of the present application provides a method for reducing the residual stress of high-temperature alloy by additive manufacturing based on hot isostatic pressing, which comprises the following steps:

[0008] 1) Put the additive manufacturing high-temperature alloy into a hot isostatic pressing furnace, vacuumize, and when the vacuum degree is 10 -3 -10 -4 Pa: close the vacuum pump, introduce inert gas into the hot isostatic pressing furnace, and heat the additive manufacturing high-temperature alloy to a first preset hot isostatic pressing temperature;

[0009] 2) heat the additive manufacturing high-temperature alloy to a first preset hot isostatic pressing temperature and a first pressure, and keep the temperature for a first set time; then heat the additive manufacturing high-temperature alloy to a second preset hot isostatic pressing temperature, and keep the temperature for a second set time at the second preset hot isostatic pressing temperature and a second pressure, so that the additive manufacturing high-temperature alloy recrystallizes; after the cooling treatment, a high-temperature alloy treated by hot isostatic pressing is obtained.

[0010] Preferably, the additive manufacturing high-temperature alloy is a nickel-based high-temperature alloy with a volume fraction of γ' phase > 50%.

[0011] Preferably, in the step 1), the additive manufacturing high-temperature alloy is heated first at a heating rate of 5-15℃ / min to a set temperature, and then at a heating rate of 1-3℃ / min to the first preset hot isostatic pressing temperature; wherein the set temperature is 30±3℃ lower than the first preset hot isostatic pressing temperature.

[0012] Preferably, in the step 1), the inert gas has a purity ≥ 99.999%, an oxygen content ≤ 5ppm, and a total carbon content ≤ 10ppm; and / or the inert gas is argon.

[0013] Preferably, in the step 2), the first preset hot isostatic pressing temperature is 1100-1150℃, the first pressure is 10±3MPa, and the first holding time is 0.5±0.1h.

[0014] Preferably, in the step 2), the second preset hot isostatic pressing temperature is 1200-1280℃, the second pressure is 150-180MPa, and the second holding time is 2-3h.

[0015] Preferably, in the step 2), the additive manufacturing high-temperature alloy is heated from the first preset hot isostatic pressing temperature to the second preset hot isostatic pressing temperature at a heating rate of 5-10℃ / min.

[0016] Preferably, in the step 2), during the cooling treatment, the cooling rate is controlled to be within 15℃ / min; preferably, during the cooling treatment, the inert gas in the hot isostatic pressing furnace is extracted at a rate of 5-6L / min.

[0017] Preferably, the proportion of small-angle grain boundaries and large-angle grain boundaries in the additive manufacturing high-temperature alloy is (1±0.5):(1:±0.5); and / or the proportion of small-angle grain boundaries and large-angle grain boundaries in the high-temperature alloy treated by hot isostatic pressing is (1±0.5):(9±0.5).

[0018] In still another aspect, the embodiments of the present application provide a high-temperature alloy after hot isostatic pressing, wherein the high-temperature alloy after hot isostatic pressing is a nickel-based high-temperature alloy; wherein the ratio of small-angle grain boundaries and large-angle grain boundaries in the high-temperature alloy after hot isostatic pressing is (1±0.5):(9±0.5); preferably, the high-temperature alloy after hot isostatic pressing is obtained by hot isostatic pressing of the high-temperature alloy by any one of the methods for reducing residual stress of high-temperature alloy by hot isostatic pressing based on additive manufacturing according to the embodiments of the present application;

[0019] Preferably, the chemical composition of the nickel-based high-temperature alloy comprises, in percentage by weight:

[0020] Al: 4-5 wt%,

[0021] Co: 7-9 wt%,

[0022] Cr: 9-11 wt%,

[0023] Mo+Ta+W: 14-20 wt%;

[0024] Ti: 0-2 wt%;

[0025] B: 0-0.02 wt%;

[0026] C: 0.01-0.03 wt%;

[0027] Ni: balance.

[0028] Compared with the prior art, the method for reducing residual stress of high-temperature alloy by hot isostatic pressing based on additive manufacturing of the present application has at least the following beneficial effects:

[0029] The embodiments of the present application provide a method for reducing residual stress of high-temperature alloy by hot isostatic pressing based on additive manufacturing, which first puts the high-temperature alloy by additive manufacturing into a hot isostatic pressing furnace, evacuates, and when the vacuum degree is 10 -3 -10 -4Pa time: the vacuum pump is closed, inert gas is introduced into the hot isostatic pressing furnace, the additive manufacturing high-temperature alloy is heated to a first preset hot isostatic pressing temperature, then the additive manufacturing high-temperature alloy is kept at the first preset hot isostatic pressing temperature and a first pressure for a first set time, then the additive manufacturing high-temperature alloy is heated to a second preset hot isostatic pressing temperature, and kept at the second preset hot isostatic pressing temperature and a second pressure for a second set time, so that the additive manufacturing high-temperature alloy recrystallizes, and after cooling treatment, the high-temperature alloy after hot isostatic pressing treatment is obtained. It should be noted that the method of the present application is based on the dissolution of the strengthening phase of the high-temperature alloy into the matrix under high-temperature conditions, the decrease of the high-temperature strength of the alloy, the recrystallization of the alloy by using the residual stress in the additive manufacturing high-temperature alloy, and the formation of the crystal. The recrystallization process not only reduces the residual stress in the additive manufacturing alloy, but also migrates the grain boundary during the migration process. The large internal micropore can be reduced, which is beneficial to the closure of the internal micropore and microcrack during hot isostatic pressing. Thus, it is beneficial to improve the mechanical properties of the additive manufacturing alloy. At the same time, since the volume fraction of the gamma prime phase of the nickel-based high-temperature alloy is high, the content of aluminum in the alloy is high, and if the vacuum degree is not controlled well, an oxide film is easily formed at the crack position, which is not conducive to the formation of recrystallization. Therefore, in order to facilitate the formation of recrystallization, the present application adopts the method of first reaching a high level of vacuum, then heating the alloy, and more strictly controlling the oxygen content in the inert gas (preferably high-purity argon, the purity is ≥99.999%, the oxygen content is ≤5ppm, the total carbon content is ≤10ppm, and other impurities such as nitrogen and water are not required. Oxygen is easy to cause slight oxidation of the crack, which is not conducive to healing. Carbon will cause the formation of carbides in the alloy, which is not conducive to healing).

[0030] Further, the method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing provided by the embodiment of the present application mainly processes nickel-based high-temperature alloy with a volume fraction of gamma prime phase > 50%. This is because this type of high-temperature alloy has high strength and is prone to cracks and internal pores during the additive manufacturing process. The method of the present application can well solve these problems.

[0031] Further, the method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing provided by the embodiment of the present application controls the heating rate to be 10±5℃ / min when heating the alloy, and then adjusts the heating rate to 1℃ / min when the temperature of the alloy is 30℃ different from the first preset hot isostatic pressing temperature. This setting is to prevent the oxidation of the crack part of the alloy during the heating process, which is not conducive to the healing of the crack, and the lower heating rate also helps to reduce part of the stress and prevent cracking.

[0032] Further, the embodiment of the present application provides a method for reducing residual stress of high-temperature alloy manufactured by additive manufacturing based on hot isostatic pressing. The high-temperature alloy manufactured by additive manufacturing is kept at 1100-1150 ℃ and 10 MPa for 0.5 h, then heated to 1200-1280 ℃ at a rate of 5-10 ℃ / min, and kept at 1200-1280 ℃ and 150-180 MPa for 2-3 h, so as to ensure complete recrystallization in the alloy and release of residual stress in the sample.

[0033] In summary, the method for reducing residual stress of high-temperature alloy manufactured by additive manufacturing based on hot isostatic pressing has the advantages of reasonable design, simple operation process and low cost. The method can significantly reduce the residual stress of high-temperature alloy manufactured by additive manufacturing, improve the density of the alloy and the mechanical properties of the alloy, thereby reducing the cost of high-temperature alloy parts manufactured by additive manufacturing. In summary, the method solves the problems of high residual stress of high-temperature alloy manufactured by additive manufacturing and easy cracking during service, and improves the yield of high-temperature alloy parts manufactured by additive manufacturing.

[0034] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application and to implement the content of the description, the following will describe the preferred embodiments of the present application in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a residual stress comparison diagram of the as-deposited alloy and the alloy after the treatment of the embodiment.

[0036] Figure 2 is an optical photograph of the additive manufactured nickel-based high-temperature alloy in Example 1 and the nickel-based high-temperature alloy after hot isostatic pressing treatment.

[0037] Figure 3 is an electron backscatter diffraction pattern of the additive manufactured nickel-based high-temperature alloy in Example 1 and the nickel-based high-temperature alloy after hot isostatic pressing treatment.

[0038] Figure 4 is an electron backscatter diffraction pattern of the additive manufactured nickel-based high-temperature alloy in Example 2 and the nickel-based high-temperature alloy after hot isostatic pressing treatment.

[0039] Figure 5 is an electron backscatter diffraction pattern of the additive manufactured nickel-based high-temperature alloy in Example 3 and the nickel-based high-temperature alloy after hot isostatic pressing treatment.

[0040] Figure 6 is an optical photograph of the additive manufactured nickel-based high-temperature alloy in Comparative Example 1 and the nickel-based high-temperature alloy after conventional hot isostatic pressing treatment. DETAILED DESCRIPTION

[0041] To further clarify the technical means and effects taken by the present application to achieve the intended purpose, the following describes the specific embodiments, structures, features and effects according to the present application in detail with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0042] The embodiment of the present application provides a method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing, which is mainly aimed at additive manufacturing nickel-based high-temperature alloy (Al: 4-5wt%, Co: 7-9wt%, Cr: 9-11wt%, Mo+Ta+W: 14-20wt%, Ti: 0-2wt%, B: 0-0.02wt%, C: 0.01-0.03wt%, Ni: balance) with a volume fraction of γ' phase being greater than 50%, the strength of the alloy is high, cracks and internal pores are easily generated in the additive manufacturing process, and the existing heat treatment cannot solve the problem (the existing heat treatment technology is mainly for high-temperature alloys with a volume fraction of γ' phase being less than 50%). Here, the method proposed in the present application can well solve such problems.

[0043] The concept of the present application is as follows: based on the dissolution of the strengthening phase of the high-temperature alloy into the matrix under high-temperature conditions, the high-temperature strength of the alloy decreases, the residual stress in the additive manufacturing high-temperature alloy is utilized to make the alloy recrystallize, the formation of recrystallization not only reduces the residual stress in the additive manufacturing alloy, but also the grain boundary migrates during the recrystallization process, the large internal micropores can be reduced during the migration process, which is beneficial to the closure of internal micropores and microcracks during hot isostatic pressing. Thus, it is beneficial to improve the mechanical properties of the additive manufacturing alloy, the scheme of the present application can simplify the process, reduce the effect of only relying on the optimization of additive manufacturing process, and solve the problems of high scrap rate and high cost of additive manufacturing high-temperature alloy parts.

[0044] The specific scheme of the present application is as follows:

[0045] The embodiment of the present application provides a method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing, which includes the following steps:

[0046] 1) Put the additive manufacturing high-temperature alloy into the hot isostatic pressing furnace, vacuumize, and wait for the vacuum degree to reach 10 -3 -10 -4 Pa: turn off the vacuum pump, introduce inert gas into the hot isostatic pressing furnace, and heat the additive manufacturing high-temperature alloy to a first preset hot isostatic pressing temperature.

[0047] Specifically, the additive manufacturing high-temperature alloy is put into the hot isostatic pressing furnace, vacuumized, and the vacuum degree is waited to reach 10 -3 -10-4 Pa, the vacuum pump is closed, inert gas is introduced, and the sample is heated, wherein the temperature increasing rate is 10±5℃ / min, and when the temperature difference between the temperature in the hot isostatic pressing furnace and the first preset hot isostatic pressing temperature is 30℃, the temperature increasing rate is adjusted to 1℃ / min.

[0048] Preferably, the inert gas is high-purity argon, and the purity of the argon is ≥99.999%, wherein the oxygen content is ≤5ppm, and the total carbon content is ≤10ppm.

[0049] 2) the additive manufacturing high-temperature alloy is kept at the first preset hot isostatic pressing temperature and the first pressure for a first set time; then the additive manufacturing high-temperature alloy is heated to the second preset hot isostatic pressing temperature, and kept at the second preset hot isostatic pressing temperature and the second pressure for a second set time; after the cooling treatment, the high-temperature alloy after the hot isostatic pressing treatment is obtained.

[0050] Specifically, the additive manufacturing high-temperature alloy is kept at 1100-1150℃ (the first preset hot isostatic pressing temperature) and 10MPa for 0.5h, and then heated to 1200-1280℃ at a temperature increasing rate of 5-10℃ / min, and kept at 1200-1280℃ (the second preset hot isostatic pressing temperature) and 150-180MPa for 2-3h, so as to ensure complete recrystallization in the alloy and release of residual stress in the alloy. Then, the cooling stage after the hot isostatic pressing adopts furnace cooling, the cooling rate is controlled to be within 15℃ / min, and argon is extracted at 5-6L / min per minute, so that the vacuum in the furnace is maintained.

[0051] Here, regarding the above-mentioned scheme of the embodiment of the application, it needs to be explained that:

[0052] (1) The existing heat treatment technology (hot isostatic pressing process, the specific process is as follows: hot isostatic pressing treatment is performed at 1100-1180℃ and 150-180MPa for 2-3h) mainly processes high-temperature alloys with a volume fraction of γ' phase <50%.

[0053] (2) Since the alloy used in the application has high strength, the temperature increasing rate needs to be controlled to be as slow as possible during the heat treatment process, so as to relieve stress concentration in the sample and prevent cracking of the sample. Therefore, gradient heating is set.

[0054] (3) The volume fraction of γ' phase in the alloy is high, and the content of aluminum element in the corresponding alloy is high. The inventors of the application find that if the conventional vacuum degree is used, an oxide film is easily formed at the position of cracks and the like, which is not conducive to the formation of recrystallization. After research, the application first controls the vacuum degree to be 10 -3 -10 -4Pa, and the oxygen content in the argon is more strictly controlled, which is beneficial to the formation of subsequent recrystallization.

[0055] (4) "Under the condition of 1100-1150℃ (first preset hot isostatic pressing temperature) and 10 MPa, heat preservation for 0.5h": the step is mainly to prevent the sample from cracking.

[0056] "Under the condition of 1200-1280℃ (second preset hot isostatic pressing temperature) and 150-180 MPa": a higher pressure stress is used to offset the tensile stress suffered by the alloy and make the alloy recrystallize.

[0057] (5) It should be noted that the ordinary heat treatment in the prior art is prone to cracking when there is no pressure. However, the application adds pressure, which not only heals small holes, but also prevents cracking.

[0058] In addition, the proportion of small angle grain boundaries and large angle grain boundaries in the additive manufacturing high-temperature alloy (as-deposited alloy) is about 1:1. The proportion of small angle grain boundaries and large angle grain boundaries in the high-temperature alloy after hot isostatic pressing is about 1:9, so that the proportion of large angle grain boundaries in the alloy is increased after the method of the application is processed, which is beneficial to improve the strength of the alloy.

[0059] The application will be further described below through specific examples as follows:

[0060] Example 1

[0061] The embodiment provides a method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing. The additive manufacturing nickel-based high-temperature alloy is subjected to hot isostatic pressing treatment to reduce the residual stress in the nickel-based high-temperature alloy. Among them, the volume fraction of γ' phase in the additive manufacturing nickel-based high-temperature alloy is > 50%, and the chemical composition is shown in Table 1.

[0062] Table 1 is the chemical composition (wt%) of the additive manufacturing nickel-based high-temperature alloy of the embodiment.

[0063] Al Co Cr Mo + Ta + W Ti B C Ni 4.3％ 8.0％ 10％ 15.5％ 1.2％ 0.015％ 0.01％ balance

[0064] The specific steps are as follows:

[0065] 1) Put the additive manufacturing nickel-based high-temperature alloy into the hot isostatic pressing furnace, and when the vacuum degree reaches 10 -3 Pa, high-purity argon is introduced, and the sample is heated, and the heating rate is 5℃ / min. When the temperature in the furnace and the first preset hot isostatic pressing temperature difference is 30℃, the heating rate is adjusted to 1℃ / min. Among them, the purity of argon is ≥ 99.999%, and the oxygen content is 5ppm, and the total carbon content is 10ppm.

[0066] 2) the additively manufactured superalloy sample is held at 1100℃ (first pre-set hot isostatic pressing temperature) and 10MPa for 0.5h, then heated to 1200℃ at a heating rate of 5℃ / min, and held at 1200℃ and 150MPa for 2.5h to ensure complete crystallization in the alloy and to release the residual stress in the sample. The cooling stage after hot isostatic pressing is furnace cooling, the cooling rate is controlled within 15℃ / min, and the argon is extracted at 5L / min per minute to keep the vacuum in the furnace. After the cooling process, the hot isostatic pressed nickel-based superalloy is obtained.

[0067] Herein, Figure 2 is the optical photograph of the additively manufactured nickel-based superalloy and the hot isostatic pressed nickel-based superalloy in Example 1. From Figure 2 It can be seen that, compared with the additively manufactured nickel-based superalloy (before hot isostatic pressing), the cracks of the nickel-based superalloy treated by the method of Example 1 (hot isostatic pressed nickel-based superalloy) are greatly reduced and decreased.

[0068] Figure 3 is the electron backscatter diffraction pattern of the additively manufactured nickel-based superalloy and the hot isostatic pressed nickel-based superalloy in Example 1. From Figure 3 It can be seen that: the proportion of low-angle grain boundaries and high-angle grain boundaries in the additively manufactured nickel-based superalloy (before hot isostatic pressing) is about 1:1. While the proportion of low-angle grain boundaries and high-angle grain boundaries in the hot isostatic pressed superalloy is about 1:9, so that the proportion of high-angle grain boundaries in the alloy is increased after the method of Example 1, which is beneficial to improve the strength of the alloy.

[0069] In addition, the scheme of Example 1 makes the alloy have a 980℃ / 260MPa condition durability of 30h, and the residual stress is reduced to 67.8MPa

[0070] Example 2

[0071] This embodiment provides a method for reducing the residual stress of an additively manufactured superalloy based on hot isostatic pressing. The additively manufactured nickel-based superalloy is subjected to hot isostatic pressing treatment to reduce the residual stress in the nickel-based superalloy. Among them, the volume fraction of γ' phase in the additively manufactured nickel-based superalloy is >50%, and the chemical composition is shown in Table 2.

[0072] Table 2 is the chemical composition (wt%) of the additively manufactured nickel-based superalloy of this embodiment

[0073] Al Co Cr Mo + Ta + W Ti B C Ni 4.3％ 8.0％ 10％ 18％ 0％ 0.015％ 0.01％ balance

[0074] The specific steps are as follows:

[0075] 1) Put the additive manufacturing nickel-based superalloy into the hot isostatic pressing furnace, and when the vacuum degree reaches 10 -4 Pa, high-purity argon is introduced, and the sample is heated at a rate of 15℃ / min. When the temperature in the furnace is 30℃ higher than the first preset hot isostatic pressing temperature, the heating rate is adjusted to 1℃ / min. Among them, the purity of argon is ≥99.999%, and the oxygen content is 4ppm, and the total carbon content is 8ppm.

[0076] 2) The additive manufacturing superalloy sample is heated at 1150℃ (the first preset hot isostatic pressing temperature) and 10MPa for 0.5h, and then heated at a rate of 10℃ / min to 1200℃, and heated at 1200℃ and 150MPa for 3h to ensure complete recrystallization in the alloy and release the residual stress in the sample. The cooling stage after hot isostatic pressing adopts furnace cooling, and the cooling rate is controlled within 15℃ / min, and the argon is extracted at 6L / min per minute to keep the vacuum in the furnace. After cooling treatment, the nickel-based superalloy after hot isostatic pressing treatment is obtained.

[0077] Here, Figure 4 is the electron backscatter diffraction pattern of the additive manufacturing nickel-based superalloy and the nickel-based superalloy after hot isostatic pressing in Example 2. From Figure 4 It can be seen that: the proportion of low-angle grain boundary and high-angle grain boundary in the additive manufacturing nickel-based superalloy (before hot isostatic pressing) is about 1:1. And the proportion of low-angle grain boundary and high-angle grain boundary in the superalloy after hot isostatic pressing is about 1:9, so that the proportion of high-angle grain boundary in the alloy is increased after the method of Example 2 is processed, which is beneficial to improve the strength of the alloy.

[0078] The scheme of Example 2 makes the alloy have a 32h durability at 980℃ / 260MPa, and the residual stress is reduced to 67.2MPa.

[0079] Example 3

[0080] This embodiment provides a method for reducing the residual stress of additive manufacturing superalloy based on hot isostatic pressing. The additive manufacturing nickel-based superalloy is subjected to hot isostatic pressing treatment to reduce the residual stress in the nickel-based superalloy. Among them, the volume fraction of γ' phase in the additive manufacturing nickel-based superalloy is >50%, and the chemical composition is shown in Table 3.

[0081] Table 3 is the chemical composition (wt%) of the additive manufacturing nickel-based superalloy of this embodiment

[0082] Al Co Cr Mo + Ta + W Ti B C Ni 4.3％ 8.0％ 10％ 18％ 0％ 0.015％ 0.01％ balance

[0083] The specific steps are as follows:

[0084] 1) Put the additive manufacturing nickel-based superalloy into a hot isostatic pressing furnace, and when the vacuum degree reaches 10 -3 Pa, high-purity argon is introduced, and the sample is heated at a rate of 5℃ / min. When the temperature in the furnace is 30℃ higher than the first preset hot isostatic pressing temperature, the heating rate is adjusted to 1℃ / min. The purity of argon is ≥99.999%, and the oxygen content is 5ppm, and the total carbon content is 10ppm.

[0085] 2) The additive manufacturing superalloy sample is heated at 1150℃ (the first preset hot isostatic pressing temperature) and 10MPa for 0.5h, and then heated at a rate of 10℃ / min to 1280℃, and heated at 1280℃ and 150MPa for 3h to ensure that the alloy is completely crystallized and the residual stress in the sample is released. The cooling stage after hot isostatic pressing adopts furnace cooling, and the cooling rate is controlled within 15℃ / min, and the argon is extracted at a rate of 5L / min per minute, so that the vacuum in the furnace is maintained. After cooling treatment, the nickel-based superalloy after hot isostatic pressing treatment is obtained.

[0086] Figure 5 are the electron backscatter patterns of the additive manufacturing nickel-based superalloy in Example 3 and the nickel-based superalloy after hot isostatic pressing treatment. From Figure 5 It can be seen that the proportion of low-angle grain boundaries and high-angle grain boundaries in the additive manufacturing nickel-based superalloy (before hot isostatic pressing) is about 1:1. The proportion of low-angle grain boundaries and high-angle grain boundaries in the superalloy after hot isostatic pressing treatment is about 1:9, so that the proportion of high-angle grain boundaries in the alloy is increased after the method of Example 3 is treated, which is beneficial to improve the strength of the alloy.

[0087] The scheme of Example 3 makes the alloy have a creep rupture property of 31h at 980℃ / 260MPa, and the residual stress is reduced to 16.9MPa.

[0088] In addition, the residual stress of the additive manufacturing nickel-based superalloy (i.e. as-deposited), the nickel-based superalloy after the treatment of Examples 1-3 is tested, and the residual stress comparison is shown in Figure 1 It can be seen from Figure 1 that the residual stress in the alloy is significantly reduced after hot isostatic pressing treatment.

[0089] Comparative Example 1

[0090] In this comparative example, the additive manufacturing nickel-based superalloy is subjected to conventional hot isostatic pressing treatment. Specifically, the alloy sample is subjected to hot isostatic pressing treatment at 1180℃ and 150MPa for 3h. The composition of the additive manufacturing nickel-based superalloy is shown in Table 1 in Example 1.

[0091] wherein,Figure 6 are optical photographs of the additive manufactured nickel-based superalloy in Comparative Example 1 and the nickel-based superalloy after conventional hot isostatic pressing treatment. From the photographs, it can be seen that the cracks on the alloy after treatment in Comparative Example 1 have a tendency to be smaller, but are not completely closed, and the effect is not as ideal as the effect of the hot isostatic pressing method of the above-mentioned embodiments of the present application. Figure 6

[0092] In addition, it is measured that the alloy treated by conventional hot isostatic pressing (the process of Comparative Example 1) has a durability of only 15 h at 980℃ / 260MPa, and the residual stress is reduced to 107.3MPa.

[0093] In summary, the method for reducing the residual stress of an additive manufactured superalloy based on hot isostatic pressing according to the present application can significantly reduce the residual stress of the additive manufactured superalloy by hot isostatic pressing of the alloy at a high temperature of 1100-1280℃ and a stress of 150-180MPa (and, the vacuum degree, heating time, heating rate, and step-by-step hot isostatic pressing treatment are designed and controlled accordingly), and by using the recrystallization process occurring in the alloy. The method has the characteristics of low cost and good effect, and can also effectively reduce the internal micropores of the alloy during the additive manufacturing process, so that the alloy has high high-temperature mechanical properties and toughness, good microstructure stability, and is particularly suitable for the preparation of high-temperature components in the fields of aerospace, aviation, ships, petrochemical industry, etc.

[0094] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.​

Claims

1. A method for reducing residual stresses in additively manufactured high temperature alloys based on hot isostatic pressing, characterized in that, wherein, the additive manufacturing high-temperature alloy is a nickel-based high-temperature alloy, and the chemical composition of the nickel-based high-temperature alloy comprises, in terms of weight percentage: Al: 4-5wt%, Co: 7-9wt%, Cr: 9-11wt%, Mo+Ta+W: 14-20wt%; Ti: 0-2wt%; B: 0-0.02wt%; C: 0.01-0.03wt%; Ni: balance; which comprises the following steps: 1) Put the additive manufacturing high-temperature alloy into a hot isostatic pressing furnace, vacuumize, when the vacuum degree is 10 -3 -10 -4 Pa: turn off the vacuum pump, introduce inert gas into the hot isostatic pressing furnace, and heat the additive manufacturing high-temperature alloy to a first preset hot isostatic pressing temperature; wherein in the step 1): heating the additive manufacturing high-temperature alloy, first heating the additive manufacturing high-temperature alloy to a set temperature at a heating rate of 5-15℃ / min, and then heating to the first preset hot isostatic pressing temperature at a heating rate of 1-3℃ / min; wherein the set temperature is 30±3℃ lower than the first preset hot isostatic pressing temperature; 2) allowing the additive manufacturing high-temperature alloy to be kept at a first preset hot isostatic pressing temperature and a first pressure for a first set time; then allowing the additive manufacturing high-temperature alloy to be heated to a second preset hot isostatic pressing temperature, and kept at the second preset hot isostatic pressing temperature and a second pressure for a second set time, so that recrystallization of the additive manufacturing high-temperature alloy occurs; after the cooling treatment, a high-temperature alloy after hot isostatic pressing treatment is obtained; wherein the first preset hot isostatic pressing temperature is 1100-1150℃, the first pressure is 10±3MPa, and the first set time is 0.5±0.1h; the second preset hot isostatic pressing temperature is 1200-1280℃, the second pressure is 150-180MPa, and the second set time is 2-3h.

2. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, the additive manufacturing high-temperature alloy is a nickel-based high-temperature alloy with a volume fraction of γ' phase > 50%.

3. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, in the step 1): the inert gas has a purity ≥ 99.999%, an oxygen content ≤ 5ppm, and a total carbon content ≤ 10ppm; and / or the inert gas is argon.

4. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, in the step 2): the additive manufacturing high-temperature alloy is heated from the first preset hot isostatic pressing temperature to the second preset hot isostatic pressing temperature at a heating rate of 5-10℃ / min.

5. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, in the step 2): when the cooling treatment is performed, the cooling rate is controlled to be within 15℃ / min.

6. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 5, wherein, in the step 2): when the cooling treatment is performed, the inert gas in the hot isostatic pressing furnace is extracted at a rate of 5-6L / min.

7. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, the proportion of small-angle grain boundaries and large-angle grain boundaries in the additive manufacturing high-temperature alloy is (1±0.5):(1:±0.5).

8. The method of reducing residual stresses in additively manufactured high temperature alloys by hot isostatic pressing of claim 1, wherein, the proportion of small-angle grain boundaries and large-angle grain boundaries in the high-temperature alloy after hot isostatic pressing treatment is (1±0.5):(9±0.5).

9. A hot isostatically pressed high temperature alloy, characterized by the high-temperature alloy after hot isostatic pressing treatment is a nickel-based high-temperature alloy; wherein the proportion of small-angle grain boundaries and large-angle grain boundaries in the high-temperature alloy after hot isostatic pressing treatment is (1±0.5):(9±0.5). wherein the high-temperature alloy after hot isostatic pressing treatment is obtained by subjecting the additive manufacturing high-temperature alloy to the method for reducing residual stress of additive manufacturing high-temperature alloy based on hot isostatic pressing according to any one of claims 1-8.

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