CN117702026A - Laser selective melting alloy and heat treatment process for components thereof - Google Patents
Laser selective melting alloy and heat treatment process for components thereof Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/60—Treatment of workpieces or articles after build-up
- B22F10/64—Treatment of workpieces or articles after build-up by thermal means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/20—Post-treatment, e.g. curing, coating or polishing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y80/00—Products made by additive manufacturing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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Abstract
The invention relates to a heat treatment process for a laser selective melting alloy and a component thereof, belongs to the technical field of additive manufacturing heat treatment, and solves the problems of low component qualification rate caused by high deformation and cracking risks of the component by the existing heat treatment process. The heat treatment process comprises the following steps: step 1: carrying out stress relief treatment on an alloy sample and/or a component thereof prepared by adopting a laser selective melting technology; step 2: and (3) aging the destressing alloy and/or the component thereof. The heat treatment process can improve the qualification rate of the components by 30-40%.
Description
Technical Field
The invention relates to the technical field of additive manufacturing heat treatment, in particular to a heat treatment process for selectively melting GH4099 alloy and a member thereof by laser.
Background
GH4099 alloy is an aging-strengthened nickel-base superalloy with a main strengthening phase of gamma '-phase (gamma' -Ni) 3 (Al, ti)). Under the action of precipitation strengthening of a high-density gamma' phase and solid solution strengthening coupling of elements such as W, mo, co and the like, the GH4099 superalloy can be stably used at 800-900 ℃, and the highest use temperature is even more than 1000 ℃; meanwhile, the GH4099 alloy also has higher heat intensity and good welding and cold and hot processing forming performances. Therefore, the GH4099 alloy is a key structural material of parts such as a combustion chamber, a cabin section and the like of a high-speed aircraft engine, and is widely applied to the field of military industry such as aviation, aerospace and the like.
At present, the main processing modes of GH4099 alloy are forging, machining and the like, but the traditional mode is difficult to realize integral forming of a complex structure, and the application and development of GH4099 high-temperature alloy are greatly limited. The laser selective melting technique (selective laser melting, SLM) is an additive manufacturing technique (Additive Manufacturing, AM) that utilizes a high energy laser beam to selectively heat metal powder to completely melt and rapidly solidify it. Compared with other AM technologies (directional energy deposition, laser three-dimensional forming and the like), the SLM technology has obvious advantages in the aspects of forming precision, forming complexity, component quality and the like, and becomes the most ideal manufacturing technology for large-size, ultrathin and complex GH4099 superalloy components. However, in the actual production process, the GH4099 high-temperature component prepared by the SLM often has the problems of deformation or cracking after heat treatment, and the root cause is that the existing heat treatment system is not suitable for the GH4099 high-temperature component manufactured by the SLM.
At present, few reports are about the heat treatment system of the SLM-GH4099 alloy and the components, and the prior patent: patent application number CN 202110294836.7, named as a heat treatment process for forming parts by selective laser melting of GH4099 alloy; 2) Patent application number CN 202111310804.8, entitled heat treatment method for forming GH4099 alloy components by selective laser melting. The SLM-GH4099 alloy heat treatment process related to the two patent documents is formed by optimizing the existing GH4099 casting or forging heat treatment process, and the prior art does not have a nest socket which is free from the traditional heat treatment process.
The heat treatment scheme of the conventional GH4099 alloy must first be solution treated, i.e.: firstly, the GH4099 alloy is slowly heated to 1100 ℃, kept for 1-2 hours, and then cooled to room temperature by air or water. Solution treatment will present three problems: 1) The risk of deformation and cracking increases; 2) Performance improvement is insufficient; 3) The efficiency is reduced. The solution treatment comprises the processes of heating, heat preservation, cooling and the like, so that the time cost is obviously increased, and the production efficiency is lower.
Therefore, providing a heat treatment process suitable for laser selective melting of GH4099 superalloy and components thereof is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a heat treatment process for a laser selective zone melting alloy and a component thereof, which is used for solving at least one of the following technical problems: (1) The heat treatment process of solid solution and aging causes the deformation and cracking risk of the component to be large, so that the qualification rate of the component is low; (2) The low-temperature and high-temperature tensile properties of the SLM-GH4099 alloy are insufficient; (3) The existing SLM-GH4099 superalloy component has complex heat treatment process flow and low production efficiency.
In one aspect, the invention provides a heat treatment process for selectively melting an alloy by laser, comprising the following steps:
step 1: performing stress relief treatment on the alloy prepared by adopting a laser selective melting technology;
step 2: and (5) aging the alloy subjected to the stress relief treatment.
Further, the step 2 includes the steps of:
step 21: placing the alloy treated in the step 1 in a vacuum furnace for vacuumizing;
step 22: heating the vacuum furnace, and after the furnace temperature reaches the target temperature, preserving heat for the first time; after the first heat preservation is finished, cooling the vacuum furnace to a certain lower temperature, and carrying out the second heat preservation;
step 23: and (5) cooling.
Further, in the step 21, the vacuum degree is 5 to 10×10 -4 Torr。
Further, the step 23 includes: cooling to room temperature in a vacuum furnace along with the furnace.
Further, the alloy is a GH4099 alloy.
Further, the step 1 includes the following steps:
step 11: placing the alloy and/or components thereof in a vacuum furnace for vacuumizing;
step 12: heating and preserving heat of the vacuum furnace;
step 13: and (5) cooling.
Further, in the step 12, the temperature of the vacuum furnace is 500-550 ℃, and the heat preservation time is 1-2 hours.
Further, in the step 12, the incubation time is 2 hours.
Further, the laser selective melting alloy includes an alloy sample and an alloy member.
On the other hand, the invention also provides a laser selective melting alloy, which is obtained by adopting the heat treatment process, wherein the room temperature yield strength of the laser selective melting alloy is more than or equal to 1020MPa, the tensile strength is more than or equal to 1180MPa, the elongation is more than or equal to 20%, the yield strength at 950 ℃ is more than or equal to 220MPa, the tensile strength is more than or equal to 290MPa, and the elongation is more than or equal to 25%.
Further, the tensile fracture of the alloy is in a cross-crystal fracture morphology.
Further, the fracture surface of the alloy contains a large number of fine dimples.
Further, the internal strengthening phase (gamma prime phase) of the alloy is smaller in size and higher in density.
Further, the grain boundaries of the alloy are free of large-size, continuous carbides.
Further, in the step 22, the first heat preservation temperature is higher than the second heat preservation temperature, the first heat preservation temperature is 800-850 ℃, the first heat preservation time is 1-2 hours, and the first heat preservation temperature is used for promoting the nucleation of gamma' -phase. The temperature of the second heat preservation is 700-750 ℃ and is used for inhibiting the growth of gamma 'phase so as to obtain small and dense gamma' phase, and the second heat preservation time is 3-4 hours.
Compared with the prior art, the invention can at least realize one of the following technical effects:
1) The traditional heat treatment process for GH4099 alloy in the prior art comprises the following steps: solution treatment and aging treatment. Even if SLM technology is combined, solution treatment + aging treatment is still employed. The heat treatment process of solid solution and aging leads the deformation and cracking risk of the component to be high, so that the qualification rate of the component is low. The invention utilizes the special process characteristics of SLM technology, namely small molten pool and high cooling speed, the molten pool is condensed from liquid state to solid state in extremely short time, and most elements exist in the deposited GH4099 alloy matrix in the form of solid solution because solute elements do not have enough time to diffuse.
Based on the above findings, the present invention innovatively proposes omitting the solution treatment and directly performing the aging treatment. The alloy and the component surface and the core part are unevenly cooled due to direct air cooling (or water cooling) from 1100 ℃ to room temperature in the solid solution process, so that the alloy or the component is deformed and cracked. The heat treatment process of the invention does not carry out solid solution treatment, so the deformation and cracking risks of the component can be greatly reduced, and the qualification rate of the component can be improved (the qualification rate of the component is improved by 30% -40%). In addition, the solution treatment is not performed, so that the heat treatment process flow is simplified, and the production efficiency is improved.
(2) In terms of mechanical properties, the GH4099 alloy subjected to direct aging heat treatment has room temperature and high temperature mechanical properties which are obviously superior to those of samples (shown in table 1) of the existing heat treatment system. Wherein the room temperature yield strength is improved by more than 30%. As shown in fig. 6 and 7, the direct aging samples were cross-crystal fractures; the existing solid solution aging test sample is broken along crystals, which may be related to solid solution treatment, and after the solid solution treatment, the crystal boundary is enriched with a large amount of solute elements, so that the crystal boundary strength is weakened, and the broken along crystals occurs. This also represents an advantage of direct ageing.
(3) The aging treatment in the prior art is one-step aging treatment, the aging treatment in the invention is two-step aging treatment, the first-step aging treatment is used for promoting the nucleation of gamma ' phase, and the second-step aging treatment is used for inhibiting the growth of gamma ' phase so as to obtain small and dense gamma ' phase, thereby improving the mechanical property of the alloy. The mechanical properties of the alloy are further improved by setting the temperature of the first ageing treatment to be higher than the temperature of the second ageing treatment.
(4) The alloy obtained by the heat treatment process has the room temperature yield strength of more than or equal to 1020MPa, the tensile strength of more than or equal to 1180MPa, the elongation of more than or equal to 20 percent, the yield strength at 950 ℃ of more than or equal to 220MPa, the tensile strength of more than or equal to 290MPa and the elongation of more than or equal to 25 percent.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like numbers referring to like parts throughout the drawings.
FIG. 1 is a thermal processing technology roadmap of the SLM-GH4099 alloy structure of the invention;
FIG. 2 (a) shows the microstructure morphology of a deposited GH4099 alloy at a low magnification;
FIG. 2 (b) shows the internal substructures of grains and the morphology of nano-carbides at high multiples of the as-deposited GH4099 alloy;
FIG. 3 is a diagram of the inverse pole of the as-deposited GH4099 alloy (Inverse Pole Figure, IPF);
FIG. 4 is an SEM image of a tensile fracture of GH4099 alloy of example 1; wherein, (a) is a macroscopic fracture morphology parallel to the direction of the additive and at a low multiple, (b) is a macroscopic fracture morphology perpendicular to the direction of the additive and at a low multiple, (c) is a microscopic fracture morphology parallel to the direction of the additive and at a high multiple, and (d) is a microscopic fracture morphology perpendicular to the direction of the additive and at a high multiple;
FIG. 5 is a SEM image of a GH4099 alloy stretch port of comparative example 1; wherein, (a) is a macroscopic fracture morphology parallel to the direction of the additive and at a low multiple, (b) is a macroscopic fracture morphology perpendicular to the direction of the additive and at a low multiple, (c) is a microscopic fracture morphology parallel to the direction of the additive and at a high multiple, and (d) is a microscopic fracture morphology perpendicular to the direction of the additive and at a high multiple;
FIG. 6 is grain boundary morphology and gamma prime phase analysis of GH4099 alloy in example 1;
FIG. 7 is grain boundary morphology and gamma prime phase analysis of GH4099 alloy in comparative example 1;
FIG. 8 is a drawing of a direct aging GH4099 alloy at 950 ℃.
Detailed Description
A heat treatment process for laser selective melting of GH4099 superalloy components is described in further detail below in connection with specific examples, which are for comparison and explanation purposes only, and the invention is not limited to these examples.
As shown in fig. 1, the present invention provides a heat treatment process for a laser selective melting alloy and a component thereof, and in particular, a heat treatment process for a GH4099 (SLM-GH 4099) alloy and a component thereof prepared by a laser selective melting technology. The GH4099 nickel-based superalloy comprises the following chemical components in percentage by mass: less than or equal to 0.08 percent of C, 17.00 to 20.0 percent of Cr, 5.00 to 7.00 percent of W, 3.50 to 4.50 percent of Mo, 1.70 to 2.40 percent of Al, 5.00 to 8.00 percent of Co, 1.00 to 1.50 percent of Ti, less than or equal to 2.00 percent of Fe, less than or equal to 0.005 percent of B, less than or equal to 0.010 percent of Mg, less than or equal to 0.020 percent of Ce, less than or equal to 0.40 percent of Mn, less than or equal to 0.50 percent of Si, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and the balance of Ni.
The heat treatment process comprises the following steps:
step 1: carrying out stress relief treatment on the alloy and/or the component thereof prepared by adopting a laser selective melting technology;
step 2: and aging the alloy and/or the component thereof after the stress relief treatment to obtain the SLM-GH4099 alloy and/or the component thereof.
The traditional heat treatment process for GH4099 alloy in the prior art comprises the following steps: solution treatment and aging treatment. Even if SLM technology is combined, solution treatment + aging treatment is still employed. In the solid solution treatment process, the cooling speed is high in the air cooling or water cooling process, so that the GH4099 alloy or the surface and the core of the component are uneven in cooling speed, larger internal stress is easy to generate, the risk of deformation and cracking of the component is increased, and the qualification rate of the component is low.
In addition, the purpose of the solution treatment is to uniformly distribute solute elements originally existing in a precipitated phase form in the GH4099 alloy in the matrix, so that the solute elements are precipitated again during aging treatment, and further, better mechanical properties are obtained. In order to allow the solute elements to re-enter the matrix as much as possible, it is necessary to ensure a sufficiently high temperature and a sufficiently long time for the solutionizing process. The high temperature and the long time can promote the uniform distribution of elements in the matrix and simultaneously lead to the occurrence of physical processes such as recrystallization, grain growth, dislocation annihilation, segregation of solute elements in grain boundaries and the like of the GH4099 alloy. Therefore, defects such as dislocation and vacancy in the structure of the GH4099 alloy after solution treatment are remarkably reduced in spite of casting, forging or additive. These high density defects promote nucleation and growth of the gamma' -phase, thereby improving the performance of the GH4099 alloy. For example, dislocation can be used as nucleation point of gamma 'phase, so as to reduce nucleation barrier and promote dispersion precipitation of gamma' phase; the vacancies are used as solute element diffusion media, and the high-density vacancies can promote the diffusion of solute elements, thereby being beneficial to the precipitation and growth of gamma' phase and shortening the heat treatment time. From this point of view, the solution treatment is also detrimental to the performance optimization of SLM-GH4099 alloys.
The invention utilizes the special process characteristics of SLM technology, namely small molten pool and high cooling speed, the molten pool is condensed from liquid state to solid state in extremely short time, and most elements exist in the deposited GH4099 alloy matrix in the form of solid solution because solute elements do not have enough time to diffuse.
As shown in FIG. 2 (a) and FIG. 2 (b), the GH4099 alloy in the deposited state has a uniform structure, fine grains and a large amount of grainsDislocation cells; the dislocation cell walls have a small amount of white nano-carbides. In addition, as can be seen from fig. 3, the morphology of the as-deposited GH4099 alloy grains is in an irregular shape. It should be noted that no other second phase is present inside the as-deposited GH4099 alloy except for a small amount of nano-scale carbides, which further demonstrates that the as-deposited GH4099 alloy is in a supersaturated state and that most solute elements are present in the matrix in solid solution. The main reason for this phenomenon is: SLM is a strongly unbalanced process with small melt pool and fast cooling (up to 10 6 -10 8 K/s) can be solidified in a very short time, so that solute elements in a molten pool are frozen in a matrix without diffusion precipitation; the structural characteristic is that the SLM-GH4099 alloy is most obviously different from the traditional casting and forging GH4099 alloy, and the method also provides possibility for developing a new heat treatment process.
Meanwhile, the SLM-GH4099 superalloy contains high-density dislocation cells (shown in figure 2), the nucleation barrier of the gamma 'phase can be obviously reduced by the high-density dislocation, and the precipitation and growth of the gamma' phase are promoted; meanwhile, the cell tissue interface contains a large number of solute element clusters (which are observed in literature and commonly known in academia), so that the element diffusion distance can be obviously shortened, and the solute clusters can also serve as nucleation points to promote the formation of a high-density gamma' phase.
The heat treatment process of direct aging provided by the invention fully utilizes high-density dislocation and cellular tissue in the deposited GH4099 alloy to generate more diffuse gamma' phase; the high density gamma' phase can hinder the movement of dislocations, significantly improving the performance of SLM-GH4099 alloys and components.
Specifically, step 1 includes the following steps:
step 11: placing the alloy and/or components thereof in a vacuum furnace for vacuumizing;
step 12: heating and preserving heat of the vacuum furnace;
step 13: and (5) cooling.
In one embodiment, in step 11, the vacuum degree of the vacuum furnace is 5 to 10×10 -4 Torr may be, for example, 5×10 -4 Torr、6×10 -4 Torr、7×10 -4 Torr、8×10 -4 Torr、9×10 -4 Torr、10×10 -4 Torr。
In one embodiment, in step 12, the vacuum furnace is heated to 500-550 ℃, e.g., 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃. The heating rate is 5-10deg.C/min, such as 5deg.C/min, 6deg.C/min, 7deg.C/min, 8deg.C/min, 9deg.C/min, 10deg.C/min. The incubation time is 1-2 hours, for example, 1 hour, 1.5 hours, 2 hours. The furnace temperature fluctuation is controlled within the range of +/-5 ℃.
In one embodiment, in step 13, cooling includes furnace cooling the alloy and/or components thereof to room temperature.
Specifically, the step 2 includes two aging treatments, specifically including the following steps:
step 21: placing the alloy and/or the components thereof treated in the step 1 into a vacuum furnace for vacuumizing;
step 22: heating the vacuum furnace to 800-850 ℃ for the first time, and preserving heat for 1-2h; then cooling to 700-750 ℃, carrying out secondary heat preservation, and preserving heat for 3-4 hours;
step 23: and (5) cooling.
In one embodiment, in step 21, the vacuum degree of the vacuum furnace is 5 to 10×10 -4 Torr may be, for example, 5×10 -4 Torr、6×10 -4 Torr、7×10 -4 Torr、8×10 -4 Torr、9×10 -4 Torr、10×10 -4 Torr。
In one embodiment, in step 22, the first soak temperature is higher than the second soak temperature.
Specifically, the temperature of the first incubation is 800-850 ℃, e.g., 800 ℃, 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃. The heating rate is 5-10deg.C/min, such as 5deg.C/min, 6deg.C/min, 7deg.C/min, 8deg.C/min, 9deg.C/min, 10deg.C/min. The incubation time is 1-2 hours, for example, 1 hour, 1.5 hours, 2 hours. The furnace temperature fluctuation is controlled within the range of +/-5 ℃.
The second incubation is at a temperature of 700-750deg.C, e.g., 700 deg.C, 710 deg.C, 720 deg.C, 730 deg.C, 740 deg.C, 750 deg.C. The cooling rate is 15-20deg.C/min, for example, 15 deg.C/min, 16 deg.C/min, 17 deg.C/min, 18 deg.C/min, 19 deg.C/min, 20 deg.C/min. The incubation time is 3-4 hours, for example, 3 hours, 3.5 hours, 4 hours. The furnace temperature fluctuation is controlled within the range of +/-5 ℃.
In one embodiment, in step 22 and step 23, cooling includes cooling the alloy and/or components thereof with the furnace to room temperature.
The SLM-GH4099 alloy and/or components thereof prepared and drawn samples were prepared using wire cutting for a high temperature (950 ℃) tensile test.
Example 1:
(1) Placing GH4099 laser selective zone melting alloy sample and additive substrate in vacuum furnace, and then pumping the vacuum furnace until the vacuum degree in the furnace reaches 5×10 -4 Torr. Then the vacuum furnace is heated to 500 ℃ by adopting the heating rate of 5 ℃/min, and the temperature is kept for 2 hours, so as to carry out stress relief treatment. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(2) Taking out the GH4099 alloy sample subjected to stress relief treatment from a vacuum furnace, removing the additive substrate by linear cutting, placing the GH4099 alloy sample in a vacuum heat treatment furnace, and then pumping the vacuum furnace to enable the vacuum degree to reach 5 multiplied by 10 -4 Torr. Then the temperature of the vacuum furnace is raised to 800 ℃ by adopting the temperature rising rate of 5 ℃/min, and the vacuum furnace is kept for 2 hours. And after the heat preservation is finished, cooling to 700 ℃, and preserving the heat for 4 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(3) And after the GH4099 alloy sample is cooled, performing linear cutting to prepare a tensile sample, and performing a low-temperature and high-temperature tensile test. The test results are shown in Table 1.
Example 2:
(1) Placing GH4099 laser selective melting component and additive substrate in vacuum furnace, and then pumping the vacuum furnace until the vacuum degree in the furnace reaches 10×10 -4 Torr. Then the vacuum furnace is heated to 550 ℃ by adopting the heating rate of 5 ℃/min, and the temperature is kept for 1.5h, so as to carry out stress relief treatment. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(2) Removing the stress-removed GH4099 component from the vacuum furnace, removing the additive substrate by wire cutting, and placing the GH4099 component in a vacuum heat treatment furnaceThen the vacuum furnace is pumped to make the vacuum degree reach 10 multiplied by 10 -4 Torr. Then the temperature of the vacuum furnace is raised to 850 ℃ by adopting the temperature rising rate of 5 ℃/min, and the vacuum furnace is kept for 1h. And after the heat preservation is finished, cooling to 750 ℃, and preserving the heat for 3 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(3) After the GH4099 component is cooled, wire cutting is carried out to prepare a tensile sample, and a low-temperature and high-temperature tensile test is carried out. The test results are shown in Table 1.
Example 3:
(1) Placing GH4099 laser selective zone melting alloy sample and additive substrate in vacuum furnace, and then pumping the vacuum furnace until the vacuum degree in the furnace reaches 8×10 -4 Torr. Then heating the vacuum furnace to 520 ℃ by adopting a heating rate of 8 ℃/min, and preserving heat for 2 hours to perform stress relief treatment. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(2) Taking out the GH4099 alloy sample subjected to stress relief treatment from a vacuum furnace, removing the additive substrate by linear cutting, placing the GH4099 alloy sample in a vacuum heat treatment furnace, and then pumping the vacuum furnace to ensure that the vacuum degree reaches 8 multiplied by 10 -4 Torr. Then the temperature of the vacuum furnace is raised to 820 ℃ by adopting the temperature rising rate of 8 ℃/min, and the temperature is kept for 1.5h. And after the heat preservation is finished, cooling to 720 ℃, and preserving the heat for 3 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(3) And after the GH4099 alloy sample is cooled, performing linear cutting to prepare a tensile sample, and performing a low-temperature and high-temperature tensile test. The test results are shown in Table 1.
Example 4:
(1) Placing GH4099 laser selective melting component and additive substrate in vacuum furnace, and then pumping the vacuum furnace until the vacuum degree in the furnace reaches 6×10 -4 Torr. Then heating the vacuum furnace to 530 ℃ by adopting a heating rate of 6 ℃/min, and preserving heat for 1h to perform stress relief treatment. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(2) Taking out the GH4099 component subjected to stress relief treatment from the vacuum furnace, removing the additive substrate by linear cutting, placing the GH4099 component in the vacuum heat treatment furnace, and pumping the vacuum furnace to make the vacuum degree reach 7×10 -4 Torr。Then the vacuum furnace is heated to 830 ℃ by adopting the heating rate of 6 ℃/min, and the temperature is kept for 1.5h. And after the heat preservation is finished, cooling to 730 ℃, and preserving the heat for 3 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(3) After the GH4099 component is cooled, wire cutting is carried out to prepare a tensile sample, and a low-temperature and high-temperature tensile test is carried out. The test results are shown in Table 1.
Comparative example 1:
(1) Placing an SLM-GH4099 alloy sample and an additive substrate in a vacuum heat treatment furnace, and then pumping the vacuum furnace to enable the vacuum degree to reach 5 multiplied by 10 -4 Torr. Firstly, heating the vacuum furnace to 500 ℃ by adopting a heating rate of 5 ℃/min, and preserving heat for 2 hours to perform stress relief treatment. And after the heat preservation is finished, cooling to room temperature along with the furnace.
(2) Then heating the vacuum furnace to 1100 ℃ by adopting a heating rate of 10 ℃/min, and preserving heat for 1h to carry out solution treatment. And after the heat preservation is finished, blowing low-temperature argon gas to cool to room temperature, wherein the cooling time is about 50min.
(3) Then the temperature of the vacuum furnace is raised to 750 ℃ by adopting the heating rate of 10 ℃/min, and the vacuum furnace is kept for 8 hours. And after the heat preservation is finished, cooling the GH4099 alloy sample to room temperature along with the furnace.
(4) And after the GH4099 alloy sample is cooled, performing linear cutting to prepare a tensile sample, and performing a low-temperature and high-temperature tensile test. The test results are shown in Table 1.
Comparative example 2:
comparative example 2 was substantially the same as example 4 except that the aging treatment was one-step aging treatment, specifically, the vacuum furnace was heated to 800 c at a heating rate of 6 c/min and kept for 8 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
Comparative example 3:
comparative example 3 was substantially the same as example 4 except that the temperature of the first aging treatment was lower than that of the second aging treatment, specifically, the vacuum furnace was raised to 730 c at a temperature raising rate of 6 c/min and kept for 1.5 hours. After the heat preservation is finished, the temperature is raised to 830 ℃, and the heat preservation is carried out for 3 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
Comparative example 4:
comparative example 4 is substantially the same as example 4 except that the temperature of the first aging treatment is not in the range of 800 to 850 c and the temperature of the second aging treatment is not in the range of 700 to 750 c. Specifically, the temperature of the vacuum furnace is raised to 900 ℃ by adopting the temperature rising rate of 6 ℃/min, and the temperature is kept for 1.5h. And after the heat preservation is finished, cooling to 800 ℃, and preserving the heat for 3 hours. And after the heat preservation is finished, cooling to room temperature along with the furnace.
TABLE 1 comparison of the temperature and high temperature tensile properties of the samples of examples 1-4 and comparative examples 1-4
As can be seen from the data of comparative example 1 and examples 1 to 4 in Table 1, the mechanical properties of the products obtained by the heat treatment process in which the aging treatment is performed after the solid solution treatment are significantly inferior to those of the products obtained by the heat treatment process in which the aging treatment is directly performed in the present invention.
As can be seen from a comparison of the data of comparative example 2 and the data of example 4, the mechanical properties of the alloy were poor in the direct one-step aging (comparative example 2) compared to the two-step aging (example 4).
As can be seen from a comparison of the data of comparative example 3 and the data of example 4, if the temperature of the first aging treatment is lower than that of the second aging treatment, the mechanical properties of the alloy are poor.
As can be seen from a comparison of the data of comparative example 4 and the data of example 4, if the temperature of the first aging treatment is not in the range of 800 to 850℃and the temperature of the second aging treatment is not in the range of 700 to 750℃the mechanical properties of the alloy are poor.
In addition to tensile testing, the present invention also performed tissue and performance analyses for example 1 and comparative example 1.
Fig. 4 and 5 are tensile fracture analyses of example 1 and comparative example 1, respectively. As shown in FIG. 4, the GH4099 superalloy obtained in example 1 has an obvious through-crystal fracture morphology, and the fracture surface contains a large number of fine ductile pits. While the GH4099 superalloy obtained in comparative example 1 exhibits an along-grain fracture morphology, the ductile fossa size is significantly larger than in example 1.
Fig. 6 and 7 are grain boundary and gamma' phase analyses of example 1 and comparative example 1, respectively. As shown in fig. 6 and 7, example 1 and comparative example 1 obtained GH4099 alloy containing a high-density nano-sized γ' precipitate phase inside. However, as can be seen from comparing fig. 6 and fig. 7, the GH4099 alloy obtained in example 1 has smaller internal strengthening phase (γ' phase) and higher density. While small, dense precipitate phases can impede dislocation movement, but do not pin dislocations, resulting in dislocation pile-up leading to cracking. Therefore, the small and dense gamma prime precipitate produced in example 1 not only improves the mechanical properties of the GH4099 alloy, but also improves the toughness of the material. This is the root cause of the significant increase in yield strength. Meanwhile, the GH4099 alloy obtained in example 1 was relatively clean in grain boundary and no large-sized, continuous carbides (precipitated phases) were present. The bonding strength of the grain boundary is higher from the side, and the grain boundary fracture is not easy to occur, which is consistent with the test observation result of fig. 4. While the GH4099 alloy obtained in comparative example 1 has many large-sized, continuous carbides at grain boundaries, these carbides weaken the grain boundary strength, resulting in easy breakage of the material along the grain boundaries. This phenomenon can well explain why the alloy in fig. 5 (comparative example 1) is broken along the crystal.
FIG. 8 is a drawing curve of GH4099 alloy at 950℃in example 1. As can be seen from FIG. 8, the GH4099 alloy obtained by the invention has excellent mechanical properties at 950 ℃, and completely meets the service requirements of high-temperature parts of aircrafts.
The heat treatment process of the present invention is particularly suitable for treating large thin-walled components such as cabins, end frames, etc. According to the invention, the GH4099 alloy sample and/or the member thereof is subjected to direct ageing treatment, the ageing treatment is set to be two-step ageing treatment, and the temperature of the first-step ageing treatment is controlled to be higher than that of the second-step ageing treatment, so that the qualification rate of large thin-wall members (cabin sections, end frames and the like) is improved by 30% -40%. Compared with one-step aging, the two-step aging not only can better regulate and control the alloy performance, but also can further eliminate the residual stress of the component generated by the processes of material increase, phase change and the like, and improve the quality of the large thin-wall component.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. A heat treatment process for melting alloy by laser selective area, which is characterized by comprising the following steps:
step 1: performing stress relief treatment on the alloy prepared by adopting a laser selective melting technology;
step 2: and (5) aging the alloy subjected to the stress relief treatment.
2. The heat treatment process according to claim 1, wherein the step 2 comprises a two-step aging treatment comprising the steps of:
step 21: placing the alloy treated in the step 1 in a vacuum furnace for vacuumizing;
step 22: heating the vacuum furnace, and carrying out first heat preservation after the furnace temperature reaches the target temperature; after the first heat preservation is finished, cooling the vacuum furnace to a certain lower temperature, and carrying out the second heat preservation;
step 23: and (5) cooling.
3. The heat treatment process according to claim 2, wherein in the step 21, the vacuum degree is 5 to 10 x 10 -4 Torr。
4. The heat treatment process according to claim 2, wherein the step 23 comprises: cooling to room temperature in a vacuum furnace along with the furnace.
5. The heat treatment process according to claim 1, wherein the alloy is a GH4099 alloy.
6. The heat treatment process according to claim 1, wherein the step 1 comprises the steps of:
step 11: placing the alloy and/or components thereof in a vacuum furnace for vacuumizing;
step 12: heating and preserving heat of the vacuum furnace;
step 13: and (5) cooling.
7. The heat treatment process according to claim 6, wherein in the step 12, the temperature of the vacuum furnace is raised to 500-550 ℃ and the holding time is 1-2 hours.
8. The heat treatment process according to claim 7, wherein in the step 12, the holding time is 2 hours.
9. The heat treatment process of claim 1, wherein the laser selective melting alloy comprises an alloy sample and an alloy member.
10. A laser selective area melting alloy, which is characterized in that the alloy is obtained by adopting the heat treatment process of any one of claims 1-9, wherein the room temperature yield strength of the laser selective area melting alloy is more than or equal to 1020MPa, the tensile strength is more than or equal to 1180MPa, the elongation is more than or equal to 20%, the yield strength at 950 ℃ is more than or equal to 220MPa, the tensile strength is more than or equal to 290MPa, and the elongation is more than or equal to 25%.
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