Method for eliminating defects of TiAl alloy blade through electron beam selective melting printing by hot isostatic pressing

Abstract

The invention provides a method for eliminating defects through hot isostatic pressing of TiAl alloy blades printed through electron beam selective melting, and belongs to the field of hot isostatic pressing of engine blades. According to the method, after a printed blade blank is cleaned, air is exhausted through circulating argon charging and discharging, then heating and pressurizing are conducted, the three-step hot isostatic pressing process is conducted, and preparation of the TiAl alloy blade is completed. During hot isostatic pressing, the blade is arranged in a tool to prevent deformation. TiAl blades of different sizes can be treated, and the TiAl blades comprise low-pressure turbine blades, high-pressure turbine blades, axial flow hollow blades and the like. The blade subjected to hot isostatic pressing through the method is in a compact and defect-free state through CT detection, and printing defects are completely eliminated. According to the method, through asynchronous load holding of temperature and pressure, closed annihilation of defects is promoted under the condition of low temperature and pressure by utilizing mechanical characteristics of different microstructures, the problem of printing of the internal defects of the TiAl alloy blade is solved, and the method has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of hot isostatic pressing of engine blades, and in particular to a multi-step hot isostatic pressing method for eliminating defects of TiAl alloy blades by electron beam selective melting printing, which is suitable for electron beam selective melting of low-pressure turbine blades, electron beam selective melting of hollow guide blades, electron beam selective melting of high-pressure turbine blades and other parts. Background Art

[0002] TiAl alloy has low density, excellent high temperature strength, specific strength and specific modulus, as well as oxidation resistance and creep resistance. Compared with nickel-based alloys, the density of TiAl alloy is only half, so it has a significant weight reduction effect. It has been applied in fields such as aircraft engines and automobile engines. Additive manufacturing is a preparation method that can quickly prepare TiAl alloy parts with complex shapes. It achieves near-net shaping by heating, melting and printing the alloy powder layer by layer. The electron beam selective melting additive manufacturing method has the characteristics of high vacuum and high preheating temperature, which can effectively avoid the influence of oxidation and stress during the printing process. It is currently the most mature preparation method for industrial production of TiAl alloy prints.

[0003] The deposited density of TiAl alloy electron beam selective melting additive manufacturing parts usually cannot reach 100%, and the defects include pores, delamination, and lack of fusion, which have a serious impact on the mechanical properties of TiAl alloy, especially fatigue properties. Hot isostatic pressing is a processing method that can effectively eliminate defects in casting and additive manufacturing alloys, and is currently widely used in the post-processing process of additive manufacturing.

[0004] Hot isostatic pressing can effectively eliminate small defects such as pores. The defect closure process is a process in which the microstructures creep and then contact each other to achieve connection, and finally annihilate the defects. Hot isostatic pressing of TiAl alloys faces a series of problems: TiAl alloys have high high-temperature strength and good creep resistance of the full-lamellar structure, so the temperature and pressure requirements for hot isostatic pressing are high, currently up to 1290℃ and 230MPa. Excessively high process parameters increase costs sharply; insulation at high processing temperatures will also cause degradation of the microstructure, and the slow cooling rate of the hot isostatic pressing furnace will cause coarsening of grains and an increase in equiaxed γ grains; high processing temperatures and pressures will also cause deformation of parts such as blades. These problems have become bottlenecks in the application of hot isostatic pressing technology for TiAl alloy blades.

[0005] For example, Chinese patent CN 116275051 A discloses a TiAl / TC4 alloy laminated composite plate and its preparation method. The method performs hot isostatic pressing on the powder blank, first keeping it at 500-800℃ for 1-2h and pressure of 40-60Mpa. The purpose of this step is to achieve connection and pre-sintering between powders, and then heating it to 1250-1350℃ and pressure of 150-250MPa for 3-5h. This step is mainly to achieve diffusion and connection between TC4 and TiAl. This method is designed for sintering, diffusion and connection of powders, and dense forming depends on the subsequent rolling process. There is no parameter design for defect closure of TiAl alloy.

[0006] Chinese patent CN 111975003 A discloses a method for regulating the full lamellar structure of titanium aluminum alloy. In this method, TNM powder is sealed in a pure Ti package for hot isostatic pressing. The hot isostatic pressing temperature is 1230-1260°C, the pressure is 130-170MPa, and the holding time is 3-5h. A TNM alloy sample is obtained with a density of 99.98%. This method only uses one step of hot isostatic pressing for processing. Excessive temperature and holding time will inevitably cause grain coarsening, thereby reducing the mechanical properties of the alloy. In addition, the density of 99.98% is not ideal. If it is to be further improved, the pressure and processing time will be significantly increased.

[0007] Chinese patent CN 117721346 A discloses a method for preparing a SiC fiber reinforced titanium alloy composite blade, in which the composite material is loaded into a titanium alloy sheath and a steel sheath, and then formed by hot isostatic pressing, and the parameters include: temperature: 700-1300°C; pressure: 100-180MPa; time: 1-10h. The temperature and pressure of this method are relatively low, and the main purpose is to achieve the combination between titanium alloy and SiC fiber, and it is not suitable for hot isostatic pressing of TiAl alloy. Summary of the invention

[0008] In order to solve the technical problems existing in the hot isostatic pressing process of TiAl alloy electron beam selective additive manufacturing blades in the prior art, the present invention provides a method that can fully press the defects of TiAl alloy electron beam selective additive manufacturing blades and adjust the microstructure at a lower pressure and temperature. The technical solution is as follows:

[0009] A method for eliminating defects of hot isostatic pressing of TiAl alloy blades printed by electron beam selective melting is characterized in that after the printed blade blank is cleaned, a three-step hot isostatic pressing process is performed by cyclically filling and discharging argon gas to exhaust air and then heating and pressurizing to complete the preparation of the TiAl alloy blade; during hot isostatic pressing, the blade must be loaded into a tool to prevent deformation; the method can process TiAl blades of different sizes, including low-pressure turbine blades, high-pressure turbine blades, axial flow hollow blades, etc. Before hot isostatic pressing of the blade, the support and powder in the gap of the blade blank are removed, and the blade blank surface roughness greater than Ra30 is sandblasted.

[0010] Furthermore, before specifying specific parameters, it is necessary to measure the thermophysical properties of the alloy used, such as the melting point, Tα point and minimum phase transition point temperature; after determining the hot isostatic pressing temperature, it is necessary to measure the strength and creep properties of the specific microstructure alloy at the relevant temperature.

[0011] Furthermore, in the first step of treatment, vacuum is first evacuated to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3 Pa, start to increase the temperature and pressure; first increase the temperature to 1140℃~1240℃, with a heating rate of no more than 10℃ / minute, and when the temperature reaches 800-900℃, start to increase the pressure to 140MPa~150MPa, with a pressure increase rate of no more than 1MPa / minute.

[0012] Furthermore, in the second step of treatment, the pressure is first increased to 150MPa~230MPa, and the pressure increase rate is not greater than 0.5MPa / minute. After reaching the pressure, the temperature is increased again, and the heating rate is not greater than 5℃ / minute. The temperature range is 1250℃~1300℃ and the treatment is stopped when it reaches the temperature, so as to obtain a sufficient number of lamellar structures while pressing the defects.

[0013] Furthermore, during the third step, the pressure is kept constant and the temperature is lowered at a rate of not less than 8°C / minute. When the temperature drops below 900°C, the pressure and temperature are lowered and gradually dropped to room temperature and atmospheric pressure.

[0014] Furthermore, when the length of the processed blade is greater than 50 mm, anti-deformation tooling is required, the blade parts should be kept at least 2 cm apart, and should be cleaned before loading into the furnace to prevent surface contamination.

[0015] Furthermore, the tooling can be taken out when the temperature inside the furnace drops to room temperature, 100°C. At this time, the temperature inside the tooling is still relatively high, and the tooling can be opened and the blades can be taken out only after the tooling has cooled for several hours.

[0016] Furthermore, the furnace test rod of the hot isostatically pressed blade was dissected, and the internal block was made into a metallographic block. After observation under a microscope, the defects with internal diameter less than 50μm were completely eliminated, while defects larger than 100μm were difficult to eliminate by hot isostatic pressing.

[0017] Furthermore, the blade is subjected to CT inspection after hot isostatic pressing, and the voxel size or resolution used needs to be less than 25μm. After the scan is completed, the part 0.5mm inward from the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50μm in the post-processing results.

[0018] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0019] The above scheme, the present invention proposes a method for eliminating defects of TiAl alloy blades by multi-step hot isostatic pressing printed by electron beam selective melting, solves the technical problems existing in the hot isostatic pressing process of TiAl alloy electron beam selective additive manufacturing blades, and provides a method that can fully press the defects of TiAl alloy electron beam selective additive manufacturing blades and adjust the microstructure at lower pressure and temperature, thereby synergistically improving the density and mechanical properties of electron beam selective additive manufacturing products.

[0020] The present invention adopts a multi-step heat treatment design, selects to pressurize in the microstructure temperature range with strong deformation ability of the alloy, and directly cools down after the temperature reaches Tα, thereby ensuring a sufficient number of lamellar structures to meet performance requirements such as fatigue creep.

[0021] The present invention can eliminate defects at lower temperature and pressure through multi-step design, and prevent degradation of microstructure and deformation of components.

[0022] The present invention provides a series of operation methods for cleaning, placing, tooling and sampling of blades through different hot isostatic pressing tests of blades, which are universally applicable to different blades.

[0023] The present invention effectively identifies the defect elimination of blades after hot isostatic pressing by means of anatomical metallographic analysis, CT detection and the like, and provides a standard for defect elimination.

[0024] The blades hot isostatically pressed using this method are found to be dense and defect-free by CT inspection, and the printing defects are completely eliminated. Since this method uses asynchronous temperature and pressure loading and utilizes the mechanical properties of different microstructures to promote the closure and annihilation of defects under lower temperature and pressure conditions, the problem of internal defects in printed TiAl alloy blades is solved. Compared with other traditional methods, through parameter design optimization and post-processing detection method selection, the processed blade parts can effectively eliminate defects and retain good microstructure and mechanical properties. The method has strong applicability and high efficiency, is conducive to large-scale industrial production and promotion, and has broad application prospects. Description of the drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 This is a scanning electron microscope image of the microstructure before hot isostatic pressing in Example 1 of the present invention, in which obvious holes can be seen;

[0027] Figure 2 This is a scanning electron microscope image of the microstructure after hot isostatic pressing in Example 1 of the present invention, in which there are no obvious holes, indicating that the holes have been healed;

[0028] Figure 3 This is a scanning electron microscope image of the microstructure after hot isostatic pressing in Example 2 of the present invention, where obvious holes can be seen;

[0029] Figure 4 This is a scanning electron microscope image of the microstructure after hot isostatic pressing in Example 2 of the present invention, in which there are no obvious holes, indicating that the holes have been healed;

[0030] Figure 5 This is a scanning electron microscope image of the microstructure after hot isostatic pressing in Example 2 of the present invention, and the morphology of the hole healing is very obvious;

[0031] Figure 6 The test bar after hot isostatic pressing in Example 3 of the present invention is contaminated by gas and impurities on the surface because it is not protected by tooling;

[0032] Figure 7 This is the blade after hot isostatic pressing in Example 3 of the present invention, which is protected by tooling, has a relatively clean surface, and has no deformation;

[0033] Figure 8 This is the performance of the blade furnace test bar after hot isostatic pressing in Example 4 of the present invention, and the strength reaches 700MPa;

[0034] Fig. 9 This is the blade after hot isostatic pressing in Example 4 of the present invention. It is protected by tooling, has a relatively clean surface, and has no deformation. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0036] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0037] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same. "of", "corresponding" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same.

[0038] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0039] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0040] A method for eliminating defects of a TiAl alloy blade by multi-step hot isostatic pressing using electron beam selective melting printing, the method being capable of processing TiAl blades of different sizes, including low-pressure turbine blades, high-pressure turbine blades, axial flow hollow blades, etc., and comprising the following steps.

[0041] (1) Check the blade surface. If there is support or powder in the holes and grooves, it needs to be removed first. If the surface roughness of the blade blank is greater than Ra30, electrochemical polishing or sandblasting is required.

[0042] (2) Before formulating specific hot isostatic pressing parameters, it is necessary to determine the thermophysical parameters of the alloy used, such as the melting point, Tα point, and the lowest phase transition point temperature. After determining the hot isostatic pressing temperature, it is necessary to determine the strength and creep properties of the specific microstructure alloy at the relevant temperature.

[0043] (3) In the first step of treatment, first vacuum to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3Pa, start to increase temperature and pressure. First, increase the temperature to 1140℃~1240℃ in the two-phase region, with a heating rate of no more than 10℃ / min. When the temperature reaches the lowest phase change point of 800-900℃, start to increase the pressure to 140MPa~150MPa, with a pressure increase rate of no more than 1MPa / min.

[0044] (4) In the second step, according to the strength of the alloy at the maximum steady-state creep rate at the temperature determined in the first step, the pressure is first increased to 150MPa~230MPa, and the pressure increase rate is not more than 0.5MPa / min. After reaching the pressure, the temperature is increased again, and the heating rate is not more than 5℃ / min. The temperature range is 1250℃~1300℃ and the treatment is stopped when the temperature is reached. A sufficient number of lamellar structures are obtained while the defects are pressed together.

[0045] (5) During the third step, the pressure is kept constant and the temperature is lowered. The cooling rate is not less than 8°C / min. The specific cooling rate can be obtained through the CCT curve of the heat treatment of the material. When the temperature drops below 900°C, the pressure and temperature are reduced and gradually dropped to room temperature and atmospheric pressure.

[0046] (6) When the length of the processed blade is greater than 50 mm, anti-deformation tooling is required, and the blade parts should be kept at least 2 cm apart.

[0047] (7) When the temperature inside the furnace drops to room temperature, 100°C, the tooling can be removed. At this time, the temperature inside the tooling is still relatively high. Wait for the tooling to cool down for several hours before opening the tooling and removing the blades.

[0048] (8) The hot isostatically pressed blade test bar was dissected and the internal block was made into a metallographic block. After observation under a microscope, the defects with an internal diameter less than 50 μm were completely eliminated, while defects larger than 100 μm were difficult to eliminate by hot isostatic pressing.

[0049] (9) The blades are subjected to CT inspection after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion inside the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

[0050] The following are specific embodiments:

[0051] Example 1

[0052] The method is used to process a TNM-TiAl blade with a blade height of 70 mm, and includes the following steps.

[0053] (1) Check the blade surface. The blade support structure has been removed and the surface roughness of the blade blank is less than Ra30.

[0054] (2) The melting point of TNM alloy is about 1600℃, the treatment temperature should be 0.7-0.9 times Tm, that is, 1120℃-1440℃, Tα point is about 1240℃, and the lowest phase transition point is about 850℃. The strength of the dual-state structure is about 600MPa, the elongation is about 0.8-1.6%, and the strength of the full lamellar structure is about 800MPa, and the elongation is about 0.6-0.8%.

[0055] (3) In the first step of treatment, first vacuum to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3 Pa, start to increase temperature and pressure. First, increase the temperature to 1180℃ in the two-phase region at a rate of 10℃ / min. When the temperature reaches the lowest phase transition point of 850℃, start to increase the pressure to 150MPa at a rate of 1MPa / min.

[0056] (4) In the second step, based on the strength of the alloy at the maximum steady-state creep rate at the temperature determined in the first step, the pressure is first increased to 220 MPa at a rate of 0.5 MPa / min. After reaching the pressure, the temperature is then increased at a rate of 5°C / min to 1240°C. The temperature is then raised to stop at the temperature reached, so that a sufficient number of lamellar structures can be obtained while closing the defects.

[0057] (5) During the third step, the pressure is kept constant and the temperature is lowered at a rate of 8°C / min. When the temperature drops below 850°C, the pressure and temperature are lowered and gradually dropped to room temperature and atmospheric pressure.

[0058] (6) The length of the processed blade is 70 mm, and anti-deformation tooling is required. The blade parts should be kept at a distance of 3 cm.

[0059] (7) When the temperature inside the furnace drops to room temperature, 100°C, the tooling can be removed. At this time, the temperature inside the tooling is still relatively high. Wait for the tooling to cool down for several hours before opening the tooling and removing the blades.

[0060] (8) The hot isostatically pressed blade test bar was dissected to obtain the internal block and made into a metallographic block. The scanning electron microscope image of the microstructure before hot isostatic pressing is shown in the figure. Figure 1 As shown, there are obvious holes. The microstructure after hot isostatic pressing is shown in Figure 2 As shown, the holes have been pressed closed.

[0061] (9) The blades are subjected to CT inspection after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion inside the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

[0062] Example 2

[0063] The method is used to process a TNM-TiAl blade with a blade height of 270 mm, and includes the following steps.

[0064] (1)-(5) are the same as in Example 1.

[0065] (6) The length of the blade to be processed is 270 mm, and an extended anti-deformation tooling is required, and the blade parts are kept at a distance of 5 cm.

[0066] (7) When the temperature inside the furnace drops to room temperature, 100°C, the tooling can be removed. At this time, the temperature inside the tooling is still relatively high. Wait for the tooling to cool down for several hours before opening the tooling and removing the blades.

[0067] (8) The hot isostatically pressed blade test bar was dissected to obtain the internal block and made into a metallographic block. The scanning electron microscope image of the microstructure before hot isostatic pressing is shown in the figure. Figure 3 As shown, there are obvious holes. The microstructure after hot isostatic pressing is shown in Figure 4 As shown in the figure, the hole has been pressed together, and the hole area after pressing is as follows Figure 5 shown.

[0068] (9) The blades are subjected to CT inspection after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion inside the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

[0069] Example 3

[0070] The method is used to process a 4822-TiAl blade with a blade height of 70 mm, and includes the following steps.

[0071] (1) Check the blade surface. The blade support structure has been removed and the surface roughness of the blade blank is less than Ra30.

[0072] (2) The melting point of 4822 alloy is about 1550℃, the treatment temperature should be 0.7-0.9 times Tm, that is, 1085℃-1395℃, Tα point is about 1260℃, and the lowest phase transition point is about 900℃. The strength of the dual-state structure is about 500MPa, the elongation is about 1.5-3%, the strength of the full lamellar structure is about 600MPa, and the elongation is about 0.8-1.5%.

[0073] (3) In the first step of treatment, first vacuum to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3Pa, start to increase temperature and pressure. First, increase the temperature to 1260℃ in the two-phase region at a heating rate of 8℃ / min. When the temperature reaches the lowest phase transition point of 900℃, start to increase the pressure to 140MPa at a rate of 0.8MPa / min.

[0074] (4) In the second step of treatment, based on the strength of the alloy at the maximum steady-state creep rate at the temperature determined in the first step, the pressure is first increased to 200 MPa at a rate of 0.4 MPa / min. After reaching the pressure, the temperature is then increased at a rate of 4°C / min to 1320°C. The temperature is then raised to stop at the temperature reached, so that a sufficient number of lamellar structures can be obtained while closing the defects.

[0075] (5) During the third step, the pressure is kept constant and the temperature is lowered at a rate of 8°C / min. When the temperature drops below 900°C, the pressure and temperature are lowered and gradually dropped to room temperature and atmospheric pressure.

[0076] (6) The length of the blade to be processed is 70 mm. Anti-deformation tooling is required. The blade parts are kept at a distance of 2 cm. The furnace test rod without anti-deformation tooling is as follows: Figure 6 As shown, there is contamination on the surface.

[0077] (7) When the temperature inside the furnace drops to room temperature, 100°C, the tooling can be removed. At this time, the temperature inside the tooling is still high. Wait for the tooling to cool down for several hours before opening the tooling to remove the blades. Figure 7 shown.

[0078] (8) The hot isostatically pressed blade test bar was dissected and the internal block was made into a metallographic block. After observation under a microscope, the defects with an internal diameter less than 50 μm were completely eliminated, while defects larger than 100 μm were difficult to eliminate by hot isostatic pressing.

[0079] (9) The blades are subjected to CT inspection after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion inside the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

[0080] Example 4

[0081] The method is used to process a high Nb-TiAl blade with a blade height of 270 mm, and includes the following steps.

[0082] (1) Check the blade surface. The blade support structure has been removed and the surface roughness of the blade blank is less than Ra30.

[0083] (2) The melting point of TNM alloy is about 1650℃, the treatment temperature should be 0.7-0.9 times Tm, that is, 1155℃-1485℃, Tα point is about 1290℃, and the lowest phase transition point is about 900℃. The strength of the dual-state structure is about 750MPa, the elongation is about 0.5-1.5%, and the strength of the full lamellar structure is about 900MPa, and the elongation is about 0.5-1.0%.

[0084] (3) In the first step of treatment, first vacuum to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3 Pa, start to increase temperature and pressure. First, increase the temperature to 1260℃ in the two-phase region at a rate of 10℃ / min. When the temperature reaches the lowest phase transition point of 900℃, start to increase the pressure to 150MPa at a rate of 1MPa / min.

[0085] (4) In the second step of treatment, based on the strength of the alloy at the maximum steady-state creep rate at the temperature determined in the first step, the pressure is first increased to 230 MPa at a rate of 0.5 MPa / min. After reaching the pressure, the temperature is then increased at a rate of 5°C / min to 1290°C. The temperature is then raised to stop at the temperature reached, so that a sufficient number of lamellar structures can be obtained while closing the defects.

[0086] (5) During the third step, the pressure is kept constant and the temperature is lowered at a rate of 8°C / min. When the temperature drops below 900°C, the pressure and temperature are lowered and gradually dropped to room temperature and atmospheric pressure.

[0087] (6) The length of the blade to be processed is 270 mm, and an extended anti-deformation tooling is required, and the blade parts are kept at a distance of 3 cm.

[0088] (7) When the temperature inside the furnace drops to room temperature, 100°C, the tooling can be removed. At this time, the temperature inside the tooling is still high. Wait for the tooling to cool down for several hours before opening the tooling to remove the blades. Figure 8 The tensile properties of the furnace test rods show that the high strength reaches 700MPa. Fig. 9 As shown, the surface is smooth and without deformation.

[0089] (8) The hot isostatically pressed blade test bar was dissected and the internal block was made into a metallographic block. After observation under a microscope, the defects with an internal diameter less than 50 μm were completely eliminated, while defects larger than 100 μm were difficult to eliminate by hot isostatic pressing.

[0090] (9) The blades are subjected to CT inspection after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion inside the surface needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

[0091] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0092] In the present invention, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0093] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0094] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing, characterized in that: After the printed blade blank is cleaned, a three-step hot isostatic pressing process is performed by circulating argon gas to exhaust the air and then increasing the temperature and pressurizing to complete the preparation of the TiAl alloy blade; during hot isostatic pressing, the blade must be loaded into a tool to prevent deformation; the method can process TiAl blades of different sizes, including low-pressure turbine blades, high-pressure turbine blades, and axial flow hollow blades. Before hot isostatic pressing of the blade, the support and powder in the gap of the blade blank are removed, and the blade blank surface roughness greater than Ra30 is sandblasted.

2. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: Before specifying specific parameters, it is necessary to measure the melting point, Tα point and lowest phase transition point temperature thermophysical parameters of the alloy used; after determining the hot isostatic pressing temperature, it is necessary to measure the strength and creep properties of the specific microstructure alloy at the relevant temperature.

3. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: In the first step of treatment, first vacuum to 10 -2 Pa, filled with inert gas to 10 -1 Pa, cycle this process several times and then evacuate to 10 -3 Pa, start to increase the temperature and pressure; first increase the temperature to 1140℃~1240℃, with a heating rate of no more than 10℃ / minute, and when the temperature reaches 800-900℃, start to increase the pressure to 140MPa~150MPa, with a pressure increase rate of no more than 1MPa / minute.

4. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: In the second step of treatment, the pressure is first increased to 150MPa~230MPa, and the pressure increase rate is not more than 0.5MPa / minute. After reaching the pressure, the temperature is increased again, and the heating rate is not more than 5℃ / minute. The temperature range is 1250℃~1300℃ and the treatment is stopped when it reaches the temperature. A sufficient number of lamellar structures are obtained while pressing the defects.

5. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: During the third step, the pressure is kept constant and the temperature is lowered at a rate of not less than 8°C / minute. When the temperature drops below 900°C, the pressure and temperature are lowered and gradually dropped to room temperature and atmospheric pressure.

6. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: When the length of the processed blade is greater than 50mm, anti-deformation tooling is required. The blade parts should be kept at least 2cm apart and should be cleaned before loading into the furnace to prevent surface contamination.

7. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: The tooling can be taken out when the temperature inside the furnace drops to room temperature, 100°C. At this time, the temperature inside the tooling is still high. The tooling can be opened and the blades can be taken out only after the tooling has cooled for several hours.

8. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: The furnace test rod of the hot isostatic pressed blade was dissected and the internal block was made into a metallographic block. After observation under a microscope, the defects with internal diameter less than 50μm were completely eliminated, while the defects larger than 100μm were difficult to eliminate by hot isostatic pressing.

9. The method for eliminating defects of TiAl alloy blades by electron beam selective melting printing and hot isostatic pressing according to claim 1, characterized in that: The blades are CT-tested after hot isostatic pressing. The voxel size or resolution used needs to be less than 25 μm. After the scan is completed, the 0.5 mm portion from the surface to the inside needs to be removed in the post-processing stage. Similarly, there should be no defects with an equivalent diameter of less than 50 μm in the post-processing results.

Images