Stability evaluation method for long-time thermal exposure of additive manufacturing high-temperature titanium alloy

Abstract

The invention discloses a stability evaluation method for long-time thermal exposure of an additive manufacturing high-temperature titanium alloy. The method comprises the following steps: step 1, forming a high-temperature titanium alloy blank by adopting laser additive manufacturing; 2, the formed blank is subjected to heat treatment; 3, machining the blank piece subjected to heat treatment into a test piece; 4, carrying out a long-time thermal exposure test on the test piece; 5, performing structure and performance evaluation on the test piece reaching the specified test time; the stability evaluation method for long-time thermal exposure of the additive manufacturing high-temperature titanium alloy can accurately reflect the performance degradation rule of the laser additive manufacturing high-temperature titanium alloy part under the simulated aero-engine service condition, and is easy to implement and comprehensive in evaluation; the method is particularly suitable for initial material selection in the aviation component design stage and structure property evaluation of additive manufacturing forming components.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and in particular, to a method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure. Background Technology

[0002] The aviation manufacturing industry is a field full of opportunities and challenges. With the continuous development of my country's economy and the increasing demand for air transport, the demand for aviation manufacturing will continue to expand. The future development of aircraft is moving towards higher performance and lower energy consumption. As the core power unit of aircraft, engines require lightweight design to withstand extreme operating environments such as high temperatures and high pressures, thus placing more stringent requirements on component materials and corresponding manufacturing processes. Additive manufacturing (such as laser powder bed melting) possesses extremely high processing precision, enabling the free "growth" of highly complex structures into near-net-shape integrated forms. This effectively reduces subsequent processing steps and greatly expands the design "space" of component structures, making it highly compatible with the needs of the aviation equipment manufacturing industry. Titanium alloys, due to their excellent properties such as lightweight and high specific strength, are one of the commonly used materials for aircraft engines. As the operating temperature of aircraft engines continues to increase, higher requirements are being placed on the operating temperature of titanium alloys. Developing high-temperature resistant titanium alloys is of great significance for the effective weight reduction and performance improvement of future aircraft engines. The history of high-temperature titanium alloys can be traced back to the α+β type titanium alloy Ti-6Al-4V developed in the United States in 1954, which can be used at a temperature of 350℃. With the rapid development of the aerospace industry, high-temperature titanium alloys with higher operating temperatures than Ti-6Al-4V alloys have emerged one after another. The long-term operating temperature of high-temperature titanium alloys has gradually increased to 600℃. People are paying more attention to the evaluation of the microstructure and performance stability of titanium alloys in service at high temperatures.

[0003] Under long-term high-temperature service conditions, the microstructure of materials (such as the size, morphology, and distribution of α and β phases) may undergo changes such as coarsening, phase transformation, or oxidation, leading to corresponding changes in the material's mechanical properties (such as strength, plasticity, and fatigue performance). Accurately assessing the microstructure and performance stability of materials under service conditions is crucial for the design of aircraft engine components. However, current evaluations of the forming microstructure and performance of additively manufactured high-temperature titanium alloys mainly focus on relatively singular conditions, failing to comprehensively consider the impact of microstructure and performance changes under long-term service thermal exposure. Therefore, accurately evaluating the microstructure and performance stability of additively manufactured high-temperature titanium alloys under long-term service thermal exposure is an urgent problem to be solved. Summary of the Invention

[0004] This invention provides a method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure, in order to solve the technical problem of how to accurately evaluate the stability of the microstructure and properties of additively manufactured high-temperature titanium alloys under long-term service thermal exposure.

[0005] According to one aspect of the present invention, a method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure is provided, comprising the following steps: Step 1: High-temperature titanium alloy blanks are formed using laser additive manufacturing; Step 2: Heat treatment is performed on the formed blank to adjust the non-equilibrium structure and residual stress in the deposited state. Step 3: The heat-treated blank is machined into a test piece to treat the surface roughness of the sample, etc., so that subsequent tests can be carried out. Step 4: Conduct long-term heat exposure tests on the test specimens to simulate their service behavior under actual working conditions; Step 5: Organize and evaluate the performance of the test pieces that have reached the specified test time.

[0006] In this embodiment, in step 1, laser additive manufacturing is laser powder bed melting (LPBF) forming.

[0007] In this embodiment, in step 1, the process window for laser additive manufacturing includes laser input power, laser scanning speed, scanning layer thickness, and laser scanning spacing. The laser input power ranges from 90 to 350W, the laser scanning speed ranges from 500 to 2000 mm / s, the scanning layer thickness ranges from 0.03 to 0.06 mm, and the laser scanning spacing ranges from 0.05 to 0.1 mm.

[0008] In this embodiment, in step 2, the heat treatment methods are solution treatment and aging treatment. The solution treatment is performed at 940~1020 ℃ / 2~4 h / AC, and the aging treatment is performed at 650~780 ℃ / 2~8 h / AC.

[0009] In this embodiment, in step 4, the test equipment for the long-term heat exposure test includes a heating furnace and a support container. The heating furnace is an air atmosphere furnace and is equipped with a temperature controller with a control accuracy of 0.5. The temperature difference in the uniform temperature zone should not exceed ±5℃. The support container should not interact with the test specimen at the test temperature.

[0010] In this embodiment, in step 4, the test temperature range of the long-term heat exposure test is a constant temperature of 300℃ to 650℃, and the test heat exposure duration ranges from 100 to 3000 hours.

[0011] In this embodiment, step 5 includes evaluation of the surface oxidation behavior of the test specimen, evaluation of microstructure changes, evaluation of tensile properties, and evaluation of fatigue properties.

[0012] In this embodiment, the evaluation of surface oxidation behavior includes oxidation product analysis, oxide layer thickness analysis, and oxygen diffusion degree analysis.

[0013] In this embodiment, the evaluation of microstructure changes includes the analysis of changes in the proportion of phase composition.

[0014] In this embodiment, the test temperatures for the tensile performance evaluation and the fatigue performance evaluation include the long-term service temperature and the maximum service temperature. The tensile performance evaluation and the fatigue performance evaluation also include a comparison of the performance with the unexposed sample and the performance change pattern.

[0015] The present invention has the following beneficial effects: The present invention provides a method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure. The method involves processing high-temperature titanium alloys formed by laser additive manufacturing into test pieces, and then subjecting the test pieces to tests simulating the thermal exposure service conditions of an aero-engine. This method accurately reflects the performance degradation law of laser-additively manufactured high-temperature titanium alloy components under simulated aero-engine service conditions. The method is simple to implement and provides comprehensive evaluation, making it particularly suitable for the initial material selection in the design phase of aero-components and the evaluation of the microstructure and performance of additively manufactured components.

[0016] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of a preferred embodiment of the stability evaluation method for additive manufacturing high-temperature titanium alloys under long-term thermal exposure. Figure 2 This is a sample image of a high-temperature titanium alloy tensile property test specimen after long-term heat exposure in an embodiment of the present invention. Figure 3 This is a sample image of a high-temperature titanium alloy fatigue performance test specimen after long-term heat exposure in an embodiment of the present invention. Figure 4 This is an analysis diagram of oxidation products on the surface of a high-temperature titanium alloy after long-term heat exposure in an embodiment of the present invention; Figure 5 This is an oxidation diagram of the high-temperature titanium alloy surface after 1000 hours of long-term heat exposure in an embodiment of the present invention; Figure 6 This is an oxidation diagram of a high-temperature titanium alloy surface after 3000 hours of long-term thermal exposure, as shown in this embodiment of the invention. Figure 7 This is a diagram of the original microstructure of a high-temperature titanium alloy that has not undergone prolonged heat exposure in an embodiment of the present invention. Figure 8 This is a microstructure diagram of a high-temperature titanium alloy after 1000 hours of long-term heat exposure in an embodiment of the present invention. Figure 9 This is a microstructure diagram of a high-temperature titanium alloy after 3000 hours of long-term heat exposure in an embodiment of the present invention. Figure 10 These are the tensile property change curves of high-temperature titanium alloys after no long-term heat exposure and after heat exposure for different durations, as described in the embodiments of the present invention. Figure 11 This is a fracture morphology image of a high-temperature titanium alloy tensile specimen after long-term heat exposure in an embodiment of the present invention. Figure 12 These are comparison curves of the low-cycle fatigue properties of high-temperature titanium alloys after no long-term heat exposure and after heat exposure for different durations, as described in this embodiment of the invention. Figure 13 This is a fracture morphology diagram of a high-temperature titanium alloy fatigue specimen after long-term heat exposure in an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, and back), the orientation or positional relationship of the directional indications is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the embodiments according to this application and simplifying the description, and is not intended to indicate or imply that the device or unit referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the embodiments according to this application.

[0020] Furthermore, if the embodiments of this invention involve descriptions using terms such as "first," "second," and "third," these terms are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," or "third" may explicitly or implicitly include at least one of those features. The term "multiple" refers to two or more unless otherwise explicitly defined. Terms such as "installed," "connected," "attached," and "fixed" should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "attached" can be a direct connection or an indirect connection through an intermediate medium.

[0021] If the words "and / or" or "and / or" appear in the text, they mean three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that satisfies both A and B. In addition, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] To better understand the above technical solution, the following detailed explanation is provided in conjunction with the accompanying drawings.

[0023] Please refer to the following: Figures 1 to 13 The stability evaluation method for long-term thermal exposure of additively manufactured high-temperature titanium alloys in this embodiment includes the following steps: Step 1: High-temperature titanium alloy blanks are formed using laser additive manufacturing; Step 2: Heat treatment is performed on the formed blank to adjust the non-equilibrium structure and residual stress in the deposited state. Step 3: The heat-treated blank is machined into a test piece to treat the surface roughness of the sample, etc., so that subsequent tests can be carried out. Step 4: Conduct long-term heat exposure tests on the test specimens to simulate their service behavior under actual working conditions; Step 5: Organize and evaluate the performance of the test pieces that have reached the specified test time.

[0024] The stability evaluation method for long-term thermal exposure of additively manufactured high-temperature titanium alloys in this embodiment involves processing high-temperature titanium alloys formed by laser additive manufacturing into test pieces, and then conducting tests on the test pieces under simulated thermal exposure service conditions of aero-engines. This accurately reflects the performance degradation law of laser-additively manufactured high-temperature titanium alloy components under simulated aero-engine service conditions. The method is simple to implement and provides comprehensive evaluation, making it particularly suitable for the initial material selection in the design phase of aero-components and the evaluation of the microstructure and performance of additively manufactured components.

[0025] In this embodiment, in step 1, laser additive manufacturing is laser powder bed melting (LPBF) forming.

[0026] In this embodiment, the process window for laser additive manufacturing in step 1 includes laser input power, laser scanning speed, scanning layer thickness, and laser scanning spacing. The laser input power ranges from 90 to 350 W, the laser scanning speed ranges from 500 to 2000 mm / s, the scanning layer thickness ranges from 0.03 to 0.06 mm, and the laser scanning spacing ranges from 0.05 to 0.1 mm. The forming parameter range selected in this embodiment is determined based on the defect size and surface quality of the formed part in actual production. If the range exceeds the upper limit of the forming parameter range in this embodiment, the laser input energy density is too high, causing the molten pool to be unstable and resulting in poor surface quality of the formed part; if the range is lower than the lower limit of the forming parameter range in this embodiment, the laser input energy density is insufficient, resulting in large areas not being fused and the formed alloy having a low degree of density.

[0027] In this embodiment, step 2 involves a solution treatment and an aging treatment. The solution treatment is performed at 940~1020 ℃ for 2~4 h / AC, and the aging treatment is performed at 650~780 ℃ for 2~8 h / AC. The alloy treated with the selected heat treatment parameters in this embodiment exhibits the best balance of strength and plasticity, resulting in the best overall performance.

[0028] In this embodiment, in step 4, the test equipment for the long-term heat exposure test includes a heating furnace and a support container. The heating furnace is an air atmosphere furnace and is equipped with a temperature controller with a control accuracy of 0.5. The temperature difference in the uniform temperature zone should not exceed ±5℃. The support container should not interact with the test specimen at the test temperature.

[0029] In this embodiment, in step 4, the test temperature range for the long-term heat exposure test is a constant temperature of 300℃ to 650℃, and the test heat exposure duration ranges from 100 to 3000 hours. Optionally, the test temperature for the long-term heat exposure test includes the long-term service temperature and the maximum service temperature. In this embodiment, the selection of the test temperature and test duration range is determined based on the temperature range of the high-temperature titanium alloy component under actual service conditions and the component maintenance cycle.

[0030] In this embodiment, step 5 includes evaluation of the surface oxidation behavior of the test specimen, evaluation of microstructure changes, evaluation of tensile properties, and evaluation of fatigue properties.

[0031] In this embodiment, the evaluation of surface oxidation behavior includes oxidation product analysis, oxide layer thickness analysis, and oxygen diffusion degree analysis.

[0032] In this embodiment, the evaluation of microstructure changes includes the analysis of changes in the proportion of phase composition.

[0033] In this embodiment, the tensile performance evaluation and the fatigue performance evaluation also include a comparison of the performance with that of the unexposed specimen and the performance change pattern.

[0034] The method for evaluating the microstructure and performance stability of additively manufactured high-temperature titanium alloys under long-term heat exposure in this embodiment includes the following steps: Step 1: Select Ti150 high-temperature titanium alloy as the object of implementation, and use laser additive manufacturing to form high-temperature titanium alloy blanks; the forming process parameters of laser powder bed melting forming of Ti150 alloy are: laser input power range of 150W, laser scanning speed range of 1250mm / s, scanning layer thickness range of 0.03mm, and laser scanning spacing range of 0.09mm.

[0035] Step 2: Heat treatment of the formed blank; the heat treatment regime for the formed sample is as follows: solution treatment at 980℃ / 2h / AC, and aging treatment at 700℃ / 4h / AC.

[0036] Step 3: The heat-treated blank is machined into test pieces; the machined tensile and fatigue performance test specimens are as follows: Figure 2 and Figure 3 As shown.

[0037] Step 4: Conduct a long-term heat exposure test on the test specimen; the long-term heat exposure test temperature is 300℃, and the test heat exposure time is 3000h. Figure 4 The figure shows the analysis of surface oxidation products of high-temperature titanium alloy after long-term heat exposure in this embodiment. As can be seen from the figure, the surface oxide layer of Ti150 alloy after heat exposure is mainly composed of rutile TiO2 and a small amount of Al2O3. SiO2 was not found in the XRD pattern. This may be due to the low content of SiO2, which results in weak or even indistinct diffraction peaks.

[0038] Step 5: Organize and evaluate the performance of the test pieces that have reached the specified test time; Figure 5 and Figure 6The figures show the surface oxidation of the high-temperature titanium alloy after 1000h and 3000h of long-term heat exposure, respectively, in this embodiment. As can be seen from the figures, after 1000h of heat exposure, a relatively thin, dense white oxide layer, approximately 2-3 μm thick, appears on the alloy surface. Near the oxide layer, an oxygen diffusion layer with a thickness of approximately 6-8 μm is formed in the alloy substrate. After 3000h of heat exposure, the oxide layer thickness on the alloy surface is approximately 4-5 μm, and the oxygen diffusion layer thickness is approximately 12-14 μm.

[0039] Figure 7 , Figure 8 and Figure 9 The images show the original microstructure of the high-temperature titanium alloy without long-term heat exposure, and the microstructure after 1000h and 3000h of long-term heat exposure, respectively. The original microstructure of the alloy without long-term heat exposure consists of β phase, lamellar α phase, and equiaxed α phase, with the equiaxed phase content being approximately 4.02% and the lamellar phase width being approximately 0.82μm. After 1000h of heat exposure, the equiaxed phase content is approximately 4.16%, and the lamellar phase width is approximately 0.87μm. After 3000h of heat exposure, the equiaxed phase content in the alloy microstructure is approximately 4.28%, and the lamellar phase width is approximately 0.93μm.

[0040] Figure 10 and Figure 12 The figures show the tensile properties and low-cycle fatigue properties of the high-temperature titanium alloy after different durations of heat exposure and without heat exposure, respectively, in this embodiment. It can be seen that, due to the relatively low heat exposure temperature, the tensile and fatigue properties of the alloy did not show a significant decrease. Specifically, in step 5, Figure 11 and Figure 13 The images show the fracture morphology of the high-temperature titanium alloy tensile and fatigue specimens after long-term heat exposure in this embodiment. Based on the above comprehensive performance evaluation, the additive manufacturing of Ti150 high-temperature titanium alloy does not affect its mechanical properties after long-term heat exposure at 300℃ for 3000h.

[0041] This embodiment provides a method for evaluating the microstructure and performance stability of Ti150 high-temperature titanium alloy formed by laser powder bed fusion additive manufacturing technology, based on the service conditions of Ti150 high-temperature titanium alloy. It accurately reflects the performance degradation law of additively manufactured high-temperature titanium alloy parts under long-term service conditions, and is particularly suitable for the initial material selection in the design stage of aerospace components and the microstructure and performance evaluation of additively manufactured parts.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure, characterized in that, Includes the following steps: Step 1: High-temperature titanium alloy blanks are formed using laser additive manufacturing; Step 2: Heat treatment is performed on the formed blank to adjust the non-equilibrium structure and residual stress in the deposited state. Step 3: The heat-treated blank is machined into a test piece; Step 4: Conduct long-term heat exposure tests on the test specimens to simulate their service behavior under actual working conditions; Step 5: Organize and evaluate the performance of the test pieces that have reached the specified test time.

2. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 1, characterized in that, In step 1, laser additive manufacturing is laser powder bed melting forming.

3. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 2, characterized in that, In step 1, the process window for laser additive manufacturing includes laser input power, laser scanning speed, scanning layer thickness, and laser scanning spacing. The laser input power ranges from 90 to 350W, the laser scanning speed ranges from 500 to 2000 mm / s, the scanning layer thickness ranges from 0.03 to 0.06 mm, and the laser scanning spacing ranges from 0.05 to 0.1 mm.

4. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 1, characterized in that, In step 2, the heat treatment methods are solution treatment and aging treatment. The solution treatment is carried out at 940~1020 ℃ / 2~4 h / AC, and the aging treatment is carried out at 650~780 ℃ / 2~8 h / AC.

5. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 1, characterized in that, In step 4, the test equipment for the long-term heat exposure test includes a heating furnace and a support container. The heating furnace is an air atmosphere furnace and is equipped with a temperature controller with a control accuracy of 0.

5. The temperature difference in the uniform temperature zone should not exceed ±5℃. The support container should not interact with the test specimen at the test temperature.

6. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 1, characterized in that, In step 4, the test temperature range of the long-term heat exposure test is a constant temperature of 300℃ to 650℃, and the test heat exposure duration ranges from 100 to 3000 hours.

7. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 1, characterized in that, In step 5, the evaluation of the structure and performance includes evaluation of the oxidation behavior of the test specimen surface, evaluation of microstructure changes, evaluation of tensile properties, and evaluation of fatigue performance.

8. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 7, characterized in that, The evaluation of surface oxidation behavior includes analysis of oxidation products, analysis of oxide layer thickness, and analysis of oxygen diffusion degree.

9. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 7, characterized in that, The evaluation of microstructure changes includes the analysis of changes in the proportion of phase composition.

10. The method for evaluating the stability of additively manufactured high-temperature titanium alloys under long-term thermal exposure according to claim 7, characterized in that, The tensile performance evaluation and the fatigue performance evaluation also include a comparison of the performance with that of unexposed specimens and the pattern of performance changes.

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