A cost-reduced thermomechanical fatigue specimen and method of making the same

Abstract

The application discloses a kind of cost-reducing thermal mechanical fatigue test pieces and preparation method thereof, belong to single crystal superalloy technical field.The thermal mechanical fatigue test piece of the application includes gauge length section, transition section, base material clamping section, weld and auxiliary material clamping section.The thermal mechanical fatigue test piece preparation includes conformal base material (including gauge length section, transition section and base material clamping section) preparation, auxiliary material preparation and base material and auxiliary material welding.Wherein, base material is expensive single crystal superalloy, and auxiliary material is low-cost single crystal superalloy, to replace most expensive base material with auxiliary material.In addition, in order to save expensive base material, base material is prepared by conformal design and conformal part directional solidification.The single crystal test rod is prepared by directional solidification of auxiliary material.The connection of base material and auxiliary material is completed by welding.The thermal mechanical fatigue test piece designed and prepared by the application significantly reduces cost, and the high-temperature strength of test is high, meets the requirements of thermal mechanical fatigue experiment.

Description

Technical Field

[0001] This invention relates to the field of single-crystal superalloy technology, and more specifically to a cost-reducing thermomechanical fatigue specimen and its preparation method. Background Technology

[0002] Single-crystal superalloys are primarily used in high-pressure and low-pressure turbine blades for aero-engines, which are the main hot-end components of these engines. During routine aircraft operation, the repeated start-ups and shutdowns of aero-engines subject single-crystal superalloy blades to cyclical temperature and stress changes. To ensure the safe service of these blades, it is essential to thoroughly study their service behavior under conditions of dual temperature and stress cyclic changes. Thermomechanical fatigue testing is an effective method for studying this complex and demanding operating condition. Therefore, it is crucial to strengthen research on the thermomechanical fatigue of single-crystal superalloys.

[0003] Small-sized thermomechanical fatigue specimens are insufficient to accurately simulate blade service behavior, and some single crystals also exhibit thin-wall effects. Therefore, thermomechanical fatigue specimens are generally large. Thermomechanical fatigue testing requires strict control of both heating and cooling rates. Therefore, air-cooling or water-cooling devices are typically incorporated into the thermomechanical fatigue equipment, while ensuring the specimen has a sufficiently long clamping section to achieve adequate cooling rates. Due to the long clamping section, along with the long gauge length and transition section, the thermomechanical fatigue specimens are quite long, typically 144–160 mm. Because preparing excessively long single crystal specimens is difficult, and the single crystallinity of specimens far from the water-cooled end is poor, the length of the prepared single crystal specimens is generally about 200–220 mm. Therefore, only one thermomechanical fatigue specimen can be obtained from one single crystal specimen.

[0004] High-generation single-crystal superalloys exhibit high temperature resistance. With the increasing inlet temperature of aero-engine turbines, the development of high-generation single-crystal superalloys is an inevitable future trend. Due to the inclusion of rare and precious elements such as Re and Ru, the cost of high-generation single-crystal superalloys is extremely high. In recent years, with the soaring price of Ru, the price of fourth-generation single-crystal superalloys has reached 7 million yuan per ton. A single crystal test bar weighs approximately 0.6 kg, and the material cost for a thermomechanical fatigue test specimen is approximately 4200 yuan. There are also costs for smelting the master alloy, preparing the single crystal (20,000 yuan per furnace, 6 single crystal test bars per furnace, approximately 33,000 yuan per bar), and testing fees (orientation and composition testing, approximately 300 yuan per bar). Moreover, fourth-generation single crystals have a high content of refractory elements, resulting in a lower pass rate (approximately 50%). Therefore, the cost of a single thermomechanical fatigue test specimen reaches 15,000 yuan. Due to the volatility of thermomechanical fatigue data and the requirement for reliable and stable material service, a large number of thermomechanical fatigue test specimens are needed. Therefore, it is urgent to improve the sample design and preparation methods to save expensive high-generation single-crystal alloy materials and significantly reduce costs. Summary of the Invention

[0005] To address the problems of large size and high cost of high-generation single-crystal superalloy thermomechanical fatigue specimens, the present invention aims to provide a thermomechanical fatigue specimen and its preparation method that significantly reduce costs, thereby significantly reducing the cost of high-generation single-crystal superalloy thermomechanical fatigue research.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A thermomechanical fatigue specimen with significantly reduced costs includes a gauge length section, a transition section, and a clamping section. The clamping section is formed by brazing a base material clamping section and an auxiliary material clamping section together. The gauge length section is connected to the transition section at both ends, and the outer side of the transition section is connected to the base material clamping section. The base material clamping section and the auxiliary material clamping section are connected by a weld.

[0008] The gauge length section, transition section, and base material clamping end are made of expensive high-generation single-crystal high-temperature alloy base material, with a base alloy price as high as 7 million yuan / ton. Furthermore, the gauge length section, transition section, and base material clamping end are an integral structure, entirely prepared by directional solidification of the expensive high-generation single-crystal high-temperature alloy base material. Its design is conformal to reduce costs. The conformal base material retains a surface allowance of 0.3–1 mm.

[0009] The total length of the clamping section is 50-80% of the total length of the thermomechanical fatigue specimen (144-160 mm); the length of the base material clamping section is 1-30 mm and the diameter is 8-20 mm.

[0010] The dimensions of the gauge length and clamping section are those of conventional thermomechanical fatigue specimen gauge length and clamping section.

[0011] The auxiliary material clamping section is prepared by directional solidification of a low-cost single-crystal high-temperature alloy. The price of its master alloy is about 500,000 to 600,000 yuan per ton, which is less than 10% of that of expensive single-crystal high-temperature alloys. Moreover, its single-crystal preparation has a high qualification rate, which further reduces costs.

[0012] The base material clamping section and the auxiliary material clamping section are connected by brazing to form a weld. The brazing filler metal is inexpensive and the welding process is simple. After the filler metal is applied, brazing can be completed simply by heat treatment. Moreover, one heat treatment cycle can process dozens or even hundreds of brazed samples, thus reducing brazing costs.

[0013] The specific operation steps of this invention are as follows:

[0014] (A) Thermomechanical fatigue specimen structure design includes the following steps (A1)-(A5):

[0015] (A1) Design the size and structure of the thermomechanical fatigue specimen, including the gauge length section, transition section, base material clamping section, weld and auxiliary material clamping section.

[0016] (A2) The gauge length section, transition section, and base material clamping end are integrally formed structures (prepared as a whole), called conformal base material. The conformal base material is an expensive high-generation single-crystal high-temperature alloy, designed to conform to the shape of the thermomechanical fatigue specimen. The length of the base material clamping section is 1–30 mm, and the diameter is 8–20 mm. A margin of 0.3–1 mm is retained on the surface of the conformal base material.

[0017] (A3) The auxiliary material clamping section adopts a low-cost single-crystal high-temperature alloy.

[0018] (A4) The base material clamping section and the auxiliary material clamping section are connected by brazing to form a weld.

[0019] (A5) The thermomechanical fatigue specimen dimensions designed in this invention are consistent with those of conventional thermomechanical fatigue specimens (total length 144-160 mm).

[0020] (B) Preparation of conformal parent material, including the following steps (B1)-(B3):

[0021] (B1) Prepare wax molds and mold shells according to the dimensions of the conformal base material (end face diameter is 16mm).

[0022] (B2) Cut about 4 kg of high-generation expensive single-crystal high-temperature alloy master alloy that meets the composition requirements, and prepare conformal master single-crystal high-temperature alloy in a directional solidification furnace. During the preparation process, defects at the abrupt change in cross section should be avoided.

[0023] (B3) The directional solidification process parameters are as follows: the temperature of the upper zone of the directional solidification furnace is 1450~1600℃, the temperature of the lower zone is 1480~1600℃, the pouring temperature is 1450~1600℃, and the pulling speed is 2~6mm / min.

[0024] (C) Preparation of low-cost single-crystal superalloys, comprising the following steps (C1)-(C3):

[0025] (C1) Prepare a single crystal test rod wax mold and mold shell with a diameter of 16 mm.

[0026] (C2) Cut about 4 kg of low-cost single-crystal high-temperature alloy master alloy that meets the composition requirements and prepare single-crystal high-temperature alloy in a directional solidification furnace.

[0027] (C3) The directional solidification process parameters are as follows: the temperature of the upper zone of the directional solidification furnace is 1450~1550℃, the temperature of the lower zone is 1460~1550℃, the pouring temperature is 1460~1550℃, and the pulling speed is 2~6mm / min.

[0028] (D) Welding, including the following steps (D1)-(D7):

[0029] (D1) The conformal base material and the low-cost single crystal high-temperature alloy test bar were subjected to solution treatment using their respective heat treatment regimes.

[0030] (D2) Polish the end face of the conformal base material.

[0031] (D3) Cut a low-cost single-crystal high-temperature alloy (auxiliary material) of appropriate length according to the thermomechanical fatigue specimen size, and polish one end face.

[0032] (D4) The welding process for the base material and auxiliary material is brazing.

[0033] (D5) Mix the brazing filler metal such as BCo45NiCrWB with the water-based adhesive in a ratio of 2:1 to 1:3, stir evenly, and then apply it to the polished end face of the base material and the auxiliary material. Add an appropriate amount of flow inhibitor to prevent molten droplets from overflowing and to bond the base material and the auxiliary material.

[0034] (D6) Place the above-mentioned base material and auxiliary material in a vacuum heat treatment furnace, raise the temperature to 1150℃~1250℃ at a heating rate of 3~20℃ / min, hold for 0.2~8h, and then cool in the furnace.

[0035] (D7) After brazing, perform aging heat treatment according to the aging heat treatment process of the base material to improve high-temperature strength.

[0036] (E) Performance testing, including the following steps (E1)-(E3):

[0037] (E1) Since the thermomechanical fatigue process may be subjected to high-temperature tensile and compressive loads, the test bar prepared above is processed into tensile and compressive specimens.

[0038] (E2) The tensile and compression specimens are processed with the weld located in the middle of the working section.

[0039] (E3) Test the high-temperature tensile and high-temperature compressive properties of the specimen (since thermomechanical fatigue tests are generally conducted at 400℃~900℃, a typical temperature was selected for high-temperature performance testing) to ensure that it can withstand the thermomechanical fatigue test load.

[0040] (F) Preparation of thermomechanical fatigue specimens:

[0041] Thermomechanical fatigue specimens were prepared by machining the test bar containing the conformal base material and its welded low-cost single-crystal high-temperature alloy, which was prepared according to the above steps.

[0042] The advantages and beneficial effects of this invention are as follows:

[0043] Conventional thermomechanical fatigue specimens of single-crystal superalloys are processed using single crystals with a diameter of 16 mm, resulting in significant material waste. This invention utilizes conformal base materials for single-crystal preparation in the gauge length and transition sections. Furthermore, due to the shorter conformal base material (approximately 35–40 mm), 5–6 conformal base materials can be prepared for each single crystal growth length, and 30–36 conformal base materials can be prepared in one batch of single crystals. This significantly reduces the consumption of expensive single-crystal superalloys, lowers smelting costs, and consequently reduces overall costs.

[0044] This invention employs brazing to attach a low-cost single-crystal superalloy to both sides of the expensive, high-generation single-crystal superalloy in the preparation of thermomechanical fatigue specimens. This largely replaces the clamping sections of the thermomechanical fatigue specimen. This method significantly reduces the consumption of expensive single-crystal superalloy, further lowering costs.

[0045] Heat treatment after brazing can release the stress in the weld and improve its high-temperature strength.

[0046] The high-generation single-crystal superalloy thermomechanical fatigue specimens prepared using this method require only about 15-30% of the material to be made from expensive high-generation single-crystal superalloys, thus reducing the amount of expensive high-generation single-crystal superalloys used and significantly lowering the cost of high-generation single-crystal superalloy thermomechanical fatigue specimens. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the design structure of the present invention.

[0048] Figure 2 This is to prepare an expensive high-generation single-crystal superalloy with a diameter of 16 mm.

[0049] Figure 3 This is to prepare an expensive high-generation single-crystal conformal matrix with an end face diameter of 16 mm.

[0050] Figure 4 To prepare a low-cost single-crystal high-temperature alloy with a diameter of 16 mm.

[0051] Figure 5 These are test bars used for performance testing after brazing.

[0052] Figure 6 This is a high-temperature tensile specimen processed after brazing.

[0053] Figure 7 This is a high-temperature compression test specimen processed after brazing.

[0054] Figure 8 The tensile properties were tested at 400℃.

[0055] Figure 9The compression performance was tested at 900℃.

[0056] Figure 10 The specimen is a thermomechanical fatigue test sample after processing. Detailed Implementation

[0057] To further understand the present invention, the present invention is described below in conjunction with embodiments, comparative examples and accompanying drawings. However, the embodiments are only for further elaboration of the features and advantages of the present invention, and are not intended to limit the claims of the present invention. The technical solutions of the present invention are not limited to the specific embodiments listed below.

[0058] Based on research on thermomechanical fatigue specimens, it has been found that the gauge length of existing thermomechanical fatigue specimens is only 22 mm, while the clamping end length reaches 110 mm. A large portion of the single-crystal specimen serves as the clamping end. Therefore, the thermomechanical fatigue specimen of this invention is designed with the following structure: gauge length 1, transition section 2, base material clamping section 3, weld 4, and auxiliary material clamping section 5, as follows... Figure 1 As shown. The total length of the auxiliary material clamping section 5 is approximately 50-80% of the total length of the thermomechanical fatigue specimen. The gauge length section 1, transition section 2, and base material clamping section 3 are made of expensive, high-generation single-crystal high-temperature alloy base materials, with a base alloy price as high as 7 million yuan / ton. They are prepared by integral directional solidification and are designed with conformal design to reduce costs.

[0059] The material of the auxiliary clamping section 5 is a low-cost single-crystal superalloy, prepared by directional solidification. Its master alloy price is approximately 500,000 to 600,000 yuan per ton, less than 10% of the price of expensive, high-generation single-crystal superalloys. Moreover, its single-crystal preparation yield is high, further reducing costs.

[0060] The base material clamping section 5 and the auxiliary material clamping section 3 are connected by brazing to form a weld 4. The brazing filler metal is inexpensive, and the welding process is simple. After the filler metal is applied, brazing is completed only through heat treatment. Moreover, one heat treatment cycle can process dozens or even hundreds of brazed samples, thus reducing brazing costs.

[0061] Comparative Example 1:

[0062] (1) A fourth-generation single-crystal high-temperature alloy test rod with a diameter of 16 mm was prepared by directional solidification, such as... Figure 2 As shown.

[0063] (2) The fourth-generation single-crystal high-temperature alloy test bar prepared in step (1) is subjected to solution treatment, first-stage aging and second-stage aging heat treatment using conventional processes.

[0064] (3) The fourth-generation single-crystal high-temperature alloy test bar that has undergone solution treatment, first-level aging and second-level aging heat treatment in step (2) is subjected to mechanical processing of a 160mm long thermomechanical fatigue specimen to obtain a high-generation single-crystal high-temperature alloy thermomechanical fatigue specimen.

[0065] The thermomechanical fatigue specimens prepared in this example, all made from expensive fourth-generation single-crystal superalloys, cost 7 million yuan per ton. A single crystal specimen weighs approximately 0.6 kg, and the material cost for one thermomechanical fatigue specimen is about 4200 yuan. There are also costs for the master alloy smelting, single crystal preparation (20,000 yuan per furnace, 6 single crystal specimens per furnace, approximately 2500-3000 yuan per specimen), and testing fees (orientation and composition testing, approximately 300 yuan per specimen). Furthermore, fourth-generation single crystals have a high content of refractory elements, resulting in a lower yield (approximately 50%). Therefore, the cost of one thermomechanical fatigue specimen reaches 15,000 yuan. The preparation cost of thermomechanical fatigue specimens is high.

[0066] Example 1:

[0067] 1. Thermomechanical fatigue specimen design

[0068] (1) Based on the dimensions of the thermomechanical fatigue specimen, the thermomechanical fatigue specimen is designed as follows: Figure 1 The structure shown includes gauge length section 1, transition section 2, base material clamping end 3, weld 4, and auxiliary material clamping section 5.

[0069] (2) The gauge length section 1, transition section 2, and base material clamping end 3 are integrated into a single unit, named conformal base material. The conformal base material is an expensive high-generation single-crystal high-temperature alloy, designed to conform to the shape of the thermomechanical fatigue specimen. In this embodiment, the length of the base material clamping section is 5 mm, and the end face diameter is 16 mm. A 0.6 mm allowance is retained on the surface of the conformal base material.

[0070] (3) The auxiliary material clamping section adopts a low-cost single crystal high-temperature alloy.

[0071] (4) The base material clamping section 5 and the auxiliary material clamping section 3 are connected by brazing to form a weld 4.

[0072] (5) The thermomechanical fatigue specimen size designed above is consistent with the general thermomechanical fatigue size.

[0073] 2. Preparation of conformal parent material

[0074] (1) Based on the dimensions of the conformal parent material, prepare 6 conformal wax molds along the length of the test bar, and prepare mold shells. 1 mold shell is used to prepare 36 conformal parent materials.

[0075] (2) Approximately 4 kg of high-generation, expensive fourth-generation single-crystal superalloy master alloy meeting the composition requirements was cut and used to prepare conformal master single-crystal superalloys in a directional solidification furnace, such as... Figure 3 As shown.

[0076] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1500℃, the temperature of the lower zone is 1520℃, the pouring temperature is 1520℃, and the pulling speed is 3mm / min.

[0077] 3. Preparation of low-cost single-crystal superalloys

[0078] (1) Prepare a wax mold and mold shell of DD413 single crystal test rod with a diameter of 16mm.

[0079] (2) Cut approximately 4 kg of DD413 master alloy that meets the composition requirements and prepare single-crystal high-temperature alloy in a directional solidification furnace, such as... Figure 4 As shown.

[0080] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1480℃, the temperature of the lower zone is 1500℃, the pouring temperature is 1500℃, and the pulling speed is 3mm / min.

[0081] 4. Welding

[0082] (1) The conformal base material and the low-cost single crystal high temperature alloy test bar were subjected to solid solution treatment according to their respective heat treatment regimes using the fourth-generation single crystal high temperature alloy and the low-cost single crystal high temperature alloy.

[0083] (2) Polish the end face of the conformal base material.

[0084] (3) Cut a low-cost DD413 single crystal high-temperature alloy (auxiliary material) of appropriate length according to the thermomechanical fatigue specimen size, and polish one end face.

[0085] (4) The connection between the base material and the auxiliary material is made by brazing.

[0086] (5) Mix BCo45NiCrWB solder and water-based adhesive in a weight ratio of 1:1, stir evenly, and then coat it onto the polished end faces of the base material and auxiliary material. Add appropriate flow inhibitors and bond the base material and auxiliary material together.

[0087] (6) Place the above-mentioned base material and auxiliary material in a vacuum heat treatment furnace, raise the temperature to 1220°C at a heating rate of 10°C / min, hold for 1 hour, and then cool the furnace.

[0088] (7) The test bar after brazing is as follows Figure 5 As shown, aging heat treatment is carried out according to the aging heat treatment process of the base material to improve high-temperature strength.

[0089] 5. Performance Testing

[0090] (1) The test bar prepared above is processed into tensile and compression specimens, such as... Figure 6 and Figure 7 As shown.

[0091] (2) The tensile and compression test specimens were processed, and weld 4 was located in the middle of the working section.

[0092] (3) The high-temperature tensile and compressive properties of the tested welded specimens are as follows: Figure 8 and Figure 9 As indicated by "1", the tensile strength reaches 700 MPa at 400℃. Since the welded part is located in the clamping section, and the cross-sectional area of ​​the clamping section is four times that of the gauge length section, this strength meets the requirements of the thermomechanical fatigue test. Similarly, the compressive strength reaches 880 MPa at 900℃, which also meets the requirements of the thermomechanical fatigue test.

[0093] 6. Preparation of thermomechanical fatigue specimens

[0094] The test bars prepared according to the above process are machined into thermomechanical fatigue specimens and subjected to thermomechanical fatigue tests, such as... Figure 10 As shown.

[0095] The thermomechanical fatigue specimens prepared using Example 1 consume less than 20% of the expensive single-crystal superalloy used in the original thermomechanical fatigue specimens. In addition, directional solidification can prepare multiple conformal base materials, which is more efficient and reduces smelting costs. The cost of the conformal base material is about 1,500 yuan, and the cost of DD413 single crystal and welding used in each thermomechanical fatigue specimen is about 1,000 yuan. The total cost of each thermomechanical fatigue specimen is about 2,500 yuan, which greatly reduces costs compared to the approximately 15,000 yuan cost of the expensive fourth-generation single-crystal thermomechanical fatigue specimens.

[0096] Example 2:

[0097] 1. Thermomechanical fatigue specimen design

[0098] (1) Based on the size of the thermomechanical fatigue specimen, the thermomechanical fatigue specimen is designed with the following structure: gauge length section 1, transition section 2, base material clamping end 3, weld 4, auxiliary material clamping section 5.

[0099] (2) The gauge length section 1, transition section 2, and base material clamping end 3 are a single unit, named conformal base material. The conformal base material is an expensive high-generation single-crystal high-temperature alloy, and its conformal design is based on the shape of the thermomechanical fatigue specimen. In this embodiment, the length of the base material clamping section is 3 mm, and the end face diameter is 16 mm. A 0.8 mm allowance is retained on the surface of the conformal base material.

[0100] (3) The auxiliary material clamping section adopts a low-cost single crystal high-temperature alloy.

[0101] (4) The base material clamping section 5 and the auxiliary material clamping section 3 are connected by brazing to form a weld 4.

[0102] (5) The thermomechanical fatigue specimen size designed above is consistent with the general thermomechanical fatigue size.

[0103] 2. Preparation of conformal parent material

[0104] (1) Based on the dimensions of the conformal parent material, prepare 6 conformal wax molds along the length of the test bar, and prepare mold shells. 1 mold shell is used to prepare 36 conformal parent materials.

[0105] (2) Approximately 4 kg of high-generation, expensive fourth-generation single-crystal superalloy master alloy meeting the composition requirements was cut and used to prepare conformal master single-crystal superalloys in a directional solidification furnace, such as... Figure 3 As shown.

[0106] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1520℃, the temperature of the lower zone is 1530℃, the pouring temperature is 1530℃, and the pulling speed is 3mm / min.

[0107] 3. Preparation of low-cost single-crystal superalloys

[0108] (1) Prepare a wax mold and mold shell of DD413 single crystal test rod with a diameter of 16mm.

[0109] (2) Cut approximately 4 kg of DD413 master alloy that meets the composition requirements and prepare single-crystal high-temperature alloy in a directional solidification furnace, such as... Figure 4 As shown.

[0110] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1500℃, the temperature of the lower zone is 1520℃, the pouring temperature is 1520℃, and the pulling speed is 3mm / min.

[0111] 4. Welding

[0112] (1) The conformal base material and the low-cost single crystal high temperature alloy test bar were subjected to solution treatment using the respective heat treatment regimes of the fourth-generation single crystal high temperature alloy and the low-cost DD413 single crystal high temperature alloy.

[0113] (2) Polish the end face of the conformal base material.

[0114] (3) Cut a low-cost DD413 single crystal high-temperature alloy (auxiliary material) of appropriate length according to the thermomechanical fatigue specimen size, and polish one end face.

[0115] (4) Brazing the base material and auxiliary material.

[0116] (5) Mix the brazing filler metal such as BCo45NiCrWB with the water-based adhesive in a ratio of 1:1.2, stir evenly, and then coat it onto the polished end face of the base material and the auxiliary material. Add an appropriate amount of flow barrier and bond the base material and the auxiliary material together.

[0117] (6) Place the above-mentioned base material and auxiliary material in a vacuum heat treatment furnace, raise the temperature to 1200°C at a heating rate of 8°C / min, hold for 20 min, and then cool the furnace.

[0118] (7) The test bar after brazing is as follows Figure 5 As shown, aging heat treatment is carried out according to the aging heat treatment process of the base material to improve high-temperature strength.

[0119] 5. Performance Testing

[0120] (1) The test bar prepared above is processed into tensile and compression specimens, such as... Figure 6 and Figure 7 As shown.

[0121] (2) The tensile and compression test specimens were processed, and weld 4 was located in the middle of the working section.

[0122] (3) The high-temperature tensile and compressive properties of the tested welded specimens are as follows: Figure 8 and Figure 9 As shown in "2", the tensile strength at 400℃ reaches 820MPa. Since the welded part is located in the clamping section, and the cross-sectional area of ​​the clamping section is four times that of the gauge length section, this strength meets the requirements of the thermomechanical fatigue test. Similarly, the compressive strength at 900℃ reaches 905MPa, which also meets the requirements of the thermomechanical fatigue test.

[0123] 6. Preparation of thermomechanical fatigue specimens

[0124] The test bars prepared according to the above process are machined into thermomechanical fatigue specimens and subjected to thermomechanical fatigue tests, such as... Figure 10 As shown.

[0125] The thermomechanical fatigue specimens prepared using Example 2 consume less than 20% of the expensive single-crystal superalloy used in the original thermomechanical fatigue specimens. In addition, directional solidification can prepare multiple conformal base materials, which is more efficient and reduces smelting costs. The cost of the conformal base material is about 1,500 yuan, and the cost of DD413 single crystal and welding used in each thermomechanical fatigue specimen is about 1,000 yuan. The total cost of each thermomechanical fatigue specimen is about 2,500 yuan, which greatly reduces costs compared to the approximately 15,000 yuan cost of the expensive fourth-generation single-crystal thermomechanical fatigue specimens.

[0126] Example 3:

[0127] 1. Thermomechanical fatigue specimen design

[0128] (1) Based on the size of the thermomechanical fatigue specimen, the thermomechanical fatigue specimen is designed with the following structure: gauge length section 1, transition section 2, base material clamping end 3, weld 4, auxiliary material clamping section 5.

[0129] (2) The gauge length section 1, transition section 2, and base material clamping end 3 are a single unit, named conformal base material. The base material is an expensive high-generation single-crystal high-temperature alloy, and is designed to conform to the shape of the thermomechanical fatigue specimen. In this embodiment, the length of the base material clamping section is 6 mm, and the end face diameter is 16 mm. A 0.9 mm allowance is retained on the surface of the conformal base material.

[0130] (3) The auxiliary material clamping section adopts a low-cost single crystal high-temperature alloy.

[0131] (4) The base material clamping section 5 and the auxiliary material clamping section 3 are connected by brazing to form a weld 4.

[0132] (5) The thermomechanical fatigue specimen size designed above is consistent with the general thermomechanical fatigue size.

[0133] 2. Preparation of conformal parent material

[0134] (1) Based on the dimensions of the conformal parent material, prepare 5 conformal wax molds along the length of the test bar, and prepare mold shells. Prepare 30 conformal parent materials with 1 mold shell.

[0135] (2) Approximately 4 kg of expensive, high-generation fourth-generation single-crystal high-temperature alloy master alloy meeting the composition requirements was cut and used to prepare conformal master single-crystal high-temperature alloy in a directional solidification furnace, such as... Figure 3 As shown.

[0136] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1520℃, the temperature of the lower zone is 1540℃, the pouring temperature is 1540℃, and the pulling speed is 3mm / min.

[0137] 3. Preparation of low-cost single-crystal superalloys

[0138] (1) Prepare a wax mold and mold shell of DD413 single crystal test rod with a diameter of 16mm.

[0139] (2) Cut approximately 4 kg of DD413 master alloy that meets the composition requirements and prepare single-crystal high-temperature alloy in a directional solidification furnace, such as... Figure 4 As shown.

[0140] (3) The process parameters for directional solidification are as follows: the temperature of the upper zone of the directional solidification furnace is 1500℃, the temperature of the lower zone is 1520℃, the pouring temperature is 1520℃, and the pulling speed is 3mm / min.

[0141] 4. Welding

[0142] (1) The conformal base material and the low-cost single crystal high temperature alloy test bar were subjected to solution treatment using the respective heat treatment regimes of the fourth-generation single crystal high temperature alloy and the low-cost DD413 single crystal high temperature alloy.

[0143] (2) Polish the end face of the conformal base material.

[0144] (3) Cut a low-cost DD413 single crystal high-temperature alloy (auxiliary material) of appropriate length according to the thermomechanical fatigue specimen size, and polish one end face.

[0145] (4) Brazing the base material and auxiliary material.

[0146] (5) Mix the brazing filler metal such as BCo45NiCrWB with the water-based adhesive at a ratio of 1:0.8, stir evenly, and then coat it onto the polished end face of the base material and the auxiliary material. Add an appropriate amount of flow barrier and bond the base material and the auxiliary material together.

[0147] (6) Place the above-mentioned base material and auxiliary material in a vacuum heat treatment furnace, raise the temperature to 1230°C at a heating rate of 10°C / min, hold for 30 min, and then cool the furnace.

[0148] (7) The test bar after brazing is as follows Figure 5 As shown, aging heat treatment is carried out according to the aging heat treatment process of the base material to improve high-temperature strength.

[0149] 5. Performance Testing

[0150] (1) The test bar prepared above is processed into tensile and compression specimens, such as... Figure 6 and Figure 7 As shown.

[0151] (2) The tensile and compression test specimens were processed, and weld 4 was located in the middle of the working section.

[0152] (3) The high-temperature tensile and compressive properties of the tested welded specimens are as follows: Figure 8 and Figure 9 As shown by "3", the tensile strength at 400℃ reaches 760MPa. Since the welded part is located in the clamping section, and the cross-sectional area of ​​the clamping section is four times that of the gauge length section, this strength meets the requirements of the thermomechanical fatigue test. Similarly, the compressive strength at 900℃ reaches 900MPa, which also meets the requirements of the thermomechanical fatigue test.

[0153] 6. Preparation of thermomechanical fatigue specimens

[0154] The test bars prepared according to the above process are machined into thermomechanical fatigue specimens and subjected to thermomechanical fatigue tests, such as... Figure 10 As shown.

[0155] The thermomechanical fatigue specimens prepared using Example 3 consume less than 21% of the expensive single-crystal superalloy used in each specimen compared to the original thermomechanical fatigue specimens. Furthermore, directional solidification allows for the preparation of multiple conformal base materials, resulting in higher efficiency and reduced smelting costs. The cost of the conformal base material is approximately RMB 1,800, and the cost of the DD413 single crystal and welding used in each thermomechanical fatigue specimen is approximately RMB 1,000. The total cost of each thermomechanical fatigue specimen is approximately RMB 2,800, which significantly reduces costs compared to the approximately RMB 15,000 cost of the expensive fourth-generation single-crystal thermomechanical fatigue specimens.

[0156] The specific embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the scope and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cost-reducing thermomechanical fatigue specimen, characterized in that: The thermomechanical fatigue specimen includes a gauge length section (1), a transition section (2), and a clamping section. The clamping section is formed by brazing a base material clamping section (3) and an auxiliary material clamping section (5). The gauge length section (1), the transition section (2), and the base material clamping section (3) are an integral structure. This integral structure is made of expensive high-generation single-crystal high-temperature alloy. The auxiliary material clamping section (5) is made of low-cost single-crystal high-temperature alloy. The gauge length section (1) is connected to the transition section (2) at both ends. The outer side of the transition section (2) is connected to the base material clamping section (3). There is a weld (4) between the base material clamping section (3) and the auxiliary material clamping section (5).

2. The cost-reduced thermomechanical fatigue specimen according to claim 1, characterized in that: The integrated structure is prepared by directional solidification and adopts conformal base material design to reduce costs; the auxiliary material clamping section (5) is prepared by directional solidification and its base alloy price is much lower than that of expensive high-generation single crystal high-temperature alloys.

3. The cost-reduced thermomechanical fatigue specimen according to claim 2, characterized in that: The total length of the clamping section is 50-80% of the total length of the thermomechanical fatigue specimen; the total length of the thermomechanical fatigue specimen is 144-160 mm; the length of the parent material clamping section (3) is 1-30 mm and the diameter is 8-20 mm.

4. The cost-reduced thermomechanical fatigue specimen according to claim 2, characterized in that: The dimensions of the gauge length and clamping section are those of conventional thermomechanical fatigue specimen gauge length and clamping section.

5. The cost-reduced thermomechanical fatigue specimen according to claim 2, characterized in that: The designed conformal base material retains a surface allowance of 0.3~1mm.

6. The method for preparing cost-reduced thermomechanical fatigue specimens according to any one of claims 1-5, characterized in that: The method includes the preparation of expensive conformal base material, the preparation of auxiliary material clamping section, and the welding of conformal base material and auxiliary material clamping section.

7. The method for preparing a cost-reducing thermomechanical fatigue specimen according to claim 6, characterized in that: The conformal base material is prepared by directional solidification. During the directional solidification process of the conformal base material, the temperature of the upper zone of the directional solidification furnace is 1450~1600℃, the temperature of the lower zone is 1480~1600℃, the casting temperature is 1450~1600℃, and the drawing speed is 2~6mm / min.

8. The method for preparing a cost-reducing thermomechanical fatigue specimen according to claim 6, characterized in that: The auxiliary material clamping section is made of low-cost single-crystal high-temperature alloy, and the auxiliary material clamping section is prepared by directional solidification. During the directional solidification preparation of the auxiliary material clamping section, the temperature of the upper zone of the directional solidification furnace is 1450~1550℃, the temperature of the lower zone is 1460~1550℃, the casting temperature is 1460~1550℃, and the pulling speed is 2~6mm / min.

9. The method for preparing a cost-reducing thermomechanical fatigue specimen according to claim 6, characterized in that: The welding of the conformal base material and the auxiliary material clamping section adopts a brazing process. The brazing process is as follows: the brazing filler metal and water-based adhesive are mixed and stirred evenly in a weight ratio of 2:1 to 1:3, and then coated between the polished end faces of the base material and the auxiliary material. An appropriate amount of flow-blocking agent may be added. Then, the base material and the auxiliary material are placed in a vacuum heat treatment furnace and heated to 1150℃ to 1250℃ at a heating rate of 3 to 20℃ / min, and held for 0.2 to 8 hours, and then cooled in the furnace. This brazing process combines the base material and the auxiliary material into one piece.

10. The method for preparing a cost-reducing thermomechanical fatigue specimen according to claim 9, characterized in that: Before brazing, the base material and auxiliary material are solution treated according to the heat treatment process of the base material and auxiliary material respectively; the main component of the brazing filler metal used in the brazing process should be the components contained in the base material and auxiliary material; after brazing, the base material is subjected to aging heat treatment according to the aging heat treatment process to improve high temperature strength.

Images