An apparatus and process for heat treating nickel-based single crystal superalloys

Abstract

The application discloses a kind of nickel-based single crystal superalloy heat treatment equipment and process.The equipment of the present application includes vacuum system, heating system, cooling system and pulling system, vacuum system is set with furnace cover furnace body, air valve and air valve, heating system is set with heat preservation layer, heater, thermocouple and heat insulation baffle, cooling system is set with crystallizer and stirrer, pulling system is set with object table and lifting rod.The process of the present application includes preparing sample, loading sample into heat treatment equipment, heating sample once, pulling sample to cooling system, heating sample twice, pulling sample to cooling system twice, heating sample three times, pulling sample to cooling system three times and the like.The present application can meet the overall process requirements of nickel-based single crystal superalloy heat treatment process, can accurately control the cooling rate of superalloy, has strong operability, high efficiency, not only can meet the high standard demand of industrial production, but also is very suitable for laboratory research use.

Description

Technical Field

[0001] This invention relates to the heat treatment of single-crystal superalloys, and more specifically to an equipment and process for heat treatment of nickel-based single-crystal superalloys. Background Technology

[0002] Nickel-based single-crystal superalloys are widely used in single-crystal blade materials for aero-engines and ground-based gas turbines due to their excellent high-temperature resistance, good creep resistance, hot corrosion resistance, high oxidation resistance, and microstructural stability. The microstructure of nickel-based superalloys mainly consists of a γ-phase matrix and γ' precipitates. By employing appropriate heat treatment processes (heating, holding, and cooling), the dendrite spacing and the size and morphology of the γ / γ' phases can be controlled, thereby enabling the alloy to exhibit optimal comprehensive high-temperature performance.

[0003] Currently, the cooling processes used in the heat treatment of nickel-based single-crystal superalloys mainly employ several methods, including furnace cooling, air cooling, and cooling medium cooling. While furnace cooling, air cooling, and general cooling medium cooling can alter the cooling rate during heat treatment, they cannot precisely control the alloy's cooling rate. Air quenching, as a type of cooling medium cooling, allows adjustment of the cooling rate of the superalloy through methods such as air pressure and speed; however, precise control of the cooling rate remains challenging, and this method involves complex and costly equipment, limiting its application in industrial settings and making it unsuitable for laboratory research. Summary of the Invention

[0004] To address the technical problems of low precision in cooling rate control, complex equipment, and high cost in existing heat treatment processes for nickel-based single-crystal superalloys, this invention provides an equipment and process for heat treatment of nickel-based single-crystal superalloys.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] An apparatus for heat treatment of nickel-based single-crystal superalloys includes a vacuum system, a heating system, a cooling system, and a pulling system; the vacuum system is equipped with a furnace body with a furnace cover, an exhaust valve, and a venting valve; the heating system is equipped with an insulation layer, a heater, a thermocouple, and a heat insulation baffle; the cooling system is equipped with a crystallizer and a stirrer; and the pulling system is equipped with a platform and a lifting rod.

[0007] Furthermore, a furnace cover is installed on the top of the furnace body, and an exhaust valve and a vent valve are installed on the side of the furnace body; the bottom of the heating system is vertically connected to the top of the cooling system via a heat insulation baffle.

[0008] Furthermore, the heat insulation baffle is preferably made of plate-shaped porous alumina ceramic material, and the thickness can be changed according to the actual situation to obtain the best heat insulation effect.

[0009] Furthermore, the heating system is placed inside the furnace body, the heater is located inside the insulation layer, the thermocouple is located below the heater, one side of the thermocouple is vertically connected to the inner wall of the insulation layer, and the bottom of the insulation layer is connected to the heat insulation baffle.

[0010] Furthermore, the heater is made of graphite, and the insulation layer is made of multiple layers of carbon felt.

[0011] Furthermore, the cooling system is placed inside the furnace body, the bottom of the crystallizer is connected to the inner bottom of the furnace body, and the stirrer is located on one side of the outer wall of the insulation layer and extends into the crystallizer through the heat insulation baffle.

[0012] Furthermore, a Ga-In-Sn solution coolant is placed inside the crystallizer. The height of the Ga-In-Sn solution coolant is 5-15 mm above the top of the crystallizer, the solution temperature is 10-25℃, and the hydraulic pressure is 0.1-2 MPa. The Ga-In-Sn solution coolant plays a crucial role in the control of the cooling rate and has the advantage of precise control compared with conventional coolants.

[0013] Furthermore, the lifting rod of the pull-out system passes longitudinally through the bottom of the furnace body, through the bottom and top of the crystallizer of the cooling system, and through the central hole of the heat insulation baffle, into the heating system, and can reciprocate between the heating system and the cooling system, with the platform placed on top of the lifting rod.

[0014] Furthermore, the diameter of the central through-hole in the bottom of the furnace body, the bottom and top of the crystallizer, and the heat insulation baffle is equal to the diameter of the lifting rod.

[0015] Furthermore, a sealing ring is installed around the furnace cover to ensure the vacuum level of the water-cooled furnace body during operation.

[0016] Furthermore, the furnace body is a water-cooled furnace body, and the crystallizer is a water-cooled crystallizer. The cooling medium in both the water-cooled furnace body and the water-cooled crystallizer is water, with a water temperature of 4 to 50°C and a hydraulic pressure of 0.1 to 2 MPa. The purpose is to dissipate heat from the furnace body and the inside of the crystallizer through water cooling.

[0017] Furthermore, two or more heaters are installed, each equipped with a thermocouple, which can adjust the heater power and temperature separately to keep the heating zone at a uniform temperature.

[0018] The device of this invention can prevent high-temperature alloy samples from being oxidized during heat treatment by using a vacuum environment, and can also precisely control the cooling rate of the alloy, thereby not only meeting the high standards required for industrialization, but also meeting the needs of laboratory research.

[0019] The heat treatment process for nickel-based single-crystal superalloys provided by this invention comprises the following steps:

[0020] (1) Sample preparation

[0021] After grinding each sample surface to 800-1000 grit, polish it, ultrasonically clean it with alcohol and acetone, and then dry it for later use.

[0022] (2) Load the sample into the heat treatment equipment

[0023] Load the sample into the crucible, then place the crucible on the stage. Adjust the height of the lifting rod so that more than half of the crucible's height is within the heating system. Close the furnace lid, open the evacuation valve, and evacuate the furnace to a vacuum level of 7 × 10⁻⁶. -3 Pa~9×10 -3 Pa;

[0024] (3) Heat the sample once.

[0025] Using direct heating or segmented stepped heating, heating is stopped when the heater temperature reaches the solution temperature of 1200-1350℃, and the temperature is maintained for 3-4 hours.

[0026] In direct heating, the heater heating rate is 10–15 °C / min;

[0027] In the segmented stepped heating process, when the heater temperature is below 500℃, the heating rate is 15–30℃ / min; when the heater temperature is between 500 and 800℃, the heating rate is 10–20℃ / min; when the heater temperature is above 800℃, the heating rate is 5–20℃ / min; the interval between two adjacent heating sections is 1–10 min, and heating continues after the thermocouple reading stabilizes.

[0028] (4) Pull the sample into the cooling system

[0029] After the heat preservation in step (3) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3-5 mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3-54℃ / s and cool for 3-10 min.

[0030] (5) Samples heated twice

[0031] During the sample cooling process in step (4), the heater temperature is adjusted to the first aging temperature of 1050-1200℃. After the thermocouple reading stabilizes, the height of the lifting rod is adjusted so that more than half of the crucible height is located in the heating system. The sample located in the crucible is heated by the heater to reach 1050-1200℃ and kept at that temperature for 3.5-5.5 hours.

[0032] (6) Pull the sample into the cooling system a second time.

[0033] After the heat preservation in step (5) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3-5 mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3-54℃ / s and cool for 3-20 minutes.

[0034] (7) Samples heated three times

[0035] During the sample cooling process in step (6), the heater temperature is adjusted to the secondary aging temperature of 750-950℃. After the thermocouple reading stabilizes, the height of the lifting rod is adjusted so that more than half of the crucible height is located in the heating system. The sample located in the crucible is heated by the heater so that the sample reaches 750-950℃ and is kept at that temperature for 16-21 hours.

[0036] (8) Pull the sample into the cooling system three times.

[0037] After the heat preservation in step (7) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3-5 mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3-54℃ / s and cool for 3-50 min.

[0038] (9) While performing step (8), turn off the heater. When the thermocouple reading is below 300°C, open the vent valve to release the vacuum, open the furnace cover, raise the lifting rod, and take out the sample.

[0039] This completes the heat treatment process for the sample.

[0040] Furthermore, before heat treatment, the sample is placed in a matching crucible to avoid contact with the Ga-In-Sn solution coolant, thereby preventing the sample from reacting with the Ga-In-Sn solution coolant and providing a protective effect.

[0041] Furthermore, the stirrer must continuously stir the Ga-In-Sn solution during the cooling process to keep the coolant temperature between 10 and 25°C.

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

[0043] First, this invention utilizes the principle of directional solidification to heat-treat nickel-based single-crystal superalloys, which can, to a certain extent, avoid the impact of initial melting on the integrity of the single crystal during the heat treatment process. The sample is kept in a vacuum throughout the heat treatment process, preventing oxidation. Based on the principle that cooling rate R = temperature gradient G × pulling rate V, the cooling rate during the heat treatment process can be precisely adjusted by changing the pulling rate, allowing for accurate control of the cooling rate's influence on the alloy's microstructure. Furthermore, the Ga-In-Sn solution coolant used offers significant advantages in terms of precision control.

[0044] Secondly, this invention can meet the overall process requirements of the heat treatment process of nickel-based single crystal high-temperature alloys, can accurately control the cooling rate of high-temperature alloys, is highly operable and efficient, and can not only meet the high standards of industrial production, but is also very suitable for laboratory research. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0046] Figure 2 This is a schematic diagram of the vacuum system of the present invention.

[0047] Figure 3 This is a schematic diagram of the heating system of the present invention.

[0048] Figure 4 This is a schematic diagram of the cooling system of the present invention.

[0049] Figure 5 This is a schematic diagram of the pull-out system of the present invention.

[0050] Figure 6 This is a schematic diagram of the structure of an embodiment of the present invention.

[0051] In the diagram: 1. Vacuum system; 2. Heating system; 3. Cooling system; 4. Pull-out system; 101. Furnace cover; 102. Furnace body; 1021. Heating system furnace body; 1022. Cooling system furnace body; 103. Ejection valve; 1031. Heating system ejection valve; 1032. Cooling system ejection valve; 104. Venting valve; 1041. Heating system venting valve; 1042. Cooling system venting valve; 201. Insulation layer; 202. Heater; 203. Thermocouple; 204. Heat insulation baffle; 205. Furnace door; 301. Stirrer; 302. Crystallizer; 303. Ga-In-Sn solution coolant; 401. Stage; 402. Lifting rod; 5. Control panel; 6. Wire. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0053] Example 1

[0054] like Figure 6As shown, the equipment for heat treatment of nickel-based single-crystal high-temperature alloys of the present invention includes a furnace cover 101, a furnace body 1021 for heating system, a furnace body 1022 for cooling system, a suction valve 1031 for heating system, a suction valve 1032 for cooling system, a venting valve 1041 for heating system, a venting valve 1042 for cooling system, an insulation layer 201, a heater 202, a thermocouple 203, a heat insulation baffle 204, an automatic push door 205, a stirrer 301, a crystallizer 302, a platform 401, and a lifting rod 40. 2. Control panel 5, wires 6; Vacuum system 1 is equipped with a heating system furnace body 1021 with furnace cover 101 and a cooling system furnace body 1022. Heating system 2 is equipped with insulation layer 201, heater 202, thermocouple 203, heat insulation baffle 204 and furnace door 205. Cooling system 3 is equipped with stirrer 301 and crystallizer 302. Ga-In-Sn solution coolant 303 is placed in crystallizer 302. Pull-out system 4 is equipped with platform 401 and lifting rod 402.

[0055] The furnace cover 101 is located above the furnace body 1021 of the heating system. A heating system exhaust valve 1031 is installed on the left side of the furnace body 1021, used to extract gas from the furnace body 1021. A heating system vent valve 1041 is installed on the right side of the furnace body 1021, used to release the vacuum in the furnace body 1021. The bottom of the furnace body 1021 is vertically connected to the top of the furnace body 1022 of the cooling system via a heat insulation baffle 204. The heat insulation baffle 204 is made of plate-shaped porous alumina ceramic material with a thickness of 30mm, and can be replaced according to actual conditions to obtain the best heat insulation effect. A cooling system exhaust valve 1032 is installed on the left side of the furnace body 1022, used to extract gas from the furnace body 1022. A cooling system vent valve 1042 is installed on the right side of the furnace body 1022, used to release the vacuum in the furnace body 1022.

[0056] Heating system 2 is placed inside heating system furnace body 1021; furnace door 205 is horizontally connected to the upper end of insulation layer 201 for easy inspection of equipment components and placement of samples; heater 202 is located inside insulation layer 201; the distance between the outer wall of heater 202 and the inner wall of insulation layer 201 is 15mm; thermocouple 203 is located 10mm below heater 202; one side of thermocouple 203 is vertically connected to the inner wall of insulation layer 201; heater 202 is square and made of graphite; heater 202 is 5mm thick, 5mm long, and 22mm high; the bottom of insulation layer 201 is connected to the inner bottom of heating system furnace body 1021; insulation layer 201 is square and made of multi-layer carbon felt, with a thickness of 25mm and a height of 300mm.

[0057] Cooling system 3 is placed inside cooling system furnace body 1022; crystallizer 302 is a square vessel with a length of 200mm, a width of 200mm, and a height of 350mm; the bottom of crystallizer 302 is connected to the bottom of the inner side of cooling system furnace body 1022; Ga-In-Sn solution coolant 303 is contained in crystallizer 302, the liquid level of Ga-In-Sn solution coolant 303 is 15mm away from the top of crystallizer 302, its temperature is 10~25℃, and the hydraulic pressure is 0.1~2Mpa.

[0058] The lifting rod 402 of the pull-out system 4 passes longitudinally through the bottom of the cooling system furnace body 1022, through the bottom and top of the crystallizer 302, the heat insulation baffle 204, and the central hole at the bottom of the heating system furnace body 1021, and extends into the heating system 2. It can reciprocate between the heating system 2 and the cooling system 3. The diameter of the central through hole at the bottom of the heating system furnace body 1021, the bottom of the cooling system furnace body 1022, the bottom and top of the crystallizer 302, and the heat insulation baffle 204 is 65mm, and the diameter of the lifting rod 402 is 65mm. The platform 401 is placed on top of the lifting rod 402 and vertically connected. The stirrer 301 is located at the center of the outer wall of the platform 401, and its area is 2 / 3 of the area of ​​the platform 401.

[0059] The control panel 5 is connected to the bottom outer wall of the cooling system furnace body 1022 by a wire 6, which facilitates the operation of the equipment; when the suction valve or the vent valve is activated, the corresponding valves of the heating system furnace body 1021 and the cooling system furnace body 1022 operate synchronously; when vacuuming, the vacuum levels of the heating system furnace body 1021 and the cooling system furnace body 1022 are the same.

[0060] A sealing ring is installed around the furnace cover 101 to ensure the vacuum level during furnace operation.

[0061] Both the heating system furnace body 1021 and the cooling system furnace body 1022 are water-cooled furnace bodies; the crystallizer 302 is a water-cooled crystallizer; the cooling medium in both the water-cooled furnace body and the water-cooled crystallizer is water, with a water temperature of 4 to 50°C and a hydraulic pressure of 0.1 to 2 MPa. The purpose is to dissipate heat from the furnace body and the inside of the crystallizer through water cooling.

[0062] Two or more heaters 202 can be installed. Each heater 202 is equipped with a thermocouple 203 and is placed symmetrically within the insulation layer 201 to maintain a uniform temperature in the heating zone. The heaters 202 and thermocouples 203 are 10mm apart vertically. The uppermost heater is 10mm away from the upper inner wall of the insulation layer 201, and the lowermost thermocouple is 10mm away from the bottom inner wall of the furnace body 1021 of the heating system.

[0063] Example 2

[0064] In this embodiment, three DD91 nickel-based single-crystal superalloy samples were selected. Under a set temperature gradient of 280℃ / cm, different cooling rates were chosen for the experiments. The aim was to ensure microstructural stability while observing the decrease in dendrite spacing of the alloy samples with increasing cooling rate. The main steps of the heat treatment process are as follows:

[0065] Step 1: Prepare the sample.

[0066] In this embodiment, three DD91 nickel-based single-crystal superalloy round bar samples with a diameter of 4 mm and a length of 25 mm were selected and labeled as sample 1, sample 2, and sample 3, respectively. The surface of each sample was ground to 1000 grit and then polished. After ultrasonic cleaning with alcohol and acetone, the samples were dried and ready for use.

[0067] Three DD91 nickel-based single-crystal superalloy round bar samples were given preset cooling rates of 16.8℃ / s, 22.4℃ / s, and 28℃ / s, respectively. According to the cooling rate formula, the pulling speeds of the three samples were set to 600μm / s, 800μm / s, and 1000μm / s, respectively.

[0068] Step 2: Load the sample into the heat treatment equipment.

[0069] Place sample #1 into the crucible and place it on the stage 401. Adjust the height of the lifting rod 402 so that half the height of the crucible is located in the heating system 2; close the furnace cover 101 and the furnace door 205. Simultaneously open the heating system exhaust valve 1031 and the cooling system exhaust valve 1032 to evacuate the furnace body 1021 of the heating system and the furnace body 1022 of the cooling system to a vacuum level of 9 × 10⁻⁶. -3 Pa.

[0070] Step 3: Heat the sample once.

[0071] The heating method is direct heating. When the temperature of heater 202 reaches the solution temperature of 1350℃, heating is stopped and the temperature is maintained for 3 hours. The heating rate of heater 202 is 15℃ / min.

[0072] Step 4: Pull the sample into the cooling system at a preset speed.

[0073] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 600 μm / s to pull sample #1 into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303. The cooling rate is controlled at 16.8℃ / s, and the cooling time is 5 min.

[0074] Step 5: Reheat the sample.

[0075] During the cooling process of sample #1 in step 4, the temperature of heater 202 is adjusted to the primary aging temperature of 1200℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample #1 reaches 1200℃ and is held at that temperature for 5.5 hours.

[0076] Step 6: Pull the sample into the cooling system a second time at a preset speed.

[0077] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 600 μm / s to pull sample #1 into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303. The cooling rate is controlled at 16.8℃ / s, and the cooling time is 5 min.

[0078] Step 7: Heate the sample three times.

[0079] During the cooling process of sample #1 in step 6, the temperature of heater 202 is adjusted to the secondary aging temperature of 950℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample #1 reaches 950℃ and is kept at that temperature for 21 hours.

[0080] Step 8: Pull the sample into the cooling system three times at a preset speed.

[0081] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 600 μm / s to pull sample #1 into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303. The cooling rate is controlled at 16.8℃ / s, and the cooling time is 5 min.

[0082] Step 9: While performing Step 8, turn off heater 202. When the reading of thermocouple 203 is below 300°C, simultaneously open the vent valve 1041 of the heating system and the vent valve 1042 of the cooling system to release the vacuum. Open furnace cover 101 and furnace door 205, raise lifting rod 402, and remove sample #1.

[0083] This completes the heat treatment process for sample #1.

[0084] Step 10, heat treatment experiments for the remaining samples:

[0085] Repeat steps 2 to 9, and conduct heat treatment experiments on sample #2 and sample #3 at pulling speeds of 800 μm / s and 1000 μm / s respectively, until the heat treatment experiments of all samples are completed.

[0086] This concludes the heat treatment experiment of DD91 nickel-based single crystal superalloy.

[0087] Example 3

[0088] In this embodiment, five DZ22 nickel-based single-crystal superalloy samples were selected. Under a set temperature gradient of 300℃ / cm, different cooling rates were chosen for the experiments. The aim was to ensure microstructural stability while observing the decrease in the size of the γ / γ' phases of the alloy samples as the cooling rate increased. The main steps of the heat treatment process are as follows:

[0089] Step 1: Prepare the sample.

[0090] In this embodiment, five DZ22 nickel-based single-crystal superalloy round bars with a diameter of 4 mm and a length of 20 mm were selected and labeled as sample a#, sample b#, sample c#, sample d#, and sample e#. Each sample surface was ground to 1000 grit, polished, ultrasonically cleaned with alcohol and acetone, and then dried for later use.

[0091] The five DZ22 nickel-based single-crystal high-temperature alloy round bar samples were pre-cooled at rates of 9℃ / s, 13.5℃ / s, 18℃ / s, 24℃ / s, and 54℃ / s, respectively. Based on the cooling rate formula, the pulling speeds of the five samples were set to 300μm / s, 450μm / s, 600μm / s, 800μm / s, and 1800μm / s, respectively.

[0092] Step 2: Load the sample into the heat treatment equipment.

[0093] Place sample a# into the crucible and place it on the stage 401. Adjust the height of the lifting rod 402 so that half the height of the crucible is located in the heating system 2; close the furnace cover 101 and the furnace door 205. Simultaneously open the heating system evacuation valve 1031 and the cooling system evacuation valve 1032 to evacuate the furnace body 1021 of the heating system and the furnace body 1022 of the cooling system to a vacuum level of 8×10⁻⁶. -3 Pa.

[0094] Step 3: Heat the sample once.

[0095] The heating method is a segmented, stepped temperature increase. When the temperature of heater 202 reaches the solution temperature of 1280℃, heating is stopped and the temperature is maintained for 3.5 hours.

[0096] In the segmented stepped heating process, when the temperature of heater 202 is below 500℃, the heating rate is 30℃ / min; when the temperature of heater 202 is between 500℃ and 800℃, the heating rate is 20℃ / min; when the temperature of heater 202 is above 800℃, the heating rate is 20℃ / min; the interval between two adjacent heating sections is 1min; and heating continues after the reading of thermocouple 203 stabilizes.

[0097] Step 4: Pull the sample into the cooling system at a preset speed.

[0098] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 1800 μm / s to pull the a# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303, and the cooling rate is controlled at 54℃ / s for 3 min.

[0099] Step 5: Reheat the sample.

[0100] During the cooling process of sample a# in step 4, the temperature of heater 202 is adjusted to the primary aging temperature of 1130℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample a# reaches 1130℃ and is held at that temperature for 4.5 hours.

[0101] Step 6: Pull the sample into the cooling system a second time at a preset speed.

[0102] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 1800 μm / s to pull the a# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303, and the cooling rate is controlled at 54℃ / s for 3 min.

[0103] Step 7: Heate the sample three times.

[0104] During the cooling process of sample a# in step 6, the temperature of heater 202 is adjusted to the secondary aging temperature of 850℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample a# reaches 850℃ and is held at that temperature for 18 hours.

[0105] Step 8: Pull the sample into the cooling system three times at a preset speed.

[0106] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 1800 μm / s to pull the a# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303, and the cooling rate is controlled at 54℃ / s for 3 min.

[0107] Step 9: While performing Step 8, turn off heater 202. When the reading of thermocouple 203 is below 300°C, simultaneously open the vent valve 1041 of the heating system and the vent valve 1042 of the cooling system to release the vacuum. Open furnace cover 101 and furnace door 205, raise lifting rod 402, and remove sample a#.

[0108] This completes the heat treatment process for sample a#.

[0109] Step 10, heat treatment experiments for the remaining samples:

[0110] Repeat steps 2 to 9, and sequentially perform heat treatment experiments on samples b#, c#, d# and e# at pulling rates of 300 μm / s, 450 μm / s, 600 μm / s and 800 μm / s, respectively, until the heat treatment experiments of all samples are completed.

[0111] This concludes the heat treatment experiment of DZ22 nickel-based single crystal superalloy.

[0112] Example 4

[0113] In this embodiment, four DD6 nickel-based single-crystal superalloy samples were selected. Under a set temperature gradient of 200℃ / cm, different cooling rates were chosen for the experiments. The aim was to ensure microstructural stability while observing the gradual transformation of the γ / γ' phases from cubic to spherical shapes as the cooling rate increased. The main steps of the heat treatment process are as follows:

[0114] Step 1: Prepare the sample.

[0115] In this embodiment, four DD6 nickel-based single-crystal superalloy round bar samples with a diameter of 4 mm and a length of 15 mm were selected and labeled as sample A#, sample B#, sample C#, and sample D#, respectively. Each sample surface was ground to 800 grit, polished, ultrasonically cleaned with alcohol and acetone, and then dried for later use.

[0116] The four DD6 nickel-based single-crystal superalloy round bar samples have preset cooling rates of 0.3℃ / s, 4℃ / s, 12℃ / s, and 16℃ / s, respectively. According to the cooling rate formula, the pulling speeds of the five samples are set to 15μm / s, 200μm / s, 600μm / s, and 800μm / s, respectively.

[0117] Step 2: Load the sample into the heat treatment equipment.

[0118] Place sample A# into the crucible and place it on the stage 401. Adjust the height of the lifting rod 402 so that half the height of the crucible is located in the heating system 2; close the furnace cover 101 and the furnace door 205. Simultaneously open the heating system evacuation valve 1031 and the cooling system evacuation valve 1032 to evacuate the furnace body 1021 of the heating system and the furnace body 1022 of the cooling system to a vacuum level of 7 × 10⁻⁶. -3 Pa.

[0119] Step 3: Heat the sample once.

[0120] The heating method is a segmented, stepped heating. When the temperature of heater 202 reaches the solution temperature of 1200℃, the heating is stopped and the temperature is maintained for 4 hours.

[0121] In the segmented stepped heating process, when the temperature of heater 202 is below 500℃, the heating rate is 15℃ / min; when the temperature of heater 202 is between 500℃ and 800℃, the heating rate is 10℃ / min; when the temperature of heater 202 is above 800℃, the heating rate is 5℃ / min; the interval between two adjacent heating sections is 10min; and heating continues after the reading of thermocouple 203 stabilizes.

[0122] Step 4: Pull the sample into the cooling system at a preset speed.

[0123] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 15 μm / s to pull the A# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303, and the cooling rate is controlled at 0.3℃ / s for 10 min.

[0124] Step 5: Reheat the sample.

[0125] During the cooling process of sample A# in step 4, the temperature of heater 202 is adjusted to the primary aging temperature of 1050℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample A# reaches 1050℃ and is held at that temperature for 3.5 hours.

[0126] Step 6: Pull the sample into the cooling system a second time at a preset speed.

[0127] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 15 μm / s to pull the A# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303, and the cooling rate is controlled at 0.3℃ / s for 20 min.

[0128] Step 7: Heate the sample three times.

[0129] During the cooling process of sample A# in step 6, the temperature of heater 202 is adjusted to the secondary aging temperature of 750℃. After the reading of thermocouple 203 stabilizes, the height of lifting rod 402 is adjusted so that half of the crucible height is located in heating system 2. The sample located in the crucible is heated by heater 202, so that sample A# reaches 750℃ and is held at that temperature for 16 hours.

[0130] Step 8: Pull the sample into the cooling system three times at a preset speed.

[0131] After the previous heat preservation step is completed, the lifting rod 402 is lowered at a preset pulling speed of 15 μm / s to pull the A# sample into the Ga-In-Sn solution coolant 303, so that the upper end of the crucible is 5 mm higher than the liquid surface of the Ga-In-Sn solution coolant 303. The cooling rate is controlled at 0.3℃ / s, and the cooling time is 50 min.

[0132] Step 9: While performing Step 8, turn off heater 202. When the reading of thermocouple 203 is below 300°C, simultaneously open the vent valve 1041 of the heating system and the vent valve 1042 of the cooling system to release the vacuum. Open furnace cover 101 and furnace door 205, raise lifting rod 402, and remove sample A#.

[0133] This completes the heat treatment process for sample A#.

[0134] Step 10, heat treatment experiments for the remaining samples:

[0135] Repeat steps 2 to 9, and sequentially perform heat treatment experiments on samples B#, C#, and D# at pulling rates of 200 μm / s, 600 μm / s, and 800 μm / s, respectively, until all samples have undergone heat treatment experiments.

[0136] This concludes the heat treatment experiment of DD6 nickel-based single crystal superalloy.

Claims

1. A device for heat treatment of nickel-based single-crystal superalloys, characterized in that, It includes a vacuum system, a heating system, a cooling system, and a pull-out system; the vacuum system is equipped with a furnace body with a furnace cover, an exhaust valve, and a vent valve; the heating system is equipped with an insulation layer, a heater, a thermocouple, and a heat insulation baffle; the cooling system is equipped with a crystallizer and a stirrer; and the pull-out system is equipped with a platform and a lifting rod. The heating system is placed inside the furnace body, the heater is located inside the insulation layer, the thermocouple is located below the heater, one side of the thermocouple is perpendicularly connected to the inner wall of the insulation layer, and the bottom of the insulation layer is connected to the heat insulation baffle. The cooling system is located inside the furnace body, and the crystallizer is a water-cooled crystallizer. The bottom of the crystallizer is connected to the inner bottom of the furnace body. The stirrer is located on one side of the outer wall of the insulation layer and extends into the crystallizer through the heat insulation baffle. The stirrer is located at the center of the outer wall of the platform, and its area is 2 / 3 of the platform. The crystallizer contains a Ga-In-Sn solution coolant. The height of the Ga-In-Sn solution coolant is 5~15mm away from the top of the crystallizer. The solution temperature is 10~25℃, and the hydraulic pressure is 0.1~2Mpa. The lifting rod of the pull-out system passes longitudinally through the bottom of the furnace body, through the bottom and top of the crystallizer of the cooling system, and through the central hole of the heat insulation baffle, and extends into the heating system. It can reciprocate between the heating system and the cooling system. The platform is placed on top of the lifting rod.

2. The equipment for heat treatment of nickel-based single-crystal superalloys according to claim 1, characterized in that, A furnace cover is installed on the top of the furnace body, and an exhaust valve and a vent valve are installed on the side of the furnace body; the bottom of the heating system is vertically connected to the top of the cooling system via a heat insulation baffle.

3. The equipment for heat treatment of nickel-based single-crystal superalloys according to claim 1 or 2, characterized in that, The heater is made of graphite, the insulation layer is made of multi-layer carbon felt, and the heat insulation baffle is made of plate-shaped porous alumina ceramic material.

4. The equipment for heat treatment of nickel-based single-crystal superalloys according to claim 1, characterized in that, The diameter of the central through hole in the bottom of the furnace body, the bottom and top of the crystallizer, and the heat insulation baffle is equal to the diameter of the lifting rod; a sealing ring is installed around the furnace cover.

5. The apparatus for heat treatment of nickel-based single-crystal superalloys according to any one of claims 1, 2, or 4, characterized in that, The furnace body is a water-cooled furnace body. The cooling medium in both the water-cooled furnace body and the water-cooled crystallizer is water, with a water temperature of 4~50℃ and a hydraulic pressure of 0.1~2Mpa. There are two or more heaters, and each heater is equipped with a thermocouple.

6. The equipment for heat treatment of nickel-based single-crystal superalloys according to claim 3, characterized in that, The furnace body is a water-cooled furnace body. The cooling medium in both the water-cooled furnace body and the water-cooled crystallizer is water, with a water temperature of 4~50℃ and a hydraulic pressure of 0.1~2Mpa. There are two or more heaters, and each heater is equipped with a thermocouple.

7. A process for heat treating nickel-based single-crystal superalloys using the equipment described in any one of claims 1 to 6, characterized in that, The steps include the following: (1) Preparation of test samples After grinding each sample surface to 800-1000 grit, polish it, ultrasonically clean it with alcohol and acetone, and then dry it for later use. (2) Load the sample into the heat treatment equipment Place the sample into the crucible, then place the crucible on the stage. Adjust the height of the lifting rod so that more than half of the crucible's height is within the heating system. Close the furnace lid, open the evacuation valve, and evacuate the furnace to a vacuum level of 7 × 10⁻⁶. -3 Pa ~ 9×10 -3 Pa; (3) Heating the sample once Using direct heating or segmented stepped heating, heating is stopped when the heater temperature reaches the solution temperature of 1200~1350℃, and the temperature is maintained for 3~4 hours. (4) Pull the sample into the cooling system. After the heat preservation in step (3) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3~5mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3~54℃ / s and cool for 3~10min. (5) Secondary heating of the sample During the sample cooling process in step (4), the heater temperature is adjusted to the first aging temperature of 1050~1200℃. After the thermocouple reading stabilizes, the height of the lifting rod is adjusted so that more than half of the crucible height is located in the heating system. The sample located in the crucible is heated by the heater so that the sample reaches 1050~1200℃ and is kept at that temperature for 3.5~5.5h. (6) Pull the sample into the cooling system a second time. After the heat preservation in step (5) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3~5mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3~54℃ / s and cool for 3~20min. (7) Three heating of the sample During the sample cooling process in step (6), the heater temperature is adjusted to the secondary aging temperature of 750~950℃. After the thermocouple reading stabilizes, the height of the lifting rod is adjusted so that more than half of the crucible height is located in the heating system. The sample located in the crucible is heated by the heater so that the sample reaches 750~950℃ and is kept at that temperature for 16~21h. (8) Pull the sample into the cooling system three times. After the heat preservation in step (7) is completed, lower the lifting rod and pull the sample into the crystallizer so that the upper surface of the crucible is 3~5mm higher than the liquid surface of the Ga-In-Sn solution coolant. Control the cooling rate at 0.3~54℃ / s and cool for 3~50min. (9) While performing step (8), turn off the heater. When the thermocouple reading is below 300°C, open the vent valve to release the vacuum, open the furnace cover, raise the lifting rod, and take out the sample.

8. The process according to claim 7, characterized in that, In direct heating, the heating rate of the heater is 10~15℃ / min; in segmented stepped heating, when the heater temperature is below 500℃, the heating rate is 15~30℃ / min; when the heater temperature is 500~800℃, the heating rate is 10~20℃ / min; when the heater temperature is above 800℃, the heating rate is 5~20℃ / min; the interval between two adjacent heating sections is 1~10min, and heating continues after the thermocouple reading stabilizes.

Images