A method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction

Abstract

This invention discloses a method for preparing Cr2Nb / Cu composite materials via laser selective melting in situ reaction, specifically including the following steps: Step 1, weighing Cu-Cr alloy powder, Nb powder, and Cu powder according to a specified ratio; Step 2, mixing the Cu-Cr binary powder with Nb powder, then adding Cu powder and mixing again, and drying the resulting mixed powder; Step 3, constructing a specimen model for a 3D printing device and importing the constructed specimen model into the 3D printing device; Step 4, loading the dried powder into the 3D printing device for printing to obtain a deposited Cr2Nb / Cu composite material; Step 5, heat-treating the Cr2Nb / Cu composite material to obtain the Cr2Nb / Cu composite material. This invention solves the problems of high cost and low yield in the existing preparation process of Cu, Cr, and Nb ternary composite materials.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology for copper-based composite materials, and relates to a method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction. Background Technology

[0002] Cr2Nb / Cu composites, with their high strength, high electrical conductivity, and excellent thermal stability at high temperatures, have become the preferred material for combustion chamber linings of next-generation aerospace engines. Selective laser melting (SLM), as an emerging technology in recent years, is gradually replacing traditional manufacturing methods and becoming the preferred technology for core components of high-end equipment due to its ability to integrate complex structures and its material utilization rate exceeding 95%. Cr2Nb / Cu composites rely on the dispersed distribution and small size of the Cr2Nb reinforcing phase to improve the overall performance of the material; SLM technology uses a laser beam to scan and generate tiny molten pools and heat-affected zones, while simultaneously providing the material with an extremely high cooling rate (10⁻⁶). 4 ~10 6 The resulting Cr2Nb reinforcing phase (K / s) is small in size, which greatly improves the mechanical properties of the material. Therefore, combining SLM and Cr2Nb / Cu composite materials for integrated molding of rocket engine combustion chamber linings is a future development trend.

[0003] However, SLM requires powders with high sphericity and good flowability as raw materials. Currently, Cr2Nb / Cu composite powders are prepared using gas atomization. However, due to the significant difference in melting points among the three components Cu, Cr, and Nb, the high-melting-point Nb component is difficult to completely melt during the smelting process. Therefore, a large superheat is required to completely melt the raw materials and achieve good flowability in the melt. However, excessive superheat can lead to severe material burn-off and increase the solidification time of the melt, resulting in high costs for preparing Cu, Cr, and Nb ternary powders. In addition, molten droplets tend to stick together during flight, increasing the probability of satellite powders and other irregularly shaped powders, which is detrimental to powder forming. Therefore, the mass production of composite powders is difficult, and the yield is low. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction, which solves the problems of high preparation cost and low yield of Cu, Cr, and Nb ternary powders in the preparation process of Cr2Nb / Cu composite materials.

[0005] The technical solution adopted in this invention is a method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction, which specifically includes the following steps:

[0006] Step 1: Weigh out Cu-Cr alloy powder, Nb powder, and Cu powder according to the specified proportions;

[0007] Step 2: Mix Cu-Cr binary powder with Nb powder, then add Cu powder and mix again. Dry the resulting mixed powder.

[0008] Step 3: Construct the specimen model for the 3D printing equipment and import the constructed specimen model into the 3D printing equipment;

[0009] Step 4: Load the dried powder into a 3D printing device for printing to obtain a deposited Cr2Nb / Cu composite material;

[0010] Step 5: Heat-treat the Cr2Nb / Cu composite material to obtain the Cr2Nb / Cu composite material.

[0011] The invention is further characterized by:

[0012] In step 1, 10-40 wt.% Cu-Cr powder, 1.5-6 wt.% Nb powder, 10-15 wt.% Cu powder with a particle size of 1-2 μm, and 39-73.5 wt.% Cu powder with a particle size of 15-45 μm are weighed according to their respective weight percentages.

[0013] In step 1, the density of Cr in Cu-Cr is the same as that of Nb. Cu-Cr powder with a particle size of 20-53 μm is screened out, and Nb powder with a particle size of 20-53 μm, Cu powder with a particle size of 1-2 μm, and Cu powder with a particle size of 15-45 μm are also taken.

[0014] The specific process of step 2 is as follows:

[0015] First, Cu-Cr binary powder and Nb powder are mixed. Cu powder with a particle size of 15-45μm is divided into several equal parts and mixed for 2-4 hours each time. Finally, Cu powder with a particle size of 1-2μm is added and mixed for 6-8 hours to obtain a mixed powder. The powder is then heated in a vacuum chamber at a temperature of 80-150℃.

[0016] The specific process of step 3 is as follows:

[0017] Draw a rectangular 3D model and import it into slicing software for 2D slicing with a single layer thickness of 25-30μm. Set the printing order and generate a .STL file to obtain the specimen model that the 3D printing equipment can read. Import the completed specimen model into the 3D printing equipment.

[0018] The specific process of step 4 is as follows:

[0019] Step 4.1: Load the dried powder into the powder supply chamber of the 3D printing equipment, close the chamber door and perform gas washing. Introduce argon gas to remove the oxygen from the molding chamber. After the gas washing is completed, start the substrate preheating. After heating to the preheating temperature, turn on the fan.

[0020] Step 4.2: Before printing, a layer of powder is pre-laid on the substrate for scanning and melting. First, a laser with a power of 430-450w is used for melting, and the powder is not further laid. Then, a laser with a power of 360-380w is used for melting. After the laser scan is repeated, another layer of powder is laid until the printing is completed, and finally, the deposited Cr2Nb / Cu composite material is obtained.

[0021] In step 4.2, the printing process is as follows: laser scanning rate 600-700 mm / s; single-layer printing thickness 25-30 μm; repetitive printing process is as follows: laser scanning rate 1000-1500 mm / s; scanning method is stripe pattern.

[0022] The specific process of step 5 is as follows: heating is carried out in a muffle furnace. After the temperature reaches the preset temperature, the sample is placed in for aging treatment. After the aging time is reached, the sample is cooled to room temperature by air cooling. The aging temperature is 450-600℃ and the aging time is 1-5h.

[0023] The beneficial effects of this invention are as follows:

[0024] 1) Based on theoretical calculations of Cu-Cr density, Cu-17Cr wt.% alloy powder was prepared in-house, ensuring that both the Cu-Cr alloy powder and Nb powder had a density of 8.57 g / cm³. 3 The density difference between Cu and the three powders is within 0.04%, so they will not separate due to density differences during mixing. The preparation of Cu-Cr alloy powder by gas atomization is relatively simple and the process is currently mature. Therefore, the raw materials and processes are simple and the cost is low.

[0025] 2) SLM first uses a high-energy-density laser to ensure the Nb powder melts, allowing Nb and Cr elements to react in situ to form Cr2Nb particles. However, the melt superheat is high at this stage, resulting in large Cr2Nb particles. Since the melting point of Cr2Nb particles (1870℃) is lower than that of Nb powder (2468℃), a second scan with a lower energy density is performed to remelt the Cr2Nb particles generated in the first scan. Due to the low superheat and fast solidification rate during the second solidification, the Cr2Nb particles generated during the second solidification process are more dispersed and finer, improving the microstructure of the composite material and enhancing its overall performance. Simultaneously, the second low-temperature remelting also reduces the melt pool size, ensuring better surface quality of the molded sample. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction according to the present invention;

[0027] Figure 2A physical image of the sample prepared in Example 1 of the method for preparing Cr2Nb / Cu composite material by laser selective melting in situ reaction according to the present invention;

[0028] Figure 3 SEM image of the Cr2Nb / Cu composite material prepared in Example 1 of the method for preparing Cr2Nb / Cu composite material by laser selective melting in situ reaction according to the present invention;

[0029] Figure 4 The stress-strain curve of the Cr2Nb / Cu composite material prepared in the aged state according to Example 1 of the method for preparing Cr2Nb / Cu composite material by laser selective melting in situ reaction of the present invention. Detailed Implementation

[0030] The following detailed description is provided in conjunction with specific implementation methods.

[0031] The present invention provides a method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction, the process of which is as follows: Figure 1 As shown, Cu-Cr powder was prepared using a gas atomization method. Cu-Cr binary powder, Nb powder, and Cu powder were mixed and synthesized using SLM (Surface Mount Technology). By calculating the proportion of Cu-Cr binary powder, and employing specific mixing methods, printing parameters, and heat treatment processes, the fabrication of high-performance Cu-Cr-Nb with a fine and dispersed second phase was achieved. The specific steps include the following:

[0032] Step 1, raw material calculation, specifically:

[0033] Step 1.1: Calculate the proportion of Cr in the Cu-Cr powder to make its density the same as that of Nb, ensuring that the powder mixing process does not lead to stratification.

[0034] Step 1.2: Prepare Cu-17Crwt.% powder by gas atomization method, screen out Cu-Cr powder with a particle size of 20-53μm, take Nb powder with a particle size of 20-53μm, Cu powder with a particle size of 1-2μm, and Cu powder with a particle size of 15-45μm.

[0035] Step 2, powder preparation and ingredient formulation, specifically: weigh out the following by weight percentage: 10-40 wt.% Cu-Cr powder, 1.5-6 wt.% Nb powder, 10-15 wt.% Cu powder with a particle size of 1-2 μm, and 39-78.5 wt.% Cu powder with a particle size of 15-45 μm. Using some 1-2 μm Cu powder allows it to fill the gaps between the Cu-Cr and Nb powders, ensuring uniformity of the powder during mixing and improving the density of the powder bed during subsequent spreading.

[0036] Step 3, mixing the powders, specifically:

[0037] Step 3.1: Take the Cu-Cr binary powder and Nb powder from Step 2 and mix them using a three-dimensional mixer. The mixer process is as follows: power 0.55KW, speed 20rpm, and filling rate 35%. The three-dimensional mixer uses gentle tumbling motion to achieve mixing, reducing mechanical stress on the powder and avoiding damage to sphericity.

[0038] Step 3.2: Divide the Cu powder with a particle size of 15-45μm from Step 1 into 3 equal parts and mix them. Add 1 part each time and mix for 2-4 hours.

[0039] Step 3.3: Add 1-2 μm Cu powder and mix for 6-8 hours.

[0040] Step 3.4: Obtain the mixed powder and heat it in a vacuum oven. The vacuum oven is evacuated to a vacuum level ≤ -0.1, the heating temperature is 80-150℃, and the holding time is 4 hours.

[0041] Step 4, modeling, specifically:

[0042] Step 4.1: Draw a 20mm × 60mm × 10mm cuboid 3D model;

[0043] Step 4.2: Import the slicing software for two-dimensional slicing and layering, with a single layer thickness of 25-30μm. Set the printing order and generate a file in .STL format to obtain the specimen model that the 3D printing equipment can read.

[0044] Step 4.3: Import the completed sliced ​​layer file model into the 3D printing equipment.

[0045] Step 5, print, specifically:

[0046] Step 5.1: Load the dried powder from Step 3 into the powder supply chamber of the 3D printing equipment, close the chamber door, and perform gas purging by introducing argon gas to remove oxygen from the molding chamber and ensure the oxygen content is less than 400 ppm during the printing process. After gas purging, start the substrate preheating process at 100°C to reduce thermal stress during molding. After reaching the preheating temperature, turn on the fan at a speed of 55 mm / s. 3 / h;

[0047] Step 5.2: Before printing, a layer of powder is pre-laid on the substrate for scanning and melting. First, a high-energy-density laser (430-450W laser power) is used for melting, without further powder laying. Then, a low-energy-density laser (360-380W laser power) is used for melting. After repeated laser scanning, another layer of powder is laid, and the steps are repeated (powder laying, first scan, second scan, second powder laying, first scan, second scan) to finally obtain the deposited Cr2Nb / Cu composite material. The printing process is as follows: laser scanning rate 600-700mm / s; single-layer printing thickness 25-30μm; repeated printing process: laser scanning rate 1000-1500mm / s; scanning strategy: stripe pattern; interlayer deflection angle 67°.

[0048] Step 6, Time Limit, specifically:

[0049] Step 6.1: Heat the sample in a muffle furnace until the preset temperature is reached, then place the sample in for aging treatment. The aging temperature is 450-600 ℃, and the aging time is 1-5 hours.

[0050] Step 6.2: After the aging time is reached, use air cooling to cool down to room temperature.

[0051] Example 1

[0052] Step 1: Calculate the Cr content in the Cu-Cr alloy powder, ensuring the density difference between the Cu-Cr alloy powder, Nb powder, and Cu powder is within 0.04%. Prepare Cu-17Cr wt.% powder using gas atomization. Screen the Cu-Cr powder with a particle size of 20-53 μm, and take Nb powder with a particle size of 20-53 μm, Cu powder with a particle size of 1-2 μm, and Cu powder with a particle size of 15-45 μm.

[0053] Step 2: Weigh out 25 wt.% Cu-Cr powder, 3.75 wt.% Nb powder, 10 wt.% Cu powder with a particle size of 1-2 μm, and 61.25 wt.% Cu powder with a particle size of 15-45 μm according to the weight percentage.

[0054] Step 3: Mix the Cu-Cr binary powder with the Nb powder. Divide the Cu powder (15-45 μm particle size) into three equal portions and add them in three batches, mixing for 1 hour each time, for a total of 3 hours. Finally, add 1-2 μm Cu powder and mix for 6 hours to obtain the mixed powder, which is then heated in a vacuum chamber. Mixer specifications: power 0.55 kW, rotation speed 20 rpm, filling rate 35%. Vacuum oven: vacuum degree ≤ -0.1 Pa, heating temperature 80℃, holding time 4 hours.

[0055] Step 4: Draw a 20mm×60mm×10mm cuboid 3D model and import it into slicing software for 2D slicing with a single layer thickness of 30μm. Set the printing order and generate a .STL file to obtain the specimen model that the 3D printing equipment can read. Import the completed sliced ​​and layered model into the 3D printing equipment.

[0056] Step 5: Load the powder from Step 3 into the powder supply chamber of the 3D printer, close the chamber door, and perform gas purging. After gas purging, start the substrate preheating process. Once the preheating temperature is reached, turn on the fan and begin printing. Alternatively, load the powder into the powder supply chamber of the 3D printer, close the chamber door, and perform gas purging by introducing high-purity (99.9%) argon gas to remove oxygen from the forming chamber and ensure the oxygen content is less than 400 ppm during printing. After gas purging, start the substrate preheating process and turn on the fan at a speed of 55 mm / s. 3 Printing begins after preheating to 100℃. During printing, a powder layer is first deposited on the substrate, followed by high-power laser scanning for melting, and then low-power, high-speed laser scanning for melting again. This process is repeated to ultimately prepare the Cr2Nb / Cu composite material. The printing process is as follows: laser power 440W; laser scanning rate 650mm / s; single-layer printing thickness 25-30μm. The repeating printing process is as follows: laser power 370W; laser scanning rate 1300mm / s; scanning strategy is a stripe pattern; interlayer deflection angle is 67°.

[0057] Step 6: Aging treatment of the obtained sedimentary samples. Aging temperature: 500℃, aging time: 1 hour. Aging method: Heating is performed using a muffle furnace. After the temperature reaches the preset temperature, the sample is placed in the furnace for aging treatment. After the aging time is reached, the sample is cooled to room temperature using air cooling.

[0058] The electrical and mechanical properties of the Cr2Nb / Cu composite material prepared in Example 1 were tested, and its conductivity was found to be 60.5% IACS and its tensile strength was 688 MPa.

[0059] Figure 2 The image shows the finished Cr2Nb / Cu alloy prepared in Example 1. It has good surface roughness and no warping deformation. Figure 3 The image shows a SEM image of the Cr2Nb / Cu alloy prepared in Example 1. The grains are typical of laser-prepared columnar and equiaxed grains, with small grain size, providing a large amount of fine grain reinforcement. Figure 4 The tensile diagram for Example 1 shows a tensile strength of 688 MPa.

[0060] Example 2

[0061] In this embodiment, in step 2, 40 wt.% Cu-Cr powder, 6 wt.% Nb powder, 15 wt.% Cu powder with a particle size of 1-2 μm, and 39 wt.% Cu powder with a particle size of 15-45 μm are weighed out by weight. In step 5, the printing process uses a laser power of 450 W; a laser scanning rate of 600 mm / s; and a single-layer printing thickness of 30 μm. For the repetitive printing process, the laser power is 360 W; the laser scanning rate is 1000 mm / s; the scanning strategy is a stripe pattern; and the interlayer deflection angle is 67°. The aging process is 600℃ / 1 h. Other steps are the same as in Example 1.

[0062] The electrical and mechanical properties of the Cr2Nb / Cu composite material prepared in Example 2 were tested, and its conductivity was found to be 65% IACS and its tensile strength was 660 MPa.

[0063] Example 3

[0064] In this embodiment, in step 2, 10 wt.% Cu-Cr powder, 1.5 wt.% Nb powder, 15 wt.% Cu powder with a particle size of 1-2 μm, and 73.5 wt.% Cu powder with a particle size of 15-45 μm are weighed out by weight. In step 5, the printing process uses a laser power of 430 W; a laser scanning rate of 700 mm / s; a single-layer printing thickness of 30 μm; and a repetitive printing process with a laser power of 360 W; a laser scanning rate of 1500 mm / s; a stripe scanning strategy; and an interlayer deflection angle of 67°. The aging process is 450℃ / 1 h. Other steps are the same as in embodiments 1 and 2.

[0065] The electrical and mechanical properties of the Cr2Nb / Cu composite material prepared in Example 3 were tested, and its conductivity was found to be 73.8% IACS and its tensile strength was 581.8 MPa.

[0066] Example 4

[0067] In this embodiment, in step 2, 25 wt.% Cu-Cr powder, 3.75 wt.% Nb powder, 10 wt.% Cu powder with a particle size of 1-2 μm, and 61.25 wt.% Cu powder with a particle size of 15-45 μm are weighed out according to weight. In step 5, the printing process uses a laser power of 440 W; a laser scanning rate of 700 mm / s; and a single-layer printing thickness of 25 μm. For the repetitive printing process, the laser power is 370 W; the laser scanning rate is 1300 mm / s; the scanning strategy is a stripe pattern; and the interlayer deflection angle is 67°. The aging process is 500℃ / 3 h. Other steps are the same as in embodiments 1, 2, and 3.

[0068] The electrical and mechanical properties of the Cr2Nb / Cu prepared in Example 4 were tested, and its conductivity was found to be 63% IACS and its tensile strength was 665 MPa.

[0069] Example 5

[0070] In this embodiment, in step 2, 40 wt.% Cu-Cr powder, 6 wt.% Nb powder, 10 wt.% Cu powder with a particle size of 1-2 μm, and 44 wt.% Cu powder with a particle size of 15-45 μm are weighed out by weight. In step 5, the printing process uses a laser power of 430 W; a laser scanning rate of 600 mm / s; and a single-layer printing thickness of 25 μm. For the repetitive printing process, the laser power is 380 W; the laser scanning rate is 1000 mm / s; the scanning strategy is a stripe pattern; and the interlayer deflection angle is 67°. The aging process is 600℃ / 3 h. Other steps are the same as in embodiments 1, 2, 3, and 4.

[0071] The electrical and mechanical properties of the Cr2Nb / Cu composite material prepared in Example 5 were tested, and its conductivity was found to be 60% IACS and its tensile strength was 650 MPa.

[0072] Example 6

[0073] In this embodiment, in step 2, 10 wt.% Cu-Cr powder, 1.5 wt.% Nb powder, 15 wt.% Cu powder with a particle size of 1-2 μm, and 73.5 wt.% Cu powder with a particle size of 15-45 μm are weighed out by weight. In step 5, the printing process uses a laser power of 440 W; a laser scanning rate of 600 mm / s; and a single-layer printing thickness of 25 μm. For the repetitive printing process, the laser power is 360 W; the laser scanning rate is 1500 mm / s; the scanning strategy is a stripe pattern; and the interlayer deflection angle is 67°. The aging process is 500℃ / 3 h. Other steps are the same as in embodiments 1, 2, 3, 4, and 5.

[0074] The electrical and mechanical properties of the Cr2Nb / Cu composite material prepared in Example 6 were tested, and its conductivity was found to be 75.4% IACS and its tensile strength was 560.3 MPa.

[0075] This invention uses self-made Cu-Cr alloy powder, Nb powder, and Cu powder of specific compositions as raw materials. Through a designed powder mixing process and specific printing methods and parameters, a finely dispersed Cr2Nb / Cu composite material with a reinforcing phase is successfully prepared via in-situ reaction. This solves the problems of high cost and limited availability of Cr2Nb / Cu composite material powder in SLM (Self-Made Molding Machine). It provides a solution for Cr2Nb / Cu composite materials used in the combustion chamber lining of integrated rocket engines.

Claims

1. A method for preparing Cr2Nb / Cu composite materials by laser selective melting in situ reaction, characterized in that: Specifically, the steps include the following: Step 1: Weigh out Cu-Cr alloy powder, Nb powder, and Cu powder according to the specified proportions. In Step 1, weigh out 10-40 wt.% Cu-Cr alloy powder, 1.5-6 wt.% Nb powder, 10-15 wt.% Cu powder with a particle size of 1-2 μm, and 39-73.5 wt.% Cu powder with a particle size of 15-45 μm, respectively, by weight percentage. In Step 1, the density of both Cu-Cr alloy powder and Nb powder is 8.57 g / cm³. 3 The density difference between Cu-Cr alloy powder, Nb powder, and Cu powder is within 0.04%. Cu-Cr alloy powder with a particle size of 20-53μm is selected, and Nb powder with a particle size of 20-53μm, Cu powder with a particle size of 1-2μm, and Cu powder with a particle size of 15-45μm are also selected. Step 2 involves mixing Cu-Cr alloy powder with Nb powder, then adding Cu powder and mixing again, followed by drying the resulting mixed powder. The specific process of step 2 is as follows: First, Cu-Cr alloy powder and Nb powder are mixed. Cu powder with a particle size of 15-45μm is divided into several parts. One part is added at a time and mixed with Cu-Cr alloy powder for 2-4 hours. Finally, Cu powder with a particle size of 1-2μm is added and mixed for 6-8 hours to obtain mixed powder. The mixed powder is then heated in a vacuum chamber at a temperature of 80-150℃. Step 3: Construct the specimen model for the 3D printing equipment and import the constructed specimen model into the 3D printing equipment; the specific process of step 3 is as follows: Draw a rectangular 3D model and import it into slicing software for 2D slicing with a single layer thickness of 25-30μm. Set the printing order and generate a .STL file to obtain the specimen model that the 3D printing equipment can read. Import the completed specimen model into the 3D printing equipment. Step 4: The dried powder is loaded into a 3D printing device for printing to obtain a deposited Cr2Nb / Cu composite material; the specific process of step 4 is as follows: Step 4.1: Load the dried powder into the powder supply chamber of the 3D printing equipment, close the chamber door and perform gas washing. Introduce argon gas to remove the oxygen from the molding chamber. After the gas washing is completed, start the substrate preheating. After heating to the preheating temperature, turn on the fan. Step 4.2: Before printing, a layer of powder is pre-laid on the substrate for scanning and melting. First, a laser with a power of 430-450W is used for melting, but powder layering is not continued. Then, a laser with a power of 360-380W is used for melting again. After repeated laser scanning, another layer of powder is laid, until printing is complete, finally obtaining the deposited Cr2Nb / Cu composite material. In step 4.2, the initial printing process is: laser scanning rate 600-700mm / s; single-layer printing thickness 25-30μm; the subsequent printing process is: laser scanning rate 1000-1500mm / s; scanning method is stripe pattern. Step 5: Heat-treat the deposited Cr2Nb / Cu composite material to obtain the Cr2Nb / Cu composite material. The specific process of step 5 is as follows: heat the sample in a muffle furnace until the temperature reaches the preset temperature, then place the sample in the furnace for aging treatment. After the aging time is reached, cool the sample to room temperature by air cooling. The aging temperature is 450-600℃ and the aging time is 1-5h.

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