Metal powder for additive manufacturing

Abstract

The present invention relates to the field of additive manufacturing technology, and specifically to a metal powder for additive manufacturing. The metal powder for additive manufacturing of the present invention comprises the following steps: preparing a composite powder; mixing a cobalt-based alloy powder, a composite powder and a chromium carbide powder, smelting and powdering, and screening to finally obtain the powder. The metal powder for additive manufacturing of the present invention has a powder fluidity of 20-30s / 50g, and the printed parts obtained by additive manufacturing have good hardness and room temperature friction resistance, and at a high temperature of 400°C, still have relatively excellent wear resistance, can be widely used in key components in aircraft engines, and provide important support for the reliability and life of the engine.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a metal powder for additive manufacturing. Background Art

[0002] Additive Manufacturing (AM), also known as 3D printing technology, is a manufacturing method that builds objects by stacking materials layer by layer. Compared with traditional subtractive manufacturing, additive manufacturing builds objects by adding materials layer by layer under the control of digital models, so it is also called "layer-by-layer manufacturing". Through additive manufacturing technology, alloys can be sprayed, melted or sintered in powder form to build the desired shape and structure layer by layer. This method can achieve complex internal structures and geometries, providing greater design freedom. In addition, additive manufacturing can also avoid multiple processing and connection processes in traditional manufacturing methods, improve manufacturing efficiency and reduce costs.

[0003] Patent technology document CN202211162058.7 discloses a Cr3C2 particle reinforced laser selective melting cobalt-based alloy and its preparation method. The invention mechanically mixes CoCrMo powder with Cr3C2 reinforced powder; additive manufacturing is performed after screening. The final printed part has a tensile strength of ≥1500MPa, a yield strength of ≥1100MPa, and a microhardness of ≥500HV at room temperature. After high-temperature oxidation at 950℃ for 40h, the unit area weight gain of the alloy is less than 0.954mg / cm 2 However, it ignores the fact that under high temperature conditions, the oxide film on the surface will fall off after friction, which greatly reduces its wear resistance in high temperature environment. Summary of the invention

[0004] In view of this, an object of the present invention is to propose a metal powder for additive manufacturing, so as to provide a metal powder for additive manufacturing, wherein the alloy obtained by additive manufacturing of the powder still has good wear resistance at 400°C.

[0005] Based on the above purpose, the present invention provides a method for preparing metal powder for additive manufacturing, comprising the following steps:

[0006] S1: mixing and grinding doped graphene and carbon powder to obtain composite powder;

[0007] Preferably, in step S1, the weight ratio of the doped graphene to the carbon powder is 1-5:95-99.

[0008] S2: mixing the cobalt-based alloy powder, the composite powder and the chromium carbide powder, vacuum melting, gas atomizing and sieving to obtain metal powder for additive manufacturing;

[0009] Preferably, the doped graphene in step S1 is nitrogen and boron co-doped graphene.

[0010] Preferably, the particle size of the carbon powder in step S1 is 20-40 nm.

[0011] Preferably, the grinding speed in step S1 is 500-700 rpm and the time is 8-12 h.

[0012] Preferably, the cobalt-based alloy powder in step S2 is Co-Mo-Cr-Si alloy powder with a particle size of 30-80 μm.

[0013] Preferably, the particle size of the chromium carbide in step S2 is 5-20 μm.

[0014] Preferably, the vacuum melting temperature in step S2 is 1600-1650°C, and the vacuum degree is 1-1.3×10 -2 Pa.

[0015] Preferably, the gas flow for atomization powder making in step S2 is high-purity argon gas with a pressure of 2.5-3.5 MPa.

[0016] Preferably, in step S2, the weight ratio of the cobalt-based alloy powder, the composite powder and the chromium carbide powder is 90-95:1-2:4-8.

[0017] Preferably, the screening in step S2 is performed using 270-mesh and 800-mesh sieves.

[0018] Furthermore, the present invention also provides a metal powder for additive manufacturing, which is prepared by a method for preparing a metal powder for additive manufacturing.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention introduces two different carbon elements by mixing graphene with carbon powder and then smelting the mixed mixture with cobalt-based alloy powder. In the additive process, a reinforcing phase is introduced, so that the hardness and wear resistance of the final alloy are improved. In addition, the wear resistance of the alloy at 400°C is also improved to a certain extent.

[0021] (2) The present invention introduces C, N, and B elements by mixing doped graphene with carbon powder and then smelting the mixed mixture with cobalt-based alloy powder. During the additive process, a variety of reinforcing phases are generated, thereby improving the hardness and wear resistance of the alloy. More importantly, during the additive process, the new reinforcing phases generated reduce the thermal expansion coefficient between the oxide film generated at high temperature and the matrix, preventing the oxide film from falling off due to wear, thereby enabling it to still have excellent wear resistance at a high temperature of 400°C. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0023] The properties or sources of the raw materials used in the examples and comparative examples of the present invention are as follows:

[0024] Co-Mo-Cr-Si alloy powder, particle size 50μm, composition as follows:

[0025]

[0026] Nitrogen and boron co-doped graphene was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with the catalog number B487614;

[0027] The particle size of the carbon powder is 30 nm.

[0028] Example 1: A metal powder for additive manufacturing, the specific preparation steps are as follows:

[0029] (1) Mix 1 g of nitrogen and boron co-doped graphene and 99 g of carbon powder and grind them at 500 rpm for 8 h to obtain composite powder;

[0030] (2) Mix 90 g of Co-Mo-Cr-Si alloy powder, 2 g of composite powder and 8 g of chromium carbide powder in a vacuum of 1 × 10 -2 The metal powder was smelted at 2.5 MPa and 1600°C and kept warm for 1 hour, then powdered at 2.5 MPa and high-purity argon, and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0031] Example 2: A metal powder for additive manufacturing, the specific preparation steps are as follows:

[0032] (1) Mix 3 g of nitrogen and boron co-doped graphene and 97 g of carbon powder and grind them at 600 rpm for 10 h to obtain composite powder;

[0033] (2) 92.5 g of Co-Mo-Cr-Si alloy powder, 1.5 g of composite powder and 6 g of chromium carbide powder were mixed and vacuumed to 1.2 × 10 -2 The metal powder was smelted at 3 MPa and 1625°C and kept warm for 2 h. It was then powdered at 3 MPa and high-purity argon and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0034] Embodiment 3: A metal powder for additive manufacturing, the specific preparation steps are as follows:

[0035] (1) 4 g of nitrogen-boron co-doped graphene and 96 g of carbon powder were mixed and ground at 700 rpm for 12 h to obtain a composite powder;

[0036] (2) 94 g of Co-Mo-Cr-Si alloy powder, 2 g of composite powder and 4 g of chromium carbide powder were mixed and vacuumed to 1.2 × 10 -2 The metal powder was smelted at 3.3 MPa and 1640°C and kept warm for 2 h. It was then powdered at 3.3 MPa and high-purity argon and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0037] Example 4: A metal powder for additive manufacturing, the specific preparation steps are as follows:

[0038] (1) Mix 5 g of nitrogen and boron co-doped graphene and 95 g of carbon powder and grind them at 700 rpm for 12 h to obtain composite powder;

[0039] (2) 95 g of Co-Mo-Cr-Si alloy powder, 1 g of composite powder and 4 g of chromium carbide powder were mixed and vacuumed to 1.3 × 10 -2 The metal powder was smelted at 3.5 MPa and 1650°C and kept warm for 2 h. It was then powdered at 3.5 MPa and high-purity argon and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0040] Comparative Example 1: A metal powder, the specific preparation steps are as follows:

[0041] (1) Mix 3 g of graphene and 97 g of carbon powder and grind at 600 rpm for 10 h to obtain composite powder;

[0042] (2) 92.5 g of Co-Mo-Cr-Si alloy powder, 1.5 g of composite powder and 6 g of chromium carbide powder were mixed and vacuumed to 1.2 × 10 -2 The metal powder was smelted at 3 MPa and 1625°C and kept warm for 2 h. It was then powdered at 3 MPa and high-purity argon and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0043] Comparative Example 2: A metal powder, the specific preparation steps are as follows:

[0044] 92.5 g of Co-Mo-Cr-Si alloy powder, 1.5 g of carbon powder and 6 g of chromium carbide powder were mixed in a vacuum of 1.2 × 10 -2 The metal powder was smelted at 3 MPa and 1625°C and kept warm for 2 h. It was then powdered at 3 MPa and high-purity argon and sieved with 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0045] Comparative Example 3: A metal powder, the specific preparation steps are as follows:

[0046] The Co-Mo-Cr-Si alloy powder is ball-milled, cooled, and sieved using 270-mesh and 800-mesh sieves to obtain metal powder for additive manufacturing.

[0047] Performance Testing

[0048] Powder fluidity: The powders obtained in the examples and comparative examples were tested according to GB / T 1482-2010 Determination of metal powder fluidity - Standard funnel method (Hall rheometer). The test results are shown in Table 1.

[0049] The powders obtained in the embodiment and the comparative example were placed in a vacuum drying furnace at 100°C for drying, 45 steel with a size of 150mm×150mm×30mm was used as a substrate, the substrate was preheated to 500°C, and laser additive manufacturing was performed with a laser power of 1300W, a scanning speed of 5mm / s, a powder feeding rate of 15g / min, and a protector flow rate of 15L / min. Subsequently, heat treatment (1250°C / 1h AC+900°C / 4h FC) was performed to finally obtain the prints corresponding to the embodiment and the comparative example, and the performance of the prints was tested.

[0050] Microhardness: The microhardness of the printed parts was measured using a Vickers microhardness tester (model: HXD-1000TMC / LCD). The printed parts were ground and polished before the experiment. The load was 300g and the holding time was 10s. The hardness of 10 points on the same sample was measured and the average value was taken. The test results are shown in Table 2.

[0051] Friction performance test: The wear resistance test was conducted using a HT-1000 ball-disc high-temperature friction and wear testing machine. The test load was 4N, the wear time was 60min, the test temperature was 25°C and 400°C, and the wear piece was a Si3N4 ceramic ball. Before the experiment, the printed part was polished with sandpaper with a mesh size of 1000#, and then the printed part was placed in anhydrous ethanol and cleaned with an ultrasonic oscillator and dried. The mass of the printed part (M1) was recorded before the friction and wear experiment. After the experiment, the printed part was cleaned and dried again, and its new mass (M2) was recorded again. The wear resistance of the printed part was judged by calculating and comparing the mass loss of the printed part before and after the experiment. Under the same experimental conditions, the smaller the wear weight loss of the printed part, the better the wear resistance. The test results are shown in Table 2.

[0052]

[0053] Data analysis: It can be seen from Table 1 that the metal powder for additive manufacturing of the present invention has a Hall flow rate maintained between 20-30s / 50g, has good fluidity and sphericity, and can meet the requirements of additive manufacturing for powder fluidity and sphericity.

[0054] It can be seen from Examples 1-4 in Table 2 that the printed parts obtained by additive manufacturing of the metal powder of the present invention have good hardness and wear resistance, especially at 400°C, the wear resistance is very excellent and can meet the use of the printed parts in high temperature environments.

[0055] It can be seen from Example 2 and Comparative Examples 2 and 3 in Table 2 that the present invention introduces two different carbon elements by mixing graphene with carbon powder and then smelting the mixed powder with cobalt-based alloy powder. In the additive process, a reinforcing phase is introduced, so that the hardness and wear resistance of the final alloy are improved, and the wear resistance of the alloy at 400°C is also improved to a certain extent.

[0056] It can be seen from Example 2 and Comparative Examples 1 and 3 in Table 2 that the present invention introduces C, N, and B elements by mixing doped graphene with carbon powder and then smelting the mixed powder with cobalt-based alloy powder. During the additive process, a variety of reinforcing phases are generated, so that the hardness and wear resistance of the alloy are improved. More importantly, during the additive process, the new reinforcing phases generated reduce the thermal expansion coefficient between the oxide film generated at high temperature and the substrate, preventing the oxide film from falling off due to wear, thereby making it still have excellent wear resistance at a high temperature of 400°C.

[0057] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0058] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing metal powder for additive manufacturing, characterized in that: The following steps are involved: S1: mixing and grinding doped graphene and carbon powder to obtain composite powder; S2: mixing the cobalt-based alloy powder, the composite powder and the chromium carbide powder, vacuum melting, gas atomizing and sieving to obtain metal powder for additive manufacturing; The doped graphene in step S1 is nitrogen and boron co-doped graphene; The weight ratio of the doped graphene to the carbon powder in step S1 is 1-5:95-99; The weight ratio of the cobalt-based alloy powder, the composite powder and the chromium carbide powder in step S2 is 90-95:1-2:4-8; The cobalt-based alloy powder in step S2 is Co-Mo-Cr-Si alloy powder with a particle size of 30-80 μm.

2. The method for preparing metal powder for additive manufacturing according to claim 1, characterized in that: The particle size of the carbon powder in step S1 is 20-40 nm.

3. The method for preparing metal powder for additive manufacturing according to claim 1, characterized in that: The grinding speed in step S1 is 500-700 rpm, and the grinding time is 8-12 hours.

4. The method for preparing metal powder for additive manufacturing according to claim 1, characterized in that: The particle size of the chromium carbide in step S2 is 5-20 μm.

5. The method for preparing metal powder for additive manufacturing according to claim 1, characterized in that: The screening in step S2 is performed by using 270 mesh and 800 mesh sieves.

6. A metal powder for additive manufacturing, characterized in that: The metal powder for additive manufacturing is prepared by the method for preparing the metal powder for additive manufacturing according to any one of claims 1 to 5.

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