A method for preparing high temperature alloy powder for additive manufacturing

Abstract

The present invention relates to the field of additive manufacturing technology, and specifically to a method for preparing a high-temperature alloy powder for additive manufacturing. The method for preparing a high-temperature alloy powder for additive manufacturing of the present invention comprises the following steps: (1) preparing doped Al2O3 powder, (2) preparing modified Al2O3 powder, (3) preparing composite alloy ingots by melting, (4) forging, and (5) preparing powder by plasma electrode atomization. The high-temperature alloy powder for additive manufacturing of the present invention has excellent sphericity and low oxygen content, which can meet the basic requirements of additive manufacturing for powder, and the printed parts obtained by printing have excellent microhardness. Most importantly, the printed parts prepared by using the high-temperature alloy powder for additive manufacturing of the present invention still have good tensile strength and excellent plasticity under high temperature conditions, and have broad application prospects in the field of additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for preparing high-temperature alloy powder for additive manufacturing. Background Art

[0002] Laser Additive Manufacturing (LAM) technology is a layer-by-layer manufacturing technology based on 3D digital model files. It is an advanced manufacturing technology that can manufacture parts or products of any complex shape. This method of "layered manufacturing and layer-by-layer stacking" using lasers reduces the difficulty of processing to the greatest extent, converting one or more complex 3D processing processes into a 2D processing process, also known as dimensionality reduction manufacturing.

[0003] High temperature resistant titanium alloy is a titanium alloy that still has good performance under high temperature conditions. Due to its good thermal strength and high specific strength, it greatly reduces the weight while ensuring the strength of the material. It is widely used in parts such as aircraft blades and engines, and has become one of the most popular materials in the aerospace field. In the past few decades, titanium alloy aerospace parts have been the fastest growing field in the application of laser additive manufacturing technology.

[0004] Patent technical document CN201710963566.8 discloses a boron-containing titanium alloy powder for additive manufacturing and a preparation method thereof. The chemical composition of the powder is: Al 4.5-5.5%, V3.5-4.5%, B 0.05-1%, and the balance is Ti and unavoidable impurity elements. The ingredients are prepared according to the required alloy composition, titanium boride and raw materials such as sponge titanium are evenly mixed and pressed into electrodes, and then smelted into ingots by vacuum consumable smelting. After forging into rods, the titanium alloy powder is prepared by a crucible-free induction melting gas atomization method. By adding boron elements, the columnar crystals caused by the temperature gradient in the additive manufacturing process can be significantly weakened, and the grains can be refined and the mechanical properties of the material can be improved. However, it does not take into account that under long-term high temperature conditions, the mechanical properties of titanium alloys will drop significantly, affecting their use. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing high-temperature alloy powder for additive manufacturing, so as to solve the problem that printed parts prepared with traditional high-temperature alloy powder have poor mechanical properties under high temperature conditions.

[0006] Based on the above purpose, the present invention provides a method for preparing high temperature alloy powder for additive manufacturing, comprising the following steps:

[0007] S1: Mix borax decahydrate, lanthanum nitrate hexahydrate, aluminum isopropoxide and deionized water, adjust the pH to 4-5, react at 90-100°C for 18-20h, age, wash and calcine to obtain doped Al2O3 powder;

[0008] Preferably, the washing process in step S1 is carried out in cold water (20° C.), warm water (60° C.) and acetone in sequence.

[0009] Preferably, the calcination in step S1 is carried out by drying at 40° C. for 24 hours and then calcining at 1000° C. for 3 hours.

[0010] Preferably, the pH is adjusted in step S1 using nitric acid.

[0011] S2: placing the doped Al2O3 powder into a palladium nitrate solution, impregnating, aging, drying, calcining, and grinding to obtain a modified Al2O3 powder;

[0012] Preferably, the drying temperature in step S2 is 100° C. and the drying time is 20-24 hours.

[0013] S3: in an argon atmosphere, uniformly mixing the titanium alloy powder and the modified Al2O3 powder, melting them, and cooling them to obtain a composite alloy ingot;

[0014] S4: forging the composite alloy ingot into a titanium alloy rod;

[0015] S5: Load the titanium alloy rod into the plasma rotating electrode atomization powder making equipment, introduce the mixed gas, perform atomization powder making and screening, and obtain the high temperature titanium alloy powder for additive manufacturing.

[0016] Preferably, the weight ratio of borax decahydrate, lanthanum nitrate hexahydrate, aluminum isopropoxide and deionized water in step S1 is 1-3:1-3:50-80:100-150.

[0017] Preferably, the particle size of the modified Al2O3 powder in step S2 is 100-500 nm.

[0018] Preferably, the dosage ratio of the doped Al2O3 powder and the palladium nitrate solution in step S2 is 10g:3-4ml.

[0019] Preferably, the palladium nitrate solution in step S2 is a 10 wt % palladium nitrate solution.

[0020] Preferably, the titanium alloy powder in step S3 is one of Ti55, Ti60 and Ti65, and has a particle size of 100-200 μm.

[0021] Preferably, the weight ratio of the titanium alloy powder to the modified Al2O3 powder in step S3 is 90-95:5-10.

[0022] Preferably, the diameter of the titanium alloy rod in step S4 is 70-90 mm.

[0023] Preferably, the mixed gas in step S5 is composed of argon and helium in a volume ratio of 2-3:1.

[0024] Preferably, the working parameters of the atomization powder making in step S5 are: the distance between the plasma gun and the electrode rod is 30-100 mm, the power is 105-125 kW, the atomization speed is 1.7-2.3 kg / min, and the pressure is 1.8-2.1 MPa.

[0025] Preferably, the melting temperature in step S3 is 2500-2600°C and the vacuum degree is 0.6×10 -3 MPa.

[0026] Preferably, the screening is performed using 270-mesh and 800-mesh sieves.

[0027] Furthermore, the present invention also provides a high-temperature alloy powder for additive manufacturing, and the high-temperature alloy powder for additive manufacturing is prepared by the above-mentioned method for preparing the high-temperature alloy powder for additive manufacturing.

[0028] Beneficial effects of the present invention:

[0029] The method for preparing high-temperature alloy powder for additive manufacturing of the present invention introduces a solid solution strengthening effect by adding lanthanum element into a titanium alloy matrix, thereby improving the mechanical properties of the titanium alloy.

[0030] The method for preparing high-temperature alloy powder for additive manufacturing of the present invention promotes grain refinement of the titanium alloy and improves tensile strength at high temperature by adding palladium element into the titanium alloy matrix.

[0031] The method for preparing high-temperature alloy powder for additive manufacturing of the present invention adds lanthanum and palladium elements to a titanium alloy matrix. The two elements have a synergistic effect and together enable the titanium alloy matrix to still maintain good mechanical properties under high temperature conditions. DETAILED DESCRIPTION

[0032] 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.

[0033] The properties of the raw materials used in the examples and comparative examples of the present invention are as follows: Ti65 powder, with a particle size of 150 μm; and modified Al2O3 powder, with a particle size of 300 nm.

[0034] Example 1: A method for preparing high-temperature alloy powder for additive manufacturing, the specific preparation steps are as follows:

[0035] (1) 1 g of borax decahydrate, 1 g of lanthanum nitrate hexahydrate, 50 g of aluminum isopropoxide and 100 g of deionized water were mixed, the pH was adjusted to 4.2, the mixture was reacted at 90°C for 18 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0036] (2) 10 g of doped Al2O3 powder was placed in 3 ml of 10 wt% palladium nitrate solution, impregnated, aged, dried at 100 °C for 20 h, calcined, and ground to obtain modified Al2O3 powder;

[0037] (3) In an argon atmosphere, 90 g Ti65 powder and 10 g modified Al2O3 powder were mixed evenly and heated at 2500 °C and a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0038] (4) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 70 mm;

[0039] (5) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 30 mm, the power is 105 kW, the atomization speed is 1.7 kg / min, and the pressure is 1.8 MPa.

[0040] Example 2: A method for preparing high-temperature alloy powder for additive manufacturing, the specific preparation steps are as follows:

[0041] (1) 2 g of borax decahydrate, 2 g of lanthanum nitrate hexahydrate, 65 g of aluminum isopropoxide and 125 g of deionized water were mixed, the pH was adjusted to 4.6, the mixture was reacted at 95°C for 19 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0042] (2) 10 g of doped Al2O3 powder was placed in 3.5 ml of 10 wt% palladium nitrate solution, impregnated, aged, dried at 100 °C for 22 h, calcined, and ground to obtain modified Al2O3 powder;

[0043] (3) In an argon atmosphere, 93 g Ti65 and 7 g modified Al2O3 powder were mixed evenly and heated at 2550 °C with a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0044] (4) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 80 mm;

[0045] (5) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 60 mm, the power is 115 kW, the atomization speed is 2 kg / min, and the pressure is 2 MPa.

[0046] Embodiment 3: A method for preparing high temperature alloy powder for additive manufacturing, the specific preparation steps are as follows:

[0047] (1) 2.5 g of borax decahydrate, 2.5 g of lanthanum nitrate hexahydrate, 70 g of aluminum isopropoxide and 140 g of deionized water were mixed, the pH was adjusted to 4.8, the mixture was reacted at 100°C for 20 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0048] (2) 10 g of doped Al2O3 powder was placed in 4 ml of 10 wt% palladium nitrate solution, impregnated, aged, dried at 100 °C for 24 h, calcined, and ground to obtain modified Al2O3 powder;

[0049] (3) In an argon atmosphere, 94 g Ti65 and 6 g modified Al2O3 powder were mixed evenly and heated at 2600 °C with a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0050] (4) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 90 mm;

[0051] (5) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 90 mm, the power is 120 kW, the atomization speed is 2.3 kg / min, and the pressure is 2.1 MPa.

[0052] Example 4: A method for preparing high-temperature alloy powder for additive manufacturing, the specific preparation steps are as follows:

[0053] (1) 3 g of borax decahydrate, 3 g of lanthanum nitrate hexahydrate, 80 g of aluminum isopropoxide and 150 g of deionized water were mixed, the pH was adjusted to 5, the mixture was reacted at 100 °C for 20 h, aged, washed with cold water (20 °C), washed with warm water (60 °C), washed with acetone, dried at 40 °C for 24 h, and calcined at 1000 °C for 3 h to obtain doped Al2O3 powder;

[0054] (2) 10 g of doped Al2O3 powder was placed in 4 ml of 10 wt% palladium nitrate solution, impregnated, aged, dried at 100 °C for 24 h, calcined, and ground to obtain modified Al2O3 powder;

[0055] (3) In an argon atmosphere, 95 g Ti65 and 5 g modified Al2O3 powder were mixed evenly and heated at 2550 °C with a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0056] (4) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 90 mm;

[0057] (5) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 100 mm, the power is 125 kW, the atomization speed is 2.3 kg / min, and the pressure is 1.8 MPa.

[0058] Comparative Example 1: A method for preparing high temperature alloy powder, the specific preparation steps are as follows:

[0059] (1) 2 g of borax decahydrate, 2 g of lanthanum nitrate hexahydrate, 65 g of aluminum isopropoxide and 125 g of deionized water were mixed, the pH was adjusted to 4.6, the mixture was reacted at 95°C for 19 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0060] (2) In an argon atmosphere, 93 g Ti65 and 7 g doped Al2O3 powder were mixed evenly and heated at 2550 °C with a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0061] (3) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 80 mm;

[0062] (4) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 60 mm, the power is 115 kW, the atomization speed is 2 kg / min, and the pressure is 2 MPa.

[0063] Comparative Example 2: A method for preparing high temperature alloy powder, the specific preparation steps are as follows:

[0064] (1) 2 g of borax decahydrate, 65 g of aluminum isopropoxide and 125 g of deionized water were mixed, the pH was adjusted to 4.6, the mixture was reacted at 95°C for 19 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0065] (2) 10 g of doped Al2O3 powder was placed in 3.5 ml of 10 wt% palladium nitrate solution, impregnated, aged, dried at 100 °C for 22 h, calcined, and ground to obtain modified Al2O3 powder;

[0066] (3) In an argon atmosphere, 93 g Ti65 and 7 g modified Al2O3 powder were mixed evenly and heated at 2550 °C with a vacuum degree of 0.6 × 10 -3 MPa environment, melting and cooling to obtain a composite alloy ingot;

[0067] (4) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 80 mm;

[0068] (5) The titanium alloy rod is loaded into the plasma rotating electrode atomization powder making equipment, and the mixed gas is introduced to perform atomization and powder making, and sieving to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53 μm; wherein, the distance between the ion gun and the electrode rod is 60 mm, the power is 115 kW, the atomization speed is 2 kg / min, and the pressure is 2 MPa.

[0069] Comparative Example 3: A method for preparing high temperature alloy powder, the specific preparation steps are as follows:

[0070] (1) 2 g of borax decahydrate, 65 g of aluminum isopropoxide and 125 g of deionized water were mixed, the pH was adjusted to 4.6, the mixture was reacted at 95°C for 19 h, aged, washed with cold water (20°C), washed with warm water (60°C), washed with acetone, dried at 40°C for 24 h, and calcined at 1000°C for 3 h to obtain doped Al2O3 powder;

[0071] (2) In an argon atmosphere, 93 g Ti65, 6.8 g doped Al2O3 powder, 0.1 g lanthanum and 0.1 g palladium were uniformly mixed, melted at 2550°C and a vacuum degree of 0.6×10-3 MPa, and cooled to obtain a composite alloy ingot;

[0072] (3) Forging the composite alloy ingot into a titanium alloy rod with a diameter of 80 mm;

[0073] (4) Load the titanium alloy rod into the plasma rotating electrode atomization powder making equipment, introduce the mixed gas, perform atomization powder making, and sieve to obtain high-temperature titanium alloy powder for additive manufacturing with a particle size of 15-53μm; wherein, the distance between the ion gun and the electrode rod is 60mm, the power is 115kW, the atomization speed is 2kg / min, and the pressure is 2MPa. Performance test

[0074] Sphericity: The powders obtained in the examples and comparative examples were tested according to GB / T16418-2008. The test results are shown in Table 1.

[0075] Oxygen content: The oxygen content of the powders obtained in the examples and comparative examples was tested according to GB / T 14265-2017. The test results are shown in Table 1.

[0076] The powders obtained in the embodiment and the comparative example were placed in a powder feeding device, and laser additive manufacturing was performed using a coaxial powder feeding method to form the powders. The main process was as follows: laser power 2400W, scanning rate 600mm / min, powder feeding rate 10g / min, spot diameter 2.8mm, overlap rate 50%, and the entire deposition process was carried out in an argon chamber to obtain the corresponding prints, which were then subjected to solution aging treatment and their performance was tested:

[0077] Microhardness: A Japanese FM-100 series microhardness tester was used. The test specimens were polished and polished using different types of sandpaper to remove processing marks and ensure that the upper and lower surfaces of the specimens were flat. The experimental load was 500 g and the holding time was 15 s. Twenty points were selected for measurement in each group of samples, and the maximum and minimum values ​​were removed. The average value was finally calculated as the microhardness of the group of samples. The test results are shown in Table 2.

[0078] Room temperature mechanical properties: A tensile testing machine of model SANS CMT 5305 was used, and a standard dog-bone tensile specimen was used with a sample thickness of 2 mm. Before the test, 120# sandpaper was used to grind off the wire cutting processing marks, and then different types of sandpaper were used to grind and polish to avoid scratches on the sample surface that would affect the room temperature tensile test results. The tensile speed of the tensile test was set to 0.1 mm / min. The test results are shown in Table 2.

[0079] High temperature mechanical properties: The experimental samples were subjected to a 650°C high temperature tensile test using a universal testing machine (AGXplus), with a holding time of 10 min and a tensile speed of 1.5 mm / min. The test results are shown in Table 2.

[0080]

[0081] From the data analysis, it can be seen from Table 1 that the preparation method of the high-temperature titanium alloy powder for additive manufacturing of the present invention has excellent sphericity and low oxygen content, which can meet the basic requirements of additive manufacturing for powder; it can be seen from Table 2 Examples 1-4 that the prints obtained from the high-temperature titanium alloy powder for additive manufacturing of the present invention have excellent microhardness, and its tensile strength can reach 1153MPa and its elongation can reach 8.73% at room temperature; most importantly, under high temperature conditions of 650°C, it has good tensile strength and excellent plasticity.

[0082] It can be seen from Table 2 Example 2 and Comparative Examples 1-2 that by adding lanthanum and palladium elements to the titanium alloy matrix, the mechanical properties of the printed parts are further improved, especially under high temperature conditions, the improvement is more obvious, and the influence of lanthanum and palladium elements on the mechanical properties of titanium alloys is higher than the influence under room temperature conditions. The reason may be: under high temperature conditions, on the one hand, lanthanum and palladium alloy elements are added to the titanium alloy to form a solid solution, and introduce a solid solution strengthening effect, which serves the purpose of increasing the dislocation density of the titanium alloy; on the other hand, the addition of lanthanum and palladium elements can also promote the grain refinement of the titanium alloy and improve the tensile strength at high temperature; at the same time, lanthanum and palladium elements have a certain synergistic effect, which jointly promotes the mechanical properties of the titanium alloy. It can be seen from Example 2 and Comparative Example 3 that by doping lanthanum and palladium elements, a composite powder is first formed with Al2O3 by impregnation. Then adding it to the titanium alloy matrix, the improvement of its mechanical properties is more obvious compared to directly adding lanthanum and palladium elements to the titanium alloy matrix.

[0083] 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 (including the claims) 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.

[0084] 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 high temperature alloy powder for additive manufacturing, characterized in that: The following steps are involved: S1: Mix borax decahydrate, lanthanum nitrate hexahydrate, aluminum isopropoxide and deionized water, adjust the pH to 4-5, react at 90-100°C for 18-20h, age, wash and calcine to obtain doped Al2O3 powder; S2: placing the doped Al2O3 powder into a palladium nitrate solution, impregnating, aging, drying, calcining, and grinding to obtain a modified Al2O3 powder; S3: in an argon atmosphere, uniformly mixing the titanium alloy powder and the modified Al2O3 powder, melting them, and cooling them to obtain a composite alloy ingot; S4: forging the composite alloy ingot into a titanium alloy rod; S5: loading the titanium alloy rod into the plasma rotating electrode atomization powder making equipment, introducing the mixed gas, atomizing and powdering, screening, and obtaining high-temperature titanium alloy powder for additive manufacturing; The weight ratio of borax decahydrate, lanthanum nitrate hexahydrate, aluminum isopropoxide and deionized water in step S1 is 1-3:1-3:50-80:100-150.

2. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The particle size of the modified Al2O3 powder in step S2 is 100-500nm.

3. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The titanium alloy powder in step S3 is one of Ti55, Ti60 and Ti65, and has a particle size of 100-200 μm.

4. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The weight ratio of the titanium alloy powder to the modified Al2O3 powder in step S3 is 90-95:5-10.

5. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The diameter of the titanium alloy rod in step S4 is 70-90 mm.

6. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The mixed gas in step S5 is composed of argon and helium in a volume ratio of 2-3:

1.

7. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The working parameters of the atomization powder making in step S5 are: the distance between the plasma gun and the electrode rod is 30-100 mm, the power is 105-125 kW, the atomization speed is 1.7-2.3 kg / min, and the pressure is 1.8-2.1 MPa.

8. The method for preparing high temperature alloy powder for additive manufacturing according to claim 1, characterized in that: The melting temperature in step S3 is 2500-2600°C and the vacuum degree is 0.6×10 -3 MPa.

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