An additive manufacturing method for a titanium matrix composite material

Abstract

The present invention provides a method for additive manufacturing of a titanium matrix composite material, comprising the following steps: S1. Put titanium powder and reinforcing phase raw materials into the ball milling tank of a planetary ball mill, charge and discharge argon gas into the ball milling tank 3 times, and then ball mill for 3-5 h to obtain a mixed powder; S2. Place the mixed powder obtained in step S1 in a vacuum drying oven and vacuum dry for 3-6 h to obtain a dried powder; S3. Put the dried powder and binder obtained in step S2 into a 3D printer, spray the binder and perform 3D printing to form a 3D printed component; S4. Subject the 3D printed component obtained in step S3 to vacuum debinding for 0.5-1.5 h to obtain a debound 3D printed component; S5. Place the debound 3D printed component obtained in step S4 in a vacuum furnace, perform vacuum sintering and then cool with the furnace to room temperature to obtain a titanium matrix composite material. During the process of the present invention, no support needs to be added, and cracking will not be caused due to thermal stress. The reinforcing phase of the obtained titanium matrix composite material is distributed in a quasi-continuous network shape and has good mechanical properties.

Description

Technical Field

[0001] The present invention relates to an additive manufacturing method, and particularly to an additive manufacturing method for titanium matrix composites. Background Art

[0002] Discontinuous reinforced titanium matrix composites have excellent specific strength, specific stiffness, and isotropy, and have broad application prospects. In particular, titanium matrix composites with a reticular structure distribution of the reinforcement phase have excellent strength and plasticity. Additive manufacturing technology is a technology that realizes net-shape forming of components by stacking materials layer by layer. Preparing titanium matrix composite components using additive manufacturing technology is one of the important directions for future development.

[0003] The additive manufacturing of titanium matrix composites mainly currently uses two methods: laser powder bed fusion and laser directed energy deposition. The specific forms are divided into the following three aspects:

[0004] (1) Mix titanium metal powder and reinforcement powder evenly so that the surface of the metal powder adheres to the reinforcement phase powder, and then use laser powder bed technology or powder-fed laser directed energy deposition technology to form. On the one hand, there are relatively large thermal stresses in these two additive manufacturing technologies themselves. On the other hand, an in-situ reaction will occur between the metal powder and the ceramic powder and heat will be released, further increasing the thermal stress and increasing the risk of cracking during the manufacturing process.

[0005] (2) First, prepare a titanium matrix composite ingot or bar by a casting method or a powder metallurgy method, and then prepare a titanium matrix composite by a gas atomization method or a rotating electrode method. Although this method can reduce the thermal stress during the manufacturing process, the process is complex, the time cycle is long, and the preparation cost is high.

[0006] (3) Use two powder feeding systems to feed titanium alloy powder and ceramic powder into the molten pool according to a preset composition during the printing process. However, due to the lack of pre-mixing, the reinforcement phase is prone to segregation during the printing process, and defects are likely to appear inside, resulting in poor performance.

[0007] In addition, during the additive manufacturing process using the above methods, the titanium alloy material often melts completely, so it is difficult to design the microstructure at the microscale. In addition, when manufacturing many complex structures, complex supports need to be added to the structure to assist the additive manufacturing process, which makes it difficult for the existing technology to prepare some components with hollow structures. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an additive manufacturing method for titanium matrix composites, which does not require adding supports during the process, does not cause cracking due to thermal stress, and the reinforcement phase of the obtained titanium matrix composite is in a quasi-continuous reticular distribution and has good mechanical properties.

[0009] To solve the above technical problems, the technical solution of the present invention is as follows:

[0010] An additive manufacturing method for a titanium matrix composite material, comprising the following steps:

[0011] S1. Put titanium powder and reinforcing phase raw materials into the ball milling tank of a planetary ball mill, charge and discharge argon gas into the ball milling tank 3 times, and then ball mill for 3 - 5 h to obtain a mixed powder;

[0012] S2. Place the mixed powder obtained in step S1 in a vacuum drying oven, and vacuum dry for 3 - 6 h to obtain a dried powder;

[0013] S3. Put the dried powder and binder obtained in step S2 into a 3D printer, spray the binder and perform 3D printing to form a 3D printed component;

[0014] S4. Vacuum degrease the 3D printed component obtained in step S3 for 0.5 - 1.5 h to obtain a degreased 3D printed component;

[0015] S5. Place the degreased 3D printed component obtained in step S4 in a vacuum furnace, perform vacuum sintering, and then cool with the furnace to room temperature to obtain a titanium matrix composite material.

[0016] Furthermore, in step S1 of the present invention, the weight ratio of titanium powder to reinforcing phase raw materials is 1:(0.02 - 0.05); the titanium powder is composed of small - particle - size titanium powder and large - particle - size titanium powder with a weight ratio of 4:6 to 7:3. Among them, the particle size of the small - particle - size titanium powder is 1 - 15 μm, and the particle size of the large - particle - size titanium powder is 35 - 180 μm; the reinforcing phase raw material is one of B4C, TiB2 or graphite flakes with a particle size of 0.2 - 3 μm. The main purpose of selecting two different particle - size titanium powders is to make the structure show a network structure distribution. And if only large - particle - size titanium powder is selected, it is difficult to ensure the density during the subsequent sintering process; the reinforcing phase raw material is selected as a powder that can undergo an in - situ reaction with titanium during the sintering process, aiming to introduce a ceramic reinforcing phase.

[0017] Furthermore, in step S1 of the present invention, the ball - milling speed is 180 - 240 rpm, the ball - to - material ratio is 1:1 to 5:1, and the materials of the ball milling tank and grinding balls are both stainless steel. The main purpose of ball milling is to mix titanium powder and reinforcing phase powder with different particle sizes evenly.

[0018] Furthermore, in step S2 of the present invention, the temperature of vacuum drying is 110 - 150 °C. The purpose of vacuum drying is to prevent the powder from getting damp and improve the powder fluidity.

[0019] Further, in step S3 of the present invention, the binder is composed of ethylene glycol monomethyl ether, diethylene glycol, and water with a volume ratio of 1:2:7. The layer thickness during the spraying of the binder is 0.05 - 0.25 mm. The main purpose of step S3 is to form the material. The main steps of jet 3D printing are as follows: First, the drawn three-dimensional model is layered by layer software with a layer thickness of 0.05 - 0.25 mm; a certain thickness of dry powder in the powder bed is evenly spread in the forming chamber by a doctor blade with a thickness of 0.05 - 0.25 mm; then the binder is dropped into the powder bed according to the layered shape and waits for the binder to penetrate to the layer thickness before printing the next layer.

[0020] Further, in step S4 of the present invention, the temperature of vacuum degreasing is 350 - 550 °C, and the vacuum degree is 10 -5 -10 -2 Pa. The main purpose of step S4 is to remove the binder in the 3D printed component.

[0021] Further, in step S5 of the present invention, the vacuum degree of vacuum sintering is 10 -5 -10 -2 Pa, and the heating rate is 10 °C / min; the process of vacuum sintering is as follows: heating from room temperature to 400 °C and then holding for 1 - 2 h, and then heating to 1250 - 1500 °C and holding for 4 - 8 h. The main purpose of step S5 is to sinter the powder into a dense bulk material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The present invention uses a binder to bond metal powders to manufacture a model shape. The temperature during the bonding process is much lower than the melting point of the metal, and the metal does not melt during the additive manufacturing process. Therefore, the thermal stress is low, no thermal cracks are generated during the manufacturing process, and the forming rate is high.

[0024] 2) The present invention hardly needs to use supports to assist the additive manufacturing process, omitting the complex support design steps before printing and the support removal process after printing. The process is simple, and at the same time, some hollow structures that are difficult to achieve by other additive manufacturing technologies can be prepared.

[0025] 3) In the method of the present invention, the composition, structure, and properties of the material are all easy to control the structure. Since the powder does not melt during the additive process, the composition of the composite material can be controlled by the composition of the metal powder and the reinforcing phase, and the parameters of the network structure can be controlled by the particle size of the metal powder and the ratio of coarse powder to fine powder, thereby controlling the properties of the material to meet the use requirements.

[0026] 4) The present invention realizes a titanium matrix composite material with a tissue reticular structure by regulating the powder ratio and manufacturing process: The ball milling energy used in the present invention is relatively low, which can ensure the uniform mixing of titanium powders with different particle sizes while the ceramic phase wraps around the surface of spherical titanium powders; during the additive manufacturing process, only the binder adheres to the mixed powders, and the sintering process is a solid-phase sintering. The added ceramic powder reacts in-situ with titanium to generate a reinforcing phase, and this step is an exothermic reaction that is beneficial to densification; the core of the larger-sized Ti powders does not participate in the in-situ reaction process, so there is almost no ceramic reinforcing phase, thereby forming a reinforcing-phase depletion zone, and the other regions opposite to it are reinforcing-phase enrichment zones with a higher content of the reinforcing phase. Therefore, only by adopting an appropriate powder composition (including powder particle size, the ratio of powders with different particle sizes, the type and content of the reinforcing phase) and sintering process can the reinforcing phase be distributed in a reticular structure and the final sintered material have a high density (using only very fine titanium powders with small particle sizes has a high cost and cannot design the tissue, while using only large-sized titanium powders is difficult to densify).

[0027] 5) The present invention does not use a laser and precision optical devices, so the equipment used has a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings:

[0029] Figure 1 It is the metallographic diagram of the titanium matrix composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be described in detail below with reference to specific embodiments. Here, the illustrative embodiments of the present invention and the description are used to explain the present invention, but do not limit the present invention.

[0031] Example 1

[0032] The titanium matrix composite material is additively manufactured according to the following steps:

[0033] S1. Put 400 g of small-sized titanium powder with a particle size of 8 μm, 600 g of large-sized titanium powder with a particle size of 50 μm, 20 g of TiB2 with a particle size of 2.5 μm, and 3.3 g of graphite flakes with a particle size of 2.5 μm into the ball milling tank of a planetary ball mill. After filling and discharging argon gas in the ball milling tank 3 times, ball mill for 5 h to obtain a mixed powder. The ball milling speed is 200 rpm, the ball-to-material ratio is 2:1, and the materials of the ball milling tank and grinding balls are both stainless steel;

[0034] S2. Place the mixed powder obtained in step S1 in a vacuum drying oven and vacuum dry it at 120 °C for 4 h to obtain a dried powder;

[0035] S3. Place the dry powder obtained in step S2 and the binder in a 3D printer, and perform 3D printing by jetting the binder to obtain a 3D printed component with a length of 10 mm, a width of 10 mm, and a height of 9.5 mm. The binder is composed of ethylene glycol monomethyl ether, diethylene glycol, and water with a volume ratio of 1:2:7. The layer thickness during binder jetting is 0.1 mm. The main steps of jet 3D printing are as follows: First, use slicing software to slice the drawn 3D model with a layer thickness of 0.1 mm; use a squeegee to evenly spread a certain thickness of dry powder in the powder bed in the forming chamber with a thickness of 0.1 mm; then drop the binder into the powder bed according to the sliced shape, and wait for the binder to penetrate to the layer thickness before printing the next layer;

[0036] S4. Place the 3D printed component obtained in step S3 in a vacuum degreasing process at 400 °C and 10 -2 Pa vacuum for 1 h to obtain a degreased 3D printed component;

[0037] S5. Place the degreased 3D printed component obtained in step S4 in a vacuum furnace, perform vacuum sintering and then cool it to room temperature with the furnace to obtain a titanium matrix composite with a length of 8 mm, a width of 8 mm, and a height of 8 mm. The vacuum degree of vacuum sintering is 10 -2 Pa, and the heating rate is 10 °C / min. The process of vacuum sintering is as follows: Heat from room temperature to 400 °C and hold for 1.5 h, then heat to 1250 °C and hold for 4 h.

[0038] During the sintering process, in-situ reaction occurs between TiB2 and Ti to form fine TiB whiskers. The mass fraction of TiB calculated according to the mass fraction of TiB2 is 2.74 wt%. In-situ reaction occurs between graphite powder and Ti to form equiaxed Ti2C particles. The mass fraction of Ti2C generated calculated according to the content of added graphite flakes is 2.97 wt%. The sintered microstructure is distributed in a network shape, as Figure 1 shown. The material is divided into a reinforced phase depletion region and a reinforced phase enrichment region. The reinforced phase enrichment region forms a three-dimensional network structure. Taking the volume fraction of the reinforced phase per unit area as a reference, the region with a density lower than the overall density is the reinforced phase depletion region, and the region with a density higher than the overall density is the reinforced phase enrichment region. The reinforced phase depletion region accounts for 30%, and the reinforced enrichment region accounts for 70%. After sintering, the density of the titanium matrix composite is measured to be 96.5% by the image method.

[0039] Comparative Example 1

[0040] The difference from Example 1 is that large-sized titanium powder is not used in step S1, and the weight of small-sized titanium powder is 1000 g.

[0041] Comparative Example 2

[0042] The difference from Example 1 is that small-sized titanium powder is not used in step S1, and the weight of large-sized titanium powder is 1000 g.

[0043] Comparative Example 3

[0044] Cold-rolled pure titanium plate, and its preparation steps are as follows: Pure titanium (alloy grade is TA2) is obtained by vacuum consumable arc melting to get a blank. After hot forging the blank at 800 °C, a prism of 15 mm × 15 mm × 120 mm is cut off by wire cutting, and placed on a rolling mill for cold rolling to obtain a cold-rolled pure titanium plate, and the reduction of cold rolling is 50%.

[0045] Experimental Example: Hardness Test

[0046] The hardness test method refers to the national standard GB / T 4340.1-2024 "Metallic materials - Vickers hardness test - Part 1: Test method". The Vickers hardness of Example 1 and Comparative Examples 1-3 was measured respectively, and the applied load was 0.2452 N.

[0047] The test results are shown in Table 1:

[0048] Vickers hardness of the reinforcement phase depletion zone Vickers hardness of the reinforcement phase enrichment zone Overall Vickers hardness Example 1 356±32 490±64 400±78 Comparative Example 1 315±22 427±36 357±56 Comparative Example 2 - - 361±23 Comparative Example 3 - - 298±21

[0049] Table 1

[0050] It can be seen from Table 1 that the overall Vickers hardness of the titanium matrix composite prepared in Example 1 of the present invention is higher than that of Comparative Example 3, indicating that the introduction of the reinforcing phase brings excellent mechanical properties. The Vickers hardness of the reinforcing phase depletion zone, the Vickers hardness of the reinforcing phase enrichment zone, and the overall Vickers hardness of Comparative Example 1 are all lower than those of Example 1. In Comparative Example 2, the distribution of the reinforcing phase is relatively uniform, there is no depletion zone and enrichment zone, and the overall Vickers hardness is not as good as that of Example 1, indicating that using only small-sized titanium powder or large-sized titanium powder cannot achieve satisfactory results.

[0051] Example 2

[0052] The titanium matrix composite is additively manufactured according to the following steps:

[0053] S1. 700 g of small-sized titanium powder with a particle size of 1 μm, 300 g of large-sized titanium powder with a particle size of 180 μm, and 20 g of B4C with a particle size of 3 μm are put into the ball milling tank of a planetary ball mill. After filling and discharging argon gas in the ball milling tank 3 times, ball milling is carried out for 3 h to obtain a mixed powder. The ball milling speed is 240 rpm, the ball-to-material ratio is 1:1, and the materials of the ball milling tank and the grinding balls are both stainless steel;

[0054] S2. The mixed powder obtained in step S1 is placed in a vacuum drying oven and vacuum dried at 110 °C for 6 h to obtain a dried powder;

[0055] S3. Place the dry powder obtained in step S2 and the binder into a 3D printer, and perform 3D printing by spraying the binder to obtain a 3D printed component. The binder is composed of ethylene glycol monomethyl ether, diethylene glycol, and water with a volume ratio of 1:2:7. The layer thickness during the spraying of the binder is 0.25 mm. The main steps of the spraying 3D printing are as follows: First, perform layer slicing on the drawn 3D model through layer slicing software, with a layer thickness of 0.25 mm; use a squeegee to evenly spread a certain thickness of dry powder in the powder bed in the forming chamber, with a thickness of 0.25 mm; then drop the binder into the powder bed according to the shape after layer slicing, and wait for the binder to penetrate to the layer thickness before printing the next layer;

[0056] S4. Place the 3D printed component obtained in step S3 under a vacuum of 350 °C and 10 -5 Pa for 0.5 h for vacuum degreasing to obtain a degreased 3D printed component;

[0057] S5. Place the degreased 3D printed component obtained in step S4 into a vacuum furnace, and perform vacuum sintering and then cool it to room temperature with the furnace to obtain a titanium matrix composite. The vacuum degree of the vacuum sintering is 10 -5 Pa, and the heating rate is 10 °C / min. The process of the vacuum sintering is as follows: Heat from room temperature to 400 °C and hold for 1 h, then heat to 1400 °C and hold for 8 h.

[0058] Example 3

[0059] Additively manufacture a titanium matrix composite according to the following steps:

[0060] S1. Put 500 g of small-sized titanium powder with a particle size of 15 μm, 500 g of large-sized titanium powder with a particle size of 35 μm, and 50 g of TiB2 with a particle size of 0.2 μm into the ball milling tank of a planetary ball mill. After filling and discharging argon into the ball milling tank 3 times, perform ball milling for 4 h to obtain a mixed powder. The ball milling speed is 180 rpm, the ball-to-powder ratio is 5:1, and the materials of the ball milling tank and the grinding balls are both stainless steel;

[0061] S2. Place the mixed powder obtained in step S1 into a vacuum drying oven and perform vacuum drying at 150 °C for 3 h to obtain a dry powder;

[0062] S3. Place the dry powder obtained in step S2 and the binder into a 3D printer, and perform 3D printing by spraying the binder to obtain a 3D printed component. The binder is composed of ethylene glycol monomethyl ether, diethylene glycol, and water with a volume ratio of 1:2:7. The layer thickness during the spraying of the binder is 0.05 mm. The main steps of the spraying 3D printing are as follows: First, perform layer slicing on the drawn 3D model through layer slicing software, with a layer thickness of 0.05 mm; use a squeegee to evenly spread a certain thickness of dry powder in the powder bed in the forming chamber, with a thickness of 0.05 mm; then drop the binder into the powder bed according to the shape after layer slicing, and wait for the binder to penetrate to the layer thickness before printing the next layer;

[0063] S4. Heat the 3D printed component obtained in step S3 in a vacuum degreasing process at 550 °C and a vacuum degree of 10 -3 Pa for 1.5 h to obtain a degreased 3D printed component;

[0064] S5. Place the degreased 3D printed component obtained in step S4 in a vacuum furnace, and after vacuum sintering, cool it to room temperature with the furnace to obtain a titanium matrix composite. The vacuum degree of vacuum sintering is 10 -3 Pa, and the heating rate is 10 °C / min. The process of vacuum sintering is as follows: heat from room temperature to 400 °C and hold for 2 h, then heat to 1500 °C and hold for 6 h.

[0065] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for additive manufacturing of a titanium-based composite material, characterized in that: The following steps are involved: S1. Put titanium powder and reinforcing phase raw material into a ball mill of a planetary ball mill, fill and discharge argon gas into the ball mill 3 times, and then ball mill for 3-5 hours to obtain a mixed powder; the weight ratio of titanium powder to reinforcing phase raw material is 1:(0.02-0.05); the titanium powder is composed of small-particle titanium powder and large-particle titanium powder in a weight ratio of 4:6-7:3, wherein the particle size of the small-particle titanium powder is 1-15μm, and the particle size of the large-particle titanium powder is 35-180μm; the reinforcing phase raw material is one of B4C, TiB2 or graphite flakes with a particle size of 0.2-3μm; S2. Place the mixed powder obtained in step S1 in a vacuum drying oven and vacuum dry for 3-6h to obtain a dry powder; S3. The dry powder and binder obtained in step S2 are placed in a 3D printer, and the binder is sprayed to form a 3D printed component; the binder is composed of ethylene glycol monomethyl ether, diethylene glycol, and water in a volume ratio of 1:2:7, and the layer thickness of the binder during spraying is 0.05-0.25 mm; S4. Vacuum degreasing the 3D printed component obtained in step S3 for 0.5-1.5h to obtain a degreased 3D printed component; S5. Place the degreased 3D printed component obtained in step S4 in a vacuum furnace, and after vacuum sintering, cool it to room temperature in the furnace to obtain a titanium-based composite material.

2. The additive manufacturing method of a titanium-based composite material according to claim 1, characterized in that: In the step S1, the ball milling speed is 180-240 rpm, the ball-to-material ratio is 1:1-5:1, and the ball milling jar and the grinding balls are made of stainless steel.

3. The additive manufacturing method of a titanium-based composite material according to claim 1, characterized in that: In step S2, the vacuum drying temperature is 110-150°C.

4. The additive manufacturing method of a titanium-based composite material according to claim 1, characterized in that: In step S4, the vacuum degreasing temperature is 350-550°C and the vacuum degree is 10 -5 -10 -2 Pa.

5. The additive manufacturing method of a titanium-based composite material according to claim 1, characterized in that: In step S5, the vacuum degree of vacuum sintering is 10 -5 -10 -2 Pa, the heating rate is 10℃ / min; the vacuum sintering process is: heating from room temperature to 400℃ and keeping warm for 1-2h, then heating to 1250-1500℃ and keeping warm for 4-8h.

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