Thermal-electric coupling sintering device for forming metal powder green body through binder spraying 3D printing and sintering method of thermal-electric coupling sintering device

Abstract

The invention discloses a thermal-electric coupling sintering device for forming a metal powder green body through binder jet 3D printing and a sintering method of the thermal-electric coupling sintering device. The method comprises the following steps: adjusting parameters such as printing layer thickness, powder laying speed, binder saturation and the like for printing, heating a printed green body in a curing oven to 120-200 DEG C for curing, and then heating the green body in a sintering furnace to 400-900 DEG C for degreasing and heat preservation. And after degreasing is completed, the temperature continues to rise to the solid-phase sintering temperature for sintering densification, meanwhile, current of 1-500 A / cm < 2 > is introduced into the sample, and the metal green body is subjected to sintering densification under the thermal-electric coupling effect. According to the thermal-electric coupling sintering device for forming the metal powder green body through binder jet 3D printing, the corresponding thermal-electric coupling sintering method is provided, the green body can be rapidly sintered into a compact metal sample at the low temperature under the condition that no external pressure exists, and meanwhile high strength-plasticity can be obtained.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing (3D printing), in particular to the research direction of binder jet 3D printing forming-sintering of metal powder. Background Art

[0002] Binder Jetting 3D Printing (BJ3DP) is a high-efficiency, low-cost 3D printing technology that can realize the forming of complex parts. It has been widely used in the forming of materials such as ceramics, stainless steel, high-temperature alloys, and titanium alloys.

[0003] BJ3DP can be used to form materials with porous complex structures and larger materials. The forming process is divided into several main steps: printing, curing, degreasing and densification sintering of green bodies. In terms of densification sintering process, it is similar to conventional powder metallurgy and MIM. Generally, metal parts formed by BJ3DP can obtain relatively dense samples after hot sintering (without external pressure), but there are problems such as high sintering temperature, long time, coarse grains of materials, and high porosity.

[0004] In the powder metallurgy and MIM forming process of metal materials, multi-field coupled sintering can solve the problems of rapid sintering and densification of green billets. Spark plasma sintering (SPS) is a typical thermal-electric-mechanical multi-field coupled sintering method, which uses the principle of pulse discharge and mechanical pressure to achieve low-temperature, short-time rapid densification of metal powder, while controlling the growth of grains. However, since the green billets formed by BJ3DP have characteristics such as complex shapes / porous structures, it is impossible to apply pressure during the sintering process. Therefore, the thermal-electric-mechanical multi-field coupled sintering method is not applicable to the densification sintering of BJ3DP green billets. Similarly, the hot isostatic pressing process (thermal-mechanical coupling) is only suitable for BJ3DP green billets with simple shapes, and cannot meet the requirements of BJ3DP green billets with complex shapes and structures. At present, there is no report on the thermal-electric coupled sintering densification process of BJ3DP green billets of metal powder. Summary of the invention

[0005] The present invention provides a thermal-electric coupling sintering device and a sintering method for metal powder green bodies formed by binder jet 3D printing, which utilizes the Joule thermal effect, electromigration effect and electroplastic effect between metal powder and electric current, so that the green bodies printed by 3DP can obtain metal materials with higher density, higher strength and better plasticity during the sintering process.

[0006] The invention provides a thermal-electric coupling sintering device for forming metal powder green bodies by binder jetting 3D printing, comprising: ① a furnace body, ③ an electrode plate, ④ an insulating device, ⑤ a wire, and ⑥ a power source.

[0007] The present invention provides a method for thermal-electric coupling sintering of metal powder green bodies formed by binder jet 3D printing, and the specific steps are as follows:

[0008] Step (1): Green body printing and molding. Adjust the printing parameters such as layer thickness and binder saturation, and perform 3DP printing on metal or high entropy alloy powder to obtain a green body.

[0009] Step (2): Solidification and degreasing. The green body is placed in a solidification furnace for solidification and heat preservation, and then placed in a sintering furnace for degreasing and heat preservation.

[0010] Step (3): Thermal-electric coupled sintering of green body. Place the degreased green body on an electrode plate, pass current, and perform thermal-electric coupled sintering, while using vacuum or atmosphere protection. After sintering is completed, cool and obtain the sample.

[0011] Furthermore, in step (1), the metal powder includes but is not limited to: aluminum alloy, copper alloy, nickel alloy and titanium alloy.

[0012] Furthermore, in step (1), the high entropy alloy powder includes but is not limited to AlFeCoCrNi 2.1 , FeCoCrNi, TiZrNbHfNi, TiZrNbMoTa, CoCrFeMnNi, CoCrFeMnNiTi and Al 0.5 Cr 0.9 FeNi 2.5 V 0.2 wait.

[0013] Furthermore, in step (1), the metal powder has a particle size of 10-150 μm and a spherical or irregular shape.

[0014] Furthermore, in step (1), the printing parameters are: layer thickness is about 60-200 μm, binder saturation is 35%-80%, powder spreading speed is 5-20 pps, and powder spreading shaft rotation speed is 10-30 pps.

[0015] Furthermore, in step (2), the curing temperature is 120-200°C, the heating rate is 1-10°C / min, and the holding time is 90-150min.

[0016] Furthermore, in step (2), the degreasing temperature is 400-900°C, the heating rate is 1-10°C / min, and the insulation time is 1-4h.

[0017] Furthermore, in step (3), the thermal-electric coupling sintering temperature is generally 10-100° C. lower than the melting point of the material, the heating rate is 1-10° C. / min, and the holding time is 1-8 h.

[0018] Furthermore, in step (3), the current applied during the thermal-electric coupled sintering is 1-500A / cm 2 , the type of current is direct current or alternating current.

[0019] Furthermore, in step (3), the thermal-electrical coupling sintering is performed by vacuuming or introducing an inert gas such as nitrogen or argon for protection.

[0020] The principle of the present invention is:

[0021] The present invention adopts the principle of thermal-electric coupling sintering, and utilizes the Joule heating effect, electromigration effect and electroplastic effect between metal powder and electric current, so that the contact neck between powders of 3DP metal powder green body can be quickly connected in the initial stage of sintering densification, thereby accelerating the densification process and obtaining a higher density. At the same time, the green body can form a smaller and denser structure under the action of electric current, so that the strength and plasticity of the sintered metal material are better.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1. Compared with ordinary hot sintering furnaces, the thermal-electric coupled sintering device of the present invention can achieve low-temperature sintering molding with lower energy consumption.

[0024] 2. Compared with ordinary high-temperature sintering process, the green body can form a smaller and denser structure under the action of electric current, with better strength and plasticity.

[0025] 3. Compared with ordinary high-temperature sintering process, the green body can be degreased more fully under the action of electric current, which greatly reduces the influence of carbon residue of binder on material properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure diagram of the thermal-electric coupling sintering device is shown in FIG. 1 : furnace body; 2 : green body after degreasing; 3 : electrode plate; 4 : insulating device; 5 : wire; 6 : power supply.

[0027] Figure 2 This is the metallographic structure diagram of the thermal-electric sintering sample of Example 9. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the thermal-electrically coupled sintering device in the following embodiment includes a furnace body ①, an electrode plate ③, an insulating device ④, a wire ⑤ and a power supply ⑥; the electrode plate ③ is arranged inside the furnace body ①, and the electrode plate ③ is connected to the power supply ⑥ through the wire ⑤; the degreased green body ② is arranged in the middle of the electrode plate ③; the insulating device ④ is arranged at the contact part of the wire ⑤ with the furnace body ①.

[0031] Example 1

[0032] (1) Green printing

[0033] The printing uses spherical 6061 aluminum alloy powder with a particle size of 13-53μm and a median particle size of about 20μm. The printing parameters are: layer thickness 60μm, binder saturation 35%, powder laying axis rotation speed 10pps and powder laying axis movement speed 5pps. The green body size is 24mm×12mm×10mm.

[0034] (2)Curing degreasing

[0035] The printed green body was placed in a curing furnace for curing. The temperature was raised to 120°C at a rate of 1°C / min and kept for 90 minutes. Then, the temperature was raised to 400°C at a rate of 1°C / min for degreasing. The holding time was 1 hour.

[0036] (3) Thermal-electrical coupled sintering of green parts

[0037] Then continue to heat up to the densification temperature at a rate of 1°C / min and keep the temperature for 1h for sintering and densification. 2 The sample is subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature is lowered to room temperature at a rate of 5℃ / min, and high vacuum is maintained throughout the sintering process.

[0038] Example 2

[0039] (1) Green printing

[0040] The printing uses spherical H62 copper alloy powder with a particle size of 13-53μm and a median particle size of about 30μm. The printing parameters are: layer thickness 70μm, binder saturation 40%, powder laying axis rotation speed 15pps and powder laying axis movement speed 10pps. The green body size is 24mm×12mm×10mm.

[0041] (2)Curing degreasing

[0042] The printed green body was placed in a curing furnace for curing. The temperature was raised to 130°C at a rate of 2°C / min and kept for 100 minutes. Then, the temperature was raised to 500°C at a rate of 2°C / min for degreasing. The holding time was 1.5 hours.

[0043] (3) Thermal-electrical coupled sintering of green parts

[0044] Then continue to heat up to the densification temperature at a rate of 2°C / min and keep it for 2h for sintering and densification. 2 The sample is subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature is lowered to room temperature at a rate of 5℃ / min, and high vacuum is maintained throughout the sintering process.

[0045] Example 3

[0046] (1) Green printing

[0047] The printing uses spherical N6 nickel alloy powder with a particle size of 13-53μm and a median particle size of about 40μm. The printing parameters are: layer thickness 80μm, binder saturation 50%, powder laying axis rotation speed 20pps and powder laying axis movement speed 15pps. The green body size is 24mm×12mm×10mm.

[0048] (2)Curing degreasing

[0049] The printed green body was placed in a curing furnace for curing. The temperature was raised to 140°C at a rate of 3°C / min and kept at that temperature for 110 min. Then, the temperature was raised to 550°C at a rate of 3°C / min for degreasing. The holding time was 2 h.

[0050] (3) Thermal-electrical coupled sintering of green parts

[0051] Then continue to heat up to the densification temperature at a rate of 3°C / min and keep the temperature for 3h for sintering and densification. 2 The sample is subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature is lowered to room temperature at a rate of 5℃ / min, and high vacuum is maintained throughout the sintering process.

[0052] Example 4

[0053] (1) Green printing

[0054] The printing uses spherical TC4 titanium alloy powder with a particle size of 25-60μm, a median particle size of about 40μm, and printing parameters: layer thickness 90μm, binder saturation 60%, powder laying axis rotation speed 25pps and powder laying axis movement speed 20pps. The green body size is 24mm×12mm×10mm.

[0055] (2)Curing degreasing

[0056] The printed green body was placed in a curing furnace for curing. The temperature was raised to 150°C at a rate of 4°C / min and kept for 120 min. Then, the temperature was raised to 600°C at a rate of 4°C / min for degreasing. The holding time was 3 h.

[0057] (3) Thermal-electrical coupled sintering of green parts

[0058] Then continue to heat up to the densification temperature at a rate of 4 °C / min and keep the temperature for 4 h for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the sintering process was carried out in a nitrogen atmosphere.

[0059] Example 5

[0060] (1) Green printing

[0061] Printing of spherical AlFeCoCrNi 2.1 High entropy alloy powder, particle size is 33-75μm, the median particle size is about 50μm, printing parameters are: layer thickness 100μm, binder saturation 65%, powder laying axis rotation speed 17pps and powder laying axis moving speed 7pps. The green body size is 24mm×12mm×10mm.

[0062] (2)Curing degreasing

[0063] The printed green body was placed in a curing furnace for curing. The temperature was raised to 160°C at a rate of 5°C / min and kept at that temperature for 130 min. Then the temperature was raised to 700°C at a rate of 5°C / min for degreasing. The holding time was 4 h.

[0064] (3) Thermal-electrical coupled sintering of green parts

[0065] Then continue to heat up to the densification temperature at a rate of 5°C / min and keep it for 5h for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the sintering process was carried out in a nitrogen atmosphere.

[0066] Example 6

[0067] (1) Green printing

[0068] The printing uses spherical FeCoCrNi high entropy alloy powder with a particle size of 43-85μm and a median particle size of about 60μm. The printing parameters are: layer thickness 110μm, binder saturation 70%, powder laying axis rotation speed 22pps and powder laying axis movement speed 13pps. The green body size is 24mm×12mm×10mm.

[0069] (2)Curing degreasing

[0070] The printed green body was placed in a curing furnace for curing. The temperature was raised to 170°C at a rate of 6°C / min and kept at this temperature for 140 minutes. Then, the temperature was raised to 750°C at a rate of 6°C / min for degreasing. The holding time was 1.5 hours.

[0071] (3) Thermal-electrical coupled sintering of green parts

[0072] Then continue to heat up to the densification temperature at a rate of 6 ° C / min and keep it for 6 hours for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the sintering process was carried out in a nitrogen atmosphere.

[0073] Example 7

[0074] (1) Green printing

[0075] The printing uses spherical CoCrFeMnNi high entropy alloy powder with a particle size of 80-160μm and a median particle size of about 100μm. The printing parameters are: layer thickness 120μm, binder saturation 80%, powder laying axis rotation speed 26pps and powder laying axis movement speed 16pps. The green body size is 24mm×12mm×10mm.

[0076] (2)Curing degreasing

[0077] The printed green body was placed in a curing furnace for curing. The temperature was raised to 180°C at a rate of 7°C / min and kept for 150 minutes. Then, the temperature was raised to 800°C at a rate of 7°C / min for degreasing. The holding time was 2.5 hours.

[0078] (3) Thermal-electrical coupled sintering of green parts

[0079] Then continue to heat up to the densification temperature at a rate of 7 ° C / min and keep it for 7 hours for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the argon atmosphere was introduced throughout the sintering process.

[0080] Example 8

[0081] (1) Green printing

[0082] Printing uses irregularly shaped CoCrFeMnNiTi high entropy alloy powder with a particle size of 160-200μm, a median particle size of about 140μm, and printing parameters: layer thickness 180μm, binder saturation 75%, powder laying axis rotation speed 28pps, and powder laying axis movement speed 18pps. The green body size is 24mm×12mm×10mm.

[0083] (2)Curing degreasing

[0084] The printed green body is placed in a curing furnace for curing. The temperature is raised to 190°C at a rate of 8°C / min and kept for 140 minutes. Then, the temperature is raised to 850°C at a rate of 8°C / min for degreasing. The holding time is 3 hours.

[0085] (3) Thermal-electrical coupled sintering of green parts

[0086] Then continue to heat up to the densification temperature at a rate of 8 °C / min and keep the temperature for 7.5 h for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the argon atmosphere was introduced throughout the sintering process.

[0087] Example 9

[0088] (1) Green printing

[0089] Printing using spherical Al 0.5 Cr 0.9 FeNi 2.5 V 0.2 High entropy alloy powder, particle size is 160-200μm, the median particle size is about 150μm, printing parameters are: layer thickness 200μm, binder saturation 80%, powder laying axis rotation speed 30pps and powder laying axis moving speed 20pps. The green body size is 24mm×12mm×10mm.

[0090] (2)Curing degreasing

[0091] The printed green body is placed in a curing furnace for curing. The temperature is increased to 200°C at a rate of 10°C / min and kept for 150 minutes. Then, the temperature is increased to 900°C at a rate of 10°C / min for degreasing. The holding time is 4 hours.

[0092] (3) Thermal-electrical coupled sintering of green parts

[0093] Then continue to heat up to the densification temperature at a rate of 10 °C / min and keep it for 8 hours for sintering and densification. 2 The sample was subjected to the action of the electric current under the action of the thermal field. After the heat preservation, the temperature was lowered to room temperature at a rate of 5℃ / min, and the argon atmosphere was introduced throughout the sintering process.

[0094] (4) Metallographic sample preparation

[0095] The fired sample was cut into 5x5x5mm squares, and one side was selected to be polished with 600 mesh, 1200 mesh, and 2500 mesh metallographic sandpaper in turn, and then polished, dripped with 1.5μm diamond polishing liquid for 2 minutes, and then corroded with aqua regia for 7s, the water stains were blown off, and the sample was observed under a metallographic microscope. The morphology is as follows: Figure 2 As shown in the figure, it is not difficult to find that the grains of the hot-sintered samples are coarse, basically around 200μm, and there are a large number of pores distributed between the grains, which significantly affects the performance of the samples.

Claims

1. A method for thermal-electric coupling sintering of metal powder green bodies by binder jetting 3D printing, characterized in that: The main steps of the thermal-electrical coupled sintering method are: Step (1): green body printing and molding: adjusting printing parameters, and performing 3DP printing on metal powder or high entropy alloy powder to obtain green body; the printing parameters include layer thickness, binder saturation, powder spreading speed and powder spreading shaft rotation speed; Step (2): curing and degreasing: placing the green body into a curing furnace for curing and heat preservation, and then placing it into a sintering furnace for degreasing and heat preservation; Step (3): Thermal-electrically coupled sintering of green body: Place the degreased green body on the electrode plate of a thermal-electrically coupled sintering device, pass current, perform thermal-electrically coupled sintering, and use vacuum or atmosphere protection. After sintering is completed, cool and obtain the sample.

2. According to the thermal-electrically coupled sintering method for binder jet 3D printing formed metal powder green body according to claim 1, in step (1), the metal powder comprises aluminum alloy, copper alloy, nickel alloy or titanium alloy; the metal powder particle size is 10-150 μm, and the morphology is spherical or irregular.

3. According to the thermal-electric coupled sintering method of binder jet 3D printing forming metal powder green body according to claim 1, in step (1), the high entropy alloy powder comprises AlFeCoCrNi 2.1 , FeCoCrNi, TiZrNbHfNi, TiZrNbMoTa, CoCrFeMnNi, CoCrFeMnNiTi or Al 0.5 Cr 0.9 FeNi 2.5 V 0.2 .

4. According to the thermal-electrically coupled sintering method for forming metal powder green bodies by binder jet 3D printing according to claim 1, in step (1), the printing parameters are: layer thickness is 60-200 μm, binder saturation is 35%-80%, powder spreading speed is 5-20 pps, and powder spreading shaft rotation speed is 10-30 pps.

5. According to the thermal-electric coupled sintering method for binder jet 3D printing formed metal powder green body as described in claim 1, in step (2), the curing temperature is 120-200°C, the heating rate is 1-10°C / min, and the holding time is 90-150min.

6. According to the thermal-electric coupled sintering method for binder jet 3D printing formed metal powder green body as described in claim 1, in step (2), the degreasing temperature is 400-900°C, the heating rate is 1-10°C / min, and the holding time is 1-4h.

7. According to the thermo-electrically coupled sintering method for binder jet 3D printing formed metal powder green body according to claim 1, in step (3), the thermo-electrically coupled sintering temperature is generally 10-100°C lower than the melting point of the powder, the heating rate is 1-10°C / min, and the holding time is 1-8h.

8. According to the method for heat-electric coupling sintering of metal powder green body formed by binder jet 3D printing as claimed in claim 1, in step (3), the current applied during the heat-electric coupling sintering is 1-500A / cm 2 , the type of current is direct current or alternating current.

9. According to the method for thermal-electrically coupled sintering of metal powder green bodies formed by binder jet 3D printing as described in claim 1, in step (3), the thermal-electrically coupled sintering is protected by vacuuming or passing nitrogen or argon inert gas.

10. The thermal-electrically coupled sintering device used in the method according to any one of claims 1 to 9, characterized in that: The invention comprises a furnace body, an electrode plate, an insulating device, a wire and a power source; the electrode plate is arranged inside the furnace body, and the electrode plate is connected to the power source through the wire; the degreased green body in step (2) is arranged in the middle of the electrode plate; the contact part between the wire and the furnace body is provided with an insulating device.

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