Powder metallurgy rheological manufacturing method for multi-material component

Abstract

The invention provides a powder metallurgy rheological manufacturing method of a multi-material component, which comprises the following steps: respectively mixing N groups of different raw material powder with a thermoplastic polymer binder to obtain N parts of materials, respectively crushing the N parts of materials to obtain N powder material particles, sequentially laying the N parts of material particles in a mold according to the structure of the multi-material component, and forming the multi-material component. Or at least one part of the material particles is preformed to obtain a green body, the green body and other material particles are laid in a mold, the mold is firstly pre-pressed, and then the mold is subjected to low-temperature hot press molding to obtain the multi-material component blank. According to the method, near-net forming of complex multi-material components is achieved, provided materials have the capacity of melting flowing and solidification shaping, powder can be formed like polymers, the method can be suitable for various powder metallurgy material systems, the provided forming mode has high dimensional precision, and the method is suitable for large-scale industrial production. The prepared complex multi-material component can be widely applied to the industries of mechanical manufacturing, energy environment, bionic medicine and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy and powder engineering, and particularly relates to a powder metallurgy rheological manufacturing method for multi-material components. Background Art

[0002] Multi-material structures are inspired by natural bionic structures. By assembling different materials, they provide more possibilities for material design and achieve the integration of structure and function, which prompts researchers to explore their design principles and manufacturing methods. So far, due to the good processing performance of polymers, the research on multi-material polymers and their composites has advanced rapidly, and with the development of multi-material 3D printing technology, the multi-material and multi-structure integration of polymers has become more feasible. In contrast, metals, ceramics, and cermets pose challenges to their multi-material assembly due to their high melting points and large differences between melting points. The existing metal, ceramic, and cermet material systems are still limited, often using materials with similar melting points or gradient materials, and the formed multi-material structures are often relatively simple, such as layered structures, single-section structures, etc.

[0003] Plasticized forming is a near-net shaping method in powder metallurgy. By mixing metal or ceramic powders with a binder, the raw materials acquire the ability to flow, solidify, and form. Combining with subsequent debinding and sintering processes, this method can produce complex powder metallurgy components. This technology allows the use of polymer processing methods to form metal, ceramic, and cermet materials. Applying this technology to the forming of multi-material structures has significant advantages. For example, the powder extrusion 3D printing technology uses a printing process similar to fused deposition modeling and can directly realize multi-material structures through multi-nozzle printing. It may be the most promising technology for the multi-material forming of metals and ceramics. However, this printing method has problems with poor interlayer properties, and when dealing with multiple material combinations, the requirements for equipment and operation increase significantly. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a powder metallurgy rheological manufacturing method for multi-material components. By mixing powders of different materials with a thermoplastic polymer binder to obtain materials, and then co-forming the different materials by low-temperature hot pressing, this method has the characteristics of low forming temperature, high dimensional accuracy, low cost, etc., and is applicable to the large-scale preparation of complex multi-material structures with complex shapes and is applicable to most powder metallurgy material systems.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A powder metallurgy rheological manufacturing method for a multi-material component. N groups of different raw material powders are respectively mixed with a thermoplastic polymer binder to obtain N portions of materials. The N portions of materials are respectively crushed to obtain N portions of material particles. According to the structure of the multi-material component, the N portions of material particles are sequentially laid in a mold, or at least one of the portions of material particles is preformed to obtain a green body, and the green body and other material particles are laid in the mold. First, the mold is pre-pressed, and then the mold is subjected to low-temperature hot pressing to form a multi-material component blank.

[0007] In the preparation method of the present invention, a thermoplastic polymer binder is used to mix with multi-materials to form special materials, enabling the materials to have the ability of viscous flow and solidification molding, so that the materials can be processed at a low temperature (above the softening point of the binder below 200 °C), with extremely high forming and shaping ability and detail resolution, and the preparation of complex components can be realized; the materials of different materials are crushed into tiny particles, and then the material particles are pre-laid according to the designed multi-material structure and pressed to make them close to dense. After the materials are heated and melted, the remaining pores are filled near the initial position while retaining the preset multi-material structure; after cooling and demolding, a multi-material blank with high detail resolution, high surface quality, and complex shape structure is obtained. After that, the binder component in the blank is removed through a debinding process, and then the debound blank is sintered to finally obtain a complex multi-material component. Compared with the conventional pressing-sintering method, the shape complexity of the formable products is significantly improved; compared with the multi-nozzle extrusion 3D printing using the same special materials, the formed green body is more dense, the properties in all directions are consistent, there are no interlayer defects, and the operation is simpler and the cost is lower.

[0008] Preferably, N≥2.

[0009] Preferably, the raw material powder is selected from at least one of metal powder, ceramic powder, and cermet powder having a co-sintering temperature.

[0010] Among them, the metal powder is such as stainless steel, titanium alloy, copper alloy, tungsten alloy, etc., the ceramic powder is such as alumina, silicon carbide, etc., and the cermet powder is such as NiFe 2 O 4 cermet.

[0011] Preferably, the thermoplastic polymer binder is selected from one of wax-based binders, water-based binders, and plastic-based binders.

[0012] Further preferably, the wax-based binder is selected from at least one of paraffin wax, beeswax, microcrystalline wax, carnauba wax, and polyethylene wax binder.

[0013] Further preferably, the water-based binder is a polyethylene glycol binder.

[0014] More preferably, the plastic-based binder is a polyoxymethylene binder.

[0015] In a preferred embodiment, the mixing is carried out in a twin-screw mixer. The mixing temperature is 5-30 °C above the softening point of the thermoplastic polymer binder. The mixing time is 0.5-2 h, and the rotor speed is 20-100 rpm. After mixing, cooling gives N parts of the material.

[0016] In a preferred embodiment, in the N parts of the material, the volume fraction of the raw material powder is 50-70%, preferably 52-64%, and more preferably 52-58%.

[0017] In a preferred embodiment, the particle size of the N powder material particles is 5-1000 μm, preferably 550-700 μm. The inventor found that there is an obvious relationship between the particle size of the material particles and the interface resolution. Only by controlling within the scope of the present invention can a multi-material component with uniform material distribution and clear interfaces between different materials be obtained.

[0018] In actual operation, a crusher is used for crushing, and then the sieving through a sieve gives particle materials with a particle size within the above range.

[0019] In a preferred embodiment, according to the structure of the multi-material component, when the structure of the multi-material component has a boundary size > 1 mm, the N parts of the material particles are sequentially placed in a laying mold. When the structure of the multi-material component has a boundary size ≤ 1 mm, at least one part of the material particles is preformed to obtain a green body. When a green body is formed in advance and then compounded with the powder, when the obtained blank has complex structural details with a size less than 1 mm, it has higher dimensional accuracy and clearer multi-material interfaces. However, when the boundary size in the structure of the multi-material component > 1 mm, only by directly laying the powder can a clear multi-material interface that meets the product requirements be obtained.

[0020] In a preferred embodiment, the preforming method of at least one part of the material particles is by injection molding or extrusion 3D printing.

[0021] In a preferred embodiment, the pre-pressing pressure is 10-50 MPa.

[0022] In the present invention, a conventional hydraulic molding press is used to lay the particle materials of different materials at the corresponding positions in the mold according to the designed structure respectively, and a pressure of 10-50 MPa is applied in advance to make the material more compact. If the pressure is too small, the green body is not firm, and the shape control of the final product is poor, and the product accuracy cannot be guaranteed. If the pressure is too large, the particles will break and the distribution will be uneven.

[0023] Preferably, the temperature for low-temperature hot pressing is 5-30 °C above the softening point of the thermoplastic polymer binder, the pressure is 10-60 MPa, and heat and pressure are maintained for 5-60 min. After pre-pressing, the mold is heated and pressurized to the above range to maintain heat and pressure, and a blank with clear interfaces and high density can be obtained. After debinding and sintering, a multi-material component with clear interfaces and high strength can be obtained.

[0024] Preferably, the multi-material component blank is debound and sintered to obtain the multi-material component.

[0025] Further preferably, when there are N groups of different raw material powders, including a group of alloy powder and a group of ceramic powder or cermet powder, the sintering temperature is the solid-liquid coexistence temperature of the alloy component in the multi-material component blank, where the liquid-phase volume fraction of the alloy component is 5-60%, preferably 20-40%.

[0026] The inventor found that when there is a group of alloy powder and a group of ceramic powder or cermet powder, controlling the sintering temperature to the solid-liquid coexistence temperature of the alloy component in the multi-material component blank, at this time, the alloy material is super-solid phase sintering, and it is in a solid-liquid coexistence state during the sintering process, while the ceramic or cermet is solid-phase sintering, which can not only maintain the original shape but also relieve the stress generated by sintering shrinkage and reduce the generation of defects, making the performance of the material better.

[0027] Principle and Advantage

[0028] The present invention provides a powder metallurgy rheological manufacturing method for complex multi-material components. A thermoplastic binder is used to mix with metal / ceramic / cermet to make a special material, enabling the material to have the ability of viscous flow and solidification molding, so that the material can be processed at a low temperature (below 200 °C) above the softening point of the binder, with extremely high forming and shaping ability and detail resolution, and can realize the preparation of complex components; the materials of different materials are broken into tiny particles, and then the material particles are pre-laid according to the designed multi-material structure and pressed to make them close to dense. After the material is heated and melted, it fills the remaining pores near the initial position and retains the preset multi-material structure; after cooling and demolding, a multi-material blank with high detail resolution, high surface quality, and complex shape structure is obtained. Then, the binder component in the blank is removed through a debinding process, and the debound blank is sintered to finally obtain a complex multi-material component. Compared with the conventional pressing-sintering method, the shape complexity of the formed product is significantly improved; compared with the multi-nozzle extrusion 3D printing using the same special material, the formed green body is more dense, the properties in all directions are consistent, there are no interlayer defects, and the operation is simpler and the cost is lower.

[0029] The advantages of the present invention are as follows: (1) The method has a wide range of material applicability. In theory, the thermoplastic binder can be uniformly distributed through mixing and all powder metallurgy material systems that can be sintered and densified, such as non-ferrous metals, metal matrix composites, alloy materials, high-temperature resistant ceramic materials, and cermet materials. (2) The materials used have high flow and plastic forming capabilities. By pre-laying the particulate materials of different materials, high-resolution forming of multiple materials and various complex structures can be achieved, and the density uniformity of the products is high, with small performance differences in each region. (3) The process has wide operability. The materials used can be processed repeatedly, and the process can be combined with other plastic forming methods such as powder injection molding and extrusion 3D printing to achieve combined forming of complex multi-material components. Brief Description of the Drawings

[0030] Figure 1 : Powder metallurgy rheological manufacturing method for multi-material components. Among them, (a) is the preparation stage of the material, (b) is the green body forming stage, and (c) is the debinding and sintering stage.

[0031] Figure 2 : NiFe in Example 1 2 O 4 and Cu-20Ni material characteristics. Among them, (a) is the particle size of the particulate material after crushing, (b) is the microstructure of the NiFe 2 O 4 cermet material, and (c) is the microstructure of the Cu-20Ni alloy material.

[0032] Figure 3 : Complex multi-material structure of NiFe 2 O 4 cermet / Cu-20Ni alloy prepared from particulate materials in Example 1. Among them, (a) is the multi-material structure green body diagram with a pentagram shape in the middle, (a1) is its partial enlarged view, (b) is the multi-material structure green body diagram with a gear shape in the middle, and (b1) is its partial enlarged view.

[0033] Figure 4 : Precision multi-material structure of NiFe 2 O 4 cermet / Cu-20Ni alloy with internal screw and external gear in Example 2, where Figure 4 the upper figure in is the green body physical diagram of the precision multi-material of NiFe 2 O 4 cermet / Cu-20Ni alloy, Figure 4 the middle figure in is the partial enlarged view of the upper figure, Figure 4 and the lower figure in is the finished product diagram of the sintered multi-material component. Detailed Description of the Invention

[0034] Example 1

[0035] The two materials used in this example are NiFe 2 O 4 cermet and Cu-20Ni alloy. The specific steps are as follows:

[0036] Step S1, Mix the NiFe 2 O 4 cermet and Cu-20Ni alloy powders with a polyoxymethylene-based binder system respectively and uniformly. After cooling, NiFe 2 O 4 cermet materials and Cu-20Ni alloy materials are obtained respectively. The volume fraction of the powder is 52%. The component mass fraction of the polyoxymethylene binder: polyoxymethylene: polypropylene: stearic acid = 90%: 7.5%: 2.5%; The temperature during mixing is 180 °C, the mixing speed is 35 rpm, and the mixing time is 30 min;

[0037] Step S2, Place the two materials obtained in S1 into a crusher for crushing respectively; After sieving, NiFe 2 O 4 cermet particulate materials and Cu-20Ni alloy particulate materials are obtained respectively. The average particle size of the two particulate materials is about 630 μm. The particle size distribution and micro-morphology of the obtained particulate materials are as Figure 2 shown.

[0038] Step S3, Lay the particulate materials obtained in Step S2 in a circular cake mold. Among them, the Cu-20Ni alloy particulate materials are laid into the shapes of a five-pointed star and a gear, and NiFe 2 O 4 cermet materials are laid around and wrapped. Apply a pressure of 10 MPa and hold for 5 min to make the materials more compact.

[0039] Step S4, Raise the temperature of the mold to 180 °C, apply pressure to 20 MPa and hold for 10 min, and then cool and demold to obtain a complex multi-material green body as Figure 3 shown. The preset five-pointed star and gear shapes are well maintained, the interface is clear, and the density of the green body reaches 98%.

[0040] Step S5, Place the green body obtained in S4 into a catalytic debinding furnace for debinding. The debinding temperature is 120 °C and the time is 24 h. Then sinter at 1170 °C for 90 min. At this time, the Cu-20Ni alloy is in the super-solid state sintering state, and the liquid phase volume is 35%. NiFe 2 O 4The cermet is in a solid-phase sintering state, and the final product is obtained. The relative density of both phases after sintering reaches more than 95%. Among them, the interfacial shear strength of the gear shape is 60 MPa.

[0041] Example 2

[0042] This example uses the same material system as Example 1, and the preparation method and components of the materials are the same as those in Example 1. The difference is that the material of the Cu-20Ni alloy is a green compact with a complex structure prepared by injection molding, and then it is compression-molded with the NiFe 2 O 4 cermet material. The specific steps are as follows:

[0043] Step S1 is the same as S1 in the example.

[0044] Step S2: Place the NiFe 2 O 4 cermet material obtained in S1 into a crusher for crushing and sieving to obtain particulate materials with an average particle size of about 630 μm; extrude and pelletize the Cu-20Ni alloy material in a screw extruder. The working temperature is 180 °C, and the screw speed is 500 r / min. The obtained pelletized material is cylindrical particles with a diameter of 2 - 3 mm and a height of 3 - 5 mm.

[0045] Step S3: Extrude the cylindrical particulate material of the Cu-20Ni alloy obtained in S2 in an injection molding machine to prepare a precision screw structure. The injection temperature is 180 °C.

[0046] Step S4: Lay the NiFe 2 O 4 cermet particulate material in a mold, lay the Cu-20Ni structure obtained in S3 flat on the particulate material, then bury it with the particulate material, and apply a pressure of 5 MPa to make it compact.

[0047] Step S5: Raise the temperature of the mold to 180 °C, apply pressure up to 20 MPa and hold for 10 min, then cool and demold to obtain a complex multi-material structure with a screw inside and a gear outside as shown in Figure 4 . The surface quality of the green compact is high, the distribution of the binder and the powder is uniform, the relative density is as high as 98%, the formed multi-material structure has a high complexity and resolution, and the interface between the NiFe 2 O 4 cermet material and the Cu-20Ni alloy is clear and flat.

[0048] Step S6: Place the green compact obtained in S5 in a catalytic debinding furnace for debinding. The debinding temperature is 120 °C and the time is 30 h. Then sinter at 1170 °C to successfully obtain a product as shown in Figure 4As shown in the complex multi-material product, it can be seen that after sintering, the interface remains clear and flat, with high detail resolution.

[0049] Example 3

[0050] In this example, 90W-6.3Ni-2.7Cu-Sn tungsten alloy material and 30CrMnSiNi2A steel material are used.

[0051] Step S1: Mix 90W-6.3Ni-2.7Cu-Sn powder and 30CrMnSiNi2A powder with a polyethylene glycol-based binder system respectively and uniformly. After cooling, 90W-6.3Ni-2.7Cu-Sn material and 30CrMnSiNi2A material are obtained respectively. The volume fraction of the powder is 58%, and the mass fraction of the components of the polyethylene glycol binder system is: polyethylene glycol: high-density polyethylene: polypropylene: ethylene bisstearamide = 70%: 20%: 7%: 3%; the temperature during mixing is 150 °C, the mixing speed is 30 rpm, and the mixing time is 30 min.

[0052] Step S2: Place the 90W-6.3Ni-2.7Cu-Sn material obtained in S1 in a crusher for crushing and sieving to obtain particulate material with an average particle size of about 600 μm; extrude and pelletize the 30CrMnSiNi2A material in a screw extruder. The working temperature is 150 °C, the screw speed is 500 r / min, and the obtained pelletized material is cylindrical particles with a diameter of 2-3 mm and a height of 3-5 mm.

[0053] Step S3: Print a cylindrical structure with serrations using the 30CrMnSiNi2A cylindrical particulate material obtained in S2 in an extrusion 3D printer. The printing temperature is 180 °C.

[0054] Step S4: Place the cylindrical structure with serrations obtained in S3 in a mold, then uniformly lay the 90W-6.3Ni-2.7Cu-Sn particulate material in the mold and coat the cylindrical structure of 30CrMnSiNi2A, and apply a pressure of 5 MPa to make it compact.

[0055] Step S5: Raise the temperature of the mold to 150 °C, pressurize to 15 MPa and hold for 10 min, then cool and demold to obtain a green body of a complex multi-material structure with a serrated cylinder inside made of 30CrMnSiNi2A and a 90W-6.3Ni-2.7Cu-Sn cylinder outside. The density of the green body reaches 98%, and the two phases are evenly distributed and the interface is clear.

[0056] Step S6: Place the green body obtained in S5 in water for solvent debinding at a temperature of 60 °C for 30 h, and then sinter at 1200 °C. The shear strength at the interface between the two after sintering exceeds 300 MPa.

[0057] Comparative Example 1

[0058] Other conditions are the same as those in Example 1, except that after crushing, the material is not sieved, and the particle size of some of the obtained particulate materials is greater than 1000 μm.

[0059] The density of the obtained multi-material green body is 98%, but the interface tortuosity between the two materials is not clear, the details of the interface are not restored, and the dimensional accuracy is low.

[0060] Comparative Example 2

[0061] Other conditions are the same as those in Example 1, except that after placing the particulate material in the mold cavity, no pre-pressure is applied to compact the material.

[0062] The density of the obtained multi-material green body is 98%, but since the flow travel of the material becomes larger after softening, the preset interface and structure between the two materials are damaged.

Claims

1. A powder metallurgy rheological manufacturing method for a multi-material component, characterized in that: N groups of different raw material powders are mixed with thermoplastic polymer binders to obtain N parts of materials, and the N parts of materials are crushed to obtain N parts of material particles. According to the structure of the multi-material component, the N parts of material particles are laid in a mold in sequence, or at least one part of the material particles is pre-formed to obtain a green body, and the green body and other material particles are laid in the mold, the mold is first pre-pressed, and then the mold is subjected to low-temperature hot pressing to obtain a multi-material component blank.

2. The powder metallurgy rheological manufacturing method of a multi-material component according to claim 1, characterized in that: Said N≥2; The raw material powder is selected from metal powder, ceramic powder and metal ceramic powder having a co-sintering temperature.

3. The powder metallurgy rheological manufacturing method of a multi-material component according to claim 1, characterized in that: The thermoplastic polymer binder is selected from one of a wax-based binder, a water-based binder, and a plastic-based binder; The wax-based binder is selected from at least one of paraffin wax, beeswax, microcrystalline wax, carnauba wax, and polyethylene wax binder; The water-based adhesive is a polyethylene glycol adhesive; The plastic-based adhesive is a polyoxymethylene adhesive.

4. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: The mixing is carried out in a twin-rotor mixer, the mixing temperature is 5-30°C above the softening point of the thermoplastic polymer binder, the mixing time is 0.5-2h, and the rotor speed is 20-100rpm. After the mixing is completed, the mixture is cooled to obtain N portions of material; In the N parts of material, the volume fraction of raw material powder is 50-70%.

5. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: The particle size of the N powder material particles is 5-1000 μm.

6. The powder metallurgy rheological manufacturing method of a multi-material component according to claim 5, characterized in that: The particle size of the N powder material particles is 550-700 μm.

7. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: According to the structure of the multi-material component, when the structure of the multi-material component has a boundary size of >1 mm, N portions of material particles are laid in the mold in sequence, and when the structure of the multi-material component has a boundary size of ≤1 mm, at least one portion of the material particles is preformed to obtain a green compact; At least one of the material particles is pre-formed by injection molding or extrusion 3D printing.

8. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: The pre-pressing pressure is 10-50 MPa.

9. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: The temperature of the low-temperature hot pressing molding is 5-30° C. above the softening point of the thermoplastic polymer binder, the pressure is 10-60 MPa, and the temperature and pressure are maintained for 5-60 minutes.

10. A powder metallurgy rheological manufacturing method for a multi-material component according to any one of claims 1 to 3, characterized in that: The multi-material component blank is degreased and sintered to obtain the multi-material component.

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