Preparation method for MIM complex part of the same material as profiling fixture

Abstract

A preparation method for an MIM complex part of the same material as a profiling fixture, comprising the following steps: a feedstock preparation step: adding an alloy, a plastic material, a toughening agent and a fluidity improving agent into an internal mixer for internal mixing and pelletizing to obtain an alloy feedstock; an injection molding step: using an injection molding machine to inject the alloy feedstock to form a part and a profiling fixture; a coating step: at least coating a surface under contact of the part and / or the profiling fixture with a nano-ceramic ink and drying; a debinding step: using oxalic acid debinding technique to debind the part and / or the profiling fixture coated with the nano-ceramic ink; and a sintering step: combining the debinded part and profiling fixture and then placing same into a vacuum furnace for sintering, to obtain a part having a smooth hard layer. The method effectively solves the problem of separation of parts and profiling fixtures of the same material, and prepared parts have high surface hardness and high size precision.

Description

A method for preparing MIM complex parts of the same quality as the profiling fixture Technical Field

[0001] The invention belongs to the technical field of metal powder injection molding, and particularly relates to a method for preparing a MIM complex part that is homogeneous with a profiling jig. Background Art

[0002] MIM (metal powder injection molding) is an abbreviation for metal powder injection molding. It is a molding method in which a plasticized mixture of metal powder and its binder is injected into a mold. The selected powder and binder are first mixed, then the mixture is granulated and injected into the desired shape. The polymer imparts its viscous flow characteristics to the mixture, which facilitates forming, mold cavity filling, and uniform powder loading. After forming, the binder is removed, and the debinded blank is sintered. Some sintered products may require further densification, heat treatment, or machining. Sintered products not only possess the same complex shapes and high precision as products produced by plastic injection molding, but also possess physical, chemical, and mechanical properties similar to forgings. This process is suitable for the mass production of small, precise, three-dimensional metal parts with complex shapes and special performance requirements.

[0003] Currently, some are applying this process to large, thin-walled MIM parts with curved edges. However, when applying MIM technology to these large, thin-walled parts, critical curvatures and dimensions can easily deform during the sintering process. Therefore, a profiling jig is required to support and prevent part deformation during the sintering process. A good profiling jig can maintain critical dimensions, minimize deformation, and reduce the workload of post-processing. Therefore, profiling jig design is particularly important.

[0004] However, when designing and manufacturing profiling jigs, if the part material and the profiling jig material differ, their shrinkage ratios will differ, making the part prone to cracking or deformation and poor dimensional accuracy. If the part material and the profiling jig material are identical (i.e., homogeneous), despite the same shrinkage ratio, the profiling jig and part will sinter together due to being made of the same material, making them impossible to separate. Furthermore, currently, high surface hardness is required to prevent scratching. This requires adjusting the material composition or heat treating the sintered part to achieve the required surface hardness. However, adjusting the material composition of the part presents two problems: first, it affects the overall mechanical properties of the material; second, some high-hardness surfaces cannot be achieved by fine-tuning the base material composition. Heat treating the sintered part also presents two problems: first, it requires additional steps and increases production costs; second, the heat treatment may generate residual stress, causing cracking, surface quality issues, and grain growth that reduces the toughness and strength of the material, thus affecting the overall performance of the part.

[0005] When the material of the part and the profiling jig are the same, separating the part from the profiling jig and enhancing the surface hardness of the part become urgent problems to be solved. Summary of the Invention

[0006] (1) Technical issues to be resolved

[0007] In order to solve the above problems of the prior art, the present invention provides a method for preparing MIM complex parts that are homogeneous with the profiling jig. This method solves the problem of separating homogeneous parts from the profiling jig, so that the prepared parts have high surface hardness and high dimensional accuracy.

[0008] (2) Technical solution

[0009] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0010] A method for preparing a complex MIM part having the same properties as a profiling fixture comprises the following steps:

[0011] Feed material preparation steps: adding alloy, plastic material, toughening agent, and fluidity improver into a mixer, mixing and pelletizing to obtain alloy feed material;

[0012] Injection molding step: Use an injection molding machine to inject the alloy feed into parts and profiling jigs;

[0013] Coating step: coating the nano-ceramic ink at least onto the surface of the part and / or the profiling jig to be in contact and drying;

[0014] Degreasing step: Use oxalic acid degreasing process to degrease the parts and profiling jigs coated with nano-ceramic ink;

[0015] Sintering step: The degreased parts and the profiling jig are combined and placed in a vacuum furnace for sintering to obtain parts with a smooth hard layer.

[0016] Preferably, in the coating step:

[0017] Nano-ceramic ink is made of nano-ceramic powder mixed with anhydrous ethanol and additives;

[0018] The nano ceramic powder is nano-aluminum oxide, nano-titanium oxide or nano-titanium nitride, and the particle size of the nano ceramic powder is 20-500nm;

[0019] In nano-ceramic ink, the mass concentration of nano-ceramic powder is 1-20%;

[0020] The additive is one or more of oleic acid, stearic acid and PVP;

[0021] The drying method is to dry in air for 10-30 minutes.

[0022] Preferably, the preparation method of the nano-ceramic ink is: adding the nano-ceramic powder and additives to anhydrous ethanol, fully stirring and ultrasonicating for 20-40 minutes at an ultrasonic frequency of 28-100 khz, and then filtering with a filtration accuracy of 4.5-5.5 μm.

[0023] Preferably, in the coating step: the thickness of the nano-ceramic ink coating is 10-100 μm.

[0024] Preferably, in the feed preparation step, the alloy is an iron-based alloy or a nickel-based alloy, the alloy powder particle size is 1-25 μm, and the banburying time is 0.8-1.5 hours;

[0025] In parts by weight: the amount of alloy used in the feed is 88%-92%.

[0026] Preferably, the alloys include stainless steel, low alloy steel and die steel, and the stainless steel includes 17-4, 304 and 316.

[0027] Preferably, in the injection molding step, the temperature of the injection mold is 60°C-120°C, and the temperature of the alloy feed is 170-210°C.

[0028] Preferably, the defatting step comprises:

[0029] S1: rinse for 50-70 minutes, degreasing temperature is 100-200℃, acid feeding rate is 1-3g / min;

[0030] S2: Degreasing for 15-30 hours, degreasing temperature is 100-200℃, acid feeding rate is 1-7g / min;

[0031] S3: Rinse for 1-4 hours, the flushing temperature is 100-200℃, and the acid injection amount is 0.

[0032] Preferably, the coating step adopts a coating method including spraying or coating, and the sintering step adopts a three-stage sintering process;

[0033] In the sintering steps: the first stage is sintered under nitrogen, the second stage is pre-sintered under vacuum, and the third stage is sintered under argon.

[0034] Preferably, the first stage sintering temperature is 0-800°C and the sintering time is 10-20 hours;

[0035] The second stage sintering temperature is 800-1100℃ and the sintering time is 1-5 hours;

[0036] The third stage sintering temperature is 1100-1400℃, the sintering time is 1-10 hours, and after sintering is completed, the temperature is slowly lowered to room temperature.

[0037] (3) Beneficial effects

[0038] The beneficial effects of the present invention are:

[0039] Through the technical solution of the present invention, the same part material and profiling jig material are used, and nano-ceramic ink is applied on the contact surface of the part and the profiling jig to form a nano-ceramic ink isolation layer, so that the part and the profiling jig have the same shrinkage ratio and shrinkage temperature. During the sintering process, the part and the profiling jig will not be sintered together and can be easily separated, effectively solving the problem of the part and the profiling jig being sintered together due to homogeneous co-firing, thereby ensuring the dimensional accuracy of large-scale, thin-walled and complex MIM parts during sintering; at the same time, the nanoparticles in the nano-ceramic ink can penetrate into the surface of the metal part. The obtained metal part has the ductility of the metal material and the hardness of the metal surface is similar to that of the ceramic material, that is, it has the hard characteristics of the ceramic material. The high hardness of the part surface can effectively prevent the part from being scratched; and the curvature of the part and the profiling jig are consistent (or the structural form is consistent), and the profiling jig can well support the part to achieve the shaping effect; finally, the profiling jig in the present invention is homogeneous with the part and both adopt the MIM preparation process. Compared with the profiling jig using ceramics (the production cost of ceramic profiling jigs is high and pollutes the environment), the production cost is low and it is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic diagram of the arrangement of parts, nano-ceramic ink isolation layer, and profiling fixture in the present invention.

[0041] The following are marked in the accompanying drawings:

[0042] Part 1, nano-ceramic ink isolation layer 2, profiling fixture 3. DETAILED DESCRIPTION

[0043] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0044] The present invention provides a method for preparing a MIM complex part having the same quality as a profiling jig, which comprises the following steps:

[0045] Feed material preparation steps: adding alloy, plastic material, toughening agent, and fluidity improver into a mixer, mixing and pelletizing to obtain alloy feed material;

[0046] Injection molding step: Use an injection molding machine to inject the alloy feed into parts and profiling jigs;

[0047] Coating step: coating the nano-ceramic ink at least onto the surface of the part and / or the profiling jig to be in contact and drying;

[0048] Degreasing step: Use oxalic acid degreasing process to degrease the parts and profiling jigs coated with nano-ceramic ink;

[0049] Sintering step: The degreased parts and the profiling jig are combined and placed in a vacuum furnace for sintering to obtain parts with a smooth hard layer.

[0050] Through the technical solution of the present invention, the same part material and profiling jig material are used, and nano ceramic ink is coated on at least the surface of the part and the profiling jig to be in contact (in the present invention, nano ceramic ink can be coated only on the part or the profiling jig, or on the part and the profiling jig at the same time; nano ceramic ink can be coated on the entire surface of the part or the profiling jig, or only on the contact surface when the part and the profiling jig are combined). First, the part and the profiling jig can have the same shrinkage ratio and shrinkage temperature, and the part and the profiling jig will not be sintered together during the sintering process and can be easily separated. After sintering, a part 1-nanoceramic ink isolation layer 2-profiling jig 3 structure will be formed (as shown in Figure 1), that is, a nano ceramic ink will be formed at the contact portion between the part and the profiling jig. The smooth, hard layer is formed because the part and the profiling jig are made of different materials than the nanoceramic ink isolation layer. This allows for easy separation of the part from the profiling jig after sintering, effectively resolving the problem of the part and profiling jig sticking together during co-firing. This ensures dimensional accuracy and minimal deformation during the sintering of large, thin-walled, complex MIM parts. Furthermore, the nanoparticles in the nanoceramic ink can penetrate the part (the nanoceramic ink isolation layer has a certain thickness, and only the nanoparticles at the ends of the layer penetrate the part and the profiling jig; the nanoceramic ink in the middle does not). After sintering, the resulting metal part exhibits both the ductility of metal and the hardness of ceramic (i.e., the metal surface has a hardness similar to that of ceramic). The high surface hardness of the part effectively prevents scratches. In contrast, the ink isolation layer used in the prior art primarily utilizes large particles, which primarily serve as an isolation function and do not exhibit the same mechanism and effect as the present invention, whereby the nanoparticles penetrate the part and produce functional properties (such as increased hardness).

[0051] It should be noted that:

[0052] (1) In the present invention, alloy is preferably used as the base material of the parts, and nano-ceramic ink is selected as the isolation agent to achieve the purpose of having the same shrinkage ratio and easy separation between the parts and the profiling jig after sintering. At the same time, the hardness of the parts is increased by the penetration of nanoparticles into the parts to form a hard surface layer similar to the ceramic material. In specific implementation, according to actual conditions, different metal (or alloy) materials can be selected for the parts, and the isolation agent can be selected from nano-ceramic ink or metal (or alloy) that cannot be melted together with the parts; if the parts are ceramic materials, the solid material in the nano-ink can be metal (or alloy) or other types of ceramics that cannot be sintered together with the parts. That is, the solid material in the isolation agent is different from the parts and cannot be sintered together with the parts. The selection of other similar mechanisms other than the present invention does not deviate from the mechanism and essence of the present invention and falls within the scope of protection of the present invention.

[0053] (2) The profiling jig in the present invention can be reused, that is, when producing parts of homogeneous quality and consistent curvature (or consistent structural form), it is only necessary to inject the parts in the injection molding step without preparing the profiling jig, thereby saving production costs and reducing resource waste.

[0054] Furthermore, in the coating step:

[0055] Nano-ceramic ink is made of nano-ceramic powder mixed with anhydrous ethanol and additives;

[0056] The nano ceramic powder is nano-aluminum oxide, nano-titanium oxide or nano-titanium nitride, and the particle size of the nano ceramic powder is 20-500nm;

[0057] In nano-ceramic ink, the mass concentration of nano-ceramic powder is 1-20%;

[0058] The additive is one or more of oleic acid, stearic acid and PVP;

[0059] The drying method is to dry in air for 10-30 minutes.

[0060] Furthermore, the preparation method of nano-ceramic ink is: adding nano-ceramic powder and additives to anhydrous ethanol, fully stirring and ultrasonicating for 20-40 minutes, the ultrasonic frequency is 28-100 khz, and then filtering, and the filtration accuracy is 4.5-5.5 μm.

[0061] Furthermore, in the coating step: the thickness of the nano-ceramic ink coating is 10-100 μm.

[0062] Through the coating step, nano-ceramic ink with nano-particle size is selected and a nano-ceramic ink isolation layer of a certain thickness is applied, which can not only effectively separate the parts and the profiling jig, but also improve the surface hardness of the parts; the nano-ceramic powder is evenly dispersed in anhydrous ethanol with the help of additives through ultrasound to form a suspension solution, and then the appropriate mass concentration is set to facilitate the coating of the nano-ceramic powder ink on the parts and / or profiling jig.

[0063] Furthermore, in the feed preparation step, the alloy is an iron-based alloy or a nickel-based alloy, the alloy powder particle size is 1-25 μm, and the banburying time is 0.8-1.5 hours;

[0064] In parts by weight: the amount of alloy used in the feed is 88%-92%.

[0065] Preferably, the alloys include stainless steel, low alloy steel and die steel, and the stainless steel includes 17-4, 304 and 316.

[0066] As described above, in addition to the preferred alloy materials of the present invention, other metals or alloys can also be prepared using the present invention's preparation method. The finer alloy powders preferred in the present invention have higher sintering activity. Larger particle sizes would require excessively high sintering temperatures, resulting in poor alloy strength. The selection of a specific alloy ratio ensures both mixing and granulation, while also facilitating subsequent degreasing. Therefore, too little mixing can complicate the degreasing process, while too much mixing can make granulation difficult.

[0067] It should be noted that the selection of plastic materials, toughening agents and flow improvers is not limited, and any general materials known to those skilled in the art that can achieve the relevant functions can be used. Among them, the plastic material is the main adhesive.

[0068] Furthermore, in the injection molding step, the temperature of the injection mold is 60°C-120°C, and the temperature of the alloy feed is 170-210°C.

[0069] Furthermore, the degreasing step comprises:

[0070] S1: rinse for 50-70 minutes, degreasing temperature is 100-200℃, acid feeding rate is 1-3g / min;

[0071] S2: Degreasing for 15-30 hours, degreasing temperature is 100-200℃, acid feeding rate is 1-7g / min;

[0072] S3: Rinse for 1-4 hours, the flushing temperature is 100-200℃, and the acid injection amount is 0.

[0073] Degreasing can effectively remove grease and impurities on the surface of parts and profiling jigs.

[0074] Furthermore, the coating method used in the coating step includes spraying or coating, and the sintering step adopts a three-stage sintering process. The present invention preferably adopts a spraying or coating technical solution to facilitate the coating of nano-ceramic ink on parts, parts and profiling jigs, and profiling jigs. In contrast, the present invention does not use shot peening or dip coating because shot peening is only applicable to exposed and unobstructed material surfaces and is difficult to use for surface treatment of complex structures and thin parts. In other words, shot peening has requirements for both part shape and strength; the structural characteristics of the parts and profiling jigs of the present invention do not facilitate the use of dip coating.

[0075] Preferably, in the sintering step: the first stage is sintered under nitrogen, the second stage is pre-sintered under vacuum, and the third stage is sintered under argon.

[0076] Preferably, the first stage sintering temperature is 0-800°C and the sintering time is 10-20 hours;

[0077] The second stage sintering temperature is 800-1100℃ and the sintering time is 1-5 hours;

[0078] The third stage sintering temperature is 1100-1400°C, and the sintering time is 1-10 hours.

[0079] The sintering process is carried out in stages. The first stage primarily removes residual organic matter from the part and / or jig. The second stage is a pre-sintering process, which forms a sintering neck and creates a porous part and / or jig. The third stage densifies the part and / or jig. After sintering, the part and jig are separated, and the nano-ceramic ink isolation layer is removed, resulting in a smooth, hard layer. The base material has a Rockwell hardness of 40-45, and the surface layer has a Rockwell hardness of 52-58.

[0080] The following is an example of a method for preparing a complex MIM part that is homogeneous with a profiling fixture according to the present invention. Example 1

[0081] A method for preparing a complex MIM part of the same quality as a profiling fixture comprises the following steps:

[0082] Feed material preparation steps: 88 parts by weight of 17-4 powder with a particle size of 1 μm and 12 parts by weight of a plastic material, a toughening agent, and a flow improver are added to a mixer and kneaded for 1 hour and pelletized to obtain 17-4 feed material;

[0083] Injection molding step: Use an injection molding machine to inject 17-4 feed into parts and contoured jigs. The injection mold temperature is 90°C and the feed temperature is 190°C.

[0084] Coating step: Apply nano-ceramic ink with a mass concentration of 10% to the contact surface of the part and the profiling jig (i.e., both the part and the profiling jig are coated with nano-ceramic ink), the thickness of the nano-ceramic ink isolation layer is 50 μm, and dry in air for 20 minutes; wherein:

[0085] The nano-ceramic ink was prepared by adding 20nm nano-alumina powder and oleic acid to anhydrous ethanol, stirring thoroughly and ultrasonicating for 30 minutes at a frequency of 70kHz, followed by filtration with a filtration accuracy of 5μm.

[0086] Degreasing step: Use oxalic acid degreasing process to degrease the parts and profiling jigs coated with nano-ceramic ink:

[0087] S1: rinse for 60 minutes, degreasing temperature is 150℃, acid feeding rate is 2g / min;

[0088] S2: Degreasing for 23 hours, degreasing temperature is 150℃, acid feeding rate is 4g / min;

[0089] S3: flushing for 3 hours, flushing temperature is 150℃, acid injection amount is 0;

[0090] Sintering steps: The degreased parts and the profiling jig are placed in a vacuum furnace for sintering. The sintering process adopts a segmented sintering process. The first stage adopts sintering at 0-800℃ under nitrogen for 15 hours; the second stage adopts sintering at 800-1100℃ under vacuum for 3 hours; the third stage adopts sintering at 1100-1400℃ under argon for 6 hours. The part is separated from the profiling jig and the nano-ceramic ink isolation layer is removed to obtain a part with a smooth hard layer. The Rockwell hardness (HRC) of the surface of the part is 56 (the base material of the part is 40). Example 2

[0091] A method for preparing a complex MIM part of the same quality as a profiling fixture comprises the following steps:

[0092] Feed material preparation steps: 90 parts by weight of 304 powder with a particle size of 25 μm and 10 parts by weight of plastic material, toughening agent and flow improver are added to a mixer and kneaded for 1.5 hours and pelletized to obtain 304 feed material;

[0093] Injection molding step: Use an injection molding machine to inject 304 feed material into parts and profiling jigs. The injection mold temperature is 120℃ and the feed temperature is 210℃.

[0094] Coating step: Apply nano-ceramic ink with a mass concentration of 20% to the surface of the part that is to contact the profiling fixture (apply only to the part), with a thickness of the nano-ceramic ink isolation layer of 10 μm, and dry in air for 10 minutes; wherein:

[0095] The nano-ceramic ink was prepared by adding nano-sized titanium oxide powder with a particle size of 500 nm, stearic acid, and PVP to anhydrous ethanol, stirring thoroughly and ultrasonicating for 40 minutes at an ultrasonic frequency of 28 kHz, followed by filtration with a filtration accuracy of 5.5 μm.

[0096] Degreasing step: Use oxalic acid degreasing process to degrease the parts and profiling jigs coated with nano-ceramic ink:

[0097] S1: rinse for 50 minutes, degreasing temperature is 200℃, acid feeding rate is 3g / min;

[0098] S2: Degreasing for 15 hours, degreasing temperature is 200℃, acid feeding rate is 7g / min;

[0099] S3: flushing for 1 hour, flushing temperature is 200℃, acid injection amount is 0;

[0100] Sintering steps: The degreased parts and the profiling jig are placed in a vacuum furnace for sintering. The sintering process adopts a segmented sintering process. The first stage adopts sintering at 0-800℃ under nitrogen for 10 hours; the second stage adopts sintering at 800-1100℃ under vacuum for 5 hours; the third stage adopts sintering at 1100-1400℃ under argon for 10 hours. The part is separated from the profiling jig and the nano-ceramic ink isolation layer is removed to obtain a part with a smooth hard layer. The Rockwell hardness (HRC) of the surface of the part is 58 (the base material of the part is 42). Example 3

[0101] A method for preparing a complex MIM part of the same quality as a profiling fixture comprises the following steps:

[0102] Feed material preparation steps: 92 parts by weight of 316 powder with a particle size of 13 μm and 8 parts by weight of plastic material, toughening agent, and flow improver are added to a mixer and kneaded for 0.8 hours and pelletized to obtain 316 feed material;

[0103] Injection molding step: Use an injection molding machine to inject 316 feed into parts and profiling jigs. The injection mold temperature is 60℃ and the feed temperature is 170℃.

[0104] Coating step: Apply nano-ceramic ink with a mass concentration of 1% to the surface of the profiling jig that is to contact the part (apply only to the profiling jig), with a thickness of the nano-ceramic ink isolation layer of 100 μm, and dry in air for 30 minutes; wherein:

[0105] The nano-ceramic ink was prepared by adding nano-sized titanium nitride powder with a particle size of 260 nm, oleic acid, stearic acid, and PVP to anhydrous ethanol, stirring thoroughly and ultrasonicating for 20 minutes at an ultrasonic frequency of 100 kHz, followed by filtration with a filtration accuracy of 4.5 μm.

[0106] Degreasing step: Use oxalic acid degreasing process to degrease the parts and profiling jigs coated with nano-ceramic ink:

[0107] S1: rinse for 70 minutes, degreasing temperature is 100℃, acid feeding rate is 1g / min;

[0108] S2: Degreasing for 30 hours, degreasing temperature is 100℃, acid feeding rate is 1g / min;

[0109] S3: flushing for 4 hours, flushing temperature is 100℃, acid injection amount is 0;

[0110] Sintering steps: The degreased parts and the profiling jig are placed in a vacuum furnace for sintering. The sintering process adopts a segmented sintering process. The first stage adopts sintering at 0-800℃ under nitrogen for 20 hours; the second stage adopts sintering at 800-1100℃ under vacuum for 1 hour; the third stage adopts sintering at 1100-1400℃ under argon for 1 hour. The part is separated from the profiling jig and the nano-ceramic ink isolation layer is removed to obtain a part with a smooth hard layer. The Rockwell hardness (HRC) of the surface of the part is 52 (the base material of the part is 44).

[0111] In summary, through the technical solution of the present invention, the same part material and profiling jig material are used, and nano-ceramic ink is applied on the contact surface of the part and the profiling jig to form a nano-ceramic ink isolation layer, so that the part and the profiling jig have the same shrinkage ratio and shrinkage temperature. During the sintering process, the part and the profiling jig will not be sintered together and can be easily separated, effectively solving the problem of the part and the profiling jig being sintered together during homogeneous co-firing, thereby ensuring the dimensional accuracy of large-scale, thin-walled, complex MIM parts during sintering; at the same time, the nanoparticles in the nano-ceramic ink can penetrate into the metal parts. The surface of the part is made of the same material as the part, and the metal surface has a hardness similar to that of ceramic material, that is, it has the hard characteristics of ceramic material. The high hardness of the part surface can effectively prevent the part from being scratched; and the curvature of the part and the profiling jig are consistent (or structural form), and the profiling jig can well support the part to achieve the shaping effect; finally, the profiling jig in the present invention is homogeneous with the part and both are prepared by MIM process. Compared with the profiling jig using ceramic (the production cost of ceramic profiling jig is high and pollutes the environment), the production cost is low and it is environmentally friendly.

[0112] Finally, it should be noted that the embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of MIM complex parts homogeneous with a profiling jig, characterized in that: It includes the following steps: Feeding preparation step: adding alloy, plastic material, toughening agent, and fluidity improver into a mixer for mixing and pelletizing to obtain alloy feedstock; Injection molding step: using an injection molding machine to inject the alloy feedstock into parts and a profiling jig; Coating step: coating nano-ceramic ink at least on the surfaces of the parts and / or the profiling jig to be in contact and drying; Debinding step: subjecting the parts and the profiling jig coated with nano-ceramic ink to debinding using an oxalic acid debinding process; Sintering step: combining the debound parts and profiling jig and putting them into a vacuum furnace for sintering to obtain parts with a smooth hard layer.

2. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 1, characterized in that: In the coating step: The nano-ceramic ink is composed of nano-ceramic powder, anhydrous ethanol, and an additive; The nano-ceramic powder is nano-aluminum oxide, nano-titanium oxide, or nano-titanium nitride, and the particle size of the nano-ceramic powder is 20 - 500 nm; In the nano-ceramic ink, the mass concentration of the nano-ceramic powder is 1 - 20%; The additive is one or more of oleic acid, stearic acid, and PVP; The drying treatment method is drying in air for 10 - 30 minutes.

3. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 2, characterized in that: The preparation method of the nano-ceramic ink is: adding nano-ceramic powder and an additive into anhydrous ethanol, fully stirring and ultrasonicating for 20 - 40 minutes, the ultrasonic frequency is 28 - 100 kHz, and then filtering, the filtering accuracy is 4.5 - 5.5 μm.

4. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 1, characterized in that: In the coating step: the coating thickness of the nano-ceramic ink is 10 - 100 μm.

5. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 1, characterized in that: In the feeding preparation step, the alloy is an iron-based series alloy or a nickel-based series alloy, the powder particle size of the alloy is 1 - 25 μm, and the mixing time is 0.8 - 1.5 hours; By weight: in the feedstock, the dosage of the alloy is 88% - 92%.

6. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 5, characterized in that: The alloy includes stainless steel, low alloy steel, and die steel, and the stainless steel includes 17 - 4, 304, and 316.

7. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 1, characterized in that: In the injection molding step, the injection mold temperature is 60°C - 120°C, and the alloy feedstock temperature is 170 - 210°C.

8. The preparation method of MIM complex parts homogeneous with a profiling jig according to claim 1, characterized in that: The debinding step includes: S1: rinsing for 50 - 70 minutes, the debinding temperature is 100 - 200°C, and the acid inlet amount is 1 - 3 g / min; S2: debinding for 15 - 30 hours, the debinding temperature is 100 - 200°C, and the acid inlet amount is 1 - 7 g / min; S3: Rinse for 1 - 4 hours at a rinse temperature of 100 - 200 °C with an acid inlet amount of 0.

9. The preparation method of the MIM complex part homogeneous with the profiling jig according to claim 1, characterized in that: The coating method used in the coating step includes spraying or coating, and the sintering step adopts a three-stage sintering process; In the sintering step: the first stage is sintered under nitrogen, the second stage is pre-sintered under vacuum, and the third stage is sintered under argon.

10. The preparation method of the MIM complex part homogeneous with the profiling jig according to claim 9, characterized in that: The sintering temperature in the first stage is 0 - 800 °C, and the sintering time is 10 - 20 hours; The sintering temperature in the second stage is 800 - 1100 °C, and the sintering time is 1 - 5 hours; The sintering temperature in the third stage is 1100 - 1400 °C, and the sintering time is 1 - 10 hours. After sintering is completed, it is slowly cooled to room temperature.

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