A multi-energy field sintering device and method for high-temperature alloy micro-sintered parts

Abstract

The present invention discloses a multi-energy field sintering device and method for high-temperature alloy micro-sintered parts, belonging to the field of powder metallurgy processing technology, in order to solve the problems existing in the current micro-sintered parts, especially the micro-gear manufacturing method, such as the difficulty in positioning the workpiece, the increase in friction resistance under high temperature environment, the difficulty in demoulding, the loss of mechanical integrity caused by the change of material microstructure, the aggravation of mold wear, and the scale effect. The present invention includes a die assembly, an insulating assembly, an internal insulating sintering mold, a fixed mold, a temperature control system, a conductive voltage head assembly and a vibration device. During sintering, the second phase particle precipitation promotion stage, the recrystallization promotion stage, the uniform growth stage of recrystallized particles, the core toughening stage and the tooth surface hardening stage are carried out. The production efficiency of micro-sintered parts is greatly improved, and the forming and characterization integrated manufacturing of micro-sintered parts is realized, and the peripheral structure performance of the obtained sintered parts is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy processing, and in particular relates to a multi-energy field sintering device and method for high-temperature alloy micro-sintered parts. Background Art

[0002] With the continuous development of micro-equipment manufacturing, the demand for micro-gears in important transmission devices in micro-machines and micro-electromechanical systems is gradually increasing. High-temperature alloy micro-gears are made of high-temperature alloys and have the advantages of high strength, good toughness, strong wear resistance, corrosion resistance, oxidation resistance, and high thermal stability. They are widely used in important fields such as micro-aircraft, micro-underwater equipment, and micro-manufacturing equipment.

[0003] Compared with traditional large gears, micro gears have small size and high processing precision requirements, especially the gear teeth, which cannot be cut by traditional large gear processing tools. In addition, the processing of micro gears also has the problem of difficult workpiece positioning. In addition, high-temperature alloys need to be formed at higher temperatures. The increased friction resistance in high temperature environments makes demolding difficult, changes in material microstructure cause loss of mechanical integrity, increased mold wear, scale effects and many other problems seriously affect product quality and cannot guarantee the formation of micro gears. Integrated manufacturing.

[0004] Patent CN114653941A discloses a powder metallurgy method for nickel-titanium alloy gears, but due to the unclear sintering mold device and the lack of a sintering method for ordinary-sized gears, the processing accuracy and mechanical properties of micro-gears cannot be guaranteed. Patent CN108411231A uses pulse current to perform aging treatment on nickel-based high-temperature alloys to improve the microstructure of the alloy. Patent CN111809128A uses pulse current to quickly dissolve the low-melting-point Laves phase in the deformed nickel-based high-temperature alloy ingot, while avoiding the initial melting of the Laves phase to hinder the diffusion of segregated element atoms. However, in the above-mentioned patents, when multi-energy fields are used to assist in the sintering of high-temperature alloys, the sintering mold and powder are energized. Since the resistance of the sintering mold is much smaller than that of the powder, most of the current passes through the mold after power-on, resulting in a very limited effect of the current on the powder. Summary of the invention

[0005] In view of the above problems, the invention provides a multi-energy field sintering device and method for high-temperature alloy micro-sintered parts, which solves the technical problems of low dimensional accuracy, uneven microstructure, poor mechanical properties and slow integrated forming manufacturing speed of high-temperature alloy micro-sintered parts manufactured in the prior art.

[0006] On the one hand, the present invention discloses a multi-energy field sintering device for high-temperature alloy micro-sintered parts, comprising a die assembly, an insulating assembly, an internal insulating sintering mold, a fixed mold, a temperature control system, a conductive voltage head assembly and a vibration device; the die assembly is used to pressurize and conduct current on high-temperature alloy powder; the internal insulating sintering mold is used to contain high-temperature alloy powder; the fixed mold is used to fix the internal sintering mold; the temperature control system is used to control the temperature when processing high-temperature alloy sintered parts; the conductive voltage head assembly is used to provide pressure when processing high-temperature alloy sintered parts; the vibration device is used to provide vibration when processing high-temperature alloy sintered parts;

[0007] The die assembly includes a first die and a second die;

[0008] The inner sintering mold includes a first sintering mold half and a second sintering mold half;

[0009] The insulating assembly includes a first semi-insulating frame and a second semi-insulating frame;

[0010] The conductive voltage head assembly includes a first conductive voltage head and a second conductive voltage head;

[0011] Wherein, the insulating component is arranged between the die component and the internal sintering mold.

[0012] Optionally, the first semi-insulating frame and the second semi-insulating frame are both sheets.

[0013] Optionally, the internal sintering mold, the fixed mold and the insulating component are respectively provided with a first through hole, a second through hole and a third through hole.

[0014] Optionally, a vacuum system and a pressure control system are also included.

[0015] On the other hand, the present invention also discloses a method for multi-energy field sintering of high-temperature alloy micro-sintered parts, using the multi-energy field sintering device for high-temperature alloy micro-sintered parts, and the specific steps include: after installing the sintering device, filling the powder raw material into the sintering device, and using the die assembly for initial compaction; vacuum treatment of the sintering device;

[0016] Sintering includes the stage of promoting the precipitation of second phase particles, the stage of promoting the nucleation of recrystallization, the stage of uniform growth of recrystallized grains, the stage of core toughening and the stage of surface hardening of sintered parts.

[0017] Optionally, during the second phase particle precipitation stage, a pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 50-60 MPa; the temperature is increased at a rate of 100-150°C / min to 850-950°C and kept at this temperature for 15-20s.

[0018] Optionally, in the recrystallization nucleation promotion stage, vibration is initiated after the second phase particle precipitation stage ends, the vibration frequency is 15 to 20 kHz, the amplitude range is 1.5 to 2 μm, and at the same time, the conductive voltage head assembly applies pressure to the powder raw material along the axial direction of the sintering device and maintains it at 70 to 80 MPa, the temperature is 880 to 980°C, and the temperature is kept for 10 to 20 seconds.

[0019] Optionally, in the stage of uniform growth of recrystallized grains, after the recrystallization nucleation promotion stage ends, the current intensity is increased to a heating rate of 200-250°C / min to reach 1050-1100°C, the vibration frequency is reduced to 10-15kHz, and the temperature is kept warm for 20-30s. At the same time, pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 60-70MPa.

[0020] Optionally, in the core toughening stage, after the uniform growth stage of recrystallized grains is completed, the vibration source is turned off, the axial pressure is maintained at 70-80 MPa, and the current is unloaded at a rate of 10-30°C / min to cool the internal structure to 500-600°C.

[0021] Optionally, in the sintered part surface hardening stage, after the core toughening stage is completed, the current is unloaded at a rate of 80-100° C. / min, and the temperature control system is turned on to cool the sintering device to room temperature.

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

[0023] (1) The sintering device of the present invention can apply a multi-energy field to perform one-time forming and sintering to manufacture micro gears. There is no need for shifting operations of different processing steps and no need for clamping molds, which simplifies the installation and manufacturing process and avoids many problems such as loss of mechanical integrity, increased mold wear, and scale effect caused by multiple processing steps, thereby greatly improving manufacturing efficiency.

[0024] (2) The outer contour of the internal sintering mold cavity of the present invention is provided with a conical surface at 0-2 / 3 of the length from top to bottom along the axial direction, which is convenient for positioning and demolding; a positioning spherical curved surface is provided at 2 / 3-5 / 6 of the length, the upper part of the spherical curved surface is tangent to the conical surface, and the lower part terminates at 5 / 6 of the length. The spherical curved surface can give the sintering mold flexibility, so that it can be adaptively positioned, reducing the difficulty of positioning. During the sintering process, after the internal sintering mold cavity is subjected to axial pressure, the adaptive positioning of the spherical curved surface can also ensure that the sintering pressure is always applied along the central axis, effectively enhancing the sintering stability of the sintered body, and preventing mold breakage and sintering failure caused by sintering pressure deviation. In addition, the spherical curved surface structure of the internal sintering mold cavity also facilitates the separation of the insulating frame from the internal sintering mold cavity; the remaining length is a cylindrical surface.

[0025] (3) The insulating frame of the sintering device of the present invention is composed of two semi-insulating frames with exactly the same geometric shape. The insulating frame is made of insulating material. Its main function is to isolate the sintering workpiece and the mold, so that the current flows completely from the die into the powder to be sintered, ensuring that the inside of the powder is fully affected by the Joule heating effect and electroplastic effect of the current, and does not affect the high-temperature mechanical properties of the sintering cavity. The outer surface of the insulating frame is a conical surface, and the generatrix of the outer surface of the conical surface is at an angle of 8-12° to the central axis. As the pressure is loaded along the axial direction of the cone, the conical surface of the insulating frame is positioned and matched with the sintering inner mold cavity, which can reduce the difficulty of positioning and improve the positioning accuracy; in addition, the conical surface limits the radial displacement of the two semi-insulating frames, ensuring that the insulating frame can gradually clamp the self-locking sintered body during the sintering process, avoiding powder overflow.

[0026] (4) The present invention uses electric field and ultrasonic vibration field to assist sintering to manufacture micro gears. The current passes through the powder particles, generating resistance heat and plasma discharge heat between the contact surfaces of the particles, which greatly promotes atomic diffusion on the contact surface and metallurgical bonding between particles, greatly reduces microstructure defects, and ensures that the micro gears have good dimensional accuracy. The ultrasonic field can effectively promote the recrystallization nucleation with the second phase particles as the core, homogenize the microstructure of the micro gear, improve the comprehensive mechanical properties, and realize the forming and integration of micro gears with a base circle diameter in the range of 0.5 to 1 mm.

[0027] (5) The present invention promotes the rapid hardening of the micro gear tooth surface by controlling the unloading process of the current, thereby effectively improving the tooth surface hardness.

[0028] (6) The sintering method of the present invention utilizes a sintering device to perform an electric field and ultrasonic vibration field assisted sintering method to manufacture micro gears. By controlling the current intensity, sintering temperature, and the frequency and amplitude of the ultrasonic vibration field, dynamic recrystallization is stimulated to promote the integrated forming of the micro gear shape.

[0029] (7) The present invention arranges an array of microstructures on the surface of the insulating frame in contact with the powder to facilitate the demolding of the workpiece from the mold after sintering. The characteristic size of a single microstructure is 10-20 μm, which has the advantages of no powder sticking and easy demolding of the workpiece after sintering compared with the irregular surface of the traditional mold.

[0030] (8) The present invention utilizes an insulating component to insulate the sintering die from the powder raw material during multi-energy field assisted sintering, and transmits current to the powder only through the die, thereby ensuring the Joule heating effect and electroplastic effect of the current in the powder particles, improving the vacancy density, and greatly increasing the frequency of atoms entering nearby vacancies. In combination with the "electron wind effect" generated by the electric field, the atomic diffusion is significantly improved, the temperature is increased in a short time, and the heating and pressurization are uniform. While ensuring the acquisition of high-density materials, the grains are refined, the sintering defects are reduced, the material strength is improved, the quality of the sintered body is effectively improved, and the forming process of the nickel-based high-temperature alloy gears is simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of a sintering device of the present invention;

[0032] Figure 2 It is a schematic diagram of assembling the die assembly and the internal sintering mold of the sintering device of the present invention;

[0033] Figure 3 is a cross-sectional schematic diagram of a sintering device of the present invention;

[0034] Figure 4 It is a multi-field energy schematic diagram of the sintering device of the present invention;

[0035] Figure 5 A schematic diagram of the array microstructure on the inner surface of the insulating frame of the sintering device of the present invention;

[0036] Figure 6 The microstructure information of the nickel-based high-temperature alloy micro-gear sintered by the sintering device and method of the present invention;

[0037] Figure 7 The microstructure information of the nickel-based high-temperature alloy micro-gear made for comparative case 1;

[0038] Figure 8 The microstructure information of the nickel-based high-temperature alloy micro-gear made for comparative case 2;

[0039] Fig. 9 The microstructure information of the nickel-based high-temperature alloy micro-gear made for comparative case 3;

[0040] Fig.10 Microstructure information of nickel-based high-temperature alloy micro gear made for comparison case 4.

[0041] Description of reference numerals:

[0042] 1-first punching die; 2-second punching die; 3-first sintering half-mold; 4-second sintering half-mold; 5-first semi-insulating frame; 6-second semi-insulating frame; 7-fixed mold; 8-first through hole; 9-second through hole; 10-powder raw material; 11-thermocouple; 12-power supply; 13-temperature control system; 14-vacuum system; 15-first conductive voltage head; 16-second conductive voltage head; 17-pressure control system; 18-vibration device. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be described clearly and completely below. The described embodiments are only some embodiments of the present invention, not all embodiments. It should be understood that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on it. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Multi-energy field sintering device and method for high-temperature alloy micro-gears

[0044] One embodiment of the present invention, see Figure 1-10 , provides a multi-energy field sintering device for high-temperature alloy micro-sintered parts, including a die assembly, an insulating assembly, an internal insulating sintering die and a fixed die; the die assembly is used to pressurize the high-temperature alloy powder and conduct current; the internal insulating sintering die is used to contain the high-temperature alloy powder; the fixed die is used to fix the internal sintering die;

[0045] The die assembly comprises a first die 1 and a second die 2;

[0046] The internal insulating sintering mold comprises a first sintering half mold 3 and a second sintering half mold 4;

[0047] The insulating assembly comprises a first semi-insulating frame 5 and a second semi-insulating frame 6;

[0048] The outer walls of the first sintering half mold 3 and the second sintering half mold 4 are conical surfaces at 0-2 / 3 of the length from top to bottom along the central axis of the sintering mold, and the generatrix of the conical surface is 8-12 degrees with the central axis; the outer walls of the first sintering half mold 3 and the second sintering half mold 4 are spherical surfaces at 2 / 3-5 / 6 of the length from top to bottom along the central axis, the upper part of the spherical surface is tangent to the lower end surface of the conical surface, the center of the spherical surface is located on the central axis of the sintering mold, and the radius of the spherical surface is twice the diameter of the sintered part; the bottom of the outer wall of the first sintering half mold 3 and the second sintering half mold 4 is a cylindrical surface; the inner wall of the first sintering half mold 3 and the second sintering half mold 4 is a conical surface, and the generatrix of the conical surface is 8-12 degrees with the central axis.

[0049] Preferably, the sintered part is a micro gear.

[0050] The insulating component used in the present invention ensures that all current passes through the high-temperature alloy powder raw material instead of passing through the internal insulating sintering mold and the fixed mold, so that the heat is concentrated in the high-temperature alloy powder raw material; in addition, the outer wall of the insulating component is a conical surface, and its outer surface is 8-12° with the central axis, which is positioned with the conical surface of the inner wall of the first sintering half mold 3 and the second sintering half mold 4 to reduce the difficulty of positioning; in addition, the conical surface limits the radial displacement of the two semi-insulating frames, ensuring that the insulating frames can gradually clamp the sintered body during the sintering process, avoiding powder overflow, and ensuring the heating rate and sintering temperature of the high-temperature alloy powder raw material during the sintering process, thereby improving the processing accuracy, and processing high-temperature alloy micro-sintered parts with a base circle diameter between 0.5 and 1 mm, and a dimensional accuracy of ±5μm. See attached Figure 5 An array of microstructures is arranged at the position where the inner wall surface of the insulating component contacts the powder raw material. The size of each microstructure is 10-20 μm, and the shape of the microstructure is circular (diameter is 10-20 μm) and / or square (side length is 10-20 μm) and / or square cone (side length is 10-20 μm). This can achieve non-stick powder and prevent the appearance of holes in the sintered parts during the sintering process. In addition, it can also facilitate the demolding of the workpiece after sintering.

[0051] Optionally, when the array microstructures include square cones, square blocks and circles, the three shapes are distributed in regions from top to bottom along the central axis, and the areas of the distribution regions are the same.

[0052] The sintering device of the present invention further comprises a temperature control system 13, a conductive voltage head assembly and a vibration device 18; the conductive voltage head assembly comprises a first conductive voltage head 15 and a second conductive voltage head 16;

[0053] The temperature control system 13 is used to control the temperature when processing the high-temperature alloy sintered parts;

[0054] The conductive voltage head assembly is used to provide pressure when processing high-temperature alloy sintered parts;

[0055] The vibration device 18 is used to provide vibration when processing the high-temperature alloy sintered part;

[0056] Optionally, the first conductive voltage head 15 is used to apply pressure to the first die 1; the second conductive voltage head 16 is used to apply pressure to the second die 2; preferably, see Figure 4 The first conductive voltage head 15 is arranged on the outer side of the lower end of the first punch die 1 , and the second conductive voltage head 16 is arranged on the outer side of the top end of the second punch die 2 .

[0057] Optionally, the vibration device 18 is an ultrasonic vibration device.

[0058] Optionally, the first punch 1 is a short punch, and the second punch 2 is a long punch. The shaft length of the short punch is 2 to 3 times the base circle diameter of the cross section of the sintered part, and the shaft length of the long punch is 10 to 12 times the base circle diameter of the cross section of the sintered part. Therefore, the short punch has a short slideway when sliding with the insulating frame and the sintering mold cavity, which is easy to fully match, and the long punch can control the sintering displacement, thereby improving the accuracy of the outer wall shape of the sintered part; further, the powder raw material area is located at the intersection of the spherical surface and the cylindrical surface of the first sintering half mold 3 and the second sintering half mold 4, further reducing the difficulty of demolding. The cross-sectional shape of the first punch 1 and the second punch 2 perpendicular to the axial direction is the same as the cross-sectional shape of the sintered part; optionally, it is a gear shape, which is completely consistent with the geometric characteristics of the cross section of the micro gear perpendicular to the axial direction after sintering; the materials of the first punch 1 and the second punch 2 have high strength and good electrical conductivity, and are respectively inserted into the internal sintering mold cavity and contacted with the conductive voltage head assembly.

[0059] Preferably, the material of the die assembly is graphite.

[0060] Optionally, the inner side surfaces of the first sintering half mold 3 and the second sintering half mold 4 are fitted together to form an internal sintering mold; half-mold inner through holes are arranged on the inner side surfaces of the first sintering half mold 3 and the second sintering half mold 4 along the axial direction of the micro sintered part, and the two half-mold inner through holes form the sintering mold inner through holes of the internal sintering mold; preferably, the cross-sectional shape of the cavity formed by the inner wall of the sintering mold inner through hole composed of the two semicircular inner through holes is the same as the cross-sectional shape of the die assembly;

[0061] It is understandable that when the sintered part is a micro gear, the tooth shape of the cavity cross section formed by the inner wall of the through hole in the sintering mold is the same as the tooth shape of the die assembly, and the die assembly can slide in the through hole in the sintering mold.

[0062] Preferably, the material of the first sintering half mold 3 and the second sintering half mold 4 is graphite, which can ensure the hardness and strength of the mold under high temperature processing conditions during sintering.

[0063] Preferably, the outer contour of the inner sintering mold is in the shape of a truncated cone.

[0064] Optionally, the first semi-insulating frame 5 and the second semi-insulating frame 6 are both sheets; when in use, the two end edges of the sheets of the first semi-insulating frame 5 and the second semi-insulating frame 6 are correspondingly fitted to form a sintering inner cavity; the sheets of the first semi-insulating frame 5 and the second semi-insulating frame 6 are respectively arranged along the axis direction of the micro-gear to form a tooth shape that is completely consistent with the geometric features of the teeth of the micro-gear after sintering; the die assembly can slide in the sintering inner cavity; the height of the insulating assembly is the same as the height of the internal sintering mold; the insulating assembly is made of electrical insulating material; the first semi-insulating frame 5 and the second semi-insulating frame 6 are located between the die assembly and the first sintering half mold 3 and the second sintering half mold 4, and are used to form an electrical insulator between the powder raw material 10 and the internal sintering mold, ensuring that the current is fully passed into the powder, and no energy is consumed on the sintering mold, which can ensure the sintering temperature and temperature control efficiency of the high-temperature alloy. In addition, the presence of the insulating frame makes it easy to demold the sintered body after forming.

[0065] Preferably, the material of the insulating component is aluminum oxide.

[0066] Optionally, the internal sintering mold and the insulating component are respectively provided with a first through hole 8 and a third through hole along the direction perpendicular to the axis of the micro gear; after the sintering device is installed, the first through hole 8 and the third through hole are connected; the third through hole is arranged corresponding to the position where the powder raw material 10 is placed. Preferably, the first through hole 8 and the third through hole are respectively arranged on the sintering half mold and the semi-insulating frame on the same side.

[0067] The installation method of the internal sintering mold is as follows: first, the first semi-insulating frame 5 and the second semi-insulating frame 6 are respectively inserted along the corresponding first sintering half mold 3 and the second sintering half mold 4, and then the two first sintering half molds 3 and the second sintering half molds 4 respectively inserted with the semi-insulating frames are slidably matched with the short punch using the toothed geometric features to form a complete internal sintering mold cavity.

[0068] When the sintering aid device of the present invention is in use, the current is only energized between the conductive voltage head assembly and the powder raw material, thereby ensuring the Joule heat effect and electroplastic effect of the current inside the sintered body and preventing short circuit.

[0069] Optionally, the fixed mold is provided with a receiving hole along the axial direction, the inner wall shape of the receiving hole is the same as the outer wall shape of the internal insulating sintering mold, and is used to receive the internal insulating sintering mold; the fixed mold is a cylinder; the material of the fixed mold has high strength and hardness.

[0070] Preferably, the receiving hole is arranged at the geometric center position of the fixed mold.

[0071] Optionally, a second through hole 9 is provided on the fixed mold along the direction perpendicular to the axis of the micro gear, and the first through hole 8, the second through hole 9 and the third through hole are provided correspondingly, and the three through holes are connected; the third through hole is provided correspondingly to the position of the powder raw material. When the internal sintering mold cavity is matched with the fixed mold, the thermocouple is inserted into the three aligned through holes, and the thermocouple is connected to the temperature control system.

[0072] Preferably, the stent is graphite.

[0073] Optionally, it also includes a thermocouple 11 , a power supply 12 , a vacuum system 14 and a pressure control system 17 .

[0074] The thermocouple 11 is inserted into the first through hole, the second through hole and the third through hole, one end of which is connected to the temperature control system 13 and the other end is in contact with the powder raw material. The temperature control system 13 is used to detect the temperature of the powder raw material in real time during the preparation process and adjust the temperature of the preparation process.

[0075] The power supply 12 is used to provide energy to the sintering device.

[0076] The vacuum system 14 is used to detect the vacuum degree of the device during the preparation process in real time and adjust the vacuum degree of the preparation process.

[0077] The pressure control system 17 is used to detect the axial pressure of the conductive voltage head assembly in real time during the preparation process and adjust the pressure value of the preparation process.

[0078] Optionally, the powder raw material 10 is nickel-based high-temperature alloy powder.

[0079] In another aspect, the present invention further provides a multi-energy field sintering method for high-temperature alloy micro-sintered parts, using the above-mentioned multi-energy field sintering device for high-temperature alloy micro-sintered parts, specifically comprising the following steps:

[0080] Install the sintering device; after installing the sintering device, use lubricant to lubricate the internal sintering cavity and the die assembly; the cross-sectional diameter of the internal sintering cavity and the die assembly is 0.5-1mm, and the sintering device is installed for sintering micro sintered parts with a diameter of 0.5-1mm and a thickness of 0.2-0.5mm.

[0081] Preferably, the axial length of the short punch is 2.5 times the base circle diameter of the cross section of the sintered part, and the axial length of the long punch is 12 times the base circle diameter of the cross section of the sintered part; a micro sintered part with a diameter of 0.8 mm and a thickness of 0.5 mm is processed.

[0082] 0.255 g to 2.85 g of the powdered raw material 10 is filled into the sintering device and initially compacted using a punch assembly; the sintering device is subjected to vacuum treatment;

[0083] Sintering includes the stage of promoting the precipitation of second phase particles, the stage of promoting the nucleation of recrystallization, the stage of uniform growth of recrystallized grains, the stage of core toughening and the stage of surface hardening of sintered parts.

[0084] The micro-gear prepared by the method has uniform internal grain refinement and good mechanical properties, a yield strength of more than 400 MPa, a tooth surface hardness of more than 65 HRC, and an elongation of more than 60%.

[0085] Preferably, the sintering device is vacuum treated to 10 -3 Pa or less; the lubricant is zinc stearate acetone emulsion.

[0086] Optionally, high-temperature alloy powder is filled into a sintering device and initially compacted using a die assembly; the sintering device is vacuum-treated, and the specific steps are: the powder raw material 10 is canned in a complete sintering cavity that has been formed by tooth-shaped geometric features; the second die 2 is inserted into the complete sintering cavity from the top; the first through hole, the second through hole and the third through hole are aligned, and a thermocouple 11 is inserted into the aligned through holes, and the thermocouple 11 is connected to the temperature control system 13; the pressure control system 17 is turned on to control the conductive voltage head assembly to initially compact the powder, and the conductive voltage head assembly applies pressure to the powder raw material along its axial direction and maintains the pressure at 10 to 20 MPa; the ultrasonic vibration control system 18 is turned on to vibrate the loose powder raw material; the vacuum system 14 is turned on to vacuum-treat the complete sintering cavity.

[0087] Preferably, the vacuum degree of the complete sintering cavity is 10 -3 The conductive voltage head applies pressure to the powder raw material along its axial direction and maintains the pressure at 15MPa.

[0088] Optionally, in the second phase particle precipitation stage, a pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 50-60 MPa, preferably, the pressure is maintained at 55 MPa; an electric current is connected through the thermocouple 11, and the temperature is increased at a rate of 100-150°C / min to 850-950°C, and the temperature is kept for 15-20s, so that the powder raw material is in a dynamic recrystallization state, thereby promoting the precipitation of γ' phase (i.e., spherical compounds with a face-centered cubic crystal structure) and γ" phase (i.e., disc-shaped compounds with a body-centered tetragonal structure) particles; preferably, the temperature is increased at a rate of 140°C / min to 900°C, and the temperature is kept for 18s, and the connected current is a pulse current or an alternating current.

[0089] Optionally, in the recrystallization nucleation promotion stage, after the second phase particle precipitation stage ends, vibration is connected, the vibration frequency is 15-20kHz, the amplitude range is 1.5-2μm, and at the same time, the conductive voltage head assembly applies pressure to the powder raw material along the axial direction of the sintering device and maintains it at 70-80MPa, the temperature is 880-980℃, and the temperature is kept for 10-20s, so that it recrystallizes and nucleates with the second phase particles as the core; preferably, the connected vibration is ultrasonic vibration, the vibration frequency is 18kHz, the amplitude is 1.8μm, and pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 75MPa, the temperature is 975℃, and the temperature is kept for 15s.

[0090] Optionally, in the stage of uniform growth of recrystallized grains, after the recrystallization nucleation promotion stage is ended, the current intensity is increased to 1050-1100°C at a heating rate of 200-250°C / min, the vibration frequency is reduced to 10-15kHz, and the temperature is kept warm for 20-30s. At the same time, pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 60-70MPa to promote uniform grain growth and make the internal structure of the micro gear highly toughened; preferably, the temperature is increased to 1050°C at a heating rate of 220°C / min, the vibration frequency is adjusted to 10kHz, and the temperature is kept warm for 25s, and pressure is applied to the high-temperature alloy powder along the axial direction of the sintering device and maintained at 65MPa.

[0091] Optionally, in the core toughening stage, after the uniform growth stage of recrystallized grains ends, the vibration source is turned off, the axial pressure is maintained at 70-80MPa, and the current is slowly unloaded at a rate of 10-30°C / min, so that the internal structure is slowly cooled to 500-600°C, which can improve the toughness of the gear core; preferably, the axial pressure is maintained at 75MPa, the current is slowly unloaded at a rate of 15°C / min, and the internal structure is slowly cooled to 550°C.

[0092] Optionally, in the sintered part surface hardening stage, after the core toughening stage is completed, the current is quickly unloaded at a rate of 80-100°C / min, and the temperature control system is turned on to quickly cool the sintering device to room temperature. At the same time, the pressure is unloaded to quickly harden the surface of the micro-sintered part with a diameter of 0.5-1mm to complete the sintering, thereby improving the sintered part surface hardness of the sintered micro-sintered part. After the sintered part surface hardening stage is completed, the vacuum is unloaded, the sintering mold containing the micro-sintered body is taken out and demolded.

[0093] In order to facilitate understanding of the above technical solution of the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment case.

[0094] The above-mentioned sintering device and sintering method are used to form a nickel-based high-temperature alloy micro gear with a base circle diameter of 0.8mm and a thickness of 0.2mm. The base circle diameter of the first punch 1 is 0.8mm, the length is 2mm, and the material is graphite; the base circle diameter of the second punch 2 is 0.8mm, the length is 8mm, and the material is graphite. The outer contour of the two sintering half molds is a conical surface at 0-2 / 3 from top to bottom along its length direction, the diameter of the top large circle is 4mm, the inclination of the cone generatrix is ​​8°, and a spherical surface is provided from 2 / 3 to 5 / 6 of the axial length. The radius of the spherical surface is 1.6mm, and it is a cylinder from 5 / 6 of the axial length to the bottom, and the diameter of the cylindrical section is 2mm. The material is graphite. Specifically comprising the following steps:

[0095] Matching of the sintering device: lubricate the first sintering half mold 3, the second sintering half mold 4, the first insulating frame, the inner wall of the second insulating frame and the die with zinc stearate acetone emulsion, slide the first sintering half mold 3 with the first insulating frame through the gear tooth shape, and then slide with the first die 1 through the gear tooth shape; slide the second sintering half mold 4 with the second insulating frame through the conical surface, and then slide with the first die 1 through the gear tooth shape to form a complete sintering inner mold cavity.

[0096] Filling 6g of nickel-based high-temperature alloy powder: Fill the nickel-based high-temperature alloy powder into the complete sintering mold cavity that has been formed by the tooth-shaped geometric features, and insert the second punch 2 into the mold cavity from the top. Align the first through hole 8 on the semi-insulating frame, the second through hole 9 and the third through hole on the fixed mold, insert the thermocouple 11 into the aligned through holes, and connect the thermocouple 11 to the temperature control system 13.

[0097] Pressurization and compaction of nickel-based high-temperature alloy powder: Open the pressure control device 17 to compact the powder preliminarily; the conductive voltage head assembly applies pressure to the powder raw material along its axial direction and maintains the pressure at 15MPa; open the ultrasonic vibration control system 18 to compact the loose powder. Open the vacuum system 14 to vacuum the complete sintering cavity. The vacuum degree of the complete sintering cavity is 10 -3 Below Pa.

[0098] Second phase particle precipitation promotion stage: connect the two ends of the power supply 12 to the electrodes respectively, turn on the power supply 12 and the temperature control system 13, apply pressure to the powder raw material along the axial direction of the sintering device and maintain it at 55MPa, and reach the dynamic recrystallization temperature of 910℃ at a heating rate of 120℃ / min, and keep it warm for 18s to promote the precipitation of γ' phase and γ" phase particles.

[0099] Recrystallization particle nucleation promotion stage: connect the ultrasonic vibration control system 18, the vibration frequency is 18kHz, the amplitude range is 1.7μm; adjust the power supply 12, control the sintering of the nickel-based high-temperature alloy powder at 975℃; and maintain the sintering axial pressure of 75MPa, and keep the temperature and pressure for 15s. This stage promotes the recrystallization nucleation with the second phase particles as the core.

[0100] Uniform growth stage of recrystallized grains: adjust the power supply 12 to reach 1080°C at a heating rate of 220°C / min, adjust the vibration frequency of the ultrasonic vibration control system 18 to 13kHz, keep warm for 25s, apply pressure to the powder along its axial direction and maintain it at 65MPa to promote uniform growth of grains and make the internal structure of the micro gear highly toughened.

[0101] Core toughening stage: turn off the ultrasonic vibration system 18 and maintain the axial pressure at 75MPa. Adjust the power supply 12, slowly unload the current at a rate of 20℃ / min, observe the temperature control system and the control system 13, and slowly cool the internal structure to 600℃ to ensure the toughness of the gear core.

[0102] Tooth surface hardening stage: Then adjust the power supply 12, observe the temperature control system 13, quickly unload the current at a rate of 100°C / min, and keep the temperature control system 13 turned on to drop to room temperature, so that the micro gear tooth surface is quickly hardened to ensure the tooth surface hardness.

[0103] The microstructure information of nickel-based high-temperature alloy micro gears made after sintering is as follows: Figure 5 As shown. The micro gears manufactured by spark plasma sintering technology have good density and fewer internal defects, which reduces the material quality problems caused by the internal defects of the original high-temperature alloy blank. It shows that the multi-energy field assisted sintering device and method of the high-temperature alloy micro gear of the present invention can manufacture high-temperature alloy gears with uniform structure and good performance.

[0104] Comparative Case 1: Microstructure information of nickel-based high-temperature alloy micro gears Figure 6 As shown, a micro gear with the same geometric features as the implementation case is sintered by a hot pressing furnace without current connection. Due to the functional limitations of the hot pressing furnace, it enters a heat preservation and pressure holding state after heating and pressure increase, and the pressure and temperature cannot be changed during the sintering process. Therefore, the sintering process is:

[0105] Pressurization of nickel-based high-temperature alloy powder: The complete sintering cavity is vacuum treated, and the vacuum degree of the complete sintering cavity is 10 -3 Pa, and apply axial pressure to the powder to 75MPa.

[0106] Heating of nickel-based high-temperature alloy powder: at a heating rate of 120°C / min, reaching a dynamic recrystallization temperature of 1050°C, and keeping the temperature for 60s.

[0107] Cooling stage: Shut down the sintering equipment and allow the sintered body to cool down with the furnace.

[0108] Comparative Case 2: Microstructure information of nickel-based high-temperature alloy micro gears Figure 7 As shown, the sintering half mold is directly matched with the punching die without placing an insulating frame in the middle, and other conditions are exactly the same as those in the implementation case.

[0109] Comparative Case 3: Microstructure information of nickel-based high-temperature alloy micro gears Figure 8 As shown, the sintering device is exactly the same as that of the implementation case, and the sintering process is the same as that of comparative case 1.

[0110] Comparative Case 4: Microstructure information of nickel-based high-temperature alloy micro gears Fig. 9 As shown, the sintering device is exactly the same as that in the implementation case, ultrasound is not set in the sintering process, and the rest is the same as that in the implementation case.

[0111] The core of the sintered body of the implementation case and comparative case 1, comparative case 2, comparative case 3 and comparative case 4 was cut open along the axial plane, and the samples were selected for scanning electron microscope microscopic analysis, respectively. Figure 5-9 shown. Figure 5 The microstructure is uniform, the density is high, the sintering neck is basically formed, and there are almost no sintering defects. Figure 6 In contrast, in case 1, no effective metallurgical bonding was formed between the particles, and sintering failed, proving that multi-energy field sintering is very effective in improving density. Figure 7 In contrast, in case 2, no effective metallurgical bonding was formed between the particles, and sintering failed, indicating that most of the current passed through the mold and the sintering temperature between the powders did not reach an effective value. Figure 8 In contrast, case 3 has better density and sufficient metallurgical bonding between particles, but has many sintering defects. Fig. 9 In case 4, the density is further improved and the sintering defects are significantly reduced, but there are still many defects, which shows that ultrasonic vibration plays a key role in reducing defects and improving density. Compared with the microstructures of the four comparative cases, the high-temperature alloy sintered body manufactured by the sintering device and sintering method of the present invention has extremely high density and almost no defects, which shows that the present invention can complete the shape-integrated sintering of micro gears.

[0112] In addition, tensile tests and microhardness tests were performed on the sintered bodies of the above five cases. The results are shown in Table 1, which proves that the high-temperature alloy sintered bodies sintered using the device and process of the present invention have good mechanical properties.

[0113] Table 1 Mechanical properties of implementation cases and comparison cases

[0114] Yield Strength tensile strength hardness Implementation Cases 552MPa 1300MPa 433Hv Comparative Case 1 none 100MPa 185Hv Comparative Case 2 none 130MPa 222Hv Comparative Case 3 406MPa 800MPa 321Hv Comparative Case 4 451MPa 1010MPa 387Hv

[0115] In summary, the present invention is a method for preparing nickel-based high-temperature alloy gear parts by pulse current assisted sintering, which can effectively control grain growth, reduce hard second phase particles and microstructure defects, and quickly prepare nickel-based high-temperature alloy gears with excellent mechanical properties.

[0116] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A multi-energy field sintering device for high-temperature alloy micro-sintered parts, characterized in that: It includes a die assembly, an insulating assembly, an internal sintering die, a fixed die, a temperature control system, a conductive voltage head assembly and a vibration device; the die assembly is used to pressurize the high-temperature alloy powder and conduct current; the internal sintering die is used to contain the high-temperature powder raw material; the fixed die is used to fix the internal sintering die; the temperature control system is used to control the temperature when processing the high-temperature alloy sintered parts; the conductive voltage head assembly is used to provide pressure when processing the high-temperature alloy sintered parts; the vibration device is used to provide vibration when processing the high-temperature alloy sintered parts; The die assembly includes a first die and a second die; The inner sintering mold includes a first sintering mold half and a second sintering mold half; The insulating assembly includes a first semi-insulating frame and a second semi-insulating frame; The conductive voltage head assembly includes a first conductive voltage head and a second conductive voltage head; Wherein, the insulating component is arranged between the die component and the internal sintering die; The outer walls of the first sintering half mold and the second sintering half mold are a conical surface, a spherical curved surface and a cylindrical surface from top to bottom along the central axis of the sintering device; an array microstructure is arranged at a position where the inner wall surface of the insulating component contacts the powder raw material; The diameter of the micro sintered part is 0.5-1 mm, and the thickness is 0.2-0.5 mm.

2. The multi-energy field sintering device according to claim 1, characterized in that: The lengths of the first punch and the second punch are set so that the powder material is located at the intersection area of ​​the spherical curved surface and the cylindrical surface of the first sintering half-mold and the second sintering half-mold.

3. The multi-energy field sintering device according to claim 1, characterized in that: The inner sintering mold, the fixed mold and the insulating component are respectively provided with a first through hole, a second through hole and a third through hole.

4. The multi-energy field sintering device according to claim 1, characterized in that: Also includes vacuum system and pressure control system.

5. A method for multi-energy field sintering of high-temperature alloy micro-sintered parts, using the multi-energy field sintering device for high-temperature alloy micro-sintered parts according to any one of claims 1 to 4, characterized in that: The specific steps include: after the sintering device is installed, the powder raw material is filled into the sintering device and initially compacted using a die assembly; vacuum treatment is performed on the sintering device; Sintering includes the stage of promoting the precipitation of second phase particles, the stage of promoting the nucleation of recrystallization, the stage of uniform growth of recrystallized grains, the stage of core toughening and the stage of surface hardening of sintered parts.

6. The multi-energy field sintering method according to claim 5, characterized in that: In the second phase particle precipitation promotion stage, pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 50-60 MPa; the temperature is increased at a rate of 100-150°C / min to 850-950°C and kept at this temperature for 15-20s.

7. The multi-energy field sintering method according to claim 6, characterized in that: In the recrystallization nucleation promotion stage, after the second phase particle precipitation promotion stage is completed, vibration is started, the vibration frequency is 15~20kHz, the amplitude range is 1.5~2μm, and at the same time, the conductive voltage head assembly applies pressure to the powder raw material along the axial direction of the sintering device and maintains it at 70~80Mpa, the temperature is 880~980℃, and the temperature is kept for 10~20s.

8. The multi-energy field sintering method according to claim 7, characterized in that: In the stage of uniform growth of recrystallized grains, after the stage of promoting recrystallization nucleation, the current intensity is increased to a temperature of 1050-1100°C at a heating rate of 200-250°C / min, the vibration frequency is reduced to 10-15 kHz, and the temperature is kept at a temperature of 20-30s. At the same time, pressure is applied to the powder raw material along the axial direction of the sintering device and maintained at 60-70MPa.

9. The multi-energy field sintering method according to claim 8, characterized in that: In the core toughening stage, after the uniform growth stage of recrystallized grains is completed, the vibration source is turned off, the axial pressure is maintained at 70-80 MPa, and the current is unloaded at a rate of 10-30°C / min to cool the internal structure to 500-600°C.

10. The multi-energy field sintering method according to claim 9, characterized in that: In the sintered part surface hardening stage, after the core toughening stage is completed, the current is unloaded at a rate of 80-100°C / min to cool the sintering device to room temperature.

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