CN114570923B

CN114570923B - Superfine spherical alloy powder and preparation method thereof

Info

Publication number: CN114570923B
Application number: CN202210272855.4A
Authority: CN
Inventors: 席生岐; 谷臻
Original assignee: Shaanxi Zhiqi Kaiwu New Material Co ltd
Current assignee: Shaanxi Zhiqi Kaiwu New Material Co ltd
Priority date: 2022-03-18
Filing date: 2022-03-18
Publication date: 2023-05-30
Anticipated expiration: 2042-03-18
Also published as: CN114570923A

Abstract

The invention discloses superfine spherical alloy powder and a preparation method thereof, which belong to the technical field of metal materials and comprise the following steps: (1) Weighing metal powder, wet grinding, drying at 60 ℃ for 24 hours, dry high-energy grinding, uniformly mixing absolute ethyl alcohol and dry high-energy grinding metal powder in a grinding container, taking out, precipitating and vacuum drying to obtain mechanical alloy powder; (2) Placing the mechanically alloyed powder in a spiral powder feeding system, then under the condition of inert gas, dropping the powder in a high-temperature heating environment in a drop tube fusing device, and cooling to room temperature to obtain the superfine spherical alloy powder. The invention realizes the container-free melting, thorough alloying and droplet spheroidization of single powder particles with uniformly mixed elements to prepare spherical alloy powder, and simultaneously can flexibly design new alloy, prepare superfine spherical alloy powder, has simple and easy operation of tooling equipment, short and easy control of technological process, and can reduce the preparation cost of superfine spherical alloy powder.

Description

Superfine spherical alloy powder and preparation method thereof

Technical Field

The invention relates to the technical field of metal materials, in particular to superfine spherical alloy powder and a preparation method thereof.

Background

Whether it is a metal direct deposition or metal selective sintering metal cladding 3D process, spherical alloy powder is the basis for 3D printing. High quality spherical alloy powder is required for high quality 3D printing parts, in addition to the uniform internal components of the alloy powder, the particle size of the spherical alloy powder should be as small as possible (< 105 um) for improving the surface quality of the printing parts, and for printing fine parts such as vascular stents, the particle size of the powder should be ultrafine (< 25 um) for printing stent parts with a rod diameter of 50-100 um.

At present, two production methods of spherical alloy powder are mainly adopted, namely gas atomization powder preparation and plasma rotary electrode atomization powder preparation. The quality of spherical powder prepared by gas atomization is influenced by a plurality of process conditions, and the problems of segregation of hollow powder, satellite powder, alloy components and the like are easily generated, so that the particle size distribution is wide and the control is not easy.

The plasma rotary electrode atomization powder process (PREP) has the advantages of high sphericity and purity of powder, few no hollow powder and satellite powder, and the like, and is one of the technologies for preparing high-quality spherical metal powder. However, this process requires the preparation of consumable electrodes for different alloys, is not friendly to develop new spherical alloy materials, and does not solve the problem of composition segregation in the alloy. The method is subject to technical bottlenecks such as equipment working speed, electrode rod diameter and the like, and the particle size of metal powder produced by powder preparation of a rotary electrode is generally concentrated at 20-250 mu m. Taking titanium alloy TC4 powder as an example, the powder yield of the prior powder with the particle size smaller than 100 mu m is less than 40%, and the thicker powder particle size limits the application of the PREP technology in the field of 3D printing technology (the powder particle size is concentrated at 10-105 mu m) formed by powder melting.

Therefore, how to provide a preparation method of spherical alloy powder with fine particle size is a problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present invention provides an ultrafine spherical alloy powder and a method for preparing the same, which can solve the problems of segregation, hollowing, satellite powder, purification (inclusion) and the like of element components in the conventional spherical alloy powder prepared by melting and atomizing,

in order to achieve the above purpose, the present invention adopts the following technical scheme:

the preparation method of the superfine spherical alloy powder comprises the following steps:

(1) Weighing metal powder, wet grinding, drying at 60 ℃ for 24 hours, dry high-energy grinding, uniformly mixing absolute ethyl alcohol and the metal powder obtained by the dry high-energy grinding in a grinding container, taking out, precipitating and vacuum drying to obtain mechanical alloying prealloy powder;

(2) And placing the short-time mechanical alloying prealloy powder into a spiral powder feeding system, then under the protection of inert gas, dropping the powder in a high-temperature heating environment in a drop tube fusing device, and cooling to room temperature to obtain the superfine spherical alloy powder.

The wet grinding and the dry high-energy grinding in the invention are both carried out in a high-energy horizontal vibrating rod mill, and the structure of the high-energy horizontal vibrating rod mill is shown in figures 2-3, and specifically comprises the following steps:

a base;

an air cushion spring; the air cushion springs are fixed on the base, 4 air cushion springs are inclined inwards to form a support, and a vibration bench is arranged on the support;

a vibrating table frame; the vibration bench consists of a main shaft provided with an eccentric block and a bracket for supporting the grinding tank, and is driven by a motor to generate eccentric elliptical vibration;

a special grinding tank; the special grinding tank is of a cylinder structure, horizontally and detachably connected to the air cushion spring, and is used for placing grinding media and alloy powder to be prepared;

a motor; the motor is used for providing power for the vibration rack, and the vibration rack drives the grinding tank to realize vibration grinding;

a control system; the control system is used for controlling the rotating speed of the motor, monitoring the state of the special grinding tank in real time and transmitting the state to the mobile terminal.

The high-energy horizontal vibration grinding machine used in the invention adopts an eccentric vibration mechanism system, a motor drives a main shaft of a vibration rack to rotate, an eccentric block capable of adjusting vibration energy is arranged on the rotating main shaft, the vibration rack is supported and balanced by using an air bag soft spring, a grinding tank is arranged on the vibration rack, the rigidity coefficient of an air bag pressure adjusting system is utilized, and the stable work of the vibration system during high-energy grinding is ensured by matching with reasonable air bag pressure. The control system of the system can adjust the vibration state of the whole high-energy vibration rod mill on line, including vibration frequency, vibration amplitude and the like, by monitoring and regulating the rotation speed of the motor, the pressure of the air bag and the position of the eccentric block.

The inner wall of the milling tank is provided with a water cooling system (i.e. cooling device) so that the milling apparatus can mill continuously, typically for no more than 20 hours in one continuous milling. One end of the grinding tank is closed, and the grinding cover at the other end is provided with an air inlet and outlet pipeline, a switch ball valve and a temperature measurement thermocouple, so that high-energy grinding and temperature monitoring under vacuum and atmosphere protection can be realized; the air inlet pipeline comprises a pressure transmitter monitoring system which can detect the pressure of protective gas in the grinding tank and perform overpressure safety protection; the control system is a microprocessor, and digital production is realized.

The spiral powder feeding system integrally belongs to one link of a drop tube fusing device. Mainly comprises a small stepping motor, a spiral powder feeder, a screen, a special metal funnel, a rotary deflector rod, a rotary deflector piece and a screen. The special metal funnel is in an hourglass shape and comprises an upper funnel and a lower funnel, and two ends of the special metal funnel are provided with screens; the rotary deflector rod penetrates through the special metal funnel; one end of the rotary shifting rod extends to the outside of the special metal funnel, a small stepping motor is arranged, the other end of the rotary shifting rod is positioned in the lower funnel, a rotary shifting piece is fixedly arranged, and the rotary shifting piece is propped against the screen; the part of the rotary deflector rod positioned in the upper funnel is provided with a spiral powder feeder.

The small stepping motor can drive the spiral powder feeder to rotate; the surface of the special metal funnel is smooth, so that the powder fluidity is improved; the rotary shifting rod is connected with the rotary shifting piece, so that the powder can uniformly and dispersedly fall before finally falling into the heating element; the screen can block the powder with larger particle size, so that the falling powder has uniform size.

The beneficial effects are that: the invention combines the short-time mechanical alloying process and the powder falling tube fusing spherical process, fully plays the advantages of the short-time mechanical alloying process for conveniently and flexibly preparing the superfine prealloy powder, avoids the problems of low efficiency and medium pollution caused by the long-time conventional mechanical alloying by means of the alloying effect of the powder falling tube fusing spherical process, provides conditions and guarantees for preparing the stable superfine spherical alloy powder by the subsequent prealloy powder through the falling tube fusing spherical process, and can obtain the high-quality superfine spherical alloy powder.

The short-time mechanical alloying technology can realize uniform mixing of elements in single powder particles and moderate deformation energy storage.

In the mechanical alloying process, metal element powder is subjected to rapid lamellar formation in a short time to form fine polygonal particles, in the subsequent short grinding time, the powder size also reaches the limit granularity through repeated cold welding and fracture among components, the lamellar refinement of the components in the powder is in the range of 0.5-20 um, the mechanical mixing uniformity among the components in the powder particles is realized, the principle is shown in fig. 5, the powder is repeatedly subjected to cold welding and fracture under the collision of grinding rods to realize the component mixing, a multilayer film structure is formed (shown in fig. 6), and the internal structure of the cross section of the typical Ag-Cu mechanical alloying powder is shown in fig. 7.

The mechanical alloying powder single particles not only can realize the mechanical uniform mixing of the component ingredients, but also store higher deformation energy in the repeated high-energy grinding process, and are very beneficial to the spheroidization, particularly alloying, of the alloy powder in the subsequent fusing process. This key technology can be achieved by a special high-energy mill.

Preferably, the metal powder in step (1) includes any of Ag, fe, cu, ni, ti, cu, cr and Mo.

The beneficial effects are that: the mechanical alloying can realize solid alloying of immiscible elements which are difficult to alloy by the traditional smelting and quick cooling technology, breaks through the limitation of a balance phase diagram, and is a typical unbalanced preparation method. Mechanical alloying is mainly achieved by high-energy grinding, and common equipment is a stirring grinder, a vibration grinder, a planetary grinder and the like. In the cold welding-crushing process, the elements are in any system, and after long-time grinding, the dynamic balance of cold welding and crushing is achieved, and finally, the nano equiaxed crystal structure containing a large number of defects is formed. These ultra-fine structures and defects in the structures promote solid state diffusion and ultimately complete mechanical alloying. In addition, supersaturated solid solutions can be obtained by mechanical alloying, and these solid solutions are often formed in some alloy systems that are not miscible or have limited solid solubility (e.g., cu-Cr, cu-Mo, cu-Fe, al-Pb, etc.). The metastable alloy powder obtained by mechanical alloying and the immiscible components are mechanically ground, so that the solid alloying of the immiscible system is hopeful to be promoted, the solid solubility of insoluble elements in an immiscible matrix is further expanded, and the application of the alloy powder in the field of additive manufacturing, aerospace and aviation is further promoted.

Preferably, in the step (1), the wet grinding aid is absolute ethyl alcohol, and the adding ratio of the metal powder to the absolute ethyl alcohol is 2kg:1L; the wet grinding rate is 1440r/min and the time is 1-3h.

The beneficial effects are that: the anhydrous ethanol has good wettability to the metal powder in the invention, and can fully diffuse the metal powder in the tank, so that the metal powder can be better subjected to cold welding and crushing processes with grinding media, the alloying efficiency is improved, and the time is shortened.

Preferably, in the step (1), the dry high-energy grinding rate is 1440r/min, and the time is 3-8h; the addition ratio of the absolute ethyl alcohol to the dry high-energy grinding metal powder is 0.6g:1ml.

Preferably, the wet grinding and the dry high-energy grinding in the step (1) are carried out under inert gas conditions, wherein the temperature is not higher than 300 ℃; the inert gas is argon.

Preferably, in the step (1), the vacuum drying temperature is less than 40-60 ℃, the vacuum degree is less than 1Pa, and the vacuum drying time is 8 hours.

The beneficial effects are that: the vacuum drying temperature is too low so that the powder is not dried, too high results in a dry surface while the interior is still wet, drying is not uniform; drying time is a parameter obtained by long-term experimentation.

Preferably, the wet grinding and the dry high-energy grinding are performed under inert gas conditions, and the inert gas is argon.

The beneficial effects are that: the invention can prevent powder oxidation caused by residual air in the grinding tank when grinding under the condition of inert gas, and balance the atmospheric pressure inside and outside the grinding tank.

Preferably, the high temperature heating temperature in step (2) is 1200-1700 ℃.

The beneficial effects are that: the temperature range is larger than the melting point of common pure metal or alloy powder, so that the powder is rapidly liquefied in the pipe dropping process and can be rapidly spheroidized in the cooling process.

Preferably, in the step (2), the powder feeding speed of the spiral powder feeding system is 10g/min.

The beneficial effects are that: the special spiral powder feeding system is a double-funnel spiral matching follow-up dispersion mechanism powder feeder. The design can prevent fine powder from being embedded into the clamping machine, so that powder can be smoothly dispersed into a high-temperature area of the drop tube, powder single particles can be ensured to uniformly fall from the upper end of the drop tube, and prealloyed powder single particles can be ensured to be melted and spheroidized in the vertical tube furnace. Aiming at the characteristic of larger stacking angle of non-spherical prealloyed powder, the spiral rod with the large angle funnel is adopted to rotate and feed in the small angle funnel charging bucket, so that the phenomenon of powder blocking during rotation of the spiral rod can be structurally ensured, and the powder can be smoothly fed into the vertical tubular furnace tube in a continuous dispersing way by the spiral rod and the follow-up dispersing mechanism, so that single-particle powder melting, spheroidizing and alloying are realized.

Preferably, in the step (2), the parameter of the powder falling device is the rotation speed 1440r/min of the motor, and the powder falling speed is 10g/min.

The beneficial effects are that: the control of the parameters of the fusion process of the powder falling pipe ensures the design of adjustable temperature and length of the high temperature area of the falling pipe and the sedimentation speed of the powder. For the powder preparation by the fusion and spheroidization of a drop tube, it is important whether mechanically alloyed powder can form a uniform liquid phase in a short-time drop tube heating and melting process, and the process parameters can regulate and control the single-particle powder to undergo a high-temperature zone melting and subsequent cooling process, so that the ultra-fine spherical alloy powder with uniform components can be obtained in a subsequent solidification process.

An ultrafine spherical alloy powder prepared by the preparation method of the spherical alloy powder.

Compared with the prior art, the invention discloses the superfine spherical alloy powder and the preparation method thereof, and fully utilizes the characteristics of homogenization and densification of the components of the superfine particle powder mechanically alloyed in short time and the functions of full alloying and spheroidization during fusion of the powder particle falling pipe, so as to realize container-free melting, thorough alloying and droplet spheroidization of single particles of the powder to prepare the superfine spherical alloy powder. The invention can flexibly design new alloy, has simple and good tooling equipment and simple and easy operation, has short and easy control process flow, and can reduce the preparation cost of high-quality superfine spherical alloy powder.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of the process of the invention;

FIG. 2 is a top view of a high energy horizontal vibration rod mill used in example 1 of the present invention;

FIG. 3 is a side view of a high energy horizontal vibration rod mill used in example 1 of the present invention;

FIG. 4 is a schematic view showing the structure of a pipe dropping device used in embodiment 1 of the present invention;

FIG. 5 is a schematic diagram showing the structure of a spiral powder feeding system used in embodiment 1 of the present invention;

FIG. 6 is a drawing showing the principle of the mechanically alloyed powder preparation of the invention;

FIG. 7 is a schematic diagram showing the internal structure of a cross section of a mechanically alloyed Ag-Cu powder obtained in example 1 of the invention;

FIG. 8 is a SEM photograph showing the powder morphology before and after fusing of a CuCrMo tube obtained in example 1 of the present invention; wherein part a is the powder morphology before fusing, and part b is the powder morphology after fusing;

FIG. 9 is a SEM photograph showing the morphology of the NiTi tube obtained in example 2 of the present invention before and after fusing; wherein part a is the powder morphology before fusing, and part b is the powder morphology after fusing;

FIG. 10 is a drawing showing the morphology and size of the alloy spherical powder of comparative example 1.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

(1) Powder preparation and wet grinding: the cylindrical grinding vessel and grinding media (round thin stainless steel rods) were cleaned, then the Cu, cr and Mo metal powder mixtures were weighed on an electronic scale, then placed into the cylindrical grinding vessel, and then the cylindrical grinding vessel was filled with grinding media. Absolute alcohol (1/3 volume of the grinding tank is suitable in principle, and the adding ratio of the absolute alcohol to the metal powder is 1L:2 kg) is added, the end cover of the grinding tank is closed, then the grinding tank is arranged on a high-energy horizontal grinding machine, a cooling water circulation system is started, a switch is opened, grinding is carried out for 1-3 hours at the rotating speed of 1440r/min, the machine is stopped, the cooling water system is closed, and the grinding tank is detached. Pouring out the metal powder cleaned in the grinding tank, and drying at 60 ℃ for 24 hours to obtain the wet grinding metal mixed powder.

And then cleaning the grinding equipment, firstly cleaning the pot and the grinding medium with clear water, then repeating the steps with industrial alcohol to clean the pot, the grinding medium, the grinding pot and the end cover of the grinding pot by using a blower.

(2) And (3) charging process: the round thin stainless steel rod is put into a grinding tank, then the dried wet grinding metal mixed powder is put into the grinding tank, the end cover of the grinding tank is sealed, the sealed grinding tank is pumped by a vacuum pump, inert protective gas (high-purity argon) is filled and discharged three times, the discharge of impurity gases such as air and the like is ensured, finally argon is filled, the inert gas is filled into the grinding tank, the indication of the vacuum pump is positive pressure, and the oxidation in the high-energy rod grinding process can be effectively avoided in the process. And finally, the grinding tank filled with the powder is arranged on a vibration bench of a high-energy horizontal vibration rod mill.

(3) Dry high energy milling: firstly, checking whether a grinding tank is positive pressure, ensuring inert Ar gas in the grinding tank, checking whether a circulating cooling pump (or cooling water) leaks, and starting a cooling circulation system after the circulating cooling pump (or cooling water) is determined to be error-free; controlling the temperature of a cooling pump or the flow of cooling water to be proper (the temperature or the flow of the cooling water can be regulated according to common knowledge and actual needs by a person skilled in the art in the regulation process), then switching on a power supply of the high-energy horizontal vibrating rod mill, setting the rotating speed to 1440r/min, the grinding time to 2h, and starting up and running; in the operation process of the high-energy horizontal vibration rod mill, checking whether the instrument normally operates every half an hour, and simultaneously connecting a monitoring camera through a mobile phone, checking at any time and ensuring the safety of a laboratory.

(4) And (3) stopping and taking materials: stopping the operation of the high-energy horizontal vibration rod mill, and closing a power supply; adding a certain amount of absolute ethyl alcohol into a grinding tank through a vacuum pump, starting up again and running for 20min, washing most of powder materials cold welded on the pipe wall of the grinding tank and a grinding medium in the process, then shutting down a high-energy horizontal vibration rod mill, closing a circulating water cooling pump (or cooling water), discharging the grinding tank, pouring out the mixture of the powder materials and the alcohol, and naturally settling in a large beaker for a certain time.

(5) Protection drying and obtaining ground powder: after full natural precipitation, most of the grinding particles are precipitated at the bottom of a beaker, filtering out supernatant liquid of the middle layer, and then placing precipitated metal powder in a drying box for medium-low temperature vacuum drying, wherein the vacuum drying temperature is 40-60 ℃, the vacuum degree of the drying box is lower than 1Pa, and the vacuum drying time is 8 hours; finally, taking out the dried powder, filling the powder into a sample bag, and rapidly vacuumizing for sealing and preserving to obtain the Cu-Cr-Mo short-time mechanical alloying prealloyed powder, wherein the microstructure of the prealloyed powder is shown in a part a in fig. 8. Such a powder extraction method can avoid direct contact of the ground powder with air (mainly oxygen), thereby minimizing oxidation of the ground powder.

(6) And (2) charging: placing the short-time mechanically alloyed prealloyed powder into a powder feeder shown in fig. 4, opening a controller, simultaneously introducing shielding gas argon, and simultaneously controlling a heating element to maintain 1200-1700 ℃;

(7) Tube falling and dissolving coagulation: the motor is turned on to enable the stirrer to rotate, at the moment, powder falls into the collecting device through the vertical long tube, shielding gas argon is continuously introduced after the powder falls into the collecting device, the cooling circulation device is started, the powder is finally cooled to room temperature to be taken out and sealed, and the appearance of the powder after the powder is fused by the finally obtained superfine CuCrMo spherical alloy powder falling tube is shown as part b in fig. 8. The average size of the particles after falling into the tube is 27.3 mu m, and the particles are superfine spherical alloy powder.

Example 2

The preparation method of the ultra-fine spherical alloy powder is different from example 1 only in that:

the metal powder raw materials in the step (1) are Ni and Ti, and the grinding time is 4h.

The morphology of the powder before and after fusion of the ultrafine NiTi spherical alloy powder falling tube is shown in figure 9, and the average size of the particles after the falling tube is 22.7 mu m, so that the ultrafine NiTi spherical alloy powder is ultrafine spherical alloy powder.

Comparative example 1

A method for preparing spherical alloy powder, which differs from example 1 only in that: the TC4 powder was milled directly using SLPA-D desktop grade PREP equipment from Sichuan sialon metal materials, inc. The morphology and particle size of the final TC4 powder are shown in FIG. 10.

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the superfine spherical alloy powder is characterized by comprising the following steps of:

(1) Weighing metal powder, wet grinding, drying at 60 ℃ for 24 hours, dry high-energy grinding, uniformly mixing absolute ethyl alcohol and the metal powder obtained by the dry high-energy grinding in a grinding container, taking out, precipitating and vacuum drying to obtain short-time mechanical alloying prealloy powder; wherein the wet grinding and the dry high-energy grinding are both performed in a high-energy horizontal vibration rod mill; the metal powder comprises any of Ag, cu, ni, ti, cu, cr and Mo; the wet grinding aid is absolute ethyl alcohol, and the adding ratio of the metal powder to the absolute ethyl alcohol is 2kg:1L; the wet grinding rate is 1440r/min, and the time is 1-3h; the dry high-energy grinding rate is 1440r/min, and the time is 3-8h; the addition ratio of the absolute ethyl alcohol to the dry high-energy grinding metal powder is 1mL:0.6g;

(2) Placing the short-time mechanical alloying prealloy powder in a spiral powder feeding system, then under the condition of inert gas, falling powder in a high-temperature heating environment in a falling pipe fusing device, and cooling to room temperature to obtain the superfine spherical alloy powder, wherein the powder feeding speed of the spiral powder feeding system is 10g/min; the high-temperature heating temperature is 1200-1700 ℃.

2. The method for producing an ultrafine spherical alloy powder according to claim 1, wherein the wet grinding and the dry grinding in step (1) are carried out at a high-energy grinding temperature of not higher than 300 ℃ under inert gas conditions; the inert gas is argon.

3. The method for preparing ultrafine spherical alloy powder according to claim 2, wherein the vacuum drying temperature in step (1) is less than 40-60 ℃, the vacuum degree is less than 1Pa, and the vacuum drying time is 8 hours.

4. A spherical alloy powder produced by the production method of the ultrafine spherical alloy powder according to any one of claims 1 to 3.