CN110614376B

CN110614376B - Preparation method of tungsten-copper composite powder for 3D printing

Info

Publication number: CN110614376B
Application number: CN201910862272.5A
Authority: CN
Inventors: 宋晓艳; 毕学东; 侯超; 李昱嵘
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2019-09-12
Filing date: 2019-09-12
Publication date: 2022-05-17
Anticipated expiration: 2039-09-12
Also published as: CN110614376A

Abstract

A preparation method of tungsten-copper composite powder for 3D printing belongs to the technical field of metal powder preparation. The method comprises the steps of preparing slurry by using tungsten powder and copper powder with average particle sizes of 0.5-3 mu m as initial raw materials, and then carrying out spray drying on the slurry to obtain micron-level tungsten-copper composite powder. Controlling the morphology and particle size distribution of the granulated powder by adjusting parameters such as the frequency of the atomizer; and finally, carrying out heat treatment on the granulated composite powder, and obtaining the spherical tungsten-copper composite powder with sphericity, fluidity and oxygen content meeting the 3D printing requirements through degumming, densification and consolidation. Compared with other process methods, the method can obtain the two-phase composite spherical powder with larger difference of melting points, and the particle size of the powder is easy to control, the process flow is simple, and the cost is lower.

Description

Preparation method of tungsten-copper composite powder for 3D printing

Technical Field

The invention relates to a preparation method of spherical metal composite powder suitable for 3D printing, and belongs to the technical field of metal powder preparation.

Background

At present, the preparation process of the tungsten-copper composite material mainly comprises an infiltration method and a powder metallurgy method. However, both of these two preparation methods have certain limitations, and the infiltration method is prone to generate the problems of closed pores, copper pools, tungsten agglomeration and the like. For the powder metallurgy sintering method, the poor wettability between tungsten and copper leads to the difficulty in preparing the high-density tungsten-copper block composite material. In addition, the complex mold structures required for some parts make industrial manufacturing costly. Therefore, the limited preparation method is a key problem for restricting the wider application of the tungsten-copper composite material. Selective Laser Melting (SLM) is an additive manufacturing technique, and its working principle is to control laser beam to selectively melt powder through a preset three-dimensional model, and directly manufacture a three-dimensional part with a complex structure in a layer-by-layer overlapping manner. The forming mode can greatly reduce the production cost of complex parts and effectively shorten the production period, so that the SLM has obvious advantages and potential and becomes a new technology for preparing the tungsten-copper block composite material.

For SLM, the quality of the printing powder directly affects the printing process and print performance. For example, the powder should have high sphericity, high fluidity and narrow particle size distribution to ensure smooth powder spreading during printing. For the current research situation of the preparation of the printing powder suitable for the SLM, the powder is mainly obtained through two modes, one mode is that spherical tungsten powder and copper powder are mechanically mixed to serve as initial printing powder; the other is to lay W, Cu two kinds of powder into the laser working area as the initial powder directly in the printing process. At present, no report on a preparation method of spherical tungsten-copper composite powder exists, and the research on using the spherical tungsten-copper composite powder as 3D printing initial powder is lacked. Although there are many methods for preparing spherical metal powder, such as gas atomization method, plasma spheroidization method, etc., these methods have the common property that spheroidization is performed while the metal powder is in a molten state, and thus, these methods are not suitable for preparing composite powder of two metals having widely different melting points (e.g., W melting point 3422 ℃, Cu melting point 1084 ℃).

Disclosure of Invention

Aiming at the background of the field, the invention provides a preparation method of high-purity spherical tungsten-copper composite powder suitable for 3D printing requirements in order to solve the limitation of the prior art.

The preparation method provided by the invention comprises the following process flows and principles: tungsten powder and copper powder with average particle size of 0.5-3 mu m are used as initial raw materials to prepare slurry, and then spray drying is carried out on the slurry to obtain micron-grade tungsten-copper composite powder. Controlling the morphology and particle size distribution of the granulated powder by adjusting parameters such as the frequency of the atomizer; and finally, carrying out heat treatment on the granulated composite powder, and obtaining the spherical tungsten-copper composite powder with sphericity, fluidity and oxygen content meeting the 3D printing requirements through degumming, densification and consolidation. Compared with other process methods, the method can obtain the two-phase composite spherical powder with larger difference of melting points, and the particle size of the powder is easy to control, the process flow is simple, and the cost is lower.

The invention provides a preparation method of spherical tungsten-copper composite powder suitable for 3D printing, which comprises the following steps:

(1) proportioning tungsten powder and copper powder according to a certain chemical proportion (the mass ratio of W to Cu is 4: 1-1: 1), mixing with polyethylene glycol 20000 and deionized water to prepare slurry, and performing ball milling for 1-2h to obtain stable slurry, wherein the mass of the metal powder is 60-75% of the total mass of the slurry, and the mass of the polyethylene glycol 20000 is 3-4% of the mass of the powder;

(2) carrying out centrifugal spray drying on the slurry prepared in the step (1), wherein the air inlet temperature is 120 ℃, the frequency of an atomizer is 45-60 Hz, and the feeding speed is 15-25 r/min, so as to obtain spherical metal composite particles with the particle size of below 50 micrometers;

(3) performing two-stage heat treatment on the spherical particles obtained in the step (2) by using a vacuum sintering furnace, wherein in the first stage, the heat treatment temperature is 400 ℃ under the atmosphere of hydrogen gas, and the heat preservation time is 1 h; the second stage is carried out in argon atmosphere, the heat treatment temperature is 790-810 ℃, and the heat preservation time is 0.5-1 h. Finally, the micron-sized spherical tungsten-copper composite powder with high sphericity and fluidity is obtained, and the requirements of the powder for 3D printing can be met.

At present, although methods such as a spray drying method for preparing spherical tungsten alloy powder and a coating method for preparing spherical tungsten copper material exist, a technology for preparing spherical W-Cu composite powder by a spray granulation method does not exist. Compared with the prior method for preparing spherical metal or alloy powder, the method has the following main technical characteristics and advantages:

(1) the problem of preparing spherical composite powder from two components with large melting point difference and poor wettability is solved. Because of large difference of melting points, the spheroidization can not coexist in a molten state; meanwhile, the requirements on the spray drying and heat treatment processes are high, relevant preparation parameters and combinations thereof cannot be obtained by extension from the existing method, particularly, the determination requirements on temperature, time and the like are very strict, the Cu is ensured to be properly melted to play a role in solidifying powder, and the temperature cannot be too high to prevent the Cu from being separated from the powder, so that the Cu is separated from the W and the spherical structure is damaged.

(2) Micron-sized copper powder and tungsten powder are selected as raw materials, and compared with the nanometer powder used in other granulation processes, the production cost is greatly reduced.

(3) In the preparation process of the slurry, the polyethylene glycol is simultaneously used as an organic binder and a dispersing agent in the slurry, so that the metal powder is prevented from agglomerating and can be uniformly dispersed in the slurry.

(4) The preparation of the stable and uniform slurry plays a crucial role in the appearance of the granulated powder and the powder yield.

(5) Compared with simple mechanical mixing of spherical tungsten powder and spherical copper powder, tungsten and copper in the granulated composite powder are distributed more uniformly, and the tungsten-copper composite powder which has better sphericity and high fluidity and meets the requirements of different particle sizes and is suitable for 3D printing can be prepared by regulating and controlling the parameter combination of each process step.

(6) The heat treatment process after granulation is very important for finally obtaining the metal powder meeting the 3D printing requirements. The heat treatment temperature is obtained through a large number of tests and explorations, a two-stage heat treatment mode is adopted, the first-stage heat treatment is carried out in a micro-positive pressure hydrogen atmosphere for removing the organic binder, and the hydrogen pressure is 1015mbar to 1030 mbar; the second stage heat treatment has the effect of slightly melting copper particles in the granulated powder particles to form solid phase bonding, and simultaneously, the composite powder particles are not integrally sintered, so that the formation of satellite balls is avoided, and the powder quality is improved.

(7) The method adopts a spray drying process to prepare powder, has simple steps, has stronger controllability on the sphericity and the particle size distribution of the powder, and has lower production cost compared with the prior spherical metal powder preparation process.

Drawings

FIG. 1 is a micrograph of a spherical W-30Cu composite powder prepared according to example 1 of the present invention.

FIG. 2 is a statistical view of the particle size distribution of the spherical W-30Cu composite powder prepared in example 1 of the present invention.

FIG. 3 is a micrograph of a spherical W-40Cu composite powder prepared according to example 2 of the present invention.

FIG. 4 is a particle size distribution statistical chart of the spherical W-40Cu composite powder prepared in example 2 of the present invention.

Table 1 results of sphericity and fluidity test of tungsten-copper composite powder particles obtained in inventive example 1 and example 2.

Detailed Description

Example 1, high-purity tungsten powder and copper powder each having an average particle size of 1 μm were mixed in a mass ratio of 7: 3, and preparing suspension slurry with 3% of polyethylene glycol 20000 and deionized water, wherein the total mass of the metal powder accounts for 75% of the mass of the slurry. Mixing materials, performing ball milling for 1h to obtain uniform and stable suspension slurry, and performing agglomeration granulation by using centrifugal atomization drying equipment, wherein the air inlet temperature is 120 ℃, the frequency of an atomizer is 50Hz, and the feeding speed is 20r/min to obtain spherical composite powder; carrying out heat treatment on the powder obtained by spray drying by using a vacuum sintering furnace, wherein the heat treatment temperature in the first stage is 400 ℃, introducing hydrogen atmosphere, and keeping the temperature for 1h, wherein the hydrogen pressure is 1030 mbar; and the temperature of the second stage of heat treatment is 800 ℃, and the heat preservation is carried out for 0.5h in the argon atmosphere, so as to obtain the micron-sized spherical tungsten-copper composite powder with high sphericity and high fluidity. The micro-topography and particle size distribution statistical map of the prepared composite powder are shown in figures 1 and 2. The results of the sphericity and fluidity measurements are shown in table 1.

Example 2, high-purity tungsten powder and copper powder each having an average particle size of 1 μm were mixed in a mass ratio of 3: 2, and preparing suspension slurry with 4% of polyethylene glycol 20000 and deionized water, wherein the total mass of the metal powder accounts for 70% of the mass of the slurry. Mixing materials, performing ball milling for 1h to obtain uniform and stable suspension slurry, and performing agglomeration granulation by using centrifugal atomization drying equipment, wherein the air inlet temperature is 120 ℃, the frequency of an atomizer is 55Hz, and the feeding speed is 25r/min to obtain spherical composite powder; carrying out heat treatment on the powder obtained by spray drying by using a vacuum sintering furnace, wherein the heat treatment temperature of the first stage is 400 ℃, introducing hydrogen atmosphere, and keeping the temperature for 1h, wherein the hydrogen pressure is 1020 mbar; and the temperature of the second stage of heat treatment is 790 ℃, and the heat preservation is carried out for 1h in the argon atmosphere, so as to obtain the micron-sized spherical tungsten-copper composite powder with high sphericity and high fluidity. The micro-topography and particle size distribution statistical map of the prepared composite powder are shown in fig. 3 and 4. The results of the sphericity and fluidity measurements are shown in table 1.

TABLE 1 physical Properties of the Metal powders obtained in inventive example 1 and example 2

	Sphericity (%)	Fluidity (s/50g)	Oxygen content (%)
				Example 1	＞95	45	0.03
Example 2	＞95	48	0.04

Claims

1. A preparation method of spherical tungsten-copper composite powder suitable for 3D printing is characterized by comprising the following steps:

(1) proportioning tungsten powder and copper powder according to a certain chemical proportion, mixing the tungsten powder and the copper powder with polyethylene glycol 20000 and deionized water to prepare slurry, and performing ball milling for 1-2h to obtain stable slurry, wherein the mass of the metal powder is 60-75% of the total mass of the slurry, and the mass of the polyethylene glycol 20000 is 3-4% of the mass of the powder; the average grain diameter of the tungsten powder and the copper powder is 0.5-3 mu m;

(2) carrying out centrifugal spray drying on the slurry prepared in the step (1), wherein the air inlet temperature is 120 ℃, the frequency of an atomizer is 45-60 Hz, and the feeding speed is 15-25 r/min, so as to obtain spherical metal composite particles with the particle size of below 50 mu m and narrow particle size distribution;

(3) performing two-stage heat treatment on the spherical particles obtained in the step (2) by using a vacuum sintering furnace, wherein the first stage is performed in a micro-positive pressure hydrogen atmosphere, the hydrogen pressure is 1015 mbar-1030 mbar, the heat treatment temperature is 400 ℃, and the heat preservation time is 1 h; the second stage is carried out in an argon atmosphere, the heat treatment temperature is 790-810 ℃, and the heat preservation time is 0.5-1 h;

finally obtaining uniform micron-sized spherical tungsten-copper composite powder with high sphericity and fluidity;

step (1) W: the mass ratio of Cu is 4: 1-1: 1.

2. The method for preparing spherical tungsten-copper composite powder suitable for 3D printing according to claim 1, wherein the spherical metal composite particles of step (2) have a particle size distribution of 5 to 50 μm.