Preparation of titanium and titanium alloy powder for 3D printing based on fluidized bed jet milling technique

Abstract

A method of preparation of titanium and titanium alloy powder for 3D printing is based on a fluidized bed jet milling technique. Hydride-dehydrite titanium powder and titanium alloy powder are used as main raw material powder, jet milling and shaping are carried out in shielding atmosphere of nitrogen or argon, and finally high-performance titanium and titanium alloy powder meeting the requirements of 3D printing process is obtained. The titanium and titanium alloy powder prepared using this method has a narrow particle size distribution, approximately spherical shape, and controllable oxygen content.

Claims

1. A method of preparation of a powder for 3D printing, comprising: 1): obtain a raw material powder comprising titanium, 1,000-2,000 PPM oxygen, and a particle size of 200-800 meshes, wherein the raw material powder has an irregular morphology; 2): loading the raw material powder into a jet mill having a fluidized bed jet grinding chamber, three gas inlets each having a nozzle arranged inside the jet mill above the fluidized bed jet grinding chamber at 60-90 included angle between the nozzle and a wall surface of the grinding chamber, and a powder inlet and a powder outlet arranged at a lower end and a upper end of the fluidized bed jet grinding chamber, respectively, and a classifier wheel disposed inside the jet mill and connected to the powder outlet; 3): injecting a grinding gas into the grinding chamber through the three gas inlets, at a pressure of 0.1-10 MPa, grinding the raw material powder for 2 to 60 mins; and discharging the powder for 3D printing, wherein the classifier wheel is operated at a frequency of 0 to 60 Hz, wherein the raw material powder is a titanium alloy powder, a hydride-dehydride titanium powder, or a mixture thereof, and the grinding gas is argon or nitrogen.

2. The method according to claim 1, wherein the three nozzles of the three gas inlets form a 120 included angle with each other.

3. The method according to claim 1, wherein each gas inlet is at a negative pressure, and the powder outlet is shielded by nitrogen or argon.

4. The method according to claim 1, wherein the frequency of the classifier wheel is 60 Hz during loading of the raw material powder and is 0 Hz during discharging of the powder for 3D printing.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of jet milling;

(2) FIG. 2 is an SEM image of raw material powder;

(3) FIG. 3 is a photograph of approximately spherical titanium and titanium alloy powder prepared by the present disclosure for 3D printing.

EMBODIMENTS

(4) The schematic diagram of jet milling is shown in FIG. 1. It consists of a powder inlet, a powder outlet, three gas inlets, a stationary solid chamber wall, and a built-in moving classifier in the mill. Pressurized nitrogen is injected into the gas grinding chamber through three Laval nozzles with a diameter of 3 mm. Particles are introduced into the classifying region by the lower nozzle. As compared with fine particles, the centrifugal force is greater than the resistance for coarse powders. Thus, after colliding with the wall, coarse particles fall back to the grinding chamber to participate in further grinding. Meanwhile, the resistance becomes the dominant force in the case of fine particles, which are pulled to the central outlet to finally achieve powder classification.

Embodiment 1

(5) When the titanium powder in the present disclosure is used, the oxygen content of the hydride-dehydride titanium powder in irregular morphology is 1,200 PPM, the mass is 400 g, the particle size is 325 meshes or smaller, the included angle between the nozzles of the fluidized bed jet mill and the wall of the grinding chamber is 60, high-purity nitrogen is used as the grinding gas, the grinding gas pressure is 0.6 MPa, the frequency of the classifier wheel is 60 Hz during material feeding and 0 Hz during material discharging, and the grinding time is 6 min. The morphology of the titanium powder is irregular before the processing, as shown in FIG. 2, and is approximately spherical after the jet milling, as shown in FIG. 3, thus the sphericity is improved, the surface smoothness is higher, the fluidity is 35 s/50 g, and the oxygen content is 1,400 PPM.

(6) The entire process in the present disclosure is short in time and has lower equipment requirements; specifically, low-oxygen titanium powder in an approximately spherical shape suitable for 3D printing or injection molding can be obtained from titanium powder in irregular shapes simply by adjusting the gas flow rate and grinding gas pressure so that the particles of the powder frictionate and collide with each other. Thus, low-cost and short-process batch production can be realized.

Embodiment 2

(7) In this embodiment, the irregular hydride-dehydride titanium powder described in the embodiment 1 is used, the oxygen content is 1,200 PPM, the mass is 600 g, and the particle size is 325 meshes. The included angle between the nozzles of the fluidized bed jet mill and the wall of the grinding chamber is 60, nitrogen is used as the grinding gas, the grinding gas pressure is 0.6 MPa, the frequency of the classifier wheel is 60 Hz during material feeding and 0 Hz during material discharging, and the grinding time is 4 min. The obtained titanium powder is approximately spherical, with smooth surface, 41 s/50 g fluidity and 1,600 PPM oxygen content.

Embodiment 3

(8) In this embodiment, the hydride-dehydride titanium powder described in the embodiment 1 is used, the oxygen content is 1,200 PPM, the mass is 600 g, and the particle size is 200 meshes. The included angle between the nozzles of the fluidized bed jet mill and the wall of the grinding chamber is 60, nitrogen is used as the grinding gas, the grinding gas pressure is 0.45 MPa, the frequency of the classifier wheel is 50 Hz, and the grinding time is 6 min. The obtained titanium powder is approximately spherical, with 33 s/50 g fluidity and 1,600 PPM oxygen content.

Embodiment 4

(9) In this embodiment, the hydride-dehydride titanium powder described in the embodiment 1 is used, the oxygen content is 1,200 PPM, the mass is 400 g, and the particle size is 325 meshes. The included angle between the nozzles of the fluidized bed jet mill and the wall of the grinding chamber is 60, argon is used as the grinding gas, the grinding gas pressure is 0.45 MPa, the frequency of the classifier wheel is 60 Hz, and the grinding time is 4 min. The obtained titanium powder has 39 s/50 g fluidity and 1,700 PPM oxygen content.

Embodiment 5

(10) In this embodiment, irregular hydride-dehydride titanium powder with 1,600 PPM oxygen content is used, the mass is 600 g, the particle size of 500 meshes, the included angle between the nozzles of the fluidized bed jet mill and the wall of the grinding chamber is 90, argon is used as the grinding gas, the grinding gas pressure is 0.72 MPa, the frequency of the classifier wheel is 60 Hz, and the grinding time is 6 min. The obtained titanium powder has 35 s/50 g fluidity and 2,000 PPM oxygen content. The results obtained in the above embodiments prove that the method of preparation of titanium and titanium alloy powder for 3D printing based on a fluidized-bed jet milling technique in the present disclosure has a short process, high powder yield, high production efficiency and low cost, and can meet the requirements of 3D printing, injection molding and other processes in terms of fluidity, impurity content, particle size distribution and other properties.

(11) While the present disclosure is described above by means of embodiments exemplarily, the present disclosure is not limited to those embodiments. All other variants made to the disclosed embodiments with reference to the description of the present disclosure shall be deemed as falling in the scope defined by the claims of the present disclosure.