Method based on fluidizing for modifying and preparing low-cost titanium powders for 3D printing

Abstract

A method based on fluidizing for modifying and preparing low-cost titanium powders for 3D printing includes: using hydrogenated-dehydrogenated irregularly-shaped titanium powders as the raw material, adding the titanium powders to a fluidized bed reactor, and introducing Ar or H.sub.2 at the flow rate of 0.5-1.5 L/min, heating the reactor to 300-700° C., and fluidizing for 5-90 min to modify the titanium powders. When filled with high-purity argon gas and heated at high temperature, the sharp edges and corners of irregularly-shaped titanium powders are ground collision of the particles due to the friction among powder particles.

Claims

1. A method based on fluidizing for modifying and preparing titanium powders for 3D printing, comprising the following steps: (1) adding a raw material comprising hydrogenated-dehydrogenated irregularly-shaped titanium powders to a fluidized bed reactor, and introducing a predetermined amount of Ar or H.sub.2 gas into the fluidized bed reactor from bottom to top to remove air in the fluidized bed reactor and provide a gas protective environment for the raw material; (2) after the air in the fluidized bed reactor is removed, transferring the fluidized bed reactor to a heating system for fluidization, and during the fluidization, continuously introducing a stable flow of the Ar or H.sub.2 gas, heating the fluidized bed reactor to a constant temperature for the fluidization, and holding the fluidized bed reactor at the constant temperature for a predetermined time, wherein collision and friction occur among the hydrogenated-dehydrogenated irregularly-shaped titanium powders at the constant temperature in an Ar or H.sub.2 protective atmosphere, thereby modifying the hydrogenated-dehydrogenated irregularly-shaped titanium powders, modifying a surface morphology and a particle size distribution of the raw material; and (3) after the fluidization is completed, removing the fluidized bed reactor from the heating system, continuously introducing the stable flow of the Ar or H.sub.2 gas into the fluidized bed reactor, cooling the fluidized bed reactor in atmospheric air, and when the fluidized bed reactor is cooled, stopping introduction of the Ar or H.sub.2 gas, and collecting the titanium powders in a hopper; wherein, a flow rate of the stable flow of the Ar or H.sub.2 gas in step (2) is 0.5-1.5 L/min; wherein, the constant temperature is 300-700° C., and the predetermined time to perform the fluidization is 5-90 min; wherein, the flowability of the achieved titanium powders is better than 30 s/50 g.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of the device and the process for fluidizing titanium powders;

(2) FIG. 2 is the SEM image of the original titanium powders;

(3) FIG. 3 is the SEM image of the titanium powders after the fluidization treatment in embodiment 1; and

(4) FIG. 4 is SEM image of the titanium powders after the fluidization treatment in embodiment 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

(5) 20 g of hydrogenated-dehydrogenated irregularly-shaped titanium powders with an average particle size of 30 μm (the SEM image is shown in FIG. 2) is weighed and added into a fluidized bed reactor. Ar gas is introduced from the air inlet at the lower end of the fluidized bed reactor at the flow rate of 0.5 L/min for 30 min to remove the air in the fluidized bed reactor to prevent the oxidation of the titanium powders. The fluidized bed reactor is heated to 450° C. and the Ar gas is introduced at the flow rate of 1 L/min. After the fluidization, the fluidized bed reactor is held at 450° C. for 10 min. Subsequently, the reactor is removed and cooled for 10 min, and then the powder is removed and vacuum packaged. The morphology (see FIG. 3) of the hydrogenated-dehydrogenated titanium powders after the fluidization is observed and the flowability and oxygen content thereof are measured. The oxygen increment of the powders is the oxygen content difference between the treated powders and untreated powders. The results are shown in Table 1. The flowability is measured by using a Hall flowmeter funnel (5 mm in diameter), and the oxygen content is measured with an inert gas fusion-infrared and thermal conductivity method. After the modifying by fluidization, the oxygen increment of the titanium powders is extremely low, and the flowability meets the requirements of powder metallurgy near-net-shape forming processes such as 3D printing and injection molding.

Embodiment 2

(6) 50 g of hydrogenated-dehydrogenated irregularly shaped titanium powders with an average particle size of 80 μm is weighed and added into a fluidized bed reactor. Ar gas is introduced from the air inlet at the lower end of the fluidized bed reactor at a flow rate of 1 L/min for 10 min to remove the air in the fluidized bed reactor in order to prevent the oxidation of titanium powders. The fluidized bed reactor is heated to 500° C., and the Ar gas is introduced at the flow rate of 2 L/min. After the fluidization, the fluidized bed reactor is held at 500° C. for 20 min. Subsequently, the reactor is removed and cooled for 30 min, and then the powders are removed and vacuum packaged. The morphology of the hydrogenated-dehydrogenated titanium powders, after the fluidization is observed and the flowability and oxygen content thereof are measured. The oxygen increment of the powders is the oxygen content difference between the treated powders and untreated powders. The results are shown in Table 1. The flowability is measured by using a Hall flowmeter funnel (5 mm in diameter), and the oxygen content is measured with an inert gas fusion-infrared and thermal conductivity method. After the modifying treatment by fluidization, the oxygen increment of the titanium powders is merely 0.16 wt. %, and the flowability meets the requirements of the powder metallurgy near-net-shape forming processes such as 3D printing and injection molding.

Embodiment 3

(7) 200 g of hydrogenated-dehydrogenated irregularly shaped titanium powders with an average particle size of 40 μm is weighed and added into a fluidized bed reactor. H.sub.2 gas is introduced from the air inlet at the lower end of the fluidized bed reactor at the flow rate of 0.8 L/min for 40 min to remove the air in the fluidized bed reactor to prevent the oxidation of the titanium powders. The fluidized bed reactor is heated to 550° C. and the H.sub.2 gas is introduced at the flow rate of 5 L/min. After the fluidization, the fluidized bed reactor is held at 550° C. for 60 min. Subsequently, the reactor is removed and cooled for 25 min. Then the powder is taken out and vacuum packaged. The morphology (See FIG. 4) of the hydrogenated-dehydrogenated titanium powders, after the fluidization is observed, and the flowability and oxygen content thereof are measured. The oxygen increment of the powders is the oxygen content difference between the treated powders and untreated powders. The results are shown in Table 1. The flowability is measured by using a Hall flowmeter funnel (5 mm in diameter), and the oxygen increment is measured with an inert gas fusion-infrared and thermal conductivity method. After the modifying treatment by fluidization, the oxygen increment of the titanium powders is relatively high, but the flowability meets the requirements of powder metallurgy near-net-shape forming processes such as 3D printing and injection molding.

Embodiment 4

(8) 200 g of hydrogenated-dehydrogenated irregularly shaped titanium powders with an average particle size of 120 μm is weighed and added into a fluidized bed reactor. H.sub.2 gas is introduced from the air inlet at the lower end of the fluidized bed reactor at the flow rate of 1 L/min for 40 min to remove the air in the fluidized bed reactor to prevent the oxidation of titanium powders. The fluidized bed reactor is heated to 600° C., and the H.sub.2 gas is introduced at the flow rate of 3 L/min. After the fluidization is performed, the fluidized bed reactor is held at 600° C. for 70 min. Subsequently, the reactor is removed and cooled for 30 min, and then the powders are removed and vacuum packaged. The morphology of the hydrogenated-dehydrogenated titanium powders, after the fluidization is observed, the flowability and oxygen content thereof are measured. The oxygen increment of the powders is the oxygen content difference between the treated powders and untreated powders. The results are shown in Table 1. The flowability is measured by using a Hall flowmeter funnel (5 mm in diameter), and the oxygen increment is measured with an inert gas fusion-infrared and thermal conductivity method. After the modifying treatment by fluidization, the oxygen increment of the titanium powders is relatively high, but the flowability meets the requirements of powder metallurgy near-net-shape forming processes such as 3D printing and injection molding.