Low-cost 3D printing method for titanium product
Technical Field
The invention relates to the technical field of metal powder metallurgy preparation, in particular to a low-cost method for 3D printing of a titanium product.
Background
The metal titanium has the advantages of low density, excellent corrosion resistance, high specific strength, excellent biocompatibility and the like, and is widely applied to the high-technology fields of aerospace, biomedicine, petrochemical industry, energy power and the like. Currently, the preparation of high-performance titanium products with complex shapes through a 3D printing process is a high concern at home and abroad. However, the cost of 3D printing titanium products is too high, and important problems are that the raw material of spherical titanium powder is expensive, and the energy consumption in the printing process is too high, which greatly restricts the development of 3D printing titanium industry. Therefore, there is a need in the present stage to develop a method for preparing a low-cost 3D printed titanium product, which includes reducing the cost of raw material powder and reducing the printing energy consumption.
Disclosure of Invention
The invention aims to provide a method for 3D printing of a titanium product at low cost.
The hydrogenated titanium hydride powder is irregular in shape, low in price, but extremely poor in fluidity, and cannot be directly used in a 3D printing process. According to the invention, the hydrogenated and dehydrogenated titanium powder is adopted, and after one-step fluidized bed jet milling treatment, the titanium powder is successfully applied to 3D printing, the mechanical property of a workpiece is obviously superior to that of a traditional powder pressed and sintered titanium product, and the workpiece has the same performance as a spherical titanium powder 3D printed workpiece, so that the problem of overhigh cost of the spherical titanium powder is solved, the surface activity of the prepared powder is higher, the prepared powder can be printed and formed under the condition of lower laser power density, the printing energy consumption is reduced, and the preparation and processing of the 3D printed titanium product with low cost and high performance are realized.
The method comprises the following steps:
(1) placing hydrogenated dehydrogenated titanium powder with irregular shape in a fluidized bed jet mill for modification treatment to obtain near-spherical titanium powder;
(2) and (3) directly using the subsphaeroidal titanium powder obtained in the step (1) for 3D printing and forming to obtain a pure titanium product.
Wherein, the particle diameter of the hydrogenated and dehydrogenated titanium powder with irregular morphology in the step (1) is 200-500 meshes, the powder does not have fluidity, and the oxygen content is less than 2000 ppm.
And (2) in the step (1), the protective and grinding gas used by the fluidized bed jet mill is at least one of nitrogen and argon, the grinding pressure is 0.5-1MPa, and a centrifugal cyclone separator is adopted to separate the superfine titanium powder. Wherein the granularity of the superfine titanium powder is less than 15 mu m.
The modification treatment in the step (1) comprises the following specific processes:
continuously adding a hydrogenated and dehydrogenated titanium powder raw material with irregular shape into a grinding cavity of a fluidized bed jet mill, continuously inputting at least one of nitrogen or argon into the grinding cavity through an air inlet device in the jet mill process, simultaneously separating ultrafine powder (less than 15 mu m) through a centrifugal cyclone separator, circulating the nitrogen or argon through an air compressor, and further providing necessary pressure for the grinding cavity; and after the jet mill is closed, a nearly spherical titanium powder finished product with the granularity of 15-50 mu m and good fluidity is obtained, drying and screening are not needed, the nearly spherical titanium powder finished product can be directly used for 3D printing, the spherical powder drying process in the conventional 3D printing process is simplified, the process flow is reduced, the cost is reduced, and batch production can be realized.
In the step (1), the average grain diameter of the subsphaeroidal titanium powder is 15-50 mu m, the microscopic morphology is smooth surface without obvious edges and corners, the fluidity is 25-50 g-40s/50g, the oxygen content is 1000-2000ppm, and the apparent density is 2.4-2.6g/cm3。
The laser absorptivity of the near-spherical titanium powder modified by the jet mill in the step (1) is more than 10% higher than that of the raw material titanium powder.
The pure titanium product formed by 3D printing in the step (2) has oxygen content not higher than 2200ppm, relative density not lower than 98%, tensile strength more than 700MPa and fracture elongation more than 19%.
The cost of the near-spherical titanium powder used for the 3D printing formed product obtained by the method is obviously lower than that of the spherical titanium powder for 3D printing sold in the market at present, the laser power required by printing and forming is also lower than that of the spherical titanium powder, the mechanical property of the obtained product is equivalent to that of a conventional 3D printing pure titanium product, the forming rate is high, and the method is suitable for large-scale production.
The technical scheme of the invention has the following beneficial effects:
according to the scheme, the problem that the cost of the spherical titanium powder is too high is solved, the prepared powder is high in surface activity, printing and forming can be carried out under the condition of low laser power density, the printing energy consumption is reduced, and the preparation and processing of the 3D printing titanium product with low cost and high performance are realized. The method has the following specific advantages:
(1) the obtained subsphaeroidal titanium powder is subjected to 3D printing to obtain a product with high tensile strength and good product performance;
(2) the subsphaeroidal titanium powder has few pores, and a product obtained after 3D printing and forming has higher densification degree and the relative density can reach 97-99 percent.
(3) The oxygen content of a finished piece formed by adopting the near-spherical titanium powder is lower than 3000 ppm.
(4) Compared with the existing reports, the pure titanium product prepared by the method has the strength meeting the requirements, and the comparison cost shows that the cost of the hydrogenated dehydrogenated titanium powder adopted by the method is extremely low, and is only about 20-30% of the cost of the atomized spheres in the market; moreover, the activity of the modified titanium powder is increased, the laser absorption rate in the printing process is improved, namely, the laser power and the printing energy consumption are reduced, so that the preparation cost can be obviously reduced.
Drawings
FIG. 1 is a graph showing the particle size distribution of titanium hydride dehydroxide powder before and after jet milling treatment in example 1 of the low-cost 3D titanium product printing method of the present invention; wherein, the figure (a) is a particle size distribution curve chart of the superfine hydrogenated and dehydrogenated titanium powder obtained after the treatment of the jet mill, and the figure (b) is a particle size distribution curve chart of the nearly spherical hydrogenated and dehydrogenated titanium powder obtained after the treatment;
FIG. 2 is a scanning electron microscope microscopic morphology photograph of hydrogenated titanium hydride powder after being treated by jet milling in example 2 of the present invention;
FIG. 3 is a graph showing the comparison of the laser reflectivity of the near-spherical titanium powder and the raw material powder after the treatment in example 3 of the present invention;
fig. 4 is a tensile stress-strain curve of a pure titanium product prepared by 3D printing according to example 4 of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention provides a low-cost method for 3D printing of a titanium product.
The method comprises the following steps:
(1) placing hydrogenated dehydrogenated titanium powder with irregular shape in a fluidized bed jet mill for modification treatment to obtain near-spherical titanium powder;
(2) and (3) directly using the subsphaeroidal titanium powder obtained in the step (1) for 3D printing and forming to obtain a pure titanium product.
The following description is given with reference to specific examples.
Example 1
The raw material powder is 200-mesh 325-mesh hydrogenated dehydrogenated titanium powder, and the median of the particle size is 32.2 mu m. Placing raw material titanium powder into a fluidized bed jet mill grinding cavity, wherein the mass is 700g, introducing nitrogen or argon as protective gas and grinding gas, collecting ultrafine powder when the frequency of a sorting wheel is 60Hz, and treating the residual powder for 2-10min under the pressure of 0.7MPa to obtain the near-spherical titanium powder with the particle size of 15-50 mu m and the fluidity of 30s/50 g.
Furthermore, the particle size of the superfine powder is less than 15 μm, and the superfine powder has certain fluidity;
furthermore, the obtained subsphaeroidal titanium powder with the diameter of 15-50 mu m after the treatment can be directly used for 3D printing.
Furthermore, the density of the obtained near-spherical titanium powder 3D printing part can reach 98-99%, the tensile strength can reach above 700MPa, the elongation after fracture can reach 19-20%, and the mechanical property of the near-spherical titanium powder 3D printing part is comprehensively superior to that of the traditional cast pure titanium.
The particle size distribution of the hydrogenated titanium dehydrogenated powder after the treatment of the titanium powder by the jet mill is shown in FIG. 1.
Example 2
The raw material powder is 200-mesh 325-mesh hydrogenated dehydrogenated titanium powder, and the median of the particle size is 32.2 mu m. Placing raw material titanium powder into a fluidized bed jet mill grinding cavity, wherein the mass of the raw material titanium powder is 700g, introducing nitrogen or argon as protective gas and grinding gas, collecting fine powder when the frequency of a sorting wheel is 60Hz, treating the residual powder for 2-10min under the pressure of 0.7MPa to obtain the near-spherical titanium powder with the particle size of 15-50 mu m, and the fluidity of the near-spherical titanium powder is 30s/50g, so that the near-spherical titanium powder can be directly used for 3D printing.
Furthermore, the tensile strength of the product obtained by the 3D printing can reach 738.2MPa, and the elongation after fracture can reach 19.1%;
further, the microhardness of the article obtained by the 3D printing is 223HV 1.
The scanning electron microscope microscopic morphology photograph of the hydrogenated titanium hydride powder after the gas stream milling treatment is shown in figure 2.
Example 3
The raw material powder is-325 mesh hydrogenated dehydrogenated titanium powder, and the median of the particle size is 23.6 mu m. Placing raw material titanium powder into a fluidized bed jet mill grinding cavity, wherein the mass of the raw material titanium powder is 800g, introducing nitrogen or argon as protective gas and grinding gas, collecting fine powder when the frequency of a sorting wheel is 70Hz, treating the residual powder for 2-10min under the pressure of 0.6MPa to obtain the near-spherical titanium powder with the particle size of 15-50 mu m, and the flowability of the near-spherical titanium powder is 32s/50g, so that the near-spherical titanium powder can be directly used for 3D printing.
Furthermore, the obtained near-spherical titanium powder after the treatment shows higher laser absorption rate, and compared with the raw material powder, the near-spherical titanium powder has the laser absorption rate higher than that of the raw material powder by more than 10 percent;
selective laser melting and forming: the substrate material is pure titanium, the substrate is preheated to 200 ℃, the laser power is 170W, the scanning speed is 120mm/s, and the processing layer thickness is 30 mu m. Carrying out sand blasting on the formed piece, then carrying out ultrasonic cleaning for 10min, and drying to obtain a pure titanium 3D printed piece;
the detection shows that the density of the product is 98.6%, the oxygen content is 2500ppm, the tensile strength is 730MPa, and the elongation after fracture can reach 20.3%.
The comparison of the laser reflectivity of the treated subsphaeroidal titanium powder and the raw material powder is shown in FIG. 3.
Example 4
The raw material powder is-325 mesh hydrogenated dehydrogenated titanium powder, and the median of the particle size is 30.2 mu m. Placing raw material titanium powder into a fluidized bed jet mill grinding cavity, wherein the mass of the raw material titanium powder is 400g, introducing nitrogen or argon as protective gas and grinding gas, collecting fine powder when the frequency of a sorting wheel is 60Hz, treating the residual powder for 2-10min under the pressure of 0.72MPa to obtain the near-spherical titanium powder with the particle size of 15-50 mu m, and the fluidity of the near-spherical titanium powder is 30s/50g, so that the near-spherical titanium powder can be directly used for selective laser melting and forming.
The material of the substrate which is melted and formed by selective laser is pure titanium, the substrate is preheated to 200 ℃, the laser power is 190W, the scanning speed is 120mm/s, and the thickness of the processing layer is 50 mu m. Carrying out sand blasting on the formed piece, then carrying out ultrasonic cleaning for 10min, and drying to obtain a 3D printed piece;
the detection shows that the compactness of the product is 99%, the oxygen content is 2100ppm, the tensile strength is 732.1MPa, and the elongation after fracture can reach 19.6%.
The tensile stress strain curve of the pure titanium product prepared by 3D printing is shown in FIG. 4.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.