CN113134626B - Additive manufacturing method of titanium alloy hydrogen pump impeller for ultralow temperature environment - Google Patents

Additive manufacturing method of titanium alloy hydrogen pump impeller for ultralow temperature environment Download PDF

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CN113134626B
CN113134626B CN202110369243.2A CN202110369243A CN113134626B CN 113134626 B CN113134626 B CN 113134626B CN 202110369243 A CN202110369243 A CN 202110369243A CN 113134626 B CN113134626 B CN 113134626B
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titanium alloy
pump impeller
hydrogen pump
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CN113134626A (en
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牛红志
臧勐超
张海瑞
张德良
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Northeastern University China
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/065—Spherical particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • B22F1/142—Thermal or thermo-mechanical treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B33Y40/10—Pre-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/30—Stress-relieving
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon

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Abstract

The invention relates to a material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment, which comprises the following steps: s1, manufacturing titanium alloy spherical powder; s2, screening powder; s3, constructing a digital model of the hydrogen pump impeller; s4, electron beam additive manufacturing; and S5, post-processing. The density of the titanium alloy hydrogen pump impeller for the ultralow-temperature environment manufactured by the invention is higher than 99.8%, the oxygen content is lower than 0.08 wt%, the low-cost manufacture of the titanium alloy hydrogen pump impeller with the ultrahigh purity and a complex structure is successfully realized, and the tensile strength and the plasticity at the temperature of liquid hydrogen (20K) and liquid nitrogen (77K) exceed the levels of conventional forging and hot isostatic pressing near net-shaped impellers. Therefore, the method provided by the invention is particularly suitable for low-cost and rapid manufacturing of the titanium alloy hydrogen pump impeller for the ultralow-temperature environment with extremely high requirements on metallurgical quality and mechanical property.

Description

Additive manufacturing method of titanium alloy hydrogen pump impeller for ultralow temperature environment
Technical Field
The invention relates to a material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment, and belongs to the technical field of material increase manufacturing of titanium alloys.
Background
The titanium alloy has the highest specific strength and the best corrosion resistance in metal structural materials, has low density and no magnetism, has small thermal conductivity and thermal expansion coefficient at low temperature, and is an ideal structural material for low-temperature engineering. The development of new titanium alloy and its parts for ultra-low temperature (less than or equal to 77K) environment is the key to the development of advanced aerospace craft, lunar engineering equipment, space weapon and low temperature superconducting device. In particular, the application of the ultralow temperature titanium alloy in key parts such as a storage tank, a hydrogen pump impeller, a liquid hydrogen pipeline, a high-pressure gas cylinder and the like of a hydrogen-oxygen liquid fuel rocket engine is of great strategic significance.
Currently, the main manufacturing methods of titanium alloy hydrogen pump impellers for liquid fuel rocket engines are precision casting, powder Hot Isostatic Pressing (HIP) near net shape, and forging & precision machining. The titanium alloy hydrogen pump impeller manufactured by the precision casting method has high dimensional precision, and is a low-cost near-net-shape manufacturing method; but the graphite or ceramic mold with a complex structure needs to be manufactured, the process flow is long, the cast structure is thick, the inclusion defect is easy to generate, and the oxygen content is generally higher than 0.12 wt%; in addition, the surface of the casting has an alpha brittle layer which is difficult to remove. The titanium alloy hydrogen pump impeller manufactured by the spherical powder HIP near net forming method shortens the process flow, obviously improves the material utilization rate, and reduces the production cost, but the size shrinkage and the deformation unevenness of each part of the impeller are easy to occur in the forming process, so that the size precision is difficult to control, and the metallurgical defects such as residual particle interfaces, micropores and the like are easy to generate; the spherical powder HIP near-net forming needs to manufacture a sheath with a complex structure, and the technological processes of powder vacuum drying, compaction, sheath vacuum sealing and welding and the like are also complex. And finally, the titanium alloy hydrogen pump impeller is manufactured by the HIP near net forming method, the quality requirement on the spherical powder is high, and the HIP near net forming is performed by using the titanium alloy spherical powder by the argon gas atomization method, so that an argon gas cavity in original powder particles cannot be eliminated, and finally, residual gas holes which cannot be eliminated are caused. The titanium alloy hydrogen pump impeller is manufactured by a forging and precision machining method, the microstructure of the component is fully compact, and the dimensional precision and the purity are guaranteed. However, forging and machining titanium alloy hydrogen pump impellers generally results in material utilization rates of less than 30%, which results in high component manufacturing costs.
Disclosure of Invention
Technical problem to be solved
The invention provides a material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment, which aims to solve the problems of long process flow, low material utilization rate, difficult control of dimensional precision, low density and purity, high manufacturing cost, cracking, warping, layering and the like of a sample in the manufacturing process in the existing titanium alloy hydrogen pump impeller manufacturing technology.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
a material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment comprises the following steps:
s1, manufacturing titanium alloy spherical powder;
s2, screening powder;
s3, constructing a digital model of the hydrogen pump impeller;
s4, electron beam additive manufacturing;
and S5, post-processing.
In the above-described production method, it is preferable that, in step S1, the titanium alloy spherical powder is produced by a plasma rotary electrode method or a crucible-less electrode gas atomization method.
In the manufacturing method as described above, preferably, in step S1, the material of the titanium alloy spherical powder is any one of Ti-5Al-2.5Sn, Ti-6Al-4V, Ti-Al-Mo-Zr, and ultra-low temperature titanium alloys of Ti-Al-Mo-Sn series.
In the above production method, in step S2, the particle size of the spherical powder is preferably 50 to 130 μm.
A large number of experimental researches show that the particle size range of the powder is 50-130 mu m, the oxygen content of the manufactured alloy sample is generally lower than 0.08 wt%, the density of the formed sample is highest, interlayer holes and fusion-proof defects cannot be generated, and therefore the particle size of the spherical powder screening is preferably 50-130 mu m.
In the manufacturing method described above, preferably, in step S3, the digital model of the hydrogen pump impeller is created by using computer graphics software, and then the three-dimensional digital model is subjected to slice discretization processing and exported as a digital model file directly used for additive manufacturing.
Further, preferably, the computer drawing software is Proe, UG, Solidworks or Materialise Magics and the like, a three-dimensional digital model of the titanium alloy hydrogen pump impeller with the target shape is constructed, and a support structure is reasonably designed and added. Then, discretizing the constructed three-dimensional digital model by means of slicing software (such as Cura, Magics and the like), and finally exporting the three-dimensional digital model into a three-dimensional digital model file which can be directly used for selective melting additive manufacturing of the electron beam.
In the manufacturing method described above, preferably, in step S4, the process parameters adopted by the electron beam additive manufacturing are: the melting current is 5.0-20 mA, the melting scanning speed is 5.0-20 m/s, the preheating current is 20-40 mA, the preheating scanning speed is 22-50 m/s, the layer thickness is 30-80 μm, the channel interval is 60-100 μm, the reciprocating scanning strategy is adopted, and the substrate preheating temperature is 400-800 ℃.
It should be noted that before the selective melting of the electron beam, the spherical powder is loaded into the powder bin, the forming chamber is vacuumized to less than or equal to 0.01Pa, and then the substrate is preheated to 400-800 ℃ by the electron beam. This operation can effectively remove the air and water vapor molecules adsorbed on the surface of the powder, and prevent the powder from splashing and the powder bed from collapsing during the electron beam melting process.
In the manufacturing method, the vacuum degree of the forming chamber is kept less than or equal to 0.01Pa during the melting forming process of the selected electron beam additive manufacturing area in step S4. Researches find that the oxygen increment in the titanium alloy additive manufacturing process can be effectively reduced by adopting a high vacuum condition.
In the selective melting process of the electron beams, the powder spreading thickness is equal to the slice thickness of the digital model in the step S3, and when one layer of powder is spread, the powder layer is quickly preheated by the large-current electron beams, then the outline scanning and selective melting are carried out by the small-current electron beams, and the process is circulated until the forming is finished.
In the manufacturing method as described above, it is preferable that in step S5, the post-processing is that the titanium alloy hydrogen pump impeller manufactured in step S4 is taken out from the powder bed, separated from the base plate, and subjected to conventional processing such as powder cleaning, stent cutting, surface blasting, and the like; in order to further improve the mechanical properties of the 20K and 77K ultralow temperature, an annealing heat treatment process can be added, wherein the annealing heat treatment condition is that the temperature is kept at 900-980 ℃ for 0.5-2.5 hours, and then furnace cooling or air cooling is carried out. And after the post-treatment is finished, obtaining the titanium alloy hydrogen pump impeller for the ultralow temperature environment, which is manufactured by electron beam additive manufacturing.
(III) advantageous effects
The invention has the beneficial effects that:
the additive manufacturing method of the titanium alloy hydrogen pump impeller for the ultralow-temperature environment provided by the invention is characterized in that high-energy electron beam selective melting forming is carried out under a high vacuum condition, so that the manufactured titanium alloy hydrogen pump impeller has high purity, the oxygen content is lower than 0.08 wt%, and the density is higher than 99.8%. Compared with the traditional precision casting, powder hot isostatic pressing near-net forming, forging forming and the like, the manufacturing method has the advantages that the process flow is greatly shortened, the material utilization rate is up to more than 95%, and the integral precision forming of parts with complex structures can be ensured.
The additive manufacturing method of the titanium alloy hydrogen pump impeller for the ultralow temperature environment provided by the invention adopts the high-temperature preheating of the substrate and the rapid scanning of the electron beam to preheat the powder bed, realizes the in-situ stress relief annealing and the homogenization of the forming structure, effectively avoids the cracking, warping and layering of a sample in the manufacturing process, and is particularly suitable for precisely manufacturing the titanium alloy hydrogen pump impeller with a complex geometric shape.
The method provided by the invention has outstanding mechanical property advantages at room temperature and ultralow temperature. The room temperature tensile plasticity is higher than that of titanium alloy hydrogen pump impellers formed by precision casting, powder HIP near net shape forming and conventional forging, and the tensile strength between room temperature and 20K reaches the level equivalent to that of the conventional forged titanium alloy impellers.
The method of the invention is an ideal means for manufacturing the titanium alloy hydrogen pump impeller with high performance, complex geometric shape and ultra-low temperature environment.
Drawings
FIG. 1 is a spherical powder for electron beam additive manufacturing of a titanium alloy hydrogen pump impeller;
FIG. 2 is a three-dimensional digital model of a hydrogen pump impeller constructed by UG modeling software;
FIG. 3 is a titanium alloy hydrogen pump impeller component manufactured by electron beam additive manufacturing according to the present invention;
FIG. 4 is a microstructure characteristic of a Ti-5Al-3Mo-3Zr hydrogen pump impeller observed under a scanning electron microscope;
FIG. 5 is a graph showing the low temperature tensile properties of Ti-5Al-3Mo-3Zr hydrogen pump impellers made in accordance with the present invention;
FIG. 6 is an as-annealed microstructure characteristic of a titanium alloy hydrogen pump impeller observed via an optical microscope.
Detailed Description
The additive manufacturing method provided by the invention takes the spherical alloy powder of the titanium alloy as a raw material, and adopts an electron beam selective melting technology under the conditions of high vacuum and in-situ stress relief annealing to realize the additive manufacturing of the high-quality titanium alloy hydrogen pump impeller. The titanium alloy spherical powder is directly used, and is matched with a high vacuum environment in an electron beam additive manufacturing process, so that the oxygen content can be effectively reduced, gas molecules on the surface and inside the powder are eliminated, and the titanium alloy hydrogen pump impeller with high density and high purity is manufactured. By improving the preheating temperature of the substrate and rapidly preheating the powder layer by the electron beams, the in-situ stress relief annealing effect is realized, the cracking and deformation of the hydrogen pump impeller are avoided, and the size precision of the impeller is ensured. The invention provides a material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment, which mainly comprises the following process steps: s1, manufacturing titanium alloy spherical powder; s2, screening powder; s3, constructing a digital model of the hydrogen pump impeller; s4, electron beam additive manufacturing; and S5, post-processing. The titanium alloy may be any of ultralow temperature titanium alloys such as Ti-5Al-2.5Sn, Ti-6Al-4V, Ti-Al-Mo-Zr, Ti-Al-Mo-Sn series and the like. The invention has the innovativeness that the titanium alloy hydrogen pump impeller with a complex geometric structure is manufactured by directly using the titanium alloy spherical pre-alloy powder and by means of electron beam additive manufacturing in a high vacuum atmosphere, so that the material utilization rate is obviously improved, the process flow is shortened, and the oxygen content is reduced. In addition, the electron beam additive manufacturing of the titanium alloy hydrogen pump impeller is carried out under the conditions of higher substrate preheating temperature and repeated electron beam preheating of the powder bed, so that the defects of cracking, warping and deformation are avoided, and the yield and the dimensional accuracy are improved.
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Example 1
The embodiment provides an additive manufacturing method of a Ti-Al-Mo-Zr series titanium alloy hydrogen pump impeller. The titanium alloy comprises the following chemical components in percentage by mass: ti-5Al-3Mo-3Zr, namely, the mass ratio of Al is 5%, the mass ratio of Mo is 3%, the mass ratio of Zr is 3%, and the balance is Ti.
First, step S1 is performed to produce titanium alloy spherical powder. Firstly, preparing raw materials according to the element mass ratio of the titanium alloy Ti-5Al-3Mo-3Zr, and manufacturing the standard electrode rod for powder manufacture by adopting the conventional vacuum casting, high-temperature forging and machining process flows. Then, a spherical powder was produced by using a plasma rotary electrode method (PREP). The technological parameters of the powder preparation by the PREP method are as follows: voltage 65V, current 1900A, electrode rod phi 75X 350mm, electrode rod rotation speed 20000r/min, feeding speed 1.0mm/s, argon pressure 0.080 MPa.
Then, the screening of the spherical powder is performed at process step S2. And (4) screening the spherical powder manufactured in the process step S1, and screening the spherical powder with the granularity range of 50-130 mu m for additive manufacturing of the titanium alloy hydrogen pump impeller. FIG. 1 shows the morphology of spherical titanium alloy powder with a particle size of 50-130 μm observed by a scanning electron microscope.
Next, a process step S3 is started to construct a digital model of the hydrogen pump impeller. And (3) constructing a three-dimensional digital model of the titanium alloy hydrogen pump impeller by adopting computer three-dimensional drawing software UG, and reasonably designing and adding a support structure. Fig. 2 shows a three-dimensional digital model of the hydrogen pump impeller constructed by UG software. Then, discretizing the constructed three-dimensional digital model by means of slicing software Magics to obtain a three-dimensional digital model file directly used for selective melting additive manufacturing of the electron beam.
And (4) performing electron beam selective melting additive manufacturing of the titanium alloy hydrogen pump impeller in the process step S4 by using the spherical powder screened in the step S2 and the three-dimensional digital model of the hydrogen pump impeller constructed in the step S3. Sequentially mounting Ti-6Al-4V titanium alloy substrates, filling spherical powder into a forming bin, and pumping the vacuum degree of the forming bin to 0.5 × 10-3Pa, electron beam heating basePreparing the plate to 760 ℃ and the like. Then, selective melting and forming of electron beams of the titanium alloy hydrogen pump impeller are carried out. And (3) preheating the powder layer by rapidly scanning the powder layer for 3 times by using an electron beam for each layer of powder, then carrying out contour scanning and selective melting by using a slow electron beam, and circulating the steps until the forming is finished. The adopted electron beam selective melting process parameters are as follows: 16mA of melting current, 5.5m/s of melting scanning speed, 35mA of preheating current, 15m/s of preheating scanning speed, 50 μm of layer thickness, 90 μm of pass interval and a reciprocating scanning strategy. In the selective electron beam melting and forming process, the pressure of helium flow in the forming chamber is always kept to be 0.12 Pa.
Finally, the post-processing in process step S5 is performed. And (4) taking the titanium alloy hydrogen pump impeller manufactured by the electron beam additive manufacturing in the process step S4 out of the powder bed, removing the base plate, cutting off the bracket, and performing surface sand blasting treatment. After the post-treatment operations are completed, a sample of the titanium alloy hydrogen pump impeller is obtained, and as shown in fig. 3, a digital photo of the titanium alloy hydrogen pump impeller manufactured by electron beam additive manufacturing is obtained.
The Ti-5Al-3Mo-3Zr titanium alloy hydrogen pump impeller manufactured by the embodiment has the oxygen content of only 0.075 wt% and the compactness of 99.8% through detection. FIG. 4 shows the microstructure morphology of the titanium alloy hydrogen pump impeller observed by a scanning electron microscope, wherein the average lamella thickness of the alpha phase is 0.65 μm.
A tensile sample was prepared by sampling from the hydrogen pump impeller in the vertical direction, and tensile properties at room temperature and at ultra-low temperature were measured on a tensile tester, and a graph was drawn with the temperature as the abscissa and the tensile strength and the elongation after fracture as the ordinate, as shown in fig. 5, in which the mechanical property results shown in the printed state were the samples prepared in this example. The result shows that the room-temperature tensile fracture elongation of the electron beam forming hydrogen pump impeller reaches 21.5 percent, and the room-temperature tensile strength reaches 700 MPa; the 77K tensile strength is as high as 1230MPa, and the 20K tensile strength reaches 1485 MPa.
Compared with the traditional forging method and the titanium alloy hydrogen pump impeller precisely cast, the hydrogen pump impeller manufactured by the invention ensures the same strength, and simultaneously, the fracture elongation of 77K and 20K is respectively improved by 40 percent and 50 percent.
Example 2
The embodiment provides an additive manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow-temperature environment. The difference between this example and example 1 is that the post-treatment in step S5 is a high-temperature annealing heat treatment of the titanium alloy hydrogen pump impeller, and the specific process is to keep the temperature at 950 ℃ for 1 hour, and then to cool the furnace. FIG. 6 is a graph showing the microstructure characteristics in an annealed state observed by an optical microscope. It can be seen that in the microstructure after annealing treatment, the alpha sheet layer is obviously widened and thickened, and the size is more uniform. The mechanical property test is carried out by sampling from the annealed hydrogen pump impeller, the tensile strength of 20K is up to 1460MPa, and the fracture elongation is up to 19%.
Example 3
The embodiment provides an additive manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow-temperature environment. The present embodiment is different from embodiment 1 in that: the titanium alloy is Ti-5Al-2.5Sn titanium alloy, namely 5 percent of Al, 2.5 percent of Sn and the balance of Ti in mass ratio;
in the process step S3, a digital model is constructed, a three-dimensional digital model of the hydrogen pump impeller is constructed by means of computer three-dimensional drawing software UG, and a support structure is reasonably designed and added. And then, discretizing the constructed three-dimensional digital model by means of slicing software Cura, and exporting the three-dimensional digital model to a three-dimensional digital model file which can be directly used for selective melting additive manufacturing of the electron beam.
The Ti-5Al-2.5Sn titanium alloy hydrogen pump impeller manufactured by the embodiment has the oxygen content of only 0.080 wt% and the density of 99.7% through detection. A tensile sample is horizontally sampled from a hydrogen pump impeller and prepared, and tensile properties of the sample are tested at room temperature and ultralow temperature on a tensile testing machine, wherein the tensile strength at room temperature and 20K is respectively 740MPa and 1500MPa, the elongation after fracture is respectively 20.0 percent and 16 percent, and the performance is excellent.
Example 4
The present embodiment is different from embodiment 1 in that: the titanium alloy is Ti-6Al-4V, namely 6% of Al and 4% of V in mass ratio, and the balance is Ti.
This embodiment differs from embodiment 1 in that: step S1 is to produce spherical titanium alloy powderCrucible-free electrode-induced gas atomization (EIGA) was used. The powder preparation process parameters of the EIGA method are as follows: electrode bar size
Figure BDA0003008649800000081
The melting temperature is 1850 ℃ and the argon pressure is 3.0 MPa.
The Ti-6Al-4V titanium alloy hydrogen pump impeller manufactured by the embodiment has the compactness reaching 99.8 percent and the oxygen content of only 0.080wt percent through detection. A tensile sample is horizontally sampled from a hydrogen pump impeller and prepared, and tensile properties at room temperature and ultralow temperature are tested on a tensile testing machine, wherein the tensile strength at room temperature and 20K is respectively 820MPa and 1545MPa, the elongation after fracture is respectively 18.0 percent and 15.5 percent, and the properties are obviously higher than the forging-state properties of the same alloy.
Comparative example
The traditional precision casting method for manufacturing the titanium alloy hydrogen pump impeller needs to manufacture and use ZrO2Or Y2O3Ceramic shell molds, which are prone to inclusions and oxygen contamination, and generally have grain sizes greater than 200 μm. Therefore, 20K elongation at break for precision cast titanium alloy hydrogen pump impellers is generally less than 12%. The titanium alloy hydrogen pump impeller manufactured by the traditional forging method needs to be subjected to the steps of alloy ingot casting smelting, forging cogging, polishing and cutting, high-temperature die forging, precision machining and the like, the working procedures are complicated, and the material utilization rate is lower than 25%. The titanium alloy hydrogen pump impeller manufactured by powder hot isostatic pressing near-net forming needs to go through complex processes of preparing alloy spherical powder, manufacturing a sheath and a core, vacuum drying the powder, vacuum sealing and welding the sheath, performing hot isostatic pressing densification forming, finally removing the sheath and the core and the like, although the material utilization rate is obviously improved, the technical difficulty is high, the size precision is difficult to control, and the defect of a residual particle interface is easily generated. In addition, the fracture elongation of the low-temperature titanium alloy hydrogen pump impeller manufactured by the powder hot isostatic pressing method is less than or equal to 14 percent at 20K.
Taking the example 1 as an example, compared with the traditional forged hydrogen pump impeller, the titanium alloy hydrogen pump impeller manufactured by the invention has the advantages that the post-fracture elongation of 77K and 20K is respectively improved by 40% and 45% as shown in FIG. 5, and the material utilization rate is improved by more than 60%; compared with the precision casting titanium alloy hydrogen pump impeller, the oxygen content of the titanium alloy hydrogen pump impeller manufactured by the invention is reduced by at least 0.04 wt%, and the fracture elongation of 20K is improved by 60%; compared with the titanium alloy hydrogen pump impeller formed by spherical powder hot isostatic pressing and near net forming, the density of the titanium alloy hydrogen pump impeller manufactured by the invention is higher than 99.8%, the defect of residual particle interface is avoided, and the fracture elongation of 20K is improved by more than 30%. Therefore, the titanium alloy hydrogen pump impeller for ultralow temperature manufactured by the invention has outstanding technical advantages in material utilization rate, compactness, oxygen content and ultralow temperature mechanical property indexes.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art can change or modify the technical content disclosed above into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims (5)

1. A material increase manufacturing method of a titanium alloy hydrogen pump impeller for an ultralow temperature environment is characterized by comprising the following steps:
s1, manufacturing titanium alloy spherical powder;
s2, screening powder;
s3, constructing a digital model of the hydrogen pump impeller;
s4, electron beam additive manufacturing;
s5, post-processing;
in step S3, the building of the digital model of the hydrogen pump impeller is to build a three-dimensional digital model of the hydrogen pump impeller by using computer drawing software, and then perform slice discretization on the three-dimensional digital model to derive a digital model file directly used for additive manufacturing;
in step S4, the process parameters adopted by the electron beam additive manufacturing are: the melting current is 5.0-20 mA, the melting scanning speed is 5.0-20 m/s, the preheating current is 20-40 mA, the preheating scanning speed is 22-50 m/s, the layer thickness is 30-80 μm, the pass interval is 60-100 μm, the reciprocating scanning strategy and the substrate preheating temperature is 400-800 ℃;
in the melting and forming process of the electron beam additive manufacturing selection area, the vacuum degree of a forming chamber is kept to be less than or equal to 0.01 Pa;
the ultralow temperature environment is less than or equal to 77K;
in step S5, the post-processing is that the titanium alloy hydrogen pump impeller manufactured in step S4 is taken out of the powder bed, separated from the base plate, and subjected to powder cleaning, stent cutting, surface blasting;
the post-treatment also comprises annealing heat treatment, wherein the annealing heat treatment is carried out under the condition that the temperature is maintained at 900-980 ℃ for 0.5-2.5 hours, and then furnace cooling or air cooling is carried out.
2. The additive manufacturing method according to claim 1, wherein in step S1, the manufacturing of the titanium alloy spherical powder is performed by a plasma rotating electrode method or a crucible-less electrode gas atomization method.
3. The additive manufacturing method according to claim 1, wherein a material of the titanium alloy spherical powder is any one of Ti-5Al-2.5Sn, Ti-6Al-4V, Ti-Al-Mo-Zr, and ultra-low temperature titanium alloys of Ti-Al-Mo-Sn series.
4. The additive manufacturing method according to claim 1, wherein in step S2, the particle size of the spherical powder screen is 50 to 130 μm.
5. The additive manufacturing method of claim 1, wherein the computer graphics software is pro, UG, Solidworks, or materialimegrams, and the software for slicing is Cura or Magics.
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