CN116179884B - Vacuum induction smelting method for preparing titanium-coated NbB2Method for reinforcing TiAl alloy by nano particles - Google Patents
Vacuum induction smelting method for preparing titanium-coated NbB2Method for reinforcing TiAl alloy by nano particles Download PDFInfo
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- 229910010038 TiAl Inorganic materials 0.000 title claims abstract description 138
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 134
- 239000000956 alloy Substances 0.000 title claims abstract description 134
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 239000010936 titanium Substances 0.000 title claims abstract description 117
- 229910052719 titanium Inorganic materials 0.000 title claims abstract description 117
- 239000002105 nanoparticle Substances 0.000 title claims abstract description 97
- 230000006698 induction Effects 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 47
- 238000003723 Smelting Methods 0.000 title claims abstract description 43
- 230000003014 reinforcing effect Effects 0.000 title 1
- 238000005266 casting Methods 0.000 claims abstract description 58
- 238000002844 melting Methods 0.000 claims abstract description 48
- 230000008018 melting Effects 0.000 claims abstract description 48
- 239000000843 powder Substances 0.000 claims abstract description 39
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000010949 copper Substances 0.000 claims abstract description 35
- 229910052802 copper Inorganic materials 0.000 claims abstract description 35
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 229910052786 argon Inorganic materials 0.000 claims abstract description 8
- 239000000155 melt Substances 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 6
- 239000002245 particle Substances 0.000 claims description 37
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 17
- 229910002804 graphite Inorganic materials 0.000 claims description 17
- 239000010439 graphite Substances 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 16
- 238000012216 screening Methods 0.000 claims description 14
- 239000011261 inert gas Substances 0.000 claims description 13
- 239000011812 mixed powder Substances 0.000 claims description 11
- 238000011049 filling Methods 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 13
- 229910052782 aluminium Inorganic materials 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- 230000003647 oxidation Effects 0.000 description 9
- 238000007254 oxidation reaction Methods 0.000 description 9
- 239000002994 raw material Substances 0.000 description 9
- 229910006281 γ-TiAl Inorganic materials 0.000 description 9
- 229910021325 alpha 2-Ti3Al Inorganic materials 0.000 description 8
- 230000000153 supplemental effect Effects 0.000 description 7
- 230000017525 heat dissipation Effects 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 229910019742 NbB2 Inorganic materials 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 4
- 238000000498 ball milling Methods 0.000 description 4
- 230000001681 protective effect Effects 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 238000012958 reprocessing Methods 0.000 description 4
- 229910019748 NbB Inorganic materials 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- UQZIWOQVLUASCR-UHFFFAOYSA-N alumane;titanium Chemical compound [AlH3].[Ti] UQZIWOQVLUASCR-UHFFFAOYSA-N 0.000 description 2
- 238000005253 cladding Methods 0.000 description 2
- 229910000943 NiAl Inorganic materials 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 229910000601 superalloy Inorganic materials 0.000 description 1
- 239000011882 ultra-fine particle Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/10—Alloys containing non-metals
- C22C1/1036—Alloys containing non-metals starting from a melt
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
- C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
- C22C32/0073—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only borides
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
Abstract
The invention discloses a method for preparing titanium-coated NbB 2 nano-particle reinforced TiAl alloy by a vacuum induction smelting method, which comprises the following steps: 1. preparing titanium coated NbB 2 nano particles; 2. placing TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, and placing titanium-coated NbB 2 nano particles into a feeding port of the vacuum induction melting furnace; 3. argon is filled into the smelting chamber, so that the pressure of the smelting chamber is kept between 40000Pa and 50000Pa; the smelting furnace starts to heat, and the heating power is gradually increased until the TiAl alloy is completely melted; 4. adding titanium coated NbB 2 nano particles in a feed port into a TiAl alloy melt in a water-cooled copper crucible; the water-cooled copper crucible forms a Lorentz force field to suspend and spontaneously stir the melt, so that the titanium-coated NbB 2 nano particles are fully dispersed in the TiAl melt, and then Al powder is added to obtain the reinforced TiAl alloy melt; 5. casting the reinforced TiAl alloy melt in a smelting chamber by using a mould; and (3) after casting and cooling, obtaining the titanium-coated NbB 2 nano-particle reinforced TiAl alloy.
Description
Technical Field
The invention belongs to the technical field of preparing high-performance particle reinforced TiAl alloy, and particularly relates to a method for preparing titanium-coated NbB 2 nano-particle reinforced TiAl alloy by a vacuum induction melting method.
Background
In recent years, the aerospace industry is greatly developed in China, and meanwhile, higher requirements are put on the adopted materials, so that high-temperature materials used for preparing the aero-engine are more important. TiAl alloy is widely paid attention to because of the advantages of light weight, high specific strength, high-temperature strength, good corrosion resistance and the like, and is expected to replace nickel-based superalloy in high-performance aeroengines as a potential novel structural material. At present, the TiAl alloy has been successfully applied to the fields of low-pressure turbine blades of aerospace engines, racing engines and the like, and has wide application prospects at 650-800 ℃. However, despite the exciting prospect of commercial application, ongoing research shows that the room temperature ductility of TiAl alloys is low, and the strength and oxidation resistance are insufficient after temperatures above 800 ℃, which will certainly limit the commercial application thereof, and therefore, we need to further improve the high temperature performance and use temperature thereof.
Disclosure of Invention
Compared with the traditional particle reinforced TiAl alloy, the titanium-coated NbB 2 nano particles are easier to disperse and have better interface combination with a TiAl matrix, and after the NbB 2 nano particles are added, the high-temperature mechanical property and the high-temperature oxidation resistance of the TiAl alloy are obviously improved.
The technical scheme provided by the invention is as follows:
a method for preparing a titanium-coated NbB2 nanoparticle reinforced TiAl alloy by a vacuum induction melting method comprises the following steps:
Preparing titanium coated NbB 2 nano particles by a high-frequency induction plasma method;
Step two, placing TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, and placing titanium coated NbB 2 nano particles into a feed port of the vacuum induction melting furnace;
Wherein the vacuum degree in the smelting chamber is kept between 5Pa and 10Pa;
Step three, filling argon into the smelting chamber to keep the pressure of the smelting chamber at 40000 Pa-50000 Pa; heating the smelting furnace, and gradually increasing the heating power until the TiAl alloy is completely melted to obtain a TiAl alloy melt;
Step four, adding the titanium coated NbB 2 nano particles in the feed port into a TiAl alloy melt in a water-cooled copper crucible; the water-cooled copper crucible forms a Lorentz force field to suspend and spontaneously stir the melt, so that the titanium-coated NbB 2 nano particles are fully dispersed in the TiAl melt to obtain an enhanced TiAl alloy melt;
wherein the adding amount of the titanium coated NbB 2 nano-particles is 0.1wt.% to 0.5wt.% of the TiAl alloy melt;
Step five, in the smelting chamber, casting reinforced TiAl alloy melt by using a mould; and after casting and cooling, obtaining the titanium-coated NbB 2 nano-particle reinforced TiAl alloy.
Preferably, in the first step, the high-frequency induction plasma method is used for preparing the titanium-coated NbB 2 nano-particles, and the method comprises the following steps:
Step 1, mixing titanium powder and NbB 2 powder, and homogenizing in a mixer to obtain mixed powder;
Wherein, the grain diameter of the titanium powder is 20-300 microns, and the grain diameter of the NbB 2 powder is 10-150 microns; the mixed powder is prepared from the following components;
Step 2, filling inert gas into the vacuum reaction chamber, and generating stable inert gas mixed thermal plasma by using a high-frequency direct-current power supply; blowing the mixed powder into the vacuum reaction chamber by using inert gas, reacting after the thermal plasma, and rapidly cooling to obtain titanium-coated NbB 2 powder;
and 3, screening out particles below 300 nanometers from the titanium-coated NbB 2 powder, namely the titanium-coated NbB 2 nanometer particles.
Preferably, in the step 2, the air pressure of the vacuum reaction chamber filled with the inert gas is 10Pa to 40Pa.
Preferably, in the step 2, the mixed powder is blown into the vacuum reaction chamber at a speed of 3 m/s to 20 m/s.
Preferably, during the preparation of the NiAl alloy melt in the third step, the heating power is raised by 4kW to 7kW each time and maintained for 4 to 8 minutes.
Preferably, in the fourth step, after the titanium-coated NbB 2 nanoparticles are fully dispersed in the TiAl melt for 30 seconds to 60 seconds, al powder is added.
Preferably, in the fourth step, the casting is performed after adding the Al powder for 1 to 2 minutes.
Preferably, in said step five, the power of the smelting equipment is gradually reduced to 0 during the casting process.
Preferably, in the fifth step, casting is performed using a graphite mold.
Preferably, in the fifth step, before casting, the mold is further placed in a vacuum melting chamber in advance and is adjacent to the cold copper crucible for preheating.
The beneficial effects of the invention are as follows:
Compared with the traditional particle reinforced TiAl alloy, the method for preparing the titanium-coated NbB2 nano particle reinforced TiAl alloy by the vacuum induction smelting method provided by the invention has the advantages that the titanium-coated NbB 2 nano particles adopted in the invention are easier to disperse and have more excellent interface combination with a TiAl matrix; after NbB 2 nano particles are added, the high-temperature mechanical property and the high-temperature oxidation resistance of the TiAl alloy are obviously improved; has important practical application value for improving the service temperature of TiAl alloy and preparing high-performance aeroengines.
Drawings
FIG. 1 is an X-ray diffraction phase analysis of comparative example 1 of the present invention.
FIG. 2 shows the microstructure morphology of comparative example 1 of the present invention.
FIG. 3 is an engineering stress strain curve at 700℃for comparative example 1 of the present invention.
FIG. 4 shows an X-ray diffraction phase analysis of example 1 of the present invention.
FIG. 5 shows the microstructure morphology of example 1 of the present invention.
FIG. 6 is an engineering stress strain curve at 700℃for example 1 of the present invention.
FIG. 7 is an X-ray diffraction phase analysis of example 2 of the present invention.
FIG. 8 is a microstructure morphology according to example 2 of the present invention.
FIG. 9 is an engineering stress strain curve at 700℃for example 2 of the present invention.
FIG. 10 is an X-ray diffraction phase analysis of example 3 of the present invention.
FIG. 11 shows the microstructure morphology of example 3 of the present invention.
FIG. 12 is an engineering stress strain curve at 700℃for example 3 of the present invention.
Detailed Description
The present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
The invention provides a method for preparing titanium-coated NbB2 nano-particle reinforced TiAl alloy by a vacuum induction melting method, which comprises the following specific preparation processes in a vacuum induction melting furnace.
(1) Preparing titanium-coated NbB 2 nano particles by a high-frequency induction plasma method:
(1a) The micron titanium powder and micron NbB 2 powder mixture are configured and uniformly mixed:
Mixing NbB 2 powder accounting for 70-90 wt% of the total mass of the mixed powder (the size is 10-150 micrometers, the purity is 99.5 wt%) and titanium powder accounting for 10-30 wt% of the total mass of the mixed powder (the size is 20-300 micrometers, the purity is 99.5 wt%) in a premixing machine for 30-90 minutes, and then putting the premixed powder into a mixing machine for mixing for 10-30 hours at the speed of 10-60 r/min; taking out the powder after ball milling for later use.
(1B) Preparing titanium coated NbB 2 nano particles from the mixture of the micron titanium powder and the micron NbB 2 powder through high-frequency induction plasma:
And filling inert protective atmosphere into the vacuum reaction chamber, wherein the air pressure is 10-40Pa, and generating stable inert mixed gas thermal plasma by using a high-frequency power supply and a direct-current power supply. When the mixture of micron titanium powder and micron NbB 2 powder is blown into a reaction chamber by inert gas, the speed is 3-20 m/s, and high-energy density thermal plasma acts on the mixed powder to generate plasma, the plasma continuously collides with inert gas atoms in the diffusion process, the cooling device is used for rapidly losing energy to cool, spontaneously nucleates and coalesces to generate ultra-fine particle clusters, after the clusters are formed, the clusters rapidly leave a supersaturation area through the gas convection effect, and finally are deposited on the wall of a particle collecting device, the nuclei are formed first for solidification due to the high melting point of NbB 2, the titanium melting point is lower, and then nuclei are formed on the surface of formed NbB 2, so that the coating of titanium on NbB 2 particles is realized.
(1C) And (3) screening and re-refining the size of the titanium-coated NbB 2 particles:
screening, namely collecting titanium-coated NbB 2 particle powder, and screening out particles below 300 nanometers to obtain a finished product;
and (3) reprocessing the larger titanium coated NbB 2 particles: taking the particles with the size larger than 300 nanometers as a raw material, and then carrying out the step (1 b) until the sizes of the collected titanium-coated NbB 2 particles are all below 300 nanometers.
(2) Adding the prepared titanium-coated NbB 2 nano particles into TiAl alloy and uniformly dispersing the nano particles:
(2a) Placing the TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, avoiding the contact of TiAl alloy raw materials with the wall of the water-cooled copper crucible (except the bottom), and ensuring that the height of the TiAl alloy is not more than 5cm; titanium-coated Nb 2 nano-particles (the content of the titanium-coated Nb 2 nano-particles accounts for 0.1-0.5 wt.% of the mass of the TiAl alloy) are placed into a feed port for subsequent addition.
(2B) In order to avoid alloy oxidation and ensure experimental safety, the melting chamber of the vacuum induction melting furnace needs to be vacuumized to 5-10Pa before melting is started, and then argon is filled, so that the pressure of the melting chamber is kept between 40000 Pa and 50000Pa.
(2C) Gradually increasing the heating power by 4-7kW each time and keeping for 4-8 minutes until the TiAl alloy is melted; the NbB 2 nano particles are coated by titanium placed in a feed port before the TiAl alloy is added after being melted and immediately, and the NbB 2 nano particles can be uniformly dispersed in the TiAl alloy melt due to the fact that the water-cooled copper crucible forms a Lorentz force field to enable the melt to suspend and spontaneously stir. Adding titanium coated NbB 2 nano particles for 30-60 seconds, adding supplemental Al to maintain the proportion of Ti and Al, adding aluminum for 1-2 minutes, and casting.
(3) Casting and forming the titanium-coated NbB 2 nano-particle reinforced TiAl alloy:
(3a) The graphite mould used for casting is placed in a smelting chamber of a vacuum induction smelting furnace before smelting, and is placed at a position which is 10cm lower than the water-cooled copper crucible and 3 cm away from the water-cooled copper crucible so as to ensure that casting can be smoothly carried out.
(3B) Due to the radiation heat dissipation of the TiAl alloy melt, the graphite mold is fully preheated before casting, so that the TiAl alloy melt and the graphite mold are prevented from having excessive temperature difference.
(3C) Casting can be performed after TiAl alloy is melted and NbB 2 nano particles are fully dispersed; gradually reducing the power to 0kW while casting in the casting process; and (5) taking out the TiAl alloy after the casting is completed and the TiAl alloy is cooled to room temperature.
Example 1
The embodiment is a vacuum induction smelting method for preparing a TiAl alloy reinforced by adding titanium coated NbB 2 nano particles accounting for 0.1wt.% of the mass of the TiAl alloy (consisting of 50at.% Ti and 50at.% Al), and the specific method is as follows:
(1) Preparing titanium-coated NbB 2 nano particles by a high-frequency induction plasma method:
(1a) The micron titanium powder and micron NbB 2 powder mixture are configured and uniformly mixed:
70wt.% (70 wt.%) of micron NbB 2 powder (10 microns in size, 99.5wt.% pure) and 30wt.% of micron titanium powder (180 microns in size, 99.5wt.% pure) are premixed in a premixer for 60 minutes and then put into a blender for mixing at a speed of 10r/min for 30 hours; taking out the powder after ball milling for later use.
(1B) Preparing titanium coated NbB 2 nano particles from the mixture of the micron titanium powder and the micron NbB 2 powder through high-frequency induction plasma:
And filling inert protective atmosphere into the vacuum reaction chamber, wherein the air pressure is 10Pa, and generating stable inert mixed gas thermal plasma by using a high-frequency power supply and a direct-current power supply. The mixture of micron titanium powder and micron NbB 2 powder was blown into the reaction chamber with inert gas at a rate of 15 m/s to produce the particle size of titanium coated NbB 2.
(1C) And (3) screening and re-refining the size of the titanium-coated NbB 2 particles:
screening: collecting titanium-coated NbB 2 particle powder, and screening out particles below 300 nanometers to obtain a finished product;
and (3) reprocessing the larger titanium coated NbB 2 particles: taking the particles with the size larger than 300 nanometers as a raw material, and then carrying out the step (1 b) until the sizes of the collected titanium-coated NbB 2 particles are all below 300 nanometers.
(2) Adding the prepared titanium-coated NbB 2 nano particles into TiAl alloy and uniformly dispersing the nano particles:
(2a) Placing the TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, avoiding the contact of TiAl alloy raw materials with the wall of the water-cooled copper crucible (except the bottom), and ensuring that the height of the TiAl alloy is not more than 5 cm; 0.1wt.% of titanium coated NbB 2 nanoparticles and supplemental Al were placed in the feed throat, respectively, in sequence for subsequent addition.
(2B) In order to avoid alloy oxidation and ensure experimental safety, the melting chamber of the vacuum induction melting furnace needs to be vacuumized to 10Pa before melting is started, and then argon is filled, so that the pressure of the melting chamber is kept at 50000Pa.
(2C) Gradually increasing the heating power by 7kW each time and keeping for 4 minutes until the TiAl alloy is melted; the NbB 2 nano particles are coated by titanium placed in a feed port before the TiAl alloy is added after being melted and immediately, and the NbB 2 nano particles can be uniformly dispersed in the TiAl alloy melt due to the fact that the water-cooled copper crucible forms a Lorentz force field to enable the melt to suspend and spontaneously stir. Adding titanium coated NbB 2 nano particles for 40 seconds, adding supplemental Al to maintain the proportion of Ti and Al, and adding aluminum for 2 minutes to perform casting.
(3) Casting and forming the titanium-coated NbB 2 nano-particle reinforced TiAl alloy:
(3a) The graphite mould used for casting is placed in a smelting chamber of a vacuum induction smelting furnace before smelting, and is placed at a position which is 10cm lower than the water-cooled copper crucible and 3 cm away from the water-cooled copper crucible so as to ensure that casting can be smoothly carried out.
(3B) Due to the radiation heat dissipation of the TiAl alloy melt, the graphite mold is fully preheated before casting, so that the TiAl alloy melt and the graphite mold are prevented from having excessive temperature difference.
(3C) Casting can be performed after TiAl alloy is melted and NbB 2 nano particles are fully dispersed; gradually reducing the power to 0kW while casting in the casting process; and (5) taking out the TiAl alloy after the casting is completed and the TiAl alloy is cooled to room temperature.
In the embodiment, the TiAl alloy reinforced by adding 0.1wt.% of titanium coated NbB 2 nano particles by the vacuum induction smelting method is composed of three phases of gamma-TiAl, alpha 2-Ti3 Al and NbB 2 (figure 4); the microstructure consisted of lamellar structures formed of gamma-TiAl and alpha 2-Ti3 Al (fig. 5), which were further refined compared to the comparative example; the yield strength, ultimate tensile strength and strain at break at 700 ℃ were 334.6MPa, 447.9MPa and 7.34%, respectively (table 1 and fig. 6), which are 19.0%, 16.4% and 9.1% increased, respectively, compared to the TiAl alloy reinforced without titanium-coated NbB 2 nanoparticles.
Example 2
The embodiment is a vacuum induction smelting method for preparing a TiAl alloy (composed of 50at.% Ti and 50at.% Al) reinforced by adding 0.3wt.% of titanium-coated NbB 2 nano particles accounting for the mass of a titanium-aluminum alloy, and the specific method is as follows:
(1) Preparing titanium-coated NbB 2 nano particles by a high-frequency induction plasma method:
(1a) The micron titanium powder and micron NbB 2 powder mixture are configured and uniformly mixed:
90wt.% of micron NbB 2 powder (size 90 microns, purity 99.5 wt.%) and 10wt.% of micron titanium powder (size 20 microns, purity 99.5 wt.%) are premixed in a premixer for 90 minutes and then put into a mixer to mix for 20 hours at a speed of 40 r/min; taking out the powder after ball milling for later use.
(1B) Preparing titanium coated NbB 2 nano particles from the mixture of the micron titanium powder and the micron NbB 2 powder through high-frequency induction plasma:
And filling inert protective atmosphere into the vacuum reaction chamber, wherein the air pressure is 30Pa, and generating stable inert mixed gas thermal plasma by using a high-frequency power supply and a direct-current power supply. The mixture of micron titanium powder and micron NbB 2 powder was blown into the reaction chamber with inert gas at a rate of 3 m/s to produce the particle size of titanium coated NbB 2.
(1C) And (3) screening and re-refining the size of the titanium-coated NbB 2 particles:
screening, namely collecting titanium-coated NbB 2 particle powder, and screening out particles below 300 nanometers to obtain a finished product;
and (3) reprocessing the larger titanium coated NbB 2 particles: taking the particles with the size larger than 300 nanometers as a raw material, and then carrying out the step (1 b) until the sizes of the collected titanium-coated NbB 2 particles are all below 300 nanometers.
(2) Adding the prepared titanium-coated NbB 2 nano particles into TiAl alloy and uniformly dispersing the nano particles:
(2a) Placing the TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, avoiding the contact of TiAl alloy raw materials with the wall of the water-cooled copper crucible (except the bottom), and ensuring that the height of the TiAl alloy is not more than 5 cm; 0.3wt.% of titanium coated NbB 2 nanoparticles and supplemental Al were placed in the feed throat, respectively, in sequence for subsequent addition.
(2B) In order to avoid alloy oxidation and ensure experimental safety, the melting chamber of the vacuum induction melting furnace needs to be vacuumized to 8Pa before melting is started, and then argon is filled, so that the pressure of the melting chamber is kept at 40000Pa.
(2C) Gradually increasing the heating power by 4kW each time and keeping for 6 minutes until the TiAl alloy is melted; the NbB 2 nano particles are coated by titanium placed in a feed port before the TiAl alloy is added after being melted and immediately, and the NbB 2 nano particles can be uniformly dispersed in the TiAl alloy melt due to the fact that the water-cooled copper crucible forms a Lorentz force field to enable the melt to suspend and spontaneously stir. Adding titanium coated NbB 2 nano particles for 30 seconds, adding supplemental Al to maintain the proportion of Ti and Al, and adding aluminum for 1.5 minutes to perform casting.
(3) Casting and forming the titanium-coated NbB 2 nano-particle reinforced TiAl alloy:
(3a) The graphite mould used for casting is placed in a smelting chamber of a vacuum induction smelting furnace before smelting, and is placed at a position which is 10cm lower than the water-cooled copper crucible and 3 cm away from the water-cooled copper crucible so as to ensure that casting can be smoothly carried out.
(3B) Due to the radiation heat dissipation of the TiAl alloy melt, the graphite mold is fully preheated before casting, so that the TiAl alloy melt and the graphite mold are prevented from having excessive temperature difference.
(3C) Casting can be performed after TiAl alloy is melted and NbB 2 nano particles are fully dispersed; gradually reducing the power to 0kW while casting in the casting process; and (5) taking out the TiAl alloy after the casting is completed and the TiAl alloy is cooled to room temperature.
In the embodiment, the TiAl alloy reinforced by adding 0.3wt.% of titanium coated NbB 2 nano particles by the vacuum induction smelting method is composed of three phases of gamma-TiAl, alpha 2-Ti3 Al and NbB 2 (figure 7); the microstructure consisted of lamellar structures formed of gamma-TiAl and alpha 2-Ti3 Al (fig. 8), which were further refined compared to the comparative example; the yield strength, ultimate tensile strength and strain at break at 700 ℃ were 353.5MPa, 482.4MPa and 9.09%, respectively (table 1 and fig. 9), which are increased by 25.8%, 25.4% and 35.1%, respectively, compared to the TiAl alloy reinforced without the titanium-coated NbB 2 nanoparticle.
Example 3
The embodiment is a vacuum induction smelting method for preparing a TiAl alloy (composed of 50at.% Ti and 50at.% Al) reinforced by adding 0.5wt.% of titanium-coated NbB 2 nano particles accounting for the mass of a titanium-aluminum alloy, and the specific method is as follows:
(1) Preparing titanium-coated NbB 2 nano particles by a high-frequency induction plasma method:
(1a) The micron titanium powder and micron NbB 2 powder mixture are configured and uniformly mixed:
80wt.% of micron NbB 2 powder (size 150 microns, purity 99.5 wt.%) and 20wt.% of micron titanium powder (size 300 microns, purity 99.5 wt.%) are premixed in a premixer for 30 minutes and then put into a blender for mixing at a speed of 60r/min for 10 hours; taking out the powder after ball milling for later use.
(1B) Preparing titanium coated NbB 2 nano particles from the mixture of the micron titanium powder and the micron NbB 2 powder through high-frequency induction plasma:
And filling inert protective atmosphere into the vacuum reaction chamber, wherein the air pressure is 40Pa, and generating stable inert mixed gas thermal plasma by using a high-frequency power supply and a direct-current power supply. The mixture of micron titanium powder and micron NbB 2 powder was blown into the reaction chamber with inert gas at a rate of 20 m/s to produce the particle size of titanium coated NbB 2.
(1C) And (3) screening and re-refining the size of the titanium-coated NbB 2 particles:
screening, namely collecting titanium-coated NbB 2 particle powder, and screening out particles below 300 nanometers to obtain a finished product;
and (3) reprocessing the larger titanium coated NbB 2 particles: taking the particles with the size larger than 300 nanometers as a raw material, and then carrying out the step (1 b) until the sizes of the collected titanium-coated NbB 2 particles are all below 300 nanometers.
(2) Adding the prepared titanium-coated NbB 2 nano particles into TiAl alloy and uniformly dispersing the nano particles:
(2a) Placing the TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, avoiding the contact of TiAl alloy raw materials with the wall of the water-cooled copper crucible (except the bottom), and ensuring that the height of the TiAl alloy is not more than 5 cm; 0.5wt.% of titanium coated NbB 2 nanoparticles and supplemental Al were placed in the feed throat, respectively, in sequence for subsequent addition.
(2B) In order to avoid alloy oxidation and ensure experimental safety, the melting chamber of the vacuum induction melting furnace needs to be vacuumized to 5Pa before melting is started, and then argon is filled, so that the pressure of the melting chamber is kept at 45000Pa.
(2C) Gradually increasing the heating power, increasing 6kW each time, and keeping for 8 minutes until the TiAl alloy is melted; the NbB 2 nano particles are coated by titanium placed in a feed port before the TiAl alloy is added after being melted and immediately, and the NbB 2 nano particles can be uniformly dispersed in the TiAl alloy melt due to the fact that the water-cooled copper crucible forms a Lorentz force field to enable the melt to suspend and spontaneously stir. Adding titanium coated NbB 2 nano particles for 60 seconds, adding supplemental Al to maintain the proportion of Ti and Al, and adding aluminum for 1 minute to perform casting.
(3) Casting and forming the titanium-coated NbB 2 nano-particle reinforced TiAl alloy:
(3a) The graphite mould used for casting is placed in a smelting chamber of a vacuum induction smelting furnace before smelting, and is placed at a position which is 10cm lower than the water-cooled copper crucible and 3 cm away from the water-cooled copper crucible so as to ensure that casting can be smoothly carried out.
(3B) Due to the radiation heat dissipation of the TiAl alloy melt, the graphite mold is fully preheated before casting, so that the TiAl alloy melt and the graphite mold are prevented from having excessive temperature difference.
(3C) Casting can be performed after TiAl alloy is melted and NbB 2 nano particles are fully dispersed; gradually reducing the power to 0kW while casting in the casting process; and (5) taking out the TiAl alloy after the casting is completed and the TiAl alloy is cooled to room temperature.
In the embodiment, the TiAl alloy reinforced by adding 0.5wt.% of titanium coated NbB 2 nano particles by the vacuum induction smelting method is composed of three phases of gamma-TiAl, alpha 2-Ti3 Al and NbB 2 (figure 10); the microstructure consisted of lamellar structure formed by gamma-TiAl and alpha 2-Ti3 Al and composition of gamma-TiAl at grain boundary (FIG. 11), but gamma-TiAl at grain boundary was significantly reduced compared to the TiAl alloy reinforced by NbB 2 nanoparticle without titanium cladding, and lamellar structure was further refined compared to comparative example; the yield strength, ultimate tensile strength and strain at break at 700 ℃ were 339.3MPa, 448.0MPa and 7.53%, respectively (table 1 and fig. 12), which are increased by 20.7%, 16.5% and 11.9%, respectively, compared to the TiAl alloy reinforced without titanium-coated NbB 2 nanoparticles.
Comparative example 1
The comparative example is a vacuum induction melting method for preparing a TiAl alloy (consisting of 50at.% Ti and 50at.% Al) reinforced by NbB 2 nano particles without titanium cladding, and the specific method is as follows:
(1) Smelting of TiAl alloy reinforced by NbB 2 nano particles without adding titanium coating:
(1a) Placing the TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, avoiding the TiAl alloy raw material from contacting with the wall of the water-cooled copper crucible (except the bottom), and ensuring that the height of the TiAl alloy is not more than 5 cm.
(1B) In order to avoid alloy oxidation and ensure experimental safety, the melting chamber of the vacuum induction melting furnace needs to be vacuumized to 10Pa before melting is started, and then argon is filled, so that the pressure of the melting chamber is kept at 45000Pa.
(1C) The heating power was gradually increased by 5kW each time and held for 5 minutes until the TiAl alloy melted.
(2) Casting of TiAl alloy reinforced by NbB 2 nano particles without adding titanium coating:
(2a) The graphite mould used for casting is placed in a smelting chamber of a vacuum induction smelting furnace before smelting, and is placed at a position which is 10 cm lower than the water-cooled copper crucible and 3 cm away from the water-cooled copper crucible so as to ensure that casting can be smoothly carried out.
(2B) Due to the radiation heat dissipation of the TiAl alloy melt, the graphite mold is fully preheated before casting, so that the TiAl alloy melt and the graphite mold are prevented from having excessive temperature difference.
(2C) Casting is carried out after the TiAl alloy is melted; gradually reducing the power to 0kW while casting in the casting process; and (5) taking out the TiAl alloy after the casting is completed and the TiAl alloy is cooled to room temperature.
In the comparative example, the TiAl alloy reinforced by NbB 2 nano particles which is not added with titanium and coated by a vacuum induction smelting method is composed of two phases of gamma-TiAl and alpha 2-Ti3 Al (figure 1); the microstructure consisted of lamellar structure formed of γ -TiAl and α 2-Ti3 Al and γ -TiAl at grain boundaries (FIG. 2); the yield strength, ultimate tensile strength and strain at break at 700℃were 281.1MPa, 384.7MPa and 6.73%, respectively (Table 1 and FIG. 3).
Table 1 tensile properties at 700 ℃ of TiAl alloys prepared in examples and comparative examples
Compared with the traditional particle reinforced TiAl alloy, the method for preparing the titanium-coated NbB2 nano particle reinforced TiAl alloy by the vacuum induction smelting method provided by the invention has the advantages that the titanium-coated NbB 2 nano particles adopted in the invention are easier to disperse and have more excellent interface combination with a TiAl matrix; after NbB 2 nano particles are added, the high-temperature mechanical property and the high-temperature oxidation resistance of the TiAl alloy are obviously improved; has important practical application value for improving the service temperature of TiAl alloy and preparing high-performance aeroengines.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (8)
1. The method for preparing the titanium-coated NbB 2 nano-particle reinforced TiAl alloy by using the vacuum induction melting method is characterized by comprising the following steps of:
Preparing titanium coated NbB 2 nano particles by a high-frequency induction plasma method;
Step two, placing TiAl alloy into a water-cooled copper crucible in a vacuum induction melting furnace, and placing titanium coated NbB 2 nano particles into a feed port of the vacuum induction melting furnace;
Wherein the vacuum degree in the smelting chamber is kept between 5Pa and 10Pa;
Step three, filling argon into the smelting chamber to keep the pressure of the smelting chamber at 40000 Pa-50000 Pa; heating the smelting furnace, and gradually increasing the heating power until the TiAl alloy is completely melted to obtain a TiAl alloy melt;
Step four, adding the titanium coated NbB 2 nano particles in the feed port into a TiAl alloy melt in a water-cooled copper crucible; the water-cooled copper crucible forms a Lorentz force field to suspend and spontaneously stir the melt, so that the titanium-coated NbB 2 nano particles are fully dispersed in the TiAl melt to obtain an enhanced TiAl alloy melt;
wherein the adding amount of the titanium coated NbB 2 nano-particles is 0.1wt.% to 0.5wt.% of the TiAl alloy melt;
step five, in the smelting chamber, casting reinforced TiAl alloy melt by using a mould; after casting and cooling, obtaining the titanium-coated NbB 2 nano-particle reinforced TiAl alloy;
In the first step, the high-frequency induction plasma method is used for preparing the titanium-coated NbB 2 nano-particles, and the method comprises the following steps:
Step 1, mixing titanium powder and NbB 2 powder, and homogenizing in a mixer to obtain mixed powder;
Wherein, the grain diameter of the titanium powder is 20-300 microns, and the grain diameter of the NbB 2 powder is 10-150 microns; the ratio of NbB 2 powder in the mixed powder is 70-90 wt.%, and the ratio of titanium powder is 10-30 wt.%;
Step 2, filling inert gas into the vacuum reaction chamber, and generating stable inert gas mixed thermal plasma by using a high-frequency direct-current power supply; blowing the mixed powder into the vacuum reaction chamber by using inert gas, reacting after the thermal plasma, and rapidly cooling to obtain titanium-coated NbB 2 powder;
Step 3, screening out particles below 300 nanometers from the titanium-coated NbB 2 powder, namely the titanium-coated NbB 2 nanometer particles;
In the fourth step, after titanium coated NbB 2 nano particles are fully dispersed in TiAl melt for 30 to 60 seconds, al powder is added.
2. The method for preparing a titanium-coated NbB 2 nanoparticle reinforced TiAl alloy by vacuum induction melting according to claim 1, wherein in step 2, the gas pressure of the vacuum reaction chamber filled with inert gas is 10Pa to 40Pa.
3. The method for preparing a titanium-coated NbB 2 nanoparticle reinforced TiAl alloy by vacuum induction melting according to claim 2, characterized in that in step 2, the mixed powder is blown into the vacuum reaction chamber at a speed of 3 m/s to 20 m/s.
4. A method for preparing a titanium-coated NbB 2 nano-particle reinforced TiAl alloy by a vacuum induction smelting process according to any one of claims 1-3, characterized in that during the preparation of the TiAl alloy melt in step three, the heating power is raised by4 kW-7 kW each time and maintained for 4-8 minutes.
5. The method for preparing a titanium-coated NbB 2 nanoparticle reinforced TiAl alloy by vacuum induction melting according to claim 4, wherein in the fourth step, casting is performed after adding Al powder for 1 to 2 minutes.
6. The method for preparing a titanium-coated NbB 2 nanoparticle reinforced TiAl alloy by vacuum induction melting according to claim 5, wherein in step five, the power of the melting equipment is gradually reduced to 0 during the casting process.
7. The method for preparing a titanium-coated NbB 2 nanoparticle reinforced TiAl alloy by vacuum induction melting according to claim 6, wherein in the fifth step, casting is performed using a graphite mold.
8. The method of claim 7, wherein in step five, prior to casting, the mold is placed in a vacuum melting chamber and preheated adjacent to the cold copper crucible.
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