CN116179883B - A method for preparing nano NbB2 particle reinforced NiAl alloy - Google Patents

Abstract

The invention discloses a preparation method of nano NbB ₂ particle reinforced NiAl alloy, which comprises the following steps: 1. preparing nickel-coated NbB ₂ nano particles; 2. placing a NiAl alloy raw material into a water-cooled copper crucible in a smelting chamber of vacuum smelting equipment, and respectively placing nickel-coated NbB ₂ nano particles and Al powder into a feed port of the vacuum smelting equipment; wherein the vacuum degree in the smelting chamber is kept between 5Pa and 20Pa; 3. filling inert gas into the smelting chamber to keep the pressure of the smelting chamber at 10000 Pa-20000 Pa; heating the smelting chamber, and gradually increasing the heating power until the NiAl alloy is completely melted to obtain a NiAl alloy melt; 4. adding nickel-coated NbB ₂ nano particles at a feed port into a NiAl alloy melt in a water-cooled copper crucible; after fully dispersing NbB ₂ nano particles in the NiAl melt by electromagnetic induction stirring, adding Al powder to obtain an enhanced NiAl alloy melt; 5. casting the reinforced NiAl alloy melt with a grinder in a smelting chamber; and after casting and cooling, obtaining the nano NbB ₂ particle reinforced NiAl alloy.

Description

A method for preparing nano NbB2 particle reinforced NiAl alloy

Technical Field

The invention belongs to the technical field of nano-particle reinforced high-temperature nickel-aluminum-based alloys, and particularly relates to a method for preparing a nano- _NbB2 particle reinforced NiAl alloy.

Background technique

With the upgrading and transformation of my country's aerospace industry, the demand for advanced high-performance materials is constantly increasing, and there is an urgent need to develop high-performance high-temperature alloys and their strengthening methods. Recent studies have shown that nanoparticles, especially nanoceramics, can effectively strengthen high-temperature alloy materials. However, due to the large specific surface area, nanoparticles are very easy to adsorb on the surface and agglomerate with each other. Therefore, how to solve the agglomeration problem of nanoparticles and how to solve the dispersion problem of nanoparticles after adding them to the melt will be an important issue in strengthening high-temperature alloy materials, which has significant significance and practical application value.

Summary of the invention

The purpose of the present invention is to provide a method for preparing a nano NbB2 particle reinforced NiAl alloy, which can improve the agglomeration phenomenon of _NbB2 ceramic particles in the NiAl alloy and improve the interface bonding between the nickel-coated _NbB2 ceramic particles and the NiAl alloy.

The technical solution provided by the present invention is:

A method for preparing a nano NbB2 particle reinforced NiAl alloy comprises the following steps:

Step 1, preparing nickel-coated _NbB2 nanoparticles;

Step 2: Place the NiAl alloy raw material into a water-cooled copper crucible in the melting chamber of the vacuum melting equipment, and place the nickel-coated _NbB2 nanoparticles and Al powder into the feeding port of the melting chamber of the vacuum melting equipment respectively;

Among them, the vacuum degree in the smelting chamber is maintained at 5Pa~20Pa;

Step 3, filling the smelting chamber with inert gas to keep the pressure of the smelting chamber at 10000Pa-20000Pa; starting heating the smelting chamber and gradually increasing the heating power until the NiAl alloy is completely melted to obtain a NiAl alloy melt;

Step 4: adding the nickel-coated _NbB2 nanoparticles at the feeding port into the NiAl alloy melt in the water-cooled copper crucible; after the _NbB2 nanoparticles are fully dispersed in the NiAl melt by electromagnetic induction stirring, Al powder is added to obtain an enhanced NiAl alloy melt;

Wherein, the mass of _NbB2 nanoparticles accounts for 0.05-0.30wt.% of the total mass of the enhanced NiAl alloy melt;

Step 5: In the smelting chamber, the reinforced NiAl alloy melt is cast using a mold; after the casting is completed and cooled, the nano _NbB2 particle reinforced NiAl alloy is obtained.

Preferably, in step 1, preparing nickel-coated _NbB2 nanoparticles comprises the following steps:

Step 1, mixing nickel powder and _NbB2 powder, and putting them into a ball mill for homogenization to obtain a mixed powder;

The particle size of the nickel powder is 20 microns to 200 microns, and the particle size of the _NbB2 powder is 10 microns to 100 microns; in the mixed powder, the nickel powder accounts for 20 to 50 wt%;

Step 2, filling the vacuum reaction chamber with an inert gas, and using a high-frequency DC power supply to generate a stable inert gas mixed thermal plasma; sending the mixed powder into the vacuum reaction chamber, after the thermal plasma post-reaction, and then rapidly cooling, to obtain nickel-coated _NbB2 powder;

Step 3: Screen out particles with a size of less than 600 nanometers from the nickel-coated _NbB2 powder, namely the nickel-coated _NbB2 nanoparticles.

Preferably, in step 2, the pressure of the vacuum reaction chamber filled with inert gas is between 0.01 MPa and 0.03 MPa.

Preferably, in step 2, the mixed powder is fed 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 step 3, the heating power is increased by 3 kW to 7 kW each time and maintained for 5 to 8 minutes.

Preferably, in the step 4, Al powder is added after the _NbB2 nanoparticles are fully dispersed in the NiAl melt for 40 seconds to 80 seconds.

Preferably, in the step 4, casting is performed 3 to 7 minutes after the Al powder is added.

Preferably, in step five, the power of the smelting equipment is gradually reduced to 0 during the casting process.

Preferably, in step five, a graphite mold is used for casting.

Preferably, in the step five, before casting, the mold is placed in a vacuum melting chamber for preheating.

The beneficial effects of the present invention are:

The method for preparing a nano _NbB2 particle reinforced NiAl alloy provided by the present invention can improve the agglomeration phenomenon of _NbB2 ceramic particles in the NiAl alloy and improve the interface bonding between the nickel-coated _NbB2 ceramic particles and the NiAl alloy. The method is simple, easy to control and automated, and has important practical application value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a NiAl alloy microstructure of Comparative Example 1 of the present invention.

FIG. 2 is the microstructure of the NiAl-0.05wt.% alloy of Example 1 of the present invention.

FIG3 is an X-ray diffraction phase analysis of Example 1 of the present invention.

FIG. 4 is a microstructure morphology of nickel-coated NbB ₂ nanoparticles according to Example 1 of the present invention.

FIG. 5 is the microstructure of the NiAl-0.15wt.% alloy of Example 2 of the present invention.

FIG6 is an X-ray diffraction phase analysis of Example 2 of the present invention.

FIG. 7 is a microstructure morphology of nickel-coated NbB ₂ nanoparticles according to Example 2 of the present invention.

FIG. 8 is the microstructure of the NiAl-0.3wt.% alloy of Example 3 of the present invention.

FIG. 9 is an X-ray diffraction phase analysis of Example 3 of the present invention.

FIG. 10 is a microstructure morphology of nickel-coated NbB ₂ nanoparticles according to Example 3 of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

The invention provides a method for preparing a nano _NbB2 particle reinforced NiAl alloy. The specific preparation process is as follows. The preparation process is carried out in a high-frequency induction plasma nano powder preparation device and a vacuum melting equipment melting chamber.

(1) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma;

(1a) Preparation and uniform mixing of micron nickel powder and micron _NbB2 powder mixture:

Prepare a mixed powder, the ingredients of which are: 50wt% to 80wt% micron _NbB2 powder _, the size of which is 10 to 100 microns, and the purity of which is 99.5wt%; 20wt% to 50wt% micron nickel powder, the size of which is 20-200 microns, and the purity of which is 99.5wt%; put the prepared mixed powder into a ball mill for homogenization treatment at a speed of 10 to 60 r/min, and mix for 30 to 90 minutes; take out the ball-milled powder for standby use.

(1b) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma from a mixture of micron nickel powder and micron _NbB2 powder:

First, the pressure of the vacuum reaction chamber filled with inert gas is set at 0.01-0.03MPa, and a high-frequency power supply and a direct current power supply are used to generate a stable inert mixed gas thermal plasma. Subsequently, a mixture of micron nickel powder and micron _NbB2 powder is sent into the reaction chamber at a speed of 3-20 m/s. When the high-energy density thermal plasma acts on the mixed powder, plasma is generated. During the diffusion process, the plasma continuously collides violently with the inert gas atoms, and then is rapidly cooled by a cooling device, spontaneously nucleates and condenses to grow into ultrafine particle clusters. After the clusters are formed, they quickly leave the supersaturated zone through gas convection, and finally deposit on the wall of the particle collection device. Due to the high melting point of _NbB2 , it first nucleates and solidifies, and the nickel has a lower melting point and then nucleates on the surface of the already formed _NbB2 , so that the nickel coating of the _NbB2 particles is achieved.

(1c) Nickel-coated NbB ₂ particle size screening and further refinement processing:

Screening treatment: Collect the nickel-coated _NbB2 particle powder prepared in step (1b), and screen out particles below 600 nanometers as the finished product; use particles larger than 600 nanometers as raw materials and process them in step (1b) until the size of the collected nickel-coated _NbB2 particle powder is all below 600 nanometers.

(2) Vacuum induction melting of nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(2a) putting the prepared NiAl alloy raw material into a water-cooled copper crucible, and paying attention to avoiding contact between the NiAl alloy raw material and the water-cooled copper crucible wall except the bottom of the crucible, and then putting the nickel-coated _NbB2 nanoparticles obtained in step (1c) and the Al powder (containing 99.8%) required to balance the NiAl ratio into the feeding port to facilitate the subsequent work;

(2b) Before starting smelting, the vacuum degree in the smelting chamber is maintained at 5-20 Pa, and then inert gas is filled to maintain the pressure of the smelting chamber at 10000-20000 Pa;

(2c) The heating power is continuously increased by 3 to 7 kW each time and maintained for 5 to 8 minutes until the NiAl alloy is melted; when the NiAl alloy is completely melted, the nickel-coated _NbB2 nanoparticles at the feeding port are added into the NiAl alloy melt in the water-cooled copper crucible; the _NbB2 nanoparticles are continuously stirred by electromagnetic induction to fully disperse them in the NiAl melt, and then Al powder is added after 40 to 80 seconds, and casting is performed after 3 to 7 minutes.

(3) Cast nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(3a) A graphite mold is used for casting. During smelting, the mold is placed in a vacuum melting chamber in advance, about 5 cm away from a water-cooled copper crucible. During the smelting process, the graphite mold is fully preheated to reduce the temperature difference between the mold and the cast NiAl alloy.

(3b) When the nickel-coated _NbB2 nanoparticles are evenly dispersed and Al is supplemented, casting begins. During casting, the power of the smelting furnace is gradually reduced to 0; finally, the NiAl alloy is cooled and can be used.

The mass of the _NbB2 nanoparticles accounts for 0.05-0.30 wt.% of the total mass of the enhanced NiAl alloy melt (the mass of the enhanced NiAl alloy finally prepared).

Example 1

This embodiment is a NiAl alloy reinforced with _NbB2 nanoparticles (composed of 50at.% Ni and 50at.% Al) prepared by vacuum induction melting, the mass of _NbB2 nanoparticles accounts for 0.05wt.% of the total mass of the prepared reinforced NiAl alloy, and the specific method is as follows:

(1) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma;

(1a) Preparation and uniform mixing of micron nickel powder and micron _NbB2 powder mixture:

Prepare a mixed powder, the ingredients of which are: 50wt% micron _NbB2 powder, the _NbB2 powder size is 20 microns, and the purity is 99.5wt%; 50wt% micron nickel powder, the nickel powder size is 180 microns, and the purity is 99.5wt%; put the prepared mixed powder into a ball mill for homogenization at a speed of 60r/min, and mix for 60 minutes; take out the ball-milled powder for standby use.

(1b) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma from a mixture of micron nickel powder and micron _NbB2 powder:

First, the pressure of the vacuum reaction chamber filled with inert gas is set at 0.01MPa, and a high-frequency power supply and a direct current power supply are used to generate a stable inert mixed gas thermal plasma. Subsequently, a mixture of micron nickel powder and micron _NbB2 powder is sent into the reaction chamber at a speed of 20 m/s. When the high-energy density thermal plasma acts on the mixed powder, a plasma is generated. During the diffusion process, the plasma continuously collides violently with the inert gas atoms, and then is rapidly cooled by a cooling device, spontaneously nucleates and condenses to grow into ultrafine particle clusters. After the clusters are formed, they quickly leave the supersaturated zone through gas convection, and finally deposit on the wall of the particle collection device. Due to the high melting point of _NbB2 , it first nucleates and solidifies, and the nickel has a lower melting point and then nucleates on the surface of the already formed _NbB2 , thereby achieving nickel coating of the _NbB2 particles.

(1c) Nickel-coated NbB ₂ particle size screening and further refinement processing:

Screening treatment: Collect the nickel-coated _NbB2 particle powder prepared in step (1b), and screen out particles below 600 nanometers as the finished product; use particles larger than 600 nanometers as raw materials and process them in step (1b) until the size of the collected nickel-coated _NbB2 particle powder is all below 600 nanometers.

(2) Vacuum induction melting of nickel-coated _NbB2 nanoparticles to reinforce NiAl alloy: (2a) Place the prepared NiAl alloy raw material into a water-cooled copper crucible. Note that except for the bottom of the crucible, the NiAl alloy raw material should avoid contact with the wall of the water-cooled copper crucible. Then, place the nickel-coated _NbB2 nanoparticles obtained in step (1c) and the Al powder (containing 99.8%) required to balance the NiAl ratio into the feeding port to facilitate subsequent work.

(2b) Before starting smelting, the vacuum degree in the smelting chamber is maintained at 5 Pa, and then inert gas is filled to keep the pressure in the smelting chamber at 15000 Pa.

(2c) The heating power is continuously increased by 3 kW each time and maintained for 6 minutes until the NiAl alloy is melted; when the NiAl alloy is completely melted, the nickel-coated _NbB2 nanoparticles at the feeding port are added into the NiAl alloy melt in the water-cooled copper crucible; the _NbB2 nanoparticles are continuously stirred by electromagnetic induction to fully disperse them in the NiAl melt, and then Al powder is added after 40 seconds, and casting is carried out after 3 minutes.

(3) Cast nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(3a) Casting is performed using a graphite mold, which is placed in a vacuum melting chamber in advance at a distance of about 5 cm from a water-cooled copper crucible during smelting. During the smelting process, the graphite mold is fully preheated to reduce the temperature difference between the graphite mold and the cast NiAl alloy;

(3b) When the nickel-coated _NbB2 nanoparticles are evenly dispersed and Al is supplemented, casting begins. During casting, the power of the smelting furnace is gradually reduced to 0; finally, the NiAl alloy is cooled and can be used.

In this embodiment, the microstructure of NiAl-0.05wt.% _NbB2 is shown in Figure 2, and it can be seen that the dispersion of _NbB2 ceramic particles in the nickel-aluminum matrix is good, there is no agglomeration of nanoparticles, and the interface of _NbB2 ceramic particles and the nickel-aluminum matrix is well bonded, without defects such as cavities. The phase composition of nickel-coated _NbB2 nanoparticles is shown in Figure 3; the organization diagram of nickel-coated _NbB2 nanoparticles is shown in Figure 4. When the strain rate is 1.0× ^10-4 s, the yield strength, ultimate compressive strength and fracture strain at 600°C are 346.7MPa, 438.2MPa, and 8.23% (Table 1), respectively, which are 8.2%, 9.4%, and 10.3% higher than the NiAl alloy reinforced by the nickel-coated _NbB2 nanoparticles. Obviously, the nanoparticles do not agglomerate, have good dispersion and good interface bonding, which is conducive to the strengthening of the mechanical properties of the nickel-aluminum alloy by nanoparticles.

Example 2

This embodiment is a NiAl alloy reinforced with _NbB2 nanoparticles (composed of 50at.% Ni and 50at.% Al) prepared by vacuum induction melting, the mass of _NbB2 nanoparticles accounts for 0.15wt.% of the total mass of the prepared reinforced NiAl alloy, and the specific method is as follows:

(1) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma;

(1a) Preparation and uniform mixing of micron nickel powder and micron _NbB2 powder mixture:

Prepare a mixed powder, the ingredients of which are: 80wt% micron _NbB2 powder, the _NbB2 powder size is 100 microns, and the purity is 99.5wt%; 20wt% micron nickel powder, the nickel powder size is 200 microns, and the purity is 99.5wt%; put the prepared mixed powder into a ball mill for homogenization at a speed of 60r/min, and mix for 90 minutes; take out the ball-milled powder for standby use.

(1b) A mixture of micron nickel powder and micron _NbB2 powder is subjected to high-frequency induction plasma to prepare nickel-coated _NbB2 nanoparticles:

First, the pressure of the vacuum reaction chamber filled with inert gas is set at 0.02MPa, and a high-frequency power supply and a direct current power supply are used to generate a stable inert mixed gas thermal plasma. Then, a mixture of micron nickel powder and micron _NbB2 powder is sent into the reaction chamber at a speed of 15 m/s. When the high-energy density thermal plasma acts on the mixed powder, a plasma is generated. During the diffusion process, the plasma continuously collides violently with the inert gas atoms, and then is rapidly cooled by a cooling device, spontaneously nucleates and condenses to grow into ultrafine particle clusters. After the clusters are formed, they quickly leave the supersaturated zone through gas convection, and finally deposit on the wall of the particle collection device. Due to the high melting point of _NbB2 , it first nucleates and solidifies, and the nickel has a lower melting point and then nucleates on the surface of the already formed _NbB2 , thereby achieving nickel coating of the _NbB2 particles.

(1c) Nickel-coated NbB ₂ particle size screening and further refinement processing:

Screening treatment: Collect the nickel-coated _NbB2 particle powder prepared in step (1b), screen out particles below 600 nanometers as the finished product; use particles larger than 600 nanometers as raw materials, and then process them in step (1b) until the size of the collected nickel-coated _NbB2 particle powder is all below 600 nanometers.

(2) Vacuum induction melting of nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(2a) putting the prepared NiAl alloy raw material into a water-cooled copper crucible, and paying attention to avoiding contact between the NiAl alloy raw material and the water-cooled copper crucible wall except the bottom of the crucible, and then putting the nickel-coated _NbB2 nanoparticles obtained in step (1c) and the Al powder (containing 99.8%) required to balance the NiAl ratio into the feeding port to facilitate the subsequent work;

(2b) Before starting smelting, the vacuum degree in the smelting chamber is maintained at 20 Pa, and then inert gas is filled to keep the pressure in the smelting chamber at 20000 Pa.

(2c) The heating power is continuously increased by 7 kW each time and maintained for 8 minutes until the NiAl alloy is melted; when the NiAl alloy is completely melted, the nickel-coated _NbB2 nanoparticles at the feeding port are added into the NiAl alloy melt in the water-cooled copper crucible; the _NbB2 nanoparticles are continuously stirred by electromagnetic induction to fully disperse them in the NiAl melt, and then Al powder is added after 80 seconds, and casting is carried out after 7 minutes.

(3) Cast nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(3a) Casting is performed using a graphite mold, which is placed in a vacuum melting chamber in advance at a distance of about 5 cm from a water-cooled copper crucible during smelting. During the smelting process, the graphite mold is fully preheated to reduce the temperature difference between the graphite mold and the cast NiAl alloy;

(3b) When the nickel-coated _NbB2 nanoparticles are evenly dispersed and Al is supplemented, casting begins. During casting, the power of the smelting furnace is gradually reduced to 0; finally, the NiAl alloy is cooled and can be used.

In this embodiment, the microstructure of NiAl-0.15wt.% NbB ₂ is shown in FIG5 , and it can be seen that the dispersion of NbB ₂ ceramic particles in the nickel-aluminum matrix is good, and there is no agglomeration of nanoparticles, and the NbB ₂ ceramic particles are well bonded to the interface of the nickel-aluminum matrix, and there are no defects such as voids. The phase composition of 0.15wt.% nickel-coated NbB ₂ nanoparticles is shown in FIG6 ; the organization diagram of nickel-coated NbB ₂ nanoparticles is shown in FIG7 . When the strain rate is 1.0×10 ^-4 s, the yield strength, ultimate compressive strength and fracture strain at 600°C are 352.4MPa, 446.5MPa, and 8.97% (Table 1), respectively, which are 10.0%, 11.5%, and 20.2% higher than the NiAl alloy reinforced by the nickel-coated NbB ₂ nanoparticles without addition. Obviously, the nanoparticles do not agglomerate, and the good dispersion and good interface bonding are conducive to the strengthening of the mechanical properties of the nickel-aluminum alloy by the nanoparticles.

Example 3

This embodiment is a NiAl alloy reinforced with _NbB2 nanoparticles (composed of 50at.% Ni and 50at.% Al) prepared by vacuum induction melting, the mass of _NbB2 nanoparticles accounts for 0.30wt.% of the total mass of the prepared reinforced NiAl alloy, and the specific method is as follows:

(1) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma;

(1a) Preparation and uniform mixing of micron nickel powder and micron _NbB2 powder mixture:

Prepare a mixed powder, the ingredients of which are: 70wt% micron _NbB2 powder, the _NbB2 powder size is 10 microns, and the purity is 99.5wt%; 30wt% micron nickel powder, the nickel powder size is 20 microns, and the purity is 99.5wt%; put the prepared mixed powder into a ball mill for homogenization at a speed of 30r/min, and mix for 50 minutes; take out the ball-milled powder for standby use.

(1b) Preparation of nickel-coated _NbB2 nanoparticles by high-frequency induction plasma from a mixture of micron nickel powder and micron _NbB2 powder:

First, the pressure of the vacuum reaction chamber filled with inert gas is set at 0.03MPa, and a high-frequency power supply and a direct current power supply are used to generate a stable inert mixed gas thermal plasma. A mixture of micron nickel powder and micron _NbB2 powder is sent into the reaction chamber at a speed of 10 m/s. When the high-energy density thermal plasma acts on the mixed powder, plasma is generated. During the diffusion process, the plasma continuously collides violently with the inert gas atoms, and then is rapidly cooled by a cooling device, spontaneously nucleates and condenses to grow into ultrafine particle clusters. After the clusters are formed, they quickly leave the supersaturated zone through gas convection, and finally deposit on the wall of the particle collection device. Due to the high melting point of _NbB2 , it first nucleates and solidifies, and nickel has a lower melting point and then nucleates on the surface of the already formed _NbB2 , thereby achieving nickel coating of _NbB2 particles.

(1c) Nickel-coated NbB ₂ particle size screening and further refinement processing:

Screening treatment: Collect the nickel-coated _NbB2 particle powder prepared in step (1b), and screen out particles below 600 nanometers as the finished product; use particles larger than 600 nanometers as raw materials and process them in step (1b) until the size of the collected nickel-coated _NbB2 particle powder is all below 600 nanometers.

(2) Vacuum induction melting of nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(2a) putting the prepared NiAl alloy raw material into a water-cooled copper crucible, and paying attention to avoiding contact between the NiAl alloy raw material and the water-cooled copper crucible wall except the bottom of the crucible, and then putting the nickel-coated _NbB2 nanoparticles obtained in step (1c) and the Al powder (containing 99.8%) required to balance the NiAl ratio into the feeding port to facilitate the subsequent work;

(2b) Before starting smelting, the vacuum degree in the smelting chamber is maintained at 15 Pa, and then inert gas is filled to keep the pressure in the smelting chamber at 12000 Pa.

(2c) The heating power is continuously increased by 4 kW each time and maintained for 7 minutes until the NiAl alloy is melted; when the NiAl alloy is completely melted, the nickel-coated _NbB2 nanoparticles at the feeding port are added into the NiAl alloy melt in the water-cooled copper crucible; the _NbB2 nanoparticles are continuously stirred by electromagnetic induction to fully disperse them in the NiAl melt, and then Al powder is added after 60 seconds, and casting is carried out after 5 minutes.

(3) Cast nickel-coated _NbB2 nanoparticles reinforced NiAl alloy:

(3a) Casting is performed using a graphite mold, which is placed in a vacuum melting chamber in advance at a distance of about 5 cm from a water-cooled copper crucible during smelting. During the smelting process, the graphite mold is fully preheated to reduce the temperature difference between the graphite mold and the cast NiAl alloy;

(3b) When the nickel-coated _NbB2 nanoparticles are evenly dispersed and Al is supplemented, casting begins. During casting, the power of the smelting furnace is gradually reduced to 0; finally, the NiAl alloy is cooled and can be used.

In this embodiment, the microstructure of NiAl-0.3wt.% _NbB2 is shown in Figure 8, which shows that the dispersion of _NbB2 ceramic particles in the nickel-aluminum matrix is good, there is no agglomeration of nanoparticles, and the interface of _NbB2 ceramic particles and the nickel-aluminum matrix is well bonded, without defects such as voids. The phase composition of 0.3wt.% nickel-coated _NbB2 nanoparticles is shown in Figure 9; the organization diagram of nickel-coated _NbB2 nanoparticles is shown in Figure 10. When the strain rate is 1.0× ^10-4 s, the yield strength, ultimate compressive strength and fracture strain at 600℃ are 349.3MPa, 441.5MPa, and 8.31% (Table 1), respectively, which are 9.0%, 10.2%, and 11.4% higher than those of NiAl alloys reinforced with no nickel-coated _NbB2 nanoparticles. Obviously, the nanoparticles do not agglomerate, have good dispersion and good interface bonding, which is conducive to the strengthening of the mechanical properties of nickel-aluminum alloys by nanoparticles.

Comparative Example 1

A blank NiAl alloy (composed of 50 at. % Ni and 50 at. % Al) was prepared by vacuum induction melting, and the specific method is as follows.

(1) Vacuum induction melting of NiAl alloy:

(1a) Put the NiAl alloy raw material into a water-cooled copper crucible, and pay attention to avoid contact between the NiAl alloy raw material and the water-cooled copper crucible wall except the bottom of the crucible;

(1b) To prevent oxidation of the material, the vacuum degree in the smelting chamber is maintained at 10 Pa, and then an inert gas is filled to maintain the pressure in the smelting chamber at 10000 Pa;

(1c) The heating power is continuously increased by 5 kW each time and maintained for 5 minutes until the NiAl alloy melts.

(2) Casting NiAl alloy:

(2a) Casting is performed using a graphite mold, which is placed in a vacuum melting chamber in advance during smelting, about 5 cm away from a water-cooled copper crucible. During the smelting process, the graphite mold is fully preheated to reduce the temperature difference between the graphite mold and the cast NiAl alloy;

(2b) Start casting and gradually reduce the power of the melting furnace to 0 during casting; finally, wait for the NiAl alloy to cool down before use.

In this comparative example, the microstructure of NiAl (as shown in FIG. 1 ) is as follows: When the strain rate is 1.0×10 ^-4 s, the yield strength, ultimate compressive strength and fracture strain at 600° C. are 320.4 MPa, 400.5 MPa and 7.46% respectively (Table 1).

Table 1 Compression performance of alloys prepared in various embodiments and comparative examples

The invention prepares nickel-coated _NbB2 nanoparticle-reinforced NiAl alloy by vacuum induction melting, and can significantly improve the performance of NiAl alloy. The preparation method provided by the invention can prepare nickel-coated nanoparticles in large quantities, and the surface coating of metal is conducive to the wetting of nanoparticles and NiAl melt, and is conducive to the dispersion of ceramic particles in the metal melt, and improves the interface bonding between ceramic particles and NiAl matrix. The preparation process of the invention is simple, easy to control and automatic; and the problem of dispersion of nanoparticles in the metal melt can be solved.

Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims (9)

1. The preparation method of the nano NbB ₂ particle reinforced NiAl alloy is characterized by comprising the following steps of:

step one, preparing nickel-coated NbB ₂ nano particles;

Secondly, placing a NiAl alloy raw material into a water-cooled copper crucible in a smelting chamber of vacuum smelting equipment, and respectively placing the nickel-coated NbB ₂ nano particles and Al powder into a feed port of the smelting chamber of the vacuum smelting equipment;

wherein the vacuum degree in the smelting chamber is kept between 5Pa and 20Pa;

step three, filling inert gas into the smelting chamber to keep the pressure of the smelting chamber at 10000 Pa-20000 Pa; heating the smelting chamber, and gradually increasing the heating power until the NiAl alloy is completely melted to obtain a NiAl alloy melt;

Step four, nickel coated NbB ₂ nano particles at a feed port are added into a NiAl alloy melt in a water-cooled copper crucible; after fully dispersing NbB ₂ nano particles in the NiAl melt by electromagnetic induction stirring, adding Al powder to obtain an enhanced NiAl alloy melt;

Wherein the mass of the NbB ₂ nano-particles accounts for 0.05 to 0.30wt.% of the total mass of the reinforced NiAl alloy melt;

Step five, in the smelting chamber, casting the reinforced NiAl alloy melt by using a grinding tool; after casting and cooling, obtaining the nano NbB ₂ particle reinforced NiAl alloy;

In the first step, nickel-coated NbB ₂ nano-particles are prepared, and the method comprises the following steps:

Step 1, mixing nickel powder and NbB ₂ powder, and homogenizing in a ball mill to obtain mixed powder;

Wherein, the grain diameter of the nickel powder is 20-200 microns, and the grain diameter of the NbB ₂ powder is 10-100 microns; in the mixed powder, the nickel powder accounts for 20-50 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; the mixed powder is sent into the vacuum reaction chamber, reacts after the thermal plasma, and is rapidly cooled to obtain nickel-coated NbB ₂ powder;

And 3, screening particles below 600 nanometers from the nickel-coated NbB ₂ powder, namely the nickel-coated NbB ₂ nanometer particles.

2. The method for producing nano NbB ₂ particle reinforced NiAl alloy according to claim 1, wherein in the step 2, the gas pressure of the vacuum reaction chamber filled with inert gas is 0.01MPa to 0.03MPa.

3. The method of preparing nano NbB ₂ particle reinforced NiAl alloy according to claim 2, wherein in step 2, the mixed powder is fed into the vacuum reaction chamber at a speed of 3 m/s to 20 m/s.

4. A method of preparing a nano NbB ₂ particle reinforced NiAl alloy according to any one of claims 1 to 3, wherein during the preparation of the NiAl alloy melt in step three, the heating power is raised by 3kW to 7kW each time and maintained for 5 to 8 minutes.

5. The method for producing nano NbB ₂ particle reinforced NiAl alloy according to claim 4, wherein in the fourth step, after the nano NbB ₂ particles are fully dispersed in the NiAl melt for 40 to 80 seconds, al powder is added.

6. The method for producing nano NbB ₂ particle reinforced NiAl alloy according to claim 5, wherein in the fourth step, casting is performed after adding Al powder for 3 to 7 minutes.

7. The method for producing nano-NbB ₂ particle reinforced NiAl alloy according to claim 6, wherein in the fifth step, the power of the melting equipment is gradually reduced to 0 during the casting process.

8. The method of preparing a nano NbB ₂ particle reinforced NiAl alloy as claimed in claim 7, wherein in the fifth step, casting is performed using a graphite mold.

9. The method of producing nano NbB ₂ particle reinforced NiAl alloy according to claim 8, wherein in step five, the method further comprises preheating the mold in a vacuum melting chamber before casting.