CN104357783A - Titanium-aluminum alloy powder material for thermal spraying and preparation method thereof - Google Patents

Abstract

The titanium-aluminum alloy powder material for thermal spraying and its preparation method can be used in different thermal spraying techniques. The powder material is based on γ-TiAl alloy, by adding Nb, Cr, and V alloying elements individually and in combination, using a vacuum consumable arc melting furnace to prepare a titanium-aluminum alloy master alloy ingot, and using the gas atomization method to achieve The γ-TiAl alloy powder material with stable β phase is prepared to achieve the purpose of improving the phase composition of the powder material. The main phase components of the new γ-TiAl-based alloy powder material are γ phase, β phase and α ₂ phase, there is no oxidation phase and nitride phase in the powder, and the sphericity is good.

Description

Titanium-aluminum alloy powder material for thermal spraying and preparation method thereof

technical field

The invention relates to a titanium-aluminum base alloy powder material containing a metastable β phase for thermal spraying and a preparation method thereof.

Background technique

Thermal spraying is an important surface engineering technology and an important means to improve the surface properties of materials. Functional coatings such as anti-corrosion, wear-resistant, heat-insulating, conductive, insulating, and sealing can be prepared through thermal spraying technology, which has been widely used in aerospace , automotive industry, information technology, optical engineering and other manufacturing and remanufacturing industries.

Titanium-aluminum binary system intermetallic compound, the density is between pure titanium and pure aluminum. It has the general characteristics of intermetallic compounds. There are not only metal bonds between atoms, but also covalent bonds. The bonding force between atoms is enhanced and the chemical bonds tend to be stable. Therefore, the corrosion resistance and friction resistance of titanium-aluminum intermetallic compounds are higher than those of general titanium alloys. Among them, γ-TiAl intermetallic compound, as a new type of lightweight structural material, has become the contemporary aerospace industry, One of the excellent candidate structural materials in civil industry and other fields.

However, covalent bonds in γ-TiAl alloy account for about 30-40%, and metal bonds account for about 60-70%. The large proportion of covalent bonds leads to the brittleness of the alloy, resulting in the single-phase γ-TiAl alloy at 0.5 %~1% room temperature plastic tensile strain has a fracture tendency, and this brittleness is mainly related to the structure of the material itself. Because γ-TiAl alloy has poor plastic deformation ability and is difficult to deposit and form, it is difficult to prepare it as a coating for surface protection of materials.

In γ-TiAl-based alloys, the metastable β phase (or B2 phase) can be introduced by adding β phase stabilizing elements such as Cr, V, Nb, Mo, W, etc. or by processing deformation. γ-TiAl-based alloys containing metastable β-phase have better plasticity. Studies have found that the β phase (or B2) phase in γ-TiAl-based alloys is a soft phase, which is often wrapped around the γ phase or expanded along the γ phase boundary during superplastic deformation, which helps The plasticity of the γ-TiAl-based alloy can be improved by enhancing the anti-debonding ability and coordinated deformation ability between the interfaces. However, due to the lag in the development of titanium-aluminum alloy powder materials for thermal spraying, the prepared titanium-aluminum coating generally has the problems of high impurity content and low coating quality. Current research shows that there is no high-purity titanium-aluminum alloy powder material suitable for thermal spraying.

Contents of the invention

The purpose of the present invention is to provide a titanium-aluminum alloy powder material for thermal spraying and a preparation method thereof to obtain a γ-TiAl-based powder material containing a metastable β phase (or B2 phase) that can be used for thermal spraying deposition.

The powder material containing metastable β phase (or B2 phase) γ-TiAl alloy involved in the present invention has the following composition (atomic ratio):

(1) Ti-45Al-7Nb-4V;

(2) Ti-45Al-7Nb-4Cr;

(3) Ti-45Al-7Nb-2V-2Cr.

The powder material containing β-phase (or B2 phase) γ-TiAl-based alloy involved in the present invention has one of the following phase compositions:

(1) The γ-TiAl phase content in the Ti-45Al-7Nb-4V alloy powder is 65wt.%～95wt.%, the α ₂ -Ti ₃ Al phase content is 0wt.%～30wt.%, the β-Ti phase content 3wt.%～6wt.%;

(2) The γ-TiAl phase content in the Ti-45Al-7Nb-4Cr alloy powder is 80wt.%～95wt.%, the α ₂ -Ti ₃ Al phase content is 0wt.%～15wt.%, the β-Ti phase content 4wt.%～7wt.%;

(3) The content of γ-TiAl phase in Ti-45Al-7Nb-2V-2Cr alloy powder is 90wt.%～95wt.%, the content of α ₂ -Ti ₃ Al phase is 0wt.%～5wt.%, β-Ti The phase content is 5wt.%～10wt.%.

The preparation steps of the thermal spraying containing metastable β phase (or B2 phase) γ-TiAl based alloy powder material involved in the present invention are as follows:

(1) The γ-TiAl-based alloy master alloy is prepared in a vacuum consumable arc melting furnace, and the specific steps are as follows:

1) Ti rods, Al grains, and master alloys AlNb, AlV, and AlCr with a purity of more than 99.9% were respectively divided into atomic ratios Ti-45Al-7Nb-4V, Ti-45Al-7Nb-4Cr, and Ti-45Al-7Nb-2V- 2Cr for proportioning;

2) Compress the prepared raw materials into consumable electrodes;

3) The master alloy is prepared by homogenizing three times in a vacuum consumable arc melting furnace. The process parameters are current 5-8kA, voltage 24-40V, vacuum 6×10 ^-2 Pa first, and argon protection during the melting process. , each smelting holding time is 10min.

(2) Preparation of metastable β-phase γ-TiAl-based alloy powder materials using gas atomization equipment

1) Put the γ-TiAl-based master alloy ingot prepared in step 1 into the induction furnace of the gas atomization equipment, and evacuate to 10 ^-2 Pa;

2) Heating the γ-TiAl-based master alloy to melting with an induction coil, with a heating power of 40-50kw and a holding time of 20 minutes;

3) Let the melted γ-TiAl-based master alloy pass through the small hole in the bottom of the furnace to form a metal liquid flow with a diameter of 4 to 6 mm, and pass high-pressure argon gas through the annular nozzle to crush the metal liquid flow to form dispersed powder. 12MPa, the final γ-TiAl-based alloy powder material containing metastable β phase is obtained.

The invention further optimizes the structure and performance of the γ-TiAl-based alloy powder, and can prepare γ-TiAl-based alloy powder materials with uniform structure, high sphericity, good fluidity, and low oxygen and nitrogen content, and can obtain different particle size distributions at the same time. The powder material can be used for deposition forming of different thermal spraying techniques, expanding the application range of titanium-aluminum alloy.

Beneficial effects of the present invention: take γ-TiAl alloy as the matrix, add Nb, Cr, V alloy elements individually and compositely, and adopt gas atomization method to realize the preparation of γ-TiAl alloy powder material containing metastable β phase, realize The purpose of improving the phase composition and mechanical properties of powder materials.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Fig. 2 is an SEM image of the as-cast structure of the titanium-aluminum alloy of Example 1.

Fig. 3 is a microscopic morphology diagram of the titanium-aluminum alloy powder in Example 1.

Fig. 4 is a diagram of elastic modulus of titanium-aluminum alloy powders with different particle sizes in Example 1.

Fig. 5 is a metallographic structure diagram of the titanium-aluminum alloy powder in Example 2.

Fig. 6 is an XRD pattern of the titanium-aluminum alloy powder material in Example 2.

Fig. 7 is a diagram of the elastic modulus of titanium-aluminum alloy powders with different particle sizes in Example 2.

Fig. 8 is a particle size distribution diagram of the titanium-aluminum alloy powder in Example 3.

Fig. 9 is a diagram of elastic modulus of titanium-aluminum alloy powders with different particle sizes in Example 3.

Detailed ways

The present invention is realized through the following measures:

Embodiment one:

1) Proportion Ti rods, Al grains, and intermediate alloys AlNb and AlV with a purity of more than 99.9% according to the atomic ratio Ti-45Al-7Nb-4V, and press the prepared raw materials into self-consumable electrodes. The Ti-45Al-7Nb-4V master alloy ingot was prepared by three times of homogenized melting in an electric arc melting furnace. The microstructure of the titanium-aluminum alloy ingot is shown in Figure 2, and the β phase is precipitated at the grain boundary, as indicated by the arrow in the figure Show. The master alloy smelting process parameters are: current 6kA, voltage 30V, vacuum 6×10 ^-2 Pa first, argon protection in the smelting process, and holding time of 10 minutes for each smelting.

2) Put the γ-TiAl-based master alloy ingot prepared in step 1 into the induction furnace of the gas atomization equipment, and evacuate to 10 ^-2 Pa; use the induction coil to heat the γ-TiAl-based master alloy until it melts, and the heating power 50kw, holding time 20min; let the melted γ-TiAl-based master alloy pass through the small hole in the bottom of the furnace to form a metal liquid flow with a diameter of 5mm, and pass high-pressure argon gas through the annular nozzle to crush the metal liquid flow to form dispersed powder. 9MPa, finally obtained the metastable β-phase γ-TiAl-based alloy powder material. Figure 3 shows the microscopic morphology of titanium-aluminum alloy powder. It can be seen from the figure that the titanium-aluminum alloy powder has better sphericity, which is conducive to improving the fluidity of the powder. Figure 4 shows titanium aluminum alloys with different particle sizes Alloy powder elastic modulus diagram, the powder elastic modulus increases with the particle size of the powder increases.

Embodiment two:

1) Proportion Ti rods, Al grains, and intermediate alloys AlNb and AlCr with a purity of more than 99.9% according to the atomic ratio Ti-45Al-7Nb-4Cr, and press the prepared raw materials into self-consumable electrodes. The ingots of Ti-45Al-7Nb-4Cr master alloy were prepared by homogenizing three times in an electric arc melting furnace. The process parameters were current 5kA, voltage 40V, vacuum 6×10 ^-2 Pa first, and argon protection during the melting process. The holding time for each smelting is 10min.

2) Put the γ-TiAl-based master alloy ingot prepared in step 1 into the induction furnace of the gas atomization equipment, and evacuate to 10 ^-2 Pa; use the induction coil to heat the γ-TiAl-based master alloy until it melts, and the heating power 45kw, holding time 20min; make the melted γ-TiAl-based master alloy pass through the small hole in the bottom of the furnace to form a metal liquid flow with a diameter of 6mm, and pass high-pressure argon gas through the annular nozzle to crush the metal liquid flow to form dispersed powder. 10MPa, the final γ-TiAl-based alloy powder material containing metastable β phase is obtained. Figure 5 shows the metallographic structure of the polished surface of the titanium-aluminum alloy powder. It can be seen from the figure that the powder structure is a fine columnar crystal. Figure 6 shows the XRD diffraction patterns of titanium-aluminum alloy powders in different particle size ranges. It can be seen from the test results that the powder is mainly composed of γ phase, β phase (B2 phase) and α ₂ phase, and there is no oxidized phase and phase in the powder. nitrided phase. Figure 7 is a diagram of the elastic modulus of titanium-aluminum alloy powders with different particle sizes, and the elastic modulus of the powder increases with the particle size of the powder.

Embodiment three:

1) Proportion Ti rods, Al grains, and intermediate alloys AlNb, AlCr, and AlV with a purity of more than 99.9% according to the atomic ratio Ti-45Al-7Nb-2V-2Cr, and press the prepared raw materials into consumable electrodes, In a vacuum consumable arc melting furnace, the Ti-45Al-7Nb-2V-2Cr master alloy ingot was prepared by three ^times of homogenization melting. Argon protection was introduced, and the holding time for each smelting was 10 minutes.

2) Put the γ-TiAl-based master alloy ingot prepared in step 1 into the induction furnace of the gas atomization equipment, and evacuate to 10 ^-2 Pa; use the induction coil to heat the γ-TiAl-based master alloy until it melts, and the heating power 40kw, holding time 20min; let the melted γ-TiAl-based master alloy pass through the small hole in the bottom of the furnace to form a metal liquid flow with a diameter of 4mm, and pass high-pressure argon gas through the annular nozzle to crush the metal liquid flow to form dispersed powder. 8MPa, the final γ-TiAl-based alloy powder material containing metastable β phase is obtained. Figure 8 shows the particle size distribution range of titanium-aluminum alloy powder measured by sieving method. Figure 9 is a diagram of the elastic modulus of titanium-aluminum alloy powders with different particle sizes, and the elastic modulus of the powder increases with the increase of the particle size of the powder.

Claims (3)

1. titanium aluminum alloy powder body material used for hot spraying, it is characterized in that having following atom composition: Ti-45Al-7Nb-4V, or Ti-45Al-7Nb-4Cr, or Ti-45Al-7Nb-2V-2Cr, described powder body material is containing γ-TiAl phase and β-Ti phase.

2. titanium aluminum alloy powder body material used for hot spraying according to claim 1, is characterized in that: in Ti-45Al-7Nb-4V alloy powder, γ-TiAl phase content is 65wt.% ~ 95wt.%, α ₂-Ti ₃al phase content is 0wt.% ~ 30wt.%, β-Ti phase content is 3wt.% ~ 6wt.%; In Ti-45Al-7Nb-4Cr alloy powder, γ-TiAl phase content is 80wt.% ~ 95wt.%, α ₂-Ti ₃al phase content is 0wt.% ~ 15wt.%, β-Ti phase content is 4wt.% ~ 7wt.%; In Ti-45Al-7Nb-2V-2Cr alloy powder, γ-TiAl phase content is 90wt.% ~ 95wt.%, α ₂-Ti ₃al phase content is 0wt.% ~ 5wt.%, β-Ti phase content is 5wt.% ~ 10wt.%.

3. the preparation method of titanium aluminum alloy powder body material used for hot spraying according to claim 1, is characterized in that carrying out according to the following steps:

(1) adopt vacuum consumable arc-melting stove to prepare alloy mother alloy, concrete steps are as follows:

1) by purity be more than 99.9% Ti rod, Al grain and master alloy AlNb, AlV, AlCr carry out proportioning by atomic ratio Ti-45Al-7Nb-4V, Ti-45Al-7Nb-4Cr and Ti-45Al-7Nb-2V-2Cr respectively;

2) starting material prepared are compressed to consumable electrode;

3) in vacuum consumable arc-melting stove, carry out three times homogenizing meltings and prepare mother alloy, processing parameter is electric current 5 ~ 8kA, voltage 24 ~ 40V, first vacuumize 6 × 10 ^-2pa, fusion process passes into argon shield, each melting soaking time 10min;

(2) adopt aerosolizing device preparation containing metastable β phase γ-TiAl-base alloy powder body material:

1) γ-TiAl base mother alloy ingot step one prepared puts into the induction furnace of aerosolizing device, is evacuated to 10 ^-2pa;

2) ruhmkorff coil is utilized γ-TiAl base mother alloy to be heated to fusing, heating power 40 ~ 50kw, soaking time 20min;

3) make the γ-TiAl base mother alloy after fusing by furnace bottom aperture, form the metal liquid stream of 4 ~ 6mm diameter, pass into high pressure argon gas by ring nozzle and smash metal liquid stream formation dispersed powders, argon pressure 8 ~ 12MPa, finally obtains containing metastable β phase γ-TiAl-base alloy powder body material.