CN103949640B - A kind of electron beam RP technique is prepared the method for Nb-Si based ultra-high temperature alloy - Google Patents

Abstract

The invention belongs to high temperature alloy preparing technical field, do you be particularly related to a kind of electron beam RP technique (electron? beam? melting, EBM) prepare the method for NbSi based ultra-high temperature alloy, utilize electron beam constituency rapid forming equipment, by rational technological parameter is set, directly completed the preparation of NbSi alloy three-dimensional drip molding by cad model one step, the NbSi base alloy density obtaining is high, mainly by Nb_ssSolid solution and Nb₅Si₃Hardening constituent composition, phase size is tiny, and (<1 μ m) and be evenly distributed. This method is prepared NbSi alloy process without mould, reduces alloy and pollutes, and reduces and is mingled with content, and stock utilization is high, can improve mechanical property and the production efficiency of NbSi based ultra-high temperature alloy.

Description

A method for preparing Nb-Si-based super high temperature alloy by electron beam rapid prototyping technology

technical field

The invention belongs to the technical field of high-temperature alloy preparation, and in particular relates to a method for preparing NbSi super-high-temperature alloy by electron beam rapid forming.

Background technique

Gas turbine engines play a pivotal role in aerospace, energy power, transportation and other fields. Their efficiency and performance are inseparable from high-temperature structural materials. In recent years, environmental problems such as global warming caused by greenhouse gas emissions have increasingly caused People's attention, so improving energy utilization efficiency, energy saving and emission reduction has far-reaching significance. At present, the energy utilization efficiency achieved by gas turbine engines is about 40%. If it is to be further improved, it is necessary to develop high-temperature structural materials with higher temperature bearing capacity.

At present, the maximum service temperature of nickel-based superalloys commonly used in hot end parts of gas turbine engines has exceeded 1100 °C, reaching 85% of the melting point of pure nickel, and there is little potential for further improvement. Therefore, it is necessary to develop a new generation of high-temperature structural materials. The melting point of the Nb-Si ultra-high temperature structural material is higher than 1750°C, and its density is relatively low (only 80-90% of the density of the Ni-based superalloy). Therefore, Nb-Si ultra-high temperature structural materials are expected to become the structural materials used in the new generation of turbine engines at 1200-1400 °C or even higher temperatures.

At present, the forming methods of Nb-Si super high temperature alloy mainly include vacuum non-consumable/consumable arc melting, vacuum induction melting, directional solidification, powder metallurgy and investment casting. The NbSi alloy obtained by vacuum arc melting often has composition segregation phenomenon, which is prone to coarse primary phase, Nb ₃ Si metastable phase and cracks, etc. The content of oxygen and other impurities is high, which is not conducive to the direct application of high temperature structural materials. When powder metallurgy NbSi alloy, the stress generated during sintering and cooling can easily lead to cracks, thus affecting the overall performance of the alloy. At the same time, the sintering temperature has a great influence on the alloy structure. The sintering temperature is different, and the structure of the obtained product is also different. The particle size is different, and the composition phase may also be different (such as the appearance of Nb ₃ Si phase); vacuum induction melting can keep the alloy composition uniform and high purity, but the disadvantage is that the melt temperature is uneven, the superheat is low, and it is easy to form defects such as insufficient casting. Directional solidification can eliminate most of the transverse grain boundaries, effectively control the microstructure and chemical composition of the alloy, and obtain low-defect castings. It is gradually becoming the main process for preparing niobium-silicon superalloys. However, the disadvantages of traditional directional solidification mainly include: the cooling rate is low during the solidification process, which leads to the coarsening and growth of the alloy structure, which limits the improvement of the alloy performance. Elements, so it is very easy to have interface reaction with the contacting crucible at high temperature, causing alloy pollution, increased oxygen content, increased casting inclusions, and decreased mechanical properties. Investment casting of Nb-Si based alloys has a shell temperature capacity exceeding 2000°C. However, the shell temperature capacity currently used for investment casting of high-temperature structural materials does not exceed 1700°C. Alloy reaction, it is difficult to meet the Nb-Si based alloy investment casting requirements.

Not only that, the preparation of NbSi alloys by the above methods requires crucibles or molds, so it is difficult to directly prepare alloy parts with specific dimensions and complex shapes and structures (variable cross-sections, inner cavities or cooling channels), often requiring more machining And post-processing, the process is cumbersome, the production efficiency is low, and it is easy to cause waste of alloy materials. Therefore, it is undoubtedly crucial to develop a more efficient method for preparing Nb-Si-based superalloys.

Contents of the invention

In order to overcome the above problems, the present invention provides a method for preparing NbSi-based super high temperature alloy by using electron beam rapid forming technology (electron beam melting, EBM). The EBM method first uses the computer to obtain the three-dimensional CAD solid model of the formed part, and then uses the layering software to perform layered slices in the height direction of the part, and converts the three-dimensional contour information of the part into two-dimensional contour information, and generates a scanning path. The high-energy electron beam emitted by the electron gun melts and deposits the preset metal or alloy powder layer by layer according to the specified scanning path, and accumulates layers to form three-dimensional alloy parts. Therefore, EBM is especially suitable for the preparation of difficult-to-process and high-performance refractory metals and alloys.

The technical scheme that the present invention utilizes EBM technology to prepare NbSi super high temperature alloy is:

The pre-alloyed NbSi powder prepared by the argon atomization method in the present invention is spherical or nearly spherical, and the diameter should be between 50 and 150 μm. Subsequently, the Nb-Si based pre-alloyed powders were prepared by rapid prototyping using electron beam rapid prototyping (electron beam melting, EBM) process. Set reasonable electron beam forming parameters (electron beam scanning speed, electron beam current, scanning distance, substrate preheating temperature and powder coating thickness), and use high-energy electron beams to melt NbSi alloy powder. In addition, in the electron beam rapid prototyping process, the powder melting/solidification is extremely fast, and the cooling rate is extremely high (10 ⁵ ~ 10 ⁶ K/s), and a fine, uniform, and stable rapid solidification alloy structure can be prepared, so as to obtain comprehensive mechanical properties. NbSi super high temperature alloy parts with excellent performance.

The invention introduces a method for preparing NbSi-based ultra-high temperature alloy by using EBM technology, which is characterized in that the preparation process includes the following steps:

(1). According to the shape of the NbSi alloy to be processed, use the three-dimensional drawing software (Magics) to establish the alloy CAD model, and save it as an STL file; then use the layering software (EBMassembler) to perform layered slice processing on the STL file in the height direction, Divided into slices with uniform thickness (0.05-0.1mm), the slices contain the cross-sectional profile information and processing path of the alloy sample; use the layering software to save the slices as ABF files, and import them into the electron beam rapid prototyping equipment (EBM);

(2). Load NbSi alloy powder, place the forming substrate on a liftable platform in the forming cavity, and vacuum the forming cavity to 10 ^-3 Pa ~ 10 ^-2 Pa;

(3). The electron beam preheats the substrate, and the preheating temperature is between 900 and 1100°C; the substrate preheating parameters: the electron beam scanning speed is 10000 to 12000mm/s, the electron beam current is 40mA, and the scanning distance is 0.05 to 0.2 mm; After the preheating of the substrate is completed, the powder scraping device evenly spreads a layer of NbSi super high temperature alloy powder with a thickness of 0.05-0.1mm on the substrate

(4). The electron beam preheats all the powders on the substrate until the temperature of the powder is the same as that of the substrate; the powder preheating parameters are: preheating 6 to 10 times, the scanning speed of the electron beam is 6000mm/s~8000mm/s, the electron beam The beam current is 30-40mA, and the scanning distance is 0.05-0.2mm;

(5). After the powder preheating is completed, the electron beam selectively scans the powder on the substrate according to the preset scanning path, and the powder melts and solidifies to form a cladding layer; powder melting parameters: melting once, electron The beam scanning speed is 400-600mm/s, the melting current is 8-12mA, and the scanning distance is 0.05-0.2mm;

(6). After the processing of one layer is completed, the forming substrate is lowered by a layer thickness, and the powder scraping device evenly spreads a layer of NbSi alloy powder with a thickness of 0.05-0.1mm on the first cladding layer;

Repeat the above steps (4), (5), and (6) until the processing of the NbSi alloy is completed; after the processing is completed, pour argon gas into the forming cavity to speed up the cooling of the formed part until the temperature of the formed part drops below 100 °C , take out and cool to room temperature;

In the present invention, the preparation process of NbSi ultra-high temperature alloy includes substrate preheating, powder preheating and melting process. The preheating process is to prevent powder splashing, promote powder pre-sintering, and at the same time maintain the forming at a higher temperature to reduce internal stress;

In the present invention, the NbSi ultra-high temperature alloy is prepared, and the accelerating voltage of the electron beam is maintained at 60kV;

In the present invention, the NbSi super high temperature alloy is prepared, and the powder coating thickness is 0.05 mm to 0.1 mm;

In the present invention, the Ti6Al4V forming substrate is used to prepare the NbSi super high temperature alloy, and the thickness is 10mm;

In the present invention, the NbSi super high temperature alloy is prepared, and the vacuum degree in the forming area is maintained at 10 ^-3 Pa to 10 ^-2 Pa;

In the present invention, the preheating temperature of the forming substrate and the powder is the same, and is controlled between 900-1100°C according to different alloy compositions;

In the present invention, argon atomization is used to prepare powder and EBM rapid prototyping process to prepare NbSi-based ultra-high temperature alloy. The interaction between powder and electron beam is different from other traditional method preparation processes, and its melting/solidification behavior is different from that of Traditional method; the main advantages of this technical solution are:

(1) Preparation of NbSi super high temperature alloy by EBM technology The preparation of NbSi alloy formed parts is completed in one step directly from the CAD model. The preparation process does not need to prepare crucibles, molds or powder jackets, etc., which can effectively avoid the interface reaction between superalloys and crucibles, molds, etc., reduce alloy pollution, and reduce inclusion content;

(2) The increase of oxygen content in NbSi alloy will reduce the performance of the alloy, and the high vacuum environment adopted by electron beam rapid prototyping has a better protective effect on the NbSi alloy in high temperature state, which can effectively avoid the oxidation of the alloy. It has a purification effect and can improve the performance of NbSi alloy;

(3) NbSi ultra-high temperature alloy prepared by EBM technology, when the powder is melted, the size of the molten pool is very small, and the solidification time is extremely short, so the cooling rate is extremely high (10 ⁵ ~ 10 ⁶ K/s), which is highly non-equilibrium solidification, and the solidification time is extremely short. Short, can effectively reduce the micro-segregation of NbSi alloy, and the alloy has high density, has a small, uniform and stable rapid solidification structure, so as to obtain NbSi super high temperature alloy with excellent mechanical properties;

(4) NbSi superalloy is a brittle material, so it is very important to preheat the powder. The temperature of the matrix is always maintained at about 900-1100°C during forming. On the one hand, it is equivalent to heat treatment, which reduces the internal thermal stress of NbSi superalloy , to prevent deformation, which is conducive to a good match between the strength and plasticity of the parts; on the other hand, it is conducive to the uniformity of the alloy structure and properties;

(5) EBM technology is suitable for preparing NbSi alloy parts with various complex structures, especially alloy parts with complex special-shaped structures (cavity, cooling channel) inside, which cannot be manufactured by traditional methods; the preparation process of NbSi alloy is simple and fast, eliminating the need for The process of designing and manufacturing molds is simplified, traditional machining and post-processing are avoided, and manpower and material resources are saved; at the same time, unprocessed and redundant NbSi pre-alloyed powders can be recycled and reused, and the material utilization rate is high.

The NbSi super high temperature alloy prepared by SLM technology has high density (>95%) and no defects such as voids and hot cracks. The prepared super high temperature alloy is mainly composed of Nbss solid solution and Nb ₅ Si ₃ strengthening phase. The phase size is extremely small (<1 μm), close to nanoscale, and evenly distributed, which can improve the comprehensive mechanical properties of NbSi based super high temperature alloy.

Description of drawings:

Figure 1 is the XRD pattern of Nb-18Si-24Ti-2Cr-2Al-2Hf alloy formed by EBM technology;

Figure 2 is a scanning electron microscope picture of Nb-18Si-24Ti-2Cr-2Al-2Hf alloy formed by EBM technology;

Figure 3 is the XRD pattern of the Nb-16Si-22Ti-4Cr-2Al-2Hf alloy formed by EBM technology;

Figure 4 is a scanning electron microscope image of Nb-16Si-22Ti-4Cr-2Al-2Hf alloy formed by EBM technology.

detailed description

The present invention is described further below in conjunction with example, but the present invention is not limited to specific embodiment.

Example 1:

Nb-18Si-24Ti-2Cr-2Al-2Hf (at.%, atomic percent) superalloy prepared by EBM technology:

(1). Nb-18Si-24Ti-2Cr-2Al-2Hf pre-alloyed powder prepared by argon atomization method, the powder is spherical or nearly spherical, and the diameter is between 50 and 150 μm;

(2). First use the three-dimensional drawing software (Magics) to establish the three-dimensional CAD model of the NbSi alloy sample, and save it as an STL file; then use the layering software (EBMassembler) to carry out layered slice processing on the STL file in the height direction, and divide it into A slice with a uniform thickness (0.1mm), which contains the cross-sectional profile information of the alloy sample; use the layering software to save the slice as an ABF file, and import it into the electron beam rapid prototyping equipment (EBM);

(3). Put the Nb-18Si-24Ti-2Cr-2Al-2Hf pre-alloyed powder into the molding cavity, put the Ti6Al4V forming substrate with a thickness of 10mm on the platform that can be lifted in the forming cavity, and vacuum the forming cavity to 10 ^-3Pa ～ ^10-2Pa ;

(4). The electron beam preheats Ti6Al4V, and the preheating temperature reaches 1000°C; the substrate preheating parameters: the electron beam scanning speed is 12000mm/s, the electron beam current is 40mA, and the scanning distance is 0.20mm; after the substrate preheating is completed, The powder scraping device evenly spreads a layer of alloy powder with a thickness of 0.1mm on the substrate;

(5). The electron beam preheats all the powders on the substrate until the powder temperature reaches 1000°C; the powder preheating parameters are: preheating 8 times, the electron beam scanning speed is 6500mm/s, the electron beam current is 30mA, and the scanning Spacing 0.20mm;

(6). After the powder preheating is completed, the electron beam selectively scans the powder on the substrate according to the preset scanning path, and the powder melts and solidifies to form a cladding layer; powder melting parameters: melting once, electron The beam scanning speed is 500mm/s, the melting current is 9mA, and the scanning distance is 0.10mm;

(7). After completing the processing of one layer, the forming substrate is lowered by a layer thickness distance (0.1mm), and the powder scraping device evenly spreads a layer of NbSi alloy powder with a thickness of 0.1mm on the first cladding layer;

Repeat the above steps (5), (6), (7) until the processing of the Nb-18Si-24Ti-2Cr-2Al-2Hf alloy is completed; When the temperature of the formed part drops below 100°C, take it out and cool it to room temperature;

It can be seen from Figure 1 and Figure 2 that the SLM formed Nb-18Si-24Ti-2Cr-2Al-2Hf alloy has high density, a small amount of pores (size <1μm), and no defects such as voids and hot cracks. The alloy prepared by SLM technology is composed of nanoscale Nbss phase and Nb ₅ Si ₃ phase (the light phase is Nbss solid solution, and the dark phase is Nb ₅ Si ₃ phase), the size is extremely small (<1μm), and the two phases are evenly distributed, showing The obvious rapid solidification structure characteristics can improve the comprehensive performance of NbSi super high temperature alloy.

Example 2

Nb-16Si-22Ti-4Cr-2Al-2Hf (at.%, atomic percent) superalloy prepared by EBM technology:

(1). Nb-16Si-22Ti-4Cr-2Al-2Hf pre-alloyed powder prepared by argon atomization method, the powder is spherical or nearly spherical, and the diameter is between 50 and 150 μm;

(2). First use the three-dimensional drawing software (Magics) to establish the three-dimensional CAD model of the NbSi alloy sample, and save it as an STL file; then use the layering software (EBMassembler) to carry out layered slice processing on the STL file in the height direction, and divide it into A slice with a uniform thickness (0.07mm), which contains the cross-sectional profile information of the alloy sample; use the layering software to save the slice as an ABF file, and import it into the electron beam rapid prototyping equipment (EBM);

(3). Put the Nb-16Si-22Ti-4Cr-2Al-2Hf pre-alloyed powder into the forming cavity, put the Ti6Al4V forming substrate with a thickness of 10mm on the platform that can be lifted in the forming cavity, and vacuum the forming cavity to 10 ^-3Pa ～ ^10-2Pa ;

(4). The electron beam preheats Ti6Al4V, and the preheating temperature reaches 900°C; the substrate preheating parameters: the electron beam scanning speed is 12000mm/s, the electron beam current is 40mA, and the scanning distance is 0.20mm; after the substrate preheating is completed, The powder scraping device evenly spreads a layer of alloy powder with a thickness of 0.07mm on the substrate;

(5). The electron beam preheats all the powders on the substrate until the powder temperature reaches 950°C; the powder preheating parameters are: preheating 9 times, the electron beam scanning speed is 8000mm/s, the electron beam current is 35mA, and the scanning Spacing 0.15mm;

(6). After the powder preheating is completed, the electron beam selectively scans the powder on the substrate according to the preset scanning path, and the powder melts and solidifies to form a cladding layer; powder melting parameters: melting once, electron The beam scanning speed is 650mm/s, the melting current is 8mA, and the scanning distance is 0.08mm;

(7). After completing the processing of one layer, the forming substrate is lowered by a layer thickness (0.07mm), and the powder scraping device is evenly spread a layer of NbSi alloy powder with a thickness of 0.07mm on the first cladding layer;

Repeat the above steps (5), (6), (7) until the processing of the Nb-16Si-22Ti-4Cr-2Al-2Hf alloy is completed; When the temperature of the formed part drops below 100°C, take it out and cool it to room temperature;

It can be seen from Figure 3 and Figure 4 that the SLM formed Nb-16Si-22Ti-4Cr-2Al-2Hf alloy has a high density and no defects such as pores, voids and thermal cracks. The alloy is composed of nanoscale Nbss phase and Nb ₅ Si ₃ phase, the size is very small (<1 μm), the distribution of the two phases is very uniform, and it presents obvious characteristics of rapid solidification structure, which can improve the comprehensive performance of NbSi-based ultra-high temperature alloy.

The above is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process conversion made by using the content of the description of the present invention, or directly or indirectly used in other related technical fields, All are included in the scope of patent protection of the present invention in the same way.

Claims (15)

1. a method utilizing electron beam rapid prototyping technology to prepare NbSi super high temperature alloy, is characterized in that, preparation process comprises the following steps: (1). According to the shape of the NbSi alloy forming part to be processed, the CAD model of the forming part is established, and then it is layered and sliced in the height direction to be divided into slices with uniform thickness. The slice contains the cross-sectional profile information of the alloy sample and Process the path, and import the slice file into the electron beam selection rapid prototyping equipment, the thickness of the slice is 0.05-0.1mm; (2). NbSi alloy powder is loaded into the electron beam selective area rapid prototyping equipment, and the Ti6Al4V forming substrate is placed on the liftable platform in the forming cavity of the electron beam selective area rapid prototyping equipment, and the forming cavity is evacuated. The selected NbSi alloy powder is prepared by argon atomization method, spherical or nearly spherical, with a diameter of 50-150 μm; (3). Use electron beams to preheat the substrate. After the preheating is completed, a powder scraping device evenly spreads a layer of NbSi alloy powder on the substrate. The thickness of the powder is equal to the thickness of the slice in step (1); (4).Use electron beams to preheat all the powders on the substrate; (5). After the powder preheating is completed, the electron beam selectively scans the alloy powder on the substrate according to the preset scanning path, and the powder melts and solidifies to form a cladding layer; (6). After completing the processing of one layer in step (5), the forming substrate is lowered by a layer thickness, and the powder scraping device is evenly laid one layer of NbSi alloy powder on the cladding layer formed in step (5); (7). Repeat the above steps (4)-(6) until the processing of the NbSi alloy is completed; after the processing is completed, pour the protective gas into the forming cavity to speed up the cooling of the formed part until the temperature of the formed part drops below 100 °C , remove and cool to room temperature. 2. a kind of method utilizing electron beam rapid prototyping technology to prepare NbSi super high temperature alloy according to claim 1, is characterized in that, described NbSi alloy powder composition is Nb-18Si-24Ti-2Cr-2Al in atomic percent -2Hf. 3. a kind of method utilizing electron beam rapid prototyping technology to prepare NbSi super high temperature alloy according to claim 1, is characterized in that, described NbSi alloy powder composition is Nb-16Si-22Ti-4Cr-2Al in atomic percent -2Hf. 4. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to any one of claims 1-3, characterized in that, the formed part obtained by cooling to room temperature has a density>95%, and the main structure is composed of Nb _ss solid solution and Nb ₅ Si ₃ strengthening phase composition, phase size <1μm and uniform distribution. 5. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1, characterized in that the thickness of the Ti6Al4V formed substrate is 10 mm. 6 . A method for preparing NbSi superalloys using electron beam rapid prototyping technology according to claim 1 , wherein the electron beam accelerating voltage of the electron beam selective area rapid prototyping equipment is maintained at 60 kV. 7. A method for preparing NbSi super high temperature alloy by using electron beam rapid prototyping technology according to claim 1, characterized in that the vacuum degree in the forming cavity after vacuuming in step (2) is 10 ⁻³ Pa～10 ^-2 Pa. 8. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1, characterized in that, in step (3), the preheating temperature of the substrate is 900-1100°C. 9. A kind of method utilizing electron beam rapid prototyping technology to prepare NbSi super high temperature alloy according to claim 1 or 8, is characterized in that, in step (3), the preheating parameter of substrate is: electron beam scanning speed is 10000 ～12000mm/s, the electron beam current is 40mA, and the scanning distance is 0.05～0.2mm. 10. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1, characterized in that, in step (4), the preheating temperature of the alloy powder is between 900-1100°C. 11. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1 or 10, characterized in that, in step (4), the powder preheating parameters are: preheating 6 to 10 times, The electron beam scanning speed is 6000mm/s～8000mm/s, the electron beam current is 30～40mA, and the scanning distance is 0.05～0.2mm. 12. A method for preparing NbSi super high temperature alloy by using electron beam rapid prototyping technology according to claim 1, characterized in that, in step (3), the thickness of the NbSi alloy powder evenly laid on the substrate is 0.05-0.1mm . 13. A method for preparing NbSi superalloys using electron beam rapid prototyping technology according to claim 1, characterized in that in step (5), the powder melting parameters: melting once, the electron beam scanning speed is 400 ~ 600mm/s, the melting current is 8-12mA, and the scanning distance is 0.05-0.2mm. 14. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1, characterized in that, in step (6), the thickness of the NbSi alloy powder laid evenly is 0.05-0.1 mm. 15. A method for preparing NbSi super high temperature alloy by electron beam rapid prototyping technology according to claim 1, characterized in that, in step (7), the protective gas is argon.