CN103949639B - The method that a kind of selective laser smelting technology prepares Nb-Si based ultra-high temperature alloy - Google Patents

Abstract

The invention belongs to the technical field of high-temperature alloy preparation, and in particular relates to a method for preparing NbSi ultra-high-temperature alloy by selective laser melting technology (Selective Laser Melting, SLM). Using laser selective melting equipment, through reasonable process parameter settings, the CAD model can be directly processed in one step. The preparation of NbSi alloy formed parts is completed. The prepared NbSi alloy has high density and few defects. It is mainly composed of Nbss solid solution and Nb ₅ Si ₃ strengthening phase, and the phase size is fine and evenly distributed. The method prepares the NbSi alloy without mold, avoids interface reaction, reduces alloy pollution, reduces inclusion content, has high material utilization rate, and can improve the comprehensive performance and production efficiency of the NbSi alloy.

Description

A method of preparing Nb-Si-based super high temperature alloy by laser selective melting 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 using laser selective melting technology.

Background technique

With the development of high-performance aero-engines and gas turbines in the direction of high flow ratio, high thrust-to-weight ratio, and high inlet temperature, the operating temperature of hot-end components such as turbine blades continues to increase, and the turbine inlet temperature also continues to increase. At present, the maximum service temperature of the third-generation nickel-based single crystal superalloy used in jet engines has reached 1100-1150 °C, which is close to 85% of the melting point of the alloy, and there is little potential for further improvement. Therefore, it is urgent to develop new structures. Material. At present, refractory silicides have become a hot spot in the research field of ultra-high temperature structural materials due to their excellent comprehensive properties, and among them, Nb-Si-based ultra-high temperature alloys have high melting point (>1750°C), low density (6.6-7.2g/ cm ³ ), good high-temperature strength, certain fracture toughness, fatigue performance and machinability, etc., has become one of the highly competitive new high-temperature metal structural materials. Nb-Si-based alloys are composed of Nb _SS solid solution and intermetallic compound Nb ₅ Si ₃ , relying on high toughness Nb _SS solid solution to withstand plastic deformation, improve room temperature fracture toughness, and rely on hard and brittle silicide phase Nb ₅ Si ₃ to withstand high temperature Mechanical load, improve high temperature strength.

In recent years, the research of NbSi super high temperature alloy has focused on alloy design and preparation process. The alloying design is mainly to add Ti, Al, Hf, Cr, platinum group metals (Re, Ru, etc.), Wo, Ta, Mo, rare earth elements (Ho, Dy, Y), B, C, Ge, Zr, V, Sn, N, Fe, In. The addition of alloying elements can significantly improve the matching among properties such as room temperature fracture toughness, high temperature creep strength and high temperature oxidation resistance. In terms of preparation technology, due to its high melting point, easy oxidation, brittle phase, and a large amount of highly active elements such as Ti and Hf, the preparation technology of Nb-Si-based alloys is greatly limited. At present, there are mainly vacuum non-consumable/consumable Arc melting, vacuum induction melting, directional solidification, powder metallurgy and investment casting, etc. The structure of 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., and 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, which will affect the overall performance of the alloy. Different, the composition phase may also be different (such as the appearance of Nb ₃ Si phase); vacuum induction melting can maintain uniform composition and high purity of the alloy, but the disadvantages are uneven melt temperature, low superheat, and 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 low cooling rate 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. For investment casting of Nb-Si based alloys, the shell temperature capacity will exceed 2000°C. However, the shell temperature capacity currently used for investment casting of high-temperature structural materials does not exceed 1700°C. It is difficult to meet the requirements of Nb-Si based alloy investment casting.

Not only that, the preparation of NbSi alloys by the above methods requires crucibles or molds, and it is difficult to directly prepare alloy parts with specific dimensions and complex 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

The present invention is aimed at the problems existing in the preparation of NbSi-based super high-temperature alloys by traditional methods, and provides a method for rapidly preparing NbSi-based super high-temperature alloys by selective laser melting technology (Selective Laser Melting, SLM).

Selective laser melting (SLM) technology is the latest advanced manufacturing technology that combines laser cladding and rapid prototyping (rapid prototyping) technology. SLM can realize the mold-free and high-performance rapid preparation of three-dimensional complex structural parts. The main process is: use the computer to obtain the three-dimensional CAD solid model of the part, and then use the layering software to slice in the height direction of the part, convert the three-dimensional contour information of the part into two-dimensional contour information, and generate a scanning path. The laser beam melts and deposits metal or alloy powder layer by layer according to the specified scanning path, and accumulates to form a three-dimensional solid part. After material and process optimization, the density of one-time forming can be higher than 95%, and the formed alloy can directly meet the industrial needs. SLM technology is suitable for the preparation of difficult-to-machine, high-performance refractory metals and alloys.

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

Pre-alloyed NbSi super high temperature alloy powder prepared by argon atomization method, the NbSi powder is spherical or nearly spherical, and the diameter is between 10 and 60 μm. Then, the Nb-Si alloy powder was prepared by rapid prototyping by selective laser melting (SLM) process. Set reasonable laser forming parameters (laser power, laser beam scanning speed, scanning distance and powder coating thickness), and use high-energy laser beam to melt NbSi alloy powder. In addition, in the selective laser melting process, the powder melts/solidifies extremely fast and the cooling rate is extremely high (10 ⁵ ~ 10 ⁶ K/s), so a fine, uniform and stable rapid solidification alloy structure can be prepared to obtain mechanical properties Excellent NbSi superalloy parts.

The present invention utilizes SLM technology to prepare the method for NbSi super high temperature alloy, and the preparation process specifically comprises the following steps:

(1) Use the computer to design the 3D CAD model of the part, and use the slicing software to discretize the model in the height direction. Processing path, save multi-layer slicing information as an STL file, and transmit it to the SLM laser melting system;

(2) Fix the forming substrate on the liftable workbench, vacuumize the sealing device and fill it with high-purity argon (99.99%) for atmosphere protection. The powder feeding system evenly spreads a layer with a thickness of 0.03-0.1mm on the substrate NbSi ultra-high temperature alloy powder to be processed;

(3) The laser 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; specific preparation parameters: laser power 350-500W, scanning speed 200-400mm /s, scanning distance 0.05～0.15mm;

(4) After completing a layer scan, the substrate is lowered by a layer thickness, and a layer of NbSi alloy powder with a thickness of 0.03-0.1mm is evenly spread on the first cladding layer;

(5) Repeat the above steps (3)-(4) until the processing of the NbSi-based ultra-high temperature alloy is completed;

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

In the present invention, the combination of argon atomization powder preparation and SLM process is used to prepare NbSi super high temperature alloy. The interaction between powder and laser beam is different from other traditional powder metallurgy processes, and its melting/solidification behavior is different from traditional methods. The main advantages of this technical solution are:

(1) SLM technology uses laser beams to deposit NbSi ultra-high temperature alloy powder layer by layer, and directly completes the preparation of NbSi alloy in one step from the CAD model. The preparation process does not need to prepare crucibles, molds or powder jackets, etc., reducing dimensional errors; SLM technology can effectively avoid interface reactions between superalloys and crucibles, molds, etc., reduce alloy pollution, and reduce inclusion content; the SLM process is protected by argon atmosphere, It has a protective effect on the NbSi alloy in high temperature state, effectively avoids the oxidation of the alloy, and improves the comprehensive performance of the alloy.

(2) During the preparation of ultra-high temperature NbSi alloys by SLM technology, when the powder is melted, the temperature of the liquid phase molten pool is extremely high, the size is small, and the solidification time is extremely short, so the cooling rate is extremely high (10 ⁵ ~ 10 ⁶ K/s), which is High non-equilibrium solidification, extremely short solidification time, can effectively reduce the micro-segregation of NbSi ultra-high temperature alloy, and the alloy density is higher than the traditional powder metallurgy process, with a small, uniform and stable rapid solidification structure, so as to obtain excellent mechanical properties NbSi ultra-high temperature alloy parts;

(3) SLM is suitable for the preparation of 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 avoids traditional machining and post-processing, saving manpower and material resources; at the same time, unprocessed and redundant NbSi pre-alloyed powders can be recycled and reused, and the material utilization rate is high;

(4) The NbSi ultra-high temperature alloy formed by SLM technology has high density. The alloy is mainly composed of Nbss solid solution and Nb ₅ Si ₃ strengthening phase, which is evenly distributed, and the phase size is extremely small (less than 1 μm), reaching the nanometer scale, which is much smaller than the traditional method Prepare the phase size. The microstructure characteristics obtained by SLM can improve the comprehensive mechanical properties of NbSi alloy.

Description of drawings:

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

Accompanying drawing 2 is the SEM image of Nb-18Si-24Ti-2Cr-2Al-2Hf alloy formed by SLM technology;

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

Accompanying drawing 4 SLM technology forming Nb-16Si-22Ti-4Cr-2Al-2Hf alloy scanning electron microscope pictures.

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

Using SLM technology to prepare Nb-18Si-24Ti-2Cr-2Al-2Hf (at.%, atomic percentage) super high temperature alloy: the SLM laser selective melting system used mainly includes: Nd-YAG laser, computer system for forming control, Powder feeding system and argon atmosphere protection device;

1. Select 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 10 and 60 μm;

2. According to the shape of the alloy parts to be processed, use the computer to establish a three-dimensional CAD model, and use the slicing software to perform layered slice discretization in the height direction of the model. Section profile information and scanning processing path, save multi-layer slice information as STL file, and transfer to SLM laser melting system;

3. Put the powder into the forming cavity, and fix the Ti6Al4V forming substrate with a thickness of 10mm on the liftable workbench; the sealed forming cavity is first evacuated, and then flushed with high-purity argon (99.99%) for protection. Use the powder feeding system to evenly spread a layer of Nb-18Si-24Ti-2Cr-2Al-2Hf ultra-high temperature alloy powder with a thickness of 0.05mm on the substrate;

4. The laser beam scans the preset powder on the substrate according to the preset scanning path and preparation parameters, and the powder melts and solidifies to form a cladding layer; specific preparation parameters: laser power 400W, scanning speed 250mm/ s, scanning distance 0.10mm;

5. After completing a layer scan, the substrate is lowered by a layer thickness, and a layer of Nb-18Si-24Ti-2Cr-2Al-2Hf alloy powder with a thickness of 0.05mm is evenly spread on the first cladding layer;

6. Repeat the above steps (5) and (6) until the Nb-18Si-24Ti-2Cr-2Al-2Hf ultra-high temperature alloy parts are processed, then shut down the system, and take them out when the parts are cooled to room temperature; the whole preparation process is carried out under argon Carried out in a protective atmosphere;

It can be seen from Figure 1 that the structure of the Nb-18Si-24Ti-2Cr-2Al-2Hf alloy formed by SLM is mainly composed of Nb _SS solid solution and Nb ₅ Si ₃ phases. The light phase is Nbss solid solution, and the dark phase is Nb ₅ Si ₃ phase.

It can be seen from Figure 2 that the SLM formed Nb-18Si-24Ti-2Cr-2Al-2Hf alloy has high density and no cracks. The size of Nbss phase and Nb ₅ Si ₃ phase is extremely small (<1 μm), reaching the level of nano phase, and the two phases are evenly distributed, showing obvious characteristics of rapid solidification structure, which can improve the comprehensive performance of NbSi super high temperature alloy.

Example 2

Using SLM technology to prepare Nb-16Si-22Ti-4Cr-2Al-2Hf (at.%, atomic percentage) super high temperature alloy: the SLM laser selective melting system used mainly includes: Nd-YAG laser, computer system for forming control, Powder feeding system and argon atmosphere protection device;

1. Select 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 10 and 60 μm;

2. According to the shape of the alloy parts to be processed, use the computer to establish a three-dimensional CAD model, and use the slicing software to perform layered slice discretization in the height direction of the model. Section profile information and scanning processing path, save multi-layer slice information as STL file, and transfer to SLM laser melting system;

3. Put the powder into the forming cavity, and fix the Ti6Al4V forming substrate with a thickness of 10mm on the liftable workbench. The sealed forming cavity is first evacuated, and then flushed with high-purity argon (99.99%) for protection. Use the powder feeding system to evenly spread a layer of Nb-16Si-22Ti-4Cr-2Al-2Hf ultra-high temperature alloy powder with a thickness of 0.08mm on the substrate;

4. The laser beam scans the preset powder on the substrate according to the preset scanning path and preparation parameters, and the powder melts and solidifies to form a cladding layer; specific preparation parameters: laser power 400W, scanning speed 300mm/ s, scanning distance 0.06mm;

5. After completing a layer scan, the substrate is lowered by a layer thickness, and a layer of Nb-16Si-22Ti-4Cr-2Al-2Hf alloy powder with a thickness of 0.08mm is evenly spread on the first cladding layer;

6. Repeat the above steps (5) and (6) until the Nb-16Si-22Ti-4Cr-2Al-2Hf ultra-high temperature alloy parts are processed, then shut down the system and take them out when the parts are cooled to room temperature; the whole preparation process is carried out under argon Carried out in a protective atmosphere;

It can be seen from Figure 3 and Figure 4 that the SLM formed Nb-16Si-22Ti-4Cr-2Al-2Hf alloy has high density, a small amount of pores (size <1μm), and no defects such as voids and hot cracks. The formed alloy is composed of nanoscale Nb _ss phase and Nb ₅ Si ₃ phase (the light-colored phase is Nbss solid solution, and the dark-colored phase is Nb ₅ Si ₃ phase), the size is extremely small (<1 μm), and the two phases are evenly distributed, showing obvious The characteristics of rapid solidification structure can improve the comprehensive performance of NbSi super 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 (8)

1. one kind utilizes the method that selective laser smelting technology prepares NbSi supertherm, it is characterised in that preparation process bag Include following steps:

(1). according to NbSi supertherm drip molding shape to be processed, set up drip molding cad model, then in short transverse On to its carry out hierarchy slicing process to be divided into section in uniform thickness, section comprise Alloy Forming part cross-sectional profiles letter Breath and machining path, and section file is imported in the melting unit of selective laser, described slice thickness is 0.03～0.1mm；

(2). in the melting unit of selective laser, Ti6Al4V forming board is fixed on liftable workbench, sealing device Being filled with protective gas after evacuation and carry out atmosphere protection, powder feed system uniform spreading one layer NbSi superhigh temperature to be processed on substrate is closed Bronze end, powder thickness is equal with slice thickness in step (1), and selected NbSi supertherm powder is by Powder In Argon Atomization It is prepared, spherical in shape or subsphaeroidal, diameter 10～60 μm；

(3). the NbSi supertherm powder on substrate, according to scanning pattern set in advance, is optionally carried out by laser beam Scanning, powder smelting also solidifies, and forms cladding layer；

(4). completing in step (3) after a plane scan, substrate declines the distance of a thickness, and is formed in step (3) Cladding layer on uniform spreading last layer NbSi supertherm powder again；

(5). repeat the above steps (3)-(4), until NbSi supertherm part machines；It is then shut off system, treats parts It is cooled to during room temperature take out；Whole preparation process is carried out in protective atmosphere.

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its Being characterised by, the protective gas described in step (2) is high-purity argon gas, and purity is 99.99%.

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its It is characterised by, in step (3), forms cladding layer；Concrete preparation parameter: laser power 350～500W, scanning speed 200 ～400mm/s, sweep span 0.05～0.15mm.

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its Being characterised by, in step (4), then the NbSi supertherm powder thickness uniformly laid is 0.03～0.1mm.

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its Being characterised by, described Ti6Al4V forming board thickness is 10mm.

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its Being characterised by, described NbSi supertherm powdered ingredients is calculated as Nb-18Si-24Ti-2Cr-2Al-with atomic percent 2Hf。

A kind of method utilizing selective laser smelting technology to prepare NbSi supertherm the most according to claim 1, its Being characterised by, described NbSi supertherm powdered ingredients is calculated as Nb-16Si-22Ti-4Cr-2Al-with atomic percent 2Hf。

8. prepare the side of NbSi supertherm according to the selective laser smelting technology that utilizes described in any one of claim 1-7 Method, it is characterised in that it is high to be cooled to the NbSi supertherm consistency that room temperature obtains, Main Tissues by Nbss solid solution and Nb5Si3 hardening constituent forms, phase size < 1 μm and being evenly distributed.