Method for preparing submicron / micron particle reinforced refractory alloy by means of electron beam selective melting forming

Abstract

A method for preparing a submicron / micron particle reinforced refractory alloy by means of electron beam selective melting forming, comprising the following steps: uniformly mixing refractory alloy powder and Si powder, and preparing a submicron / micron particle reinforced refractory alloy by means of an electron beam selective melting forming method. The particle size of the refractory alloy powder is 30-80 μm, and the particle size of the Si powder is 10-25 μm.

Description

A method for preparing submicron / micron particle reinforced refractory alloy by electron beam selective melting

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 6, 2023, with application number 2023116678841 and invention name “A method for preparing submicron / micron particle reinforced refractory alloys by electron beam selective melting forming”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The invention belongs to the technical field of in-situ forming of refractory alloy composite materials, and in particular relates to a method for preparing submicron / micron particle reinforced refractory alloys by electron beam selective melting. Background Art

[0003] Compared with single-phase refractory alloys, particle reinforcement can effectively improve the room temperature and high temperature strength of refractory metal matrix composites, but it also leads to a significant decrease in plasticity. The contradiction between strength and plasticity has always been an unsolvable problem in this field, which seriously restricts the application of refractory alloys in aviation, aerospace and other fields. Research results in recent years have shown that with the reduction of the size of the reinforcement phase, the comprehensive mechanical properties such as strength and plasticity of particle reinforced composites show a better balance. At present, relevant research has been carried out on particle reinforced Al, Mg, Fe and other metal matrix composites and their preparation technology at home and abroad, and good results have been achieved. In addition, Nb5Si3 / Nb composed of Nb5Si3 reinforcement phase and Nb solid solution SS The dual-phase composite material exhibits excellent high-temperature mechanical properties, with a tensile strength of 370 MPa at 1200°C, twice that of the second-generation Ni-based single crystal alloy. By regulating the microstructure, its fracture toughness can be increased to 18 MPa·m 1 / 2 The above are the current hot topics in the development of a new generation of ultra-high temperature structural materials with a target temperature range of 1200-1300°C. It can be speculated that the formation of dispersed small-sized reinforcing particles in the refractory alloy matrix is ​​expected to significantly improve the strength-toughness balance of refractory alloys.

[0004] However, refractory metal composites are generally used in high-temperature working environments, and the reinforcing phase in them must also have a high melting point to ensure the high-temperature mechanical properties of the material. Selecting the right second-phase particles so that they can bond well with the refractory alloy matrix interface and achieve uniform dispersion is the key to obtaining refractory alloy composites with good performance matching. In addition, due to the high melting point of refractory alloys themselves, traditional techniques such as melting and casting are difficult to prepare, and are prone to problems such as coarse structure and element segregation. In particular, when the particle reinforcement phase size reaches tens of microns, these reinforcement phases can easily become crack initiation sites, seriously affecting the mechanical properties of the alloy.

[0005] It can be seen that selecting suitable reinforcement phase particles and making the reinforcement phase present a fine and dispersed distribution through appropriate processes are key issues that need to be urgently solved for high-performance refractory alloy composites with a working temperature target of 1200-1300℃. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing submicron / micron particle reinforced refractory alloys by electron beam selective melting. The method of the present invention can effectively improve the high-temperature mechanical properties of refractory alloy materials and avoid cracking of refractory alloys with low plasticity due to thermal stress during the forming process.

[0007] The present invention provides a method for preparing a submicron / micron particle reinforced refractory alloy by electron beam selective melting, comprising the following steps:

[0008] The refractory alloy powder and Si powder are uniformly mixed, and a submicron / micron particle reinforced refractory alloy is prepared by electron beam selective melting forming method;

[0009] The particle size of the refractory alloy powder is 30 to 80 μm, and the particle size of the Si powder is 10 to 25 μm.

[0010] Preferably, the refractory alloy powder is an alloy powder composed of one or two or more of W, Ta, Mo, Nb, V, Zr, Hf and Ti.

[0011] Preferably, the refractory alloy powder is spherical powder.

[0012] Preferably, the refractory alloy is a single-phase solid solution alloy powder.

[0013] Preferably, the mass of the Si powder accounts for 1 to 8% of the total mass of the refractory alloy powder and the Si powder.

[0014] Preferably, no other solid substances are added during the mixing process, and after uniform mixing, a nearly spherical composite powder of Si powder coated with refractory alloy powder is obtained.

[0015] Preferably, the mixing time is 1 to 10 hours.

[0016] Preferably, during the electron beam selective melting and forming process, the powder bed is preheated by electron beam scanning, the electron beam power is 300-600W, and the operating voltage is 40-70kV.

[0017] Preferably, the preheating temperature is 800°C to 1000°C, and the vacuum degree is 2×10 -3 ±0.5×10 -4 mbar.

[0018] Preferably, the thickness of each layer of powder is 30 to 80 μm.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) Since refractory metal silicides have excellent high-temperature properties, silicides are selected as the reinforcing phase of refractory alloys. Since refractory metal silicides have extremely high melting points and high-temperature mechanical properties, they can greatly improve the high-temperature mechanical properties of refractory alloy composites.

[0021] (2) Under the action of high-energy electron beams, refractory metal silicides are formed in situ in the matrix of the refractory alloy, effectively avoiding the interface problem between the reinforcement phase and the matrix phase. The interface between the two phases is well bonded, which further ensures the mechanical properties of the refractory alloy composite material.

[0022] (3) The present invention uses Si powder raw materials with a particle size of 10-25 μm and Nb powder raw materials with a particle size of 30-80 μm. Under the action of an electron beam, the refractory alloy and Si react in situ and solidify rapidly to obtain a refractory alloy composite material reinforced with submicron / micron refractory metal silicide particles. Compared to a cast refractory alloy of the same composition, the particle reinforcement phase can be significantly reduced from the size of tens of microns to the submicron / micron level, and the submicron Nb5Si3 reinforcement phase accounts for more than 40% of the total reinforcement phase. This greatly reduces the brittleness of the particle-reinforced refractory alloy and, based on the Orowan strengthening principle, significantly improves the strength of the particle-reinforced refractory alloy. This is a significant technological advancement in this field.

[0023] (4) The use of electron beam selective melting (EBSM) technology can significantly shorten the preparation cycle of refractory alloy composites and has the potential to form complex structures. Using this method, crack-free hollow, thin-walled, complex engine turbine blades were successfully prepared. The blades had good metallurgical quality and no cracks were found.

[0024] (5) Using the above method, we successfully prepared a product with a size greater than 100×50×50mm. 3 The room temperature strength, room temperature fracture toughness and high temperature strength of the alloy are effectively improved compared with the refractory alloy itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0026] FIG1 is a microstructure of a (NbTiZrHf)5Si3 particle reinforced NbTiZrHf refractory alloy in Example 1 of the present invention;

[0027] FIG2 is a simulation of a hollow turbine blade made of a NbTiZrHf refractory alloy reinforced with submicron / micron (NbTiZrHf)5Si3 particles in Example 1 of the present invention;

[0028] FIG3 shows the microstructure of the Nb5Si3 particle reinforced Nb-based refractory alloy in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a submicron / micron particle reinforced refractory alloy by electron beam selective melting, comprising the following steps:

[0030] The refractory alloy powder and Si powder are uniformly mixed, and a submicron / micron particle reinforced refractory alloy is prepared by electron beam selective melting forming method;

[0031] The particle size of the refractory alloy powder is 30 to 80 μm, and the particle size of the Si powder is 10 to 25 μm.

[0032] In the present invention, the refractory alloy powder is an alloy powder composed of one or two or more of W, Ta, Mo, Nb, V, Zr, Hf and Ti; the phase structure of the refractory alloy is a single-phase solid solution, and the refractory alloy powder is preferably a spherical powder, and the particle size is preferably 30 to 80 μm, more preferably 40 to 70 μm, such as 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, preferably a range value with any of the above values ​​as the upper or lower limit.

[0033] In the present invention, the Si powder is spherical or irregularly shaped, and the particle size of the Si powder is preferably 10 to 25 μm, more preferably 15 to 20 μm.

[0034] In the present invention, the mass of the Si powder preferably accounts for 1 to 8% of the total mass of the refractory alloy powder and the Si powder, more preferably 2 to 7%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0035] In the present invention, spherical refractory alloy powder and Si powder are mechanically mixed, and no other solid objects (such as grinding balls, etc.) are added during the mixing process, so as to maintain the particle size range of the two powders and form a nearly spherical composite powder of small-sized Si powder coated refractory alloy powder.

[0036] In the present invention, the mixing time is preferably 1 to 10 hours, more preferably 3 to 8 hours, and most preferably 5 to 6 hours.

[0037] After the composite powder is obtained, the composite powder of the present invention is used as raw material powder for electron beam selective melting and forming, and is loaded into a powder cylinder of the electron beam selective melting and forming equipment.

[0038] Then, a three-dimensional CAD model of the refractory alloy blade to be prepared is established, and it is sliced ​​in layers in the height direction. The scanning path is filled for each slice layer, and then the slice information and scanning path information are imported into the electron beam selective melting forming system.

[0039] During the forming process, electron beam scanning is used to preheat the powder bed. The nearly spherical composite powder of refractory alloy + Si is rapidly melted under the action of the electron beam, and an in-situ reaction occurs between the Si element and part of the refractory alloy to form fine refractory metal silicides. At the same time, some refractory alloy that has not been completely reacted is retained, ultimately forming submicron / micron particle reinforced refractory alloy materials or refractory alloy parts with complex structures.

[0040] In the present invention, the preheating temperature is preferably 800-1000°C, more preferably 850-950°C, such as 800°C, 850°C, 900°C, 950°C, 1000°C, preferably with any of the above values ​​as the upper or lower limit; the vacuum degree during the forming process is preferably maintained at 2×10 -3 ±0.5×10 -4 mbar, more preferably 2×10 -3 ±0.4×10 -4 mbar, most preferably 2×10 -3 ±0.3×10 -4 mbar; the working voltage is preferably 40-70kV, more preferably 50-60kV, such as 40kV, 45kV, 50kV, 55kV, 60kV, 65kV, 70kV, preferably a range value with any of the above values ​​as the upper or lower limit; the electron beam power is preferably set to 300-600W, more preferably 400-500W, such as 300W, 350W, 400W, 450W, 500W, 550W, 600W, preferably a range value with any of the above values ​​as the upper or lower limit; the thickness of each layer of powder is preferably 30-80μm, more preferably 40-70μm.

[0041] The present invention provides a method for preparing submicron / micron particle-reinforced refractory alloys by electron beam selective melting. The method comprises the following steps: uniformly mixing refractory alloy powder with Si powder, and preparing the submicron / micron particle-reinforced refractory alloy by electron beam selective melting. The refractory alloy powder has a particle size of 30 to 80 μm, and the Si powder has a particle size of 10 to 25 μm. The present invention also provides a method for mechanically mixing large-particle refractory alloy powder (30 to 80 μm) with Si powder (10 to 25 μm) to obtain a nearly spherical composite powder of refractory alloy and Si. This composite powder serves as the raw material for electron beam selective melting. Under the action of a high-energy electron beam, the Si powder in the composite powder reacts in situ with the refractory alloy powder, forming submicron / micron-sized silicides in situ on the refractory alloy matrix. Rapid electron beam scanning is used to achieve preheating during the forming process, preventing cracking of the refractory alloy, which has low plasticity, due to thermal stress during the forming process.

[0042] To further illustrate the present invention, a method for preparing submicron / micron particle reinforced refractory alloys by electron beam selective melting provided by the present invention is described in detail below in conjunction with examples, but it should not be understood as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] A method for preparing submicron / micron (NbTiZrHf)5Si3 particle-reinforced NbTiZrHf refractory alloy hollow turbine blades by electron beam selective melting is completed in the following seven steps:

[0045] (1) NbTiZrHf refractory alloy powder was prepared by melt casting + plasma rotating electrode method, and TiZrHfNb refractory alloy spherical powder with a size of about 30-80 μm was obtained by screening.

[0046] (2) Weigh 50,000 g of TiZrHfNb refractory alloy powder with a particle size of 30-80 μm and Si powder with a particle size of 10-25 μm at a mass ratio of approximately 96:4. Generally, the amount of Si added is calculated based on the Si content required to fully consume the Nb5Si3 reinforcement phase.

[0047] (3) Put 50000g of mixed powder into the mixer without adding grinding balls and mix for a total of 1-7 hours

[0048] (4) The mixed powder is used as raw material powder for electron beam selective melting and forming, and the mixed powder is loaded into a powder cylinder of an electron beam selective melting and forming device.

[0049] (5) Set the electron beam preheating temperature selection zone melting forming powder bed preheating temperature to 900±50℃.

[0050] (6) A 3D CAD model of the refractory alloy blade to be prepared is established, and then it is sliced ​​in layers in the height direction, and the scanning path is filled for each slice. The slice information and scanning path information are then imported into the electron beam selective melting forming system. The forming vacuum is maintained at 2×10 -3 ±0.5×10 -4 mbar, the operating voltage is 60kV, the electron beam power is set to 500W, and the thickness of each powder layer is 50μm.

[0051] (7) The electron beam selective melting forming system begins forming. First, the powder bed is preheated using a defocused electron beam to slightly consolidate the alloy powder. Each layer of powder is then heated, melted, and solidified according to a computer-generated path. The powder is then accumulated layer by layer until the blade is completed.

[0052] The effect achieved by this embodiment is as follows: the microstructure of the refractory alloy prepared by this method is shown in Figure 1. The white phase in Figure 1 is the TiZrHfNb solid solution phase, and the black phase in Figure 1 is the (NbTiZrHf)5Si3 refractory metal silicide phase. In the alloy microstructure, the vast majority of the (NbTiZrHf)5Si3 phase size is ≤1 micron, resulting in a submicron / micron particle-reinforced refractory alloy. Compared with the traditional melting and casting preparation process, this alloy effectively reduces the brittleness of the alloy while improving the strength and toughness of the alloy. Figure 2 shows a prepared micron / micron (NbTiZrHf)5Si3 particle-reinforced NbTiZrHf refractory alloy hollow turbine blade simulation part, which has dimensions of approximately 100 mm (length) × 20 mm (width) × 80 mm (height). No macro cracks were observed, further demonstrating the ability of the present invention in complex structure forming and manufacturing.

[0053] Example 2

[0054] A method for preparing submicron / micron Nb5Si3 particle-reinforced Nb-based refractory alloy by electron beam selective melting is completed in the following six steps:

[0055] (1) Pure Nb refractory alloy powder with a particle size of 30-80 μm and Si powder with a particle size of 10-25 μm were weighed in a mass ratio of approximately 95:5, for a total of 10,000 g.

[0056] (2) 10,000 g of mixed powder was placed in a powder mixer and mixed for 3-5 hours.

[0057] (3) The mixed powder is loaded into the powder cylinder of the electron beam selective melting forming equipment.

[0058] (4) Set the electron beam preheating temperature to select the zone for melting and forming the powder bed preheating temperature to 1000±50℃.

[0059] (5) The size is 100×50×50mm 3 A 3D CAD model of a rectangular refractory alloy specimen to be fabricated was prepared. The model was then sliced ​​at a height of 50 mm. The scanning path for each slice was filled. The slice and scanning path information was then imported into the electron beam selective melting (EBM) system. The operating voltage was 60 kV, the electron beam power was set to 550 W, and the powder thickness per layer was 60 μm.

[0060] (6) The electron beam selective melting forming system begins to form. First, the powder bed is preheated using a defocused electron beam to slightly consolidate the alloy powder. Then, each layer of powder is heated, melted, and solidified according to the path generated by the computer. Finally, it is accumulated layer by layer until it reaches 100×50×50mm. 3 The rectangular test block is prepared.

[0061] The effect obtained by this embodiment is: the microstructure of the Nb-Si binary alloy obtained by the present invention is shown in Figure 3, where the white phase in Figure 3 is the Nb-based solid solution phase, and the black phase in Figure 3 is the Nb5Si3 silicide phase. The Nb5Si3 silicide phase presents a submicron or micron scale, which can effectively reduce the brittleness of the Nb-Si binary alloy while maintaining its high-temperature strength.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a submicron / micron particle reinforced refractory alloy by electron beam selective melting, comprising the following steps: The refractory alloy powder and Si powder are uniformly mixed, and a submicron / micron particle reinforced refractory alloy is prepared by an electron beam selective melting forming method; The particle size of the refractory alloy powder is 30-80 μm, and the particle size of the Si powder is 10-25 μm.

2. The method according to claim 1, characterized in that The refractory alloy powder is an alloy powder composed of one or two or more of W, Ta, Mo, Nb, V, Zr, Hf and Ti.

3. The method according to claim 2, characterized in that The refractory alloy powder is spherical powder.

4. The method according to claim 1, characterized in that: The refractory alloy is a single-phase solid solution alloy powder.

5. The method according to claim 1, characterized in that The mass of the Si powder accounts for 1 to 8% of the total mass of the refractory alloy powder and the Si powder.

6. The method according to claim 1, characterized in that No other solid matter is added during the mixing process, and after uniform mixing, a nearly spherical composite powder of Si powder coated with refractory alloy powder is obtained.

7. The method according to claim 1, characterized in that The mixing time is 1 to 10 hours.

8. The method according to claim 1, characterized in that During the electron beam selective melting forming process, the powder bed is preheated by electron beam scanning, the electron beam power is 300-600W, and the working voltage is 40-70kV.

9. The method according to claim 8, characterized in that The preheating temperature is 800°C to 1000°C, and the vacuum degree is 2×10 -3 ±0.5×10 -4 mbar.

10. The method according to claim 9, characterized in that The thickness of each powder layer is 30 to 80 μm.

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