Preparation method of niobium-silicon alloy with surface multi-gradient eutectic structure and high toughness and oxidation resistance

Abstract

The invention discloses a preparation method of a niobium-silicon alloy with a surface multi-gradient eutectic structure and high toughness and oxidation resistance, and relates to post-treatment preparation of a high-melting-point active alloy material. The problem that the room-temperature fracture toughness and the high-temperature oxidation resistance of an existing niobium-silicon alloy cannot be considered at the same time is solved. The method comprises the following steps: 1, weighing a niobium-silicon alloy raw material; 2, vacuum non-self-consumption smelting ingot casting is carried out; thirdly, the cast ingot in the second step is cut into a metal plate through linear cutting, and the metal plate is obtained through cleaning and polishing; fourthly, the metal plate is subjected to laser remelting treatment, and a sub-nanometer eutectic structure layer is obtained; fifthly, abrasive paper is adopted for polishing treatment; sixthly, the metal plate in the fifth step is subjected to shot blasting treatment, and a nanometer ultra-fine grain structure with the thickness being 10-40 microns is obtained; and step 7, ultrasonically cleaning and drying the obtained metal plate, namely the niobium-silicon alloy with the multi-gradient eutectic size on the surface and high toughness and oxidation resistance. The method is used for post-treatment preparation of the high-melting-point active alloy material.

Description

Technical Field

[0001] The invention relates to a method for preparing a surface-strengthened niobium-silicon alloy, and in particular to a method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure and high toughness and oxidation resistance, belonging to the technical field of post-processing preparation of high-melting-point active alloy materials. Background Art

[0002] Aircraft engines are known as "the jewel in the crown of the industry" and are developing towards higher temperatures and greater thrust. The future fifth-generation aircraft engines will require a thrust-to-weight ratio of more than 15, and the service temperature of high-pressure turbine blade materials will reach 1250-1400°C, which puts higher requirements on the blade materials of aircraft engines.

[0003] At present, the service temperature of high-pressure turbine blades made of Ni-based single crystal alloys is 1100-1150℃, which is about 85% of the melting point of Ni-based single crystals. It is difficult to achieve a significant breakthrough in reaching its maximum operating temperature, and it cannot meet the demand for high thrust-to-weight ratio of future aviation engines.

[0004] The melting point of niobium silicon alloy exceeds 1900℃, and the potential service temperature exceeds 1300℃. It is an important potential application material for the high-pressure turbine blades of the new generation of aircraft engines. Niobium silicon alloy is mainly composed of tough niobium silicon solid solution phase and brittle silicide phase. Large-sized silicide phase will significantly deteriorate room temperature fracture toughness and oxidation resistance due to its intrinsic brittleness. Therefore, regulating the size and content of silicide phase is a favorable way to improve the room temperature toughness and high temperature oxidation performance of niobium silicon alloy.

[0005] Laser remelting of niobium silicon alloy can refine the coarse silicide phase, but the remelted niobium silicon alloy structure will produce cracks due to the large internal stress, which will eventually lead to the failure of the ingot structure, thereby greatly deteriorating the room temperature toughness and high temperature oxidation resistance. Therefore, it is necessary to explore a preparation method that has a multi-gradient eutectic size on the surface and inhibits remelting cracks to improve its toughness and oxidation resistance, so as to quickly put niobium silicon alloy into application.

[0006] In summary, the existing niobium silicon alloy has a coarse silicide phase structure, which deteriorates the room temperature toughness and high temperature oxidation resistance. Summary of the invention

[0007] The purpose of the present invention is to solve the problem that the existing niobium silicon alloy has a coarse silicide phase structure, which deteriorates the room temperature toughness and high temperature oxidation resistance, and further provide a method for preparing a niobium silicon alloy with a surface multi-gradient eutectic structure that combines high strength and toughness with oxidation resistance.

[0008] The technical solution of the present invention is: a method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance comprises the following steps:

[0009] Step 1: Weigh the niobium silicon alloy raw materials;

[0010] Step 2: Vacuum non-consumable melting ingot;

[0011] Step 3: Cut the ingot in step 2 into metal plates by wire cutting, clean and polish them to obtain metal plates with no processing marks and clean surfaces;

[0012] Step 4: laser remelting the metal plate to obtain a 200-400 μm thick sub-nanometer eutectic structure layer;

[0013] Step 5: Polish the remelted metal plate in step 4 with sandpaper;

[0014] Step 6: Shot peening the metal plate in step 5 to obtain a nano-ultrafine grain structure with a thickness of 10-40 μm;

[0015] Step 7: Ultrasonic cleaning and drying of the obtained metal plate, i.e., the niobium silicon alloy with multi-gradient eutectic size on the surface taking into account high strength, toughness and oxidation resistance.

[0016] Furthermore, the niobium silicon alloy raw materials in step 1 are weighed in the ratio of 16% Si, 30% Ti, x% Sm and 54-x% Nb in atomic percentage, and the total atomic percentage is 100%.

[0017] Preferably, in step 1, the percentage content of x% Sm in the niobium silicon alloy raw material is 0.1 or 0.2 or 0.5.

[0018] Furthermore, the vacuum non-consumable melting ingot in step 2 includes the following steps:

[0019] Step 21: Put the weighed single element into a vacuum non-consumable water-cooled copper crucible according to the principle that the single element with high melting point is on the top and the single element with low melting point is on the bottom;

[0020] Step 22: Use the mechanical pump and vacuum pump to pump the pressure of the vacuum melting chamber to 2×10 -3 Pa, flush with protective argon gas to 400Pa-600Pa;

[0021] Step 2 and 3: Carry out tungsten electrode non-consumable smelting with a smelting current of 500A-700A to obtain niobium silicon ingots.

[0022] Furthermore, the laser remelting of the metal plate in step 4 includes the following steps:

[0023] Step 41: Fix the metal plate obtained in step 3 on the laser beam platform and evacuate to 2×10 -3 Pa, flush with protective argon gas to 300Pa;

[0024] Step 42: Use a 40mA laser beam to perform a single pass zigzag remelting on the surface of the metal plate;

[0025] Step 43: The platform movement rate during the remelting process is 200mm / min-400mm / min, and the final cooling is used to obtain the preparation of the laser beam remelted metal sheet.

[0026] Furthermore, the parameters for shot peening the metal plate in step six are: using ceramic shots with a diameter of 0.2 mm, a ceramic shot flow rate of 6-8 kg / min, a compressed gas pressure of 0.5 MPa, and a shot peening time of 40-60 min, and finally obtaining a 10-40 μm thick nano-ultrafine grained niobium silicon plate after shot peening.

[0027] Preferably, the ingot in step 2 is smelted repeatedly 8 times.

[0028] Preferably, in step three, the metal plate is cleaned by ultrasonic cleaning and acetone cleaning.

[0029] Preferably, the platform movement rate during the remelting process in step 43 is: 300 mm / min or 400 mm / min.

[0030] Preferably, the shot peening time in step six is ​​50-60 minutes.

[0031] Compared with the prior art, the present invention has the following effects:

[0032] 1. The present invention adopts reasonable alloy composition. The Si content is 16%, which is a near-eutectic composition point, ensuring that there are no large-sized primary silicide phases and niobium-based solid solution phases in the structure. The Ti content is 30%, which improves the room temperature toughness. The high content of Ti increases the toughness of the niobium-based solid solution. The rare earth element Sm refines the eutectic structure and reduces the oxygen content of the grain boundary, thereby improving the toughness and high-temperature oxidation resistance of the matrix alloy. A eutectic niobium-silicon alloy with a finer structure was prepared. After 0.2Sm element doping, the size of the eutectic group was reduced by 50%, and the toughness of the cast alloy itself reached 9.4Mpa·m 1 / 2 , 1200℃ / 50h oxidation performance is 239.4mg / cm 3 , the overall performance is good, and the silicide phase in the multi-gradient eutectic structure is further produced by laser remelting and shot peening.

[0033] 2. The present invention uses the compressive stress generated by the ceramic shot with a diameter of 0.2 mm and the shot peening for 40-60 minutes to offset the internal stress generated by remelting, thereby avoiding the crack problem caused by the excessive cooling rate of remelting. Finally, the gradient eutectic structure greatly improves the room temperature toughness and high temperature oxidation resistance of the niobium silicon alloy. The fuel injector and other hot end components of the aircraft engine can be prepared later. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a microstructure diagram of the Nb-16Si-30Ti-0.5Sm alloy in Example 1 of the present invention, in which the shot peening time is 50 minutes and the moving speed of the niobium silicon metal plate is 300 mm / min.

[0035] Figure 2 It is a schematic diagram of the comparison of the room temperature fracture toughness values ​​of the multi-gradient Nb-Si alloy in Example 1 of the present invention.

[0036] Figure 3 It is a schematic diagram comparing the high temperature oxidation resistance of the multi-gradient Nb-Si alloy in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] Specific implementation method 1: A method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance in this implementation method comprises the following steps:

[0038] Step 1: Weigh the niobium silicon alloy raw materials;

[0039] Step 2: Vacuum non-consumable melting ingot;

[0040] Step 3: Cut the ingot in step 2 into metal plates by wire cutting, clean and polish, and obtain metal plates with no processing marks and clean surface;

[0041] Step 4: laser remelting the metal plate to obtain a 200-400 μm thick sub-nanometer eutectic structure layer;

[0042] Step 5: Polish the remelted metal plate in step 4 with sandpaper;

[0043] Step 6: Shot peening the metal plate in step 5 to obtain a nano-ultrafine grain structure with a thickness of 10-40 μm;

[0044] Step 7: Ultrasonic cleaning and drying of the obtained metal plate, i.e., the niobium silicon alloy with multi-gradient eutectic size on the surface taking into account high strength, toughness and oxidation resistance.

[0045] The Nb-Si alloy prepared by this embodiment is expressed as Nb-16Si-30Ti-0.1Sm, Nb-16Si-30Ti-0.2Sm or Nb-16Si-30Ti-0.5Sm.

[0046] In step 3 of this embodiment, the metal plate is firstly polished with sandpaper to remove the wire cutting marks, and then cleaned with alcohol, which can facilitate the removal of the processing marks in the wire cutting process and ensure a clean and smooth surface.

[0047] Specific implementation method 2: In step 1 of this implementation method, the niobium silicon alloy raw materials are weighed according to the atomic percentage ratio of 16% Si, 30% Ti, x% Sm and 54-x% Nb, and the total atomic percentage is 100%.

[0048] The purity of the single substance Nb in step 1 of this embodiment is >99.5wt.% The purity of cylindrical silicon wafers is >99.8wt.%, the purity of granular sponge titanium is >99wt.%, and the purity of elemental filamentous Sm is >99wt.%.

[0049] The raw material single substance in step 1 is subjected to ultrasonic treatment and drying treatment in sequence. The alcohol content of the ultrasonic treatment is 90%, and the drying treatment uses a drying oven to remove the alcohol attached during the ultrasonic treatment.

[0050] The other components and implementation methods are the same as those of the first specific implementation method.

[0051] Specific implementation method three: In step 1 of this implementation method, the percentage content of x% Sm in the niobium silicon alloy raw material is 0.1 or 0.2 or 0.5.

[0052] In this configuration, if the Sm content is too low, the effect is small, and if the content is higher than 0.5%, the refinement effect becomes very weak and unnecessary. The other components and connection relationships are the same as those in the first or second embodiment.

[0053] Specific embodiment 4: In step 2 of this embodiment, the vacuum non-consumable melting ingot includes the following steps:

[0054] Step 21: Put the weighed single element into a vacuum non-consumable water-cooled copper crucible according to the principle that the single element with high melting point is on the top and the single element with low melting point is on the bottom;

[0055] Step 22: Use the mechanical pump and vacuum pump to pump the pressure of the vacuum melting chamber to 2×10 -3 Pa, flush with protective argon gas to 400Pa-600Pa;

[0056] Step 2 and 3: Carry out tungsten electrode non-consumable smelting with a smelting current of 500A-700A to obtain niobium silicon ingots.

[0057] In step 2 of this embodiment, the argon filling value is preferably 600 Pa. Other components and connection relationships are the same as any one of the specific embodiments 1 to 3.

[0058] Specific implementation method 5: In step 4 of this implementation method, laser remelting of the metal plate includes the following steps:

[0059] Step 41: Fix the metal plate obtained in step 3 on the laser beam platform and evacuate to 2×10 -3 Pa, flush with protective argon gas to 300Pa;

[0060] Step 42: Use a 40mA laser beam to perform a single pass zigzag remelting on the surface of the metal plate;

[0061] Step 43: The platform movement rate during the remelting process is 200mm / min-400mm / min, and the final cooling is used to obtain the preparation of the laser beam remelted metal sheet.

[0062] With such arrangement, the zigzag remelting will not have a sudden change, thus ensuring the structural stability of the surface remelting layer. The other components and connection relationships are the same as any one of the specific implementation modes 1 to 4.

[0063] Specific implementation method 6: In step 6 of this implementation method, the parameters for shot peening the metal plate are:

[0064] Ceramic shot with a diameter of 0.2 mm, a ceramic shot flow rate of 6-8 Kg / min, a compressed gas pressure of 0.5 MPa, and a shot peening time of 40-60 min are used to finally obtain a 10-40 μm thick nano-ultrafine grain niobium silicon plate after shot peening.

[0065] In this way, a gradient eutectic niobium-silicon structure can be obtained, which takes into account both room temperature fracture toughness and high temperature oxidation resistance. Other components and connection relationships are the same as any one of the specific embodiments 1 to 5.

[0066] Specific implementation method seven: the ingot in step 2 of this implementation method is repeatedly smelted 8 times.

[0067] Such an arrangement eliminates segregation and ensures organizational stability, and other components and connection relationships are the same as any one of the specific implementation modes one to six.

[0068] Specific implementation method eight: In step three of this implementation method, the metal plate is cleaned by ultrasonic cleaning and acetone cleaning.

[0069] With such arrangement, the cleaning is more thorough and free of impurities. The other components and connection relationships are the same as any one of the specific implementation modes 1 to 7.

[0070] Specific implementation method 9: In step 43 of this implementation method, the platform moving rate during the remelting process is 300 mm / min or 400 mm / min. A gradient eutectic niobium silicon structure can be obtained, taking into account both room temperature fracture toughness and high temperature oxidation resistance.

[0071] Specific embodiment 10: The shot peening time in step 6 of this embodiment is 50-60 minutes. In this way, a gradient eutectic niobium-silicon structure can be obtained, taking into account both room temperature fracture toughness and high temperature oxidation resistance. Other compositions and connection relationships are the same as any one of specific embodiments 1 to 9.

[0072] Combination Figures 1 to 3 Embodiment 1 of the present invention is described:

[0073] A method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure and high strength, toughness and oxidation resistance, comprising the following steps:

[0074] Step 1: Weigh the elemental Si, Ti, Sm and Nb in the ratio of 16% Si, 30% Ti, x% Sm and 54-x% Nb in atomic percentage, the total atomic percentage is 100%, Nb is Cylindrical, 1-3 cm flake, granular sponge titanium and elemental filamentous Sm.

[0075] Step 2: According to the principle that high melting point elements are on the top and low melting point elements are on the bottom, the weighed single element is placed into a vacuum non-consumable water-cooled copper crucible, and an ingot is obtained by vacuum non-consumable smelting.

[0076] The ingot is cut into metal plates by wire cutting, cleaned and polished to obtain metal plates with smooth surface and no processing marks; a 40mA laser beam is used to perform a single-pass zigzag remelting of the metal plate surface, protective argon gas is introduced into the remelting chamber to 400Pa, the platform movement rate is 300mm / min, and finally cooled to obtain the laser beam remelted metal plate.

[0077] The surface of the remelted niobium silicon plate was polished and smoothed, and ceramic shots with a diameter of 0.2 mm, a ceramic shot flow rate of 6-8 kg / min, a compressed gas pressure of 0.5 MPa, and a shot peening time of 50 min were used to finally obtain a surface gradient eutectic niobium silicon plate treated with shot peening.

[0078] Depend on Figure 1 It can be seen that the surface has a multi-gradient eutectic niobium silicon structure. The bottom layer is Nbss / Nb5Si3 eutectic structure, which is larger in size and the silicide exceeds 10μm. There is a eutectic structure of 0.5-5μm in the middle. The eutectic structure is even finer. There are a large number of nano-ultrafine eutectics on the surface. The white niobium-based solid solution phase mostly changes from irregular elliptical to spherical.

[0079] Figure 1 The phase detection results show that the phase composition is composed of Nbss and Nb5Si3 phases.

[0080] Figure 2 It can be seen that the room temperature fracture toughness of the alloy is 20.4MPa·m 1 / 2 .

[0081] Figure 3 It can be seen that the oxidation weight gain of the alloy at 1200℃ / 50h is only 51.5mg / cm 3 .

[0082] Compared with cast niobium silicon alloy, the room temperature fracture toughness and high temperature oxidation resistance are greatly improved, which accelerates the application of niobium silicon alloy in the new generation of lightweight aircraft engine high-pressure turbine blades, solves the problem, and actively promotes the application process of niobium silicon alloy in aircraft engine thermal components.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure and high toughness and oxidation resistance, characterized in that: It includes the following steps: Step 1: Weigh the niobium silicon alloy raw materials; Step 2: Vacuum non-consumable melting ingot; Step 3: Cut the ingot in step 2 into metal plates by wire cutting, clean and polish them to obtain metal plates with no processing marks and clean surfaces; Step 4: laser remelting the metal plate to obtain a 200-400 μm thick sub-nanometer eutectic structure layer; Step 5: Polish the remelted metal plate in step 4 with sandpaper; Step 6: Shot peening the metal plate in step 5 to obtain a nano-ultrafine grain structure with a thickness of 10-40 μm; Step 7: Ultrasonic cleaning and drying of the obtained metal plate, i.e., the niobium silicon alloy with multi-gradient eutectic size on the surface taking into account high strength, toughness and oxidation resistance.

2. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 1, characterized in that: The niobium silicon alloy raw materials in step 1 are weighed in the proportion of 16% Si, 30% Ti, x% Sm and 54-x% Nb in atomic percentage, and the total atomic percentage is 100%.

3. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 2, characterized in that: In step 1, the percentage content of x% Sm in the niobium silicon alloy raw material is 0.1 or 0.2 or 0.

5.

4. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 3, characterized in that: The vacuum non-consumable melting ingot in step 2 includes the following steps: Step 21: Put the weighed single element into a vacuum non-consumable water-cooled copper crucible according to the principle that the single element with high melting point is on the top and the single element with low melting point is on the bottom; Step 22: Use the mechanical pump and vacuum pump to pump the pressure of the vacuum melting chamber to 2×10 -3 Pa, flush with protective argon gas to 400Pa-600Pa; Step 2 and 3: Carry out tungsten electrode non-consumable smelting with a smelting current of 500A-700A to obtain niobium silicon ingots.

5. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 4, characterized in that: The laser remelting process of the metal plate in step 4 includes the following steps: Step 41: Fix the metal plate obtained in step 3 on the laser beam platform and evacuate to 2×10 -3 Pa, flush with protective argon gas to 300Pa; Step 42: Use a 40mA laser beam to perform a single pass zigzag remelting on the surface of the metal plate; Step 43: The platform movement rate during the remelting process is 200mm / min-400mm / min, and the final cooling is used to obtain the preparation of the laser beam remelted metal sheet.

6. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 5, characterized in that: The parameters for shot peening the metal plate in step 6 are: Ceramic shot with a diameter of 0.2 mm, a ceramic shot flow rate of 6-8 Kg / min, a compressed gas pressure of 0.5 MPa, and a shot peening time of 40-60 min are used to finally obtain a 10-40 μm thick nano-ultrafine grain niobium silicon plate after shot peening.

7. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 4 or 6, characterized in that: The ingot in step 2 was melted repeatedly 8 times.

8. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 7, characterized in that: In step 3, the metal plate is cleaned by ultrasonic cleaning and acetone cleaning.

9. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 8, characterized in that: The platform moving speed during the remelting process in step 43 is: 300mm / min or 400mm / min.

10. The method for preparing a niobium-silicon alloy with a surface multi-gradient eutectic structure having both high strength and toughness and oxidation resistance according to claim 6, characterized in that: The shot peening time in step six is ​​50-60 minutes.

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