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

Abstract

The application relates to a preparation method of a niobium-silicon alloy with high strength and toughness and oxidation resistance, and relates to post-treatment preparation of high-melting-point active alloy materials. The application solves the problem that the room-temperature fracture toughness and high-temperature oxidation resistance of the existing niobium-silicon alloy cannot be considered simultaneously. The application comprises the following steps: step one, niobium-silicon alloy raw materials are weighed; step two, vacuum non-consumable smelting is carried out to obtain ingots; step three, the ingots in step two are cut into metal plates by using wire cutting, and the metal plates are cleaned and polished to obtain the metal plates; step four, laser remelting treatment is carried out on the metal plates to obtain a sub-nanometer eutectic structure layer; step five, sandpaper polishing treatment is carried out; step six, the metal plates in step five are subjected to shot blasting treatment to obtain a 10-40 mu m thick nanometer ultra-fine grain structure; and step seven, the obtained metal plates are subjected to ultrasonic cleaning and drying to obtain the niobium-silicon alloy with high strength and toughness and oxidation resistance. The application is used for post-treatment preparation of high-melting-point active alloy materials.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a surface-strengthened niobium-silicon alloy, in particular to a preparation method of a niobium-silicon alloy with surface multi-gradient eutectic structures and high strength and toughness and oxidation resistance, and belongs to the technical field of post-processing preparation of high-melting-point active alloy materials. BACKGROUND

[0002] The aero-engine is called the "industrial palm pearl", and develops towards higher temperature and larger thrust. The fifth-generation aero-engine requires a thrust-to-weight ratio of more than 15, and the service temperature of the high-pressure turbine blade material reaches 1250-1400 DEG C, which puts forward higher requirements for the blade material of the aero-engine.

[0003] At present, the service temperature of the high-pressure turbine blade prepared from the Ni-based single crystal alloy is 1100-1150 DEG C, that is, about 85% of the melting point of the Ni-based single crystal alloy, and it is difficult to achieve a substantial breakthrough to reach the limit working temperature, and the demand of the future aero-engine for high thrust-to-weight ratio cannot be met.

[0004] The melting point of the niobium-silicon alloy is more than 1900 DEG C, and the potential service temperature is more than 1300 DEG C, which is an important potential application material for the high-pressure turbine blade of the new-generation aero-engine. The niobium-silicon alloy is mainly composed of a ductile niobium-silicon solid solution phase and a brittle silicide phase. The large-size silicide phase will significantly deteriorate the room-temperature fracture toughness and oxidation resistance due to intrinsic brittleness, so regulating the size and content of the silicide phase is a favorable way to improve the room-temperature toughness and high-temperature oxidation resistance of the niobium-silicon alloy.

[0005] The laser remelting of the niobium-silicon alloy can refine the coarse silicide phase, but the remelted niobium-silicon alloy structure will produce cracks due to large internal stress, finally resulting in 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 of the surface multi-gradient eutectic size and the remelted cracks are inhibited, so as to improve the strength and toughness and the oxidation resistance, so as to quickly make the niobium-silicon alloy into application.

[0006] In summary, the existing niobium-silicon alloy silicide phase structure is coarse, and the room-temperature toughness and high-temperature oxidation resistance are deteriorated. SUMMARY

[0007] The purpose of the present application is to solve the problem of the existing niobium-silicon alloy silicide phase structure being coarse and the room-temperature toughness and high-temperature oxidation resistance being deteriorated, and to provide a preparation method of a niobium-silicon alloy with surface multi-gradient eutectic structures and high strength and toughness and oxidation resistance.

[0008] The technical scheme of the present application is: a preparation method of a niobium-silicon alloy with surface multi-gradient eutectic structures and high strength and toughness and oxidation resistance comprises the following steps:

[0009] Step one: weigh the niobium-silicon alloy raw materials;

[0010] Step two: vacuum non-consumable smelting ingot;

[0011] Step three: cut the ingot in step two into a metal plate using wire cutting, clean and polish to obtain a metal plate without processing marks and clean surface;

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

[0013] Step five: polish the remelted metal plate in step four using sandpaper;

[0014] Step six: shot blasting is performed on the metal plate in step five to obtain a 10-40 μm thick nano ultra-fine grain structure;

[0015] Step seven: ultrasonic cleaning and drying the obtained metal plate, which is a surface multi-gradient eutectic size niobium-silicon alloy with high strength and toughness and oxidation resistance.

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

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

[0018] Further, the vacuum non-consumable smelting ingot in step two includes the following steps:

[0019] Step two one: according to the principle of high melting point elements on the top and low melting point elements on the bottom, put the weighed elemental substances into the vacuum non-consumable water-cooled copper crucible;

[0020] Step two two: sequentially use a mechanical pump and a vacuum pump to reduce the pressure in the vacuum smelting chamber to 2×10 -3 Pa, and flush in protective argon gas to 400 Pa-600 Pa;

[0021] Step two three: perform tungsten electrode non-consumable smelting, the smelting current is 500 A-700 A, and the niobium-silicon ingot is obtained.

[0022] Further, the laser remelting treatment of the metal plate in step four includes the following steps:

[0023] Step four one: fix the metal plate obtained in step three on the laser beam platform, vacuum to 2×10 -3 Pa, and flush in protective argon gas to 300 Pa;

[0024] Step four two: the surface of the metal plate is zigzag remelted by a laser beam with 40mA in a single pass;

[0025] Step four three: the moving rate of the platform during the remelting process is 200mm / min-400mm / min, and the laser beam remelted metal plate is obtained after final cooling.

[0026] Further, the shot blasting parameters of the metal plate in step six are as follows: the diameter of the ceramic shot is 0.2mm, the ceramic shot flow is 6-8Kg / min, the compressed gas pressure is 0.5MPa, and the shot blasting time is 40-60min, and finally the nanometer ultra-fine crystal structure niobium silicon plate with a thickness of 10-40μm is obtained after shot blasting.

[0027] Preferably, the ingot is repeatedly melted for 8 times in step two.

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

[0029] Preferably, the moving rate of the platform during the remelting process is 300mm / min or 400mm / min in step four three.

[0030] Preferably, the shot blasting time in step six is 50-60min.

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

[0032] 1. The present application adopts reasonable alloy composition, the Si content is 16%, which is the near-eutectic composition point, to ensure that there is no large-size primary silicon phase and niobium-based solid solution phase in the structure, the Ti content is 30% to improve the room temperature toughness, the high content of Ti element increases the toughness of the niobium-based solid solution, the rare earth element Sm refines the eutectic structure and reduces the oxygen element content of the grain boundary, thereby improving the toughness and high-temperature oxidation resistance of the matrix alloy. The eutectic niobium silicon alloy with a more fine structure is prepared, the eutectic group size is reduced by 50% after 0.2Sm element doping, and the toughness of the as-cast alloy itself reaches 9.4Mpa·m 1 / 2 , the oxidation performance at 1200℃ / 50h is 239.4mg / cm 3 , the overall performance is good, and further laser remelting and shot blasting produce the silicide phase in the multi-gradient eutectic structure.

[0033] 2. The present application uses the ceramic shot with a diameter of 0.2mm and the compressive stress generated by the shot blasting for 40-60min to offset the internal stress generated by the remelting, thereby avoiding the crack problem caused by the excessive cooling rate of the remelting, and finally the gradient eutectic structure greatly improves the room temperature toughness and high-temperature oxidation resistance of the niobium silicon alloy. The oil nozzle of the aero-engine and other hot end parts can be subsequently prepared. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the microstructure of Nb-16Si-30Ti-0.5Sm alloy in the shot time of 50 min and the moving speed of 300 mm / min of the Nb-Si metal plate in embodiment 1 of the application.

[0035] Figure 2 is a schematic diagram of the comparison of the room temperature fracture toughness values of the multi-gradient Nb-Si alloy in embodiment 1 of the application.

[0036] Figure 3 is a schematic diagram of the comparison of the high-temperature oxidation resistance performance of the multi-gradient Nb-Si alloy in embodiment 1 of the application. DETAILED DESCRIPTION

[0037] Embodiment 1: A preparation method of the surface multi-gradient eutectic structure Nb-Si alloy with high strength and toughness and oxidation resistance performance, comprising the following steps:

[0038] Step 1: Weigh the Nb-Si alloy raw material;

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

[0040] Step 3: Cut the ingot in step 2 into a metal plate by wire cutting, clean and polish it to obtain a metal plate without processing marks and clean surface;

[0041] Step 4: Perform laser remelting treatment on 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 by using sandpaper;

[0043] Step 6: Perform shot peening treatment on the metal plate in step 5 to obtain a 10-40 μm thick nano ultra-fine grain structure;

[0044] Step 7: Ultrasonic cleaning and drying the obtained metal plate, i.e. the surface multi-gradient eutectic size Nb-Si alloy with high strength and toughness and oxidation resistance performance.

[0045] The expression of the Nb-Si alloy prepared by the embodiment is Nb-16Si-30Ti-0.1Sm, Nb-16Si-30Ti-0.2Sm or Nb-16Si-30Ti-0.5Sm.

[0046] The metal plate in step 3 of the embodiment is first polished by sandpaper to remove the wire cutting marks, and then cleaned by alcohol. It can facilitate the removal of processing marks in the wire cutting process and ensure the surface to be clean and flat.

[0047] Specific implementation two: the niobium silicon alloy raw material in step one of the embodiment is weighed according to the proportion of 16% Si, 30% Ti, x% Sm and 54-x% Nb in atomic percentage, and the total atomic percentage is 100%.

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

[0049] The raw material elements in step one are sequentially subjected to ultrasonic treatment and drying treatment. The alcohol content of the ultrasonic treatment is 90%, and the drying treatment uses a drying box to remove the alcohol attached during the ultrasonic treatment.

[0050] The other components are the same as in embodiment one.

[0051] Specific implementation three: the percentage content of x% Sm in the niobium silicon alloy raw material in step one of the embodiment is 0.1 or 0.2 or 0.5.

[0052] In this way, too little Sm content has little effect, and when the content is higher than 0.5%, the refining effect becomes very weak and unnecessary. The other components and connections are the same as in embodiment one or two.

[0053] Specific implementation four: the vacuum non-consumable smelting ingot in step two of the embodiment includes the following steps:

[0054] Step two one: according to the principle of placing high melting point elements on top and low melting point elements on bottom, the weighed elemental elements are placed into the vacuum non-consumable water-cooled copper crucible;

[0055] Step two two: sequentially use a mechanical pump and a vacuum pump to draw the pressure in the vacuum smelting chamber to 2x10 -3 Pa, and flush in protective argon to 400Pa-600Pa;

[0056] Step two three: perform tungsten electrode non-consumable smelting, the smelting current is 500A-700A, and a niobium silicon ingot is obtained.

[0057] The argon filling value in step two of the embodiment is preferably 600Pa. The other components and connections are the same as in any one of embodiments one to three.

[0058] Specific implementation five: the laser remelting treatment of the metal plate in step four of the embodiment includes the following steps:

[0059] Step four one: fix the metal plate obtained in step three on the laser beam platform, vacuumize to 2x10 -3 Pa, flush protective argon gas to 300Pa;

[0060] Step four two: zigzag re-melting of the surface of the metal plate by 40mA laser beam in single pass;

[0061] Step four three: the moving speed of the platform during the re-melting process is 200mm / min-400mm / min, and finally the preparation of the laser beam re-melted metal plate is obtained.

[0062] In this way, the zigzag re-melting does not appear mutation, ensuring the structural stability of the surface re-melted layer. The other components and connection relationships are the same as any one of the first to fourth embodiments.

[0063] Embodiment six: the shot blasting parameters of the metal plate in step six of the embodiment are as follows:

[0064] The diameter of the ceramic shot is 0.2mm, the ceramic shot flow is 6-8Kg / min, the compressed gas pressure is 0.5MPa, and the shot blasting time is 40-60min, finally obtaining a 10-40μm thick nano ultra-fine crystal structure niobium silicon plate after shot blasting treatment.

[0065] In this way, gradient eutectic niobium silicon structure can be obtained, which takes into account the room temperature fracture toughness and high temperature oxidation resistance. The other components and connection relationships are the same as any one of the first to fifth embodiments.

[0066] Embodiment seven: the ingot re-melting in step two of the embodiment is repeated 8 times.

[0067] In this way, the segregation is eliminated, and the structure is stable. The other components and connection relationships are the same as any one of the first to sixth embodiments.

[0068] Embodiment eight: the cleaning of the metal plate in step three of the embodiment is cleaned by ultrasonic and acetone.

[0069] In this way, the cleaning is cleaner and there is no impurity. The other components and connection relationships are the same as any one of the first to seventh embodiments.

[0070] Embodiment nine: the moving speed of the platform during the re-melting process in step four three of the embodiment is 300mm / min or 400mm / min. Gradient eutectic niobium silicon structure can be obtained, which takes into account the room temperature fracture toughness and high temperature oxidation resistance.

[0071] Specific implementation ten: the shot time in step six of the embodiment is 50-60 min. In this way, the gradient eutectic niobium-silicon structure can be obtained, and the room temperature fracture toughness and high temperature oxidation resistance are considered. The other compositions and connection relationships are the same as any one of specific implementations one to nine.

[0072] In combination Figures 1 to 3 Embodiment 1 of the present application is described:

[0073] A preparation method of a surface multi-gradient eutectic structure niobium-silicon alloy considering high strength and toughness and oxidation resistance performance, comprising the following steps:

[0074] Step one: according to the proportion of 16% Si, 30% Ti, x% Sm and 54-x% Nb in atomic percentage, the elemental Si, Ti, Sm and Nb are weighed, the total atomic percentage is 100%, and the Nb is Cylindrical, 1-3 cm flaky, granular sponge titanium and elemental filamentous Sm.

[0075] Step two: according to the principle of high melting point elements on the top and low melting point elements on the bottom, the weighed elemental elements are put into a vacuum non-consumable water-cooled copper crucible, and a cast ingot is obtained by vacuum non-consumable smelting.

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

[0077] The surface of the remelted niobium-silicon plate is polished flat, ceramic shots with a diameter of 0.2 mm are used, the ceramic shot flow is 6-8 Kg / min, the compressed gas pressure is 0.5 MPa, and the shot time is 50 min, and finally a shot-treated surface gradient eutectic niobium-silicon plate is obtained.

[0078] From Figure 1 It can be seen that the surface multi-gradient eutectic niobium-silicon structure has the largest size of the Nbss / Nb5Si3 eutectic structure at the bottom, the silicide is more than 10 μm, there is 0.5-5 μm eutectic structure in the middle, the eutectic structure is more fine, there is a large number of nanometer ultra-fine crystal eutectic in the surface layer, and the white niobium-based solid solution phase is mostly changed from irregular ellipse to spherical.

[0079] Figure 1 The phase detection result in the table shows that the phase composition is Nbss and Nb5Si3.

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

[0081] Figure 3 The oxidation weight gain of the alloy at 1200℃ / 50h is only 51.5mg / cm 3 .

[0082] Compared with the room temperature fracture toughness and high temperature oxidation resistance of the as-cast niobium silicon alloy, the room temperature fracture toughness and high temperature oxidation resistance of the alloy are greatly improved, the application of the niobium silicon alloy in the new generation of light weight aero-engine high pressure turbine blade is accelerated, the neck problem is solved, and the application process of the niobium silicon alloy in the aero-engine hot part is actively promoted.

[0083] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a niobium-silicon alloy with high strength and toughness and oxidation resistance by surface multi-gradient eutectic structure, characterized in that: It comprises the following steps: Step one: weigh the niobium-silicon alloy raw materials; The niobium-silicon alloy raw materials in step one are weighed according to the atomic percentage of 16% Si, 30% Ti, x% Sm, and 54-x% Nb. The atomic percentage total is 100%. Step two: vacuum non-consumable smelting ingot; Step three: cut the ingot in step two into a metal plate using wire cutting, clean and polish it to obtain a metal plate without processing marks and clean surface; Step four: perform laser remelting treatment on the metal plate to obtain a 200-400 μm thick sub-nanometer eutectic structure layer; Step five: polish the remelted metal plate in step four using sandpaper; Step six: perform shot blasting on the metal plate in step five to obtain a 10-40 μm thick nano-ultrafine crystal structure; Step seven: ultrasonic cleaning and drying the obtained metal plate, which is a niobium-silicon alloy with surface multi-gradient eutectic size and high strength and toughness and oxidation resistance.

2. The method according to claim 1, characterized in that: The percentage content of x% Sm in the niobium-silicon alloy raw materials in step one is 0.1 or 0.2 or 0.

5.

3. The method according to claim 2, wherein the method is characterized by: The vacuum non-consumable smelting ingot in step two comprises the following steps: Step two one: place the weighed elemental substances into the vacuum non-consumable water-cooled copper crucible according to the principle of high-melting-point elements on top and low-melting-point elements on the bottom; Step two: the pressure of the vacuum melting chamber was pumped to 2 x 10 -3 Pa, and protective argon was injected to 400 Pa-600 Pa; Step two three: perform tungsten electrode non-consumable smelting with a current of 500A-700A to obtain a niobium-silicon ingot.

4. The method according to claim 3, characterized in that: The laser remelting treatment on the metal plate in step four comprises the following steps: Step four one: fix the metal plate obtained in step three on the laser beam platform, vacuumize to 2x10 -3 Pa, flush protective argon gas to 300 Pa; Step four two: use a 40mA laser beam to perform single-pass zigzag remelting on the surface of the metal plate; Step four three: the platform moving rate during remelting is 200mm / min-400mm / min, and the final cooling obtains the preparation of the laser beam remelted metal plate.

5. The method according to claim 4, characterized in that: The shot blasting parameters for the metal plate in step six are: Use ceramic shots with a diameter of 0.2mm, ceramic shot flow of 6-8kg / min, compressed gas pressure of 0.5MPa, and shot blasting time of 40-60min to finally obtain a 10-40μm thick nano-ultrafine crystal structure niobium-silicon plate after shot blasting.

6. The method according to claim 3, characterized in that: The ingot in step two is repeatedly smelted 8 times.

7. The method according to claim 6, characterized in that: The cleaning of the metal plate in step three uses ultrasonic and acetone cleaning.

8. The preparation method of the niobium-silicon alloy with surface multi-gradient eutectic structure and high strength and toughness and oxidation resistance according to claim 7, characterized in that: The platform moving rate during remelting in step four three is 300mm / min or 400mm / min.

9. The method according to claim 5, characterized in that: The shot blasting time in step six is 50-60min.

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