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CN-122013098-A - Niobium alloy surface antioxidation composite NbSi2-SiO2Ceramic layer and preparation method and application thereof

CN122013098ACN 122013098 ACN122013098 ACN 122013098ACN-122013098-A

Abstract

The invention discloses an antioxidant composite NbSi 2 -SiO 2 ceramic layer on the surface of a niobium alloy, and a preparation method and application thereof, and belongs to the technical field of coatings. The coating has a two-layer composite structure, wherein the surface layer is a composite layer of nanocrystalline-amorphous SiO 2 , the inner layer is an NbSi 2 diffusion layer with gradient change of Si concentration, and in the composite layer of nanocrystalline-amorphous SiO 2 , the volume fraction Vc of nanocrystalline is 30-60%, and the volume fraction Vc of amorphous is 40-70%. The nano-crystal is SiO 2 particles with a long-range ordered structure, the average particle size is 10-50 nm, and the nano-crystal is dispersed in an amorphous SiO 2 matrix with a disordered structure. The coating structure of the invention obviously improves the high-temperature oxidation resistance, thermal shock resistance and interface bonding strength of the coating, and shows a self-healing protection mechanism in the high-temperature oxidation process.

Inventors

  • Jia Chenjie
  • LI ZHENGXIAN
  • ZHAN MENGLING

Assignees

  • 江苏集萃表面工程技术研究所有限公司

Dates

Publication Date
20260512
Application Date
20260209

Claims (10)

  1. 1. An antioxidation composite NbSi 2 -SiO 2 ceramic layer on the surface of niobium alloy is characterized by having a two-layer composite structure, wherein the surface layer is a composite layer of nanocrystalline-amorphous SiO 2 , the inner layer is a NbSi 2 diffusion layer with gradient change of Si concentration, and the volume fraction Vc of nanocrystalline is 30% -60% and the volume fraction Vc of amorphous is 40% -70% in the composite layer of nanocrystalline-amorphous SiO 2 .
  2. 2. The niobium alloy surface oxidation-resistant composite NbSi 2 -SiO 2 ceramic layer as claimed in claim 1, wherein the nanocrystals are SiO 2 particles with long-range order structure, the average particle size is 10-50nm, and the nanocrystals are dispersed in an amorphous SiO 2 matrix with disordered structure.
  3. 3. The niobium alloy surface oxidation-resistant composite NbSi 2 -SiO 2 ceramic layer as claimed in claim 1, wherein the NbSi 2 diffusion layer is columnar and grown on the surface of the niobium alloy substrate, and the thickness of the NbSi 2 diffusion layer is more than 15 μm.
  4. 4. The surface oxidation-resistant composite NbSi 2 -SiO 2 ceramic layer of claim 1, wherein the ceramic layer is capable of withstanding at least 20 cycles without cracking during thermal shock cycles at room temperature to 1000 ℃.
  5. 5. The preparation method of the niobium alloy surface oxidation-resistant composite NbSi 2 -SiO 2 ceramic layer according to any one of claims 1 to 4, which is characterized by comprising the following steps: Step one, cleaning niobium alloy; Step two, taking the cleaned niobium alloy to be infiltrated as a workpiece electrode, taking a Si target material with a clean surface as a source electrode, placing the workpiece electrode and the source electrode in a double-glow plasma surface metallurgical furnace, vacuumizing to a distance of less than 0.1Pa, filling argon into the furnace to ensure that the air pressure in the furnace is greater than 200Pa, exhausting again, repeating at least twice, controlling the air pressure in the furnace to be 38Pa, switching on a workpiece electrode power supply, adjusting the workpiece electrode voltage to 300-350V, keeping for 10-20min, then adjusting the workpiece electrode voltage to 400-500V, adjusting the source electrode voltage to 750-900V, performing double-glow plasma siliconizing to ensure that the surface temperature of the niobium alloy is increased to 850-950 ℃ and the heat preservation time is 2-4h; preparing an SiC outer layer by magnetron sputtering after siliconizing is finished, namely taking an SiC target as a source electrode under the argon atmosphere, fixing the DC power to be 250W, keeping the working pressure at 0.30 Pa and the total Ar gas flow at 60 sccm in the deposition process, sputtering and depositing a SiC layer with the thickness of 300-600 nm, heating to 300 ℃, and obtaining the SiC coating after the deposition time is 60-90 minutes; step four, the surface texturing of the pulse laser is that Nd-YAG pulse laser is adopted to scan the surface of the SiC coating, The energy density E 1 of the first laser treatment is 5-15.0J/cm 2 , the laser wavelength is 1064 and nm, the frequency is 20-50kHz, the pulse width is 10-200ns, the scanning speed is 500-1500mm/s, and the light spot overlapping rate is 30-50%; The energy density E 2 of the second laser treatment is 1.5-3.5J/cm 2 , the laser wavelength is still 1064 nm, the frequency is 10-30kHz, the pulse width is 500-2000ns, the scanning speed is 200-600mm/s, the light spot overlapping rate is 70-85%, and finally the NbSi 2 -SiO 2 ceramic layer is obtained.
  6. 6. The method according to claim 5, wherein in the first step, the niobium alloy is polished to a mirror surface by sand paper, polished by a polisher after the polishing treatment, and then immersed in absolute ethanol for ultrasonic cleaning for 20 to 30 minutes.
  7. 7. The method of claim 5, wherein in step four, E 2 /E 1 is 0.2< 0.5.
  8. 8. The use of a niobium alloy surface oxidation resistant composite NbSi 2 -SiO 2 ceramic layer according to any one of claims 1-4 in aerospace high temperature environments.
  9. 9. The method according to claim 8, wherein the high temperature is in the range of 800 ℃ to 1600 ℃.
  10. 10. The use of claim 8, wherein the aerospace high temperature environment comprises turbine engine blades, hypersonic aircraft leading edges and wing leading edges, rocket engine thrust chamber extensions, nozzle vanes.

Description

Niobium alloy surface antioxidation composite NbSi 2-SiO2 ceramic layer and preparation method and application thereof Technical Field The invention relates to an antioxidant composite NbSi 2-SiO2 ceramic layer on the surface of a niobium alloy, and a preparation method and application thereof, and belongs to the technical field of coatings. Background The metal niobium has a series of excellent characteristics of high melting point, low vapor pressure, good cold processing performance, high chemical stability, strong acid and alkali corrosion resistance, small thermal neutron capture section, superconductivity and the like, and is an important functional material in the fields of military industry, aerospace, atomic energy and the like. Such as weapon propellers, aerospace engines, nuclear reactor structural materials, etc., while niobium has been widely used in steel for nearly a century as an important alloying element, the addition of a small amount of niobium in steel can greatly improve its strength, improve its mechanical and welding properties, and improve corrosion resistance. The most studied and applied niobium alloy is in the aerospace field, in recent years, along with the rapid development of aerospace industry of various countries in the world, higher requirements are also put forward on various performance indexes of the niobium alloy, and the most applied niobium alloy of Nb521, C-103, nb-1Zr and low density is currently available. However, based on the characteristics of the metal niobium, the oxidation resistance of the niobium alloy at high temperature is insufficient, at lower temperature, niobium reacts with oxygen to form a protective oxide film on the surface, the metal niobium is subjected to severe oxidation at 600 ℃ or above, namely 'PEST' oxidation phenomenon, and the higher the temperature is, the faster the oxidation rate is, so that the preparation of an oxidation-resistant coating on the surface of the niobium alloy is the most effective means for solving the problem. Therefore, a surface treatment method of the niobium alloy needs to be explored, so that the application of the niobium alloy in a high-temperature environment is effectively improved. The aluminide coating may form a dense Al 2O3 oxide scale in high temperature atmosphere to prevent further oxidation of the substrate. Unfortunately, aluminide coatings have poor mechanical properties at high temperatures and are prone to spalling at the interdiffusion layer. This can expose the substrate to air and cause the substrate to quickly "fail," limiting the application of the aluminide coating. Of the numerous Nb compounds, nbSi 2 is considered as a potential coating material due to its excellent physicochemical properties and good thermal compatibility with Nb-based materials. Under the high temperature state, oxygen can react with Si element in the coating preferentially to generate SiO 2 glass phase, and partial oxygen is consumed and meanwhile oxygen is prevented from diffusing inwards, so that the formation of Nb 2O5 is delayed. However, the thermal expansion Coefficients (CET) of the NbSi 2 coating and the Nb substrate are 11.7×10 -6K-1 and 7.3×10 -6K-1, respectively, and the mismatch of the thermal expansion coefficients can lead to the coating being extremely liable to crack and peel under the condition of high temperature. So that there is a certain requirement for the NbSi 2 coating structure to prevent this. Therefore, a niobium alloy surface antioxidation composite NbSi 2-SiO2 ceramic layer and a preparation method and application thereof are needed. Disclosure of Invention The invention aims to limit the application of Nb521 alloy under high temperature condition aiming at the reduction of high temperature mechanical property of the alloy caused by expansion of high temperature oxide and pulverization of the alloy surface at high temperature. The invention provides an antioxidant coating for improving the surface of a niobium alloy based on a composite double-glow plasma-pulse laser synergistic means, and an NbSi 2-SiO2 composite ceramic layer which has the characteristics of high temperature resistance, oxidation resistance, good high-temperature thermal stability and the like is prepared on the surface of the Nb521 alloy. Meanwhile, the characteristic of double-glow plasma plating is utilized to prepare a diffusion layer with a columnar growth structure, and the diffusion layer is compounded with the nanocrystalline and amorphous SiO 2 composite surface layer formed after the secondary treatment of the SiC film. Further improving the thermodynamic performance. The coating prepared by the method can bear at least 20 times of cycles without crack generation in the thermal shock cycle at the room temperature to 1000 ℃. Meanwhile, the invention discloses a preparation method of the niobium alloy surface antioxidation composite NbSi 2-SiO2 ceramic layer. Meanwhile, the invention discloses application of the ni