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CN-121990845-A - Graphite ablation-resistant composite coating and preparation method thereof

CN121990845ACN 121990845 ACN121990845 ACN 121990845ACN-121990845-A

Abstract

The invention discloses a graphite ablation-resistant composite coating and a preparation method thereof, and belongs to the technical field of coatings. The graphite ablation-resistant composite coating comprises a graphite substrate, a SiC compact transition and sealing layer, a ZrC porous heat insulation and strain tolerance layer and an HfC-TaC compact ultrahigh temperature ablation coating which are sequentially arranged on the surface of the graphite substrate from inside to outside, wherein the linear expansion coefficients of the SiC compact transition and sealing layer, the ZrC porous heat insulation and strain tolerance layer and the HfC-TaC compact ultrahigh temperature ablation coating gradually decrease from outside to inside. The coating of the invention is distributed in a gradient manner in components, mechanical properties and thermal expansion coefficients, and the continuous change can effectively relieve the property mismatch between the substrate and the coating, so that the outermost layer is subjected to smaller tensile stress in the ablation process. The coating obtained by the invention has stable adhesive force under the action of heat stress, does not generate layering cracking and has good ablation resistance.

Inventors

  • LIU XINZE
  • LI ZHENGXIAN
  • YANG KAI
  • DANG BO
  • ZHAN MENGLING

Assignees

  • 江苏集萃表面工程技术研究所有限公司

Dates

Publication Date
20260508
Application Date
20260211

Claims (10)

  1. 1. A graphite ablation-resistant composite coating is characterized in that a SiC compact transition and sealing layer, a ZrC porous heat insulation and strain tolerance layer and an HfC-TaC compact ultrahigh temperature ablation coating are sequentially arranged on the surface of a graphite substrate from inside to outside, and the linear expansion coefficients of the SiC compact transition and sealing layer, the ZrC porous heat insulation and strain tolerance layer and the HfC-TaC compact ultrahigh temperature ablation coating are gradually reduced from outside to inside.
  2. 2. The graphite ablation-resistant composite coating according to claim 1, wherein the thickness of the SiC compact transition and sealing layer is 3-4 μm, the thickness of the ZrC porous heat insulation and strain tolerance layer is 4.5-8 μm, and the thickness of the HfC-TaC compact ultrahigh temperature ablation coating is 21-24 μm.
  3. 3. The graphite ablation-resistant composite coating according to claim 1, wherein the surface hardness of the coating is 1351.63-1589.24HV, the flexural strength thereof is 300-600MPa at room temperature, 200-400MPa at 1500 ℃, and 100-250MPa at 2000 ℃. The thermal conductivity at room temperature is 20-40W/(m.k), the thermal conductivity at 2000 ℃ is 15-25W/(m.k), the high-temperature steady-state emissivity at 2000 ℃ is 0.7-0.9, the critical load during separation between film bases is 0.27-0.29N, the depth of 40 times of ablation pits is 39.85-45.03 mu m, and the diameter of 40 times of ablation pits is 1237.74-1527.44 mu m.
  4. 4. The method for preparing the graphite ablation-resistant composite coating according to any one of claims 1-3, which is characterized by comprising the following steps: Step one, performing plasma activation pretreatment on the surface of a graphite substrate; Step two, generating a SiC compact transition and sealing layer on the surface of the graphite matrix pretreated by the three-time reaction infiltration method; step three, coating slurry on the surface of the SiC compact transition and sealing layer to deposit a ZrC porous heat insulation and strain tolerance layer; And fourthly, preparing the HfC-TaC compact ultrahigh-temperature ablative coating on the surface of the ZrC porous heat insulation and strain tolerance layer by using a plasma spraying method.
  5. 5. The method of claim 4, wherein the plasma activation pretreatment is performed by introducing argon gas at a power of 100-200W and a gas pressure of 10-20Pa for 10-20min.
  6. 6. The preparation method of claim 4, wherein in the second step, the pretreatment by the three-time reaction infiltration method comprises the steps of placing silicon blocks around a graphite substrate, Introducing argon, raising the temperature from room temperature to 1430-1470 ℃, raising the temperature to 5-10 ℃ per minute, preserving the heat for 30-60 minutes, cooling along with a furnace, and polishing to remove the shell; Secondary reaction infiltration, namely raising the temperature from room temperature to 1530-1570 ℃, raising the temperature to 5-10 ℃ per minute, preserving the heat for 40-80 minutes, cooling along with a furnace, and polishing to remove the shell; and (3) performing three-time reaction infiltration, namely raising the temperature from room temperature to 1630-1670 ℃, keeping the temperature at 5-10 ℃ per minute for 60-120 min, cooling along with a furnace, and polishing to remove the shell.
  7. 7. The method according to claim 4, wherein in the third step, the surface of the graphite substrate on which the SiC dense transition and sealing layer deposition is completed is coated with slurry to deposit a ZrC porous heat insulation and strain tolerance layer, the raw materials comprise 10-20% by weight of pore-forming agent, 3-4% by weight of binder, 1-2% by weight of dispersing agent, 20-30% by weight of solvent and the balance ZrC powder, and the graphite substrate is sintered in an argon atmosphere, the heat preservation time is 60-120min, the temperature is 1800-2000 ℃, the heating rate is 5-7 ℃ per min, and the porosity is 30% -50%.
  8. 8. The method of claim 7, wherein the pore-forming agent comprises polymethyl methacrylate, the binder comprises PVB, the dispersing agent comprises PVP, and the solvent comprises absolute ethanol.
  9. 9. The preparation method of the graphite substrate according to claim 4, wherein in the fourth step, the spraying angle of the powder feeding spray gun is perpendicular to the surface of the graphite substrate by a plasma spraying method, wherein powder used by the plasma spraying method is HfC-TaC powder, the HfC-TaC powder is compound powder with a molar ratio of 1:1-1:3, plasma gas is Ar, the power is 40-60kW, the spraying distance is 100-140mm, the powder feeding speed is 20-30g/min, and the moving speed of the spray gun is 500-800mm/s.
  10. 10. The application of the graphite ablation-resistant composite coating according to any one of claims 1-3 in a high-energy discharge environment.

Description

Graphite ablation-resistant composite coating and preparation method thereof Technical Field The invention relates to a graphite anti-ablation composite coating and a preparation method thereof, in particular to a novel graphite anti-ablation composite coating and a preparation method thereof, and belongs to the technical field of coatings. Background The graphite material has low strength and weak binding force, and is easy to crack and peel under the action of external force, so that after high-energy discharge ablation under extreme conditions such as high temperature, high voltage, high current density, high-speed air flow and the like, the mass loss and the volume ablation rate of the graphite surface are much larger than those of alloy materials such as tungsten and copper, and the application of the graphite material in a high-energy discharge environment is restricted. The ablation failure of graphite refers to that the graphite which is contacted up and down generates arc discharge by the ultrahigh arc energy born in the electric conduction and heat conduction processes, so that a great amount of electric quantity transfer and exchange occur, the surface temperature of the graphite with layered arrangement and loose crystal structure is increased to the phase transition temperature, sublimation and remelting of surface layer graphite are caused, breakdown or fracture failure finally occurs, and unnecessary mass and volume loss is caused. The ablation process can be divided into a graphite heating process and a material removing process, wherein the heat flow input of an arc to the graphite surface in an arc root region can generate joule heating on the surface, and meanwhile, the heat flow input can heat an electrode material to generate phase change, so that the graphite material is subjected to solid-liquid, solid-gas conversion, oxidization and other processes and separated from the surface. The ultra-high temperature ceramic material represented by TaC has excellent high temperature performance, so that the ultra-high temperature ceramic material can effectively protect graphite materials in the form of a coating in high temperature environments such as corrosive solution, aerobic atmosphere and the like, and improves the oxidation resistance, corrosion resistance and the like of a matrix. However, the thermal expansion coefficient and mechanical properties of graphite and tantalum carbide are greatly different, and the increased property mismatch leads to the occurrence of thermal stress and dislocation, and the adhesion of the coating begins to decrease under the action of the thermal stress and is extremely easy to generate delamination cracking or even peeling, so that the need for adopting a composite coating is urgent to reduce the property mismatch. Disclosure of Invention The invention aims to overcome the defects of the prior art, and aims to provide the graphite anti-ablation composite coating with good anti-ablation performance and strong bonding force between film bases. The invention also aims to provide a preparation method of the graphite ablation-resistant composite coating with shorter preparation time, higher uniformity and larger thickness. Technical proposal The graphite ablation-resistant composite coating is arranged on the surface of a graphite substrate, and the surface of the graphite substrate is sequentially provided with a SiC compact transition and sealing layer, a ZrC porous heat insulation and strain tolerance layer and an HfC-TaC compact ultrahigh temperature ablation coating from inside to outside, wherein the linear expansion coefficients of the SiC compact transition and sealing layer, the ZrC porous heat insulation and strain tolerance layer and the HfC-TaC compact ultrahigh temperature ablation coating gradually decrease from outside to inside. Further, the thickness of the SiC compact transition and sealing layer is 3-4 mu m, the thickness of the ZrC porous heat insulation and strain tolerance layer is 4.5-8 mu m, and the thickness of the HfC-TaC compact ultra-high temperature ablation coating is 21-24 mu m. Further, in the HfC-TaC dense ultra-high temperature ablative coating, the molar ratio of HfC-TaC is 1:1-1:3. The preparation method of the ablation-resistant composite coating of the cylindrical graphite comprises the following steps: Step one, performing plasma activation pretreatment on the surface of a graphite substrate; Step two, generating a SiC compact transition and sealing layer on the surface of the graphite matrix pretreated by the three-time reaction infiltration method; step three, coating slurry on the surface of the SiC compact transition and sealing layer to deposit a ZrC porous heat insulation and strain tolerance layer; And fourthly, preparing the HfC-TaC compact ultrahigh-temperature ablative coating on the surface of the ZrC porous heat insulation and strain tolerance layer by using a plasma spraying method. Further, in the first st