WO2019109752A1 - 一种钨铼热电偶高温抗氧化涂层及其应用 - Google Patents

一种钨铼热电偶高温抗氧化涂层及其应用 Download PDF

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WO2019109752A1
WO2019109752A1 PCT/CN2018/112015 CN2018112015W WO2019109752A1 WO 2019109752 A1 WO2019109752 A1 WO 2019109752A1 CN 2018112015 W CN2018112015 W CN 2018112015W WO 2019109752 A1 WO2019109752 A1 WO 2019109752A1
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layer
tungsten
oxygen barrier
barrier layer
thermocouple
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PCT/CN2018/112015
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English (en)
French (fr)
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陈实
邱新潮
徐健博
张博文
杨晓非
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华中科技大学
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
    • C23C28/042—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
    • C23C28/048—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material with layers graded in composition or physical properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples

Definitions

  • the invention belongs to the technical field of temperature measurement, and more particularly to a tungsten-rhenium thermocouple high-temperature oxidation resistant coating and its application.
  • thermocouples For the measurement of ultra-high temperature above 1600 °C, non-contact (infrared, optical, etc.) methods are often used for measurement, but the non-contact method not only has a slow response speed, but also the temperature measurement accuracy is far less than the direct contact type temperature measurement using a thermocouple.
  • Platinum rhodium (Pt-Rh) thermocouples, nickel-chromium-nickel silicon thermocouples, iron-constantan thermocouples and tungsten-rhenium (W-Re) thermocouples are common types of high-temperature thermocouples, among which tungsten-rhodium thermocouples Compared with other thermocouples, it has obvious advantages:
  • the temperature measurement range is large, and the upper limit of the working temperature can reach 2800 ° C;
  • the tungsten-rhenium thermocouple starts to oxidize from about 300 ° C in an aerobic environment, and is only suitable for high-temperature measurement in environments such as reduction, inertness, and vacuum, and cannot be applied in a high-temperature oxidizing atmosphere. Therefore, how to improve the anti-oxidation ability of tungsten-rhenium thermocouples has been a topic of high concern in the field of high-temperature measurement at home and abroad.
  • the temperature is measured by a tungsten-rhenium thermocouple in an aerobic environment.
  • two methods are used: one is for one-time measurement, that is, each temperature measurement time is short, and the thermocouple is no longer used or reprocessed after oxidation failure. After use, another way is to take anti-oxidation treatment on the thermocouple.
  • the commercial tungsten-tungsten thermocouple anti-oxidation technology is mainly an armored protection method, that is, quartz, corundum, refractory metal and high-temperature ceramics are used as protective tubes, and after being filled into a tungsten-rhenium thermocouple, the air-sealed seal is filled with an inert gas seal or Filled with an inert powder seal, creating a non-oxidizing atmosphere for the thermocouple in the protective tube to complete the temperature measurement mission before oxidation damage, but this non-removable solid anti-oxidation thermocouple has the following problems:
  • thermocouple is limited by the temperature resistance of the protective tube, usually less than 1800 ° C;
  • thermocouple After the protection of the casing and the filling material, the response speed of the thermocouple is greatly affected.
  • thermocouple By coating the surface of the tungsten-rhenium thermocouple with an anti-oxidation coating, the upper limit of temperature measurement and the extended temperature measurement time of the thermocouple in high-temperature air and other high-temperature oxidizing atmospheres are improved without affecting the response speed, which solves the above problems.
  • the ideal method In fact, research at home and abroad has been carried out since the 1960s, but there has been no continuous public reporting, and no relevant products have been put into practical use on a global scale.
  • the invention is based on a novel high-temperature anti-oxidation coating structure for the surface of a tungsten-rhenium thermocouple, so that it can realize long-time contact temperature measurement under an ultra-high temperature aerobic environment above 2000 °C.
  • the present invention provides a tungsten-rhenium thermocouple high-temperature oxidation resistant coating and an application thereof, the object of which is to directly prepare an anti-oxidation coating on the surface of a tungsten-rhenium thermocouple substrate, the anti-oxidation coating
  • the oxidized coating comprises a transition layer directly attached to the surface of the tungsten-rhodium thermocouple substrate and an oxygen barrier layer on the surface of the transition layer, the thermal expansion coefficient of the transition layer material being between the tungsten-rhenium thermocouple base material and the oxygen barrier layer
  • the coating can work continuously for more than 30 minutes in an aerobic environment above 2000 °C without falling off, and the oxidation resistance is excellent, thereby solving the long-term contact temperature measurement in the ultra-high temperature aerobic environment above 2000 °C.
  • the problem is to work continuously for more than 30 minutes in an aerobic environment above 2000 °C without falling off, and the oxidation resistance is excellent, thereby solving the long-term contact temperature measurement in the ultra-high temperature aerobic environment above 2000
  • a tungsten-rhenium thermocouple oxidation resistant coating characterized in that the oxidation resistant coating comprises a transition layer and an oxygen barrier layer on the surface of the transition layer.
  • the coefficient of thermal expansion of the transition layer material is between the tungsten-rhenium thermocouple matrix material and the material selected for the oxygen barrier layer.
  • the material selected for the transition layer does not react with the tungsten-rhenium thermocouple substrate above 2000 ° C, and the tungsten-rhenium thermocouple substrate, the transition layer and the oxygen barrier layer are intermediate layers and layers.
  • the absolute value of the difference between the coefficients of thermal expansion does not exceed 3 ⁇ 10 -6 K -1 .
  • the material selected for the transition layer is selected from one or more of titanium nitride, tungsten carbide, tantalum, tantalum carbide, tungsten silicide and magnesium oxide.
  • the transition layer is a film layer of 10 to 100 microns.
  • the transition layer is a film layer of 10 to 50 microns.
  • the oxygen barrier layer is a multi-layer structure of not less than 2 layers, and a coefficient of thermal expansion of each layer of the oxygen barrier layer gradually increases away from a direction of the tungsten-rhenium thermocouple substrate, the oxygen barrier material
  • the absolute value of the difference between the thermal expansion coefficient of the outermost layer and the thermal expansion coefficient of the substrate is not more than 7 ⁇ 10 -6 K -1 , and the oxygen ablation resistance of each layer of the material in the oxygen barrier layer is away from the tungsten-rhenium thermoelectricity.
  • the orientation of the even substrate is also gradually increased.
  • the oxygen barrier layer has a total thickness of no greater than 200 microns.
  • the material selected for the oxygen barrier layer is a refractory metal oxide, a boride or a nitride capable of functioning as an oxygen barrier or an oxygen ablation at 2000 ° C or higher.
  • the material selected for the oxygen barrier layer is one or more of silicon oxide, hafnium oxide, tantalum boride, tantalum nitride, zirconium oxide, zirconium boride, zirconium nitride and hafnium oxide.
  • the oxygen barrier layer of the multilayer structure has a composition gradient or a concentration gradient, that is, each layer of the multilayer structure of the oxygen barrier layer adopts different material species to form a composition gradient; or each layer has the same material type And at least a mixture of two materials, but the ratio of materials in each layer is different to form a concentration gradient.
  • the oxygen barrier layer has a multilayer structure of 5 to 10 layers.
  • the anti-oxidation coating described as an anti-oxidation coating for a tungsten-rhenium thermocouple attached to a surface of a tungsten-rhodium thermocouple substrate is provided.
  • the transition layer is prepared on the surface of the tungsten-rhodium thermocouple substrate by magnetron sputtering, thermal spraying, chemical vapor deposition or embedding;
  • the oxygen barrier layer is prepared on the surface of the transition layer by a chemical vapor deposition method, a thermal spray method or a sol-gel method.
  • the tungsten-rhenium thermocouple anti-oxidation coating proposed by the present invention is attached to the surface of the tungsten-rhenium thermocouple substrate and directly contacts the surface of the tungsten-rhenium thermocouple substrate, and the total thickness is within 300 micrometers.
  • the experiment proves that the anti-oxidation coating of the tungsten-rhenium thermocouple can continue to work for more than 30 minutes at 2000 °C without falling off, the anti-oxidation time is long and the temperature response speed is fast.
  • the anti-oxidation coating structure proposed by the present invention comprises an oxygen barrier layer having a multilayer structure, and the oxygen barrier layer in the multilayer structure has a composition gradient and a concentration gradient, that is, by adjusting each layer material type or material.
  • the ratio of the difference between the thermal expansion coefficient of the oxygen barrier layer formed on the tungsten barrier thermocouple substrate and the thermal expansion coefficient of the matrix is not more than 6 ⁇ 10 -6 K -1 , and is in the oxygen barrier layer.
  • the thermal expansion coefficient of each layer material gradually increases away from the tungsten-rhenium thermocouple matrix, and the oxygen-resistant ablation ability of each layer material in the oxygen barrier layer gradually increases away from the tungsten-rhenium thermocouple matrix.
  • the difference in the original thermal expansion coefficient is dispersed in a gradual manner between the layers by the composition gradient or the concentration gradient, so that the thermal expansion coefficient is from the inside out. Slowly increasing, effectively reducing the thermal stress of the high temperature oxidation resistant coating of the tungsten-rhenium thermocouple, and increasing the adhesion of the high temperature anti-oxidation coating of the tungsten-rhenium thermocouple.
  • the tungsten-rhenium thermocouple oxidation-resistant coating provided by the invention is further provided with a transition layer between the tungsten-rhenium thermocouple substrate and the oxygen barrier layer of the multilayer structure, and the transition layer is directly located on the surface of the tungsten-rhenium thermocouple wire, and the thickness is 10-100 micron, the transition layer is further provided to greatly improve the adhesion of the tungsten-rhenium thermocouple surface coating; the thermal expansion coefficient of the transition layer material is between the tungsten-rhenium thermocouple substrate and the oxygen barrier layer material, and the coating is at a high temperature The thermal stress underneath is greatly reduced.
  • the transition layer in the anti-oxidation coating structure of the tungsten-rhenium thermocouple of the present invention and the oxygen barrier layer of the multi-layer structure, material selection is essential, when different materials are used to realize multi-layer structure oxygen barrier with concentration gradient or composition gradient In the layer, not only the thermal expansion coefficient is increased, but also the stress is well dispersed. At the same time, the oxygen barrier layer of the same material is obtained at the same thickness, and the oxygen-resistant ablation ability, that is, the antioxidant capacity is greatly enhanced, indicating different components.
  • the oxygen barrier material of the kind or the oxygen barrier material between the layers exerts a synergistic promoting effect, enhances the oxidation resistance of the overall antioxidant coating, and provides a strong guarantee for the coating to work continuously for more than 30 minutes at 2000 ° C or higher. .
  • the present invention intelligently designs the multilayer structure of the oxygen barrier layer by selecting a specific oxygen barrier layer material and the material type of the transition layer, and sets a composition gradient or a concentration gradient between the layers, through a unique design concept and The careful selection of the material types, combined with the specific preparation process and parameter selection, finally obtained a tungsten-rhenium thermocouple high-temperature anti-oxidation coating, which can resist oxidation for more than 30 min at 2000 °C, oxidation resistance and thermocouple response speed. Both are far superior to prior art thermocouple oxidation coatings.
  • FIG. 1 is a schematic cross-sectional view showing an oxygen barrier material of a tungsten-rhenium thermocouple oxidation-resistant coating, that is, a tungsten-rhenium thermocouple substrate-transition layer-multilayer structure;
  • thermoelectric potential is a graph showing the change of the thermoelectric potential with the ablation time after the annealing of the oxidation resistant coating prepared in Example 1 of the present invention by annealing at 1000 ° C with an oxyacetylene flame of 2300 ° C or higher;
  • Example 3 is a SEM photograph of the oxidation resistant coating prepared in Example 2 of the present invention after ablation for 10 minutes by an oxyacetylene flame at 2300 ° C;
  • Figure 4 is an external view of an oxidation resistant coating prepared in Example 3 of the present invention.
  • Figure 5 is a SEM photograph of an oxidation resistant coating prepared in Example 3 of the present invention after ablation for 35 minutes with an oxyacetylene flame at 2500 °C.
  • the present invention provides a tungsten-rhenium thermocouple high-temperature oxidation-resistant coating.
  • the anti-oxidation coating proposed by the present invention comprises a transition layer directly attached to the surface of the tungsten-rhenium thermocouple substrate and attached to the transition.
  • the oxygen barrier layer on the surface of the layer, the thermal expansion coefficient of the transition layer material is between the material of the tungsten-rhenium thermocouple base material and the oxygen barrier layer, and the anti-oxidation coating continuously works for more than 30 minutes in an aerobic environment above 2000 ° C. Fall off.
  • the material selected for the transition layer does not react with the tungsten-rhenium thermocouple substrate above 2000 ° C, and the absolute value of the difference between the thermal expansion coefficients of the tungsten-rhenium thermocouple substrate, the transition layer and the oxygen barrier layer and the layer does not exceed 3 ⁇ 10 -6 K -1 .
  • the thermal expansion coefficient of the tungsten-rhenium alloy matrix is the smallest, and the thermal expansion coefficient increases from the inside to the outside.
  • the transition layer is selected from the group consisting of titanium nitride, tungsten carbide, tantalum, tantalum carbide, tungsten silicide or magnesium oxide.
  • the transition layer is a film layer of 10 to 100 microns, preferably 10 to 50 microns.
  • the oxygen barrier layer is a multi-layer structure of not less than 2 layers, and the thermal expansion coefficient of each layer of the oxygen barrier layer gradually increases away from the tungsten-rhenium thermocouple matrix, and the oxygen-resistant ablation ability of each layer material in the oxygen barrier layer is The direction away from the tungsten-rhodium thermocouple substrate is also gradually increased, and it is preferred that the total thickness of the oxygen barrier layer is within 200 ⁇ m.
  • the material selected for the oxygen barrier layer is a refractory metal oxide, a boride or a nitride which can function as an oxygen barrier or an oxygen ablation at 2000 ° C or higher.
  • the oxygen barrier layer is one or more of silicon oxide, hafnium oxide, tantalum boride, tantalum nitride, zirconium oxide, zirconium boride, zirconium nitride, and hafnium oxide.
  • the oxygen barrier layer of the multilayer structure has a composition gradient or a concentration gradient, that is, each layer of the multilayer structure of the oxygen barrier material adopts different material types; or each layer has the same kind of material and at least a mixture of two materials, but each The ratio of materials in the layers is different.
  • the number of layers of the oxygen barrier material is preferably 5 to 10 layers, and may be 5 layers or less or 10 or more layers as needed.
  • the above anti-oxidation coating is used as an anti-oxidation coating for a tungsten-rhenium thermocouple, the transition layer in the anti-oxidation coating structure and the oxygen barrier layer of the multi-layer structure, material selection is essential, and when different materials are used to achieve concentration Gradient or composition gradient multi-layer structure oxygen barrier layer not only satisfies the problem of increasing thermal expansion coefficient and achieving good stress dispersion, but also achieves oxygen barrier layer and oxygen-resistant ablation ability of the same material at the same thickness. That is to say, the antioxidant capacity is greatly enhanced, indicating that the oxygen barrier material of different component types or the oxygen barrier material between the layers exerts a synergistic promoting effect, and enhances the oxidation resistance of the overall antioxidant coating, achieving 2000 ° C for the coating.
  • the above continuous work for more than 30 minutes provides a strong guarantee.
  • thermocouple anti-oxidation coating comprises the following steps:
  • thermocouple substrate grinding the thermocouple substrate with sandpaper
  • purification treatment Using concentrated sodium hydroxide, concentrated sulfuric acid, ethanol to ultrasonically clean the substrate for 10 minutes to remove the substrate
  • Surface oil stains and other chemicals that may affect the spraying effect obtaining a tungsten-rhenium thermocouple substrate after surface roughening and purification
  • transition layer having a thickness of 10 to 100 ⁇ m on the surface of the roughened and purified tungsten-rhenium thermocouple substrate obtained in the step (1); the transition layer is subjected to magnetron sputtering, thermal spraying, and chemistry Prepared by vapor deposition or embedding.
  • the material selected for the transition layer does not react with the tungsten-rhenium thermocouple substrate above 2000 ° C, and the absolute value of the difference between the thermal expansion coefficients of the tungsten-rhenium thermocouple substrate, the transition layer and the oxygen barrier layer and the layer does not exceed 3 ⁇ 10 -6 K -1 , the thermal expansion coefficient of the transition layer material is between the tungsten-rhenium thermocouple base material and the material selected for the oxygen barrier layer;
  • step (3) sequentially change the material type of each layer, or the material type is not replaced, gradually adjust the concentration ratio of different materials in each layer, and deposit layer by layer in the same direction away from the tungsten-rhenium thermocouple substrate in the same way as in step (3). So that the thermal expansion coefficient of each layer of the oxygen barrier layer of the prepared multilayer structure is gradually increased away from the tungsten-rhenium thermocouple substrate, and the oxygen-resistant ablation ability of each layer of the oxygen barrier layer is far away. The direction of the tungsten-rhodium thermocouple substrate is also gradually increased; the total thickness of the oxygen barrier layer deposited layer by layer is 50-200 ⁇ m.
  • Magnetron sputtering is generally used to make films with a film thickness of 2 ⁇ m or less, while thermal spraying, chemical vapor deposition, and embedding are used to make thicker films.
  • the transition layer in the preparation of the tungsten-rhenium thermocouple high-temperature anti-oxidation coating of the present invention can be firstly formed into a film having a thickness of about 2 ⁇ m by magnetron sputtering, and then the remaining thickness can be made by chemical vapor deposition; or can be directly used.
  • the transition layer is prepared by embedding or directly by thermal spraying.
  • the silicon carbide film can be prepared by magnetron sputtering a silicon carbide film on a tungsten-rhenium thermocouple substrate with a silicon carbide target.
  • Methane and silane Si/C is about 1 are used as the reaction gas phase, and hydrogen is used as the carrier.
  • the thicker silicon carbide film is formed by chemical vapor deposition at a temperature of about 1350 °C, and the total thickness is controlled within 10 to 100 ⁇ m.
  • the preparation method may be as follows: silicon, sodium fluoride and silicon carbide are used as reaction raw materials, and the ratio is about 20%: 5%: 75%. After uniformly mixing, the tungsten-rhenium matrix is embedded and kept at about 1100 ° C for 0.5 to 2 hours. The longer the holding time, the thicker the transition layer.
  • the preparation method may be: using tungsten carbide powder as a reaction raw material, and performing thermal spraying on the surface of the tungsten-rhenium substrate by ultra-high temperature atomizing device after smelting at 3000 ° C. Control the flow to make the coating uniform and dense.
  • the tungsten-rhenium thermocouple high-temperature oxidation resistant coating of the present invention can deposit an oxygen barrier layer material on the outer layer of the transition layer by plasma enhanced chemical vapor deposition, or spray the oxygen barrier layer material on the outer layer of the transition layer by plasma spraying, or The sol-gel method condenses the oxygen barrier material on the outer layer of the transition layer.
  • An oxygen barrier layer material is deposited on the outer layer of the transition layer by plasma enhanced chemical vapor deposition.
  • silica silane and nitrous oxide are used as the reaction gas phase in a reaction gas phase, and nitrogen gas (ratio 1) is used as a carrier, and plasma enhanced at a temperature of about 300 ° C and a pressure of about 850 mTorr.
  • the chemical vapor deposition method deposits silicon dioxide on the outer layer of the transition layer at a deposition rate of about 3 ⁇ m/h for several hours to a thickness of 50 to 200 ⁇ m.
  • the oxygen barrier material is sprayed on the outer layer of the transition layer by plasma spraying.
  • the zirconium carbide powder is refined by ball milling, and then the spraying distance is controlled by a plasma spraying machine to be 150 mm, the spraying power is 30 kW, the powder feeding rate is 3 kg/h, and the zirconium carbide coated powder is sprayed.
  • the thickness is between 50 ⁇ m and 200 ⁇ m.
  • the oxygen barrier layer material is condensed on the outer layer of the transition layer by a sol-gel method.
  • cerium oxide as an oxygen barrier layer, an cerium sol is prepared by first using cerium oxychloride octahydrate (10-20 wt%), polyethylene glycol 4000 (10-20 wt%), and deionized water (60-80 wt%). Then, the pH value of the sol is adjusted to 2 to 3 with ammonia water, and after aging for several days, the cerium oxide powder (10-40% of the sol mass) is mixed, and the suspension is uniformly stirred to form a suspension. Finally, the tungsten ruthenium thermoelectricity is lifted by a pulling machine.
  • the bismuth dioxide oxygen barrier layer can be obtained by even immersing-drawing-drying, circulating to a certain thickness (50 ⁇ m to 200 ⁇ m) and annealing at 600 to 800 ° C for 1 hour.
  • a tungsten-rhenium thermocouple high temperature oxidation resistant coating structure comprising a transition layer and an oxygen barrier layer.
  • the oxygen barrier material and the tungsten-rhenium thermocouple substrate that is, the surface of the tungsten-rhenium thermocouple wire having a diameter of about 0.5 mm, have a TaC transition layer having a thickness of about 20 ⁇ m. As shown in FIG.
  • the oxygen barrier layer has a total of seven layers, first The layer is HfC-10% ZrC material, the coefficient of thermal expansion is 6 ⁇ 10 -6 K -1 , the thickness is 20 ⁇ m; the second layer is HfC-30% ZrC material, the thickness is 20 ⁇ m; the third layer is HfC-50% ZrC, The thickness is 20 ⁇ m; the fourth layer is ZrC, the thermal expansion coefficient is 7.3 ⁇ 10 -6 K -1 , the thickness is 20 ⁇ m; the fifth layer is ZrC-10% ZrO2, the thickness is 20 ⁇ m; the sixth layer is ZrC-30ZrO2, and the thickness is 20 ⁇ m; the seventh layer is ZrC-50ZrO2 and has a thickness of 20 ⁇ m.
  • the multi-layered oxygen barrier material has a total thickness of 140 micrometers, and its thermal expansion coefficient and oxygen ablation resistance gradually increase away from the tungsten-rhenium thermocouple matrix.
  • the preparation method of the transition layer in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • the Ta powder was added to a plastic container containing a solution of HF (concentration: about 40%) in a closed chamber having a venting apparatus and heated in a water bath of about 80 ° C, wherein the mass ratio of HF acid to Ta powder was about 1.5. During the experiment, the Ta powder was quickly dissolved and gas was emitted. After completion of the reaction, the TaF5 solution was filtered, and dried in an oven at 120 ° C to obtain a white powder. The white powder and the graphite powder were mixed in a 1:1 mass ratio, and the tungsten twisted wire was wrapped, and then placed in an Ar protective atmosphere furnace for high-temperature heat treatment at 1800 ° C for about 1 h, and the heating rate was 10 ° C / min.
  • HF concentration: about 40%
  • the preparation method of the oxygen barrier material in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • the cerium carbide, zirconium carbide and zirconia powder are refined by ball milling, and their mass ratios are adjusted according to the above-mentioned components, and then the spraying distance is controlled by a plasma spraying machine to be 150 mm, the spraying power is 30 kW, and the powder feeding rate is 3 kg/h.
  • a coated powder of a%HfC-b%ZrC-c%ZrO2 having a different composition ratio was sprayed on the outer layer of the transition layer, and seven layers of a tungsten-rhenium thermocouple oxygen barrier layer having a composition gradient were sequentially prepared. Finally, annealing treatment was performed at 1000 ° C for 1 hour.
  • thermoelectric potential with ablation time. It can be seen that there is still a thermoelectromotive force at 850 s, indicating that tungsten ruthenium is present.
  • the thermocouple is not damaged and still works normally, and the anti-oxidation coating has a significant protective effect.
  • a tungsten-rhenium thermocouple high temperature oxidation resistant coating structure comprising a transition layer and an oxygen barrier layer.
  • the oxygen barrier material and the tungsten-rhenium thermocouple substrate that is, the surface of the tungsten-rhenium thermocouple wire having a diameter of about 0.5 mm, have a Ta transition layer having a thickness of about 15 ⁇ m.
  • the oxygen barrier layer has six layers.
  • the first layer is SiC material with a thermal expansion coefficient of 4.5 ⁇ 10 -6 K -1 and a thickness of 20 ⁇ m.
  • the second layer is SiC-20% HfC material with a thickness of 20 ⁇ m.
  • the third layer is SiC-40%HfC, thickness 20 ⁇ m; fourth layer is SiC-60%HfC, thickness 20 ⁇ m; fifth layer is SiC-80%HfC, thickness is 20 ⁇ m; sixth layer is HfC, thermal expansion coefficient is 6.7 ⁇ 10 -6 K -1 with a thickness of 20 ⁇ m.
  • the oxygen barrier material of the multilayer structure has a total thickness of 120 micrometers, and its thermal expansion coefficient and oxygen ablation resistance gradually increase toward the tungsten carbide thermocouple matrix.
  • the preparation method of the transition layer in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • the tungsten carbide powder is used as a reaction raw material, and after being smelted at 3000 ° C in an ultra-high temperature, the surface of the tungsten-rhenium substrate is thermally sprayed by an ultra-high temperature atomizing device to control the spraying distance of 150 mm, the spraying power is 30 kW, and the flow rate is controlled to make the coating uniform and dense.
  • the thickness is about 15 ⁇ m.
  • the preparation method of the oxygen barrier material in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • the coating composition adjusts the proportion of each gas source in the reaction gas phase, and a thin layer of multi-layer x% SiC-y%HfC with a compositional composition gradient can be obtained by low pressure chemical vapor deposition at a low pressure of about 850 mTorr and a high temperature of about 900 °C. The deposition rate is about 3 ⁇ m/h. Finally, annealing treatment was performed at 1000 ° C for 1 hour.
  • Figure 3 is a SEM photograph of the coating after ablation for 10 minutes at 2300 ° C oxyacetylene flame. It can be seen from Fig. 3 that the surface of the coating is cracked by a long time high temperature flame scouring, but no obvious through crack is observed.
  • a tungsten-rhenium thermocouple high temperature oxidation resistant coating structure comprising a transition layer and an oxygen barrier layer.
  • the oxygen barrier material and the tungsten-rhenium thermocouple substrate that is, the surface of the tungsten-rhenium thermocouple wire having a diameter of about 0.5 mm, have a WSi2 transition layer having a thickness of about 20 ⁇ m.
  • the preparation method of the transition layer in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • the infiltrated element powder, the filler, and the activator are weighed according to (25% by weight of (high-purity silicon powder), 70% by weight of (silicon carbide powder), and 5 wt% of (sodium fluoride powder), and are weighed according to the size of the corundum crucible. Quality of the osmotic agent.
  • the tungsten-rhenium alloy was buried in the corundum crucible containing the infiltrant, and the lid was closed.
  • the corundum crucible embedded with the tungsten-rhenium thermocouple was placed in a high-temperature furnace and treated at 1650 ° C for 1 h. In order to reliably prevent the oxidation of the infiltration agent and the alloy during the infiltration process and improve the quality of the infiltration layer, the infiltration process is protected by argon gas.
  • the preparation method of the oxygen barrier material in the tungsten-rhenium thermocouple oxidation-resistant coating structure is:
  • cerium sol is prepared by using cerium oxychloride octahydrate (10-20% by weight), polyethylene glycol 4000 (10-20% by weight) and deionized water (60-80% by weight), and then adjusting the pH of the sol with ammonia water to 2 ⁇ 3, after a few days of stabilization, take a certain amount of cerium oxide powder (10-40% of the mass of the sol) in the beaker, stir evenly to make a suspension, and then use a pulling machine to immerse the tungsten-rhodium thermocouple into the pull-pull
  • the first layer is obtained by drying-out; the same amount of sol is used, and the cerium oxide powder and the zirconia-6% molar cerium oxide powder (the total mass is 10-40% of the mass of the sol) are added to the sol at a mass ratio of 9:1.
  • Figure 5 is a SEM photograph of the coating after ablation for 35 minutes at 2500 ° C oxyacetylene flame. It can be seen from Fig. 5 that the surface of the coating is peeled off and cracked layer by layer due to long-time high-temperature flame scouring, but the morphology of the WRe thermocouple substrate remains basically intact.

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Abstract

一种钨铼热电偶高温抗氧化涂层，包括直接位于钨铼热电偶基体表面的过渡层以及位于过渡层表面的氧阻挡材料，过渡层材料的热膨胀系数介于钨铼热电偶基体材料与氧阻挡材料之间。还提供了一种抗氧化涂层的应用。

Description

一种钨铼热电偶高温抗氧化涂层及其应用 【技术领域】
本发明属于温度测量技术领域，更具体地，涉及一种钨铼热电偶高温抗氧化涂层及其应用。
【背景技术】
对于1600℃以上超高温度的测量，目前多采用非接触(红外、光学等)方法测量，但非接触方法不仅响应速度慢，而且测温精度远不如采用热电偶进行直接接触式测温。铂铑(Pt-Rh)热电偶、镍铬-镍硅热电偶、铁-康铜热电偶和钨铼(W-Re)热电偶是比较常见的几种高温热电偶，其中钨铼热电偶与其它热电偶相比，具有明显的优势：
(1)熔点高(>3000℃)，强度大，抗热震性好，化学性质稳定；
(2)热电动势大(约为铂铑热电偶的2～3倍)，灵敏度高；
(3)测温范围大，工作温度上限可达2800℃；
(4)价格便宜(约为铂铑热电偶的十分之一)。
然而，钨铼热电偶在有氧环境下从300℃左右即开始氧化，只适用于还原、惰性、真空等环境的高温测量，不能在高温氧化性气氛中应用。因此，如何提高钨铼热电偶抗氧化能力，一直是国内外高温测量领域高度关注的课题。
目前在有氧环境下使用钨铼热电偶测温，一般采取两种方式：一种是一次性测量使用，即每次测温时间很短，热电偶氧化失效后即不再使用或重新处理加工后使用，另一种方式是对热电偶采取抗氧化处理。目前商业化的钨铼热电偶防氧化技术主要为铠装保护法，即采用石英、刚玉、难熔金属以及高温陶瓷等作为保护管，装入钨铼热电偶后抽空密封、充惰性气体密封或充填惰性粉体密封，在保护管内为热电偶人为创造出非氧化性气 氛，使其在氧化蚀损前完成测温使命，但这种不可拆卸的实体型抗氧化热电偶，存在以下问题：
(1)热电偶使用温度受保护管耐温能力的限制，通常低于1800℃；
(2)热电偶铠装保护后体积和重量增大，在体积要求比较严格的系统中使用受到限制；
(3)采用套管和填充物质保护后，热电偶的响应速度受到很大影响。
通过在钨铼热电偶表面涂覆抗氧化涂层，在不影响响应速度的前提下，提高热电偶在高温空气及其它高温氧化气氛中的测温上限、延长测温工作时间，是解决以上问题的比较理想的方法。实际上，国内外这方面的研究从上世纪六十年代起就已开展，但始终未见持续性的公开报道，而且全球范围内至今没有相关产品投入实际使用。
本发明基于一种新型的用于钨铼热电偶表面的高温抗氧化涂层结构，使之能实现2000℃以上超高温有氧环境下的长时间接触式测温。
发明内容
针对现有技术的以上缺陷或改进需求，本发明提供了一种钨铼热电偶高温抗氧化涂层及其应用，其目的在于通过在钨铼热电偶基体表面直接制备抗氧化涂层，该抗氧化涂层包括直接附着于钨铼热电偶基体表面的过渡层以及位于所述过渡层表面的氧阻挡层，过渡层材料的热膨胀系数介于所述钨铼热电偶基体材料与所述氧阻挡层选用的材料之间，该涂层在高于2000℃有氧环境中能够持续工作30min以上不脱落，而且抗氧化性能优异，由此解决2000℃以上超高温有氧环境中长时间接触式温度测量的问题。
为实现上述目的，按照本发明的一个方面，提供了一种钨铼热电偶抗氧化涂层，其特征在于，该抗氧化涂层包括过渡层以及位于所述过渡层表面的氧阻挡层，所述过渡层材料的热膨胀系数介于所述钨铼热电偶基体材料与所述氧阻挡层选用的材料之间。
优选地，所述过渡层选用的材料在2000℃以上不与所述钨铼热电偶基 体发生反应，且所述钨铼热电偶基体、所述过渡层与所述氧阻挡层三者中层与层之间的热膨胀系数之差的绝对值不超过3×10 -6K -1。
优选地，所述过渡层选用的材料选自氮化钛、碳化钨、钽、碳化钽、硅化钨和氧化镁中的一种或多种。
优选地，所述过渡层为10～100微米的薄膜层。
优选地，所述过渡层为10～50微米的薄膜层。
优选地，所述氧阻挡层为不低于2层的多层结构，所述氧阻挡层中各层材料热膨胀系数向远离所述钨铼热电偶基体的方向逐渐增大，所述氧阻挡材料最外层的热膨胀系数与所述基体热膨胀系数之差的绝对值不大于7×10 -6K -1，所述氧阻挡层中各层材料的耐氧烧蚀能力向远离所述钨铼热电偶基体的方向也逐渐增大。
优选地，所述氧阻挡层总厚度不大于200微米。
优选地，所述氧阻挡层选用的材料为在2000℃以上能起到氧阻挡或耐氧烧蚀作用的难熔金属氧化物、硼化物或氮化物。
优选地，所述氧阻挡层选用的材料为氧化硅、氧化铪、硼化铪、氮化铪、氧化锆、硼化锆、氮化锆和氧化钇中的一种或多种。
优选地，所述多层结构的氧阻挡层存在成分梯度或浓度梯度，即所述氧阻挡层的多层结构中每一层采用不同的材料种类以形成成分梯度；或者每一层材料种类相同且至少为两种材料的混合物，但是各层中材料的配比不同以形成浓度梯度。
优选地，所述氧阻挡层为5～10层的多层结构。
按照本发明的另一个方面，提供了一种所述的抗氧化涂层的应用，用作钨铼热电偶的抗氧化涂层，该抗氧化涂层附着于钨铼热电偶基体表面。
优选地，通过磁控溅射法、热喷涂法、化学气相沉积法或包埋法在所述钨铼热电偶基体表面制备得到所述过渡层；
优选地，通过化学气相沉积法、热喷涂法或溶胶凝胶法在所述过渡层 表面制备得到所述氧阻挡层。
总体而言，通过本发明所构思的以上技术方案与现有技术相比，能够取得下列有益效果：
(1)与传统的“铠装”不同，本发明提出的钨铼热电偶抗氧化涂层附着于钨铼热电偶基体表面，与钨铼热电偶基体表面直接相接触，总厚度为300微米以内，实验证明该钨铼热电偶抗氧化涂层在2000℃以上能够持续工作30min以上不脱落，抗氧化时间长且温度响应速度快。
(2)本发明提出的抗氧化涂层结构中包含有多层结构的氧阻挡层，该多层结构中的氧阻挡层存在成分梯度和浓度梯度，即通过调整每一层材料种类或材料之间的配比，使得形成的氧阻挡层在靠近钨铼热电偶基体的氧阻挡层材料热膨胀系数与基体热膨胀系数之差的绝对值不大于6×10 -6K -1，且氧阻挡层中各层材料热膨胀系数向远离钨铼热电偶基体的方向逐渐增大，氧阻挡层中各层材料的耐氧烧蚀能力向远离钨铼热电偶基体的方向也逐渐增大。这样，相比简单的钨铼基体与单一氧阻挡层的组合，它将原本热膨胀系数大的差异通过成分梯度或浓度梯度以渐变的形式分散到了层与层之间，使得热膨胀系数由内而外缓缓增大，有效减小了钨铼热电偶高温抗氧化涂层的热应力，同时增大了钨铼热电偶高温抗氧化涂层的附着力。
(3)本发明提出的钨铼热电偶抗氧化涂层在钨铼热电偶基体与多层结构的氧阻挡层之间还设置有过渡层，过渡层直接位于钨铼热电偶丝表面，厚度为10-100微米，设置过渡层进一步使得钨铼热电偶表面涂层的附着力得到很大提高；过渡层材料的热膨胀系数介于钨铼热电偶基体和氧阻挡层材料之间，涂层在高温下的热应力大大减小。
(4)本发明钨铼热电偶抗氧化涂层结构中的过渡层以及多层结构的氧阻挡层，材料选择至关重要，当采用不同材料实现具有浓度梯度或成分梯度的多层结构氧阻挡层时，不仅满足了热膨胀系数递增，实现应力良好分散的问题，同时也取得了在同等厚度下相比较同一种材料的氧阻挡层，耐 氧烧蚀能力即抗氧化能力大大增强，说明不同成分种类的氧阻挡材料或层与层之间的氧阻挡材料发挥了协同促进作用，增强了总体抗氧化涂层的抗氧化能力，为该涂层实现2000℃以上持续工作30分钟以上提供了有力保证。
(5)本发明通过选择特定的氧阻挡层材料以及过渡层的材料种类，巧妙设计氧阻挡层的多层结构，并设置层与层之间的成分梯度或浓度梯度，通过独特的设计构思与材料种类的精心选择，结合特定的制备工艺和参数选择，最终获得了一种钨铼热电偶高温抗氧化涂层，其能够在2000℃以上持续抗氧化30min以上，抗氧化性能以及热电偶响应速度均远远优于现有技术的热电偶抗氧化涂层。
附图说明
图1是本发明钨铼热电偶抗氧化涂层即钨铼热电偶基体-过渡层-多层结构的氧阻挡材料的截面结构示意图；
图2是本发明实施例1制得的抗氧化涂层经1000℃退火处理后，用2300℃以上氧乙炔焰进行烧蚀，其热电势随烧蚀时间的变化图；
图3是本发明实施例2制得的抗氧化涂层经2300℃氧乙炔焰烧蚀10分钟后的SEM照片；
图4本发明实施例3制得的抗氧化涂层的外观图；
图5是本发明实施例3制得的抗氧化涂层经2500℃氧乙炔焰烧蚀35分钟后的SEM照片。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
本发明提供了一种钨铼热电偶高温抗氧化涂层，与传统的“铠装”不同， 本发明提出的抗氧化涂层包括直接附着于钨铼热电偶基体表面的过渡层以及附着于过渡层表面的氧阻挡层，过渡层材料的热膨胀系数介于钨铼热电偶基体材料与氧阻挡层选用的材料之间，该抗氧化涂层在高于2000℃有氧环境中持续工作30min以上不脱落。过渡层选用的材料在2000℃以上不与所述钨铼热电偶基体发生反应，且钨铼热电偶基体、过渡层与氧阻挡层层与层之间的热膨胀系数之差的绝对值不超过3×10 -6K -1。一般钨铼合金基体热膨胀系数为最小，从内到外热膨胀系数依次增大。过渡层选自氮化钛、碳化钨、钽、碳化钽、硅化钨或氧化镁。过渡层为10～100微米的薄膜层，优选10～50微米。
氧阻挡层为不低于2层的多层结构，氧阻挡层中各层材料热膨胀系数向远离钨铼热电偶基体的方向逐渐增大，氧阻挡层中各层材料的耐氧烧蚀能力向远离所述钨铼热电偶基体的方向也逐渐增大，优选氧阻挡层总厚度为200微米以内。氧阻挡层选用的材料为在2000℃以上能起到氧阻挡或耐氧烧蚀作用的难熔金属氧化物、硼化物或氮化物。氧阻挡层为氧化硅、氧化铪、硼化铪、氮化铪、氧化锆、硼化锆、氮化锆和氧化钇中的一种或多种。多层结构的氧阻挡层存在成分梯度或浓度梯度，即氧阻挡材料的多层结构中每一层采用不同的材料种类；或者每一层材料种类相同且至少为两种材料的混合物，但是各层中材料的配比不同。优选的氧阻挡材料层数为5～10层，也可根据需要做到5层以下或10层以上。
将上述抗氧化涂层用作钨铼热电偶的抗氧化涂层，该抗氧化涂层结构中的过渡层以及多层结构的氧阻挡层，材料选择至关重要，当采用不同材料实现具有浓度梯度或成分梯度的多层结构氧阻挡层时，不仅满足了热膨胀系数递增，实现应力良好分散的问题，同时也取得了在同等厚度下相比较同一种材料的氧阻挡层，耐氧烧蚀能力即抗氧化能力大大增强，说明不同成分种类的氧阻挡材料或层与层之间的氧阻挡材料发挥了协同促进作用，增强了总体抗氧化涂层的抗氧化能力，为该涂层实现2000℃以上持续 工作30分钟以上提供了有力保证。
制备上述钨铼热电偶抗氧化涂层，包括如下步骤：
(1)对钨铼热电偶基体进行表面粗化(采用砂纸对热电偶基体进行打磨处理)和净化处理(分别用浓氢氧化钠、浓硫酸、乙醇对基体进行超声清洗10分钟，以去除基体表面油污及其他可能影响喷涂效果的化学物质)，得到表面粗化和净化后的钨铼热电偶基体；
(2)在步骤(1)获得的表面粗化和净化后的钨铼热电偶基体表面制备一层厚度为10～100微米的过渡层；过渡层通过磁控溅射法、热喷涂法、化学气相沉积法或包埋法制备得到。过渡层选用的材料在2000℃以上不与所述钨铼热电偶基体发生反应，且钨铼热电偶基体、过渡层与氧阻挡层层与层之间的热膨胀系数之差的绝对值不超过3×10 -6K -1，过渡层材料的热膨胀系数介于钨铼热电偶基体材料与所述氧阻挡层选用的材料之间；
(3)选择热膨胀系数与钨铼热电偶基体热膨胀系数之差的绝对值不大于5×10 -6K -1的材料或材料的混合物作为氧阻挡层材料，通过化学气相沉积法、热喷涂法或溶胶凝胶法在步骤(2)所述过渡层表面进行第一层氧阻挡层材料的制备；
(4)依次更换每一层材料种类，或材料种类不更换，逐渐调配每一层中不同材料的浓度配比，按照步骤(3)相同的方法向远离钨铼热电偶基体的方向逐层沉积，使得制备得到的多层结构的氧阻挡层中各层材料热膨胀系数向远离所述钨铼热电偶基体的方向逐渐增大，所述氧阻挡层中各层材料的耐氧烧蚀能力向远离所述钨铼热电偶基体的方向也逐渐增大；逐层沉积至氧阻挡层总厚度为50～200μm。
磁控溅射法一般用来做膜厚2μm以下的薄膜，而热喷涂法、化学气相沉积法及包埋法用来做更厚的薄膜。制备本发明钨铼热电偶高温抗氧化涂层中的过渡层可以先采用磁控溅射法做一层厚度为2μm左右的薄膜，然后利用化学气相沉积法做剩下的厚度；也可以直接用包埋法制备过渡层或者 直接用热喷涂法制备过渡层。
作为其中一种实施方案，当过渡层为碳化硅时，其制备方法可以为：先以碳化硅为靶材，在钨铼热电偶基底上磁控溅射一层2μm左右的碳化硅薄膜，然后以甲烷和硅烷(Si/C约为1)为反应气相，以氢气为载体，在1350℃左右温度下采用化学气相沉积法做更厚的碳化硅薄膜，总厚度控制在10～100μm以内。
作为其中一种实施方案，当过渡层为硅化钨时，其制备方法可以为：制备方法可以为：将硅、氟化钠和碳化硅作为反应原料，比例约为20％:5％:75％，均匀混合后把钨铼基体包埋在内，使其在1100℃左右保温0.5～2小时，保温时间越长，过渡层厚度越厚。
作为其中一种实施方案，当过渡层为碳化钨时，其制备方法可以为：将碳化钨粉末作为反应原料，经3000℃超高温熔炼后通过超高温雾化装置对钨铼基体表面进行热喷涂，控制流量，使涂层均匀而致密。
本发明钨铼热电偶高温抗氧化涂层可通过等离子体增强化学气相沉积法在过渡层外层沉积氧阻挡层材料，或用等离子喷涂法在过渡层外层喷涂氧阻挡层材料，也可采用溶胶凝胶法在过渡层外层凝结氧阻挡层材料。
采用等离子体增强化学气相沉积法在过渡层外层沉积氧阻挡层材料。以二氧化硅作氧阻挡层为例，将硅烷和一氧化二氮按1：2.5作为反应气相，以氮气(比例为1)为载体，在300℃左右温度、850mTorr左右压强下采用等离子体增强化学气相沉积法在过渡层外层沉积二氧化硅，沉积速率约为3μm/h，沉积数小时至厚度50～200μm。
采用等离子喷涂法在过渡层外层喷涂氧阻挡层材料。以碳化锆作氧阻挡层为例，先通过球磨对碳化锆粉末进行细化处理，然后通过等离子喷涂机控制喷涂距离150mm，喷涂功率30kW，送粉速率3kg/h，将碳化锆包覆粉末喷涂在过渡层外层，使其厚度在50μm～200μm之间。
采用溶胶凝胶法在过渡层外层凝结氧阻挡层材料。以氧化铪作氧阻挡 层为例，先用八水合氧氯化铪(10～20wt％)、聚乙二醇4000(10～20wt％)和去离子水(60～80wt％)制备铪溶胶，然后用氨水调节溶胶PH值为2～3，陈化数日稳定后掺入二氧化铪粉(溶胶质量的10～40％)，均匀搅拌制成悬浮液，最后采用提拉机将钨铼热电偶浸入-拉出-干燥，循环至一定厚度(50μm～200μm)后经600～800℃退火1小时即可制得二氧化铪氧阻挡层。
以下为实施例：
实施例1
一种钨铼热电偶高温抗氧化涂层结构，包括过渡层和氧阻挡层。氧阻挡材料与钨铼热电偶基体即直径约为0.5mm的钨铼热电偶丝表面之间有一层20μm左右厚度的TaC过渡层，如图1所示，氧阻挡层一共有七层，第一层为HfC-10％ZrC材料，热膨胀系数为6×10 -6K -1，厚度为20μm；第二层为HfC-30％ZrC材料，厚度为20μm；第三层为HfC-50％ZrC，厚度为20μm；第四层为ZrC，热膨胀系数为7.3×10 -6K -1，厚度为20μm；第五层为ZrC-10％ZrO2，厚度为20μm；第六层为ZrC-30ZrO2，厚度为20μm；第七层为ZrC-50ZrO2，厚度为20μm。该多层结构的氧阻挡材料总厚度为140微米，其热膨胀系数以及耐氧烧蚀能力向远离钨铼热电偶基体的方向均逐渐增大。
该钨铼热电偶抗氧化涂层结构中过渡层的制备方法为：
将Ta粉加入盛有HF(浓度约40％)溶液的塑料容器中于有排气设备的密闭仓内与80℃左右水浴加热，其中HF酸与Ta粉的质量比约为1.5。实验过程中Ta粉迅速溶解，同时有气体冒出。待反应完成后过滤得到TaF5溶液，将其置于120℃烘箱内干燥后得到白色粉末。将白色粉末、石墨粉按1:1质量比混合，包裹住钨铼丝，再置于Ar保护气氛炉中进行1800℃高温热处理1h左右，升温速率为10℃/min。
该钨铼热电偶抗氧化涂层结构中氧阻挡材料的制备方法为：
先通过球磨对碳化铪、碳化锆以及氧化锆粉末分别进行细化处理，按 照上述成分含量调整它们的质量比，然后通过等离子喷涂机控制喷涂距离150mm，喷涂功率30kW，送粉速率3kg/h，分别将具有不同成分占比的a％HfC-b％ZrC-c％ZrO2的包覆粉末喷涂在过渡层外层，依次制得七层具有成分梯度的钨铼热电偶氧阻挡层。最后在1000℃进行退火处理1小时。
制得的多层涂层经1000℃退火处理后，用2300℃以上氧乙炔焰进行烧蚀，图2是其热电势随烧蚀时间的变化，可见850s时仍有热电动势产生，说明钨铼热电偶未被破坏，仍能正常工作，抗氧化涂层的防护效果显著。
实施例2
一种钨铼热电偶高温抗氧化涂层结构，包括过渡层和氧阻挡层。氧阻挡材料与钨铼热电偶基体即直径约为0.5mm的钨铼热电偶丝表面之间有一层15μm左右厚度的Ta过渡层。氧阻挡层一共有六层，第一层为SiC材料，热膨胀系数为4.5×10 -6K -1，厚度为20μm；第二层为SiC-20％HfC材料，厚度为20μm；第三层为SiC-40％HfC，厚度为20μm；第四层为SiC-60％HfC，厚度为20μm；第五层为SiC-80％HfC，厚度为20μm；第六层为HfC，热膨胀系数为6.7×10 -6K -1，厚度为20μm。该多层结构的氧阻挡材料总厚度为120微米，其热膨胀系数以及耐氧烧蚀能力向远离钨铼热电偶基体的方向均逐渐增大。
该钨铼热电偶抗氧化涂层结构中过渡层的制备方法为：
将碳化钨粉末作为反应原料，经3000℃超高温熔炼后通过超高温雾化装置对钨铼基体表面进行热喷涂，控制喷涂距离150mm，喷涂功率为30kW，控制流量，使涂层均匀而致密，厚度约为15μm。
该钨铼热电偶抗氧化涂层结构中氧阻挡材料的制备方法为：
以氢气(流速约为750sccm)、甲基三氯硅烷(流速约为200sccm)和四氯化铪(流速约为100sccm)作为反应气相，以氩气为载体(流速约为350sccm)，按各层涂层成分调节反应气相中各气源的占比，在850mTorr左右低压、900℃左右高温下通过低压化学气相沉积的方法可以制得成分占 比渐变的多层x％SiC-y％HfC薄层，沉积速度约为3μm/h。最后在1000℃进行退火处理1小时。
图3为该涂层经2300℃氧乙炔焰烧蚀10分钟后的SEM照片。由图3可见，涂层表面经长时间高温火焰冲刷而出现开裂，但未见明显贯通裂纹。
实施例3
一种钨铼热电偶高温抗氧化涂层结构，包括过渡层和氧阻挡层。氧阻挡材料与钨铼热电偶基体即直径约为0.5mm的钨铼热电偶丝表面之间有一层20μm左右厚度的WSi2过渡层。氧阻挡层一共有十一层，第一层为HfO2材料，热膨胀系数为4.3×10 -6K -1，厚度为20μm；第二层为HfO2-10％YSZ(钇稳定氧化锆，摩尔比Y：Zr＝6：100)材料，厚度为20μm；第三层为HfO2-20％YSZ，厚度为20μm；第四层为HfO2-30％YSZ，厚度为20μm；第五层为HfO2-40％YSZ，厚度为20μm；第六层为HfO2-50％YSZ，厚度为20μm；第七层为HfO2-60％YSZ，厚度为20μm；第八层为HfO2-70％YSZ，厚度为20μm；第九层为HfO2-80％YSZ，厚度为20μm；第十层为HfO2-90％YSZ，厚度为20μm；第十一层为YSZ，热膨胀系数为11.5×10 -6K -1，厚度为20μm。该多层结构的氧阻挡材料总厚度为210微米，其热膨胀系数以及耐氧烧蚀能力向远离钨铼热电偶基体的方向均逐渐增大。
该钨铼热电偶抗氧化涂层结构中过渡层的制备方法为：
将渗入元素粉末、填充剂、活化剂按照(高纯硅粉)25wt％、(碳化硅粉末)70wt％、(氟化钠粉末)5wt％的比例称取，并根据刚玉坩埚的大小称取一定质量的渗剂。混合均匀后，将钨铼合金埋入装有渗剂的刚玉坩埚中，盖上盖子。将包埋好钨铼热电偶的刚玉坩埚置于高温炉中，进行1650℃高温处理1h。为了可靠的防止包渗过程中渗剂及合金的氧化，改善渗层质量，采用氩气保护包渗过程。
该钨铼热电偶抗氧化涂层结构中氧阻挡材料的制备方法为：
先用八水合氧氯化铪(10～20wt％)、聚乙二醇4000(10～20wt％)和 去离子水(60～80wt％)制备铪溶胶，然后用氨水调节溶胶PH值为2～3，陈化数日稳定后取一定量于烧杯中掺入二氧化铪粉(溶胶质量的10～40％)，均匀搅拌制成悬浮液，再采用提拉机将钨铼热电偶浸入-拉出-干燥制得第一层；取等量溶胶，将二氧化铪粉和氧化锆-6％摩尔氧化钇粉(总质量占溶胶质量的10～40％)按质量比9：1加入到溶胶中去，重复浸入-拉出-干燥步骤制得第二层；另取等量溶胶，将二氧化铪粉和氧化锆-6％摩尔氧化钇粉(总质量占溶胶质量的10～40％)按质量比8：2加入到溶胶中去，重复浸入-拉出-干燥步骤制得第三层；依次类推，制得十一层具有成分梯度的钨铼热电偶抗氧化涂层，其外观图如图4所示。最后在1000℃进行退火处理1小时。
图5为涂层经2500℃氧乙炔焰烧蚀35分钟后的SEM照片。由图5可见，涂层表面经长时间高温火焰冲刷而逐层剥离、开裂，但WRe热电偶基体形态基本保持完好。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种钨铼热电偶抗氧化涂层，其特征在于，所述抗氧化涂层包括过渡层以及位于所述过渡层表面的氧阻挡层，所述过渡层材料的热膨胀系数介于所述钨铼热电偶基体材料与所述氧阻挡层选用的材料之间。
  2. 如权利要求1所述的抗氧化涂层，其特征在于，所述过渡层选用的材料在2000℃以上不与所述钨铼热电偶基体发生反应，且所述钨铼热电偶基体、所述过渡层与所述氧阻挡层三者中任意两者之间的热膨胀系数之差的绝对值不超过3×10 -6K -1。
  3. 如权利要求1所述的抗氧化涂层，其特征在于，所述过渡层选用的材料选自氮化钛、碳化钨、钽、碳化钽、硅化钨和氧化镁中的一种或多种。
  4. 如权利要求1所述的抗氧化涂层，其特征在于，所述过渡层为10～100微米的薄膜层，优选10～50微米。
  5. 如权利要求1所述的抗氧化涂层，其特征在于，所述氧阻挡层为不低于2层的多层结构，所述氧阻挡层中各层材料热膨胀系数向远离所述钨铼热电偶基体的方向逐渐增大，所述氧阻挡材料最外层的热膨胀系数与所述基体热膨胀系数之差的绝对值不大于7×10 -6K -1，所述氧阻挡层中各层材料的耐氧烧蚀能力向远离所述钨铼热电偶基体的方向也逐渐增大。
  6. 如权利要求1所述的抗氧化涂层，其特征在于，所述氧阻挡层总厚度不大于200微米。
  7. 如权利要求1所述的抗氧化涂层，其特征在于，所述氧阻挡层选用的材料为在2000℃以上能起到氧阻挡或耐氧烧蚀作用的难熔金属氧化物、硼化物或氮化物；优选为氧化硅、氧化铪、硼化铪、氮化铪、氧化锆、硼化锆、氮化锆和氧化钇中的一种或多种。
  8. 如权利要求5所述的抗氧化涂层，其特征在于，所述多层结构的氧阻挡层存在成分梯度或浓度梯度，即所述氧阻挡层的多层结构中每一层采 用不同的材料种类以形成成分梯度；或者每一层材料种类相同且至少为两种材料的混合物，但是各层中材料的配比不同以形成浓度梯度。
  9. 如权利要求5所述的抗氧化涂层，其特征在于，所述氧阻挡层为5～10层的多层结构。
  10. 如权利要求1～9任意一项所述的抗氧化涂层的应用，其特征在于，用作钨铼热电偶的抗氧化涂层，该抗氧化涂层附着于所述钨铼热电偶基体表面。
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