Composite powder for thermal barrier coating, thermal barrier coating and preparation method

Abstract

The present invention belongs to the technical field of thermal barrier coatings, and specifically relates to a composite powder for thermal barrier coatings, a thermal barrier coating and a preparation method. The composite powder is a spherical powder with a hollow structure, and the composite powder includes a chemical formula of (Hf x ,Zr 1‑x )6Ta2O 17 The composite tantalate, wherein x is 0.2-0.8. The thermal barrier coating formed by the composite powder spraying has significantly reduced thermal conductivity and significantly improved high-temperature phase structure stability, and can significantly extend the life of the thermal barrier coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal barrier coatings. Specifically, it relates to a composite powder for thermal barrier coatings, a thermal barrier coating, and a preparation method thereof. Background Art

[0002] The development level of aero-engines is a concentrated reflection of a country's industrial foundation, scientific and technological level, and comprehensive national strength. Currently, the turbine inlet temperature of advanced aero-engines has approached 2000 °C, and the temperature reaching the surface of the turbine blades is 1400 °C. With the continuous development of engine technology and the continuous increase in the thrust-to-weight ratio, the service temperature will further increase, and the high-temperature-resistant thermal barrier coating on the surface of the turbine blades has become a bottleneck for improving the performance of aero-engines.

[0003] Currently, the existing thermal barrier coating materials are mainly yttria partially stabilized zirconia (YSZ). However, YSZ has a relatively high thermal conductivity, making it difficult to meet the heat insulation requirements of thermal barrier coatings. Moreover, when the use temperature exceeds 1200 °C, it is prone to phase transformation and sintering, resulting in coating failure.

[0004] It should be noted that this part of the content of the present invention only provides the background technology related to the present invention, and does not necessarily constitute the prior art or well-known technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the existing thermal barrier coating materials, such as relatively high thermal conductivity, difficulty in meeting the heat insulation requirements, limited high-temperature phase structure stability, and easy coating failure. The present invention provides a composite powder for thermal barrier coatings, a thermal barrier coating, and a preparation method thereof. The thermal barrier coating formed by spraying this composite powder has a significantly reduced thermal conductivity and a significantly improved high-temperature phase structure stability, and can significantly extend the service life of the thermal barrier coating.

[0006] To achieve the above purpose, in the first aspect, the present invention provides a composite powder for thermal barrier coatings. The composite powder is a spherical powder with a hollow structure, and the composite powder includes a composite tantalate with the chemical formula (Hf x ,Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 - 0.8.

[0007] In some preferred embodiments, the ratio of the inner diameter to the outer diameter of the composite powder is 0.25 - 0.7.

[0008] Preferably, the ratio of the inner diameter to the outer diameter of the composite powder is 0.4 - 0.6.

[0009] In the second aspect, the present invention provides a preparation method of the composite powder for thermal barrier coatings according to the first aspect, including: preparing a solution containing Zr 4+, Hf 4+ , Ta 5+ A composite salt solution of, add a precipitating agent to the composite salt solution to obtain a suspension, and perform plasma spheroidization on the suspension to obtain the composite powder for the thermal barrier coating;

[0010] In the composite salt solution, Zr 4+ , Hf 4+ and Ta 5+ have a molar ratio of 20 - 40:20 - 75:15 - 40. The solid dispersed phase in the suspension includes a composite tantalate with the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 - 0.8. The conditions for the plasma spheroidization include: the flame power is 40 kW - 50 kW, and the liquid feeding rate is 5 mL / min - 15 mL / min.

[0011] In some preferred embodiments, the flame power is 42 - 48 kW, and the liquid feeding rate is 5 mL / min - 10 mL / min.

[0012] Preferably, the conditions for the plasma spheroidization further include: the gas temperature for rapid cooling by the quenching gas is -15°C - 0°C, and the gas flow rate is 20 slpm - 30 slpm.

[0013] In some preferred embodiments, dissolve a mixture including ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 in water to prepare the composite salt solution; the precipitating agent is ammonia water.

[0014] In the third aspect, the present invention provides a method for preparing a thermal barrier coating. Using the composite powder for the thermal barrier coating described in the first aspect and / or the composite powder for the thermal barrier coating prepared by the preparation method described in the second aspect, perform atmospheric plasma spraying to obtain a thermal barrier coating.

[0015] In some preferred embodiments, the conditions for the atmospheric plasma spraying include: the spraying distance is 90 mm - 120 mm, the spraying power is 43 kw - 47 kw, the carrier gas flow rate is 2 slpm - 5 slpm, and the powder feeding rate is 10 g / min - 20 g / min;

[0016] and / or,

[0017] Before atmospheric plasma spraying the composite powder for thermal barrier coatings prepared by using the composite powder for thermal barrier coatings described in the first aspect and / or the preparation method described in the second aspect, an MCrAlY coating and a YSZ coating are sprayed in sequence.

[0018] Fourthly, the present invention provides a thermal barrier coating which is prepared by the preparation method described in the third aspect.

[0019] The composite powder of the present invention comprises a composite tantalate with the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 to 0.8, and Hf and Zr are doped in the lattice of Ta 2 O 5 , causing lattice distortion of the original Ta 2 O 5 lattice, resulting in long-range disorder and short-range order in the lattice structure within the powder body, reducing the mean free path of phonons, and thus significantly reducing the thermal conductivity of the coating formed by spraying the powder.

[0020] The composite powder of the present invention comprises a composite tantalate with the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 to 0.8. On the one hand, since the main body of the composite powder is tantalum and tantalum has a high melting point. On the other hand, Zr and Hf are doped in the tantalum system. Due to the mismatch between the ionic radii and atomic weights of Hf and Zr and tantalum, Hf and Zr atoms are randomly distributed in the tantalate system, which causes lattice distortion of the original lattice, and the formed phase structure is relatively stable and difficult to undergo a phase change under high-temperature conditions, significantly improving the high-temperature phase structure stability of the coating formed by spraying the powder and preventing the high-temperature failure of the coating. If ZrO 2 and / or HfO 2 are physically mixed with Ta 2 O 5 , since ZrO 2 and / or HfO 2 are prone to undergo a high-temperature phase change from the cubic phase to the monoclinic phase at 1100°C to 1200°C, causing volume expansion and easily leading to the failure of the thermal barrier coating. If only Zr is doped in the lattice of Ta 2 O 5 of the present invention, it will result in problems such as ineffective improvement of the phase structure stability, inability to reduce the thermal conductivity of the coating, poor fracture toughness of the coating, high brittleness of the coating, and low service life of the coating. If Ta 2 O 5Doping only Hf in the lattice will result in problems such as high coating thermal conductivity, poor heat insulation performance, and inability to effectively improve the phase structure stability. When x is less than 0.2, Zr dominates, and the coating cannot form a ferroelastic domain toughening structure, thus unable to effectively improve the coating fracture toughness. The phase structure stability formed by lattice distortion is limited and cannot effectively reduce the thermal conductivity of the coating. When x is greater than 0.8, Hf dominates, and the coating cannot form a large amount of lattice distortion, unable to effectively diffuse phonons, unable to effectively reduce the thermal conductivity and improve the heat insulation performance, and the phase structure stability is limited. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0022] Figure 1 Scanning electron microscope photograph of the composite powder for thermal barrier coating in Embodiment 1 of the present invention.

[0023] Figure 2 Scanning electron microscope photograph of the cross-section of the composite powder for thermal barrier coating in Embodiment 1 of the present invention.

[0024] Figure 3 Scanning electron microscope photograph of the thermal barrier coating in Embodiment 1 of the present invention.

[0025] Figure 4 Phase structure diagram of the thermal barrier coating in Embodiment 1.

[0026] Figure 5 Phase structure diagram of the thermal barrier coating in Embodiment 1 after high-temperature phase structure stability detection. Detailed Description of the Embodiments

[0027] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0028] The inventors of the present application have found through research that existing thermal barrier coating materials have high thermal conductivity, are difficult to meet the heat insulation requirements, have limited high-temperature phase structure stability, and the coating is prone to failure.

[0029] In this regard, in a first aspect, the present invention provides a composite powder for thermal barrier coating, wherein the composite powder is a spherical powder having a hollow structure, and the composite powder comprises a chemical formula of (Hf x ,Zr 1-x ) 6 Ta 2 O 17 complex tantalate, where x is 0.2~0.8.

[0030] The inventors found that thermal conductivity decreases with the increase of composition and lattice complexity. The oxide thermal barrier coating conducts heat through lattice vibration (phonon). The thermal conductivity is mainly determined by the free path of phonons. The free path of phonons can be reduced by doping with foreign ions. The average free path of phonons is inversely proportional to the mass difference between the replacing atom and the replaced atom and the square of the ionic radius difference. By introducing anion and cation vacancies and the mismatch between ionic radius and atomic weight through substitution, the introduction of such point defects and the manipulation of atomic arrangement can reduce thermal conductivity. The composite powder of the present invention includes a chemical formula of (Hf x ,Zr 1-x ) 6 Ta 2 O 17 complex tantalate, where x is 0.2~0.8, Ta 2 O 5 The lattice of is doped with Hf and Zr, which makes the original Ta 2 O 5 The lattice of the powder is distorted, resulting in long-range disorder and short-range order in the lattice structure of the powder, which reduces the free path of phonons and can significantly reduce the thermal conductivity of the coating formed by powder spraying.

[0031] The composite powder of the present invention includes a chemical formula of (Hf x ,Zr 1-x ) 6 Ta 2 O 17 composite tantalate, wherein x is 0.2~0.8. On the one hand, since the main body of the composite powder is tantalum, tantalum has a relatively high melting point. On the other hand, Zr and Hf are doped in the tantalum system. Due to the mismatch between the ionic radius and atomic weight of Hf and Zr and tantalum, Hf and Zr atoms are scattered in the tantalate system, which causes the original lattice to undergo lattice distortion. The formed phase structure is relatively stable and it is difficult to undergo phase change under high temperature conditions. Through the interaction of the above two aspects, the high-temperature phase structure stability of the coating formed by powder spraying can be significantly improved to prevent the coating from failing at high temperature. In the present invention, if ZrO 2 and / or HfO 2 With Ta 2 O 5 It is a physical mixture, because ZrO 2 and / or HfO2 It is prone to high-temperature phase transformation at 1100°C to 1200°C, changing from the cubic phase to the monoclinic phase, triggering volume expansion and easily leading to the failure of the thermal barrier coating. In the present invention, if Ta 2 O 5 is doped only with Zr in its lattice, it will result in problems such as being unable to effectively improve the phase structure stability, unable to reduce the thermal conductivity of the coating, poor fracture toughness of the coating, high brittleness of the coating, and low service life of the coating. If Ta 2 O 5 is doped only with Hf in its lattice, it will cause problems such as high thermal conductivity of the coating, poor heat insulation performance, and inability to effectively improve the phase structure stability. When x is less than 0.2, Zr dominates, and the coating cannot form a ferroelastic domain toughening structure, thus unable to effectively improve the fracture toughness of the coating. The phase structure stability formed by lattice distortion is limited and unable to effectively reduce the thermal conductivity of the coating. When x is greater than 0.8, Hf dominates, and the coating cannot form a large amount of lattice distortion, unable to effectively diffuse phonons, unable to effectively reduce the thermal conductivity and improve the heat insulation performance, and the phase structure stability is limited.

[0032] The composite powder of the present invention is a spherical powder with a hollow structure. The hollow structure can promote the melting of the powder during the spraying process, reduce the defects of unmelted powder inside the coating, inhibit the stacking of powders that have not been fully melted, and improve the bonding strength of the coating (the bonding between the unmelted powder and the substrate or other molten powders is mainly mechanical bonding rather than solid solution bonding or chemical bonding). The hollow structure can also, through the powder inheritance mechanism, that is, the internal organizational structure of the powder is retained in the internal organizational structure of the coating. Specifically, after the powder melts, there is still gas inside the melted powder. After the melted powder is stacked into the coating, the gas is difficult to escape, resulting in dispersed pores in the coating. The air inside the pores can be regarded as an adiabatic body compared to the coating. The coating has many and dispersed pores, which can further reduce the thermal conductivity of the coating and improve the heat insulation performance of the coating.

[0033] The strength of the composite powder of the present invention can reach 50 MPa to 150 MPa, the fluidity can reach 20 s - 45 s / 50 g, and the loose bulk density can reach 3.10 g / cm 3 ~3.30 g / cm 3 .

[0034] In some preferred embodiments, the ratio of the inner diameter to the outer diameter of the composite powder is 0.25 to 0.7. The ratio of the inner diameter to the outer diameter of the composite powder is not less than 0.25, which is more conducive to promoting the melting of the powder during the spraying process, reducing the defects of unmelted particles inside the coating, improving the bonding strength of the coating, forming dispersed pores in the coating, and reducing the thermal conductivity of the coating. The ratio of the inner diameter to the outer diameter of the composite powder is not greater than 0.7, which is more conducive to inhibiting gasification during the powder spraying process and affecting the coating preparation. The ratio of the inner diameter to the outer diameter of the composite powder refers to the average ratio.

[0035] Preferably, the ratio of the inner diameter to the outer diameter of the composite powder is 0.4 to 0.6. When the ratio of the inner diameter to the outer diameter of the composite powder is not less than 0.4, it is more conducive to promoting the melting of the powder during spraying, reducing the defect of unmelted particles inside the coating, improving the coating bonding strength, the dispersed pores in the coating, and reducing the thermal conductivity of the coating. When the ratio of the inner diameter to the outer diameter of the composite powder is not greater than 0.6, it is more conducive to suppressing gasification during powder spraying and affecting the coating preparation.

[0036] Second, the present invention provides a preparation method of the composite powder for the thermal barrier coating described in the first aspect, including: preparing a composite salt solution containing Zr 4+ , Hf 4+ , Ta 5+ , adding a precipitating agent to the composite salt solution to obtain a suspension, and performing plasma spheroidization on the suspension to obtain the composite powder for the thermal barrier coating;

[0037] In the composite salt solution, the molar ratio of Zr 4+ , Hf 4+ and Ta 5+ is 20 to 40:20 to 75:15 to 40. The solid dispersed phase in the suspension includes a composite tantalate with the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 to 0.8. The conditions for the plasma spheroidization include: the flame power is 40 kW to 50 kW, and the liquid feeding rate is 5 mL / min to 15 mL / min.

[0038] The composite salt solution of the present invention contains Zr 4+ , Hf 4+ and Ta 5+ . The molar ratio of Zr 4+ , Hf 4+ and Ta 5+ is 20 to 40:20 to 75:15 to 40. Adding a precipitating agent that can ionize OH - in the solution to the composite salt solution can form a solid dispersed phase including a composite tantalate with the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17A suspension of a composite tantalate, where x ranges from 0.2 to 0.8. During the plasma spheroidization process, under plasma spheroidization conditions with a flame power of 40 kW to 50 kW and a liquid feeding rate of 5 mL / min to 15 mL / min, the carrier gas feeds the suspension as the liquid feed into the high-temperature plasma. The dispersant (solvent) evaporates rapidly, and the solid dispersed phase rapidly absorbs heat. The heat conducts from the outer surface of the solid dispersed phase to the inside, and the solid dispersed phase melts from the outer surface to the inside. There are a large number of tiny pores inside the solid dispersed phase, and the internal gas is difficult to escape and is enclosed in the internal space. Under the action of surface tension, the molten solid dispersed phase particles condense into spherical droplets including (Hf x ,Zr 1-x ) 6 Ta 2 O 17 spherical droplets of the composite tantalate; then the spherical droplets containing pores inside enter the cooling chamber and are quenched rapidly. The shell layer of the spherical droplets cools, and spherical powder with a hollow structure including a composite tantalate with the chemical formula (Hf x ,Zr 1-x ) 6 Ta 2 O 17 can be formed.

[0039] The present invention does not limit the carrier gas for plasma spheroidization, such as argon, nitrogen, hydrogen, etc. The quenching of plasma spheroidization in the present invention preferably uses a quenching gas for rapid cooling, which is more conducive to forming spherical composite powder with a hollow structure.

[0040] In some preferred embodiments, the flame power is 42 - 48 kW, and the liquid feeding rate is 5 mL / min - 10 mL / min. The melting degree of the solid dispersed phase in the high-temperature flame progresses from the surface to the inside. When the flame power is higher and the liquid feeding rate is lower, the melting degree of the solid dispersed phase is higher, and the ratio of the inner diameter to the outer diameter of the composite powder is larger. When the flame power is lower and the liquid feeding rate is higher, the melting degree of the solid dispersed phase is lower, and the ratio of the inner diameter to the outer diameter of the composite powder is smaller. Under this preferred scheme, with a flame power of 42 - 48 kW and a liquid feeding rate of 5 mL / min - 10 mL / min, by controlling the total amount of heat absorbed by the solid dispersed phase in the high-temperature plasma and controlling the melting degree of the solid dispersed phase, the ratio of the inner diameter to the outer diameter of the composite powder can be made to be 0.25 - 0.7.

[0041] Preferably, the conditions for the plasma spheroidization further include: the gas temperature of the rapid cooling by the quenching gas is -15°C to 0°C, and the gas flow rate is 20 slpm to 30 slpm. On the premise that the flame power is 42 to 48 kW and the liquid feeding rate is 5 mL / min to 10 mL / min, when the gas temperature of the rapid cooling by the quenching gas is -15°C to 0°C and the gas flow rate is 20 slpm to 30 slpm, the ratio of the inner diameter to the outer diameter of the composite powder can be 0.4 to 0.6.

[0042] In some preferred embodiments, a mixture including ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 is dissolved in water to prepare the composite salt solution; the precipitant is ammonia water. Under this preferred scheme, an excessive amount of the precipitant is added to the solution, and ammonia water can decompose into ammonia gas at high temperature without impurity retention. Chloride ions and nitrate ions combine with ammonium ions, and they can decompose into gases when heated at a relatively high temperature and will not remain on the powder formed after plasma spheroidization, which can avoid the introduction of other impurities and is more conducive to the purification of the powder.

[0043] In a third aspect, the present invention provides a method for preparing a thermal barrier coating. Using the composite powder for thermal barrier coating described in the first aspect and / or the composite powder for thermal barrier coating prepared by the preparation method described in the second aspect, atmospheric plasma spraying is carried out to obtain a thermal barrier coating.

[0044] The present invention uses a composite tantalate including the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 to 0.8, and a hollow-structured spherical-like powder. By carrying out atmospheric plasma spraying, the obtained thermal barrier coating has a significantly reduced thermal conductivity, a significantly improved high-temperature phase structure stability and bonding strength, and the coating is not easily damaged. The thermal conductivity of the thermal barrier coating of the present invention is significantly reduced to 0.8 to 0.9 W / (m·K), the coating bonding strength is significantly increased to 25 MPa - 35 MPa, the thermal barrier coating has a longer service life than the conventional thermal barrier coating, can withstand a harsh high-temperature service environment, and in the 1400°C thermal shock assessment experiment, the service life reaches more than 2000 times.

[0045] In some preferred embodiments, the conditions for the atmospheric plasma spraying include: the spraying distance is 90 mm to 120 mm, the spraying power is 43 kw to 47 kw, the carrier gas flow rate is 2 slpm to 5 slpm, and the powder feeding rate is 10 g / min to 20 g / min;

[0046] and / or

[0047] Before atmospheric plasma spraying with the composite powder for thermal barrier coatings prepared by using the composite powder for thermal barrier coatings described in the first aspect and / or the preparation method described in the second aspect, an MCrAlY coating and a YSZ coating are sprayed in sequence.

[0048] Under this preferred scheme, based on the composite powder being a composite tantalate including the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 - 0.8, a hollow-structured spherical-like powder, spraying distance: 90 mm - 120 mm, spraying power is 43 kw - 47 kw, carrier gas flow rate is 2 slpm - 5 slpm, powder feeding rate is 10 g / min - 20 g / min. This spraying process is more conducive to improving the coating bonding strength while making the internal structure of the coating form a dispersed pore structure, reducing the coating thermal conductivity, thereby enhancing the coating heat insulation performance. The MCrAlY coating is used as the bottom layer, and the YSZ coating is used as the intermediate layer. Using a composite tantalate coating formed by spraying a composite tantalate including the chemical formula (Hf x , Zr 1-x ) 6 Ta 2 O 17 , where x is 0.2 - 0.8, a hollow-structured spherical-like powder as the surface layer is more conducive to reducing the brittleness of the thermal barrier coating and improving the coating service life. The YSZ coating refers to a yttria partially stabilized zirconia coating, and M in the MCrAlY coating refers to Ni and / or Co.

[0049] Before preparing the thermal barrier coating of the present invention, it is preferred to roughen the substrate so that the surface roughness of the substrate is Ra8 - 12 μm. The thickness of the MCrAlY bottom layer of the present invention is preferably 50 μm - 150 μm, the thickness of the intermediate YSZ coating is preferably 100 μm - 200 μm, and the thickness of the hafnium zirconium tantalate surface layer is preferably 100 μm - 200 μm.

[0050] In the fourth aspect, the present invention provides a thermal barrier coating prepared by the preparation method described in the third aspect. The thermal barrier coating of the present invention has a significantly reduced thermal conductivity, significantly improved high-temperature phase structure stability and bonding strength, and the coating is not easily failed.

[0051] The present invention will be further elaborated in detail below in conjunction with specific embodiments.

[0052] Example 1

[0053] A preparation method of a composite powder for thermal barrier coatings is as follows:

[0054] Step 1: Dissolve ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 in water to form a composite salt solution. The molar ratio of ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 is 30:30:20. The composite salt solution contains Zr 4+ , Hf 4 + , Ta 5+ . The molar ratio of Zr 4+ , Hf 4+ and Ta 5+ in the composite salt solution is 30:30:20. Add an ammonia precipitating agent to the composite salt solution to form a suspension. The solid dispersed phase in the suspension includes a composite tantalate with the chemical formula (Hf 1 / 2 ,Zr 1 / 2 ) 6 Ta 2 O 17 ;

[0055] Step 2: Perform plasma spheroidization on the suspension obtained in Step 1 to obtain a composite powder for thermal barrier coatings. The flame power of the plasma spheroidization is 45 kW, the liquid feeding rate is 8 mL / min, the gas temperature of the rapid cooling by the quenching gas is -10°C, and the gas flow rate is 25 slpm.

[0056] A composite powder for thermal barrier coatings, wherein the composite powder is a spherical powder with a hollow structure. The composite powder includes a composite tantalate with the chemical formula (Hf 1 / 2 ,Zr 1 / 2 ) 6 Ta 2 O 17 . The average ratio of the inner diameter to the outer diameter of the composite powder is 0.5. Measure the inner diameter and outer diameter of the composite powder to obtain the ratio of the inner diameter to the outer diameter of the composite powder. See the scanning electron microscope photos of the composite powder in Figure 1 and Figure 2 . The composite powder is a spherical powder with a hollow structure.

[0057] A preparation method of a thermal barrier coating is carried out by atmospheric plasma spraying using the aforementioned composite powder for the thermal barrier coating to obtain the thermal barrier coating. The spraying distance of the atmospheric plasma spraying is 110 mm, the spraying power is 45 kw, the carrier gas flow rate is 3 slpm, and the powder feeding rate is 15 g / min. See the scanning electron microscope photograph of the thermal barrier coating in Figure 3 , and pores are diffusely distributed in the thermal barrier coating. The fracture toughness of the thermal barrier coating is 4.3 MPa·m 1 / 2 , and the detection method is "ASTM E1820-23b Standard Test Method for Measurement of Fracture Toughness".

[0058] Example 2

[0059] It is carried out with reference to the preparation method of the composite powder in Example 1. The difference is that in step two, the gas temperature of the rapid cooling of the quenching gas for plasma spheroidization is -40 °C, and the gas flow rate is 40 slpm. Referring to the composite powder in Example 1, the difference is that the ratio of the inner diameter to the outer diameter of the composite powder is 0.25.

[0060] Example 3

[0061] It is carried out with reference to the preparation method of the composite powder in Example 1. The difference is that in step two, the flame power of the plasma spheroidization is 40 kW, and the liquid feeding rate is 12 mL / min. Referring to the composite powder in Example 1, the difference is that the ratio of the inner diameter to the outer diameter of the composite powder is 0.21.

[0062] Example 4

[0063] It is carried out with reference to the preparation method of the thermal barrier coating in Example 1. The difference is that the spraying power of the atmospheric plasma spraying is 40 kW.

[0064] Comparative Example 1

[0065] It is carried out with reference to the preparation method of the composite powder for the thermal barrier coating in Example 1. The difference is that in step one, the molar ratio of ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 is 50:10:20, the molar ratio of Zr 4+ , Hf 4+ and Ta 5+ in the composite salt solution is 50:10:20, and the solid dispersed phase in the suspension includes the chemical formula (Hf 1 / 6 ,Zr 5 / 6 ) 6 Ta 2 O 17The composite tantalate. Refer to the composite powder of Example 1, except that the composite powder comprises a composite tantalate with the chemical formula (Hf 1 / 6 , Zr 5 / 6 ) 6 Ta 2 O 17 . The fracture toughness of the thermal barrier coating is 3.1 MPa·m 1 / 2 .

[0066] Comparative Example 2

[0067] Refer to the preparation method of the composite powder for the thermal barrier coating of Example 1, except that in Step 1, the molar ratio of ZrOCl 2 ·8H 2 O, HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 is 10:50:20, the molar ratio of Zr 4+ , Hf 4+ and Ta 5+ in the composite salt solution is 10:50:20, and the solid dispersion phase in the suspension comprises a composite tantalate with the chemical formula (Hf 5 / 6 , Zr 1 / 6 ) 6 Ta 2 O 17 . Refer to the composite powder of Example 1, except that the composite powder comprises a composite tantalate with the chemical formula (Hf 5 / 6 , Zr 1 / 6 ) 6 Ta 2 O 17 .

[0068] Comparative Example 3

[0069] Refer to the preparation method of the composite powder for the thermal barrier coating of Example 1, except that in Step 1, ZrOCl 2 ·8H 2 O is not added, the molar ratio of HfOCl 2 ·8H 2 O and TaO(NO 3 ) 3 is 80:25, the composite salt solution contains Hf 4+ , Ta 5+ , the molar ratio of Hf 4+ and Ta 5+ in the composite salt solution is 80:25, and the solid dispersion phase in the suspension comprises Hf 6 Ta 2 O 17Tantalate, the composite powder of Reference Example 1, except that the composite powder includes hafnium with the chemical formula 6 Ta 2 O 17 tantalate.

[0070] Comparative Example 4

[0071] Referring to the preparation method of the composite powder for thermal barrier coatings in Reference Example 1, except that in Step 1, HfOCl 2 ·8H 2 O, ZrOCl 2 ·8H 2 O and TaO(NO 3 ) 3 are not added, and the molar ratio of Zr 4+ , Ta 5+ in the composite salt solution is 80:25. The composite salt solution contains Zr 4+ , Ta 5+ , and the molar ratio of Zr 4+ and Ta 5+ in the composite salt solution is 80:25. The solid dispersed phase in the suspension includes Zr 6 Ta 2 O 17 tantalate, the composite powder of Reference Example 1, except that the composite powder includes zirconium with the chemical formula Zr 6 Ta 2 O 17 tantalate. The fracture toughness of the thermal barrier coating is 2.5 MPa·m 1 / 2 .

[0072] Comparative Example 5

[0073] Referring to the preparation method of the composite powder for thermal barrier coatings in Reference Example 1, except that in Step 2, the flame power is 28 kW and the liquid feeding rate is 40 mL / min. The composite powder does not have a hollow structure.

[0074] Test Example

[0075] The thermal barrier coatings obtained in the above Examples and Comparative Examples were subjected to various performance tests shown in Table 1, and the results are shown in Table 1. The detection method of thermal conductivity refers to GB / T 22588, the detection method of high-temperature phase structure stability refers to JY / T 5320-2006, the detection temperature range is 25°C to 1400°C, and the detection method of bonding strength refers to ISO 1491. The phase structure of the coating completed by atmospheric plasma spraying in Example 1 is shown in Figure 4 , and the phase structure completed by the detection of high-temperature phase structure stability at 25°C to 1400°C is shown in Figure 5 . The phase structure stability is good and there is no phase change.

[0076] Table 1

[0077]

[0078] Comparing Comparative Example 1 and the Example, for the composite tantalate (Hf x , Zr 1-x ), 6 Ta 2 O 17 when x is not less than 0.2, it can improve the fracture toughness of the coating, the stability of the high-temperature phase structure, and reduce the thermal conductivity of the coating. Comparing Comparative Example 2 and the Example, for the composite tantalate (Hf x , Zr 1-x ), 6 Ta 2 O 17 when x is not greater than 0.8, it can improve the stability of the high-temperature phase structure of the coating and reduce the thermal conductivity of the coating. Comparing Comparative Example 3 and the Example, compared with doping only Hf, co-doping Hf and Zr to form a composite tantalate can improve the stability of the high-temperature phase structure of the coating and reduce the thermal conductivity of the coating. Comparing Comparative Example 4 and the Example, compared with doping only Zr, co-doping Hf and Zr to form a composite tantalate can improve the fracture toughness, the stability of the high-temperature phase structure of the coating and reduce the thermal conductivity of the coating. Comparing Comparative Example 5 and the Example, using a composite powder with a hollow structure can improve the coating bonding strength and reduce the thermal conductivity of the coating.

[0079] Comparing Examples 1 to 3, when the ratio of the inner diameter to the outer diameter of the composite powder is not less than 0.25, it is more conducive to improving the coating bonding strength and reducing the thermal conductivity of the coating. When the ratio of the inner diameter to the outer diameter of the composite powder is not less than 0.4, it is further more conducive to improving the coating bonding strength and reducing the thermal conductivity of the coating. Comparing Example 1 and Example 4, when the spraying power of atmospheric plasma spraying is not less than 43 kw, it is more conducive to improving the coating bonding strength.

[0080] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A composite powder for thermal barrier coating, characterized in that: The composite powder is a spherical powder with a hollow structure. The composite powder includes a chemical formula of (Hf x ,Zr 1-x )6Ta2O 17 A composite tantalate, wherein x is 0.2 to 0.8; the ratio of the inner diameter to the outer diameter of the composite powder is 0.4 to 0.6; The preparation method of the composite powder comprises: preparing a Zr 4+ , Hf 4+ 、 5+ A composite salt solution, adding a precipitant to the composite salt solution to obtain a suspension, and plasma spheroidizing the suspension to obtain the composite powder for the thermal barrier coating; The composite salt solution contains Zr 4+ , Hf 4+ and Ta 5+ The molar ratio of is 20-40:20-75:15-40, and the solid dispersed phase in the suspension includes a chemical formula of (Hf x ,Zr 1-x )6Ta2O 17 The composite tantalate, x is 0.2~0.8, and the conditions of plasma spheroidization include: flame power of 42kW~48kW, liquid feeding rate of 5mL / min~10mL / min, rapid cooling by quenching gas after the solid dispersed phase is melted, the gas temperature of the quenching gas rapid cooling is -15℃~0℃, and the gas flow rate is 20slpm~30slpm.

2. A method for preparing the composite powder for thermal barrier coating according to claim 1, characterized in that: include: Preparation of Zr 4+ , Hf 4+ 、 5+ A composite salt solution, adding a precipitant to the composite salt solution to obtain a suspension, and plasma spheroidizing the suspension to obtain the composite powder for the thermal barrier coating; The composite salt solution contains Zr 4+ , Hf 4+ and Ta 5+ The molar ratio of is 20-40:20-75:15-40, and the solid dispersed phase in the suspension includes a chemical formula of (Hf x ,Zr 1-x )6Ta2O 17 The composite tantalate, x is 0.2~0.8, and the conditions of plasma spheroidization include: flame power of 42kW~48kW, liquid feeding rate of 5mL / min~10mL / min, rapid cooling by quenching gas after the solid dispersed phase is melted, the gas temperature of the quenching gas rapid cooling is -15℃~0℃, and the gas flow rate is 20slpm~30slpm.

3. The preparation method according to claim 2, characterized in that: The composite salt solution is prepared by dissolving a mixture of ZrOCl2·8H2O, HfOCl2·8H2O and TaO(NO3)3 in water; and the precipitant is ammonia water.

4. A method for preparing a thermal barrier coating, characterized in that: The composite powder for thermal barrier coating according to claim 1 and / or the composite powder for thermal barrier coating prepared by the preparation method according to claim 2 or 3 is subjected to atmospheric plasma spraying to obtain a thermal barrier coating.

5. The preparation method according to claim 4, characterized in that: The conditions of the atmospheric plasma spraying include: a spraying distance of 90 mm to 120 mm, a spraying power of 43 kW to 47 kW, a carrier gas flow rate of 2 slpm to 5 slpm, and a powder feeding rate of 10 g / min to 20 g / min; and / or, Before atmospheric plasma spraying of the composite powder for thermal barrier coating according to claim 1 and / or the composite powder for thermal barrier coating prepared by the preparation method according to claim 2 or 3, an MCrAlY coating and a YSZ coating are sprayed in sequence.

6. A thermal barrier coating, characterized in that: The compound is prepared by the preparation method according to claim 4 or 5.

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