A high thermal stability and low thermal conductivity zirconia-based thermal barrier coating and its preparation method

Abstract

The present invention discloses a high thermal stability and low thermal conductivity zirconium oxide based thermal barrier coating and a preparation method thereof, wherein the raw materials include: 5% to 10% (Y x Sc y Gd 1‑x‑y )2O3, 10%~20% LaPO4, 1%~5% MO z , 8.6%~15.2% RE2O3, the balance is ZrO2; (Y x Sc y Gd 1‑x‑y )2O3, x =0.5~0.75, y =0.05~0.15;MO z In RE2O3, M is one or more of Mg, Ca, and In; in RE2O3, RE is one or more of Er, Sm, Dy, Yb, and Eu. The present invention modifies the components of a zirconia-based thermal barrier coating by doping and optimizes its preparation process, effectively improving the thermal barrier coating's high-temperature stability, thermal shock resistance, and sintering resistance, while reducing its high-temperature thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal barrier coatings, and in particular to a high thermal stability and low thermal conductivity zirconia-based thermal barrier coating and a preparation method thereof. Background Art

[0002] Gas turbines and aircraft engines are important power equipment. However, their extremely high operating temperatures create a harsh operating environment for the hot-end components of these engines. They must withstand high-temperature oxidation, corrosion, and high-velocity airflow, resisting high-temperature creep and thermomechanical fatigue. Improving the reliability and service life of high-temperature components has become a critical issue that needs to be addressed in the gas turbine and aircraft engine fields. Using advanced surface technologies to locally modify or protect the surfaces of high-temperature components is a cost-effective and effective way to improve their high-temperature tolerance, safety, and reliability.

[0003] Thermal barrier coatings (TBCs) are among the most advanced high-temperature protective coatings to date. They possess excellent thermal insulation, erosion resistance, and high-temperature chemical stability. They can significantly increase the operating temperature of high-temperature alloy components and extend the service life of hot-end components. Currently, Y2O3 partially stabilized ZrO2 (YSZ) ceramics and rare earth zirconates are widely used in the field of thermal barrier coatings. However, YSZ thermal barrier coatings have relatively high thermal conductivity, low high-temperature thermal radiation absorption, and are prone to sintering and phase transformation at high temperatures, causing cracking and shedding of the coating. Rare earth zirconates, on the other hand, have limited widespread application due to their low thermal expansion coefficient and poor fracture toughness.

[0004] While plasma spraying thermal barrier coatings offers advantages such as high deposition rates, low cost, no size restrictions, and large-scale production, the coating material composition system is not fully designed, and the preparation process is not yet perfected, making it difficult to produce high-quality thermal barrier coatings, which affects their service reliability and service life. With the continuous development of engines with high thrust-to-weight ratios, high flow rates, and high inlet temperatures, traditional thermal barrier coating materials are no longer able to meet performance requirements. Therefore, there is an urgent need to develop high-performance thermal barrier coating materials with excellent volume stability and thermophysical properties. Summary of the Invention

[0005] The present invention aims to overcome the problems of poor high-temperature stability, poor sintering resistance, easy peeling and oxidation, and short service life of thermal barrier coatings in the prior art. It provides a high-thermal-stability, low-thermal-conductivity zirconia-based thermal barrier coating and a preparation method thereof. The components are doped and modified, and the preparation process is optimized, which can effectively improve the high-temperature stability, thermal shock resistance, and sintering resistance of the thermal barrier coating and reduce its high-temperature thermal conductivity.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high thermal stability and low thermal conductivity zirconium oxide based thermal barrier coating, characterized in that, in terms of mass percentage, the raw materials include: 5% to 10% (Y x Sc y Gd 1-x-y )2O3, 10%~20% LaPO4, 1%~5% MO z , 8.6%~15.2% RE2O3, the balance is ZrO2;

[0008] (Y x Sc y Gd 1-x-y )2O3, x =0.5~0.75, y =0.05~0.15;

[0009] MO z wherein M is one or more of Mg, Ca, and In;

[0010] In RE2O3, RE is one or more of Er, Sm, Dy, Yb, and Eu.

[0011] The ZrO2-based thermal barrier coating doped with (Y x Sc y Gd 1-x-y )2O3, part of Sc and Gd replaces Y, which can improve the coating strength, enhance the fracture toughness and oxidation resistance, and effectively reduce the distortion of the tetragonal phase and promote the formation of a stable non-equilibrium tetragonal phase. z Doping, M a+ (Ca 2+ Mg 2+ or In 3+ ) cations enter the zirconia lattice. Due to the different valences of the ions, in order to maintain the electrical neutrality in the lattice, the ZrO2 crystal is stabilized from 8-coordinate to 7-coordinate, thereby generating a large number of oxygen vacancies, which can effectively prevent the phase change of ZrO2 during the thermal cycle, so that it always maintains a non-equilibrium tetragonal phase, and improves the high-temperature stability of the coating. The introduction of LaPO4 will form a network-like structure inside the substrate, which has a significant hindering effect on photons, reducing the energy density of photons in the original propagation direction, and reducing the high-temperature thermal conductivity of the coating; at the same time, it effectively inhibits the recovery of thermal conductivity in the high-temperature section. After doping with rare earth oxide RE2O3, RE 3+ It enters the ZrO2 lattice, causing lattice distortion and reducing thermal conductivity; inhibiting grain growth and improving sintering resistance; increasing surface infrared reflectivity, reducing radiation thermal conductivity, inducing coating grain size to be uniform and densely stacked, hindering the diffusion of oxygen elements, reducing the growth and evolution of the interface oxide layer, and improving thermal shock resistance life.

[0012] The zirconia-based thermal barrier coating of the present invention has a reasonable composition design. Compared with the 8YSZ thermal barrier coating prepared by the same process, at 1500°C, the thermal expansion coefficient is similar, the high-temperature thermal conductivity is reduced by 52%, the hardness is increased by 11.5%, the fracture toughness is increased by 74.7%, the high-temperature phase stability is good, the thermal shock resistance is good (the number of thermal cycles is increased by 12.3 times), and the sintering resistance is excellent (the density change rate is reduced by 55.2%).

[0013] The present invention also provides a method for preparing the above-mentioned high thermal stability and low thermal conductivity zirconia-based thermal barrier coating, comprising the following steps:

[0014] (1) Mix the raw materials in proportion, add deionized water, dispersant, and binder, and perform ball milling to prepare a suspension;

[0015] (2) spray-drying the obtained suspension into powder, sintering, crushing, and screening to obtain raw material powder of zirconia-based thermal barrier coating;

[0016] (3) Clean, sandblast, roughen and preheat the surface of the alloy substrate to be sprayed;

[0017] (4) using atmospheric plasma spraying to spray metal bonding layer raw material powder on the surface of the preheated alloy substrate to obtain a metal bonding layer;

[0018] (5) The zirconia-based thermal barrier coating raw material powder is sprayed on the surface of the metal bonding layer by an atmospheric plasma spraying method to obtain the high thermal stability and low thermal conductivity zirconia-based thermal barrier coating.

[0019] Preferably, in the suspension obtained in step (1), the mass ratio of the total mass of the raw materials to the deionized water, the dispersant, and the binder is 1:0.7-1.2:0.005-0.02:0.01-0.05, the dispersant is one of polyethylene glycol and sodium citrate, and the binder is one of polyvinyl alcohol and arabic resin powder.

[0020] Preferably, in step (2), the sintering temperature is 1300-1800°C, and the sintering time is 5-12 h; the particle size of the obtained zirconia-based thermal barrier coating raw material powder is 250-350 mesh.

[0021] Preferably, the sandblasting used in step (3) is 10-50 mesh quartz sand or corundum sand, the sandblasting pressure and sandblasting time are 0.2-0.8 MPa and 3-10 min respectively, and the preheating temperature of the alloy substrate is 80-150°C. The present invention optimizes the sandblasting process by screening the appropriate sandblasting type and particle size, effectively preventing the sandblasting particles from being fragmented during the sandblasting process to form irregular shaped secondary particles embedded in the substrate, causing damage and component contamination; forming a certain degree of roughness on the substrate surface to achieve mechanical engagement between the coating and the substrate, thereby enhancing the bonding strength between the coating and the substrate; and generating a certain compressive stress on the substrate surface to partially offset the tensile stress generated during the coating spraying process, thereby reducing the residual stress of the coating.

[0022] Preferably, the raw material powder of the metal bonding layer described in step (4) comprises the following components: 18% to 30% Co, 15% to 30% Cr, 5% to 13% Al, 0.1% to 1% Y, 0.5% to 5% A, and the balance Ni; A is one of the active oxygen elements Si, W, and Mo. The present invention bonds the zirconium oxide-based thermal barrier coating to the substrate through the metal bonding layer, and by doping the metal bonding layer with an appropriate amount of active oxygen elements, promotes the formation of an oxide layer with uniform thickness, promotes the formation of fine Al2O3 columnar crystals, and improves the bonding strength of the Al2O3 film layer; at the same time, it helps to make the diffusion rate of oxygen atoms exceed that of aluminum atoms, thereby reducing the growth rate of a-Al2O3, avoiding the formation of interfacial spinel and mixed oxides due to the depletion of Al elements, playing a certain inhibitory role on interfacial oxidation behavior, and improving the resistance of the interfacial oxide layer to cracking and failure.

[0023] Preferably, the process parameters for preparing the metal bonding layer in step (4) are: the distance between the workpiece and the nozzle is 100~180 mm, the powder feeding rate is 20~50 g / min, the spraying current is 450~550 A, the voltage is 60~75 V, the main gas flow rate is 40~50 L / min, the auxiliary gas flow rate is 2~5 L / min, the carrier gas flow rate is 4~8 L / min, the lateral movement rate of the spray gun is 300~600 mm / s, and the longitudinal movement rate of the spray gun is 2~10 mm / s.

[0024] Preferably, the process parameters for preparing the high thermal stability and low thermal conductivity zirconia-based thermal barrier coating in step (5) are as follows: the distance between the workpiece and the nozzle is 50~120 mm, the powder feeding rate is 20~50 g / min, the spraying current is 550~650 A, the voltage is 75~90 V, the main gas flow rate is 30~45 L / min, the auxiliary gas flow rate is 4~10 L / min, the carrier gas flow rate is 2~8 L / min, the lateral movement rate of the spray gun is 300~1000 mm / s, and the longitudinal movement rate of the spray gun is 2~10 mm / s.

[0025] By optimizing the process of the atmospheric plasma spraying system, the present invention can not only ensure that the sprayed particles can be fully melted, spread, wetted and overlapped, thereby reducing defects such as porosity and unmelted particles in the coating, but also can efficiently prepare large-area high-quality thermal barrier coatings, realize continuous automated operation, and facilitate large-scale production and application.

[0026] Preferably, when the plasma spraying operation in step (4) and step (5) lasts for more than 3 to 5 minutes, the spraying is suspended and compressed air is used for cooling.

[0027] Preferably, before the atmospheric plasma spraying in step (4) and step (5), the raw material powder of the metal bonding layer and the raw material powder of the zirconium oxide-based thermal barrier coating are vacuum dried at a drying temperature of 70-300°C, a drying time of 1-5 hours, and a vacuum degree of 5×10 -4 ~1×10 -6 Pa.

[0028] Therefore, the present invention has the following beneficial effects:

[0029] (1) Adopt (Y x Sc y Gd 1-x-y )2O3、MO z Doping ZrO2 with LaPO4, RE2O3 and other components can effectively improve the high-temperature stability, thermal shock resistance and sintering resistance of the thermal barrier coating and reduce its high-temperature thermal conductivity;

[0030] (2) By doping the metal bonding layer with an appropriate amount of active oxygen elements, the formation of an oxide layer with uniform thickness is promoted, thereby improving the resistance of the interface oxide layer to cracking and failure;

[0031] (3) By selecting the appropriate sandblasting type and particle size, the sandblasting process is optimized to effectively prevent the sandblasting particles from breaking into irregular-shaped secondary particles during sandblasting, which may be embedded in the substrate and cause damage and component contamination, and enhance the bonding strength between the coating and the substrate;

[0032] (4) By optimizing the atmospheric plasma spraying process, not only can the defects of the coating such as pores and unmelted particles be reduced, but also a large area of high-quality thermal barrier coating can be efficiently prepared, which can realize continuous automated operation and is easy to mass produce and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a comparison chart of thermal conductivity of thermal barrier coatings of the embodiment of the present invention and the comparative example;

[0034] Figure 2 This is a comparison chart of thermal expansion coefficients of thermal barrier coatings of the embodiment of the present invention and the comparative example;

[0035] Figure 3 This is a comparison chart of the hardness and fracture toughness of thermal barrier coatings of the embodiment and the comparative example of the present invention;

[0036] Figure 4 This is a comparison chart of the density change rate of thermal barrier coatings after high-temperature sintering in the embodiment of the present invention and the comparative example;

[0037] Figure 5 This is a comparison chart of the thermal cycle times of thermal barrier coatings of the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] In the present invention, unless otherwise specified, the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following examples, unless otherwise specified, are all conventional methods in the art.

[0040] Example 1:

[0041] A high thermal stability and low thermal conductivity zirconium oxide based thermal barrier coating, the raw materials of which are calculated by mass percentage: (Y 0.6 Sc 0.1 Gd 0.3 )2O35%, LaPO412.5%, In2O32.5%, Er2O3+Dy2O3 (Er2O3: Dy2O3=1:1, mass ratio) 10%, ZrO2 balance.

[0042] The preparation method of the above-mentioned high thermal stability and low thermal conductivity zirconia-based thermal barrier coating comprises the following steps:

[0043] (1) Mix the raw materials in proportion, then add deionized water, polyethylene glycol, and polyvinyl alcohol in a ratio of raw material: deionized water: dispersant: binder = 1:1:0.01:0.025 (mass ratio) and mix them evenly by ball milling to prepare a suspension;

[0044] (2) The suspension in step (1) is spray-dried into powder using a spray drying technique, and sintered at 1650°C for 8 h, and then taken out, crushed, and sieved to obtain a zirconia-based thermal barrier coating raw material powder with a particle size of 300 mesh;

[0045] (3) The raw material powder of the zirconia-based thermal barrier coating in step (2) and the bonding layer powder of NiCoCrAlYSi (the content of each component is: 22.5 wt.% Co, 18% wt.Cr, 7.5 wt.% Al, 0.5 wt.% Y, 1.25 wt.% Si, and the balance is Ni) are placed in a vacuum chamber with a degree of 1×10 -5 Pa drying oven at 200 °C for 5 h;

[0046] (4) The surface of the high-temperature alloy substrate to be sprayed was cleaned and sandblasted with 25-35 mesh corundum sand for 7.5 min at a sandblasting pressure of 0.45 MPa. The treated substrate was then preheated at 120 °C.

[0047] (5) spraying NiCoCrAlYSi bonding layer powder and zirconia-based thermal barrier coating raw material powder in sequence on the surface of the workpiece treated in step (4) by atmospheric plasma spraying to prepare a metal bonding layer and a high thermal stability and low thermal conductivity zirconia-based thermal barrier coating;

[0048] The process parameters for preparing the metal bonding layer are as follows: the distance between the workpiece and the nozzle is 120 mm, the powder feeding rate is 25 g / min, the spraying current is 500 A, the voltage is 70 V, the main gas (Ar) flow rate is 45 L / min, the auxiliary gas (H2) flow rate is 4 L / min, the carrier gas (Ar) flow rate is 5 L / min, the lateral movement rate of the spray gun is 500 mm / s, and the longitudinal movement rate of the spray gun is 3 mm / s.

[0049] The process parameters for preparing high thermal stability and low thermal conductivity zirconia-based thermal barrier coatings are as follows: the distance between the workpiece and the nozzle is 85 mm, the powder feeding rate is 25 g / min, the spraying current is 600 A, the voltage is 80 V, the main gas (Ar) flow rate is 30 L / min, the auxiliary gas (H2) flow rate is 4 L / min, the carrier gas (Ar) flow rate is 3 L / min, the lateral movement rate of the spray gun is 500 mm / s, and the longitudinal movement rate of the spray gun is 5 mm / s.

[0050] Example 2:

[0051] A high thermal stability and low thermal conductivity zirconium oxide based thermal barrier coating, the raw materials of which are calculated by mass percentage: (Y 0.5 Sc 0.1 Gd 0.4 )2O37.5%, LaPO415%, MgO 1.5%, Er2O3+Yb2O3 (Er2O3: Yb2O3=2:3, mass ratio) 11.5%, ZrO2 balance.

[0052] The preparation method of the above-mentioned high thermal stability and low thermal conductivity zirconia-based thermal barrier coating comprises the following steps:

[0053] (1) Mix the raw materials in proportion, then add deionized water, polyethylene glycol, and arabic resin powder in a ratio of raw material: deionized water: dispersant: binder = 1:1:0.02:0.02 (mass ratio) and mix them evenly by ball milling to prepare a suspension;

[0054] (2) The suspension in step (1) is spray-dried into powder using a spray drying technique, and sintered at 1600°C for 7.5 h, and then taken out, crushed, and sieved to obtain a zirconia-based thermal barrier coating raw material powder with a particle size of 300 mesh;

[0055] (3) The raw material powder of the zirconia-based thermal barrier coating in step (2) and the bonding layer powder of NiCoCrAlYW (component content: 21 wt.% Co, 25 wt.% Cr, 10 wt.% Al, 0.8 wt.% Y, 1.5 wt.% W, and the balance is Ni) are placed in a vacuum chamber with a degree of 1×10 -5 Pa drying oven at 200 °C for 5 h;

[0056] (4) The surface of the high-temperature alloy substrate to be sprayed was cleaned and sandblasted with 25-35 mesh corundum sand for 8 minutes at a sandblasting pressure of 0.5 MPa. The treated substrate was then preheated at 100 °C.

[0057] (5) spraying NiCoCrAlYW bonding layer powder and zirconia-based thermal barrier coating raw material powder in sequence on the surface of the workpiece treated in step (4) by atmospheric plasma spraying to prepare a metal bonding layer and a high thermal stability and low thermal conductivity zirconia-based thermal barrier coating;

[0058] The process parameters for preparing the metal bonding layer are as follows: the distance between the workpiece and the nozzle is 115 mm, the powder feeding rate is 27.5 g / min, the spraying current is 515 A, the voltage is 70 V, the main gas (Ar) flow rate is 45 L / min, the auxiliary gas (H2) flow rate is 5 L / min, the carrier gas (Ar) flow rate is 5.5 L / min, the lateral movement rate of the spray gun is 500 mm / s, and the longitudinal movement rate of the spray gun is 5 mm / s.

[0059] The process parameters for preparing high thermal stability and low thermal conductivity zirconia-based thermal barrier coatings are as follows: the distance between the workpiece and the nozzle is 95 mm, the powder feeding rate is 30 g / min, the spraying current is 645 A, the voltage is 80 V, the main gas (Ar) flow rate is 30 L / min, the auxiliary gas (H2) flow rate is 4 L / min, the carrier gas (Ar) flow rate is 3 L / min, the lateral movement rate of the spray gun is 500 mm / s, and the longitudinal movement rate of the spray gun is 5 mm / s.

[0060] Example 3:

[0061] A high thermal stability and low thermal conductivity zirconium oxide based thermal barrier coating, the raw materials of which are calculated by mass percentage: (Y 0.75 Sc 0.15 Gd 0.1)2O310%, LaPO415%, In2O3+CaO 3%, Yb2O3+Dy2O3+Sm2O3 (Yb2O3: Dy2O3: Sm2O3=1.5:1:0.8, mass ratio) 10.6%, ZrO2 balance.

[0062] The preparation method of the above-mentioned high thermal stability and low thermal conductivity zirconia-based thermal barrier coating comprises the following steps:

[0063] (1) Mix the raw materials in proportion, then add deionized water, sodium citrate, and polyvinyl alcohol in a ratio of raw material: deionized water: dispersant: binder = 1:1:0.02:0.02 (mass ratio) and mix them evenly by ball milling to prepare a suspension;

[0064] (2) The suspension in step (1) is spray-dried into powder using a spray drying technique, and sintered at 1700°C for 7.5 h, and then taken out, crushed, and sieved to obtain a zirconia-based thermal barrier coating raw material powder with a particle size of 300 mesh;

[0065] (3) The raw material powder of the zirconia-based thermal barrier coating in step (2) and the bonding layer powder of NiCoCrAlYSiW (the content of each component is: 21 wt.% Co, 18 wt.% Cr, 7.5 wt.% Al, 1 wt.% Y, 1 wt.% Si, 0.5 wt.% W, and the balance is Ni) are placed in a vacuum chamber with a degree of 1×10 -5 Pa drying oven at 200 °C for 5 h;

[0066] (4) The surface of the high-temperature alloy substrate to be sprayed was cleaned and sandblasted with 25-35 mesh corundum sand for 10 minutes at a sandblasting pressure of 0.5 MPa. The treated substrate was then preheated at 100 °C.

[0067] (5) spraying NiCoCrAlYSiW bonding layer powder and zirconia-based thermal barrier coating raw material powder on the surface of the workpiece treated in step (4) in sequence by atmospheric plasma spraying to prepare a metal bonding layer and a high thermal stability and low thermal conductivity zirconia-based thermal barrier coating;

[0068] The process parameters for preparing the metal bonding layer are as follows: the distance between the workpiece and the nozzle is 110 mm, the powder feeding rate is 30 g / min, the spraying current is 525 A, the voltage is 70 V, the main gas (Ar) flow rate is 45 L / min, the auxiliary gas (H2) flow rate is 4 L / min, the carrier gas (Ar) flow rate is 5 L / min, the lateral movement rate of the spray gun is 400 mm / s, and the longitudinal movement rate of the spray gun is 3 mm / s.

[0069] The process parameters for preparing high thermal stability and low thermal conductivity zirconia-based thermal barrier coatings are as follows: the distance between the workpiece and the nozzle is 80 mm, the powder feeding rate is 25 g / min, the spraying current is 650 A, the voltage is 80 V, the main gas (Ar) flow rate is 30 L / min, the auxiliary gas (H2) flow rate is 4 L / min, the carrier gas (Ar) flow rate is 3 L / min, the lateral movement rate of the spray gun is 500 mm / s, and the longitudinal movement rate of the spray gun is 5 mm / s.

[0070] Comparative Example 1:

[0071] The raw material of the zirconium oxide-based thermal barrier coating in Comparative Example 1 is 8YSZ (8 wt.% Y2O3 and 92 wt.% ZrO2), and the preparation method is the same as that in Example 1.

[0072] The properties of the zirconium oxide based thermal barrier coatings prepared in the above examples and comparative examples were tested, and the results are as follows: Figures 1 to 5 As shown in Tables 1 and 2.

[0073] Among them, the performance test method is:

[0074] (1) Thermal conductivity

[0075] The thermal diffusivity and specific heat capacity of the coating were measured using a laser thermal conductivity meter, and the density was measured according to the Archimedean principle. The thermal conductivity was calculated according to formula ①:

[0076] ①

[0077] Where: k is thermal conductivity, W / (m·K);

[0078] Cp is the specific heat capacity, J / (g·K);

[0079] l is the thermal diffusivity, mm 2 / s;

[0080] P is density, g / cm 3 .

[0081] (2) Thermal expansion coefficient

[0082] The linear thermal expansion coefficient of the coating was tested using a thermal dilatometer in an air atmosphere at a temperature ranging from room temperature to 1500°C at a heating rate of 5°C / min.

[0083] (3) Hardness and fracture toughness

[0084] The Vickers hardness tester was used to test the coating's fracture toughness using the indentation method. Test conditions: 300gf loading force, 10s loading time, hardness readings and crack length measurements, averaging 10 test points. Fracture toughness was calculated using formula ②:

[0085] ②

[0086] Where: K IC is the fracture toughness, MPa·m 0.5 ;

[0087] HV is the Vickers hardness, GPa;

[0088] a is the diagonal length of the indentation, mm;

[0089] c is the crack length, mm.

[0090] (3) Coating bonding strength

[0091] According to GB8642-2002 “Determination of Bond Strength of Thermal Spray Coatings”, the bonding strength of the coating was determined by the bonding tensile method with a tensile speed of 2 mm / min. Five tests were performed and the average value was taken.

[0092] (4) Sintering resistance

[0093] The coating samples were heat treated at 1100℃~1500℃, with a heating rate of 10℃ / min and a holding time of 100h. The samples were cooled in the furnace. The density of the samples before and after sintering was tested by the drainage method. The density change rate was calculated according to formula ③:

[0094] ③

[0095] Where d is the density change rate;

[0096] r T is the density after sintering at different temperatures;

[0097] r 1100 The density after sintering at 1100℃.

[0098] (5) High temperature phase stability:

[0099] The coating samples were subjected to high temperature heat treatment at 1100℃~1500℃ for 400 h at a heating rate of 10℃ / min, and then cooled in the furnace. The coating phase composition and content were tested using XRD technology.

[0100] Note: Non-equilibrium tetragonal phase t′, equilibrium tetragonal phase t, cubic phase c, monoclinic phase m.

[0101] (6) Thermal shock resistance

[0102] Thermal shock tests were performed on the coating samples at 1100°C to 1500°C. The furnace temperature was first raised to a preset temperature, and the coated sample was then placed in the furnace, held at that temperature for 5 minutes, and then removed and air-cooled. The above steps were repeated, and the number of thermal shocks was recorded. Failure was determined when the coating peeled off by more than 10% of the surface area.

[0103] Table 1: Coating bonding strength test results

[0104]

[0105] Table 2: High temperature phase stability test results

[0106]

[0107] from Figures 1 to 5 As can be seen from Tables 1 and 2, the composition of the zirconia-based thermal barrier coating in the present invention is reasonably designed. Compared with the 8YSZ thermal barrier coating prepared by the same process in Comparative Example 1, at 1500°C, the thermal barrier coating in Example 1 has a similar thermal expansion coefficient, a 52% decrease in high-temperature thermal conductivity, an 11.5% increase in hardness, and a 74.7% increase in fracture toughness. It has good high-temperature phase stability, good thermal shock resistance (the number of thermal cycles increased by 12.3 times), and excellent sintering resistance (the density change rate decreased by 55.2%).

Claims

1. A method for preparing a high thermal stability and low thermal conductivity zirconia-based thermal barrier coating, characterized in that: The steps include: (1) Mix the raw materials in proportion, add deionized water, dispersant and binder and mix by ball milling to prepare a suspension; in terms of mass percentage, the raw materials include: 5%~10% (Y x Sc y Gd 1-x-y )2O3, 10%~20% LaPO4, 1%~5% MO z , 8.6%~15.2% RE2O3, the balance is ZrO2; (Y x Sc y Gd 1-x-y )2O3, x =0.5~0.75, y =0.05~0.15; MO z Wherein, M is one or more of Mg, Ca, and In; In RE2O3, RE is one or more of Er, Sm, Dy, Yb, and Eu; (2) spray-drying the obtained suspension into powder, sintering, crushing, and screening to obtain raw material powder of zirconia-based thermal barrier coating; (3) Clean, sandblast, roughen and preheat the surface of the alloy substrate to be sprayed; (4) spraying a metal bonding layer raw material powder on the surface of the preheated alloy substrate by an atmospheric plasma spraying method to obtain a metal bonding layer; the components of the metal bonding layer raw material powder include, by mass percentage, 18% to 30% Co, 15% to 30% Cr, 5% to 13% Al, 0.1% to 1% Y, 0.5% to 5% A, and the balance is Ni; A is one of the active oxygen elements W and Mo; (5) The zirconia-based thermal barrier coating raw material powder is sprayed on the surface of the metal bonding layer by an atmospheric plasma spraying method to obtain the high thermal stability and low thermal conductivity zirconia-based thermal barrier coating.

2. The preparation method according to claim 1, wherein In the suspension obtained in step (1), the mass ratio of the total mass of the raw materials to the mass of deionized water, the dispersant, and the binder is 1:0.7~1.2:0.005~0.02:0.01~0.05; the dispersant is one of polyethylene glycol and sodium citrate, and the binder is one of polyvinyl alcohol and arabic resin powder.

3. The preparation method according to claim 1, wherein In step (2), the sintering temperature is 1300-1800° C., and the sintering time is 5-12 h; the particle size of the obtained zirconia-based thermal barrier coating raw material powder is 250-350 mesh.

4. The preparation method according to claim 1, wherein The sandblasting used in step (3) is 10-50 mesh quartz sand or corundum sand, the sandblasting pressure and sandblasting time are 0.2-0.8 MPa and 3-10 min respectively, and the preheating temperature of the alloy substrate is 80-150°C.

5. The preparation method according to claim 1, wherein The process parameters for preparing the metal bonding layer in step (4) are as follows: the distance between the workpiece and the nozzle is 100~180 mm, the powder feeding rate is 20~50 g / min, the spraying current is 450~550 A, the voltage is 60~75 V, the main gas flow rate is 40~50 L / min, the auxiliary gas flow rate is 2~5 L / min, the carrier gas flow rate is 4~8 L / min, the lateral movement rate of the spray gun is 300~600 mm / s, and the longitudinal movement rate of the spray gun is 2~10 mm / s.

6. The preparation method according to claim 1, wherein The process parameters for preparing the high thermal stability and low thermal conductivity zirconia-based thermal barrier coating in step (5) are as follows: the distance between the workpiece and the nozzle is 50~120 mm, the powder feeding rate is 20~50 g / min, the spraying current is 550~650 A, the voltage is 75~90 V, the main gas flow rate is 30~45 L / min, the auxiliary gas flow rate is 4~10 L / min, the carrier gas flow rate is 2~8 L / min, the lateral movement rate of the spray gun is 300~1000 mm / s, and the longitudinal movement rate of the spray gun is 2~10 mm / s.

7. The preparation method according to claim 1, 5 or 6, characterized in that: When the plasma spraying operation in step (4) and step (5) exceeds 3 to 5 minutes, the spraying is suspended and compressed air is used for cooling.

8. The preparation method according to claim 2, wherein Before the atmospheric plasma spraying in step (4) and step (5), the raw powder of the metal bonding layer and the raw powder of the zirconium oxide-based thermal barrier coating are first vacuum dried at a drying temperature of 70-300°C, a drying time of 1-5 hours, and a vacuum degree of 5×10 -4 ~1×10 -6 Pa.

9. A high thermal stability and low thermal conductivity zirconia-based thermal barrier coating prepared using the preparation method according to any one of claims 1 to 8.

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