PS-PVD-based CMAS protective thermal barrier coating and preparation method thereof

Abstract

The invention provides a PS-PVD-based CMAS protective thermal barrier coating and a preparation method thereof, relates to the technical field of protective coatings, and is designed for solving the problem that an existing thermal barrier coating is relatively weak in CMAS corrosion resistance. The thermal barrier coating comprises a bonding layer, a first ceramic layer, a second ceramic layer and a surface compact layer which are sequentially arranged from inside to outside, the material of the surface compact layer is the same as that of the second ceramic layer, and the porosity of the surface compact layer is reduced in a gradient mode from inside to outside. And the structure of the surface compact layer is gradually transited from a quasi-columnar structure of an inner layer to a layered structure of an outer layer. The anti-CMAS corrosion coating has high CMAS corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of protective coatings, and in particular to a PS-PVD-based CMAS protective thermal barrier coating and a preparation method thereof. Background Art

[0002] The core hot end components of aircraft engines and gas turbines are turbine blades, and thermal barrier coatings are an indispensable key thermal protection technology for the surface of turbine blades. When aircraft engines and gas turbines are working, they often encounter environmental deposits such as sand, volcanic ash or salt spray. Such environmental deposits adhere to the surface of thermal barrier coatings, corrode and penetrate the thermal barrier coatings, and cause the thermal barrier coatings to peel off and fail. The more typical environmental deposits are CMAS, which mainly include CaO, MgO, Al2O3 and SiO2, and the existing thermal barrier coatings have weak resistance to CMAS corrosion.

[0003] PS-PVD (Plasma Spray Physical Vapor Deposition) is an advanced coating preparation technology that has gradually developed in recent years. The thermal barrier coating prepared by PS-PVD has the high porosity and high thermal insulation characteristics of the thermal barrier coating prepared by APS (Air Plasma Spray) and the high strain tolerance and long life characteristics of the thermal barrier coating prepared by EB-PVD (Electron Beam Physical Vapor Deposition). It is the development trend of coating preparation technology in the future.

[0004] PS-PVD has a complex nucleation and continuous deposition mechanism. The solid, liquid and gas phases can all nucleate and grow competitively. It is extremely difficult to control the structure of the coating, and it is not easy to obtain a dense layer on the sample surface. Summary of the invention

[0005] The first object of the present invention is to provide a CMAS protective thermal barrier coating based on PS-PVD to solve the technical problem that the existing thermal barrier coating has weak CMAS corrosion resistance.

[0006] The PS-PVD-based CMAS protective thermal barrier coating provided by the present invention comprises a bonding layer, a first ceramic layer, a second ceramic layer and a surface dense layer which are arranged in sequence from the inside to the outside, wherein the material of the surface dense layer is the same as that of the second ceramic layer, and the porosity of the surface dense layer decreases gradually from the inside to the outside, and the structure of the surface dense layer gradually transitions from the quasi-columnar structure of the inner layer to the layered structure of the outer layer.

[0007] Furthermore, the ratio of the thickness of the first ceramic layer to the thickness of the second ceramic layer is between 0.1:1 and 10:1, and the first ceramic layer to the second ceramic layer are morphologically continuously grown quasi-columnar structures.

[0008] Furthermore, the thickness of the surface dense layer is between 1 and 50 μm; and / or the thickness of the surface dense layer is 1% to 20% of the thickness of the thermal barrier coating; and / or the material of the first ceramic layer is yttria-stabilized zirconia; and / or the material of the second ceramic layer and the surface dense layer is rare earth modified zirconate.

[0009] The beneficial effects of the PS-PVD-based CMAS thermal barrier coating of the present invention are:

[0010] The thermal barrier coating sets the porosity of the surface dense layer to decrease gradually from the inside to the outside, and the structure gradually transitions from the quasi-columnar structure of the inner layer to the layered structure of the outer layer, that is, the surface dense layer is formed by a gradient deposition transition process, which, on the one hand, gradually increases the density of the coating, and on the other hand, allows the second ceramic layer to smoothly transition to the surface dense layer. Therefore, the surface dense layer is more tightly combined with the surface and gap positions of the first ceramic layer and the second ceramic layer in the quasi-columnar structure, and no obvious cracks and pores will appear. In addition, the above transition area is also conducive to alleviating the stress between the surface dense layer and the columnar crystals, reducing the risk of coating peeling.

[0011] By setting the material of the surface dense layer to be consistent with the material of the second ceramic layer, the thermal mismatch stress between the two coatings can be avoided, so that the bonding effect between the coatings is better, and the surface dense layer can better cover the surface of the quasi-columnar structure, and play a certain sealing role in the pore cracks and the pores of the quasi-columnar structure, so that the thermal barrier coating has good resistance to CMAS corrosion, so as to reduce the penetration of molten CMAS in practical applications, thereby effectively improving the adaptability of aircraft engines and gas turbine hot end components in harsh environments.

[0012] In addition, since the material of the surface dense layer is consistent with that of the second ceramic layer, no intermediate processing is required during the switching of the coating deposition process. Instead, it can be directly added to the spraying program to achieve streamlined spraying operations with lower production costs.

[0013] The second object of the present invention is to provide a method for preparing a CMAS protective thermal barrier coating based on PS-PVD, so as to solve the technical problem that the existing thermal barrier coating has weak resistance to CMAS corrosion.

[0014] The preparation method of the PS-PVD-based CMAS protective thermal barrier coating provided by the present invention is used to prepare the above thermal barrier coating, comprising:

[0015] Step S100: placing a sample to be processed in a vacuum chamber of a PS-PVD device, evacuating the vacuum chamber, and preheating the sample using a plasma flame; wherein the sample includes a substrate and a bonding layer deposited on the outer surface of the substrate;

[0016] Step S200: running a preset spraying program, turning on a powder feeder, and sequentially depositing a first ceramic layer, a second ceramic layer, and a surface dense layer;

[0017] Step S300: close the powder feeder, run the cooling program, gradually reduce the gas flow, and gradually cool down. After the cooling program is completed, the arc is extinguished and the plasma spray gun is closed;

[0018] Step S400: Ar is filled into the vacuum chamber, and after the pressure of the vacuum chamber reaches one atmosphere and the temperature of the sample drops to a preset temperature, the chamber is opened and taken out to complete the preparation.

[0019] Furthermore, in the step S100, the vacuum degree of the vacuum chamber is 10-500 Pa; and the preheating temperature of the sample is 500-800°C.

[0020] Furthermore, in step S200, the spraying current of the plasma spray gun used for depositing the first ceramic layer, the second ceramic layer and the surface dense layer is 1600-2200A; the Ar flow rate used for depositing the first ceramic layer and the second ceramic layer is 20-40SLPM, and the He flow rate is 50-70SLPM.

[0021] Furthermore, in the step S200, the process of depositing the surface dense layer includes 3 to 8 process steps, wherein during the entire process of depositing the surface dense layer, the flow rate of Ar is gradually increased from 20 to 40 SLPM to 100 to 130 SLPM, and the flow rate of He is gradually decreased from 50 to 70 SLPM to 10 to 30 SLPM; the thickness of the surface dense layer formed in each process step is 1 to 20 μm.

[0022] Furthermore, the process of depositing the surface dense layer includes five process steps, which are:

[0023] The flow rate of Ar is 20-40 SLPM, and the flow rate of He is 50-70 SLPM. The coating formed in this process step has a quasi-columnar structure, a porosity of 15-20%, and a deposition efficiency of 0.4-0.8 μm / s.

[0024] The flow rate of Ar is 40-60 SLPM, the flow rate of He is 40-60 SLPM, the coating formed in this process step has a quasi-columnar structure, a porosity of 10-15%, and a deposition efficiency of 0.4-0.8 μm / s;

[0025] The flow rate of Ar is 60-80 SLPM, and the flow rate of He is 30-50 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 7-10%, and a deposition efficiency of 0.1-0.2 μm / s.

[0026] The flow rate of Ar is 80-100 SLPM, and the flow rate of He is 20-40 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 3-7%, and a deposition efficiency of 0.1-0.2 μm / s.

[0027] The flow rate of Ar is 100-130 SLPM, and the flow rate of He is 10-30 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 1-3%, and a deposition efficiency of 0.1-0.2 μm / s.

[0028] Furthermore, the thickness of the surface dense layer formed in each process step is regulated by the deposition time.

[0029] Furthermore, in step S200, the powder feeder is a double-sided powder feeder, one side of the double-sided powder feeder is filled with yttria-stabilized zirconia, and the other side is filled with rare earth modified zirconate; the insulation temperature of the tank body of the double-sided powder feeder is 50-100°C, the powder feeding amount on each side of the double-sided powder feeder is 5-20g / min, and the flow rate on each side of the double-sided powder feeder is 5-20SLPM.

[0030] The beneficial effects of the preparation method of the CMAS protective thermal barrier coating based on PS-PVD of the present invention are:

[0031] The preparation method is used to manufacture the above-mentioned PS-PVD-based CMAS protective thermal barrier coating. The thermal barrier coating prepared by the preparation method has good resistance to CMAS corrosion and can reduce the penetration of molten CMAS in practical applications, thereby effectively improving the adaptability of aircraft engines and gas turbine hot end components in harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 A schematic diagram of the structure of a PS-PVD-based CMAS protective thermal barrier coating formed on a high-temperature alloy surface provided in an embodiment of the present invention;

[0034] Figure 2 A cross-sectional morphology diagram of a CMAS protective thermal barrier coating based on PS-PVD provided in an embodiment of the present invention;

[0035] Figure 3 for Figure 2 Cross-sectional morphology of the medium thermal barrier coating after being corroded by CMAS for 2 hours. DETAILED DESCRIPTION

[0036] With the continuous development of gas turbine engine thrust-to-weight ratio and thermal efficiency, the turbine inlet temperature is increasing, and the working environment of hot end components is becoming increasingly harsh. As the main material of hot end components, high-temperature alloy materials have a low melting point and are difficult to cope with the increasing working temperature. Therefore, thermal insulation protection measures must be taken to ensure the safe and reliable operation of aerospace engines, gas turbines and other equipment.

[0037] TBC (Thermal Barrier Coating) is one of the common thermal protection methods. It uses the low thermal conductivity brought by the ceramic layer material and structure to protect the internal high-temperature alloy. It is a low-cost, high-efficiency thermal protection technology that must be adopted for the development of modern aircraft engines, gas turbines and other gas turbine engine technologies. Due to the extremely high temperature at the front end of the turbine of the fourth-generation and above aircraft engines and future-class gas turbines, the long-term temperature resistance requirement of the thermal barrier coating reaches 1300°C or even higher under the action of the cooling structure. Therefore, the traditional thermal barrier coating ceramic insulation layer 8YSZ (6-8wt.% Y2O3-ZrO2) cannot meet the service requirements of long-term high temperature resistance and high temperature stability. 8YSZ and a new generation of rare earth salt compounds are usually used to form a double ceramic layer to improve the overall temperature resistance and thermal insulation performance of the coating. However, since aircraft engines and gas turbines often encounter environmental deposits such as CMAS during operation, the high-temperature corrosion mechanism is complex. Penetration, corrosion and accelerated sintering all lead to the degradation of thermodynamic properties and life shortening of ceramic coatings. The existing thermal barrier coatings have weak resistance to CMAS corrosion and cannot meet the environmental requirements of aircraft engines and gas turbines.

[0038] In the PS-PVD technology for preparing thermal barrier coatings, a high-power plasma spray gun is used to spray at an ultra-low working pressure, which greatly changes the morphology and characteristics of the plasma jet. The plasma gas is heated by the arc in the electrode gun and dissociated into high-energy and high-pressure plasma. When it enters the vacuum chamber through the nozzle, it will expand violently to form a supersonic plasma jet, which can quickly liquefy and gasify the sprayed particles, reach the surface of the sample substrate at high speed, and take the opportunity to achieve solid, liquid, and gas multiphase composite deposition.

[0039] The columnar or quasi-columnar structure coating of PS-PVD is similar to that of EB-PVD, but it is limited by the pure evaporation deposition mode of EB-PVD. When preparing a sealing barrier layer on the surface of the EB-PVD coating, the surface needs to be treated with high finish and then put into the furnace again to prepare the surface sealing barrier layer. The preparation of environmental deposit protective coating is achieved through complex and cumbersome processes and substrate temperature control. PS-PVD has a complex nucleation and continuous deposition mechanism. The solid, liquid and gas phases can all nucleate and grow competitively, and it is extremely difficult to control the structure of the coating. At present, there are no relevant successful cases in the existing literature to achieve continuous process adjustment to ensure the continuous growth of columnar crystals without interruption by the deposition of liquid phase and nanocluster condensed particles, and at the same time, to uniformly transition from a dendrite structure with a certain porosity to a dense structure. The main reason is that the solid, liquid and gas three-phase flow is extremely complex, and there is no online monitoring method that can adapt to the establishment of a rapid regulation mechanism. The PS-PVD preparation of thermal barrier coatings is more based on deposition principles and a large number of explorations and verifications to determine the method, which still needs to overcome technical difficulties such as continuous deposition, high bonding strength, continuous transition from columnar crystals to dense layers, and process control that does not affect the performance of double ceramic layer ultra-high temperature thermal barrier coatings.

[0040] Therefore, the object of the present invention is to provide a PS-PVD-based CMAS protective thermal barrier coating and a preparation method thereof, aiming to solve at least one of the above-mentioned problems.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] like Figure 1 As shown, the PS-PVD-based CMAS protective thermal barrier coating includes a bonding layer, a first ceramic layer, a second ceramic layer and a surface dense layer arranged in sequence from the inside to the outside, wherein the material of the surface dense layer is the same as that of the second ceramic layer, and the porosity of the surface dense layer decreases gradually from the inside to the outside, and the structure of the surface dense layer gradually transitions from the quasi-columnar structure of the inner layer to the layered structure of the outer layer.

[0043] The thermal barrier coating sets the porosity of the surface dense layer to decrease gradually from the inside to the outside, and the structure gradually transitions from the quasi-columnar structure of the inner layer to the layered structure of the outer layer, that is, the surface dense layer is formed by a gradient deposition transition process, which, on the one hand, gradually increases the density of the coating, and on the other hand, allows the second ceramic layer to smoothly transition to the surface dense layer. Therefore, the surface dense layer is more tightly combined with the surface and gap positions of the first ceramic layer and the second ceramic layer in the quasi-columnar structure, and no obvious cracks and pores will appear. In addition, the above transition area is also conducive to alleviating the stress between the surface dense layer and the columnar crystals, reducing the risk of coating peeling.

[0044] By setting the material of the surface dense layer to be consistent with the material of the second ceramic layer, the thermal mismatch stress between the two coatings can be avoided, so that the bonding effect between the coatings is better, and the surface dense layer can better cover the surface of the quasi-columnar structure, and play a certain sealing role in the pore cracks and the pores of the quasi-columnar structure, so that the thermal barrier coating has good resistance to CMAS corrosion, so as to reduce the penetration of molten CMAS in practical applications, thereby effectively improving the adaptability of aircraft engines and gas turbine hot end components in harsh environments.

[0045] In addition, since the material of the surface dense layer is consistent with that of the second ceramic layer, no intermediate processing is required during the switching of the coating deposition process. Instead, it can be directly added to the spraying program to achieve streamlined spraying operations with lower production costs.

[0046] Please continue to refer to Figure 1 In this embodiment, the ratio of the thickness of the first ceramic layer to the thickness of the second ceramic layer is between 0.1:1 and 10:1, and the first ceramic layer to the second ceramic layer are morphologically a continuously grown quasi-columnar structure.

[0047] In this embodiment, the deposition process of the first ceramic layer and the deposition process of the second ceramic layer can be set to have similar processes to achieve continuous deposition in the same columnar crystal structure, so that the first ceramic layer to the second ceramic layer are morphologically continuously grown quasi-columnar structures, avoiding the interruption of columnar crystal growth caused by liquid particles and clusters formed on the surface of the columnar crystal during the deposition conversion of the first ceramic layer and the second ceramic layer, ensuring the continuity of the morphology from the first ceramic layer to the second ceramic layer, and reducing the risk of coating peeling.

[0048] In this embodiment, the thickness of the surface dense layer is between 1 and 50 μm, and the thickness of the surface dense layer is 1% to 20% of the thickness of the thermal barrier coating.

[0049] By limiting the thickness of the surface dense layer within the above range, on the one hand, it is possible to avoid the situation where the protective effect is poor due to the surface dense layer being too thin. On the other hand, it is also possible to avoid the situation where the thermal insulation effect of the thermal barrier coating itself is affected due to the surface dense layer being too thick. In addition, the strain tolerance of the surface dense layer is small, and the thicker the surface dense layer is, the easier it is to crack due to stress.

[0050] In this embodiment, the total thickness of the first ceramic layer and the second ceramic layer is 100-300 μm.

[0051] In this embodiment, the material of the first ceramic layer is yttria-stabilized zirconia (YSZ), and the material of the second ceramic layer and the surface dense layer is rare earth modified zirconate (Gd 0.9 Yb 0.1 )2Zr2O7).

[0052] In addition, this embodiment also provides a method for preparing a CMAS protective thermal barrier coating based on PS-PVD, which is used to prepare the above thermal barrier coating, comprising:

[0053] Step S100: placing a sample to be processed in a vacuum chamber of a PS-PVD device, evacuating the vacuum chamber, and preheating the sample using a plasma flame; wherein the sample includes a substrate and a bonding layer deposited on the outer surface of the substrate;

[0054] Step S200: running a preset spraying program, turning on a powder feeder, and sequentially depositing a first ceramic layer, a second ceramic layer, and a surface dense layer;

[0055] Step S300: close the powder feeder, run the cooling program, gradually reduce the gas flow, and gradually cool down. After the cooling program is completed, the arc is extinguished and the plasma spray gun is closed;

[0056] Step S400: Ar is filled into the vacuum chamber, and after the pressure of the vacuum chamber reaches one atmosphere and the temperature of the sample drops to a preset temperature, the chamber is opened and taken out to complete the preparation.

[0057] The preparation method is used to manufacture the above-mentioned PS-PVD-based CMAS protective thermal barrier coating. The thermal barrier coating prepared by the preparation method has good resistance to CMAS corrosion and can reduce the penetration of molten CMAS in practical applications, thereby effectively improving the adaptability of aircraft engines and gas turbine hot end components in harsh environments.

[0058] It should be noted that, in this embodiment, the material of the bonding layer can be NiCrAlYSi, NiAl or PtAl, etc. For high-temperature alloy substrates of different materials, a bonding layer of the same material can be used. For turbine blades, the material of the bonding layer can be actually selected according to the required performance.

[0059] In the above step S100, the vacuum degree of the vacuum chamber is 10-500 Pa, and the preheating temperature of the sample is 500-800° C. This setting enables the vacuum chamber to have a higher vacuum degree and the sample to have better bonding properties, ensuring the smooth progress of the coating deposition process.

[0060] In the above step S200, the spraying current of the plasma spray gun used for depositing the first ceramic layer, the second ceramic layer and the surface dense layer is 1600-2200A; the Ar flow rate used for depositing the first ceramic layer and the second ceramic layer is 20-40SLPM, and the He flow rate is 50-70SLPM.

[0061] This arrangement makes the processes of the first ceramic layer and the second ceramic layer similar, and they can be deposited continuously in the same columnar crystal structure. For details, please refer to Figure 1 The first ceramic layer grows continuously to the second ceramic layer, which avoids the interruption of columnar crystal growth caused by liquid particles and clusters formed on the surface of the columnar crystal during the coating deposition conversion process.

[0062] It should be noted that in the above step S300, the sample temperature after the thermal barrier coating deposition is about 800°C. By gradually reducing the gas flow rate and gradient cooling, it is possible to avoid large thermal mismatch stresses between any two adjacent coatings and between the coating and the substrate, which may lead to cracks or even coating peeling.

[0063] Among them, gradient cooling can be achieved by gradually reducing the spraying current and reducing the He ratio. By reducing the spraying current and reducing the He ratio, the heat input is gradually reduced to achieve the purpose of slowly cooling the substrate. Specifically, the gradient cooling process can be completed in three stages. The first stage: reduce the spraying current to 1500A, increase Ar to 60SLPM, and reduce He to 20SLPM; the second stage: reduce the spraying current to 1200A, increase Ar to 80SLPM, and reduce He to 10SLPM; the third stage: reduce the spraying current to 1000A, increase Ar to 100SLPM, and reduce He to 0.

[0064] In the above step S200, the process of depositing the surface dense layer may include 3 to 8 process steps, wherein during the entire process of depositing the surface dense layer, the flow rate of Ar is gradually increased from 20 to 40 SLPM to 100 to 130 SLPM, and the flow rate of He is gradually reduced from 50 to 70 SLPM to 10 to 30 SLPM; the thickness of the surface dense layer formed in each process step is 1 to 20 μm.

[0065] That is to say, the process of transition from columnar crystal layer to surface dense layer adopts gradient deposition transition. By gradually increasing the flow rate of Ar and reducing the flow rate of He, the heat input can be gradually reduced, thereby increasing the proportion of liquid phase in the sprayed particles, and using the solidification and deposition of liquid phase particles to form a dense layered structure, so that the density of the surface dense layer is gradually increased from the inside to the outside, and the different structural coatings can be smoothly transitioned, so that the surface dense layer is more tightly combined at the surface of the columnar crystal and the gap position, and no obvious cracks and pores will appear. Moreover, the transition area is also conducive to alleviating the stress between the surface dense layer and the columnar crystal, and preventing the surface dense layer from peeling off. Among them, the thickness of the surface dense layer formed in each process step can be regulated by the deposition time, so as to achieve flexible control of the thermal barrier coating structure.

[0066] In this embodiment, when the deposition time increases, the thickness of the formed surface dense layer increases accordingly; when the deposition time decreases, the thickness of the formed surface dense layer decreases accordingly.

[0067] Specifically, the process of depositing the surface dense layer includes five process steps, which are:

[0068] The flow rate of Ar is 20-40 SLPM, and the flow rate of He is 50-70 SLPM. The coating formed in this process step has a quasi-columnar structure, a porosity of 15-20%, and a deposition efficiency of 0.4-0.8 μm / s.

[0069] The flow rate of Ar is 40-60 SLPM, the flow rate of He is 40-60 SLPM, the coating formed in this process step has a quasi-columnar structure, a porosity of 10-15%, and a deposition efficiency of 0.4-0.8 μm / s;

[0070] The flow rate of Ar is 60-80 SLPM, and the flow rate of He is 30-50 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 7-10%, and a deposition efficiency of 0.1-0.2 μm / s.

[0071] The flow rate of Ar is 80-100 SLPM, and the flow rate of He is 20-40 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 3-7%, and a deposition efficiency of 0.1-0.2 μm / s.

[0072] The flow rate of Ar is 100-130 SLPM, and the flow rate of He is 10-30 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 1-3%, and a deposition efficiency of 0.1-0.2 μm / s.

[0073] By dividing the process of depositing a dense surface layer into five process steps, on the one hand, it can avoid the situation where the transition effect is poor due to too few process steps, and ensure a smooth transition from the columnar crystal structure to the layered structure. On the other hand, it can also avoid the situation where the deposition efficiency is reduced due to too many process steps.

[0074] In this embodiment, the powder feeder is a double-sided powder feeder, wherein one side of the double-sided powder feeder is filled with yttria-stabilized zirconia, and the other side is filled with rare earth modified zirconate; the insulation temperature of the tank body of the double-sided powder feeder is 50-100°C, the powder feeding amount on each side of the double-sided powder feeder is 5-20g / min, and the flow rate on each side of the double-sided powder feeder is 5-20SLPM.

[0075] In the preparation method of the CMAS protective thermal barrier coating based on PS-PVD, the first ceramic layer is deposited by feeding powder on one side of the double-sided powder feeder, and the second ceramic layer and the surface dense layer are deposited by feeding powder on the other side of the double-sided powder feeder. By setting the flow rate of each side of the double-sided powder feeder to 5-20 SLPM, wherein when the flow rate is 5-8 SLPM, the powder feeder flow rate is low, so that the powder fed into the tank body through the double-sided powder feeder is relatively dispersed in the flame flow, and it is more difficult to concentrate in the center of the flame flow for heating, thereby reducing the gasification ratio, and then increasing the relative liquid phase content, so as to achieve the purpose of assisting in adjusting the surface dense layer structure.

[0076] The technical solution of the present invention will be described in detail below through specific embodiments.

[0077] Embodiment 1

[0078] In this embodiment 1, Al2O3 ceramics are used as the coating deposition substrate, and a 60-80 μm YSZ ceramic layer, a 60-80 μm (Gd 0.9 Yb 0.1 )2Zr2O7 ceramic layer, 10-30μm surface dense layer, the cross-sectional morphology of the prepared thermal barrier coating is as follows Figure 2 As shown, the specific steps of preparation are as follows:

[0079] (1) Use a fixture to clamp the sample and fix it to the turntable of the PS-PVD equipment. Set the motion parameters, where the plasma spray gun is perpendicular to the sample surface, the plasma spray gun swings up and down for spraying, the step amount is 200 mm, the swing speed is 400 mm / s, and the spraying distance is 900 mm;

[0080] (2) Turn on the PS-PVD equipment and complete the setting of the spraying program. During the operation, the pressure of the vacuum chamber is maintained at 200 Pa. The spraying current of the plasma spray gun is set to 2200A. During the deposition of the first ceramic layer and the second ceramic layer, the Ar flow rate is 30SLPM and the He flow rate is 60SLPM. The surface dense layer deposition process is divided into 5 process steps. The Ar flow rates of the 5 process steps are 30SLPM, 50SLPM, 80SLPM, 100SLPM and 120SLPM, respectively. The He flow rates of the 5 process steps are 60SLPM, 50SLPM, 40SLPM, 30SLPM and 20SLPM, respectively. During the entire deposition process of the thermal barrier coating, 8SLPM of auxiliary gas O2 is also introduced.

[0081] (3) The powder feeding rate during the spraying process was set to 12 g / min, and the YSZ powder carrier gas flow rate was set to 12 SLPM. 0.9 Yb 0.1 )2Zr2O7 powder carrier gas flow rate was set to 14SLPM;

[0082] (4) When the pressure in the vacuum chamber drops below 10 Pa, backfill Ar to 3500 Pa, turn on the plasma spray gun, and complete the spraying of the first ceramic layer, the second ceramic layer, and the surface dense layer;

[0083] (5) After the thermal barrier coating is prepared, Ar is filled into the vacuum chamber. When the pressure of the vacuum chamber reaches one atmosphere and the sample temperature drops below 100° C., the chamber is opened and the sample is taken out to complete the preparation.

[0084] The surface of the thermal barrier coating prepared in Example 1 was coated with about 50 mg / cm 2 The environmental sediment CMAS with typical marine environment characteristics has the characteristics of the operating environment of ship and carrier-based aircraft gas turbines in terms of composition. After heat treatment at 1250℃ for 2h, the cross-sectional microstructure of the sample is as follows: Figure 3 .Depend on Figure 3 It can be seen that after CMAS infiltration, a dense reaction layer with a thickness of 60 to 80 μm is formed, which significantly slows down the penetration rate of the CMAS melt. Taking the DCL coating without a dense layer as a comparison, under the same conditions, the DCL coating without a dense layer will be completely infiltrated after corrosion, and obvious spheroidization will occur. However, the sample with a dense reaction layer has a CMAS reaction penetration thickness of 60 to 80 μm after continuous heat treatment for 8 hours, and the YSZ layer is less affected, showing good corrosion resistance.

[0085] Embodiment 2

[0086] In the second embodiment, a K403 high temperature alloy substrate is used as a coating deposition substrate, and a 30-50 μm HY3 (NiCrAlYSi) metal bonding layer is deposited on the substrate surface by multi-arc ion plating. Then, a 60-80 μm YSZ ceramic layer, a 60-80 μm (Gd 0.9 Yb 0.1 )2Zr2O7 ceramic layer and 10-30μm surface dense layer, the specific steps of preparation are as follows:

[0087] (1) Use a fixture to clamp the sample and fix it to the turntable of the PS-PVD equipment. Set the motion parameters, where the plasma spray gun is perpendicular to the sample surface, the plasma spray gun swings up and down for spraying, the step amount is 200 mm, the swing speed is 400 mm / s, and the spraying distance is 900 mm;

[0088] (2) Turn on the PS-PVD equipment and complete the setting of the spraying program. During the operation, the pressure of the vacuum chamber is maintained at 200 Pa. The spraying current of the plasma spray gun is set to 2200A. During the deposition of the first ceramic layer and the second ceramic layer, the Ar flow rate is 30SLPM and the He flow rate is 60SLPM. The surface dense layer deposition process is divided into 5 process steps. The Ar flow rates of the 5 process steps are 30SLPM, 50SLPM, 80SLPM, 100SLPM and 120SLPM, respectively. The He flow rates of the 5 process steps are 60SLPM, 50SLPM, 40SLPM, 30SLPM and 20SLPM, respectively. During the entire deposition process of the thermal barrier coating, 8SLPM of auxiliary gas O2 is also introduced.

[0089] (3) The powder feeding rate during the spraying process was set to 12 g / min, and the YSZ powder carrier gas flow rate was set to 12 SLPM. 0.9 Yb 0.1 )2Zr2O7 powder carrier gas flow rate was set to 14SLPM;

[0090] (4) When the pressure in the vacuum chamber drops below 10 Pa, backfill Ar to 3500 Pa, turn on the plasma spray gun, and complete the spraying of the first ceramic layer, the second ceramic layer, and the surface dense layer;

[0091] (5) After the thermal barrier coating is prepared, Ar is filled into the vacuum chamber. When the pressure of the vacuum chamber reaches one atmosphere and the sample temperature drops below 100° C., the chamber is opened and the sample is taken out to complete the preparation.

[0092] The thermal barrier coating prepared in Example 2 was subjected to a CMAS-coupled gas thermal shock test, using an environmental simulation test machine, under the conditions of a thermal barrier coating surface temperature of 1200-1300°C, a substrate temperature of 900-1000°C, and a CMAS addition amount of 0.1 g / min, a thermal cycle shock test was performed. After the test, the average number of impacts of the thermal barrier coating with a surface dense layer in Example 2 was 221 times, which was significantly higher than the 50 times of the sample without a surface dense layer, and the coating life in the CMAS environment was significantly improved.

[0093] In summary, according to the characteristic that the temperature of the PS-PVD flame flow decreases radially along the flame flow, the particle morphology in the flame flow is also different. Since the columnar crystal structure is formed by the condensation of gas phase particles, and the solidification and deposition of liquid phase particles can form a relatively dense layered structure, therefore, by increasing the proportion of liquid phase particles in the flame flow, a dense coating structure can be obtained. The present invention adjusts the process parameters, reduces the input of heat, and makes the surface dense layer deposition mainly based on liquid phase solidification, thereby obtaining a continuous and dense surface structure, which has a significant hindering effect on the penetration of molten CMAS.

[0094] The thermal barrier coating prepared by the preparation method of the CMAS protective thermal barrier coating based on PS-PVD is mainly composed of feather-like quasi-columnar crystals in structure, with certain columnar crystal gaps, and also has high strain tolerance and good thermal insulation performance. The present invention uses a double-sided powder feeder for continuous deposition. When the coating deposition switches from the first ceramic layer to the second ceramic layer, the deposition environment remains unchanged, so that the new coating can continue to grow along the original columnar crystals, reducing the interface effect, thereby making the structure of the obtained thermal barrier coating more stable.

[0095] In addition, during the deposition of the two-layer columnar crystal structure of the first ceramic layer and the second ceramic layer and the surface dense layer, no other operations are required, and the process procedure can be directly switched for continuous deposition, which saves the time of surface treatment and repeated cavity opening and vacuuming, reduces costs and improves work efficiency.

[0096] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

[0097] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0098] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A CMAS protective thermal barrier coating based on PS-PVD, characterized in that: It includes a bonding layer, a first ceramic layer, a second ceramic layer and a surface dense layer which are arranged in sequence from the inside to the outside, wherein the material of the surface dense layer is the same as that of the second ceramic layer, and the porosity of the surface dense layer decreases gradually from the inside to the outside, and the structure of the surface dense layer gradually transitions from the quasi-columnar structure of the inner layer to the layered structure of the outer layer.

2. The thermal barrier coating according to claim 1, characterized in that: The ratio of the thickness of the first ceramic layer to the thickness of the second ceramic layer is between 0.1:1 and 10:1, and the first ceramic layer to the second ceramic layer are morphologically continuously grown quasi-columnar structures.

3. The thermal barrier coating according to claim 1, characterized in that: The thickness of the surface dense layer is between 1 and 50 μm; and / or the thickness of the surface dense layer is 1% to 20% of the thickness of the thermal barrier coating; and / or the material of the first ceramic layer is yttria-stabilized zirconia; and / or the material of the second ceramic layer and the surface dense layer is rare earth modified zirconate.

4. A method for preparing a CMAS protective thermal barrier coating based on PS-PVD, characterized in that: For preparing the thermal barrier coating according to any one of claims 1 to 3, comprising: Step S100: placing a sample to be processed in a vacuum chamber of a PS-PVD device, evacuating the vacuum chamber, and preheating the sample using a plasma flame; wherein the sample includes a substrate and a bonding layer deposited on the outer surface of the substrate; Step S200: running a preset spraying program, turning on a powder feeder, and sequentially depositing a first ceramic layer, a second ceramic layer, and a surface dense layer; Step S300: close the powder feeder, run the cooling program, gradually reduce the gas flow, and gradually cool down. After the cooling program is completed, the arc is extinguished and the plasma spray gun is closed; Step S400: Ar is filled into the vacuum chamber, and after the pressure of the vacuum chamber reaches one atmosphere and the temperature of the sample drops to a preset temperature, the chamber is opened and taken out to complete the preparation.

5. The preparation method according to claim 4, characterized in that: In the step S100, the vacuum degree of the vacuum chamber is 10-500 Pa; the preheating temperature of the sample is 500-800°C.

6. The preparation method according to claim 4, characterized in that: In the step S200, the spraying current of the plasma spray gun used for depositing the first ceramic layer, the second ceramic layer and the surface dense layer is 1600-2200A; the Ar flow rate used for depositing the first ceramic layer and the second ceramic layer is 20-40SLPM, and the He flow rate is 50-70SLPM.

7. The preparation method according to claim 4, characterized in that: In the step S200, the process of depositing the surface dense layer includes 3 to 8 process steps, wherein during the entire process of depositing the surface dense layer, the flow rate of Ar is gradually increased from 20 to 40 SLPM to 100 to 130 SLPM, and the flow rate of He is gradually reduced from 50 to 70 SLPM to 10 to 30 SLPM; the thickness of the surface dense layer formed in each process step is 1 to 20 μm.

8. The preparation method according to claim 7, characterized in that: The process of depositing the surface dense layer includes five process steps, which are: The flow rate of Ar is 20-40 SLPM, and the flow rate of He is 50-70 SLPM. The coating formed in this process step has a quasi-columnar structure, a porosity of 15-20%, and a deposition efficiency of 0.4-0.8 μm / s. The flow rate of Ar is 40-60 SLPM, the flow rate of He is 40-60 SLPM, the coating formed in this process step has a quasi-columnar structure, a porosity of 10-15%, and a deposition efficiency of 0.4-0.8 μm / s; The flow rate of Ar is 60-80 SLPM, and the flow rate of He is 30-50 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 7-10%, and a deposition efficiency of 0.1-0.2 μm / s. The flow rate of Ar is 80-100 SLPM, and the flow rate of He is 20-40 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 3-7%, and a deposition efficiency of 0.1-0.2 μm / s. The flow rate of Ar is 100-130 SLPM, and the flow rate of He is 10-30 SLPM. The coating formed in this process step has a solid-liquid-gas mixed deposition layered structure, a porosity of 1-3%, and a deposition efficiency of 0.1-0.2 μm / s.

9. The preparation method according to claim 7, characterized in that: The thickness of the surface dense layer formed in each process step is controlled by the deposition time.

10. The preparation method according to claim 4, characterized in that: In step S200, the powder feeder is a double-sided powder feeder, one side of the double-sided powder feeder is filled with yttria-stabilized zirconia, and the other side is filled with rare earth modified zirconate; the insulation temperature of the tank body of the double-sided powder feeder is 50-100°C, the powder feeding amount on each side of the double-sided powder feeder is 5-20g / min, and the flow rate on each side of the double-sided powder feeder is 5-20SLPM.

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