A thermal barrier coating containing a v-shaped vertical crack, a preparation method and a preparation device

Abstract

The application provides a V-shaped vertical crack thermal barrier coating, a preparation method and a preparation device, which comprise an atmospheric plasma spraying unit, a preheating unit, a cooling unit and a fixing unit; the atmospheric plasma spraying unit is provided with a spray gun, the preheating unit is provided with a laser emission head, and the cooling unit is provided with a liquid carbon dioxide injection pipe; the fixing unit is provided with a movable clamp, and the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are sequentially fixed on the clamp along the moving direction of the clamp. The deposition process of the ceramic coating is divided into N rounds, and each round is deposited n times; at the n-th time of deposition in each round, the deposited ceramic coating is instantaneously heated and cooled by the preheating unit and the cooling unit, so that the tensile stress in the ceramic coating is formed to generate a through crack; in the next round of deposition, the ceramic droplets at the crack tend to deposit away from the crack, so that the width of the newly formed crack is greater than the width of the crack in the last round, and the crack finally presents a V-shaped crack with a wide upper part and a narrow lower part.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing, and in particular to a thermal barrier coating containing V-shaped vertical cracks, a preparation method and a preparation device. Background Art

[0002] Thermal barrier coatings (TBCs) are widely used to protect the hot-end metal components of aircraft engines and gas turbines. Their primary function is to effectively insulate and reduce the thermal impact of high ambient temperatures on these components, ensuring the long-term, stable service life of high-temperature metal components such as combustion chambers and turbine blades. TBCs typically consist of a dual-layer structure: a metallic bond layer adhered to the surface of the hot-end metal component and a ceramic insulation layer. The ceramic insulation layer primarily achieves its thermal insulation effect through its low thermal conductivity. Currently, the most widely used ceramic coating materials include yttria-stabilized zirconia (YSZ) and rare earth zirconates. These coatings are primarily deposited using methods such as electron beam physical vapor deposition (EB-PVD) and plasma spraying.

[0003] Aircraft engines and gas turbines experience temperature fluctuations from room temperature to over 2000K during operation. Due to the inherent brittleness of ceramic materials and the difference in thermal expansion coefficients between ceramics and the high-temperature alloy substrates used in the hot-end components, ceramic insulation layers are prone to delamination and peeling due to drastic temperature fluctuations. Therefore, the thermal shock resistance of thermal barrier coatings is an important indicator that determines their service life. To this end, one of the important solutions in the industry is to introduce cracks or gaps perpendicular to the coating surface within the ceramic coating. Their function is similar to that of expansion joints on concrete floors. When the temperature changes, they can effectively alleviate strain and reduce stress, significantly reducing the driving force for coating peeling. The ceramic insulation layer of the thermal barrier coating prepared by the EB-PVD method itself exhibits columnar crystal characteristics, with self-generated gaps between the columnar crystals, resulting in excellent thermal shock resistance, but the manufacturing cost is extremely high. The ceramic thermal insulation layer prepared by atmospheric plasma spraying (APS) presents a layered structure parallel to the coating direction. Although it has better thermal insulation performance than the ceramic coating prepared by EB-PVD, its thermal shock resistance is poor due to the absence of cracks or gaps perpendicular to the coating surface.

[0004] Therefore, how to introduce cracks or gaps perpendicular to the coating surface into the ceramic thermal insulation layer prepared by atmospheric plasma spraying to obtain a thermal barrier coating ceramic coating with both high strain relaxation effect and high thermal insulation effect is currently a hot topic of research. Summary of the Invention

[0005] In response to the above problems existing in the prior art, the present invention provides a thermal barrier coating containing V-shaped vertical cracks, a preparation method and a preparation device to obtain a thermal barrier coating ceramic coating with both high strain relaxation effect and high thermal insulation effect.

[0006] The specific content of the invention is as follows:

[0007] In a first aspect, the present invention provides a device for preparing a thermal barrier coating containing V-shaped vertical cracks, comprising: an atmospheric plasma spraying unit, a preheating unit, a cooling unit, and a fixing unit;

[0008] The atmospheric plasma spraying unit is provided with a spray gun for depositing ceramic powder onto the surface of the high-temperature alloy with the metal bonding layer to form a ceramic coating;

[0009] The preheating unit is provided with a laser emission head for providing instantaneous high temperature to instantaneously heat the ceramic coating;

[0010] The cooling unit is provided with a liquid carbon dioxide injection pipe for providing instantaneous low temperature to instantaneously cool the ceramic coating;

[0011] The fixing unit is provided with a movable clamp. Along the direction of movement of the clamp, the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are fixed on the clamp in sequence. Through the movement of the clamp, the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are moved synchronously.

[0012] Optionally, the liquid carbon dioxide injection pipe, the laser emission head, and the spray gun are sequentially fixed on the fixture along the direction in which the fixture moves, including:

[0013] The horizontal distance between the center of the liquid carbon dioxide injection pipe and the center of the laser emission head is between 20-45 mm; the horizontal distance between the center of the laser emission head and the center of the spray gun is between 60-100 mm.

[0014] Optionally, the diameter of the laser spot emitted by the laser emitter is larger than the diameter of the plasma beam ejected by the spray gun; the diameter of the liquid carbon dioxide injection tube is larger than the diameter of the plasma beam ejected by the spray gun.

[0015] In a second aspect, the present invention provides a method for preparing a thermal barrier coating containing V-shaped vertical cracks, wherein the method is applicable to the preparation device described in the first aspect, comprising:

[0016] Step 1: Divide the deposition process of the ceramic coating into N rounds according to the thickness of the ceramic coating, with the number of deposition passes in each round being n;

[0017] Step 2: Turn on the atmospheric plasma spraying unit and use a spray gun to deposit ceramic powder n times on the surface of the high-temperature alloy with the metal bonding layer;

[0018] Step 3, when the n-th deposition is performed, the preheating unit and the cooling unit are turned on, the laser spot emitted by the laser emitting head of the preheating unit and the liquid carbon dioxide beam emitted by the liquid carbon dioxide jetting pipe of the cooling unit act on the ceramic coating formed by deposition at the same time, and the ceramic coating is instantaneously heated and cooled, so that the tensile stress generated by the instantaneous heating and cooling forms the through cracks in the ceramic coating, thereby completing the first round of deposition;

[0019] Step 4, the above steps 2-3 are repeated until the N-th round of deposition of the ceramic coating is completed, so that the total thickness of the deposited ceramic coating reaches the target value; when a new round of deposition is performed on the surface of the ceramic coating formed in the last round of deposition, due to the edge effect, the ceramic droplets tend to deposit away from the cracks, so that the crack width generated in the new round of deposition is greater than that generated in the last round of deposition, and finally the vertical cracks in the ceramic coating present a V-shaped pattern with a wide upper part and a narrow lower part.

[0020] Optionally, the ceramic powder is yttrium-stabilized zirconia (YSZ), rare earth tantalate or rare earth zirconate.

[0021] Optionally, the spraying power of the spray gun is 36-45 kW.

[0022] The power of the laser is 1.5-6 kW, and the instantaneous high temperature provided by the laser is 600-1000℃.

[0023] The beam flow of the liquid carbon dioxide is 0.1-1.2 L / min, and the instantaneous low temperature provided by the liquid carbon dioxide beam reduces the surface temperature of the ceramic coating to 200-300℃.

[0024] Optionally, N is 1-15, and n is 1-10.

[0025] Optionally, the thickness of the ceramic coating formed by each round of deposition is 10-150 μm.

[0026] In a third aspect, the application provides a thermal barrier coating layer containing V-shaped vertical cracks, which is obtained by the preparation method of the second aspect.

[0027] Optionally, the porosity of the ceramic coating of the thermal barrier coating layer containing V-shaped vertical cracks is greater than 8%, and the thermal conductivity is 0.6-1.2 W / Km.

[0028] Compared with the prior art, the application has the following advantages:

[0029] The present invention provides a device for preparing a thermal barrier coating with V-shaped vertical cracks, comprising: an atmospheric plasma spraying unit, a preheating unit, a cooling unit, and a fixing unit; the atmospheric plasma spraying unit is provided with a spray gun for spraying and forming a ceramic coating; the preheating unit is provided with a laser emitter head for providing instantaneous high temperature to instantaneously heat the ceramic coating; the cooling unit is provided with a liquid carbon dioxide injection pipe for providing instantaneous low temperature to instantaneously cool the ceramic coating; the fixing unit is provided with a movable fixture, and the liquid carbon dioxide injection pipe, the laser emitter head, and the spray gun are fixed to the fixture in sequence along the direction of movement of the fixture, and the movement of the fixture achieves synchronous movement of the liquid carbon dioxide injection pipe, the laser emitter head, and the spray gun. The present invention introduces a laser beam instantaneous heating and liquid carbon dioxide instantaneous cooling unit during the atmospheric plasma spraying process, utilizing the high-amplitude tensile stress generated by rapid heating and rapid cooling to introduce vertical cracks in the ceramic thermal barrier coating, thereby achieving the preparation of a thermal barrier coating with V-shaped vertical cracks.

[0030] The application also provides a preparation method of the V-shaped vertical crack thermal barrier coating, which comprises the following steps: decomposing the deposition process of the ceramic coating into N rounds, depositing n times in each round, and instantaneously heating and cooling the formed ceramic coating by means of the preheating unit and the cooling unit in the n-th deposition of each round, so that the tensile stress generated by the instant heating and cooling forms a through crack in the ceramic coating; due to the existence of the through crack formed in the previous round of deposition, the ceramic droplet at the crack tends to deposit away from the crack in the new round of deposition, so that the crack width of the ceramic coating formed in the new round of deposition is greater than that of the ceramic coating formed in the previous round of deposition, and finally the vertical crack in the ceramic coating presents a V-shaped structure with the upper part being wide and the lower part being narrow, and the V-shaped vertical crack has a higher strain tolerance than the equal-width vertical crack. Since the ceramic coating formed in each round of deposition will generate a vertical crack, the application can generate a vertical crack in the ceramic coating with a thickness of 0.1 mm, which is wider than the existing ceramic coating preparation method of the thermal barrier coating with a vertical crack, and the thickness of the ceramic coating usually needs to be greater than 0.4-0.5 mm (in order to accumulate a high level of tensile stress to ensure that a vertical crack is generated in the ceramic coating), so the application has a wider range of application; meanwhile, the ion spraying power used in the application is 36-45 kW, which is lower than the high-power (>100 kW) plasma spraying equipment required in the existing ceramic coating preparation method of the thermal barrier coating with a vertical crack, so that the workpiece temperature in the spraying process is at a high level, and the equipment cost is significantly reduced. In addition, in each round of deposition, the laser spot emitted by the laser emitting head of the preheating unit heats the ceramic coating to a high temperature and then further cools it to a lower temperature by liquid carbon dioxide, so that the surface temperature of the deposited ceramic coating is low (200-300 DEG C), and thus the wetting effect of the ceramic droplet on the surface in the subsequent round of deposition is not affected, and the porosity of the newly deposited ceramic coating is not reduced, so that the thermal barrier coating ceramic coating with high strain relaxation effect and high thermal insulation effect is obtained. The application provides technical support for the low-cost preparation of high-thermal-insulation and long-life thermal barrier coatings. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.

[0032] Figure 1 A device structure schematic diagram for preparing the thermal barrier coating with a V-shaped vertical crack is shown.

[0033] Figure 2A flow chart of a method for preparing a V-shaped vertical crack-containing thermal barrier coating is shown;

[0034] Figure 3 A scanning electron microscope characterization diagram of the V-shaped vertical crack-containing thermal barrier coating is shown.

[0035] Figure 4 A thermal conductivity change curve of the V-shaped vertical crack-containing thermal barrier coating is shown.

[0036] BRIEF DESCRIPTION OF DRAWINGS

[0037] 1 - spray gun; 2 - laser emitting head; 3 - liquid carbon dioxide injection pipe; 4 - clamp. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, any person under the inspiration of the present application or combining the present application with other prior art features to obtain any product same or similar to the present application falls within the protection scope of the present application. In addition, all other embodiments obtained by the ordinary skilled in the art without carrying out creative labor fall within the protection scope of the present application.

[0039] The specific experimental steps or conditions not mentioned in the embodiments can be carried out according to the conventional experimental steps or conditions described in the prior art in the field. The reagents and other instruments not mentioned by the manufacturer are all conventional reagent products that can be obtained by purchase. In addition, the drawings are only schematic diagrams of the embodiments of the present application, and are not necessarily drawn to scale. The same reference signs in the drawings represent the same or similar parts, and thus repeated description thereof will be omitted. Some block diagrams shown in the drawings are functional entities, and do not necessarily correspond to physically or logically independent entities.

[0040] The techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the present specification when appropriate.

[0041] In the description of the present application, it should be understood that the use of the words "first", "second", and the like to qualify elements is only for the convenience of distinguishing the corresponding elements, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as limiting the scope of protection of the present application.

[0042] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] Before describing in detail the thermal barrier coating containing V-shaped vertical cracks, the preparation method and the preparation device provided by the present invention, it is necessary to describe the related technologies as follows:

[0044] In order to introduce periodic vertical cracks in the plasma sprayed ceramic insulation layer and improve its thermal shock resistance, the industry has made a lot of attempts. The main principle is to take advantage of the preferential shrinkage of the ceramic coating when the coating is cooled from high temperature to low temperature after spraying, so that a higher tensile thermal stress is generated inside the ceramic coating, causing cracking inside the ceramic coating and generating periodic vertical cracks. In order to generate sufficiently large tensile thermal stress, the main strategies are: 1) increase the temperature when the spraying is completed, thereby increasing the temperature range when the ceramic coating is cooled; 2) increase the thickness and density of the coating to increase the tensile stress level; 3) select ceramics that are more prone to cracking as the insulation material, so that the ceramic insulation layer is more likely to crack under the same tensile stress level.

[0045] Based on this strategy, the Chinese patent (CN113862603A) uses a high-power plasma spray gun (current 2000-2600A, compared to 500-800A for conventional plasma spraying) and sprays in a vacuum chamber (with only radiation heat exchange). This allows the coating to maintain a higher temperature, allowing it to span a wider temperature range when cooled to room temperature, thereby increasing stress levels. Chinese patents (CN109763090A, CN116770210A, and CN116497306A) require preheating the substrate to 900-1400°C, 200-500°C, and 200-800°C, respectively. Materials with higher brittleness than YSZ, such as rare earth tantalates, are used, and coating thicknesses typically reach 500μm. Some even use heat sources such as lasers to melt the ceramic coating after spraying, and use the tensile stress generated by the rapid solidification, cooling and shrinkage of the ceramic to introduce cracks into the ceramic coating (CN113564592A).

[0046] Although the above-mentioned strategies can produce periodic vertical cracks in the ceramic coating and improve the impact resistance of the ceramic thermal barrier layer, the above-mentioned solutions have certain problems. On the one hand, when the ceramic coating is deposited at a higher preheating temperature, the porosity of the ceramic coating is significantly reduced due to the reduced solidification rate, reduced viscosity, and improved wettability of the ceramic droplets when colliding on the substrate surface, thus significantly increasing the thermal conductivity of the ceramic coating and reducing the thermal insulation effect. On the other hand, when using a high-power plasma spray gun (> 150 kW) and spraying in a vacuum chamber, the equipment cost and operating cost are significantly increased. When the ceramic coating is too thick, although a higher tensile stress can be generated in the coating during the cooling process of coating preparation, causing the coating to crack, but a higher level of compressive stress can also be generated during the heating process, causing the coating to easily peel off.

[0047] Therefore, the present application aims to develop a new method that does not affect the porosity of the ceramic coating while quickly introducing vertical cracks in the plasma sprayed ceramic thermal barrier layer. The specific implementation content is as follows:

[0048] Figure 1 The device structure schematic diagram for preparing the thermal barrier coating containing V-shaped vertical cracks provided by the embodiment of the present application is shown in FIG. 1. Figure 1 As shown in FIG. 1, the device structure schematic diagram for preparing the thermal barrier coating containing V-shaped vertical cracks provided by the embodiment of the present application includes an atmospheric plasma spraying unit, a preheating unit, a cooling unit, and a fixing unit. The atmospheric plasma spraying unit is provided with a spray gun 1 for depositing ceramic powder on the surface of the high-temperature alloy with a metal bonding layer to form a ceramic coating. The preheating unit is provided with a laser emitting head 2 for providing a transient high temperature to instantaneously heat the ceramic coating. The cooling unit is provided with a liquid carbon dioxide injection pipe 3 for providing a transient low temperature to instantaneously cool the ceramic coating. The fixing unit is provided with a movable clamp 4. The liquid carbon dioxide injection pipe 3, the laser emitting head 2, and the spray gun 1 are sequentially fixed on the clamp 4 along the direction of the clamp movement. By moving the clamp 4, the synchronous movement of the liquid carbon dioxide injection pipe 3, the laser emitting head 2, and the spray gun 1 is realized.

[0049] In specific implementation, the liquid carbon dioxide injection pipe 3, the laser emitting head 2, and the spray gun 1 are all located above the high-temperature alloy with a metal bonding layer, so as to deposit ceramic powder on the surface of the high-temperature alloy with a metal bonding layer to form a ceramic coating. The liquid carbon dioxide injection pipe 3, the laser emitting head 2, and the spray gun 1 are fixed on the clamp 4 at a certain interval, and the three are kept synchronous movement during the deposition process of the ceramic coating. That is, when the spray gun 1 sprays ceramic powder, the liquid carbon dioxide injection pipe 3 and the laser emitting head 2 move with the spray gun 1.

[0050] In this embodiment, the deposition process of the ceramic coating is determined based on the thickness of the ceramic coating. Specifically, if the desired thickness of the ceramic coating is A (0.15-2.2 mm), the deposition process is divided into N rounds, with n deposition passes in each round. Then, after N rounds, a total of N*n deposition passes are performed to obtain a ceramic coating with a thickness of A (N is between 1-15, n is between 1-10, and the thickness of the ceramic coating formed by each deposition round is between 10-150 μm). Furthermore, during each deposition round, during the 1st to n-1st deposition passes, only the atmospheric plasma spray unit and the fixing unit are activated. The spray gun 1 deposits ceramic powder according to the movement trajectory of the fixture 4. During the nth deposition pass, the preheating unit and the cooling unit are further activated. As the spray gun 1 deposits the ceramic powder for the nth pass, the laser head 2 located behind it emits laser light, instantaneously heating the deposited ceramic coating with the high heat released by the laser spot. Subsequently, the liquid carbon dioxide injection pipe 3 located behind the laser head 2 injects liquid carbon dioxide. By absorbing heat from liquid carbon dioxide, the temperature of the ceramic coating drops sharply, generating tensile stress within the ceramic coating during the instantaneous heating and cooling process, thereby forming through-cracks. Due to the presence of through-cracks formed in the previous round of deposition, in the new round of deposition, the ceramic droplets at the cracks tend to deposit away from the cracks, making the crack width of the ceramic coating formed in the new round of deposition greater than the crack width of the ceramic coating formed in the previous round of deposition. Ultimately, the vertical cracks in the ceramic coating appear V-shaped, wide at the top and narrow at the bottom, and have a higher strain tolerance than vertical cracks of equal width. Since vertical cracks are generated within the ceramic coating formed in each round of deposition, the present invention can produce vertical cracks in ceramic coatings with a thickness as low as 0.1 mm. This is compared to existing methods for preparing ceramic thermal barrier coatings containing vertical cracks, where the ceramic coating thickness generally needs to be greater than 0.4-0.5 mm (to accumulate a higher level of tensile stress to ensure the generation of vertical cracks within the ceramic coating), and has a wider range of applications.

[0051] Furthermore, existing methods for preparing ceramic layers with vertical crack thermal barrier coatings require preheating the substrate to temperatures above 500°C. This makes effective preheating and maintaining a stable preheating temperature throughout the spraying process extremely difficult for complex blades or large combustion chambers. The present invention eliminates the need for preheating the substrate and directly deposits ceramic powder onto the surface of the high-temperature alloy with a metal bonding layer. Furthermore, the present invention utilizes an ion spray power of 36-45kW, significantly reducing equipment costs compared to existing methods for preparing ceramic layers with vertical crack thermal barrier coatings, which require high-power (>100 kW) plasma spray equipment to maintain a high workpiece temperature during the spraying process. Furthermore, during each deposition cycle, the laser spot emitted by the preheating unit's laser emitter heats the ceramic coating to a high temperature before being further cooled to a lower temperature by liquid carbon dioxide. This keeps the surface temperature of the deposited ceramic coating relatively low (200-300°C), thus preventing wetting of the ceramic droplets with the surface during subsequent deposition cycles and reducing the porosity of the newly deposited ceramic coating. This results in a thermal barrier coating with both high strain relaxation and high thermal insulation properties. This technology provides technical support for the cost-effective preparation of high-insulation, long-life thermal barrier coatings.

[0052] In some embodiments, the density of V-shaped cracks in the ceramic coating can be controlled by adjusting the distance between the liquid carbon dioxide injection tube 3, the laser emission head 2 and the spray gun 1, as well as parameters such as the beam flow rate of the liquid carbon dioxide, the power of the laser and the spraying power of the spray gun 1. Generally, the horizontal distance between the center of the liquid carbon dioxide injection tube and the center of the laser emission head is between 20-45 mm; the horizontal distance between the center of the laser emission head and the center of the spray gun is between 60-100 mm. It should be noted that the diameter of the laser spot emitted by the laser emission head 2 must be larger than the diameter of the plasma beam ejected by the spray gun 1; the diameter of the liquid carbon dioxide injection tube 3 is larger than the diameter of the plasma beam ejected by the spray gun 1 to ensure that instantaneous heating and instantaneous cooling can cover the ceramic coating instantaneously deposited by the spray gun 1; the spraying power of the spray gun 1 is between 36-45 kW, the spraying distance is between 60-150 mm, the diameter of the plasma powder beam deposition spot is between 10-50 mm, and the moving speed of the spray gun 1 is between 400-800 mm / s; the power of the laser is between 1.5-6 kW, and the instantaneous high temperature provided by the laser is between 600-1000°C; the beam flow rate of the liquid carbon dioxide is between 0.1-1.2 L / min, and the instantaneous low temperature provided by the liquid carbon dioxide beam reduces the surface temperature of the ceramic coating to between 200-300°C.

[0053] In this embodiment, the ceramic coating formed after N rounds of deposition has a porosity greater than 8% and a thermal conductivity between 0.6 and 1.2 W / Km.

[0054] The embodiment is based on Figure 1 The device structure schematic diagram is shown, the device is assembled, and the device is used to prepare the V-shaped vertical crack thermal barrier coating, Figure 2 The method flow chart for preparing the V-shaped vertical crack thermal barrier coating is shown, and the method comprises the following steps. Figure 2 The method flow chart for preparing the V-shaped vertical crack thermal barrier coating is shown, and the method comprises the following steps.

[0055] Step 1, according to the thickness of the ceramic coating, the deposition process of the ceramic coating is divided into N rounds, and the number of deposition passes in each round is n.

[0056] Step 2, the atmospheric plasma spraying unit is started, and the n passes of ceramic powder deposition are performed on the surface of the high-temperature alloy with the metal bonding layer using the spray gun.

[0057] Step 3, when the n-th pass of deposition is performed, the preheating unit and the cooling unit are started, the laser spot emitted by the laser emitting head of the preheating unit and the liquid carbon dioxide beam emitted by the liquid carbon dioxide jet pipe of the cooling unit simultaneously act on the ceramic coating formed by deposition, and the ceramic coating is instantaneously heated and cooled, the tensile stress generated by the instantaneous heating and cooling forms through cracks in the ceramic coating, thereby completing the first round of deposition.

[0058] Step 4, the above steps 2-3 are repeated until the N-th round of ceramic coating deposition is completed, so that the total thickness of the deposited ceramic coating reaches the target value; when the new round of deposition is performed on the surface of the ceramic coating formed in the last round of deposition, due to the edge effect, the ceramic droplets tend to deposit away from the cracks, so that the crack width generated by the ceramic coating formed in the new round of deposition is greater than the crack width generated by the ceramic coating formed in the last round of deposition, and finally the vertical cracks in the ceramic coating present a V-shaped pattern with the width increasing from top to bottom.

[0059] In some embodiments, the ceramic powder used for deposition can be selected from yttria-stabilized zirconia YSZ, rare earth tantalate or rare earth zirconate. The ceramic powder can be sintered broken ceramic powder with a particle size of 10-35 μm or hollow spherical ceramic powder with a particle size of 50-75 μm; before deposition, the ceramic powder must be dried in a vacuum oven for standby use. The drying temperature is between 150-200℃.

[0060] In order for those skilled in the art to more clearly understand the present application, the following examples are used to illustrate the V-shaped vertical crack thermal barrier coating, the preparation method and the preparation device.

[0061] Example 1:

[0062] A 3mm-thick Mar-M247 nickel-based superalloy was used as the substrate, and hollow spherical YSZ powder with a particle size of 50-75μm was used as the raw material for the ceramic thermal insulation layer. During the spraying process, the surface temperature distribution was monitored using an infrared thermal imager. First, a NiCoCrAlY metal bonding layer with a thickness of 95-130μm was deposited on the sandblasted Mar-M247 superalloy surface using a JP8000 high-velocity fuel oxygen spraying machine.

[0063] Then, the YSZ powder was placed in a vacuum oven at 150°C for 2 hours for drying. Figure 2 The following preparation process was used to prepare a ceramic coating with a target thickness of 150 μm. First, the center-to-center distance d1 of the spray gun 1 from the laser emitter 2 was adjusted to 85 mm, and the center-to-center distance d2 of the liquid carbon dioxide injection tube 3 from the laser emitter 2 was adjusted to 35 mm. The APS spraying parameters were set as follows: spray power 42 kW, argon flow rate 45 SLPM, hydrogen flow rate 10 SLPM, powder feed gas flow rate 5 SLPM, powder feed rate 30 g / min, spray distance 80 mm, plasma powder beam deposition spot diameter 15 mm, and travel rate 600 mm / s. A square-spot fiber laser was used for rapid preheating. The spot had a length of 17 mm and a width of 2 mm. The laser power was set to 3 kW. The liquid carbon dioxide flow rate was 0.85 L / min, and the distance from the tube end to the substrate was adjusted to ensure an effective cooling zone diameter of 18-20 mm.

[0064] Preliminary verification tests showed that under these APS spraying conditions, a single-pass YSZ coating produced a thickness of approximately 13 μm. Therefore, the total number of spray passes was 150 / 13, rounded up to 12. In this embodiment, ceramic coating deposition was performed in two passes (N = 2), with the spray gun scanning the substrate surface six times in each pass. The YSZ coating achieved a thickness of 78 μm. During the sixth spray pass, the laser emitter 2 and the liquid carbon dioxide injection tube 3 were simultaneously activated to ensure that vertical cracks were penetrated.

[0065] Temperature test results show that when laser preheating and liquid carbon dioxide cooling are not used, the substrate surface temperature is between 120-230°C; when laser preheating and liquid carbon dioxide cooling are used, the instantaneous temperature of the laser preheating area reaches 870°C, and the temperature drops to 220°C after liquid carbon dioxide cooling.

[0066] Figure 3 The scanning electron microscope characterization image of the thermal barrier coating containing V-shaped vertical cracks provided by the embodiment of the present invention is shown. Figure 3As shown, the YSZ ceramic layer is uniform in thickness, the coating and the metal bonding layer are well combined, vertical V-shaped cracks are formed in the coating, and the density of the V-shaped cracks in the coating is about 2.7 / mm by image method. On the other hand, there are a large number of pores in the coating, and the porosity of the YSZ ceramic layer is tested by image method, and the result shows that the average porosity is about 6.7%.

[0067] In addition, in the same way, a free coating with a diameter of 12.7 mm and a thickness of 0.8 mm is prepared, and the influence of the hydrogen flow in the APS parameter setting on the thermal conductivity of the coating is studied (the thermal conductivity of the coating is tested by laser flash method).

[0068] Figure 4 The thermal conductivity variation curve of the thermal barrier coating with V-shaped vertical cracks provided by the embodiment of the present application is shown, and the result is as shown in Figure 4 The thermal conductivities of the ceramic coatings prepared at different hydrogen flows are at a relatively low level, about 50% of the sintered bulk material, which meets the requirement of the thermal barrier ceramic insulating layer.

[0069] Example 2

[0070] Inconel718 nickel-based superalloy with a thickness of 3 mm is used as the substrate, and the smelted and crushed YSZ powder with a particle size of 10-30 μm is used as the raw powder of the ceramic insulating layer. During the spraying process, the surface temperature distribution is detected by using an infrared thermal imager. First, a CoNiCrAlTaY metal bonding layer with a thickness of 95-130 μm is prepared on the sandblasted Inconel718 superalloy surface by using a JP8000 type supersonic flame spraying.

[0071] Subsequently, the YSZ powder is placed in a vacuum oven at 180°C for 2h for drying. The ceramic coating of the present application is prepared according to the principle as shown in Figure 1 The target thickness of the ceramic coating is 500 μm. First, the center distance d1 between the center of the spray gun 1 in the device and the center of the laser emitting head 2 is adjusted to 100 mm, and the center distance d2 between the center of the liquid carbon dioxide jet pipe 3 and the center of the laser emitting head 2 is adjusted to 25 mm; the APS spraying parameters are set as follows: spraying power 45 kW, argon flow 50 SLPM, hydrogen flow 12 SLPM, powder feeding gas flow 5 SLPM, powder feeding rate 30 g / min, spraying distance 100 mm, diameter of the plasma powder beam deposition spot 15 mm, and moving rate 600 mm / s. A square spot fiber laser is selected for rapid preheating, the length direction distance of the square spot is 17 mm, the width is 2 mm, and the laser power is set to 4.5 kW; the liquid carbon dioxide flow is 1.4 L / min, and the distance between the pipe port and the substrate is adjusted to make the effective cooling area diameter 18-20 mm.

[0072] Preliminary verification tests showed that under these APS spraying conditions, a single-pass YSZ coating produced a thickness of approximately 15 μm. Therefore, the total number of spray passes was 500 / 15, rounded up to 33. In this example, the ceramic coating was deposited in seven passes (N = 7), with the spray gun scanning the substrate surface five times in each pass. The YSZ coating achieved a thickness of 75 μm. During the fifth spray pass, the laser head 2 and the liquid carbon dioxide injection tube 3 were simultaneously activated to ensure that vertical cracks were penetrated. Spraying was stopped after a total of 33 passes.

[0073] Temperature test results show that when laser preheating and liquid carbon dioxide cooling are not used, the substrate surface temperature is between 150-260°C; when laser preheating and liquid carbon dioxide cooling are used, the instantaneous temperature of the laser preheating area reaches 980°C, and the temperature drops to 240°C after liquid carbon dioxide cooling.

[0074] The scanning electron microscopy results of the thermal barrier coating ceramic insulation layer obtained in this example are similar to those in Example 1 and are not repeated in the accompanying figures. The YSZ ceramic layer exhibits uniform thickness and good adhesion to the metal bonding layer. Increased laser power and liquid carbon dioxide flow rate resulted in more vertical V-shaped cracks within the coating compared to Example 1. Image analysis revealed a density of approximately 4.2 V-shaped cracks per mm within the coating. Furthermore, the coating exhibited a significant number of pores, and the porosity of the YSZ ceramic layer was measured using image analysis, revealing an average porosity of approximately 10.2%.

[0075] In addition, this embodiment uses the same means and the strategy of increasing the number of spraying passes to prepare a free coating with a diameter of 12.7 mm and a thickness of 0.65 mm, and uses the laser flash method to test the thermal conductivity of the coating. The room temperature thermal conductivity is about 0.98 W / Km, which is at a relatively low level and meets the requirements of the ceramic insulation layer of the thermal barrier coating.

[0076] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0077] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0078] The above is a detailed introduction to a thermal barrier coating containing V-shaped vertical cracks, a preparation method and a preparation device provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for preparing a thermal barrier coating containing V-shaped vertical cracks, characterized in that: include: Atmospheric plasma spraying unit, preheating unit, cooling unit and fixing unit; The atmospheric plasma spraying unit is provided with a spray gun for depositing ceramic powder onto the surface of the high-temperature alloy with the metal bonding layer to form a ceramic coating; The preheating unit is provided with a laser emission head for providing instantaneous high temperature to instantaneously heat the ceramic coating; The cooling unit is provided with a liquid carbon dioxide injection pipe for providing instantaneous low temperature to instantaneously cool the ceramic coating; The fixing unit is provided with a movable clamp. Along the direction of movement of the clamp, the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are fixed on the clamp in sequence. Through the movement of the clamp, the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are moved synchronously.

2. The device for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 1, characterized in that: Along the direction of movement of the fixture, the liquid carbon dioxide injection pipe, the laser emission head and the spray gun are fixed to the fixture in sequence, including: The horizontal distance between the center of the liquid carbon dioxide injection pipe and the center of the laser emission head is between 20-45 mm; the horizontal distance between the center of the laser emission head and the center of the spray gun is between 60-100 mm.

3. The device for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 1, characterized in that: The diameter of the laser spot emitted by the laser emitting head is larger than the diameter of the plasma beam ejected by the spray gun; the diameter of the liquid carbon dioxide ejection pipe is larger than the diameter of the plasma beam ejected by the spray gun.

4. A method for preparing a thermal barrier coating containing V-shaped vertical cracks, characterized in that: The preparation method is applicable to the preparation device according to any one of claims 1 to 3, comprising: Step 1: Divide the deposition process of the ceramic coating into N rounds according to the thickness of the ceramic coating, with the number of deposition passes in each round being n; Step 2: Turn on the atmospheric plasma spraying unit and use a spray gun to deposit ceramic powder n times on the surface of the high-temperature alloy with the metal bonding layer; Step 3: During the nth deposition pass, the preheating unit and the cooling unit are turned on. The laser spot emitted by the laser emitter of the preheating unit and the liquid carbon dioxide beam ejected by the liquid carbon dioxide ejection pipe of the cooling unit simultaneously act on the deposited ceramic coating, and instantaneously heat and instantaneously cool the ceramic coating. The tensile stress generated by the instantaneous heating and instantaneous cooling forms a penetrating crack in the ceramic coating, thereby completing the first deposition pass. Step 4: Repeat steps 2-3 above until the Nth round of ceramic coating deposition is completed, so that the total thickness of the deposited ceramic coating reaches the target value; when a new round of deposition is performed on the surface of the ceramic coating formed by the previous round of deposition, due to the edge effect, the ceramic droplets tend to move away from the crack deposition, so that the crack width of the ceramic coating formed by the new round of deposition is greater than the crack width of the ceramic coating formed by the previous round of deposition, and finally the vertical crack in the ceramic coating presents a V-shape that is wide at the top and narrow at the bottom.

5. The method for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 4, characterized in that: The ceramic powder is yttria-stabilized zirconia YSZ, rare earth tantalate or rare earth zirconate.

6. The method for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 4, characterized in that: The spraying power of the spray gun is between 36-45kW; The power of the laser is between 1.5-6kW, and the instantaneous high temperature provided by the laser is between 600-1000°C; The flow rate of the liquid carbon dioxide beam is between 0.1-1.2 L / min, and the instantaneous low temperature provided by the liquid carbon dioxide beam reduces the surface temperature of the ceramic coating to between 200-300°C.

7. The method for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 4, characterized in that: The N is between 1-15, and the n is between 1-10.

8. The method for preparing a thermal barrier coating containing V-shaped vertical cracks according to claim 4, characterized in that: The thickness of the ceramic coating formed in each round of deposition is between 10 and 150 μm.

9. A thermal barrier coating containing V-shaped vertical cracks, characterized in that: The thermal barrier coating containing V-shaped vertical cracks is obtained by the preparation method described in any one of claims 4 to 8.

10. The thermal barrier coating containing V-shaped vertical cracks according to claim 9, characterized in that: The porosity of the ceramic coating containing the V-shaped vertical crack thermal barrier coating is greater than 8%, and the thermal conductivity is between 0.6-1.2 W / Km.

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