A hierarchical topological defect structure thermal barrier coating and method of manufacture

Abstract

The application discloses a hierarchical topological defect structure thermal barrier coating and a preparation method. Ceramic powder is sprayed by using a wide-speed-range high-energy plasma spraying method, the spraying voltage is 75-130 V, the current is 500-650 A, the argon flow rate is 60-135 slpm, the hydrogen flow rate is 10-20 slpm, a plasma jet is formed, and a hierarchical topological defect structure thermal barrier coating is formed on the surface of a substrate. The wide-speed-range high-energy plasma spraying method is used to improve the temperature and speed of ceramic flying particles by improving the voltage, current, hydrogen and hydrogen flow rate in the spraying parameter, based on the synergistic effect of the superplastic deformation of the ceramic flying particles in the high-energy plasma jet after impacting the substrate and the non-steady-state heat source, and especially the improvement of the flying speed under the action of high argon is beneficial to the sheeting of the thickness of the coating, the micro-nano effect, and the effective improvement of the number of internal hierarchical interfaces of the coating, so that the thermal conductivity is improved.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology of materials, specifically relating to a layered topological defect structure thermal barrier coating and its preparation method. Background Technology

[0002] Thermal barrier coatings are functional coatings that provide thermal protection and heat barrier properties. Applied to the surface of a metal substrate, they reduce the substrate's surface temperature, ensuring normal operation in high-temperature environments. They are widely used on the surfaces of hot-end components in aero-engines, gas turbines, and diesel engines. Plasma spraying is a common method for preparing thermal barrier coatings and belongs to the category of thermal spraying. Its principle involves introducing the coating material into a high-temperature, high-speed plasma jet under the action of a carrier gas. The material interacts physicochemically with electrons and ions in the plasma jet, rapidly heating the ceramic, metal, or other materials to a molten or semi-molten state, forming particles. These particles are accelerated within the jet, forming a high-speed particle stream that impacts the substrate. After lateral flow, spreading, rapid cooling, and solidification, they form flakes. Subsequently, these flakes undergo the same process, overlapping and stacking to form the coating. The coating prepared by plasma spraying is formed by the layering of flakes, creating a multi-level structure.

[0003] Interfacial defects in plasma-sprayed coatings have become a key factor limiting their operational reliability. The traditional design philosophy of plasma-sprayed coatings is to increase porosity to reduce thermal conductivity and improve insulation; for example, the porosity of ordinary plasma-sprayed thermal barrier coatings is typically maintained within the range of 10%-15%. However, increased porosity significantly increases the number of crack nucleation sites, making crack initiation and propagation highly likely under high-temperature operating conditions, leading to coating peeling and failure, and severely weakening reliability. Based on coating reliability analysis, the key is to achieve high thermal insulation and reliable application of the coating while maintaining its density and within a limited coating thickness. Summary of the Invention

[0004] To overcome the problems in the prior art, the present invention aims to provide a layered topological defect structure thermal barrier coating and its preparation method. This method can achieve the integrated preparation of a high-bonding, low-thermal-conductivity thermal barrier coating, and has the characteristics of low cost, simplicity and efficiency, good repeatability, precise and controllable process, and significant theoretical and engineering application value.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a thermal barrier coating with a hierarchical topological defect structure includes the following steps:

[0007] Ceramic powder is sprayed using a wide-velocity high-energy plasma spraying method. The spraying voltage is 75-130V, the current is 500-650A, the argon flow rate is 60-135slpm, and the hydrogen flow rate is 10-20slpm to form a plasma jet, which forms a layered topological defect structure thermal barrier coating on the substrate surface.

[0008] Furthermore, the ceramic powder is a YSZ, ScYSZ, GdYSZ, LC, or LZ ceramic material.

[0009] Furthermore, the ceramic powder has a particle size of 10-60 μm.

[0010] Furthermore, when using a wide-velocity-range high-energy plasma spraying method to form a plasma jet, the spraying distance is 110-120 mm and the powder feed rate is 35-40 g·min. -1 .

[0011] Furthermore, during spraying, the microgrid mask is dynamically moved back and forth in real time.

[0012] Furthermore, the width L of the microgrid mask is 10-20μm, and the distance of one movement of the real-time dynamic reciprocating microgrid mask is 1 / 2L.

[0013] Furthermore, the particle flight speed in the plasma jet is in the subsonic, transonic, and supersonic range.

[0014] Furthermore, the particle flight velocity ranges from 200 to 600 m / s. -1 The temperature range is 3000-3800K.

[0015] The hierarchical topological defect structure thermal barrier coating prepared according to the method described above has a thermal conductivity of 0.85-0.98 W·m. -1 ·K -1 .

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] In this invention, interlayer interface defects are a crucial evaluation indicator affecting the engineering application of plasma-sprayed ceramic coatings. By changing the traditional method of reducing coating thermal conductivity by increasing porosity, this invention proposes a wide-velocity high-energy plasma spraying method. This method increases the temperature velocity of the flying ceramic particles by improving the voltage, current, hydrogen gas, and hydrogen flow rate in the spraying parameters. Based on the synergistic effect of the superplastic deformation of the ceramic particles after impacting the substrate in the high-energy plasma jet and the unsteady heat source, especially the increased flight velocity under high argon gas conditions, this invention facilitates the thinning and micro-nanoization of the spread sheet thickness, thereby effectively increasing the number of interlayer interfaces within the coating. This invention provides a theoretical basis for the structural design of low thermal conductivity, high-reliability thermal barrier coatings and will provide technical support for the surface protection of major national equipment such as aero-engines, possessing significant theoretical and engineering application value.

[0018] Furthermore, based on the defect characteristics formed at the interface between a single ceramic and the substrate in the edge region after impact, a proposal is made to utilize the real-time dynamic reciprocating movement of a microgrid to form hierarchical topological defects. The high heat dissipation effect of cross-scale hierarchical structures, multi-grain boundaries, and high-density substructure defects on phonons is used to replace porous structures to reduce the thermal conductivity and synergistically improve the thermal conductivity of the coating. Attached Figure Description

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a schematic diagram of the preparation apparatus according to an embodiment of the present invention;

[0021] Figure 2 These are TEM images of a single sheet and the sheet / substrate interface morphology obtained in Embodiment 1 of the present invention; wherein, (a) is the central region of the sheet; and (b) is the edge region of the sheet.

[0022] Figure 3 This is a topological image of the coating obtained in Embodiment 1 of the present invention.

[0023] Among them, 1 is the power supply device, 2 is the water-air system, 3 is the spray gun, 4 is the powder feeding device, 5 is the plasma jet, 6 is the ceramic flying particles, 7 is the temperature and speed measuring device, 8 is the micro-grid shield, 9 is the shield, 10 is the substrate, and 11 is the coating sample. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0025] The design of the hierarchical defect structure in this invention involves introducing a microscopic multi-level and defect topological distribution structure into a macroscopically densified coating. This utilizes the interfacial thermal resistance between layers and the heat dissipation effect of phonon dissipation due to the topology of defects at the interfaces to improve the thermal conductivity of the coating to 0.85-0.98 W·m. -1 ·K -1 .

[0026] The present invention discloses a method for preparing a layered topological defect structure thermal barrier coating, comprising the following steps:

[0027] (1) This invention uses ceramic powder materials as raw materials, specifically YSZ, ScYSZ, GdYSZ, LC, or LZ ceramic materials. First, the particle size of the original ceramic powder material is fixed within the range of 10-60 μm. Subsequently, a coating is prepared using a wide-velocity high-energy plasma spraying method, employing a preparation device such as... Figure 1 As shown. First, adjust the spraying voltage and current in the power supply device 1, the argon and hydrogen flow rates in the water-air system 2, and the moving distance of the shield 9 in the microgrid shielding device 8 to deposit a layered topological defect structure thermal barrier coating on the substrate surface. The spraying distance is 110-120 mm, and the powder feeding rate of the powder feeding device 4 is 35-40 g·min. -1 The spraying voltage is 75-130V, the current is 500-650A, the argon flow rate is 60-135 slpm, and the hydrogen flow rate is 10-20 slpm. The spray gun 3 has an internal powder feeding mechanism with a powder feeding nozzle diameter of 1-3mm. By utilizing the inverse relationship between the powder feeding nozzle diameter and the flight speed, the ceramic flying particles 6 can achieve subsonic, transonic, and supersonic flight.

[0028] (2) Regarding the setting of the masking plate 9 during the spraying process, since the edges of the spread formed after a single ceramic particle impacts the substrate are unbonded areas with crack defects, while the middle is a bonded area. Based on the interface TEM results of a single ceramic spread, the width L of the masking plate device 9 is set to 10-20 μm, and the single movement distance of the masking plate 9 is 1 / 2L, to ensure that the edge area of ​​the second droplet is located in the middle area of ​​the previous solidified spread. Subsequently, through the real-time dynamic reciprocating movement of the masking plate 9, the edge areas of the 3rd, 4th, and 5th particles are respectively located in the middle area of ​​the solidified spread, ultimately obtaining a thermal barrier coating with topological distribution characteristics.

[0029] (3) During the spraying process, the flight velocity and surface temperature of the ceramic particles in the plasma jet 5 are monitored using the Spray Watch 2i temperature and velocity measurement system 7. The velocity range of the ceramic particles 6 flying in the plasma jet 5 is 200-600 m / s. -1 Supersonic refers to the flight speed of ceramic particles exceeding 340 m / s, with a surface temperature range of 3000-3800 K.

[0030] (4) Finally, the prepared coating was observed using a scanning electron microscope (SEM), and the layer defect rate of the coating was measured using the image grayscale method. The SEM images were magnified to 500x and had a resolution of 600 dpi. For each sample, 20 scanned images were taken to statistically analyze the content of layer topological defects within the coating sample 11 collected on the surface of the substrate 10. The topological defect content ranged from 3.6% to 8.0%. Laser thermal conductivity testing revealed that the thermal conductivity of the coatings under different embodiments ranged from 0.61 to 0.98 W·m at room temperature. -1 ·K -1 .

[0031] The specific implementation method is as follows:

[0032] Example 1

[0033] Using ceramic powder as raw material, specifically YSZ ceramic material, the initial particle size of the ceramic powder was fixed within the range of 10-60 μm. Subsequently, a coating was prepared using a wide-velocity high-energy plasma spraying method. First, the spraying voltage and current in the power supply device 1, the argon and hydrogen flow rates in the water-gas system 2, and the moving distance of the microgrid masking device 8 were adjusted to deposit a thermal barrier coating on the substrate surface. The spraying distance was 110 mm, and the powder feeding rate of the powder feeding device 4 was 35 g·min. -1 The spraying voltage was 75V, the current was 550A, the argon flow rate was 60 slpm, and the hydrogen flow rate was 10 slpm. The nozzle powder feed orifice diameter was 1mm, and the interface morphology between the spread sheet and the substrate was as follows. Figure 2 As shown in (a) and (b), the edge interface morphology between the ceramic plate and the substrate is a crack defect, while the middle region is a mechanical-physical bond. Based on the interface TEM results of a single ceramic plate, the width L of the micrograting baffle was set to 10 μm, the single movement distance of the baffle was 1 / 2L, and the velocity range of the flying particles in the plasma jet was 200 m·s. -1 The surface temperature range is 3500K. Based on image-based statistical analysis of the coating structure, it was found that… Figure 3 The coating shown has a topological defect content of 8% and a thermal conductivity of 0.98 W·m. -1 ·K -1 .

[0034] Examples 2-20 use the same method as Example 1, but with different parameters, which are detailed in Table 1.

[0035] Table 1. Relationship between wide velocity-range high-energy plasma spraying parameters and defect content in different embodiments.

[0036]

[0037]

[0038] In this invention, by adjusting the process parameters of wide-velocity high-energy plasma spraying, setting the width and reciprocating movement distance of the microgrid mask, and utilizing the heat and mass transfer, high-speed impact, and flattening solidification of ceramic flying particles in the jet to determine the defect formation location, a layered topological defect structure thermal barrier coating is prepared.

[0039] This invention is based on the heat and mass transfer, high-speed particle collision, and solidification theories of ceramic flying particles and plasma jets, to achieve the formation of a layered topological defect structure thermal barrier coating by plasma spraying. Based on the defect characteristics formed at the edge region of the interface between a single ceramic particle and the substrate after impact, the defect distribution of the layered coating structure is quantitatively characterized using image methods. With the aid of an online monitoring system for the flying particles, the fabrication of the layered topological defect structure thermal barrier coating is finally realized.

[0040] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing a thermal barrier coating with a hierarchical topological defect structure, characterized in that, Includes the following steps: Ceramic powder is sprayed using a wide-velocity high-energy plasma spraying method. The spraying voltage is 75-130V, the current is 500-650A, the argon flow rate is 60-135 slpm, and the hydrogen flow rate is 10-20 slpm to form a plasma jet, which forms a layered topological defect structure thermal barrier coating on the substrate surface. During spraying, a micro-grid mask is dynamically reciprocated in real time. The topological defect content is 3.6%-8.0%.

2. The method for preparing a layered topological defect structure thermal barrier coating according to claim 1, characterized in that, The ceramic powder is a YSZ, ScYSZ, GdYSZ, LC, or LZ ceramic material.

3. The method of claim 1, wherein the hierarchical topological defect structure thermal barrier coating is prepared by a method comprising: The ceramic powder has a particle size of 10-60 μm.

4. The method for preparing a layered topological defect structure thermal barrier coating according to claim 1, characterized in that, The ceramic powder is sprayed by a high-energy plasma spraying method with a spraying distance of 110-120 mm and a powder feeding rate of 35-40 g·min -1 .

5. The method for preparing a layered topological defect structure thermal barrier coating according to claim 1, characterized in that, The width L of the microgrid is 10-20μm, and the distance of one movement of the real-time dynamic reciprocating microgrid is 1 / 2L.

6. The method of claim 1, wherein the hierarchical topological defect structure thermal barrier coating is formed by a process comprising: The particle speeds in the plasma jet range from subsonic to transonic and supersonic.

7. The method of claim 6, wherein the method further comprises: Particle flight velocity range is 200-600 m·s -1 Temperature range is 3000-3800 K.

8. The layered topological defect structure thermal barrier coating prepared by the method according to any one of claims 1-7, characterized in that, The thermal conductivity of the coating is 0.85-0.98 W·m. -1 ·K -1 .

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