Thermal barrier coating with embedded structure and preparation method of thermal barrier coating

Abstract

The thermal barrier coating with the embedded structure comprises a base body, a bonding layer and a ceramic embedded layer which are sequentially arranged from bottom to top, the ceramic embedded layer comprises a ceramic middle layer and a ceramic top layer which are sequentially arranged from bottom to top, and a preparation method comprises the steps that firstly, the bonding layer is sprayed, and secondly, the ceramic embedded layer is subjected to deposition treatment; the rare earth element Dy and modified NiAl doped alloy is adopted as the bonding layer, the rare earth aluminate compound is adopted as the ceramic top layer material, and therefore the thermal barrier coating has the high melting point, the high thermal expansion coefficient and the low thermal conductivity, more particles exist in the fixed range, the thermal shock resistance is good, and meanwhile the thermal barrier coating is simple in structure and low in cost. The material has the advantages of good anti-scouring, anti-oxidation and heat-insulating properties, good thermal shock resistance and heat-insulating property, simple preparation process, easy realization, and suitableness for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of thermal barrier coatings, and in particular to a thermal barrier coating with a mosaic structure and a preparation method thereof. Background Art

[0002] Thermal barrier coatings (TBCs) are one of the most advanced high-temperature protective coatings to date. They have good thermal insulation, erosion resistance and high-temperature chemical stability, and have been widely used in many fields such as aerospace, aviation, electric power, chemical industry and metallurgy. Spraying thermal barrier coatings with low thermal conductivity on the surface of parts can effectively reduce the surface temperature of the parts, thereby extending the service life of the parts.

[0003] Traditional thermal barrier coatings mainly include a high-temperature resistant alloy substrate, a metal bonding layer with excellent oxidation resistance and corrosion resistance, and a ceramic layer that provides good thermal insulation for the hot end components, which are arranged in sequence from bottom to top. Among them, the ceramic layer is mostly a single-layer porous ceramic layer. In high-temperature service environments, traditional thermal barrier coatings are formed by plasma spraying, and the single-layer porous ceramic layer structure can obtain a relatively ideal low thermal conductivity to meet the functional requirements of its thermal insulation effect. Although traditional thermal barrier coatings can reduce the operating temperature of the surface of parts and enhance the corrosion resistance of parts, due to the harsh working environment and the material characteristics of the coating system itself, there is often a problem of cracking and failure in the ceramic layer before the interface between the ceramic layer and the bonding layer peels off, which greatly affects the practicality of the thermal barrier coating.

[0004] In view of the above defects, the prior art has made many improvements to thermal barrier coatings and proposed thermal barrier coatings of various structures. Currently, the common structures of TBCs materials include three forms: double-layer structure, multi-layer structure and gradient structure. Among them, the double-layer structure includes a ceramic surface layer and a bonding surface layer. It is widely used due to its simple preparation. However, the thermal expansion coefficients and elastic moduli of the upper and lower layers of different materials are very different, and large thermal stress is easily generated at the interface between the two, which can easily lead to coating failure. The multi-layer structure is composed of: a bonding bottom layer, an intermediate thermal insulation layer, a functional layer and a ceramic surface layer. The functional layer can be an oxygen barrier layer to prevent oxidation, a reflective layer with high reflection of flue gas radiation, or a corrosion layer to improve the corrosion resistance of the coating. However, the preparation process of this structure is The invention relates to a double-layer structure in which a gradient ceramic layer structure with a changing volume fraction of a casting is added between the bonding layer and the ceramic surface layer. This arrangement can effectively alleviate the internal stress generated at the interface in the double-layer structure, thereby significantly improving the bonding strength and thermal shock resistance of the coating. However, the disadvantage is that the gradient ceramic layer composed of a mixture of bonding layer materials and ceramic layer materials is prone to produce an oxide layer, which causes the coating to fail and fall off. In summary, thermal barrier coatings currently generally have many problems such as poor high-temperature phase stability, poor thermal shock resistance and thermal insulation performance, and easy oxidation corrosion. Therefore, the present invention proposes a thermal barrier coating with a mosaic structure and a preparation method thereof to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a thermal barrier coating with a mosaic structure and a preparation method thereof, which has a simple structure, good anti-scouring, anti-oxidation and thermal insulation properties, and also has good thermal shock resistance and thermal insulation properties.

[0006] To achieve the purpose of the present invention, the present invention is implemented through the following technical scheme: a thermal barrier coating with a mosaic structure, including a substrate, a bonding layer and a ceramic mosaic layer, the bonding layer is arranged on the surface of the substrate, the ceramic mosaic layer is arranged on the surface of the bonding layer, the ceramic mosaic layer includes a ceramic middle layer and a ceramic top layer, and the ceramic middle layer is arranged on the surface of the ceramic top layer.

[0007] A further improvement is that the bonding layer is a large particle material with a particle diameter of 10 to 100 μm, the ceramic middle layer is a micron-sized particle material with a particle diameter of 1 to 10 μm, and the ceramic top layer is a nano-sized material with a particle diameter of 1 to 10 nm.

[0008] A further improvement is that the bonding layer is a doped alloy of the rare earth element Dy and modified NiAl.

[0009] A further improvement is that the ceramic middle layer material is YSZ, and the ceramic top layer material is a rare earth aluminate compound.

[0010] A method for preparing a thermal barrier coating having a mosaic structure comprises the following steps:

[0011] Step 1: Surface treatment of the substrate: cleaning, sandblasting and other treatments are performed on the high-temperature alloy substrate to remove surface impurities and improve the bonding strength between the substrate and the coating;

[0012] Step 2: spraying the bonding layer: first premix the pore-forming agent and the bonding layer material to obtain a mixture, and then spray the mixture on the surface of the substrate by plasma spraying to form a bonding layer on the surface of the substrate;

[0013] Step three: ceramic interlayer deposition treatment, using electron beam physical deposition method, depositing ceramic middle layer and ceramic top layer on the surface of bonding layer from bottom to top to complete the preparation of thermal barrier coating.

[0014] Further improvements are: the pore-forming agent in step 2 is one of polyester powder, polystyrene powder and high-density polyethylene powder; the substrate is preheated before spraying and then the bonding layer is sprayed, wherein the preheating temperature is 280-300°C.

[0015] Further improvements are: in the step three, the workpiece with the sprayed bonding layer is preheated before depositing the ceramic intermediate layer, and the preheating temperature is 800-850°C; before depositing the ceramic top layer, the semi-finished coated workpiece after depositing the ceramic intermediate layer is preheated again, and the preheating temperature is 280-300°C.

[0016] The beneficial effects of the present invention are as follows: the present invention adopts a doped alloy of rare earth element Dy and modified NiAl as a bonding layer, and a rare earth aluminate compound as a ceramic top layer material, so that the thermal barrier coating has a high melting point, a high thermal expansion coefficient and a low thermal conductivity, and has more particles within a fixed range, and has better thermal shock resistance. The ceramic interlayer is deposited by electron beam physical vapor deposition, and its structure is denser and the coating surface is smoother;

[0017] At the same time, the thermal barrier coating of the present invention has a simple structure, good anti-scouring, anti-oxidation and heat-insulating properties, good thermal shock resistance and heat-insulating properties, and its preparation process is simple, easy to implement, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a coating structure diagram of Example 1 of the present invention.

[0019] Figure 2 This is a comparison chart of the overall thermal insulation performance of the traditional thermal barrier coating and the thermal barrier coating with double ceramic interlayers in Example 1 of the present invention.

[0020] Figure 3This is a comparison chart of the temperature changes of the substrates of the traditional thermal barrier coating and the dual-ceramic embedded thermal barrier coating under the same conditions in Example 1 of the present invention.

[0021] Figure 4 This is a temperature distribution diagram along the axial direction of a traditional thermal barrier coating and a dual-ceramic embedded thermal barrier coating under the same conditions in Example 1 of the present invention.

[0022] Figure 5 This is a cloud diagram of the equivalent thermal stress distribution of the traditional thermal barrier coating and the dual-ceramic embedded thermal barrier coating in Example 1 of the present invention.

[0023] Figure 6 This is a cloud diagram of the normal stress distribution of the traditional thermal barrier coating and the dual-ceramic embedded thermal barrier coating in Example 1 of the present invention.

[0024] Figure 7 This is a cloud diagram of the thermal deformation of the traditional thermal barrier coating and the dual-ceramic embedded thermal barrier coating in Example 1 of the present invention.

[0025] Figure 8 This is a diagram showing the local equivalent stress changes of the traditional thermal barrier coating and the double ceramic embedded layer thermal barrier coating in Example 1 of the present invention.

[0026] Fig. 9 This is an operational flow chart of the coating preparation method of Example 2 of the present invention.

[0027] Fig.10 This is a schematic diagram of preparing the bonding layer using the plasma spraying method in Example 2 of the present invention.

[0028] Fig.11 Schematic diagram of preparing a double ceramic interlayer by electron beam physical vapor deposition in Example 2 of the present invention.

[0029] Among them: 1. Base layer; 2. Adhesive layer; 3. Ceramic middle layer; 4. Ceramic top layer. DETAILED DESCRIPTION

[0030] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0031] Example 1

[0032] according to Figure 1-Figure 8 As shown, this embodiment provides a thermal barrier coating with a mosaic structure, which can be applied to the piston of an internal combustion engine to improve the piston's anti-scouring, anti-oxidation and heat insulation properties, and improve the strength. The thermal barrier coating includes a base layer 1, a bonding layer 2 and a ceramic mosaic layer. The bonding layer 2 is arranged on the surface of the base layer 1, and a ceramic mosaic layer is arranged on the outer side of the bonding layer 2. The ceramic mosaic layer includes a ceramic middle layer 3 and a ceramic top layer 4, and the ceramic middle layer 3 is provided with a ceramic top layer 4 on its surface.

[0033] In the actual process, the particle size of the bonding layer 2 is controlled by the particle size of the pore-forming agent and the bonding layer material. The pore-forming agent can be selected from polyester powder, polystyrene powder or high-density polyethylene powder. In this embodiment, polyester powder is preferred. The polyester powder and the doped alloy powder of the rare earth element Dy and the modified NiAl are mechanically mixed to prepare the thermal barrier coating, and the bonding layer powder particle size formed after mixing is 10 to 100 μm. This is conducive to the filling of the micro-aggregate particles of the upper layer to fit together, so as to achieve better embedding.

[0034] The bonding layer 2 is a large particle material with a particle diameter of 10 to 100 μm, the ceramic middle layer 3 is a micron-sized particle material with a particle diameter of 1 to 10 μm, and the ceramic top layer 4 is a nano-sized material with a particle diameter of 1 to 10 nm. A total of three levels of particle sizes are selected for the bonding layer 2 and the ceramic interlayer, thereby forming three levels of pores. In the present invention, the bonding layer 2 is a large particle, and the ceramic interlayer disposed on the surface of the bonding layer 2 is a dense particle, and the bonding layer 2, the ceramic middle layer 3 and the ceramic top layer 4 form a thermal barrier ceramic layer coating with a double-layer interlayer structure.

[0035] The ceramic top layer 4 is nano-scale particles, which can make the outer ceramic structure dense, with good phase stability, low thermal conductivity, good sintering resistance and corrosion resistance, small thermal expansion coefficient and low fracture toughness; the ceramic middle layer 3 is micron-scale particles, which can make the inner ceramic and the outer material complementary, and the ceramic has high fracture toughness and large thermal expansion coefficient. The above-mentioned double ceramic layer structure can effectively overcome the thermal mismatch effect between the inner and outer ceramics, and can not only combine the advantages of the inner and outer ceramics, but also overcome their respective disadvantages, which can effectively extend the service life of the coating and significantly increase the use temperature of the coating. The bonding layer 2 is a doped alloy of rare earth element Dy and modified NiAl.

[0036] Adding rare earth element Dy to NiAl eutectic alloy can significantly refine the alloy structure and grains, effectively improve the room temperature and high temperature tensile plasticity and strength of NiAl eutectic alloy, and improve its oxidation resistance. However, excessive rare earth elements reduce the mechanical properties and oxidation resistance of the alloy. Therefore, in this embodiment, the material ratio of the bonding layer 2 is as follows: 0.05 at.% Dy is added to each NiAl eutectic alloy containing 50 at.% Ni and 50 at.% Al, where at.% represents atomic percentage, and the modified NiAl is an existing modified NiAl material, which can be directly obtained.

[0037] The material of the ceramic middle layer 3 is YSZ, and the material of the ceramic top layer 4 is a rare earth aluminate compound.

[0038] YSZ has excellent grains, so that the produced ceramic layer has dense density, few pores, excellent mechanical strength, corrosion resistance, impact toughness, thermal shock resistance and extremely low thermal conductivity. The ceramic top layer material uses rare earth aluminate compounds; the ceramic mosaic layer is combined with the bonding layer 2 to make the coating have a high melting point, high thermal expansion coefficient and low thermal conductivity, and the more particles there are within a fixed range, the better the thermal shock resistance.

[0039] As the instruction manual Figure 2 And the instruction manual Figure 3 As shown, under the same thermal boundary conditions, the double ceramic interlayer (ceramic top layer material is Yb 4 Al 2 O 9 The temperature of the thermal barrier coating substrate (with the ceramic intermediate layer material being 8YSZ) is 630.46°C, and the temperature difference between the top surface of the coating and the surface of the substrate is 270°C, while the temperature of the traditional thermal barrier coating substrate is 712.65°C, which is 82°C lower. In comparison, the thermal barrier coating with a ceramic mosaic layer structure in this embodiment has better thermal insulation performance, and the temperature gradient changes less, which is beneficial to the thermal adaptation stability between the structures of the thermal barrier coating.

[0040] Instructions attached Figure 4 The temperature changes of traditional thermal barrier coating and thermal barrier coating with double ceramic interlayer. It can be seen from the figure that the double ceramic interlayer can show better high-temperature performance and effectively provide thermal protection for the substrate components. The YSZ ceramic intermediate layer can effectively improve the thermal mismatch caused by the thermal expansion coefficient between the rare earth aluminate ceramic top layer and the bonding layer.

[0041] Instructions attached Figure 5 , 6 7 and 8 are the changes in thermal stress and thermal deformation of the traditional thermal barrier coating and the thermal barrier coating with double ceramic interlayer under thermal load conditions. It can be seen from the figure that the changes in the equivalent stress and normal stress of the thermal barrier coating with double ceramic interlayer in this embodiment are smaller than those of the traditional YSZ thermal barrier coating under the same conditions, which shows that the thermal-mechanical performance of the thermal barrier coating with double ceramic interlayer is more stable, the stress gradient between the components is smaller, and the equivalent stress on the surface of the thermal barrier coating with double ceramic interlayer is 1100MPa, which is much smaller than that of the traditional YSZ thermal barrier coating. Its thermal shock resistance is better, which is conducive to improving the service performance of the coating in high temperature environment. In addition, the deformation of the thermal barrier coating with double ceramic interlayer under thermal load conditions is smaller than that of the YSZ thermal barrier coating, which shows that the double ceramic layer material and interlayer structure can effectively improve the heat capacity variation limit between the components of the coating.

[0042] Instructions attached Figure 8The local equivalent stress variation at the interlocking structure of the traditional thermal barrier coating and the double ceramic interlocking layer thermal barrier coating is given intuitively. Under the condition of heat load, the equivalent stress of the double ceramic interlocking layer thermal barrier coating is smaller than that of the YSZ thermal barrier coating at the same interlocking structure, which further proves the advantage of this embodiment.

[0043] Example 2

[0044] according to Figure 9-11 As shown, this embodiment provides a method for preparing a thermal barrier coating with a mosaic structure, comprising the following steps:

[0045] Step 1: Surface treatment of the substrate: cleaning, sandblasting, etc. of the high-temperature alloy substrate 1 to remove surface impurities and improve the bonding strength between the substrate and the coating;

[0046] Step 2: spraying the bonding layer 2: premixing the polyester powder with the bonding layer 2 material to obtain a mixture, and then spraying the mixture on the surface of the substrate by plasma spraying to form a bonding layer on the surface of the substrate;

[0047] Before spraying, the substrate is preheated before the bonding layer 2 is sprayed, wherein the preheating temperature is 300°C. The plasma spraying method is used to spray the mixture so that the surface of the substrate 1 has the properties of wear resistance, corrosion resistance, high temperature oxidation resistance, electrical insulation, heat insulation, radiation protection, friction reduction and sealing; the specification is attached Fig.10 Schematic diagram of preparing bonding layer using plasma spraying method.

[0048] Step 3: ceramic interlayer deposition treatment, using electron beam physical deposition method, sequentially depositing a ceramic middle layer 3 and a ceramic top layer 4 on the surface of the bonding layer 2 to complete the preparation of the thermal barrier coating;

[0049] Before depositing the ceramic intermediate layer 3, the workpiece with the sprayed bonding layer is preheated at a temperature of 800°C; before depositing the ceramic top layer 4, the semi-finished coated workpiece after depositing the ceramic intermediate layer 3 is preheated again at a temperature of 280°C.

[0050] The ceramic interlayer prepared by electron beam physical vapor deposition has a denser structure, and the coating surface formed is composed of many separated columnar crystals perpendicular to the coating surface. Compared with plasma spraying, the coating surface prepared by electron beam physical vapor deposition is smoother. Fig.11 Shown is a schematic diagram of preparing a double ceramic interlayer using electron beam physical vapor deposition.

[0051] The performance test results of the thermal barrier coating in this example are as follows

[0052] When the thermal barrier coating prepared in this embodiment is heated from 25°C to 1400°C, its thermal diffusivity decreases by about 50% compared with the thermal barrier coating prepared from traditional zirconia materials. According to the XRD results, it is found that the thermal conductivity of the prepared thermal barrier coating is in the range of 1.0 to 1.3 W / (m·K), which is much lower than that of traditional thermal barrier coatings. The hardness reaches more than 7 GPa, which can effectively resist corrosion and foreign body impact. In the thermal cycle experiment, it is found that the average thermal cycle life of the thermal barrier coating can reach more than 4000 cycles, which is higher than that of traditional thermal barrier coatings.

[0053] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A thermal barrier coating with a mosaic structure, characterized in that: The invention comprises a base layer (1), an adhesive layer (2) and a ceramic interlocking layer, wherein the surface of the base layer (1) is provided with the adhesive layer (2), the surface of the adhesive layer (2) is provided with a ceramic interlocking layer, the ceramic interlocking layer comprises a ceramic middle layer (3) and a ceramic top layer (4), and the surface of the ceramic middle layer (3) is provided with a ceramic top layer (4).

2. The thermal barrier coating with a mosaic structure according to claim 1, characterized in that: The bonding layer (2) is a large particle material with a particle diameter of 10 to 100 μm, the ceramic middle layer (3) is a micron-level particle material with a particle diameter of 1 to 10 μm, and the ceramic top layer (4) is a nanometer-level material with a particle diameter of 1 to 10 nm.

3. The thermal barrier coating with a mosaic structure according to claim 1, characterized in that: The bonding layer (2) is a doped alloy of the rare earth element Dy and modified NiAl.

4. The thermal barrier coating with a mosaic structure according to claim 1, characterized in that: The material of the ceramic middle layer (3) is YSZ, and the material of the ceramic top layer (4) is a rare earth aluminate compound.

5. A method for preparing a thermal barrier coating having a mosaic structure, characterized in that: The following steps are involved: Step 1: Surface treatment of the substrate: firstly, the high temperature alloy substrate (1) is cleaned and sandblasted to remove surface impurities; Step 2: spraying the bonding layer (2), premixing the pore-forming agent and the bonding layer (2) material to obtain a mixture, and then spraying the mixture on the surface of the substrate by plasma spraying to form a bonding layer on the surface of the substrate; Step three, ceramic interlayer deposition treatment, using electron beam physical deposition method, sequentially depositing a ceramic middle layer (3) and a ceramic top layer (4) on the outside of the bonding layer (2) to complete the preparation of the ceramic coating.

6. The method for preparing a thermal barrier coating with a mosaic structure according to claim 5, characterized in that: The pore-forming agent in step 2 is one of polyester powder, polystyrene powder and high-density polyethylene powder; the substrate is preheated before spraying and then the bonding layer (2) is sprayed, wherein the preheating temperature is 280-300°C.

7. The method for preparing a thermal barrier coating with a mosaic structure according to claim 5, characterized in that: In the step three, the workpiece on which the bonding layer is sprayed is preheated before depositing the ceramic intermediate layer (3), and the preheating temperature is 800-850°C; and the semi-finished coated workpiece after depositing the ceramic intermediate layer (3) is preheated again before depositing the ceramic top layer (4), and the preheating temperature is 280-300°C.

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